Evaluation of Water Quality in the Tamiš River in Serbia Using the Water Pollution Index: Key Pollutants and Their Sources

Abstract

This study evaluates the water quality of the Tamiš River, a tributary of the Danube, at the Jaša Tomić and Pančevo hydrological stations from 2011 to 2016 and from 2018 to 2022, using the Water Pollution Index (WPI) and seasonal analysis. The analysis revealed elevated nitrite and orthophosphate concentrations at both stations, with Pančevo exhibiting extreme microbial contamination in 2015, attributed to urban runoff, agricultural activities, and inadequate wastewater treatment. Seasonal results indicate that while spring conditions align with Class I water standards, summer presents critical risks, especially at Pančevo, where the highest WPI value (26.47 in 2015) was recorded. Autumn shows stabilization, though sporadic WPI peaks reflect the impact of nutrient runoff. Winter conditions are marked by stability, with favorable dissolved oxygen levels but occasional exceedances in heavy metals, particularly at Jaša Tomić. Increased concentrations of suspended solids and heavy metals at Jaša Tomić emphasize diverse pollution sources, including industrial discharges and soil erosion. These findings underscore the necessity of integrated water management strategies, such as wastewater treatment upgrades and sustainable agricultural practices, to mitigate pollution. Protecting the Tamiš River is crucial for supporting biodiversity, safeguarding public health, and ensuring sustainable use of this vital Danube tributary.

1. Introduction

Water quality is a critical factor in assessing the sustainability of aquatic ecosystems and is essential not only for drinking water supply but also for tourism, transportation, and various other uses. Surface water quality is highly sensitive to both natural processes and human activities. Natural factors such as geological formations, soil types, climatic conditions, and hydrological characteristics inherently influence water quality parameters. However, anthropogenic activities—including urbanization, industrialization, mining, agriculture, and increased water consumption—significantly exacerbate the degradation of surface waters.

Numerous studies have documented the impact of the petrochemical industry on the quality and pollution of surface and groundwater, highlighting the release of nitrates, chlorides, sulphates and petroleum products into aquatic systems [1,2,3,4]. Agricultural practices, particularly intensive farming, contribute substantial amounts of nitrogen and phosphorus to water bodies through runoff, making agricultural nutrients a significant component of diffuse water pollution [5,6,7]. These factors often act as continuous pollution sources, severely degrading aquatic ecosystems and diminishing the usability of water for various activities.

Monitoring water quality and identifying sanitary risks are essential for protecting populations from waterborne diseases and developing appropriate preventive measures. Global water contamination poses a severe threat to public health, with the impact and seriousness of health issues depending on factors such as the chemical composition of contaminants, exposure duration, and pollutant concentration levels [8,9,10].

Water quality indices serve as valuable tools for assessing and communicating water quality status. Their primary purpose is to condense numerous physical, chemical, and biological measurements into a single value that reflects the ecological condition of a specific water body. These indices facilitate the comparison of water quality across different regions and time periods, forming the basis for extensive scientific research [11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29].

One such index, the Water Pollution Index (WPI), is employed to measure the extent of water pollution caused by various contaminants. The WPI helps in understanding the pollution load, identifying primary pollution sources, and assessing the effectiveness of pollution control measures. This index is applied in water pollution assessment worldwide: rivers in China [30]; Lake Ulansuhai in China [31]; Grenjeng River in Indonesia [32]; Nambul River in Manipur and groundwater in West Bengal in India [33,34]; Mekong River in Vietnam [35]. The WPI is also widely used in various studies in Serbia, including the Danube River in the Djerdap National Park and downstream until the Serbian–Romanian border [19,36]; the Sava River [37]; the Timok River [38]; the Porečka River [39]; the Hydro-system Danube–Tisa–Danube [40]; and Vlasina Lake [41].

The Tamiš River is a significant watercourse originating in the western part of Romania and flowing through the Banat region before joining the Danube near Pančevo in northern Serbia. The river holds substantial cultural and economic importance, supporting activities such as transportation, recreation, and tourism. However, its water quality faces challenges due to various pollution sources. In Romania, the Tamiš is polluted starting from Caransebeș due to wastewater discharges containing chlorides, fats, detergents, and petroleum products, as well as industrial activities and agricultural runoff [42]. In Serbia, previous assessments have indicated that pollutants enter the river through agricultural runoff and industrial and municipal sewage systems located along its course [43]. Besides this pollution, Lujić et al. [44] addressed inadequate maintenance of irrigation channels as well as effluents from fish and livestock farms as a main pollution sources.

In 2023, the establishment of a protected area within the Tamiš basin (Potamišje Region of Exceptional Characteristics) emphasized the ecological significance of the region. The designation of this area underscores the need for continuous monitoring and effective management of the river’s water quality to preserve its ecological integrity [45].

The Serbian section of the Tamiš River has not been subject to water quality research since 2009 [43]. This study aims to provide new insights into the water quality status of the Tamiš River in Serbia by calculating the Water Pollution Index (WPI) at two hydrological stations, namely Jaša Tomić and Pančevo, for the periods 2011–2015 and 2018–2022. Due to the cessation of operations at the Pančevo hydrological station in 2015, the WPI for this station was calculated only for the first period. By evaluating key physico-chemical parameters, this research aims to provide valuable insights into pollution levels, identify the main sources of contamination, and contribute to a comprehensive understanding of the river’s ecological status. The findings can contribute to future water management strategies and support efforts to protect and restore the Tamiš River basin.

2. Materials and Methods

2.1. Study Area

The Tamiš River, a tributary of the Danube in Serbia, originates in Romania under the highest peak of the Semenic Mountain. It flows for 340 km, of which 118 km is in Serbia, before joining the Danube near Pančevo. The river’s catchment area covers approximately 7319 km², with 1529 km² within Serbia [46].

Due to frequent meandering caused by the flat terrain and gentle river gradient, the Tamiš has a slow water flow, which historically led to significant flooding. To mitigate this, regulatory works began in the first half of the 18th century, cutting through numerous meanders to control flooding and improve navigation. Significant changes to the Tamiš water regime occurred in 1967 with the diversion of water from the Brzava River basin into the Danube and the construction of three sluice gates on the Tamiš River in Serbia [46].

The river exhibits its highest average monthly flows in March and April, while the lowest flows occur in September and October, which is characteristic of rivers with Central Europe’s rain–snow regime. The average annual flow of the Tamiš at Jaša Tomić is 39.1 m³/s [47].

