Search Results (98)

Lead (Pb) is one of the most relevant contaminants due to its high toxicity, even at low concentrations. The growing need for research about real-time Pb analysis in the field has driven advancements in portable, sensitive, and automated analytical methodologies. These innovations are crucial for taking proactive measures against the impacts of Pb pollution on ecosystems and public health. Flow analysis techniques have proven to be very effective in automating procedures for isolating and preconcentrating Pb in surface water and biological samples. Such automation boosts sample throughput and reduces processing time and reagent consumption, aligning with the green chemistry principles by lowering costs and minimizing waste. This review covers 31 recent automated analytical methodologies employing flow analysis techniques such as FIA, SIA, MSFIA, and LOV, emphasizing the trend toward portability and miniaturization, which facilitates in-situ analysis. Additionally, this review examines the pretreatment methods and detection systems used, highlighting the analytical parameters of each technique. The methodologies discussed demonstrate the capability to process up to 55 samples per hour accurately. Limits of quantification as low as 0.014 µg L⁻¹ are reported, enabling environmental monitoring that effectively detects Pb concentrations below the WHO and EPA drinking water reference values of 10 µg L⁻¹ and 15 µg L⁻¹, respectively. Full article

Industrially applied bioelectrochemical systems require long-term stable operation, and hence the control of biofilm accumulation on the electrodes. An optimized application of biofilm control mechanisms presupposes on-line, in-situ monitoring of the accumulated biofilm. Heat transfer sensors have successfully been integrated into industrial systems for on-line, non-invasive monitoring of biofilms. In this study, a mathematical model for the description of the sensitivity of a heat transfer biofilm sensor was developed, incorporating the hydrodynamic conditions of the fluid and the geometrical properties of the substratum. This model was experimentally validated at different flow velocities by integrating biofilm sensors into cylindrical pipes and planar mesofluidic flow cells with a carbonaceous substratum. Dimensionless sensor readings were correlated with the mean biovolume measured gravimetrically, and optical coherence tomography was used to determine the sensors’ sensitivity. The biofilm sensors applied in the planar flow cells revealed an increase in sensitivity by a factor of 6 compared to standard stainless steel pipes, as well as improved sensitivity at higher flow velocities. Full article

Multicomponent gas mixture diffusion in a microscale confined flow in the transition gas regime at Knudsen numbers (Kn) above 0.1 has potential engineering applications in gas-phase microfluidics. Although the calculation of the diffusion coefficient accounts for the influence of the concentration of other species in a multicomponent gas mixture, the higher rate of gas-wall collision at 0.1 < Kn ≤ 10 introduces additional complications not predicted by conventional calculation methods. Thus, simultaneous measurement of diffusion coefficients for multiple gas species ensures accurate estimation of the diffusion coefficient of a particular species that includes the effect of interactions with other species and wall surface conditions in a multicomponent gas mixture at Kn > 0.1. However, most experimental methods for measuring the diffusion coefficient are not species-specific and therefore cannot directly differentiate between the species diffusing in a gas mixture. Thus, this paper demonstrates a new experiment methodology consisting of a two-bulb diffusion configuration accompanied by a tunable diode laser absorption spectroscopy detection technique for species-specific, in-situ, simultaneous measurement of the effective diffusion coefficient for a CO₂-N₂O gas mixture in the transition gas regime. The experimental results are compared against direct simulation Monte Carlo calculations and the Bosanquet approximation showing a deviation that has not been reported in the literature before. Full article

The management of landscapes and agricultural activities significantly impacts phosphorus (P) and nitrogen (N) losses, directly influencing eutrophication risk. This study quantifies the eutrophication potential of different land covers through in-situ measurements and analysis of runoff and inorganic substances. The research was conducted in two sub-catchments in the Bedřichovský stream basin, Novohradské hory, Czech Republic: a forest-dominated upper sub-catchment (UFS) and an agricultural lower sub-catchment (LAS). Water flows and surface water samples were measured over a hydrological year (November 2017 to October 2018) to determine runoff and concentrations of nitrate (N-NO₃⁻) and phosphate (P-PO₄³⁻). The ReCiPe 2016 method, as a tool for LCIA, was used to quantify the eutrophication potential, converting N and P concentrations into nitrogen equivalents (N eq ha⁻¹ sub-catchment) for marine eutrophication and phosphorus equivalents (P eq ha⁻¹ sub-catchment) for freshwater eutrophication. The potential loss of species (species·yr ha⁻¹ sub-catchment) was assessed as follows. Results indicate UFS has about 60% lower freshwater and 80% lower marine eutrophication potential compared to LAS, along with about 60% lower potential for biodiversity loss. This highlights the role of forest and grassland covers in mitigating eutrophication and protecting water sources. These findings can guide landscape management practices to reduce eutrophication potential, enhancing environmental quality and biodiversity conservation. Full article

