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Article

Atmosphere-Transported Emerging and Persistent Contaminants (EPCs) in Rainfall and Throughfall: Insights from a Rural Site in Northern Thailand

by
Theodora H.Y. Lee
1,
Khajornkiat Srinuansom
2,
Shane A. Snyder
1,* and
Alan D. Ziegler
2,3,*
1
Nanyang Environment & Water Research Institute (NEWRI), Nanyang Technological University, 1 Cleantech Loop, CleanTech One, Singapore 637141, Singapore
2
Faculty of Fisheries Technology & Aquatic Resources, Maejo University, Nong Han, San Sai District, Chiang Mai 50290, Thailand
3
Water Resources Research Center, University of Hawaii, Honolulu, HI 96822, USA
*
Authors to whom correspondence should be addressed.
Atmosphere 2023, 14(11), 1603; https://doi.org/10.3390/atmos14111603
Submission received: 2 August 2023 / Revised: 12 September 2023 / Accepted: 23 October 2023 / Published: 26 October 2023
(This article belongs to the Section Air Quality and Human Health)
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Abstract

:
This study investigates the presence and concentrations of emerging and persistent contaminants (EPCs) in rainwater and throughfall water collected from urban areas and agricultural lands in northern Thailand. It focuses on one daily-use compound (caffeine), two industrial compounds (4-nitrophenol and tris(2-butoxyethyl) phosphate (TBEP)), and three agrichemicals (atrazine, fenobucarb, and 2,4-D). Additionally, information is provided regarding the presence of acetaminophen, fexofenadine, diphenhydramine, and gabapentin. Small differences in the chemical composition of the six main contaminants were observed between rainwater and forest throughfall water. However, significant variations were found in the concentration ranges of each EPC. In most cases, throughfall samples exhibited slightly higher concentrations, suggesting a limited contribution from dry deposition compared to rainfall. Limited reliable evidence was found concerning seasonal patterns in EPC concentrations in precipitation (rainfall and throughfall) and surface water samples in remote ponds and reservoirs. The transportation of EPCs via rainwater appears to vary among the compounds tested and is likely to vary from one rainfall event to another, rather than showing a strong and common seasonal response within the monsoon rainfall regime. These findings suggest that the transport of EPCs to remote areas via rainfall does occur for some EPCs. However, the dominance of this process over other transport mechanisms could not be determined with high confidence.

1. Introduction

As the world undergoes increasing industrialization and human development activities expand, the release of contaminants into aquatic environments has become a growing concern in the so-called Anthropocene [1,2]. Emerging contaminants, including contemporary agrochemicals, pharmaceuticals, personal care products, and industrial chemicals, have the potential to negatively impact ecosystems and human health [3,4]. Some of these contaminants are not only of emerging concern, but the potential risk of many has been recognized for decades, and they are therefore of persistent concern. While traditional sources of contamination, such as industrial effluents, wastewater discharges, and storm runoff, have been extensively studied for their role in releasing and transporting contaminants into the environment, the role of rainwater as a potential carrier of many pollutants through the atmosphere remains an area in which additional research is warranted [5,6,7]. Much research has focused on contaminants in rainwater harvesting systems [8,9,10].
Rainwater merits attention due to its potential role in facilitating the transport of anthropogenic-related contaminants to remote areas and typically pristine environments [11,12,13]. For example, rain has the potential to accumulate pollutants from the atmosphere, including flame-retardants, perfluoroalkyl substances, surfactants, personal care products, pharmaceutical compounds, and agrochemicals, thereby becoming a potential carrier of contaminants that can be transported across a range of distances [14,15]. Additionally, various contaminants have the potential to sorb onto aerosol particles that enter the terrestrial environment through both wet and dry deposition processes [11,16]. Understanding the mobilization and transport of emerging and persistent contaminants through rainfall processes is crucial for assessing their potential negative effects on both human and ecological systems [17,18].
In this study, we assessed the concentrations of several emerging and persistent contaminants (EPCs) in rainwater and throughfall water in a rural area in northern Thailand. Throughfall (TF) refers to the precipitation that reaches the ground after passing through the canopy of trees; and this process has not been studied sufficiently in terms of its content of contaminants [19,20]. Throughfall water, therefore, contains chemical signatures from both the rainwater of a specific event and the dry deposition on the canopy since the last event [21,22,23]. While many prior studies have focused on nutrient recycling, acid ions, and potentially toxic elements in throughfall, only limited research has addressed emerging contaminants, such as urban- and road-related contaminants and microplastics [24,25]; this is also discussed in the Discussion section.
In preliminary work, we found that many contaminants in the study area were largely associated with urban pollution signatures, particularly in surface waters. However, some remote sites also showed the presence of various pharmaceuticals, industrial contaminants, and agrochemicals, prompting a closer examination of rainfall (RF) as a potential source of these emerging contaminants (ECs). The increasing presence of anthropogenic activities in urban and intensively farmed agricultural areas also raises concerns about potential contamination and its subsequent impact on water resource quality in surrounding areas that should be relatively pristine. By investigating the concentrations of various contaminants in rainfall, we seek to gain insights into the role of the atmospheric transport of various contaminants from source locations to other areas. Herein, we refer to them as emerging and persistent contaminants (EPCs), as we include a few that have been of concern for decades (e.g., atrazine, 2,4-D, 4-nitrophenol).
Specifically, we compared the concentrations of EPCs in rainwater and throughfall water with those found in surface water bodies in remote locations to assess the potential role of rainwater as a transmitter of pollution from source locations, including agricultural areas and the urban environment. Our research approach revolves around the main hypothesis that if rainfall is a significant contributor to the EPC signatures in water features that should normally be uncontaminated, their general patterns should exhibit similar seasonal variations in concentration changes. Otherwise, other types of transport processes that are not readily observable may play a crucial role in these systems where direct input and surface runoff during rainfall events are not the primary mechanisms of mobilization (taking EPC degradation and transformation into account). Other key hypotheses include the following: (1) the EPC chemistry of rainwater and throughfall will differ due to the influence of dry deposition in the latter; (2) trends in EPC patterns will be similar among all remote sites, assuming the transport mechanism is the same (i.e., through the atmosphere); (3) EPC presence and concentrations will reflect seasonality within the monsoon climate system of the study area.

2. Materials and Methods

2.1. Study Area

Chiang Mai is one of the most populous provinces in Thailand. The city of Chiang Mai and the surrounding boroughs form the primary population center within the Ping River Catchment [26,27]. The recent growth of the once-rural peripheral districts around the city has led to the development of a large peri-urban landscape, consisting of agricultural lands mixed with residential developments and a variety of commercial, manufacturing, and industrial complexes of various sizes.
The area experiences three distinct seasons: (1) the hot and dry season extends from March through May; (2) a wet and rainy season extends to late October; and (3) a lengthy dry season stretches from November to March [28,29]. In this paper, we draw attention to the transition from drier months (months 1 to 5) and wetter months (month 6 onward). Some work has shown variability in the presence of various pollutants associated with seasonality in Thailand [30,31,32]. Additional study area details on related biophysical phenomena (pollutants, hydrology, and rainfall) are provided elsewhere [26,30,31,32,33,34,35].
The general location of sampling for rainfall (RF) and throughfall (TF) was approximately 20 km NE of the city center (Figure 1). Agriculture, urban, and light industrial activities exist in the peri-urban settings between the collection site and the greater Chiang Mai urban area, but intensive farming largely occurs in areas further to the east, northwest, and south. Relevant to our study is the fact that within the vicinity of the collection areas, there are no intensive agriculture and industrial contamination sources for which surface runoff would be a major pollution transport mechanism to the ponds and reservoirs studied (discussed in more detail below).

2.2. Sampling

We collected a total of 22 paired samples of rainfall and throughfall between August 2021 and September 2022. The samples were collected in identical alcohol-rinsed tubs placed in an open area for rainfall collection or under the canopy of a lowland dipterocarp forest (e.g., Dipterocarpus sp. and Shorea sp.) for throughfall collection. Additionally, we obtained two additional rainfall samples and two samples of dry deposition (DD) events to provide additional descriptive information, as shown in Figure 1.
We collected water samples from nearby ponds (n = 2; P04, P30), reservoirs (n = 4; R04, R25, R59, R60), and a stream (n = 1; S42). The pond and reservoir sites were largely free from surface water contamination. However, the stream drains a larger area with mixed land use, where more contamination inputs would be expected. Most of the sites were located within a 3 km radius of the rainfall and throughfall collection site, except for two reservoirs situated approximately 15 km away in the most remote areas (Figure 1). The samples from most sites were collected once a month from June 2021 to July 2022, totaling 13 samples; the samples at reservoir sites R59 and R60 were occasionally compromised and discharged, resulting in few samples for consideration (8 and 9).
Rainfall and TF water samples were collected in alcohol-rinsed Nalgene vessels that were positioned in their sampling locations prior to rainfall events. Due to the unpredictability of the timing and duration of rainfall events, the sampling time for which the vessels were situated varied. Water from overnight events was collected the following morning, while water from some daily events was collected after water had stopped dripping from the forest canopy. The collected samples were stored in 125 mL Nalgene bottles at 4 °C for a limited period (a few days to a week) until they were sent to the laboratory in Singapore for analysis. Prior to collection, all samples were spiked with sodium azide (1 g/L) to inhibit microbial activity.