A systematic analysis of river water quality was conducted at two hydrological stations (Figure 1): the Jaša Tomić hydrological station (UTM coordinates 5,031,950 m N and 7,489,150 m E, zone 34 N), and the Pančevo hydrological station (UTM coordinates 4,969,525 m N and 7,471,325 m E, zone 34 N) [48]. The Jaša Tomić Hydrological Station, located in northern Serbia near the border with Romania, primarily reflects pollution originating from upstream Romanian sources. Key contributors include industrial facilities, agricultural runoff, and urban wastewater. In contrast, the Pančevo Hydrological Station, situated near the confluence of the Tamiš with the Danube, integrates both upstream pollution from Romania and additional contributions from urban, industrial, and agricultural sources within Serbia (

Table 1. Anthropogenic pollution sources in Serbia.

Company	Facility	Location
Stary Tamiš D.O.O.	Nadel Farm	Pančevo, Serbia
HIP Petrohemija d.o.o. Pančevo	Petrochemical industry	Pančevo, Serbia
Timkok Proizvodno d.o.o.	Poultry Farm	Pančevo, Serbia
Higijena Javno komunalno preduzeće Pančevo	New landfill	Pančevo, Serbia
HIP Azotara DOO	Nitrogen fertilizer production	Pančevo, Serbia
Naftna Industrija Srbije a.d. Novi Sad	Oil refinery	Pančevo, Serbia
MASSAGRAR	Pig Farm	Sečanj, Serbia

Note: Source: SEPA [49].

).

This dual influence highlights the complexity of managing pollution in transboundary rivers like the Tamiš river.

Figure 1. Map of the study area. Source of data: [50].

Figure 1. Map of the study area. Source of data: [50].

The geographic distribution of these stations underscores the necessity for collaborative transboundary water management between Romania and Serbia. Effective measures require not only addressing local pollution sources but also implementing upstream interventions to mitigate the overall impact on the river’s ecological health.

An Integrated Polluters Cadastre of the Tamiš River was created as part of the “Eco-status of the Tamiš River” project, funded by the EU IPA funds under the Neighbourhood Programme Romania–Serbia. This project identified pollutants—including both natural and artificial substances—that disrupt the natural composition and properties of the environment when released into water, air, and soil. The concentrated pollution sources for the Tamiš River include industrial facilities, farms, public utility landfills, sewage discharges, and fishponds. Additionally, diffuse pollution sources encompass the use of artificial fertilizers and agrochemicals in agriculture, transportation (as diffuse sources), septic tanks, and forest resource utilization [51].

Water quality monitoring of the Tamiš River is of great importance, particularly due to the establishment of the Potamišje Region of Exceptional Characteristics. Covering 22,633.18 ha, this first-category natural asset of international, national, and exceptional significance boasts a unique mosaic of ecosystems, including alluvial forests, wet meadows and pastures, ancient river sections, marshes, and both mesophilic and saline meadows. It is celebrated for its rich biodiversity, being a hotspot with 606 taxa of higher plants, 42 species of fish, 11 species of amphibians, 9 species of reptiles, 49 species of invertebrates of national and international importance, 257 species of birds, and 58 species of mammals. Additionally, it encompasses two internationally significant bird areas (Important Bird Areas—IBA) and an internationally significant plant area (Important Plant Area—IPA). The created values of this area are no less important. There are 17 villages evenly distributed around the perimeter of the protected area. All are known for their traditional use of resources, indigenous culture, and preserved rural architecture [52]. The protected area holds immense value not only for the local community and, also, for the broader scientific community, offering a unique opportunity to study ecological processes and interactions within preserved natural habitats.

2.2. Data and Methods

This study systematically evaluated river water quality at the Jaša Tomić and Pančevo hydrological stations. The river water quality data were analyzed for two separate periods, 2011–2015 and 2018–2022, from the Serbian Environmental Protection Agency [49]. The dataset for Pančevo was available only for the period 2011–2015 due to the cessation of station operation in 2015.

The water quality evaluation included key physico-chemical parameters, namely dissolved oxygen (DO), oxygen saturation (OS), pH, suspended solids (SS), biochemical oxygen demand (BOD), chemical oxygen demand (COD_Mn), nitrites (NO₂⁻), ammonium (NH₄⁺), orthophosphates (PO₄³⁻), sulphates (SO₄²⁻), dissolved metals (Fe, Mn, Ni, Hg Cu, Pb, Cd), and total coliforms (TC).

Based on water sampling, the Serbian Environmental Protection Agency (SEPA), under the Ministry of Environmental Protection of the Republic of Serbia, applied the following methods for these analyses: SRPS ISO 5813:1994 (for dissolved oxygen); SRPS H.Z1.160:1987 (for oxygen saturation); SRPS H.Z1.111:1987 (for pH); SRPS H.Z1.160:1987 (for suspended solids); BOD JUS ISO 5815 (for biochemical oxygen demand). determination using potassium permanganate: Kubel–Tiemann method (for chemical oxygen demand); HACH Method 8507—EPA 353.2 (for nitrites); HACH Method 8155 (for ammonium); HACH Method 8048—EPA 365.1 (for orthophosphates); HACH Method 8051 (for sulphates); EPA 6020 A:2014 (for Fe, Mn, Ni, Cu, and Cd); EPA 6020 A:2007 (for Pb); EPA Method 245.7 (for Hg); SRPS EN ISO 9308-1:2010 (for total coliforms) [49].

2.3. Water Pollution Index (WPI)

The water pollution index (WPI) was calculated to quantify water quality status based on measured parameters. WPI is defined as the sum of ratios between observed parameter values and corresponding standard limits:

$$\mathrm{WPI}={\sum }_{i=1}^n{\displaystyle \frac{Ci}{SFQS}}·{\displaystyle \frac{1}{n}}$$

In this formula, Ci represents the average annual concentration of the analyzed parameters based on river water quality data [53]. SFQS denotes the standard values (

Table 2. Parameter standard values for Class I.