A continuous flow with reagent injection method on a novel inlaid microfluidic platform for nitrite determination has been successfully developed. The significance of the high-frequency monitoring of nutrient fluctuations in marine environments is crucial for understanding our impacts on the ecosystem. Many in-situ systems face limitations in high-frequency data collection and have restricted deployment times due to high reagent consumption. The proposed microfluidic device employs automatic colorimetric absorbance spectrophotometry, using the Griess assay for nitrite determination, with minimal reagent usage. The sensor incorporates 10 solenoid valves, four syringes, two LEDs, four photodiodes, and an inlaid microfluidic technique to facilitate optical measurements of fluid volumes. In this flow system, Taylor–Aris dispersion was simulated for different injection volumes at a constant flow rate, and the results have been experimentally confirmed using red food dye injection into a carrier stream. A series of tests were conducted to determine a suitable injection frequency for the reagent. Following the initial system characterization, seven different standard concentrations ranging from 0.125 to 10 µM nitrite were run through the microfluidic device to acquire a calibration curve. Three different calibrations were performed to optimize plug length, with reagent injection volumes of 4, 20, and 50 µL. A straightforward signal processing method was implemented to mitigate the Schlieren effect caused by differences in refractive indexes between the reagent and standards. The results demonstrate that a sampling frequency of at least 10 samples per hour is achievable using this system. The obtained attenuation coefficients exhibited good agreement with the literature, while the reagent consumption was significantly reduced. The limit of detection for a 20 µL injection volume was determined to be 94 nM from the sample intake, and the limit of quantification was 312 nM. Going forward, the demonstrated system will be packaged in a submersible enclosure to facilitate in-situ colorimetric measurements in marine environments. Full article

The climatic warming-induced shrinking of permafrost currently encompasses 65% of alpine areas in North China, where a large population relies on its water and land resources. With increasing recognition of the economic and ecological impacts of permafrost basins, forecasts of environmental vulnerability have gained prominence. However, the links between permafrost and winter water resources remain inadequately explored, with most studies focusing on in-situ measurements related to snow cover and frozen layer thickness. Evaluating more complex phenomena, such as the magnitude and persistence of air temperature or low streamflow, depends on numerous climate-driven factors interacting through various subsurface flow mechanisms, basin drainage mechanics, and hydro-climatic correlations at a macroscale. The present study focuses on winter warming, flow increases, and their teleconnections in Xinjiang, China. The research analyzes their links to the atmospheric cycle of the Siberian High (SH) using long-term data spanning 55 years from two large alpine permafrost basins. Changes in variability and correlation persistence were explored for the past decades, and significant variability and connections were constructed using statistical correlation. The years 1980 and 1990 were a turning point when both winter temperatures and winter river flow began to exhibit a notable and consistent upward trend. Subsequently, the period from the mid-1990s to 2013 was characterized by high variability and persistence in these trends. The influence of the SH plays a dominant role in regard to both winter temperatures and river flow, and these variabilities and correlations can be utilized to estimate and predict winter flow in ungauged permafrost rivers in Xinjiang China. Full article

Atmospheric radon measurements assist in many aspects of climate and meteorological research, notably as an airmass tracer and for modelling boundary layer development, mixing heights and stability. Daughter products from radon decay are sometimes incorporated into the particle pollution measurements of commercially available beta-attenuation monitors (BAM). BAMs incorporating radon measurements are used in air quality monitoring networks and can supplement traditional radon measurements. Here we compare in-situ radon measurements from Thermo Fisher Scientific (Franklin, MA, USA) BAM instruments (Thermo Scientific 5014i, Thermo Scientific 5030 SHARP, Thermo Anderson FH62C14) at two air quality monitoring stations in New South Wales, Australia. Between systems we find strong correlations for hourly measurements (r = 0.97–0.99); daily means (r = 0.97–0.99); hour of the day (r = 0.84–0.98); and month (r = 0.82–0.98). The regression analysis for radon measurements between systems showed strong linear responses, although there are some variations in the slopes of the regressions. This implies that with correction BAM measurements can be comparable to standard measurement techniques, for example, from the Australian Nuclear Science and Technology Organisation (ANSTO) dual flow loop monitors. Our findings imply that BAM derived radon measurements are precise, although their accuracy varies. BAM radon measurements can support studies on boundary layer development or where radon is used as an atmospheric transport tracer. Full article

