The effect of oil sands process-affected water and naphthenic acids on the germination and development of Arabidopsis

Oil sands mining in the Athabasca region of northern Alberta results in the production of large volumes of oil sands process-affected water (OSPW). We have evaluated the effects of OSPW, the acid extractable organic (AEO) fraction of OSPW, and individual naphthenic acids (NAs) on the germination and development of the model plant, Arabidopsis thaliana (Arabidopsis). The surrogate NAs that were selected for this study were petroleum NAs that have been used in previous toxicology studies and may not represent OSPW NAs. A tricyclic diamondoid NA that was recently identified as a component of OSPW served as a model NA in this study. Germination of Arabidopsis seeds was not inhibited when grown on medium containing up to 75% OSPW or by 50 mg L⁻¹ AEO. However, simultaneous exposure to three simple, single-ringed surrogate NAs or a double-ringed surrogate NA had an inhibitory effect on germination at a concentration of 10 mg L⁻¹, whereas inhibition of germination by the diamondoid model NA was observed only at 50 mg L⁻¹. Seedling root growth was impaired by treatment with low concentrations of OSPW, and exposure to higher concentrations of OSPW resulted in increased growth inhibition of roots and primary leaves, and caused bleaching of cotyledons. Treatment with single- or double-ringed surrogate NAs at 10 mg L⁻¹ severely impaired seedling growth. AEO or diamondoid NA treatment was less toxic, but resulted in severely impaired growth at 50 mg L⁻¹. At low NA concentrations there was occasionally a stimulatory effect on root and shoot growth, possibly owing to the broad structural similarity of some NAs to known plant growth regulators such as auxins. This report provides a foundation for future studies aimed at using Arabidopsis as a biosensor for toxicity and to identify genes with possible roles in NA phytoremediation.     

Toxicity assessment of collected fractions from an extracted naphthenic acid mixture

Recent expansion within the oil sands industry of the Athabasca Basin of Alberta, Canada has led to increased concern regarding process-affected wastewaters produced during bitumen extraction. Naphthenic acids (NAs) have been identified as the primary toxic constituents of oil sands process-affected waters (OSPW) and studies have shown that with time, microbial degradation of lower molecular weight NAs has led to a decrease in observed toxicity. As earlier studies identified the need for an "unequivocal demonstration" of lower molecular weight NAs being the primary contributors to mixture toxicity, a study was initiated to fractionate an extracted NA mixture by molecular weight and to assess each fraction's toxicity. Successful molecular weight fractionation of a methylated NA mixture was achieved using a Kugelrohr distillation apparatus, in which fractions collected at higher boiling points contained NAs with greater total carbon content as well as greater degree of cyclicity. Assays with Vibrio fischeri bioluminescence (via Microtox assay) revealed that the lowest molecular weight NAs collected had higher potency (EC50: 41.9+/-2.8 mg l(-1)) than the highest molecular weight NAs collected (EC50: 64.9+/-7.4 mg l(-1)). Although these results support field observations of microbial degradation of low molecular weight NAs decreasing OSPW toxicity, it is not clear why larger NAs, given their greater hydrophobicity, would be less toxic.     

Electrochemical mineralization and detoxification of naphthenic acids on boron-doped diamond anodes

Electrochemical oxidation (ELOX) with boron-doped diamond (BDD) anodes was successfully applied to degrade a model aqueous solution of a mixture of commercial naphthenic acids (NAs). The model mixture was prepared resembling the NA and salt composition of oil sands process-affected water (OSPW) as described in the literature. The initial concentration of NAs between 70 and 120 mg/L did not influence the electrooxidation kinetics. However, increasing the applied current density from 20 to 100 A/m² and the initial chloride concentration from 15 to 70 and 150 mg/L accelerated the rate of NA degradation. At higher chloride concentration, the formation of indirect oxidative species could contribute to the faster oxidation of NAs. Complete chemical oxygen demand removal at an initial NA concentration of 120 mg/L, 70 mg/L of chloride and applied 50 A/m² of current density was achieved, and 85% mineralization, defined as the decrease of the total organic carbon (TOC) content, was attained. Moreover, after 6 h of treatment and independently on the experimental conditions, the formation of more toxic species, i.e. perchlorate and organochlorinated compounds, was not detected. Finally, the use of ELOX with BDD anodes produced a 7 to 11-fold reduction of toxicity (IC₅₀ towards Vibrio fischeri) after 2 h of treatment.     