2.3. Analyses

2.3.1. Compounds Considered

Our analysis encompasses a total of 26 EPCs, including three industrial compounds (4-nitrophenol, TBEP, and tolyltriazole), four agrochemicals (2,4-D, atrazine, fenobucarb, and prohydrojasmon), three everyday compounds (acesulfame, caffeine, and sucralose), seven non-prescription pharmaceuticals (diclofenac, fexofenadine, gemfibrozil, ibuprofen, naproxen, acetaminophen, and diphenhydramine), and ten prescribed pharmaceuticals (atenolol, carbamazepine, estrone, fluoxetine, gabapentin, iomeprol, metformin, metoprolol, sulfamethoxazole, and valsartan). These EPCs were selected because they were among the most prevalent in surface water within the study area during a preliminary reconnaissance study. We pay particular attention to the six that are commonly found at the site, namely 4-nitrophenol, caffeine, TBEP, fenobucarb, atrazine, and 2,4-D.
In brief, caffeine, a natural stimulant found in coffee, tea, and various beverages, can enter water bodies through wastewater and can adversely affect aquatic organisms. 4-nitrophenol is a chemical compound used in various industrial applications and can be toxic to aquatic life, potentially persisting in the environment if not managed properly. TBEP, a plasticizer used in some industrial processes, raises environmental concerns due to its potential leaching into soil and water, with adverse effects on aquatic organisms. Fen-obucarb is an agricultural pesticide that can be transported in runoff, contaminating water bodies, and potentially impacting non-target species and ecosystems. Atrazine and 2,4-D are widely used “old-guard” herbicides in agriculture, capable of leaching into groundwater, contaminating surface water, and potentially harming aquatic ecosystems (see Discussion session for more details). These EPCs are discussed in greater detail in the discussion section. The other EPCs are described in Supplement Item S1.

2.3.2. Analytical Procedures

For the analysis, we used online solid-phase extraction (OSPE) coupled with high-resolution liquid chromatography–triple quadrupole mass spectrometry (LC-MS/MS). Raw water samples were filtered using 0.2-μm PES syringe filters, and each 5 mL filtered sample was spiked with 100 μL of a 10 μg/l internal standard (ISTD) stock solution. Chromatographic separation was achieved using InfinityLab Poroshell 120 superficially porous columns (EPC-C18; 3.0100 mm; 2.7 μm) and a compatible guard column (EPC-C18; 2.15 mm; 1.9 μm). Mass spectrometry was performed using an Agilent 6495C triple quadrupole tandem mass spectrometer with a dual Agilent Jet Stream Electrospray Ionization (AJS-ESI) source.
The limit of detection (LOD) for each targeted EPC and four quality control samples, at a concentration of 100 ng/L distributed across the samples, was recorded each month to ensure method and instrumental consistency (see quality assurance/quality control (QA/QC) details in Supplement Item S1). The LOD was defined as a signal-to-noise ratio of at least 10. Concentrations < LOD are also referred to as below the detection limit in the results. Samples with low internal standard (ISTD) counts were retested to account for inaccurate additions of the standard during sample preparation rather than presuming it was due to matrix effects. All data were preprocessed using Agilent MassHunter Quantitative Analysis and post-processed using R v4.2.2.

2.3.3. Quality Assurance/Quality Control (QA/QC)

The QA/QC data for the EPCs considered in this paper are listed in Supplement Item S2. The data indicate reasonable consistency in the reproduction of lab standards (100 ng/L) and field blanks (0 ng/L). Further, the field replicates (3 water types; 3 replicates; variable concentrations) were also generally consistent. Not shown are several compounds that were rejected owing to poor QA/QC performance. Nevertheless, we keep detection variability in mind in the discussing of the EPCs that are the focus of this analysis.

3. Results

3.1. Throughfall Relationship with Selected Water Quality Parameters

Rainfall depths for the 22 events ranged from 2 to 75 mm; the range for throughfall was 0 to 73 mm (Figure 2; Supplement Item S3). The throughfall component was an estimated 0.80 ± 0.30, like that reported elsewhere in Thailand for similar forests [20,34].
The pH of the throughfall was slightly more acidic than the rainfall (median ± median absolute deviation (MAD)): 6.15 versus 6.83 (Table 1). The specific electrical conductivity (SEC) of throughfall was more than double that of rainfall: 18.5 versus 8.2 µS/cm (Table 1). Throughfall also contained much more dissolved organic carbon (DOC) and rainfall (22.07 versus 5.04 mg/L); and total nitrogen (TN) was slightly higher (0.75 versus 0.48 mg/L). These data suggest noticeable differences in the chemistry of the two water types.

3.2. EPC Concentrations

3.2.1. Rainfall and Throughfall

Detectable concentrations were found in the following EPCs (listed in order of presence; Table 1): 4-nitrophenol (n = 22 RF; 22 TF), caffeine (18; 22), TBEP (14; 15), fenobucarb (10; 13), atrazine (10; 10), 2,4-D (3; 7), acetaminophen (5; 1), fexofenadine (0; 3), diphenhydramine (2; 0), and gabapentin (0; 1). The data for the six most prevalent are shown in Figure 3. The highest concentrations were recorded for 4-nitrophenol, with medians of 1431 and 810 ng/L in rainfall and throughfall, respectively (maximums = 6870 and 7127 ng/L; Table 1). Caffeine also exhibited relatively high concentrations in both rainfall (median = 133 ng/L; maximum = 908 ng/L; 82% presence) and throughfall (141; 1176 ng/L; 100%) across the year.
Detectable concentrations of TBEP (RF and TF) were also prevalent, with detection frequencies ≥ 50%; the maximum concentration was 292 ng/L. Maximum concentrations of the pesticides fenobucarb (342 ng/L), atrazine (95 ng/L), and 2,4-D (74 ng/L) were slightly lower, and prevalent in only 14% to 46% of the samples. Of the three pesticides, median concentrations of atrazine and 2,4-D were below the detection limit (bdl) in both rainfall and throughfall. Median concentrations of fenobucarb were higher (between 13 and 30 ng/L).
Correlations between concentrations in rainfall and throughfall were high (≥0.75) for the most prevalent EPCs (Rho in Table 1). Despite being present in all rainfall and throughfall samples, the median concentrations of 4-nitrophenol were higher in the rainfall samples. Nineteen of the twenty-two paired samples had higher 4-nitrophenol concentrations in rainfall than throughfall, a trend that was opposite to the other five commonly found compounds (Figure 4). This association is statistically significant, yet not practically significant, given the overlapping range of the two precipitation types. For the other EPCs, there was no statistical difference between the concentrations of rainfall and throughfall (Wilcoxon rank-order test). Furthermore, only the concentration of 4-nitrophenol in rainfall was correlated with rainfall depth (linear regression R2 = 0.62; 0.20 for throughfall).
Regarding the other EPCs that were present, the maximum concentrations were 2059 ng/L for gabapentin, 2055 ng/L for acetaminophen, 208 ng/L for diphenhydramine; and 103 ng/L for fexofenadine. However, these four EPCs were not prevalent. The other sixteen EPCS considered were not found (listed above and in Supplement Item S1).
In general, the data do not support the notion that EPC throughfall waters were substantially contaminated compared to rainwater, providing little support for the theory of dust deposition between storms as a significant pathway for EPC transport into the forest canopy (Table 2; Figure 5). The concentrations of EPCs collected in the four dry deposition samples were not greater than those collected in rainfall or throughfall. Only four EPCs had medians above detection limit (See data in Supplement Item S2): caffeine (220 ng/L [median]; 246 ng/L [maximum]; 100% [detection frequency]); metformin (130 ng/L; 517 ng/L; 50%); 4-nitrophenol (70 ng/L; 115 ng/L; 100%); and TBEP (55 ng/L; 76 ng/L; 50%). Acesulfame and metformin were detectable in one and two dry deposition samples, respectively.

3.2.2. Surface Waters

Concentrations of EPCs in the surface water bodies were generally low to moderate based on medians (Table 2). Only caffeine had at least one sample with concentrations above 1000 ng/L in one reservoir and one pond. Generally, EPC concentrations tended to be lower than those in rainfall or throughfall (RF-TF) samples (Figure 5). An exception occurred at the stream site (S42), where relatively high concentrations of 2,4-D, atrazine, caffeine, and fenobucarb were found at different times of the year (Figure 5).
Atrazine concentrations were often elevated in the dry season (months 1–4; Figure 5), suggesting a potential dilution effect. Fenobucarb and 2,4-D showed some elevated levels in the rainy season (months 8–10), likely associated with surface runoff from agricultural areas, a process that was considered during the experiment design. Caffeine and TBEP in the surface waters exhibited concentration profiles similar to those in rainfall and throughfall, providing some support for rainfall as a potential transportation pathway (Figure 5). The effect of seasonality on EPC concentrations was generally not obvious.