In this study, we developed composite Fe-Cr-V-C coatings by plasma transferred-arc (PTA) powder surfacing on a 42CrMo steel substrate. The effects of arc current and ion gas flow rate on the coatings’ microstructure, hardness, and bonding performance were investigated. During the surfacing process, ${\mathrm{V}}_{\mathrm{x}}{\mathrm{C}}_{\mathrm{y}},{{\mathrm{M}}_7\mathrm{C}}_3\left(\mathrm{M}=\mathrm{F}\mathrm{e},\mathrm{C}\mathrm{r}\right)$ and other hard phases are in-situ generated throughout the entire PTA powder surfacing. These phases are uniformly distributed in the Fe matrix through precipitation and dispersion strengthening, yielding a surface hardness of up to 64.1 HRC. Also, the bonding performance between the substrate and coatings was evaluated by measuring the tensile strength, revealing that strong metallurgical bonds are formed, reaching a strength greater than 811 MPa. Full article

The COVID-19 pandemic put emergency departments all over the world under severe and unprecedented distress. Previous methods of evaluating patient flow impact, such as in-situ simulation, tabletop studies, etc., in a rapidly evolving pandemic are prohibitively impractical, time-consuming, costly, and inflexible. For instance, it is challenging to study the patient flow in the emergency department under different infection rates and get insights using in-situ simulation and tabletop studies. Despite circumventing many of these challenges, the simulation modeling approach and hybrid agent-based modeling stand underutilized. This study investigates the impact of increased patient infection rate on the emergency department patient flow by using a developed hybrid agent-based simulation model. This study reports findings on the patient infection rate in different emergency department patient flow configurations. This study’s results quantify and demonstrate that an increase in patient infection rate will lead to an incremental deterioration of the patient flow metrics average length of stay and crowding within the emergency department, especially if the waiting functions are introduced. Along with other findings, it is concluded that waiting functions, including the waiting zone, make the single average length of stay an ineffective measure as it creates a multinomial distribution of several tendencies. Full article

As the second most significant metal following steel, aluminum plays a vital role in the advancement of both strategic emerging industries and national economic development. The existing oil and gas drilling data indicate that the deep bauxite deposits is abundant around the Ordos Basin in China, at the depths ranging from several hundred meters to several kilometers. Based on the geological and hydrogeological characteristics analysis, it is found that deep bauxite deposits in the basin have distinct electrical characteristics, characterized by four highs and two lows. While there is scarcity of prior research on the exploration topic for the technique limitation. In this paper, a logging interpretation model has been developed, which allows the evaluation of bauxite deposits. An efficient technology was proposed for deep bauxite exploration, utilizing an in-situ leaching mining technique. This technology is well-suited to the geological conditions of the Ordos Basin, ensuring that the solution flows within the bauxite ore bed without any seepage loss. To prevent the leaching solution from seeping into and polluting the main aquifer around the basin, several measures have been proposed. These include filling with polymer resin, well pattern seepage control plugging, and establishing monitoring systems. The results of this study provide a theoretical basis for the adoption of environmentally sustainable mining techniques and the mitigation of water pollution in deep bauxite exploration. Full article

Large-scale groundwater flow modelling demands comprehensive geological investigation (GI) to accurately predict groundwater dynamics during open-cut and underground mining. Due to the existence of large-scale heterogeneity (e.g., fault and fracture) in natural geological strata (e.g., overburden soil, rock mass and coal seam), the in-situ flow measurement in boreholes, compared to laboratory seepage tests, can bring more reliable information to estimating the in-situ seepage properties (e.g., hydraulic conductivity, intrinsic permeability, transmissivity and specific yield). In this paper, a flow-measuring technique-heat pulse flowmeter (HPFM) is methodologically introduced and then practically applied for GI in the mining extension zone of Hunter Valley Operations (HVO), New South Wales, Australia. The measuring experiences, including both positive and negative outcomes, are reported and discussed with a series of datasets of in-situ flow rates measured in the selected boreholes. The pros and cons of the HPFM application in HVO are also discussed and summarised based on the user experience collected through this field trip. Finally, through a thorough reflection, some practical recommendations are provided to help other HPFM practitioners bypass all difficulties experienced on this trip. It is anticipated that valuable user information can contribute to better GI in other sites when performing this measuring technique. Full article