Parameter	Unit	Class I
Dissolved Oxygen (DO)	mg/L	8.5
Oxygen Saturation (OS)	%	90
pH		6.5–8.5
Suspended solids (SS)	mg/L	25
Biochemical Oxygen Demand (BOD)	mg/L	2
Chemical Oxygen Demand (CODMn)	mg/L	10
Nitrites (NO2−),	mg/L	0.01
Ammonium (NH4+)	mg/L	0.1
Orthophosphates (PO43−)	mg/L	0.02
Sulphates (SO42−)	mg/L	50
Iron (Fe)	mg/L	0.3
Manganese (Mn)	mg/L	0.05
Nickel (Ni)	µg/L	20
Mercury (Hg)	µg/L	1
Copper (Cu)	µg/L	2000
Lead (Pb)	µg/L	50
Cadmium (Cd)	µg/L	5
Total Coliforms (TC)	CFU/100 mL	500

Note: Source: [54,55,56,57].

) for the first class of water quality in Serbia, while n presents the total number of analyzed parameters. In Serbia, the SFQS values correspond to Class I of surface water according to national legislation [54,55,56,57]. Water quality Class I could be used for drinking (after appropriate filtration and disinfection), recreation, irrigation, and various industrial uses.

Classification of water quality status based on WPI values is presented in

Table 3. Classification of surface water using the WPI.

Class	Characteristics	WPI
I	Very pure	≤0.3
II	Pure	0.3–1
III	Moderately polluted	1–2
IV	Polluted	2–4
V	Impure	4–6
VI	Heavily impure	>6

Note: Source: [53].

, following Lyulko et al. [53].

One of the advantages of the WPI is its flexibility to incorporate various parameters. It is not restricted by the quantity or types of parameters utilized.

Understanding the deviations from class I water quality standards contributes to the identification of pollution levels and sources affecting the river ecosystem. By analyzing the ratio of mean annual concentrations, the parameters that exceed the acceptable limits are addressed, providing a comprehensive assessment of the river’s water quality over the studied periods.

3. Results and Discussion

3.1. Parameters Deviation from Class I

Table 4. Ratio of mean annual concentration and standards of the Class I of water quality for analyzed parameters.

Pančevo
Year	DO	OS	pH	SS	BOD	CODMn	NO2−	NH4+	PO43−	SO42−	Fe	Mn	Ni	Hg	Cu	Pb	Cd	TC
2011	1.138	0.943	0.929	0.732	0.895	0.48	1.9	1.33	5.3	1.326	0.347	0.6	0.168	0.1	0.002	0.01	0.005	21.067
2012	1.175	1.022	0.941	0.648	0.885	0.488	1.7	0.8	4.1	0.72	0.17	0.28	0.511	0.1	0.002	0.01	0.004	6.3
2013	1.15	0.959	0.929	0.604	0.82	0.53	1.8	1.18	4.9	0.748								1.34
2014	1.013	0.891	0.929	1.128	0.845	0.605	1.6	1.25	4.35	0.75	0.353	0.56	0.511	0.1	0.005	0.014	0.006	39.8
2015	1.125	0.942	0.929	1.3	1.055	0.513	1.8	1.14	3.8	0.948	0.29	0.48	0.171	0.1	0.003	0.014	0.006	149.5
Jaša Tomić
Year	DO	OS	pH	SS	BOD	CODMn	NO2−	NH4+	PO43−	SO42−	Fe	Mn	Ni	Hg	Cu	Pb	Cd	TC
2011	2.088	1.022	0.929	1.456	0.922	0.41	1.3	0.84	1.95	1.062	0.247	1.68	0.59	0.046	0.002	0.01	0.005	2.096
2012	1.175	1.03	0.918	1.064	0.841	0.36	1.6	2.8	1.15	1.442	0.177	0.82	0.26	0.114	0.001	0.01	0.004	0.25
2013	1.254	1.071	0.926	1.953	0.795	0.456	1.7	1.1	2.35	0.757								7.55
2014	1.203	1.011	0.935	2.107	0.763	0.575	1.4	0.6	2.5	0.715	0.41	0.64	0.495	0.1	0.004	0.013	0.005	13.333
2015	1.188	1.036	0.941	1.272	0.704	0.415	1.5	0.69	1.75	0.884	0.28	0.42	0.206	0.1	0.002	0.014	0.005	3.69
2018	1.2	1.009	0.918	1.852	0.625	0.498	1.6	0.89	1.7	0.845	2	1	0.26	0.07	0.007	0.015	0.005	1.823
2019	1.200	0.912	0.906	0.828	0.692	0.449	1.3	1.25	1.85	1.035	0.697	1.14	1.745	0.07	0.01	0.016	0.005	1.488
2020	1.225	1.028	0.918	0.808	0.823	0.328	1.9	1.9	1	0.855	0.613	0.82	0.494	0.07	0.003	0.014	0.005	1.84
2021	1.249	1.061	0.908	1.252	0.775	0.435	1	0.4	1	0.953	0.183	0.48	0.246	0.07	0.003	0.01	0.015	3.895
2022	1.231	1.025	0.902	1.340	0.84	0.498	2	2	1	0.8	0.367	0.8	0.34	0.07	0.005	0.013	0.022	1.584

presents the deviations from Class I Water Quality Standards at the Pančevo hydrological station for the period 2011–2015 and at the Jaša Tomić hydrological station for the periods 2011–2016 and 2018–2022. It should be noted that, due to the cessation of data collection at the Pančevo station in 2015, the results for this location cover only the first period. Additionally, dissolved metal measurements were unavailable or incomplete for certain years, thus excluded from parts of the analysis.

The results at the Pančevo hydrological station for the period 2011–2015 show that the dissolved oxygen (DO) ratios ranged from 1.013 to 1.175. The dissolved oxygen ratios at the Jaša Tomić hydrological station ranged from 1.175 to 1.355, relative to the Class I standard. These increased levels indicate supersaturation in the water, which is generally not harmful to the water quality or to aquatic organisms.

The oxygen saturation (OS) ratios ranged from 0.891 to 1.022 at the Pančevo hydrological station and from 0.912 to 1.071 at the Jaša Tomić hydrological station, indicating that oxygen levels fluctuated near optimal conditions. Although slightly lower oxygen saturation values were observed occasionally, they remained close to the optimal range.

The pH ratios were consistently between 0.929 and 0.941 at the Pančevo hydrological station and between 0.902 and 0.941 at the Jaša Tomić hydrological station throughout the examined years, indicating that the water acidity levels remained stable and well within the Class I water quality standards. This stability suggests a balanced aquatic environment without significant acidic or alkaline fluctuations, which is essential for the health of diverse aquatic species.