4. Discussion

4.1. Comparison with Other Studies Worldwide

The ranges of values we report for the six EPCs of focus fall within the ranges of those reported elsewhere worldwide (Supplement Item S4). When considering all types of precipitation, the 4-nitrophenol values (60–7100 ng/L) we find in precipitation and throughfall water are intermediate within the wide range reported in the literature worldwide, which conservatively spans from 8 to 71,000 ng/L (Supplement Item S4). Values exceeding 10,000 ng/L have been reported in Germany [36,37,38,39] and the UK [40]. The lowest values (8–11 ng/L) were reported in rains in Moscow [41] and Melpitz, Germany (500 ng/L [40]). Maximum values in the UK (1900 ng/L [40]), USA (≤5000 ng/L [42]), France (5700–6100 ng/L [38,43]), were more in line with the higher values we found in Thailand. Extreme values of up to 29,000,000 ng/L have also been reported in Italy [44].
Nitrophenols, in general, originate from direct emissions resulting from combustion processes, the hydrolysis of some pesticides, and secondary formation in the atmosphere [45,46]. In the past, there was concern about their potential role in damaging forest vegetation [47]. Additionally, as well as being hazardous to humans and the environment [42], 4-nitrophenol is a potentially useful tracer of EC transport from source to remote areas. For instance, in Bavaria, Germany, 4-nitrophenol was found to be the highest of all phenols measured, with maximum values of about 12,000 ng/L [39]. One key emission source in Germany was the lubricating oil of a gas turbine, located one kilometer from the sampling area. The amount of the compound (in air and water) found in rural sites, anywhere, is likely of photochemical origin, whereas the amount found in urban sites is the largely sum of that emitted by traffic and that of photochemical origin. The low air–water partitioning coefficient of nitrophenols promotes their enrichment in rain and fog water [48].
Caffeine is food-associated compound in water resources that has garnered growing attention worldwide in several locations [49], including (Supplement Item S4) Australia [50], China [51], Singapore [52,53], South Africa [54,55], and the USA [56,57]. Due to its ubiquity, caffeine serves as a potentially good indicator to track chemicals in the environment [54], even in very remote locations such as Antarctica [58]. The caffeine concentrations we measured in rainfall and throughfall water [bdl-1176 ng/L] are at the lower end of the range observed in various types of rainfall-affected waters worldwide (Supplement Item S4). The maximum concentration exceeds those in very clean sites in China and Antarctica [51,58] but falls below levels observed in a reservoir in Singapore (26–645 ng/L; [52]). Our values are slightly lower than those found in surface water runoff and stream water in sites in the USA (369–1710 ng/L [56,57]) and Singapore (57–2980 ng/L [52]). Concentrations exceeding about 9000 ng/L have been reported in rainwater harvesting systems in South Africa [54,55] and runoff in Singapore [53]. The concentrations we find in rainfall/throughfall in Thailand therefore appear plausible.
TBEP, an organophosphate ester, is commonly used as a flame retardant and plasticizer in various products [59]. This industrial chemical has the potential to be transported in the atmosphere over long distances, including through rain, as it has been detected in aerosols, precipitation, and surface water runoff (Supplement Item S4). The range of concentrations we measured (bdl-292 ng/L) is intermediate compared to the low levels (<120 ng/L) reported in China [60], Germany [61,62], Sweden [63], and Italy [64], and the higher values (>1000 ng/L) reported in the USA [56] and Germany [61,65,66]. Fries and Püttmann [65,66] suggest that values of ~390 ng/L are indicative of diffuse input, and the presence in precipitation-associated waters likely indicates the ongoing use of flame retardants.
The presence of pesticides in precipitation is not surprising given Thailand’s continued import of many pesticides, including 2,4-D, atrazine, and fenobucarb [67]. Most prior work reporting on Fenobucarb in precipitation was conducted in Japan, where the compound was often not detected, but maximum concentrations ranged from 140 to 580 ng/L [68,69], and even exceeded 8000 ng/L [70]. Our maximum value of 342 ng/L falls within the range of values reported elsewhere (see [71,72]). In Utsunomiya, Japan, high values were often associated with small rainfall depths [70]. The range of values we found is plausible based on the limited evidence elsewhere.
Atrazine was the most studied compound among the three pesticide EPCs we measured (Supplement Item S4). The concentration values we determined (bdl-95 ng/L) are consistent with a range of values (bdl to 200 ng/L) reported in the USA [73,74,75] and Europe [76,77,78,79,80,81,82], with maximum values ranging from 430 to 903 ng/L also reported in Europe [83,84,85,86]. These values are at least an order of magnitude lower than those often observed in agriculture areas worldwide decades ago (>1000 ng/L; [87,88,89,90,91]), including extremely high values (>20,000 ng/L) in the USA [92,93,94]. Recently, values ranging from 100 to 26,900 ng/L were reported in Argentina [95]. Values up to 1300 ng/L were reported in France and Belgium after the turn of the century [86,96]. One study in Italy [90] considered pesticides in both rainfall and throughfall in forests, with values ranging from bdl to 1990 ng/L. To our knowledge, our study is the only one that has investigated atrazine and the other EPCs reported in throughfall water. The generally low values of atrazine we find in Thailand rainfall and throughfall are plausible compared with the data reported worldwide, particularly in areas where pesticide use has been intense in the past [97,98,99,100].
The widely used herbicide 2,4-D has raised concerns over the years due to its presence in rainwater, potentially leading to environmental contamination and health risks by impacting ecosystems and water quality [101,102,103,104,105,106]. The range of values we determined [bdl-74 ng/L] is at the lower end of the range reported worldwide (Supplement Item S4), slightly higher than the maximum concentrations of 31–48 ng/L found in Finland, Sweden, and Switzerland [82,85,101], yet lower than concentrations found in the USA, Canada, and Germany, which ranged from 282 to 527 ng/L [75,102,103]. Concentrations that were two-to-three orders of magnitude higher than what we found were reported a few decades ago [104,105,106]. Thus, the maximum values we found appear to be plausible, but not high.
Regarding the other four EPCs detected, the concentrations of acetaminophen appear to be the most plausible (bdl-2054 ng/L), falling within the range of concentrations reported for Antarctica (bdl-39 ng/L [58]), rainwater tanks in South Africa [54], Svihov Reservoir in the Czech Republic (bdl-1800 ng/L [107]), and higher values also found in South Africa (7420–9530 ng/L [55]) and waste-associated effluent in Latin America (17–66,000 ng/L [108]). In contrast, based on limited data, our gabapentin maximum (2059 ng/L) is high compared to raw water in the Czech Republic (bdl-157 ng/L [107]). The maximum concentrations of diphenhydramine (208 ng/L) are also higher than effluent reported for Latin America (1–99 ng/L [108]). The limited data available for fexofenadine had maximum concentrations two orders of magnitude (640–147,870 ng/L [108]) higher than our concentration of 2054 ng/L. The uncertainty in the validity of these latter three EPCs is trivial, as only 1–3 rainfall/throughfall samples had detectable concentrations.

4.2. Trends at the Thailand Site

A central observation from our study is the discrepancy between the presence and trends of EPCs in surface waters compared with rainfall (Figure 5). While EPCs were generally found to be prevalent, if not more so, in rainfall samples compared with surface waters at remote sites. An exception was atrazine, which exhibited a higher prevalence in some ponds and streams located in proximity to anthropogenic activities. Fenobucarb, when present, tended to be found in similar locations. Thus, the proximity to sources is likely a more important variable for the presence of these agrochemicals than transport in the atmosphere from distant sources. In comparison, caffeine emerged as a consistently ubiquitous compound in both precipitation and surface waters. Pesticides fenobucarb and 2,4-D were less prevalent than atrazine. The two industrial compounds (4-nitrophenol and TBEP) tended to occur less frequently in surface water samples than rainfall.
The observed variations in prevalence among classes and individual EPCs likely reflect differences in sources relative to the measurement sites, as well as their transformation and fate once entering the systems [109,110,111]. This divergence can be attributed to the fact that the surface water systems in our study areas are not entirely closed features dependent solely on rainwater inputs, as would be the case with very pristine volcanic-associated lakes. The lower concentrations of EPCs in surface waters can also be attributed to a range of factors, including the processes of mixing, removal during transport over distances (such as runoff and infiltration), and degradation over time. Our measurements were not conducted during or immediately after rainfall events; thus, a “perfect” association with rainfall should not be expected (discussed more below). The differences underscore the multifaceted nature of EPC transport and distribution in ecosystems that are in remote areas, yet likely impacted by somewhat distant anthropogenic activities.
The data did not reveal evidence of seasonality associated with the presence of EPCs, such as the flushing of contaminants with the onset of the rainy season or dilution during prolonged wet periods [112,113]. Similarly, no washout effect, which refers to the dilution of EPC presence in larger rainfall events, was observed. However, we acknowledge that limited data may have constrained our ability to detect some of these types of patterns.
Regarding transport, the patterns depicted in Figure 6 do not align with the hypothesis that the listed pairs of compounds are transported in a similar manner. Each pair of compounds belongs to distinct categories, encompassing industrial (4-nitrophenol, TBEP) and agricultural (fenobucarb, atrazine) compounds. If these compounds were primarily transported through a common medium like rainfall or surface runoff, we would anticipate less variability within each pair, factoring in considerations like degradation and transformation. Put more simply, we would not expect a greater association between levels of concentration unless application rates varied, for example, in the case of the two pesticides. Although the groupings for the agricultural pair exhibited a relatively tighter pattern than the industrial pair, the presence of numerous values below the detection limit contributes to high variability.

4.3. Uncertainties for 4-nitrophenol and Experimental Limitations

Some degree of uncertainty exists in our analysis of EPCs in rain and throughfall water, stemming from several issues that warrant careful consideration. First among these is the potential for sample contamination due to the presence of the field team, particularly concerning caffeine and some pharmaceuticals (e.g., acetaminophen). However, the concentrations recorded in the field bank do not exhibit persistent and elevated concentrations that would indicate contamination (Supplement Item S2). Furthermore, the team consistently us disposable rubber gloves for all sample handling procedures, a precautionary measure to minimize the risk of contamination. Regarding pesticides, the rainfall and throughfall monitoring site was chosen because no pesticides were used at the location, and no intensive agriculture was located nearby. In sum, external contamination is believed to be nonexistent, or at least very low.
Another issue of concern is the presence of higher concentrations of 4-nitrophenol in rainfall samples compared with throughfall samples. While we used identical plastic sampling vessels for both types of samples, their placement was not entirely random. The frequency of encountering high concentrations of 4-nitrophenol in the rainfall vessel may be linked to a potential defect in the material composition of that specific vessel, but this type of contamination was not supported by the two dry deposition samples showing higher concentrations associated with the throughfall vessel. Here, we entertain the notion that 4-nitrophenol underwent a transformation when passing through the canopy, but more work is needed to investigate the validity of this hypothesis, as phenols in general tend to be resilient to biodegradation [114].
It is also important to acknowledge that the observed concentrations of EPCs might be influenced by the time lapse between sample placement and the actual rainfall event. Although our protocol aimed to place samples daily in the morning to anticipate afternoon storms, strict adherence to this routine was not always feasible due to the remote location of the site. Additionally, some rainfall events might have comprised a mixture of smaller events occurring throughout the day or night. Nighttime events, in particular, could accumulate water over a 12 h period, whereas most daytime events were collected shortly after the rainfall storm. Furthermore, despite our efforts to minimize errors through expedient sample processing, we cannot rule out the possibility that differences in processing times could have impacted the results. This is a common challenge in environmental sampling campaigns conducted in remote areas where immediate sample analysis is hindered by shipping delays and instrument downtimes.