Ozonation of oil sands process water removes naphthenic acids and toxicity

Naphthenic acids are naturally-occurring, aliphatic or alicyclic carboxylic acids found in petroleum. Water used to extract bitumen from the Athabasca oil sands becomes toxic to various organisms due to the presence of naphthenic acids released from the bitumen. Natural biodegradation was expected to be the most cost-effective method for reducing the toxicity of the oil sands process water (OSPW). However, naphthenic acids are poorly biodegraded in the holding ponds located on properties leased by the oil sands companies. In the present study, chemical oxidation using ozone was investigated as an option for mitigation of this toxicity. Ozonation of sediment-free OSPW was conducted using proprietary technology manufactured by Seair Diffusion Systems Inc. Ozonation for 50min generated a non-toxic effluent (based on the Microtox bioassay) and decreased the naphthenic acids concentration by approximately 70%. After 130min of ozonation, the residual naphthenic acids concentration was 2mgl(-1): <5% of the initial concentration in the filtered OSPW. Total organic carbon did not change with 130min of ozonation, whereas chemical oxygen demand decreased by approximately 50% and 5-d biochemical oxygen demand increased from an initial value of 2mgl(-1) to a final value of 15mgl(-1). GC-MS analysis showed that ozonation resulted in an overall decrease in the proportion of high molecular weight naphthenic acids (n> or = 22).     

Naphthenic acid biodegradation by the unicellular alga Dunaliella tertiolecta

Naphthenic acids (NAs) are a major contributor to toxicity in tailings waste generated from bitumen production in the Athabasca Oil Sands region. While investigations have shown that bacteria can biodegrade NAs and reduce tailings toxicity, the potential of algae to biodegrade NAs and the biochemical mechanisms involved remain poorly understood. Here, we discovered that the marine alga Dunaliella tertiolecta is able to tolerate five model NAs (cyclohexanecarboxylic acid, cyclohexaneacetic acid, cyclohexanepropionic acid, cyclohexanebutyric acid and 1,2,3,4-tetrahydro-2-naphthoic acid) at 300 mg L⁻¹, a level which exceeds that of any single or combination of NAs typically found in tailings ponds. Moreover, we show that D. tertiolecta can metabolize four of the model NAs. Analysis of NA-amended cultures of D. tertiolecta via low resolution gas chromatography-mass spectrometry allowed us to quantify decreasing NA levels, identify metabolites, and formulate putative mechanisms of biodegradation. Degradation of cyclohexanebutyric acid and cyclohexanepropionic acid proceeded via β-oxidation and resulted in the transient accumulation of cyclohexaneacetic acid and cyclohexanecarboxylic acid, respectively. Cyclohexanecarboxylic acid was metabolized via 1-cyclohexenecarboxylic acid suggesting that further degradation may occur by step-wise β-oxidation. When D. tertiolecta was inoculated in the presence of oil sands tailings water from the Athabasca region, biodegradation of single-ring NAs was observed relative to controls. This result corroborates the trend we observed with the single-ring model NAs.     

Estimating naphthenic acids concentrations in laboratory-exposed fish and in fish from the wild

Naphthenic acids (NAs) are the most water-soluble organic components found in the Athabasca oil sands in Alberta, Canada, and these acids are released into aqueous tailing waters as a result of bitumen extraction. Although the toxicity of NAs to fish is well known, there has been no method available to estimate NAs concentrations in fish. This paper describes a newly developed analytical method using single ion monitoring gas chromatography-mass spectrometry (GC-MS) to measure NAs in fish, down to concentrations of approximately 0.1mgkg(-1) of fish flesh. This method was used to measure the uptake and depuration of commercial NAs in laboratory experiments. Exposure of rainbow trout (Oncorhynchus mykiss) to 3mg NAsl(-1) for 9d gave a bioconcentration factor of approximately 2 at pH 8.2. Within 1d after the fish were transferred to NAs-free water, about 95% of the NAs were depurated. In addition, the analytical method was used to determine if NAs were present in four species of wild fish - northern pike (Esox lucius), lake whitefish (Coregonus clupeaformis), white sucker (Catostomus commersoni), walleye (Sander vitreus) - collected from near the oil sands. Flesh samples from 23 wild fish were analyzed, and 18 of these had no detectable NAs. Four fish (one of each species) contained NAs at concentrations from 0.2 to 2.8mgkg(-1). The GC-MS results from one wild fish presented a unique problem. However, with additional work it was concluded that the NAs concentration in this fish was <0.1mgkg(-1).     