Suspended solids (SS) ratios at the Pančevo hydrological station varied between 0.604 and 1.300, with exceedances in 2014 (1.128) and 2015 (1.300). The increased levels may have reduced water clarity, affecting photosynthesis by limiting light penetration and potentially degrading habitat quality for aquatic organisms by smothering benthic habitats [58]. Similarly, SS ratios at the Jaša Tomić hydrological station varied between 0.808 and 2.107, with notable deviations in 2013 (1.953), 2014 (2.107), and 2018 (1.852), which likely resulted from increased soil erosion, runoff, or anthropogenic activities upstream.

The ratios for biological oxygen demand (BOD) ranged from 0.820 to 1.055 at the Pančevo hydrological station. A slight increase was observed in 2015, when the ratio peaked at 1.055, slightly surpassing the Class I standard. This increase indicates that the amount of biodegradable organic matter in the water was occasionally high enough to cause minor oxygen depletion. BOD ratios at the Jaša Tomić hydrological station ranged from 0.625 to 0.922, remaining within the Class I water quality standards throughout the studied periods, indicating no significant risk of oxygen depletion.

Chemical oxygen demand (COD_Mn) values ranged from 0.800 to 1.300 at the Pančevo hydrological station, with some years surpassing the Class I thresholds. Elevated COD_Mn levels indicate the presence of oxidizable organic and inorganic substances, indicating potential sources such as industrial effluents or urban runoff. The COD_Mn ratios were between 0.328 and 0.575 at the Jaša Tomić hydrological station, remaining within the Class I standards. This indicates that the levels of oxidizable compounds were low and chemical pollutants were not a significant concern during the analyzed period.

Nitrite (NO₂⁻) ratios were consistently high, ranging from 1.600 to 1.900 at the Pančevo hydrological station and from 1.000 to 2.000 at the Jaša Tomić hydrological station, significantly exceeding the Class I standards throughout the studied period. These elevated nitrite levels signal substantial nitrogen pollution, raising concerns since nitrites can be toxic to aquatic life even at low concentrations. The likely sources include agricultural runoff rich in fertilizers and inadequate sewage treatment [59], emphasizing the need for improved nutrient management in the region. According to the Ministry of Agriculture, Forestry and Water Management of the Republic of Serbia [60], there is currently no organized collection of data on pesticide use, nor an appropriate database that records the quantities of chemical agents used on different crops. Water bodies at significant potential risk of pesticide pollution are predominantly located in Vojvodina, northern Serbia. Therefore, further research and improvements in monitoring and analysis regarding the chemical use are necessary to accurately assess the actual impact from hazardous substances from agriculture.

Ammonium (NH₄⁺) ratios fluctuated between 0.890 and 1.330 at the Pančevo hydrological station. Notably, in 2011 (1.330), 2013 (1.180), 2014 (1.250), and 2015 (1.140), the ratios exceeded the Class I standard. At the Jaša Tomić hydrological station, ammonium ratios varied between 0.400 and 2.800, with significant deviations recorded in 2012 (2.800) and 2022 (2.000). Increased ammonium concentrations can be detrimental, as ammonium is toxic to fish and invertebrates at higher levels, affecting their growth, reproduction, and survival. These findings highlight potential issues with wastewater discharge and agricultural practices leading to ammonia pollution [61]. Decomposition of organic matter could also cause increased ammonium concentrations.

Orthophosphate (PO₄³⁻) ratios were significantly above the Class I standards during the entire period, ranging from 3.800 to 5.300 at the Pančevo hydrological station and from 1.000 to 2.500 at the Jaša Tomić hydrological station. Such high concentrations indicate considerable phosphorus pollution, likely from agricultural fertilizers, detergents, and sewage effluent. According to Biliani et al. [62] increased orthophosphates promote excessive algal growth, leading to eutrophication, which degrades water quality by causing oxygen depletion and harming aquatic life.

Sulphate (SO₄²⁻) ratios were mostly within standards, except in 2011 at the Pančevo hydrological station, when the ratio peaked at 1.326, surpassing the Class I limit. This peak suggests a possible influx of sulphate-rich effluents during that year, necessitating investigation into industrial discharges, agricultural runoff, or natural sources. Sulphate ratios ranged from 0.715 to 1.442 at the Jaša Tomić hydrological station, with a deviation in 2012 (1.442) exceeding the standard.

The analysis of metal concentrations at the Pančevo hydrological station from 2011 to 2015 reveals that metal pollution was not a significant concern during this period, with all measured metals remaining within Class I water quality standards. However, the absence of data for 2013 underscores the need for continuous monitoring. Slight increases in certain metals, such as nickel, lead, and cadmium, highlight the importance of ongoing attention to maintain the river’s health and prevent future contamination. At the Jaša Tomić hydrological station, notable deviations from Class I standards were recorded for dissolved metals. Iron (Fe) ratios ranged from 0.177 to 2.000, with a notable deviation in 2018 (2.000) exceeding the Class I standard. Possible sources include natural geological leaching, industrial discharges, or mining activities upstream. Manganese (Mn) ratios were between 0.420 and 1.680, with deviations in 2011 (1.680) exceeding the standards. Nickel (Ni) ratios were notably elevated in 2019 (1.745), exceeding the class I standard. The elevated levels indicate possible industrial influence or contamination from urban runoff.

Total coliform (TC) ratios at the Pančevo hydrological station ranged from 1.340 to an alarming 149,500 in 2015. The mean annual concentration of total coliforms in 2015 was 747,500 CFU/100 mL vastly exceeding Class I standards. This substantial increase indicates severe fecal contamination, posing significant health risks for human contact and signaling potential outbreaks of pathogenic organisms. Contamination can stem from untreated sewage discharge, septic system failures, or runoff from livestock areas. The extraordinarily high level of coliforms necessitates urgent attention and remediation efforts. Total coliform ratios at the Jaša Tomić hydrological station varied from 0.250 to 13.333, with elevated levels in 2014 (13.333) and 2021 (3.895) exceeding the Class I standards.

The data from the Pančevo Hydrological Station between 2011 and 2015 highlight several concerning deviations from Class I water quality standards. Parameters such as nitrites, ammonium, orthophosphates, suspended solids, BOD, sulphates, and total coliforms exceeded acceptable levels in various years, suggesting significant pollution from agricultural runoff, inadequate wastewater treatment, and possibly industrial activities.