In view of the tremendous emissions of toxic gases and particulate matter (PM) by low-power firewood-fueled fireplaces, there is an urgent need for effective measures to lower emissions to keep this renewable and economical source for private home heating available in the future. For this purpose, an advanced combustion air control system was developed and tested on a commercial fireplace (HKD7, Bunner GmbH, Eggenfelden, Germany), complemented with a commercial oxidation catalyst (EmTechEngineering GmbH, Leipzig, Germany) placed in the post-combustion zone. Combustion air stream control of the wood-log charge combustion was realized by five different control algorithms to describe all situations of combustion properly. These control algorithms are based on the signals of commercial sensors representing catalyst temperature (thermocouple), residual oxygen concentration (LSU 4.9, Bosch GmbH, Gerlingen, Germany) and CO/HC-content in the exhaust (LH-sensor, Lamtec Mess- und Regeltechnik für Feuerungen GmbH & Co. KG, Walldorf (Germany)). The actual flows of the combustion air streams, as calculated for the primary and secondary combustion zone, are adjusted by motor-driven shutters and commercial air mass flow sensors (HFM7, Bosch GmbH, Gerlingen, Germany) in separate feedback control loops. For the first time, the residual CO/HC-content (CO, methane, formaldehyde, etc.) in the flue gas is in-situ monitored with a long-term stable AuPt/YSZ/Pt mixed potential high-temperature gas sensor, which allows continuous estimation of the flue gas quality with an accuracy of about ±10%. This parameter is not only an essential input for advanced combustion air stream control but also provides monitoring of the actual combustion quality and logging of this value over a whole heating period. By many firing experiments in the laboratory and by field tests over four months, it could be demonstrated that with this long-term stable and advanced automated firing system, depression of the gaseous emissions by about 90% related to manually operated fireplaces without catalyst could be achieved. In addition, preliminary investigations at a firing appliance complemented by an electrostatic precipitator yielded PM emission depression between 70% and 90%, depending on the firewood load. Full article

Groundwater-surface water interactions play a crucial role in hydrologic cycles, especially in arid and semi-arid basins. There is a growing interest in developing integrated hydrologic models to describe groundwater-surface water interactions and the associated processes. In this study, an integrated process-based hydrologic model, ParFlow, was tested and utilized to quantify the hydrologic responses, such as changes in surface runoff and surface/subsurface storage. We progressively conducted a complexity-increasing series of benchmarking cases to assess the performance of ParFlow in simulating overland flow and integrated groundwater-surface water exchange. Meanwhile, the overall performance and the computational efficiency were quantitatively assessed using modified Taylor diagrams. Based on the benchmarking cases, two case studies in the Heihe River Basin were performed for further validation and to diagnose the hydrologic responses under disturbance, named the Bajajihu (BJH) and Dayekou (DYK) cases, respectively. Both cases were 2D transects configured with in-situ measurements in the mid- and downstream of the Heihe River Basin. In the BJH case, simulated soil moisture by ParFlow was shown to be comparable with in-situ observations in general, with Pearson’s correlation coefficient (R) > 0.93 and root mean square difference (RMSD) < 0.007. In the DYK case, seven scenarios driven by remote sensing and reanalysis data were utilized to study hydrological responses influenced by natural physical processes (i.e., precipitation) and groundwater exploitations (i.e., pumping) that are critical to surface and subsurface storage. Results show that subsurface storage is sensitive to groundwater exploitation before an obvious stationary point. Moreover, a correlation analysis was additionally provided demonstrating the impacts of different factors on subsurface storage timeseries. It was found that pumping influences subsurface storage remarkably, especially under short-term but large-volume pumping rates. The study is expected to provide a powerful tool and insightful guidance in understanding hydrological processes’ effects in arid and semi-arid basins. Full article

This study investigated the role of bank return flow to two medium size rivers in southeast Queensland using a combination of hydrograph separation techniques and geochemical baseflow separations. The main aims were to provide a case study to demonstrate spatial and temporal variability in groundwater contributions to two river systems in Southeast Victoria; the Avon River and the Mitchell River. The two rivers show large spatial and temporal variations in groundwater contributions with higher percentages during low flow periods and more surface runoff during wet years. At the end of the Australian millennium drought, groundwater discharge accounted for 60% of the total flow for the Avon River and 42% for the Michell River, whereas groundwater discharge only had a minor component to the total discharge in wetter years, ∼15% for the Avon River and only 3% for the Mitchell River. Radon and chloride were used for the geochemical baseflow separation and provide a means to separate regional groundwater discharge to the rivers from bank return flow. Bank return flow accounts for 2 to 5 times higher fluxes in certain areas. Geochemistry in combination with physical hydrogeology enhances the overall understanding of groundwater connected river systems over the river length. Full article

Nutrient pollution may negatively affect the water quality and ecological status of rivers and estuaries worldwide, specifically in stratified and small inland estuaries. We present a long-term, two-decade data set of dissolved inorganic nutrient concentrations, chlorophyll-a (chl-a), dissolved oxygen (DO), and potentially toxic algal cell concentrations at the Kishon River estuary (Israel) as a case study for assessing nutrient ecological thresholds in such type of estuaries, prevalent along the Mediterranean coast of Israel. In-situ measurements and water samples were collected at 3 permanent stations at the lower part of the estuary every March and October/November in 40 campaigns over the years 2002 to 2021. In spite of an improvement in nutrient loads and concentrations as recorded over the last 2 decades, the nutrient and chl-a levels at the Kishon estuary surface water represent mostly a ‘bad’ or ‘moderate’ ecological state, considering the recommended thresholds discussed in this study. It is suggested to develop a combined suite of nutrient and biological variables for assessing Good Environmental Status (GES), considering the relatively high residence time of such small, low-flow estuarine water bodies. Full article