Acute toxicity of aromatic and non-aromatic fractions of naphthenic acids extracted from oil sands process-affected water to larval zebrafish

The toxicity of oil sands process-affected water (OSPW) has regularly been attributed to naphthenic acids, which exist in complex mixtures. If on remediation treatment (e.g., ozonation) or on entering the environment, the mixtures of these acids all behave in the same way, then they can be studied as a whole. If, however, some acids are resistant to change, whilst others are not, or are less resistant, it is important to establish which sub-classes of acids are the most toxic.     

Effects of oil sands process-affected waters and naphthenic acids on yellow perch (Perca flavescens) and Japanese medaka (Orizias latipes) embryonic development

Syncrude Canada Ltd. is currently developing environmentally acceptable oil sands process-affected water management methods as part of their land reclamation strategy. Surface waters of the “wet landscape” reclamation option characteristically have elevated concentrations of sodium sulphate and naphthenic acids (NAs), with low levels of PAHs. The following experiment compared early-life stage responses of yellow perch (Perca flavescens) to those of Japanese medaka (Oryzias latipes) when exposed to Mildred Lake settling basin (MLSB) surface water and a commercial sodium naphthenate (Na-NA) standard. Perch eggs were fertilized and incubated in: 100%, 50%, 20%, 4%, 0.8%, and 0.16% dilutions of MLSB water, as well as 20, 10, 5, 2.5, and 1.25 mg/l solutions of the commercial standard. Medaka embryos were exposed to the same treatments, post-fertilization. Both species demonstrated an increase in the incidence of deformity, and a decrease in length at hatch as NA concentrations increased. MLSB surface water contained higher levels of NAs than the commercial standard, however, showed consistently higher NA threshold effect concentrations for both species. Significant differences between the MLSB water and the Na-NA standard suggest that they contain NA congeners with different toxicity, or other compounds such as PAHs. Species differences in thresholds could be explained by the difference in developmental stage in which the exposures were initiated.     

Diethylaminoethyl-cellulose clean-up of a large volume naphthenic acid extract

The Athabasca oil sands of Alberta, Canada contain an estimated 174 billion barrels of bitumen. During oil sands refining processes, an extraction tailings mixture is produced that has been reported as toxic to aquatic organisms and is therefore collected in settling ponds on site. Investigation into the toxicity of these tailings pond waters has identified naphthenic acids (NAs) and their sodium salts as the major toxic components, and a multi-year study has been initiated to identify the principal toxic components within NA mixtures. Future toxicity studies require a large volume of a NA mixture, however, a well-defined bulk extraction technique is not available. This study investigated the use of a weak anion exchanger, diethylaminoethyl-cellulose (DEAE-cellulose), to remove humic-like material present after collecting the organic acid fraction of oil sands tailings pond water. The NA extraction and clean-up procedure proved to be a fast and efficient method to process large volumes of tailings pond water, providing an extraction efficiency of 41.2%. The resulting concentrated NA solution had a composition that differed somewhat from oil sands fresh tailings, with a reduction in the abundance of lower molecular weight NAs being the most significant difference. This reduction was mainly due to the initial acidification of tailings pond water. The DEAE-cellulose treatment had only a minor effect on the NA concentration, no noticeable effect on the NA fingerprint, and no significant effect on the mixture toxicity towards Vibrio fischeri.     

A detailed field-based evaluation of naphthenic acid mobility in groundwater

An anaerobic plume of process-affected groundwater was characterized in a shallow sand aquifer adjacent to an oil sands tailings impoundment. Based on biological oxygen demand measurements, the reductive capacity of the plume is considered minimal. Major dissolved components associated with the plume include HCO₃, Na, Cl, SO₄, and naphthenic acids (NAs). Quantitative and qualitative NA analyses were performed on groundwater samples to investigate NA fate and transport in the subsurface. Despite subsurface residence times exceeding 20 years, significant attenuation of NAs by biodegradation was not observed based on screening techniques developed at the time of the investigation. Relative to conservative tracers (i.e., Cl), overall NA attenuation in the subsurface is limited, which is consistent with batch sorption and microcosm studies performed by other authors. Insignificant biological oxygen demand and low concentrations of dissolved As (< 10 µg L^− 1) in the plume suggest that the potential for secondary trace metal release, specifically As, via reductive dissolution reactions driven by ingress of process-affected water is minimal. It is also possible that readily leachable As is not present in significant quantities within the sediments of the study area. Thus, for similar plumes of process-affected groundwater in shallow sand aquifers which may occur as oil sands mining expands, a reasonable expectation is for NA persistence, but minimal trace metal mobilization.     