Based on the comparative analysis of the results from both hydrological stations, we can conclude that both stations exhibited high levels of nitrites and orthophosphates, with Pančevo showing higher concentrations of orthophosphates. Pančevo also displayed significantly higher levels of total coliforms, particularly in 2015. Regarding heavy metals, Jaša Tomić exhibited significant deviations in iron, manganese, and nickel. Analyses have shown that Pančevo had fewer deviations concerning heavy metals. Suspended solids were higher at the Jaša Tomić station, indicating upstream erosion or construction activities.

The data reveal that both hydrological stations deviate from Class I water quality standards, albeit with different predominant pollutants. Pančevo exhibited elevated nutrients and microbial pollution with likely sources including urban runoff, inadequate wastewater treatment, and agricultural activities. Agriculture land use includes poultry and pig farms, cultivation of cereals, legumes, and oilseeds. Besides agriculture, industrial activities (petrochemical industry, oil refinery, nitrogen fertilizer production) also contribute to water quality impairment. Regional landfill also affects water quality [49]. Jaša Tomić had elevated levels of suspended solids, heavy metals, and nutrients. Probable sources are soil erosion, industrial discharges, and agricultural practices.

3.2. Seasonal Analysis

By comparing seasonal data to Class I water quality standards, the analysis highlights temporal fluctuations influenced by natural and anthropogenic factors. Spring was analyzed based on the mean values of parameters measured in March, April, and May; summer as the mean of June, July, and August; autumn as the mean of September, October, and November; and winter as the mean of December, January, and February. These seasonal analyses provide insights into temporal variations across spring, summer, autumn, and winter, offering a detailed evaluation of how water quality fluctuates throughout the year in relation to regulatory standards. By analyzing the ratio of mean annual and seasonal concentrations, the parameters that exceed the acceptable limits are addressed, providing a comprehensive assessment of the river’s water quality over the studied periods. Understanding seasonal dynamics is crucial for water resource management, as it reveals patterns that inform mitigation strategies and environmental protection measures.

During the spring, water quality at both Jaša Tomić and Pančevo stations generally aligns with Class I standards, with minor seasonal fluctuations. Dissolved oxygen levels at the Jaša Tomić hydrological station consistently exceed thresholds (greater than 1.10), driven by increased photosynthesis and algal activity. The pH remains neutral, reflecting balanced aquatic systems, while suspended solids exhibit moderate variability linked to spring runoff and sediment transport. Nutrient concentrations, such as nitrites, ammonium, and orthophosphates, show slight increases due to agricultural runoff but remain within the acceptable limits. Overall, spring highlights balanced conditions at both stations, with minimal anthropogenic impacts (

Table 5. Ratio of seasonal mean concentration and standards of the Class I of water quality for analyzed parameters (Spring).

Pančevo
Year	DO	OS	pH	SS	BOD	CODMn	NO2−	NH4+	PO43−	SO42−	Fe	Mn	Ni	Hg	Cu	Pb	Cd	TC
2011	0.963	0.926	0.933	0.906	0.734	0.463	2.5	0.77	6.15	1.313	0.200	1.00	0.255	0.100	0.001	0.010	0.005	7.600
2012	0.996	0.944	0.918	1.346	0.784	0.577	2.3	1.00	3.35	0.467	0.253	0.28	0.062	0.100	0.001	0.010	0.004
2013	0.958	0.796	0.909	0.613	1.015	0.727	1.9	0.87	5.50	0.653								1.000
2014	1.208	1.100	0.953	0.800	1.217	0.427	1.7	1.73	3.50	0.827	0.143	0.58	0.110	0.100	0.003	0.013	0.005	20.000
2015	1.171	0.967	0.941	0.960	0.950	0.460	2.0	0.90	3.50	1.040	0.267	0.40	0.209	0.100	0.002	0.017	0.006	24.000
Jaša Tomić
Year	DO	OS	pH	SS	BOD	CODMn	NO2−	NH4+	PO43−	SO42−	Fe	Mn	Ni	Hg	Cu	Pb	Cd	TC
2011	3.450	1.041	0.929	1.373	1.067	0.420	1.2	0.53	3.50	0.780	0.167	1.00	1.500	0.055	0.002	0.010	0.005	1.000
2012	1.213	1.041	0.906	1.933	0.700	0.470	1.6	0.80	1.60	0.640	0.190	0.44	0.075	0.100	0.001	0.010	0.004
2013	1.204	1.081	0.902	5.240	0.917	0.717	1.4	0.93	2.90	0.673								8.200
2014	1.263	1.081	0.953	1.386	0.665	0.480	0.8	0.53	1.50	0.880	0.370	0.94	0.152	0.100	0.002	0.016	0.004	2.000
2015	1.125	0.967	0.954	0.573	0.634	0.350	1.2	0.30	2.10	0.827	0.220	0.32	0.194	0.100	0.002	0.017	0.006	0.700
2018	1.171	1.015	0.918	2.813	0.634	0.593	1.2	0.40	1.95	0.367	4.110	0.66	0.150	0.070	0.010	0.021	0.006	4.200
2019	1.263	1.037	0.912	0.560	0.434	0.373	1.5	0.53	0.95	0.427	0.403	0.60	1.102	0.070	0.013	0.010	0.005	1.600
2020	1.138	1.026	0.904	0.653	0.517	0.303	2.2	0.33	1.00	0.627	0.660	0.60	0.592	0.070	0.003	0.018	0.006
2021	1.329	1.059	0.908	2.253	0.965	0.600	1.0	0.50	1.00	0.647	0.200	0.40	0.103	0.070	0.002	0.010	0.004	0.460
2022	1.329	1.048	0.898	1.573	0.667	0.343	1.4	0.33	0.90	0.700	0.583	0.58	0.001	0.070	0.009	0.017	0.040	2.400

).

Summer introduces notable changes at both stations, with elevated temperatures and intensified biological activity. Dissolved oxygen levels decline at both Jaša Tomić and Pančevo hydrological stations, with ratios slightly below Class I thresholds (for example, ranging from 0.67 to 0.92 at Pančevo). Nutrient levels, especially nitrates and phosphates, increase, reflecting eutrophication risks. At Pančevo, orthophosphates reach consistently high ratios, from 4.95 to 6.05. Manganese concentrations also rise, exceeding regulatory thresholds at Pančevo (up to 1.96 in 2015). Despite increased pressures, key parameters like suspended solids and organic pollutants remain relatively stable at both stations. Summer conditions emphasize the need for careful monitoring of nutrients and metals (

Table 6. Ratio of seasonal mean concentration and standards of the Class I of water quality for analyzed parameters (Summer).

