Copper export and mobility in acid mine drainage are difficult to understand with conventional approaches. Within this context, Cu isotopes could be a powerful tool and here we have examined the relative abundance of dissolved (<0.22 μm) Cu isotopes (δ⁶⁵Cu) in the Meca River which is an outlet of the Tharsis mine, one of the largest abandoned mines of the Iberian Pyrite Belt, Spain. We followed the chemical and isotopic composition of the upstream and downstream points of the catchment during a 24-h diel cycle. Additional δ⁶⁵Cu values were obtained from the tributary stream, suspended matter (>0.22 μm) and bed sediments samples. Our goals were to 1) assess Cu sources variability at the upstream point under contrasted hydrological conditions and 2) investigate the conservative vs. non conservative Cu behavior along a stream. Average δ⁶⁵Cu values varied from −0.47 to −0.08‰ (n = 9) upstream and from −0.63 to −0.31‰ downstream (n = 7) demonstrating that Cu isotopes are heterogeneous over the diel cycle and along the Meca River. During dry conditions, at the upstream point of the Meca River the Cu isotopic composition was heavier which is in agreement with the preferential release of heavy isotopes during the oxidative dissolution of primary sulfides. The more negative values obtained during high water flow are explained by the contribution of soil and waste deposit weathering. Finally, a comparison of upstream vs. downstream Cu isotope composition is consistent with a conservative behavior of Cu, and isotope mass balance calculations estimate that 87% of dissolved Cu detected downstream originate from the Tharsis mine outlet. These interpretations were supported by thermodynamic modelling and sediment characterization data (X-ray diffraction, Raman Spectroscopy). Overall, based on contrasted hydrological conditions (dry vs flooded), and taking the advantage of isotope insensitivity to dilution, the present work demonstrates the efficiency of using the Cu isotopes approach for tracing sources and processes in the AMD regions.

Eating fish provides numerous health benefits, but it is also a dominant pathway for human exposure to contaminants. Many studies have examined mercury (Hg) accumulation in fish, but fewer have considered other elements, such as arsenic (As) and chromium (Cr). Recently, freshwater fish from several pristine boreal systems across northern Ontario, Canada, have been reported with elevated concentrations of As and Cr for reasons that are not well understood. Our goal was to investigate the ecological and environmental influences over concentrations of As, Cr, and other elements in these fish to better understand what affects metal uptake and the risk to consumers. We measured 10 elements (including As, Cr, Hg) as well as carbon (δ¹³C), nitrogen (δ¹⁵N), and sulfur (δ³⁴S) stable isotopes in 388 fish from 25 lake and river sites across this remote region. These data were used to determine the effect of: 1) trophic ecology; and 2) watershed geology on piscine elemental content. Overall, most element concentrations were low, often below provincial advisory benchmarks (ABs). However, traces of Hg, As, Cr, and selenium (Se) were detected in most fish. Based on their exceedance of their respective ABs, the most restrictive elements on fish consumption in these boreal systems were Hg > As > Cr. Arsenic and Se, but not Cr concentrations were related to fish size and trophic ecology (inferred from δ¹³C and δ¹⁵N), suggesting bioaccumulation of the former elements. Fish with enriched δ³⁴S values, suggestive of anadromous behaviour, had marginally lower Hg but higher Se concentrations. Modeling results suggested a strong effect of site-specific factors, though we found weak trends between piscine elemental content and geological features (e.g., mafic intrusions), potentially due to the broad spatial scale of this study. Results from this study address gaps in our understanding of As and Cr bioaccumulation and will help to inform fish consumption guidelines.