5. Conclusions

This study delved into the concentrations of emerging and persistent contaminants in rainwater and throughfall water to unravel the extent to which EPCs are transmitted from urban and intensively farmed agricultural areas to remote regions through the atmosphere in precipitation. By comparing EPC concentrations in rainfall and throughfall with those in nearby surface water bodies within remote and relatively unpolluted regions, we aimed to gauge the role of rainwater in redistributing pollution. The findings illuminated subtle differences in EPC concentrations among different compounds in rainwater and throughfall water. In general, throughfall samples exhibited a slightly higher presence of EPCs, although not necessarily higher concentrations, except for 4-nitrophenol. Dry deposition, therefore, likely had a limited impact on elevating throughfall concentrations of most EPCs compared to rainfall. Surface water samples generally displayed lower EPC concentrations, except for agrochemicals atrazine, fenobucarb, and 2,4-D, typically in a stream possibly influenced by surface runoff from fields.
Furthermore, our investigation did not uncover a robust seasonal response in EPC concentrations in rainfall, throughfall, or surface water. This lack of a seasonal pattern in precipitation and remote water bodies, such as ponds and reservoirs, implies that rainfall may not serve as the primary transport mechanism for many EPCs to reach remote sites in the study area (e.g., pesticides observed). Rainfall does, however, likely contribute to the presence of other types of industrial and daily-use EPCs observed in the remote water bodies. Nevertheless, limited data hinder a complete understanding of EPC transitions and fate upon entering the environment, potentially concealing the initial transport process. Additionally, the timing of this transport may involve more intricate dynamics than a straightforward increase or decrease tied to annual wetness patterns, such as rainy versus dry seasons.
Despite certain quality assurance and quality control limitations, our general conclusion is that rain likely carries some types of EPCs from distant sources to remote areas, thereby influencing the water characteristics in certain types of water bodies that are primarily influenced by pollutants in surface runoff or direct dumping. Future research could focus on individual events rather than relying solely on a monthly sampling approach, while also considering the impact of wind phenomena. Furthermore, it is essential to consider other EPCs of immediate concern in the study area once they are identified. The intricate interplay of factors affecting EPC distribution underscores the imperative for continued research aimed at gaining a deeper understanding of the dynamics of emerging and persistent contaminants in pristine ecosystems. This knowledge is pivotal for making informed decisions regarding the conservation and management of these remote and often sensitive environments.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/atmos14111603/s1: Supplement Item S1 (general description of the other or non-prevalent EPCs considered in the paper), Supplement Item S2 (QA/QC information), Supplement Item S3 (raw data), Supplement Item S4 (summary of concentrations for EPCs reported for precipitation and other relevant water resources worldwide).

Author Contributions

Formal analysis, T.H.Y.L. and A.D.Z.; Funding acquisition, S.A.S.; Field investigation, K.S. and A.D.Z.; Methodology, T.H.Y.L.; Sample preparation, K.S. and A.D.Z.; Laboratory analysis, T.H.Y.L.; Writing—original draft, T.H.Y.L. and A.D.Z.; Writing—review & editing, T.H.Y.L., S.A.S. and A.D.Z.; Writing—final version, T.H.Y.L. and A.D.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This work is funded by National Research Foundation, Singapore, and PUB, Singapore’s National Water Agency under its RIE2025 Urban Solutions and Sustainability (USS) (Water) Centre of Excellence (CoE) programme, awarded to Nanyang Environmental & Water Research Institute (NEWRI), Nanyang Technological University, Singapore (NTU), and also supported by the Lien Environmental Fellowship Programme. This research is also supported by the Interdisciplinary Graduate Program (IGP), NTU, as well as the Faculty of Fisheries Technology & Aquatic Resources, Mae Jo University, Chiang Mai, Thailand. Authors acknowledge and are thankful to Agilent Technologies for support through a research collaboration agreement (RCA-2019-0349). We would also like the acknowledge the contributions of Ms Kalaya Kantawong, Goh Chun Ting and Charmaine Tay who have assisted in field data collection and preparation.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

All data are available in the Supplementary Materials.

Conflicts of Interest

There are no conflict of interest to report.