In vivo endocrine effects of naphthenic acids in fish

Oil pollution from various sources, including exploration, production and transportation, is a growing global concern. The highest toxicity of hydrocarbon pollutants is associated with the water-soluble phase compounds, including naphthenic acids, a known component found in all hydrocarbon deposits. Recently, naphthenic acids (NAs) have shown estrogenic and anti-androgenic effects in vitro. For this reason we investigated the potential effects of two commercial mixtures of naphthenic acids on fish in vivo, using the three-spined stickleback (Gasterosteus aculeatus) as a model species.     

Evolution of China’s water issues as framed in Chinese mainstream newspaper

There is an urgent need globally to trigger fundamental societal changes in water management away from existing unsustainable paradigms. This paper attempts to understand the evolution of newspaper coverage of water issues in China by analyzing water-related articles in a major national newspaper, the People’s Daily, over the period 1946–2012 using a content analysis approach. The major findings include the following: (1) water issues were in relatively prominent positions in the newspaper; (2) the reporting of water issues in China experienced three stages: 1946 to the middle of 1980s—flood and drought control and water for food production, the middle of 1980s to 1997—water for economic development, and 1998 to the present—water for the environmental sustainability and economic development; (3) the reporting of water issues in the People’s Daily clearly reflected China’s top-down water resources management system, and no “real” public opinions on water were reported during the study period; and (4) the People’s Daily is just a wind vane of Chinese mainstream values and policies on water. The findings supported the realist assumption that the societal value changes on water issues in China were triggered by a range of factors including biophysical pressure (floods and droughts), political campaign (the Cultural Revolution), macro-economic reform (Reform and Opening-up), water institutional arrangement (the Water Law), and water management reform (the No. 1 Central Document on water reform). While there are similarities and differences between this study and other studies, important implications for more sustainable water management are a need to strengthen academic specialists’ and NGO’s voices in the newspaper to create a better informed public, and to stimulate practices toward sustainable water use.     

Analysis of polychlorinated dibenzo-p-dioxins and furans in various aqueous samples in Taiwan

Twenty-one fresh water samples were taken from reservoirs, wells and drinking water treatment plants in Taiwan for measurement of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) concentrations. Due to low concentration of PCDD/Fs, water samples (400-1000 L) were collected by using the on-site large volume pre-concentration system and analyzed by high resolution gas chromatography (HRGC)/high resolution mass spectrometer (HRMS). Different characteristics of dioxin profiles in surface water and groundwater are observed. The PCDD/F concentrations in fresh water samples varied from 0.001 to 0.265 pg WHO₉₈-TEQ/L which are lower than the standard (12 pg WHO₉₈-TEQ/L) set by the Taiwan Environmental Protection Administration (TEPA) for drinking water. Only a small fraction (<5%) of the total PCDD/F concentration in fresh water samples was water-soluble. As a result of their hydrophobicity, PCDD/Fs are effectively removed along with suspended solid via the water treatment process (average 98% removal efficiency).     

Occurrence of diarrheagenic Escherichia coli genes in raw water of water treatment plants

Purpose

The high incidences of waterborne diseases are frequently associated with diarrheagenic Escherichia coli (DEC). DEC may pose a health risk to people who contact surface water for recreation or domestic use. However, there is no published report on the monitoring of DEC in drinking water sources in Taiwan. In this study, the occurrence of DEC genes in raw water for water treatment plants in Taiwan was investigated.

Method

Raw water samples were taken from water treatment plants adjacent to the Kaoping River in southern Taiwan. Each water sample was treated with membrane filtration followed by DNA extraction from the concentrate and concentrate enrichment, respectively. The target genes for various DEC strains of genes were identified, including enteroaggregative E. coli (EAEC), enterohemorrhagic E. coli (EHEC), enteroinvasive E. coli (EIEC), enteropathogenic E. coli (EPEC), and enterotoxigenic E. coli (ETEC).