This study determined the contamination levels of oil and grease (O/G) across nine (9) galamsey operations under different environmental media (background soil, surface drainage, slurry/sludge and galamsey wastes) in three galamsey hotspot assemblies (Tarkwa Nsuaem, Amenfi East and Prestea Huni Valley) within the Western region of Ghana. Triplicate samples each of the four environmental media for the nine galamsey types (Washing Board, Washing Plant, Anwona, Dig and Wash, Dredging, Underground Abandoned Shaft, Underground Sample Pit, Chamfi and Mill House) were collected and analysed using n-hexane extractable materials in acidic medium by extraction and gravimetry to determine O/G concentrations. From the comparison of mean ranked concentration of O/G, using Kruskal-Wallis Test, the observed differences in the ranking was significant across all four media. The O/G concentrations for Anwona, Chamfi, Mill House, Washing Board and Washing Plant galamsey recorded exceedances when compared to the Ghana EPA Effluent Guideline Value of 100 mg/L for water and The New Dutch Lists’ Target and Intervention Value of 50 mg/kg and 500 mg/kg for solid/semi-solid materials. Consistently and for all environmental media types, the levels of O/G across the galamsey types were in the descending order of: Washing Board, Chamfi, Anwona, Mill House, Washing Plant, Underground Sample Pit, River Dredging, Dig and Wash, Underground Abandoned Shaft and Control Sample (non-galamseyed areas). In general, the surface drainage medium was predominantly found to be the most impacted upon medium from hydrocarbons by seven of the nine galamsey operations (Washing Board, Anwona, Chamfi, Mill House, Dredging, Dig and Wash and Underground Sample Pit). This was followed by slurry/sludge, background soil and waste media in that order. Expectedly, there were no exceedances for the Reference or Control Samples (non-galamseyed areas).

The occurrence of emergent contaminants, 24 polybrominated diphenyl ethers (PBDEs), di(2-ethylhexyl)phthalate (DEHP), dibutyl phthalate (DBP), butyl benzyl phthalate (BBP), diethyl phthalate (DEP), dimethyl phthalate (DMP), di-n-octyl phthalate (DnOP), bisphenol A (BPA) and nonylphenol (NP), was investigated in sediments and fishes collected from the Tamsui River system to determine the factors that influence their distribution and their risk to aquatic ecosystems and human health. The concentrations of total PBDEs, DEHP, DBP, BBP, DEP, DMP, DnOP, BPA and NP in sediments were 1–955, ND-23570, <50–411, <50–430, ND-80, ND-<50, ND-<50, 1–144, 3–19624 μg/kg dw, respectively. The spatial-temporal distribution trends of these compounds in sediments could be attributed to urbanization, industrial discharge and effluents from wastewater treatment plants. The PBDE congener distribution patterns (BDE-209 was the dominant congener) in sediments reflected the occurrence of debromination of BDE-209 and the elution of penta-BDE from the treated products. The concentrations of total PBDEs, DEHP, DBP, BBP, DEP, DMP, DnOP, BPA and NP in fish muscles were 2–66, 17–1046, <10–231, <10–66, <30, ND-<30, ND-<30, 0.4–7 and 3–440 μg/kg ww, respectively. The species-specific bioaccumulation of these compounds by fish was found and four species particularly showed high bioaccumulation potential. BDE-47 was the predominant BDE congener in fish muscles, suggesting high bioavailability and bioaccumulation of this compound. The results of biota–sediment accumulation factors showed that BDE-47, 99, 100, 153 and 154 had relatively high bioavailability and bioaccumulation potential for some fish species. The ecological risk assessment showed that the concentrations of BPA and NP in sediments were likely to have adverse effects on aquatic organisms (risk quotients > 1). The human health risk assessment according to hazard quotients (HQs) and carcinogenic risks (CRs) revealed no remarkable risk to human health through consumption of fish contaminated with BDE-47, 99, 100, 154, 209, DEHP, BPA and NP.