References

  1. Burri, N.M.; Weatherl, R.; Moeck, C.; Schirmer, M. A review of threats to groundwater quality in the anthropocene. Sci. Total Environ. 2019, 684, 136–154. [Google Scholar] [CrossRef] [PubMed]
  2. Kumar, M.; Snow, D.D.; Honda, R. (Eds.) Emerging Issues in the Water Environment During Anthropocene: A South East Asian Perspective; Springer: Berlin/Heidelberg, Germany, 2020; pp. 1–365. [Google Scholar]
  3. Noguera-Oviedo, K.; Aga, D.S. Lessons learned from more than two decades of research on emerging contaminants in the environment. J. Hazard. Mater. 2016, 316, 242–251. [Google Scholar] [CrossRef] [PubMed]
  4. Sauvé, S.; Desrosiers, M. A review of what is an emerging contaminant. Chem. Cent. J. 2014, 8, 15. [Google Scholar] [CrossRef] [PubMed]
  5. Gavrilescu, M.; Demnerová, K.; Aamand, J.; Agathos, S.; Fava, F. Emerging pollutants in the environment: Present and future challenges in biomonitoring, ecological risks and bioremediation. New Biotechnol. 2015, 32, 147–156. [Google Scholar] [CrossRef]
  6. Prieto-Rodriguez, L.; Miralles-Cuevas, S.; Oller, I.; Agüera, A.; Puma, G.L.; Malato, S. Treatment of emerging contaminants in wastewater treatment plants (WWTP) effluents by solar photocatalysis using low TiO2 concentrations. J. Hazard. Mater. 2012, 211, 131–137. [Google Scholar] [CrossRef]
  7. Naidu, R.; Espana, V.A.A.; Liu, Y.; Jit, J. Emerging contaminants in the environment: Risk-based analysis for better management. Chemosphere 2016, 154, 350–357. [Google Scholar] [CrossRef]
  8. Gwenzi, W.; Dunjana, N.; Pisa, C.; Tauro, T.; Nyamadzawo, G. Water quality and public health risks associated with roof rainwater harvesting systems for potable supply: Review and perspectives. Sustain. Water Qual. Ecol. 2015, 6, 107–118. [Google Scholar] [CrossRef]
  9. Sánchez, A.; Cohim, E.; Kalid, R. A review on physicochemical and microbiological contamination of roof-harvested rainwater in urban areas. Sustain. Water Qual. Ecol. 2015, 6, 119–137. [Google Scholar] [CrossRef]
  10. Deng, Y. Pollution in rainwater harvesting: A challenge for sustainability and resilience of urban agriculture. J. Hazard. Mater. Lett. 2021, 2, 100037. [Google Scholar] [CrossRef]
  11. Barroso, P.J.; Santos, J.L.; Martín, J.; Aparicio, I.; Alonso, E. Emerging contaminants in the atmosphere: Analysis, occurrence and future challenges. Crit. Rev. Environ. Sci. Technol. 2019, 49, 104–171. [Google Scholar] [CrossRef]
  12. Kim, S.-K.; Kannan, K. Perfluorinated acids in air, rain, Snow, surface runoff, and lakes: Relative importance of pathways to contamination of urban lakes. Environ. Sci. Technol. 2007, 41, 8328–8334. [Google Scholar] [CrossRef]
  13. Alfonso, M.B.; Arias, A.H.; Ronda, A.C.; Piccolo, M.C. Continental microplastics: Presence, features, and environmental transport pathways. Sci. Total Environ. 2021, 799, 149447. [Google Scholar] [CrossRef]
  14. Abbasi, T.; Abbasi, S.A. Sources of pollution in rooftop rainwater harvesting systems and their control. Crit. Rev. Environ. Sci. Technol. 2011, 41, 2097–2167. [Google Scholar] [CrossRef]
  15. Pamuru, S.T.; Forgione, E.; Croft, K.; Kjellerup, B.V.; Davis, A.P. Chemical characterization of urban stormwater: Traditional and emerging contaminants. Sci. Total Environ. 2021, 813, 151887. [Google Scholar] [CrossRef]
  16. Potter, A. Atmospheric dry deposition of legacy and emerging per-and polyfluoroalkyl substances (PFAS) in North Carolina. In Proceedings of the 2021 Emerging Contaminants in the Environment Conference (EPCEPC21), Champaign, IL, USA, 27–28 April 2021. [Google Scholar]
  17. Wang, Q.; Guo, S.; Hou, Z.; Lin, H.; Liang, H.; Wang, L.; Luo, Y.; Ren, H. Rainfall facilitates the transmission and proliferation of antibiotic resistance genes from ambient air to soil. Sci. Total Environ. 2021, 799, 149260. [Google Scholar] [CrossRef]
  18. Seiber, J.N.; Cahill, T.M. Pesticides, Organic Contaminants, and Pathogens in Air: Chemodynamics, Health Effects, Sampling, and Analysis; Taylor & Francis: Abingdon, UK, 2022; p. 260. [Google Scholar]
  19. Rodrigo, A.; Àvila, A.; Rodà, F. The chemistry of precipitation, throughfall and stemflow in two holm oak (Quercus ilex L.) forests under a contrasted pollution environment in NE Spain. Sci. Total Environ. 2003, 305, 195–205. [Google Scholar] [CrossRef]
  20. Ziegler, A.D.; Giambelluca, T.W.; Nullet, M.A.; Sutherland, R.A.; Tantasarin, C.; Vogler, J.B.; Negishi, J.N. Throughfall in an evergreen-dominated forest stand in northern Thailand: Comparison of mobile and stationary methods. Agric. For. Meteorol. 2009, 149, 373–384. [Google Scholar] [CrossRef]
  21. Hansen, K.; Draaijers, G.P.; Ivens, W.P.; Gundersen, P.; Vanleeuwen, N. Concentration variations in rain and canopy throughfall collected sequentially during individual rain events. Atmos. Environ. 1994, 28, 3195–3205. [Google Scholar] [CrossRef]
  22. Draaijers, G.; Erisman, J.; Leeuwen, N.; Römer, F.; Winkel, B.; Veltkamp, A.; Vermeulen, A.; Wyers, G. The impact of canopy exchange on differences observed between atmospheric deposition and throughfall fluxes. Atmos. Environ. 1997, 31, 387–397. [Google Scholar] [CrossRef]
  23. Návar, J.; González, J.M.; Gonzalez, H. Gross precipitation and throughfall chemistry in legume species planted in Northeastern México. Plant Soil 2008, 318, 15–26. [Google Scholar] [CrossRef]
  24. Polkowska, Ż.; Skarżyńska, K.; Górecki, T.; Namieśnik, J. Formaldehyde in various forms of atmospheric precipitation and deposition from highly urbanized regions. J. Atmos. Chem. 2006, 53, 211–236. [Google Scholar] [CrossRef]
  25. Van Stan, J.T.; Ponette-González, A.G.; Swanson, T.; Weathers, K.C. Throughfall and stemflow are major hydrologic highways for particulate traffic through tree canopies. Front. Ecol. Environ. 2021, 19, 404–410. [Google Scholar] [CrossRef]
  26. McGrath, B.; Sangawongse, S.; Thaikatoo, D.; Corte, M.B. The architecture of the metacity: Land use change, patch dynamics and urban form in chiang Mai, Thailand. Urban Plan. 2017, 2, 53–71. [Google Scholar] [CrossRef]
  27. Gugino, H.; Irvine, K.; Ngern-klun, R.; Sukontason, K.; Sukontason, K.; Prangkio, C.; Thunyapar, P. Impacts of the urban environment on area water source: The Klong Mae Kha-Chiang Mai, Thailand. In Proceedings of the Fourth International Symposium on Southeast Asian Water Environment, Bangkok, Thailand, 6–8 December 2006; pp. 85–88. [Google Scholar]
  28. Itayama, T.; Hawkins, P.R.; Leelahakriengkrai, P.; Kullasoot, S.; Whangchai, N.; Chitmanat, C.; Kawabata, Z.I. Bioassessment of dry season water quality in the Ping River around Chiang Mai City, Thailand. Chiang Mai J. Sci. 2015, 42, 349–366. [Google Scholar]
  29. Vanwambeke, S.O.; Somboon, P.; Lambin, E.F. Rural transformation and land use change in northern Thailand. J. Land Use Sci. 2007, 2, 1–29. [Google Scholar] [CrossRef]
  30. Harnpicharnchai, K.; Chaiear, N.; Charerntanyarak, L. Residues of organophosphate pesticides used in vegetable cultivation in ambient air, surface water and soil in Bueng Niam Subdistrict, Khon Kaen, Thailand. Southeast Asian J. Trop. Med. Public Health 2013, 44, 1088–1097. [Google Scholar]
  31. Chuah, C.J.; Mukhaidin, N.; Choy, S.H.; Smith, G.J.; Mendenhall, I.H.; Lim, Y.A.; Ziegler, A.D. Prevalence of Cryptosporidium and Giardia in the water resources of the Kuang River catchment, Northern Thailand. Sci. Total Environ. 2016, 562, 701–713. [Google Scholar] [CrossRef]
  32. Chuah, C.J.; Ziegler, A.D. Temporal variability of faecal contamination from On-Site sanitation systems in the groundwater of Northern Thailand. Environ. Manag. 2018, 61, 939–953. [Google Scholar] [CrossRef]
  33. Ziegler, A.D.; Benner, S.G.; Tantasirin, C.; Wood, S.H.; Sutherland, R.A.; Sidle, R.C.; Jachowski, N.; Nullet, M.A.; Xi, L.X.; Snidvongs, A.; et al. Turbidity-based sediment monitoring in northern Thailand: Hysteresis, variability, and uncertainty. J. Hydrol. 2014, 519, 2020–2039. [Google Scholar] [CrossRef]
  34. Sidle, R.C.; Ziegler, A.D. The canopy interception–landslide initiation conundrum: Insight from a tropical secondary forest in northern Thailand. Hydrol. Earth Syst. Sci. 2017, 21, 651–667. [Google Scholar] [CrossRef]
  35. Wood, S.H.; Ziegler, A.D. Floodplain sediment from a 30-year-recurrence flood in 2005 of the Ping River in northern Thailand. Hydrol. Earth Syst. Sci. Discuss. 2007, 4, 3839–3868. [Google Scholar]
  36. Rippen, G.; Zietz, E.; Frank, R.; Knacker, T.; Klöpffer, W. Do airborne nitrophenols contribute to forest decline? Environ. Technol. Lett. 1987, 8, 475–482. [Google Scholar] [CrossRef]
  37. Richartz, H.; Reischl, A.; Trautner, F.; Hutzinger, O. Nitrated phenols in fog. Atmos. Environ. Gen. Top. 1990, 24, 3067–3071. [Google Scholar] [CrossRef]
  38. Levsen, K.; Behnert, S.; Mussmann, P.; Raabe, M.; Priess, B. Organic compounds in cloud and rain water. Int. J. Environ. Anal. Chem. 1993, 52, 87–97. [Google Scholar] [CrossRef]