Pančevo
Year	DO	OS	pH	SS	BOD	CODMn	NO2−	NH4+	PO43−	SO42−	Fe	Mn	Ni	Hg	Cu	Pb	Cd	TC
2011	0.891	0.907	0.926	0.800	0.700	0.437	1.5	0.73	4.95	0.774	0.300	0.40	0.098	0.100	0.004	0.010	0.005	27.8
2012	0.900	1.011	0.927	0.546	0.700	0.370	1.2	0.53	5.45	0.693	0.194	0.29	0.065	0.100	0.003	0.010	0.004
2013	0.921	0.985	0.906	0.506	0.734	0.510	1.4	0.47	5.65	0.913								0.58
2014	0.671	0.693	0.914	1.853	0.734	0.927	1.9	0.83	6.05	0.607	0.573	0.44	1.064	0.100	0.007	0.017	0.006	9.6
2015	0.766	0.874	0.931	1.227	1.415	0.563	1.0	0.60	5.00	1.007	0.683	1.96	0.295	0.100	0.004	0.010	0.014	460
Jaša Tomić
Year	DO	OS	pH	SS	BOD	CODMn	NO2−	NH4+	PO43−	SO42−	Fe	Mn	Ni	Hg	Cu	Pb	Cd	TC
2011	1.254	0.967	0.945	1.213	0.900	0.473	1.5	0.60	0.90	1.313	0.167	1.00	0.215	0.010	0.002	0.010	0.006	0.44
2012	1.000	1.107	0.929	0.826	0.984	0.370	0.4	0.40	1.30	1.333	0.150	0.70	0.608	0.150	0.002	0.010	0.004	0.4
2013	1.017	1.133	0.968	0.200	0.780	0.320	1.3	0.27	3.85	1.093								2.4
2014	0.925	0.952	0.933	2.733	0.867	0.623	1.6	0.70	3.25	0.667	0.583	0.42	0.475	0.100	0.004	0.011	0.005	4
2015	0.966	1.081	0.962	0.586	0.615	0.353	1.0	0.33	1.70	0.847	0.227	0.72	0.282	0.100	0.003	0.013	0.005	11
2018	0.888	0.951	0.907	1.600	0.584	0.493	1.7	0.67	2.50	0.760	2.443	1.10	0.360	0.070	0.005	0.016	0.005	4.
2019	0.863	0.896	0.842	1.200	0.934	0.730	1.1	1.13	3.65	0.600	0.407	2.36	1.600	0.070	0.008	0.011	0.006	4.4
2020	0.950	1.000	0.921	1.480	1.134	0.397	1.5	0.37	1.05	1.047	0.493	0.82	0.977	0.070	0.003	0.014	0.005	2.6
2021	1.029	1.122	0.906	0.360	0.817	0.337	1.8	0.23	1.45	0.847	0.153	0.62	0.189	0.070	0.001	0.010	0.004	0.56
2022	0.929	1.011	0.898	1.147	0.867	0.513	1.6	3.37	1.55	0.660	0.407	0.72	0.448	0.070	0.002	0.012	0.013	1.373

).

In autumn, water quality stabilizes at both stations as temperatures drop. Dissolved oxygen ratios improve at the Jaša Tomić (approximately 1.30) and Pančevo hydrological stations (ranging from 1.17 to 1.44), reflecting cooler conditions and reduced biological activity. Nutrient levels, particularly ammonium and orthophosphates, show increases due to organic matter degradation and runoff, with Pančevo exhibiting peaks (ammonium reaching 2.10 and orthophosphates reaching 4.3). Despite localized risks, autumn represents a transitional phase with overall improvements compared to summer (

Table 7. Ratio of seasonal mean concentration and standards of the Class I of water quality for analyzed parameters (Autumn).

Pančevo
Year	DO	OS	pH	SS	BOD	CODMn	NO2−	NH4+	PO43−	SO42−	Fe	Mn	Ni	Hg	Cu	Pb	Cd	TC
2011	1.438	1.050	0.959	0.360	1.100	0.460	1.8	1.10	4.30	1.410	0.333	0.40	0.110	0.10	0.002	0.010	0.004
2012	1.338	1.044	0.955	0.293	0.800	0.440	1.5	0.83	4.00	0.720	0.033	0.30	0.083	0.10	0.002	0.010	0.004	0.6
2013	1.171	0.952	0.949	0.747	0.617	0.513	1.8	1.77	4.25	0.680								3.2
2014	0.916	0.804	0.902	0.586	0.700	0.557	1.3	1.50	4.25	0.727	0.323	0.64	0.354	0.10	0.005	0.013	0.005	120
2015	1.063	0.926	0.939	0.640	0.850	0.410	3.0	2.10	4.00	0.847	0.100	0.40	0.129	0.10	0.002	0.010	0.004	57
Jaša Tomić
Year	DO	OS	pH	SS	BOD	CODMn	NO2−	NH4+	PO43−	SO42−	Fe	Mn	Ni	Hg	Cu	Pb	Cd	TC
2011	1.538	1.111	0.929	0.480	0.800	0.270	2.0	0.70	0.40	2.280	0.133	5.00	0.485	0.010	0.001	0.010	0.004	0.44
2012	1.091	0.981	0.948	0.772	0.665	0.290	2.9	1.20	0.80	2.346	0.047	0.82	0.143	0.100	0.001	0.010	0.004	0.1
2013	1.191	1.026	0.901	0.760	0.800	0.353	1.9	1.07	0.85	0.787								8.333
2014	1.138	0.978	0.911	3.680	0.784	0.860	1.6	0.50	3.25	0.553	0.433	0.46	0.919	0.100	0.007	0.012	0.008	29
2015	1.241	1.059	0.954	0.293	0.650	0.323	2.0	0.87	0.95	1.040	0.183	0.34	0.195	0.100	0.001	0.010	0.004	0.26
2018	1.200	1.041	0.927	0.480	0.717	0.297	1.9	0.53	1.15	1.373	0.187	0.88	0.292	0.070	0.005	0.010	0.004	0.58
2019	1.154	0.993	0.938	0.266	0.634	0.293	1.0	0.33	0.70	2.047	0.163	0.76	3.838	0.070	0.010	0.031	0.004	0.32
2020	1.295	1.011	0.906	0.413	0.517	0.247	1.7	1.80	1.35	0.793	0.590	0.68	0.108	0.070	0.002	0.010	0.004	0.62
2021	1.179	1.030	0.919	0.373	0.500	0.263	0.6	0.30	0.55	1.327	0.053	0.32	0.354	0.070	0.005	0.010	0.042
2022	1.196	1.022	0.926	1.386	0.800	0.413	1.6	1.00	1.10	0.893	0.240	0.50	0.083	0.070	0.003	0.010	0.004	1.4

).