Riverbed sediments are the interface layer in riverine ecosystems connecting the overlying medium of water and the vadose zone. The transport behavior of phosphorus (P), which has been recognized as the primary cause of freshwater eutrophication, in riverbed sediments remains unclear. Understanding the impact of riverbed sediments on P transport is a necessary prerequisite for the development of appropriate strategies to reduce potential groundwater pollution. In this study, riverbed sediments were collected from the upstream, midstream, and downstream sections of the Beiyun River, China, and packed into vertical soil columns to perform leaching experiments to quantify P transport characteristics. In addition, the impact mechanisms were further explored by conducting laboratory batch tests of P adsorption and desorption. The results demonstrated that approximately 80% of P can be adsorbed by riverbed sediments in soil column leaching experiment, and a tailing phenomenon was observed in its desorption. The hydraulic conductivity properties of riverbed sediments were evaluated by the advection-dispersion equation, showing a gradually decreasing adsorption capacity for P from upstream to downstream sections, which was supported by the results obtained from adsorption–desorption thermodynamic and kinetic batch tests. The estimated annual leaching masses of P increased from 60.72 g/(m² a) in the upstream section to 132.31 g/(m² a) in the downstream section. The role of riverbed sediments as a source or sink of P is possibly determined by their coarse sand particles content, and the mean equilibrium P concentration (EPC0). The competitive relationship between P and other forms of nutrients also has an important influence on its source-sink role. These findings suggest that the prevention of the potential P leaching is most needed in the downstream sections of Beiyun River, and corresponding control strategies should be developed to avoid groundwater pollution.

Contaminated groundwater is considered as one of the most important pathways of human exposure to the geogenic contaminants. Present study has been conducted in a part of Indus basin to investigate the presence and spatial distribution of arsenic (As) and other trace metals in groundwater. The As concentration varies from bdl-255.6 μg/L and 24.6% of the 73 collected groundwater samples have As above world health organization (WHO) guideline of 10 μg/L. High concentration of As is found along the newer alluvium of Ravi River. As is found with high bicarbonate (HCO3−) and Iron (Fe) and low nitrate (NO3−) indicating reductive dissolution of Fe bearing minerals. However, silicate weathering along with high sulphate (SO42) and positive oxidation-reduction potential (ORP) indicates mixed redox conditions. Weathering of minerals along with other major hydrogeochemical process are responsible for composition of groundwater. With 31.5% of the samples, sodium bicarbonate (Na–HCO3) is the major water facies followed by magnesium bicarbonate (Mg–HCO3) in 30% of samples. As, Fe and other trace metals including copper (Cu), cadmium (Cd), chromium (Cr), zinc (Zn) were used to calculate the health risk for children and adults in the region. Out of 73 samples, 58% has high Fe, 32.8% has high Zn, and 4.1% has high Cd which are above the prescribed limits of WHO guidelines. Health risk of the population has been assessed using chronic dose index (CDI), hazardous quotients (HQ) and hazardous index (HI) for children and adults. The mean CDI values follows the order as Fe > Zn > Cu > As > Cr > Cd, while the HQ values indicates high As hazards for both children and adults. 43.8% of the groundwater samples have high HI for adults, however, 49.3% has high HI for children indicating higher risk for children compared to adults. A large-scale testing should be prioritized to test the wells for As and other trace metals in the study region to reduce health risks.

We investigated the profiles and levels of perfluoroalkyl carboxylic acids in edible clams from five fishing sites in Japan (Hokkaido, Himakajima-Aichi, Atsumi-Aichi, Kyoto, and Kumamoto) and one site in Vancouver, Canada in 2017. The mean concentrations of perfluoroalkyl carboxylic acids with 6–15 carbon atoms (C6–C15) in edible clams from Japanese coastal waters ranged from 197 to 1757 pg/g wet weight, but were only 48 pg/g wet weight in clams from the site in Canada. Total perfluoroalkyl carboxylic acid concentrations in clams collected in Japanese waters were 4–40 times higher than concentrations in clams from Canada. Perfluorooctanoic acid (C8) contributed 53% of total perfluoroalkyl carboxylic acid concentrations in the clams from Japanese waters, which may be contaminated from terrestrial sources though river effluents, but was not detected in the clam samples from Canada. Principal component analysis separated shorter- and longer-chain perfluoroalkyl carboxylic acids, suggesting differing emission sources or environmental fate. Consumption of clams may be an exposure pathway of perfluorooctanoic acid in the Japanese population.