  39. Shussler, W.; Nitschke, L. Nitrophenols in precipitation. Chemosphere 2001, 42, 277. [Google Scholar] [CrossRef]
  40. Hofmann, D.; Hartmann, F.; Herrmann, H. Analysis of nitrophenols in cloud water with a miniaturized light-phase rotary perforator and HPLC-MS. Anal. Bioanal. Chem. 2008, 391, 161–169. [Google Scholar] [CrossRef]
  41. Polyakova, O.V.; Artaev, V.B.; Lebedev, T. Priority and emerging pollutants in the Moscow rain. Sci. Total Environ. 2018, 645, 1126–1134. [Google Scholar] [CrossRef]
  42. Ganranoo, L.; Mishra, S.K.; Azad, A.K.; Shigihara, A.; Dasgupta, P.K.; Breitbach, Z.S.; Armstrong, D.W.; Grudpan, K.; Rappenglueck, B. Measurement of Nitrophenols in Rain and Air by Two-Dimensional Liquid Chromatography−Chemically Active Liquid Core Waveguide Spectrometry. Anal. Chem. 2010, 82, 5838–5843. [Google Scholar] [CrossRef]
  43. Levsen, K.; Behnert, S.; Prieß, B.; Svoboda, M.; Winkeler, H.-D.; Zietlow, J. Organic compounds in precipitation. Chemosphere 1990, 21, 1037–1061. [Google Scholar] [CrossRef]
  44. Belloli, R.; Bolzacchini, E.; Clerici, L.; Rindone, B.; Sesana, G.; Librando, V. Nitrophenols in air and rainwater. Environ. Eng. Sci. 2006, 23, 405–415. [Google Scholar] [CrossRef]
  45. Bossi, R.; Vejrup, K.; Mogensen, B.; Asman, W. Analysis of polar pesticides in rainwater in Denmark by liquid chromatography–tandem mass spectrometry. J. Chromatogr. A 2002, 957, 27–36. [Google Scholar] [CrossRef] [PubMed]
  46. Harrison, M.A.; Barra, S.; Borghesi, D.; Vione, D.; Arsene, C.; Olariu, R.I. Nitrated phenols in the atmosphere: A review. Atmos. Environ. 2005, 39, 231–248. [Google Scholar] [CrossRef]
  47. Natangelo, M.; Mangiapan, S.; Bagnati, R.; Benfenati, E.; Fanelli, R. Increased concentrations of nitrophenols in leaves from a damaged forestal site. Chemosphere 1999, 38, 1495–1503. [Google Scholar] [CrossRef]
  48. Schwarzenbach, R.P.; Stierli, R.; Folsom, B.R.; Zeyer, J. Compound properties relevant for assessing the environmental partitioning of nitrophenols. Environ. Sci. Technol. 1988, 22, 83–92. [Google Scholar] [CrossRef] [PubMed]
  49. Li, S.; Wen, J.; He, B.; Wang, J.; Hu, X.; Liu, J. Occurrence of caffeine in the freshwater environment: Implications for ecopharmacovigilance. Environ. Pollut. 2020, 263, 114371. [Google Scholar] [CrossRef] [PubMed]
  50. Sidhu, J.P.S.; Ahmed, W.; Gernjak, W.; Aryal, R.; McCarthy, D.; Palmer, A.; Kolotelo, P.; Toze, S. Sewage pollution in urban stormwater runoff as evident from the widespread presence of multiple microbial and chemical source tracking markers. Sci. Total Environ. 2013, 463–464, 488–496. [Google Scholar] [CrossRef]
  51. Liu, N.; Jin, X.; Yan, Z.; Luo, Y.; Feng, C.; Fu, Z.; Tang, Z.; Wu, F.; Giesy, J.P. Occurrence and multiple-level ecological risk assessment of pharmaceuticals and personal care products (PPCPs) in two shallow lakes of China. Environ. Sci. Eur. 2020, 32, 27. [Google Scholar] [CrossRef]
  52. You, L.; Nguyen, V.T.; Pal, A.; Chen, H.; He, Y.; Reinhard, M.; Gin, K.Y.-H. Investigation of pharmaceuticals, personal care products and endocrine disrupting chemicals in a tropical urban catchment and the influence of environmental factors. Sci. Total Environ. 2015, 536, 955–963. [Google Scholar] [CrossRef]
  53. Tran, N.H.; Reinhard, M.; Khan, E.; Chen, H.; Nguyen, V.T.; Li, Y.; Goh, S.G.; Nguyen, Q.; Saeidi, N.; Gin, K.Y.-H. Emerging contaminants in wastewater, stormwater runoff, and surface water: Application as chemical markers for diffuse sources. Sci. Total Environ. 2019, 676, 252–267. [Google Scholar] [CrossRef]
  54. Waso, M.; Ndlovu, T.; Dobrowsky, P.H.; Khan, S.; Khan, W. Presence of microbial and chemical source tracking markers in roof-harvested rainwater and catchment systems for the detection of fecal contamination. Environ. Sci. Pollut. Res. 2016, 23, 16987–17001. [Google Scholar] [CrossRef]
  55. Waso, M. Identifying the Primary Microbial and Chemical Source Tracking Markers in Harvested Rainwater for the Detection of Faecal Contamination. Ph.D. Thesis, University of Stellenbosch, SA, Stellenbosch, South Africa, 2017. Available online: https://core.ac.uk/download/pdf/188219886.pdf (accessed on 30 September 2023).
  56. Burant, A.; Selbig, W.; Furlong, E.T.; Higgins, C.P. Trace organic contaminants in urban runoff: Associations with urban land-use. Environ. Pollut. 2018, 242, 2068–2077. [Google Scholar] [CrossRef] [PubMed]
  57. Fairbairn, D.J.; Elliott, S.M.; Kiesling, R.L.; Schoenfuss, H.L.; Ferrey, M.L.; Westerhoff, B.M. Contaminants of emerging concern in urban stormwater: Spatiotemporal patterns and removal by iron-enhanced sand filters (IESFs). Water Res. 2018, 145, 332–345. [Google Scholar] [CrossRef] [PubMed]
  58. González-Alonso, S.; Merino, L.M.; Esteban, S.; de Alda, M.L.; Barceló, D.; Durán, J.J.; López-Martínez, J.; Aceña, J.; Pérez, S.; Mastroianni, N.; et al. Occurrence of pharmaceutical, recreational and psychotropic drug residues in surface water on the northern Antarctic Peninsula region. Environ. Pollut. 2017, 229, 241–254. [Google Scholar] [CrossRef] [PubMed]
  59. Mihajlović, I.; Fries, E. Atmospheric deposition of chlorinated organophosphate flame retardants (OFR) onto soils. Atmospheric Environ. 2012, 56, 177–183. [Google Scholar] [CrossRef]
  60. Shi, Y.; Gao, L.; Li, W.; Wang, Y.; Liu, J.; Cai, Y. Occurrence, distribution and seasonal variation of organophosphate flame retardants and plasticizers in urban surface water in Beijing, China. Environ. Pollut. 2016, 209, 1–10. [Google Scholar] [CrossRef]
  61. Regnery, J.; Püttmann, W. Seasonal fluctuations of organophosphate concentrations in precipitation and storm water runoff. Chemosphere 2010, 78, 958–964. [Google Scholar] [CrossRef]
  62. Regnery, J.; Püttmann, W. Occurrence and fate of organophosphorus flame retardants and plasticizers in urban and remote surface waters in Germany. Water Res. 2010, 44, 4097–4104. [Google Scholar] [CrossRef]
  63. Marklund, A.; Andersson, B.; Haglund, P. Traffic as a Source of Organophosphorus Flame Retardants and Plasticizers in Snow. Environ. Sci. Technol. 2005, 39, 3555–3562. [Google Scholar] [CrossRef]
  64. Bacaloni, A.; Cucci, F.; Guarino, C.; Nazzari, M.; Samperi, R.; Laganà, A. Occurrence of Organophosphorus Flame Retardant and Plasticizers in Three Volcanic Lakes of Central Italy. Environ. Sci. Technol. 2008, 42, 1898–1903. [Google Scholar] [CrossRef]
  65. Fries, E.; Püttmann, W. Occurrence of organophosphate esters in surface water and groundwater in Germany. J. Environ. Monit. 2001, 3, 621–626. [Google Scholar] [CrossRef]
  66. Fries, E.; Püttmann, W. Monitoring of the three organophosphate esters TBP, TCEP and TBEP in river water and ground water (Oder, Germany). J. Environ. Monit. 2003, 5, 346–352. [Google Scholar] [CrossRef] [PubMed]
  67. Laohaudomchok, W.; Nankongnab, N.; Siriruttanapruk, S.; Klaimala, P.; Lianchamroon, W.; Ousap, P.; Jatiket, M.; Kajitvichyanukul, P.; Kitana, N.; Siriwong, W.; et al. Pesticide use in Thailand: Current situation, health risks, and gaps in research and policy. Hum. Ecol. Risk Assess. Int. J. 2020, 27, 1147–1169. [Google Scholar] [CrossRef] [PubMed]
  68. Sakai, M. Acute toxic tests of rainwater samples using Daphnia magna. Ecotoxicol. Environ. Saf. 2006, 64, 215–220. [Google Scholar] [CrossRef] [PubMed]
  69. Nohara, S.; Hanazato, T.; Iwakuma, T. Pesticide Residue Flux from Rainwater into Lake Nakanuma in the Rainy Season. Jpn. J. Limnol. 1997, 58, 385–393. [Google Scholar] [CrossRef]
  70. Suzuki, S.; Otani, T.; Iwasaki, S.; Ito, K.; Omura, H.; Tanaka, Y. Monitoring of 15 Pesticides in Rainwater in Utsunomiya, Eastern Japan, 1999–2001. J. Pestic. Sci. 2003, 28, 1–7. [Google Scholar] [CrossRef]
  71. Haraguchi, K.; Kitamura, E.; Yamashita, T.; Kido, A. Simultaneous determination of trace pesticides in urban precipitation. Atmos. Environ. 1995, 29, 247–253. [Google Scholar] [CrossRef]
  72. Chau, N.D.G.; Sebesvari, Z.; Amelung, W.; Renaud, F.G. Pesticide pollution of multiple drinking water sources in the Mekong Delta, Vietnam: Evidence from two provinces. Environ. Sci. Pollut. Res. 2015, 22, 9042–9058. [Google Scholar] [CrossRef]
  73. Miller, S.M.; Sweet, C.W.; DePinto, J.V.; Hornbuckle, K.C. Atrazine and Nutrients in Precipitation: Results from the Lake Michigan Mass Balance Study. Environ. Sci. Technol. 1999, 34, 55–61. [Google Scholar] [CrossRef]
  74. Mast, M.A.; Foreman, W.T.; Skaates, S.V. Current-Use Pesticides and Organochlorine Compounds in Precipitation and Lake Sediment from Two High-Elevation National Parks in the Western United States. Arch. Environ. Contam. Toxicol. 2007, 52, 294–305. [Google Scholar] [CrossRef]
  75. Villagómez-Márquez, N.; Abrell, L.; Foley, T.; Ramírez-Andreotta, M.D. Organic micropollutants measured in roof-harvested rainwater from rural and urban environmental justice communities in Arizona. Sci. Total Environ. 2023, 876, 162662. [Google Scholar] [CrossRef]