Winter brings stability to water quality at both stations. Dissolved oxygen ratios remain favorable, with both the Jaša Tomić (ranging from 1.42 to 1.66) and Pančevo hydrological stations (ranging from 1.38 to 1.64) showing sufficient aeration under low temperatures. Ammonium concentrations increase significantly at Pančevo (peaks of up to 3.30 in 2011), reflecting slower degradation rates. Heavy metals, including manganese, occasionally approach or exceed standards. The pH values and suspended solids remain stable, supporting balanced aquatic ecosystems. It is noteworthy that total coliform bacteria were not analyzed in winter (

Table 8. Ratio of seasonal mean concentration and standards of the Class I of water quality for analyzed parameters (Winter).

Pančevo
Year	DO	OS	pH	SS	BOD	CODMn	NO2−	NH4+	PO43−	SO42−	Fe	Mn	Ni	Hg	Cu	Pb	Cd	TC
2011	1.450	0.917	0.918	0.780	1.225	0.590	1.9	3.30	5.55	2.090	0.60	0.80	0.280	0.100	0.002	0.010	0.005
2012	1.638	1.122	0.947	0.280	1.450	0.605	2.0	1.35	3.40	1.140
2013	1.566	1.100	0.948	0.520	0.915	0.376	2.0	1.60	4.25	0.746
2014	1.381	1.006	0.927	1.560	0.675	0.465	1.7	0.80	3.28	0.890	0.39	0.55	0.318	0.100	0.005	0.015	0.006
2015	1.483	1.000	0.905	2.373	1.000	0.620	1.1	0.90	2.65	0.900	0.43	0.20	0.118	0.100	0.003	0.020	0.006
Jaša Tomić
Year	DO	OS	pH	SS	BOD	CODMn	NO2−	NH4+	PO43−	SO42−	Fe	Mn	Ni	Hg	Cu	Pb	Cd	TC
2011	1.581	1.044	0.918	3.400	0.800	0.330	0.9	1.75	1.95	0.500	0.600	0.40	0.160	0.100		0.012	0.005	7.6
2012	1.538	0.972	0.865	0.560	1.100	0.285	1.7	11.85	0.60	1.450	0.453	1.86	0.170	0.100	0.001	0.010	0.004
2013	1.604	1.044	0.929	1.613	0.684	0.433	2.0	2.13	1.75	0.473								11.2
2014	1.484	1.033	0.944	0.626	0.734	0.337	1.8	0.80	1.10	0.760	0.263	0.68	0.383	0.100	0.003	0.010	0.004	12
2015	1.421	1.033	0.914	3.640	0.915	0.633	1.9	1.27	2.20	0.820	0.487	0.32	0.154	0.100	0.001	0.017	0.005	2.8
2018	1.538	1.030	0.900	2.508	0.565	0.610	1.5	1.97	1.15	0.880	0.880	1.60	0.228	0.070	0.007	0.012	0.006	1
2019	1.500	1.000	0.899	1.280	0.765	0.400	1.7	3.00	2.10	1.067	1.800	0.84	0.438	0.070	0.008	0.013	0.005	0.8
2020	1.656	1.094	0.920	0.620	1.275	0.385	2.2	6.70	0.65	1.000	0.763	1.37	0.200	0.070	0.003	0.012	0.004	3.4
2021	1.563	1.017	0.894	2.400	0.825	0.595	1.0	0.70	2.25	1.010	0.403	0.49	0.228	0.070	0.005	0.010	0.004	14
2022	1.470	0.973	0.888	1.252	1.015	0.723	1.6	3.33	1.10	0.947	0.290	1.14	0.393	0.070	0.004	0.013	0.029

).

3.3. Water Pollution Index (WPI) Analysis

Table 9. Mean annual WPI values and water quality classifications at the analyzed hydrological stations.

Hydrological Station	2011	2012	2013	2014	2015	2018	2019	2020	2021	2022
Pančevo	2.1	1.1	1.4	3	9.1	-	-	-	-	-
	IV	III	III	IV	VI
Jaša Tomić	0.93	0.78	1.81	1.49	0.83	0.91	0.87	0.81	0.77	0.82
	II	II	III	III	II	II	II	II	II	II

Note: “-” indicates data not available due to the cessation of monitoring.

shows the WPI values for the analyzed hydrological stations. According to these values, water quality at the Jaša Tomić hydrological station shows slight variations in WPI classes. Most years were rated as Class II, indicating moderate pollution, while a few years shifted to Class III, indicating an increase in pollution. Overall, pollution remained moderate throughout the analyzed period.

Notably, at the Pančevo hydrological station, the highest WPI class (Class VI) was recorded in 2015, indicating extremely high pollution. During the other years (2011–2014), the WPI classes varied between Class III and Class IV, indicating changes in pollution levels. The extremely high pollution level in 2015 highlights the urgent need for targeted remediation efforts.

The data clearly indicate higher pollution levels at the Pančevo station, notably due to extremely elevated total coliforms, nutrients, and organic pollutants. However, analyzing long-term pollution trends at this station is complicated because of the cessation of monitoring after 2015, which emphasizes the necessity for renewed monitoring.

The stabilization of water quality from 2015 to 2022 at the Jaša Tomić hydrological station indicates that pollution control measures may have been effective. This improvement could be attributed to better agricultural practices, improved wastewater management, or decreased industrial discharges upstream.