The overuse and misuse of antibiotics could promote the emergence of antibiotic resistance genes (ARGs) and pose a potential risk to human health and the ecological environment. In this study, fifteen antibiotics and their corresponding ARGs in water, sediment and sewage treatment plant (STP) effluent were analysed to investigate their occurrence and correlation in the Yangtze River (Jiangsu section) for the first time. The concentrations of erythromycin-H₂O (EM-H₂O) (2.08–30 ng L⁻¹) and ofloxacin (OFL) (290–8400 ng kg⁻¹) were the highest in the water and sediment, respectively, and EM-H₂O and clarithromycin (CLA) posed the highest risks to aquatic organisms. The concentrations of antibiotics in STP effluent were significantly higher (p < 0.05) than those in the water. Norfloxacin (NOR) was the most predominant antibiotic, with low removal efficiency (−38%-51%), in STPs; the concentration of NOR in the STP effluent was 4–6 orders of magnitude higher than that in the water. Moreover, the concentrations of antibiotics and their corresponding ARG abundance in downstream were higher than those in upstream, suggesting that STPs with high concentration levels might be an important source of river contamination. Additionally, the concentrations of antibiotics and the abundance of ARGs might increase after the sewage treatment process. The results also showed the prevalence of sul1 and sul2 in all the sampling sites. Significant correlations (p < 0.0001) were detected between int1 and sul1 and sul2, which resulted from the contribution of int1 to the propagation of ARGs. Overall, this study demonstrated the prevalence of antibiotics and ARGs and their inconsistent correlations in the Yangtze River (Jiangsu section) and provides support for further investigation of the occurrence and spread of antibiotics and ARGs.

Metal contamination in the Pearl River Estuary (PRE) is persistent-, yet a comprehensive understanding of distribution and behavior of metals in surface water of this large, multi-source estuary is still lacking. In the present study, water samples from 24 sites spanning the whole estuary during the dry and wet season were collected and fractioned. Trace metal concentrations in samples were then determined following a preconcentration technique using Nobias Chelate-PA1 resin. Distribution of trace metals exhibited variability along and across estuary, as a result of estuarine mixing, external metal loadings, addition and removal. Behavior of metals was contrasting between the dry and wet seasons, exhibiting metal-specific intercorrelations and dynamics. Colloidal metals (Mn, Ni and Cd) were primarily present in upper estuary and areas affected by external contaminant loading. Colloidal Cu was the only metal that was ubiquitous in the estuary in both seasons. It showed a high affinity for small-size organic colloids (likely fulvic acid) during the dry season. Overall, the present study demonstrated the multi-source character of the PRE and that the behavior of trace metals was controlled by the coupling of hydrologic and geochemical processes, with anthropogenic perturbations.

The extensive use of melamine and its three derivatives (i.e., ammeline, ammelide, and cyanuric acid) resulted in their widespread occurrence in the environment. Nevertheless, limited information is available on their distribution in the aquatic environment. In this study, concentrations and profiles of melamine and its derivatives were determined in 223 water samples, comprising river water, lake water, seawater, tap water, bottled water, rain water, wastewater, and swimming pool water, collected from New York State, USA. The sum concentrations of melamine and its derivatives (∑₄MELs) decreased in the following order: swimming pool water (median: 1.5 × 10⁷ ng/L) ≫ wastewater (1240) > precipitation (739) > tap water (512) > river water (370) > lake water (347) > seawater (186) > bottled water (98). Cyanuric acid was the major compound, accounting for 60–100% of ∑₄MELs concentrations in swimming pool water, wastewater, precipitation, tap water, seawater, and bottled water, whereas melamine dominated in river and lake water (54–64% of ∑₄MELs). Significant positive correlations (0.499 < R < 0.703, p < 0.002) were found between the concentrations of melamine and atrazine (a triazine herbicide) in surface waters. The geographic distribution in the concentrations of ∑₄MELs in river, lake, and tap water corresponded with the degree of urbanization, suggesting that human activities contribute to the sources melamine and cyanuric acid in the aquatic environments. A preliminary hazard assessment of melamine and cyanuric acid in waters suggested that their ecological or human health risks were minimal. This is the first study to document the occurrence and spatial distribution of melamine and its derivatives in waters from the United States.