  76. Albanis, T.; Hela, D.; Sakellarides, T.; Konstantinou, I. Monitoring of pesticide residues and their metabolites in surface and underground waters of Imathia (N. Greece) by means of solid-phase extraction disks and gas chromatography. J. Chromatogr. A 1998, 823, 59–71. [Google Scholar] [CrossRef] [PubMed]
  77. Trautner, F.; Huber, K.; Niessner, R. Appearance and concentration ranges of atrazine in spring time cloud and rainwater from the Vosges France. J. Aerosol Sci. 1992, 23, 999–1002. [Google Scholar] [CrossRef]
  78. Bester, K.; Hühnerfuss, H.; Neudorf, B.; Thiemann, W. Atmospheric deposition of triazine herbicides in Northern Germany and the German Bight (North Sea). Chemosphere 1995, 30, 1639–1653. [Google Scholar] [CrossRef]
  79. Chevreuil, M.; Garmouma, M. Occurrence of triazines in the atmospheric fallout on the catchment basin of the River Marne (France). Chemosphere 1993, 27, 1605–1608. [Google Scholar] [CrossRef]
  80. Drevenkar, V.; Fingler, S.; Mendaš, G.; Stipičević, S.; Vasilić, Z. Levels of atrazine and simazine in waters in the rural and urban areas of North-West Croatia. Int. J. Environ. Anal. Chem. 2004, 84, 207–216. [Google Scholar] [CrossRef]
  81. Asman, W.A.; Jørgensen, A.; Bossi, R.; Vejrup, K.V.; Mogensen, B.B.; Glasius, M. Wet deposition of pesticides and nitrophenols at two sites in Denmark: Measurements and contributions from regional sources. Chemosphere 2005, 59, 1023–1031. [Google Scholar] [CrossRef]
  82. Kreuger, J.; Adielsson, S.; Kylin, H. Monitoring of Pesticides in Atmospheric Deposition in Sweden 2002–2005: Report to Swedish Environmental Protection Agency Contract No. 211 0543; Technical Report 103; Swedish University of Agricultural Sciences, Department Soil Sciences, Division of Water Quality Management: Uppsala, Sweden, 2006. [Google Scholar]
  83. Buser, H.R. Atrazine and other s-triazine herbicides in lakes and in rain in Switzerland. Environ. Sci. Technol. 1990, 24, 1049–1058. [Google Scholar] [CrossRef]
  84. Siebers, J.; Gottschild, D.; Nolting, H.-G. Pesticides in precipitation in Northern Germany. Chemosphere 1994, 28, 1559–1570. [Google Scholar] [CrossRef]
  85. Bucheli, T.D.; Müller, S.R.; Heberle, S.; Schwarzenbach, R.P. Occurrence and Behavior of Pesticides in Rainwater, Roof Runoff, and Artificial Stormwater Infiltration. Environ. Sci. Technol. 1998, 32, 3457–3464. [Google Scholar] [CrossRef]
  86. Scheyer, A.; Morville, S.; Mirabel, P.; Millet, M. Analysis of trace levels of pesticides in rainwater using SPME and GC–tandem mass spectrometry. Anal. Bioanal. Chem. 2005, 384, 475–487. [Google Scholar] [CrossRef]
  87. Wu, T.L. Atrazine residues in estuarine water and the aerial deposition of atrazine into Rhode River, Maryland. Water Air Soil Pollut. 1981, 15, 173–184. [Google Scholar] [CrossRef]
  88. Richards, R.P.; Kramer, J.W.; Baker, D.B.; Krieger, K.A. Pesticides in rainwater in the northeastern United States. Nature 1987, 327, 129–131. [Google Scholar] [CrossRef]
  89. Hall, J.C.; Van Deynze, T.D.; Struger, J.; Chan, C.H. Enzyme immunoassay based survey of precipitation and surface water for the presence of atrazine, metolachlor and 2,4-D. J. Environ. Sci. Health 1993, 28, 577–598. [Google Scholar] [CrossRef] [PubMed]
  90. Trevisan, M.; Montepiani, C.; Ragozza, L.; Bartoletti, C.; Ioannilli, E.; Del Re, A. Pesticides in rainfall and air in Italy. Environ. Pollut. 1993, 80, 31–39. [Google Scholar] [CrossRef] [PubMed]
  91. Dankwardt, A.; Wüst, S.; Elling, W.; Thurman, E.M.; Hock, B. Determination of atrazine in rainfall and surface water by enzyme immunoassay. Environ. Sci. Pollut. Res. 1994, 1, 196–204. [Google Scholar] [CrossRef]
  92. Nations, B.K.; Hallberg, G.R. Pesticides in Iowa precipitation. J. Environ. Qual. 1992, 21, 486–492. [Google Scholar] [CrossRef]
  93. Hatfield, J.L.; Wesley, C.K.; Prueger, J.H.; Pfeiffer, R.L. Herbicide and Nitrate Distribution in Central Iowa Rainfall. J. Environ. Qual. 1996, 25, 259–264. [Google Scholar] [CrossRef]
  94. Goolsby, D.A.; Thurman, E.M.; Pomes, M.L.; Meyer, M.T.; Battaglin, W.A. Herbicides and Their Metabolites in Rainfall: Origin, Transport, and Deposition Patterns across the Midwestern and Northeastern United States, 1990−1991. Environ. Sci. Technol. 1997, 31, 1325–1333. [Google Scholar] [CrossRef]
  95. Alonso, L.L.; Demetrio, P.M.; Etchegoyen, M.A.; Marino, D.J. Glyphosate and atrazine in rainfall and soils in agroproductive areas of the pampas region in Argentina. Sci. Total Environ. 2018, 645, 89–96. [Google Scholar] [CrossRef]
  96. Quaghebeur, D.; De Smet, B.; De Wulf, E.; Steurbaut, W. Pesticides in rainwater in Flanders, Belgium: Results from the monitoring program 1997–2001. J. Environ. Monit. 2004, 6, 182–190. [Google Scholar] [CrossRef]
  97. Lode, O.; Eklo, O.M.; Holen, B.; Svensen, A.; Johnsen, A.M. Pesticides in precipitation in Norway. Sci. Total Environ. 1995, 160–161, 421–431. [Google Scholar] [CrossRef]
  98. Dörfler, U.; Scheunert, I. S-triazine herbicides in rainwater with special reference to the situation in Germany. Chemosphere 1997, 35, 77–85. [Google Scholar] [CrossRef]
  99. Van Maanen, J.M.S.; de Vaan, M.A.J.; Veldstra, A.W.F.; Hendrix, W.P.A.M. Pesticides and nitrate in groundwater and rainwater in the Province of Limburg in The Netherlands. Environ. Monit. Assess. 2001, 72, 95–114. [Google Scholar] [CrossRef]
  100. Potter, T.L.; Coffin, A.W. Assessing pesticide wet deposition risk within a small agricultural watershed in the Southeastern Coastal Plain (USA). Sci. Total Environ. 2017, 580, 158–167. [Google Scholar] [CrossRef]
  101. Hirvi, J.P.; Rekolainen, S. Pesticides in precipitation and surface water in Finland. In: Arne Helweg (Ed.), Pesticides in Precipitation and Surface Water (Nordic seminar). TemaNord 1995, 558, 12–18. [Google Scholar]
  102. Rawn, D.F.K.; Halldorson, T.H.J.; Lawson, B.D.; Muir, D.C.G. A Multi-Year Study of Four Herbicides in Air and Precipitation from a Small Prairie Watershed. J. Environ. Qual. 1999, 28, 898–906. [Google Scholar] [CrossRef]
  103. Scheyer, A.; Morville, S.; Mirabel, P.; Millet, M. Pesticides analysed in rainwater in Alsace region (Eastern France): Comparison between urban and rural sites. Atmos. Environ. 2007, 41, 7241–7252. [Google Scholar] [CrossRef]
  104. Dubus, I.; Hollis, J.; Brown, C. Pesticides in rainfall in Europe. Environ. Pollut. 2000, 110, 331–344. [Google Scholar] [CrossRef]
  105. Sandmann, E.R.; de Beer, P.R.; van Dyk, L.P. Atmospheric pollution by auxin-type herbicides in Tala Valley, Natal. Chemosphere 1991, 22, 137–145. [Google Scholar] [CrossRef]
  106. Hill, B.D.; Harker, K.N.; Hasselback, P.; Inaba, D.J.; Byers, S.D.; Moyer, J.R. Herbicides in Alberta Rainfall as Affected by Location, Use and Season: 1999 to 2000. Water Qual. Res. J. 2002, 37, 515–542. [Google Scholar] [CrossRef]
  107. Datel, J.V.; Hrabankova, A. Pharmaceuticals Load in the Svihov Water Reservoir (Czech Republic) and Impacts on Quality of Treated Drinking Water. Water 2020, 12, 1387. [Google Scholar] [CrossRef]
  108. Peña-Guzmán, C.; Ulloa-Sánchez, S.; Mora, K.; Helena-Bustos, R.; Lopez-Barrera, E.; Alvarez, J.; Rodriguez-Pinzón, M. Emerging pollutants in the urban water cycle in Latin America: A review of the current literature. J. Environ. Manag. 2019, 237, 408–423. [Google Scholar] [CrossRef] [PubMed]
  109. Atkinson, R.; Guicherit, R.; Hites, R.A.; Palm, W.-U.; Seiber, J.N.; de Voogt, P. Transformations of Pesticides in the Atmosphere: A State of the Art. Water Air Soil Pollut. 1999, 115, 219–243. [Google Scholar] [CrossRef]
  110. Unsworth, J.B.; Wauchope, R.D.; Klein, A.-W.; Dorn, E.; Zeeh, B.; Yeh, S.M.; Akerblom, M.; Racke, K.D.; Rubin, B. Significance of the Long Range Transport of Pesticides in the Atmosphere. Pure Appl. Chem. 1999, 71, 1359–1383. [Google Scholar] [CrossRef]
  111. Tong, X.; Mohapatra, S.; Zhang, J.; Tran, N.H.; You, L.; He, Y.; Gin, K.Y.-H. Source, fate, transport and modelling of selected emerging contaminants in the aquatic environment: Current status and future perspectives. Water Res. 2022, 217, 118418. [Google Scholar] [CrossRef]
  112. Corrêa, J.M.M.; Sanson, A.L.; Machado, C.F.; Aquino, S.F.; Afonso, R.J.C.F. Occurrence of contaminants of emerging concern in surface waters from Paraopeba River Basin in Brazil: Seasonal changes and risk assessment. Environ. Sci. Pollut. Res. 2021, 28, 30242–30254. [Google Scholar] [CrossRef]
  113. Ebele, A.J.; Oluseyi, T.; Drage, D.S.; Harrad, S.; Abdallah, M.A.-E. Occurrence, seasonal variation and human exposure to pharmaceuticals and personal care products in surface water, groundwater and drinking water in Lagos State, Nigeria. Emerg. Contam. 2020, 6, 124–132. [Google Scholar] [CrossRef]
  114. Sun, J.; Mu, Q.; Kimura, H.; Murugadoss, V.; He, M.; Du, W.; Hou, C. Oxidative degradation of phenols and substituted phenols in the water and atmosphere: A review. Adv. Compos. Hybrid Mater. 2022, 5, 627–640. [Google Scholar] [CrossRef]