Previous studies of nearby rivers have obtained similar WPI results. The WPI values for the Danube River showed similar trends: the Danube River had moderate to high pollution (Class II–III), with a mean WPI of 0.84 (Class II) in 2014 at the Pančevo area, while the Karaš River showed a relatively lower pollution level (Class II, WPI = 0.75) in 2019 [63,64]. These comparisons highlight that pollution in the Tamiš River aligns with broader regional trends, underscoring the importance of integrated water resource management across the region.

The Water Pollution Index (WPI) was also calculated for each season, providing a comprehensive overview of ecological conditions. The seasonal analysis of the Water Pollution Index (WPI) at the Jaša Tomić hydrological station reveals distinct patterns. During spring, WPI values generally fall into Class II (pure) or Class III (moderately polluted), reflecting balanced ecological conditions with occasional spikes in pollution. In summer, WPI values often reach the upper range of Class III or even the lower limits of Class IV (polluted), driven by increased biological activity and nutrient enrichment due to elevated temperatures. Autumn exhibits stabilization, with WPI values predominantly within Class III, though sporadic peaks at the threshold of Class IV highlight nutrient runoff from seasonal rains. Winter, however, records elevated WPI values, frequently near or within Class IV, attributed to reduced water flow and sediment interactions, signaling a need for careful observation during this period. Detailed seasonal WPI values for Jaša Tomić hydrological station are presented in

Table 10. Seasonal WPI Values and Water Classifications at Jaša Tomić hydrological station.

Jaša Tomić	2011	2012	2013	2014	2015	2018	2019	2020	2021	2022
Spring	1.00	0.69	2.20	0.73	0.59	1.13	0.65	0.63	0.64	0.72
Class	II	II	IV	II	II	III	II	II	II	II
Summer	0.66	0.59	1.21	1.05	1.16	1.06	1.16	0.82	0.58	0.87
Class	II	II	III	III	III	III	III	II	II	II
Autumn	0.92	0.73	1.63	2.51	0.58	0.65	0.75	0.67	0.46	0.7
Class	II	II	III	IV	II	II	II	II	II	II
Winter	1.30	1.38	2.17	1.28	1.03	0.91	0.98	1.24	1.53	0.90
Class	II	III	IV	III	III	II	II	III	III	II

.

The seasonal analysis of the Water Pollution Index (WPI) at the Pančevo hydrological station shows clear seasonal fluctuations (

Table 11. Seasonal WPI Values and Water Classifications at the Pančevo hydrological station.

Pančevo	2011	2012	2013	2014	2015
Spring	1.38	0.79	1.36	1.91	2.1
Class	III	II	III	III	IV
Summer	2.3	0.76	1.23	1.5	26.47
Class	IV	II	III	III	VI
Autumn	0.88	0.73	1.51	7.43	4.03
Class	II	II	III	VI	VI
Winter	1.21	1.39	1.4	0.82	0.81
Class	III	III	III	II	II

). In spring, WPI values predominantly fall within Class III (moderately polluted), indicating moderate ecological balance with occasional stress. Notably, 2015 recorded a Class IV (polluted) level, reflecting increased seasonal runoff and sediment transport. In summer, values display significant variability, ranging from Class III to as high as Class VI (severely polluted) in 2015, driven by intensified biological activity, nutrient enrichment, and elevated temperatures. The extreme WPI value of 26.47 recorded in 2015, due to high total coliform concentrations (measured in n/L), is also summarized in Table 11. In autumn, a stabilization is observed, with most WPI values in Class III; however, sporadic peaks, such as the Class VI levels in 2014 and 2015, indicate nutrient runoff exacerbated by seasonal rainfall. Winter highlights relatively stable conditions, with WPI values consistently in Class III across the years analyzed, reflecting reduced biological activity and favorable oxygen conditions despite sediment dynamics. The complete seasonal WPI dataset for the Pančevo station is also included in Table 11.

This seasonal variation emphasizes the need for targeted monitoring during critical periods, particularly in summer and autumn, to mitigate pollution risks and ensure sustainable water quality management.

4. Conclusions

The consistent monitoring and analysis of water quality in the Tamiš River have highlighted significant challenges related to anthropogenic pressures, particularly urban runoff, agricultural practices, and inadequate wastewater treatment. The key findings include elevated levels of nitrites and orthophosphates at both hydrological stations, with the Pančevo hydrological station showing extreme microbial contamination in 2015. In contrast, Jaša Tomić hydrological station exhibited higher levels of heavy metals and suspended sediments, emphasizing diverse pollution sources along the river’s course.

Seasonal analysis of water quality parameters and the Water Pollution Index (WPI) further underscores temporal variability and critical periods of heightened ecological vulnerability. During spring, water quality at both stations generally aligns with Class I standards, highlighting balanced ecological conditions. However, summer presents significant stress, particularly at the Pančevo hydrological station, where the WPI values peaked at an alarming 26.47 in 2015, reflecting severe microbial contamination. Autumn represents a period of stabilization, although the sporadic peaks in WPI values, especially at the Pančevo hydrological station, emphasize the impact of nutrient runoff and rainfall. Winter exhibits stability in water quality, though occasional exceedances in heavy metals and elevated WPI values at the Jaša Tomić hydrological station indicate sediment interactions and reduced flow dynamics. These findings underscore the seasonal complexity of pollution dynamics in the Tamiš River system.

This study underscores the critical importance of implementing integrated water management strategies to address these issues. Upgrading wastewater treatment facilities, enforcing stricter industrial discharge regulations, and promoting sustainable agricultural practices are essential steps to mitigate pollution. Furthermore, restoring monitoring at the Pančevo station is imperative for comprehensive long-term assessments. Taking into account that the Tamiš River is an international river and the location of Jaša Tomić hydrological station is near the Serbian–Romanian border, joint measures of Serbia and Romania should be implemented to improve water quality.

Additionally, it is essential to engage the local community in efforts to protect water quality by implementing educational initiatives, encouraging sustainable practices, and increasing awareness of how human activities affect the river. Providing incentives for farmers and industrial sectors that adopt eco-friendly technologies could help minimize pollution. Additionally, authorities should establish comprehensive long-term water management strategies, ensuring consistent river monitoring and prompt action in response to detected issues.

Protecting the Tamiš River is vital for maintaining its ecological integrity, supporting local biodiversity, and safeguarding public health. Future research should focus on identifying the impacts of specific pollution sources and evaluating the effectiveness of implemented mitigation measures. By adopting a multi-faceted approach, it is possible to ensure the sustainable use of this crucial water resource and contribute to broader ecological stability.