Results

Among 55 water samples analyzed, DEC genes were detected in 16 (29.1%) samples. Strain-specific genes for EAEC, EHEC, EIEC, and EPEC were found in the percentages of 3.6%, 10.9%, 9.1%, and 9.1%, respectively. The specific gene for ETEC is not detected in the study. By looking at the presence/absence of specific genes and water sample characteristics, water temperature was found to differ significantly between samples with and without EHEC gene. In addition, pH levels differed significantly for EHEC and EPEC presence/absence genes, and turbidity was significantly different for water with and without EPEC genes.

Conclusion

DEC genes were detected in 29.1% of the raw water samples in the study location. The potential health threat may be increased if the treatment efficiencies are not properly maintained. Routine monitoring of DEC in drinking water sources should be considered.     

A level change in mutagenicity of Japanese tap water over the past 12 yr

A relative comparison study of mutagenicity in Japanese tap water was conducted for 1993 and 2005 surveys. It intended to assess the effects of advanced water treatment installations to water works, improvement of raw water quality and improvement of residual HOCl concentration controlling. Sampling points (taps) were the same in both surveys. The results of 245 samples obtained by the Ames Salmonella mutagenicity test (Ames test) were analyzed. The Ames tests were conducted by using Salmonella typhimurium TA98 and TA100 strains with and without exogenous activation (S9). With the exception of TA100-S9, the other conditions needed no discussion as a factor in the mutagenicity level change. The average mutagenicity in 1993 and 2005 under the conditions of TA100-S9 were 2600 and 1100 net revertant L⁻¹, respectively. This indicated that the mutagenicity level of Japanese tap water decreased during the 12-yr period. Particularly a remarkable decrease in mutagenicity was observed in the water works where the advanced water treatments were installed during the 12-yr period. The advanced water treatments were effective in decreasing the mutagenicity of tap water. Mutagenicity also decreased in the water works with conventional water treatments; the improvement of residual HOCl concentration controlling was also considered to be effective in decreasing the mutagenicity of tap water.     

Influence of seasonal climate differences on the pharmaceutical,hormone and personal care product removal efficiency of a drinking water treatment plant

The potential presence of pharmaceuticals, hormones and personal care products in drinking water supplies has raised concerned over the efficiency with which these substances are removed by water treatment processes. In this work, we analyzed samples of raw, unprocessed water collected in different periods and found them to contain higher levels of these contaminants in the colder periods (viz. 12–314 ng L⁻¹ in autumn and winter as compared to 8–127 ng L⁻¹ in spring and summer) as a result of their biodegradation being favoured by high temperatures and solar irradiance. We also assessed the efficiency with which these contaminants are removed from drinking water by a water treatment plant operating in south-eastern Spain. Preoxidation with potassium permanganate and chloramination with sodium hypochlorite in the presence of highly concentrated ammonia were found to be the treatment steps most markedly contributing to the removal of pharmaceuticals, hormones and personal care products from drinking water (especially in the warmer periods, where these contaminants were completely removed from the water). By contrast, water treated in the colder periods (autumn and winter) still contained small amounts of ibuprofen and carbamazepine (0.09–0.5 ng L⁻¹) which, however, accounted for less than 0.2% of their original concentrations in the water prior to treatment.     

Relative influence of the dissolved humic material on the solid-phase extraction efficiency of pesticides from environmental water

The effect of organic matter on the solid-phase extraction (SPE) efficiency for pesticides belonging to different chemical groups (urea-derivatives, carbamates and triazines) and having different polarities, was simultaneously studied for the first time in pure and simulated water samples. SPE was carried out in precolumns packed with C18 silica or styrene-divinylbenzene copolymer PLRP-S phases on-line coupled to high performance liquid chromatography (HPLC) analysis. Retention factors in water (k'_W) were estimated for 25 compounds and used for the calculation of the theoretical breakthrough volume (Vb_T) in pure water. Experimental breakthrough volumes (Vb_E) were first determined using purified and deionized water as the matrix for selected compounds having Vb_T < 500 mL; then, the same water with an added humic acid sodium salt (HA) at 0.4–5.6 mg/L of dissolved organic carbon (DOC) content, was used as the matrix for compounds having VbE < 500 mL in pure water. Several polar pesticides showed negative linear or logarithmic Vb_E curves depending on HA content; their recoveries were also determined in environmental samples having low dissolved organic carbon values, between 0.5–6.4 mg/L. A similar behavior was observed for these compounds in simulated and natural water samples, where DOC concentration and the percolated volume (Vp) mainly determine the solute recoveries values. However, the variation of recoveries as a function of DOC content could be negative or null depending on the two examined conditions (Vp lower or larger than Vb_E in pure water). Results demonstrated that breakthrough volume must always be considered to correctly interpret the participation of dissolved humic material on the SPE efficiency of organic micropollutants in water.     