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Figure 1. Study area where rainfall and throughfall (RF+TF), reservoir (R), pond (P), and stream (S) samples were taken in Thailand. The large reservoir is Mae Kuang Udon Thara Reservoir in Chiang Mai province, Thailand. Most surface water sites were within a three km radius of the RF/TF sites (circle); reservoirs R59 and R60 are 17 km away. The rainfall/throughfall (RF/TF) collection site is about 19 km from the city center (square in inset (B)). Field site location is shown in inset (A).
Figure 1. Study area where rainfall and throughfall (RF+TF), reservoir (R), pond (P), and stream (S) samples were taken in Thailand. The large reservoir is Mae Kuang Udon Thara Reservoir in Chiang Mai province, Thailand. Most surface water sites were within a three km radius of the RF/TF sites (circle); reservoirs R59 and R60 are 17 km away. The rainfall/throughfall (RF/TF) collection site is about 19 km from the city center (square in inset (B)). Field site location is shown in inset (A).
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Figure 2. The relationship between rainfall and throughfall for 96 pairs of samples collected at the RF + TF monitoring site (854 individual collector measurements are shown; this is more data than the EPC concentrations were determined on). Mean throughfall is estimated as 0.80 ± 0.3 of rainfall. Based on the linear model shown in the figure (dotted line), throughfall depth is 0.75 the rainfall depth; median event throughfall was 0.77.
Figure 2. The relationship between rainfall and throughfall for 96 pairs of samples collected at the RF + TF monitoring site (854 individual collector measurements are shown; this is more data than the EPC concentrations were determined on). Mean throughfall is estimated as 0.80 ± 0.3 of rainfall. Based on the linear model shown in the figure (dotted line), throughfall depth is 0.75 the rainfall depth; median event throughfall was 0.77.
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Figure 3. Comparison of EPC concentrations for rainfall and throughfall paired samples. The below detection limit (bdl) value is set manually at 2.5 ng/L for visualization. The six main EPCs are shown in panels (a) 4-nitrophenol; (b) caffeine; (c) TBEP; (d) Fenobucarb; (e) Atrazine; and (f) 2,4-D. Month 1 is January; 6 is June; etc. Pairs are offset slightly to preserve visibility. Duplicate values for bdl are not visible. There are no paired data for month 7. Shading highlights the wet period.
Figure 3. Comparison of EPC concentrations for rainfall and throughfall paired samples. The below detection limit (bdl) value is set manually at 2.5 ng/L for visualization. The six main EPCs are shown in panels (a) 4-nitrophenol; (b) caffeine; (c) TBEP; (d) Fenobucarb; (e) Atrazine; and (f) 2,4-D. Month 1 is January; 6 is June; etc. Pairs are offset slightly to preserve visibility. Duplicate values for bdl are not visible. There are no paired data for month 7. Shading highlights the wet period.
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Figure 4. Comparison of rainfall versus throughfall concentration for the six more prevalent EPCs studied; 4-nitrophenol was systematically higher in rainfall than throughfall. Values below detection limit (bdl) are plotted at 2.5 ng/L for visibility.
Figure 4. Comparison of rainfall versus throughfall concentration for the six more prevalent EPCs studied; 4-nitrophenol was systematically higher in rainfall than throughfall. Values below detection limit (bdl) are plotted at 2.5 ng/L for visibility.
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Figure 5. Comparison of EPC concentrations in two ponds (P02, P30), two reservoirs (R04, R25), one stream (S25), and 44 combined rainfall and throughfall samples. June (month 6) combines data from 2021 and 2022. Values below detection limit (bdl) are plotted at ~2.5 ng/L for visibility. Data for R59 and R60 are not shown. The six main EPCs are shown in panels (a) 4-nitrophenol; (b) caffeine; (c) TBEP; (d) Fenobucarb; (e) Atrazine; and (f) 2,4-D. Dry deposition and rainfall-only samples are included in the graph (these data are listed in Supplement item S2). Month 1 is January; 6 is June, etc. Shading highlights the wet period.
Figure 5. Comparison of EPC concentrations in two ponds (P02, P30), two reservoirs (R04, R25), one stream (S25), and 44 combined rainfall and throughfall samples. June (month 6) combines data from 2021 and 2022. Values below detection limit (bdl) are plotted at ~2.5 ng/L for visibility. Data for R59 and R60 are not shown. The six main EPCs are shown in panels (a) 4-nitrophenol; (b) caffeine; (c) TBEP; (d) Fenobucarb; (e) Atrazine; and (f) 2,4-D. Dry deposition and rainfall-only samples are included in the graph (these data are listed in Supplement item S2). Month 1 is January; 6 is June, etc. Shading highlights the wet period.
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Figure 6. Comparison of concentrations of two classes of EPCs in rainfall and throughfall samples: industrial (4-nitrophenol and TBEP) and agricultural (atrazine and fenobucarb).
Figure 6. Comparison of concentrations of two classes of EPCs in rainfall and throughfall samples: industrial (4-nitrophenol and TBEP) and agricultural (atrazine and fenobucarb).
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Table 1. Summary statistics for six prevalent EPCs, four infrequently occurring EPCS, and other variables in the paired rainfall (RF) and throughfall (TF) samples.
Table 1. Summary statistics for six prevalent EPCs, four infrequently occurring EPCS, and other variables in the paired rainfall (RF) and throughfall (TF) samples.
UnitRainfall (ng/L) aThroughfall (ng/L) aRho bField Banks f
n-2222-44
4-Nitrophenolng/L1431 (6870) 1.0810 (7127) 1.00.90Bdl e
Caffeineng/L133 (908) 0.82141 (1176) 1.00.75bdl (553) g
TBEPng/L45 (168) 0.6448 (292) 0.690.96bdl
Fenobucarbng/L13 (299) 0.4630 (342) 0.600.88bdl
Atrazineng/Lbdl (95) 0.46bdl (81) 0.460.91bdl
2,4-Dng/Lbdl (26) 0.14bdl (74) 0.32ND dbdl
Acetaminophenng/Lbdl (2054) 0.23bdl (1103) 0.05NDbdl
Fexofenadineng/Lbdlbdl (103) 0.14NDbdl
Diphenhydramineng/Lbdl (208) 0.1bdlNDbdl
Gabapentinng/Lbdlbdl (bdl–2059) 0.05NDbdl
DOCmg/L5.04 (2.48–1245) 1.022.07 (6.96–137.6) 1.0NDND
TNmg/L0.48 (0.21–3.13) 1.00.75 (0.39–8.51) 1.0NDND
n (pH and SEC)-10164NDND
pH-6.83 (5.08–8.71)6.15 (4.93–8.44)NDND
SEC cµS/cm8.2 (2–50)18.5 (2–105)NDND
(a) Values are medians, maximums, and detection frequency. (b) Rho is the Spearman rank correlation coefficient. (c) SEC is specific conductivity. (d) ND means not determined (either not relevant or too few data). (e) bdl is below detection level. (f) Field blank EPC data are listed in detail in (Supplement item S2). (g) Only one value of caffeine was above detection limit.
Table 2. Median concentrations (ng/L), maximum concentrations (ng/L), and detection frequencies for the six most prevalent EPCs in seven water bodies, for samples collected across the year.
Table 2. Median concentrations (ng/L), maximum concentrations (ng/L), and detection frequencies for the six most prevalent EPCs in seven water bodies, for samples collected across the year.
4-NitrophenolCaffeineTBEPFenobucarbAtrazine2,4-D
Pond (P02)8 (66) 0.5459 (1532) 0.5426 (344) 0.75bdl11 (38) 0.690 (32) 0.31
Reservoir (R04)bdl (46) 0.31bdl (1209) 0.4612 (122) 0.55bdl (24) 0.08bdl (12) 0.46bdl
Reservoir (R25)8 (72) 0.58210 (424) 0.92bdl (20) 0.20bdlbdl (7) 0.17bdl
Pond (P30)bdl (69) 0.42bdl (373) 0.426 (124) 0.50bdl (95) 0.1722 (53) 1.000 (26)
Stream (S42)bdl (35) 0.3399 (896) 0.75bdl (131) 0.3010 (875) 0.58229 (970) 1.0017 (2699) 0.67
Reservoir (R59)bdl (45) 0.25bdl (494) 0.386 (127) 0.50bdlbdl (6) 0.13bdl
Reservoir (R60)bdl (69) 0.33bdl (116) 0.4413 (128) 0.57bdlbdl (19) 0.45bdl
bdl refers to below detection limit. Field blank data are reported in Table 1; locations are shown in Figure 1. Sample numbers are 13 (P02, R04), 12 (R25, P30, S42), 8 (R59), and 9 (R60).
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Lee, T.H.Y.; Srinuansom, K.; Snyder, S.A.; Ziegler, A.D. Atmosphere-Transported Emerging and Persistent Contaminants (EPCs) in Rainfall and Throughfall: Insights from a Rural Site in Northern Thailand. Atmosphere 2023, 14, 1603. https://doi.org/10.3390/atmos14111603

AMA Style

Lee THY, Srinuansom K, Snyder SA, Ziegler AD. Atmosphere-Transported Emerging and Persistent Contaminants (EPCs) in Rainfall and Throughfall: Insights from a Rural Site in Northern Thailand. Atmosphere. 2023; 14(11):1603. https://doi.org/10.3390/atmos14111603

Chicago/Turabian Style

Lee, Theodora H.Y., Khajornkiat Srinuansom, Shane A. Snyder, and Alan D. Ziegler. 2023. "Atmosphere-Transported Emerging and Persistent Contaminants (EPCs) in Rainfall and Throughfall: Insights from a Rural Site in Northern Thailand" Atmosphere 14, no. 11: 1603. https://doi.org/10.3390/atmos14111603

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