Preliminary toxicological assessment of phthalate esters from drinking water consumed in Portugal

This paper reports, for the first time, the concentrations of selected phthalates in drinking water consumed in Portugal. The use of bottled water in Portugal has increased in recent years. The main material for bottles is polyethylene terephthalate (PET). Its plasticizer components can contaminate water by leaching, and several scientific studies have evidenced potential health risks of phthalates to humans of all ages. With water being one of the most essential elements to human health and because it is consumed by ingestion, the evaluation of drinking water quality, with respect to phthalate contents, is important. This study tested seven commercial brands of bottled water consumed in Portugal, six PET and one glass (the most consumed) bottled water. Furthermore, tap water from Lisbon and three small neighbor cities was analyzed. Phthalates (di-n-butyl phthalate ester (DnBP), bis(2-ethylhexyl) phthalate ester (DEHP), and di-i-butyl phthalate ester (DIBP)) in water samples were quantified (PET and glass) by means of direct immersion solid-phase microextraction and ionic liquid gas chromatography associated with flame ionization detection or mass spectrometry due to their high boiling points and water solubility. The method utilized in this study showed a linear range for target phthalates between 0.02 and 6.5 μg L^?1, good precision and low limits of detection that were between 0.01 and 0.06 μg L^?1, and quantitation between 0.04 and 0.19 μg L^?1. Only three phthalates were detected in Portuguese drinking waters: dibutyl (DnBP), diisobutyl (DIBP), and di(ethylhexyl) phthalate (DEHP). Concentrations ranged between 0.06 and 6.5 μg L^?1 for DnBP, between 0.02 and 0.16 μg L^?1 for DEHP, and between 0.1 and 1.89 μg L^?1 for DIBP. The concentration of DEHP was found to be up to five times higher in PET than in glass bottled water. Surprisingly, all the three phthalates were detected in glass bottled water with the amount of DnBP being higher (6.5 μg L^?1) than in PET bottled water. These concentrations do not represent direct risk to human health. Regarding potable tap water, only DIBP and DEHP were detected. Two of the cities showed concentration of all three phthalates in their water below the limits of detection of the method. All the samples showed phthalate concentrations below 6 μg L^?1, the maximum admissible concentration in water established by the US Environmental Protection Agency. The concentrations measured in Portuguese bottled waters do not represent any risk for adult's health.     

Evaluation of spatial-temporal variations and trends in surface water quality across a rural-suburban-urban interface

Water quality degradation is often a severe consequence of rapid economic expansion in developing countries. Methods to assess spatial-temporal patterns and trends in water quality are essential for guiding adaptive management efforts aimed at water quality remediation. Temporal and spatial patterns of surface water quality were investigated for 54 monitoring sites in the Wen-Rui Tang River watershed of eastern China to identify such patterns in water quality occurring across a rural-suburban-urban interface. Twenty physical and chemical water quality parameters were analyzed in surface waters collected once every 4–8 weeks from 2000 to 2010. Temporal and spatial variations among water quality parameters were assessed between seasons (wet/dry) and among major land use zones (urban/suburban/rural). Factor analysis was used to identify parameters that were important in assessing seasonal and spatial variations in water quality. Results revealed that parameters related to organic pollutants (dissolved oxygen (DO), chemical oxygen demand (manganese) (COD_Mn), and 5-day biochemical oxygen demand (BOD₅)), nutrients (ammonia nitrogen (NH₄ ⁺-N), total nitrogen (TN), total phosphorus (TP)), and salt concentration (electrical conductivity (EC)) were the most important parameters contributing to water quality variation. Collectively, they explained 70.9 % of the total variance. A trend study using the seasonal Kendall test revealed reductions in COD_Mn, BOD₅, NH₄ ⁺-N, petrol, V-phen, and EC concentrations over the 11-year study period. Cluster analysis was employed to evaluate variation among 14 sampling sites representative of dominant land use categories and indicated three, three, and four clusters based on organic, nutrient, and salt water quality characteristics, respectively. Factors that are typically responsible for water quality degradation (including population, topography, and land use) showed no strong correlation with water quality trends implying considerable point source inputs in the watershed. The results of this study help inform ongoing water quality remediation efforts by documenting trends in water quality across various land use zones.