The impact of point and diffuse sources for 26 per- and polyfluoroalkyl substances (PFASs) in northern Europe were investigated by studying Swedish rivers (n = 40) and recipient seawater (Baltic Sea and Kattegat; n = 18). Different composition profiles were observed in the rivers, with ten rivers having a remarkably high fraction of perfluoroalkane sulfonic acids (PFSAs; 65% of the ƩPFASs) as compared to other rivers (19%) suggesting major impact of one or several source types dominated by PFSAs. Population density and low latitude (south) were strongly correlated to the widely used perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA) as well as to perfluorohexanesulfonic acid (PFHxS). Significant relationships between several PFCAs and PFSAs (i.e. perfluorobutanoic acid (PFBA), perfluoroheptanoic acid (PFHpA), PFOA, perfluorobutanesulfonic acid (PFBS), and PFHxS) and dissolved organic carbon (DOC) were detected (p < 0.05), indicating chemical binding and co-transport with DOC in fresh water and seawater. Partial least squares regression analysis showed that perfluoroalkyl carboxylic acids (PFCAs) were related to latitude according to their perfluorocarbon chain length (C3, C7, C8, C9, C10 and C11), with longer chains associated with higher latitudes. This suggests the presence of mechanisms promoting higher prevalence of longer chained PFCAs in the north, e.g. precursor degradation, and/or aerosol associated stabilization of PFCAs and their precursors.

Radiocesium (137Cs) migration from headwater forested areas to downstream rivers has been investigated in many studies since the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, which was triggered by a catastrophic earthquake and tsunami on 11 March 2011. The accident resulted in the release of a huge amount of radioactivity and its subsequent deposition in the environment. A large part of the radiocesium released has been shown to remain in the forest. The dissolved 137Cs concentration and its temporal dynamics in river water, stream water, and groundwater have been reported, but reports of dissolved 137Cs concentration in soil water remain sparse.In this study, soil water was sampled, and the dissolved 137Cs concentrations were measured at five locations with different land-use types (mature/young cedar forest, broadleaf forest, meadow land, and pasture land) in Yamakiya District, located 35 km northwest of FDNPP from July 2011 to October 2012. Soil water samples were collected by suction lysimeters installed at three different depths at each site. Dissolved 137Cs concentrations were analyzed using a germanium gamma ray detector. The dissolved 137Cs concentrations in soil water were high, with a maximum value of 2.5 Bq/L in July 2011, and declined to less than 0.32 Bq/L by 2012. The declining trend of dissolved 137Cs concentrations in soil water was fitted to a two-component exponential model. The rate of decline in dissolved 137Cs concentrations in soil water (k1) showed a good correlation with the radiocesium interception potential (RIP) of topsoil (0–5 cm) at the same site. Accounting for the difference of 137Cs deposition density, we found that normalized dissolved 137Cs concentrations of soil water in forest (mature/young cedar forest and broadleaf forest) were higher than those in grassland (meadow land and pasture land).

Bioaccumulation and trophic transfer in ecosystems is an important criterion for assessing environmental risks of contaminants. This study investigated bioaccumulation and biomagnification of 13 organic ultraviolet absorbents (UVAs) in marine wildlife organisms in the Pearl River Estuary, South China Sea. The UVAs could accumulate in the organisms with biota - sediment accumulation factors (BSAF) of 0.003–2.152. UV531 was the most abundant and showed the highest tendency to accumulate in the organisms with a median BSAF of 1.105. The UVAs demonstrated species - and compound-specific accumulation in the marine organism. Fishes showed significantly higher capability than the cephalopods and crustaceans in accumulation of the UVAs. Habitat did not demonstrate obvious impact on accumulation of the UVA. On the other hand, benzophenone-3, UV328, and UV234 showed significantly higher concentration in the detritus feeding fishes than carnivorous and planktivorous fishes, suggesting governing effect of dietary habits of the organisms on bioaccumulation of these UVAs. Direct uptake from growth media was a significant exposure pathway of the organisms to the UVAs. The estimated trophic magnification factors and biomagnification factors revealed that UV329, UV531, and octocrylene could potentially biomagnify in the marine food web.

The rapid human activities and urbanization exacerbate the human health risks induced by antibiotic resistance genes (ARGs). In this study, the profiling of ARGs was investigated using high-throughput qPCR from water samples of 13 catchment areas in East Tiaoxi River, China. High prevalence of ARGs indicated significant antibiotic resistance pollution in the research area (absolute abundance: 6.1 × 108–2.1 × 1010 copies/L; relative abundance: 0.033–0.158 copies/cell). Conventional water qualities (COD, TN, TP, NH3-N), bacterial communities and mobile gene elements (MGEs) were detected and analyzed as factors of ARGs shift. Nutrient and MGEs showed positive correlation with most ARGs (P < 0.05) and bacteria community was identified as the key contributing factor driving ARGs alteration. With the land-use study and field investigation, country area, especially arable, was expected as a high spot for ARGs shift and pathogen breeding. Comparing to environmental background, promotion of ARGs and marked shift of bacterial community were observed in country and urban city areas, indicating that human activities may lead to the spread of ARGs. Analysis of factors affecting ARGs in this study may shed new light on the mechanism of the maintenance and propagation of ARGs in urban rivers.

Infections with antibiotic resistant bacteria are among the major threats for human health. Studies elucidating the role of the environment in their spread are still in their infancy, it, however, seems that different environments might function as a long-term reservoir of antibiotic resistance genes (ARGs) that reside within their microbial communities. An increasing number of studies target the presence and the persistence of ARGs in waters and soils that are exposed to human activities; they, however, rarely consider the spatial/temporal variability that predominate in these environments. Here we evaluated the effect of a moderate rain event (4 mm rain h−1) on the abundance and distribution of ARGs (tetA, ermB, blaCTXM, sulII, and qnrS), by comparing measurements of gene abundances during the rainfall to the yearly average, in the waters of a large subalpine river. ARG abundances, which all increased during the rain event, were then correlated to several microbiological, physical and chemical variables, in order to establish their potential origin. Increments in ARG abundances during rainfall (total ARGs: 24 fold) was concomitant to an increase in total phosphorous, N-NH4, and microbial aggregates. Our results show a strong influence of a moderate rainfall on the abundances of ARGs, and suggest the catchment as their source. The impact of moderate rainfalls in areas exposed to anthropic activities should then be considered in modelling and management of ARG dynamics.

Seasonal variations in the concentrations of eight ultraviolet (UV) filters and 22 illicit drugs including their metabolites in the Korean aquatic environment were investigated. Seawater samples from three beaches, water samples from two rivers, and influents and effluents from three wastewater treatment plants were analyzed. The UV filter concentrations in the seawater, river water, and effluent samples were 39.4–296, 35.4–117, and 6.84–51.1 ng L-1, respectively. The total UV filter concentrations in the seawater samples were 1.9–4.4 times higher at the peak of the holiday season than outside the peak holiday season. An environmental risk assessment showed that ethylhexyl methoxy cinnamate (EHMC) could cause adverse effects on aquatic organisms in the seawater at the three beaches during the holiday period. Seven of the 22 target illicit drugs including their metabolites were detected in the wastewater influent samples, and the total illicit drug concentrations in the influent samples were 0.08–65.4 ng L-1. The estimated daily consumption rates for cis-tramadol (Cis-TRM), methamphetamine (MTP), meperidine (MEP), and codeine (COD) were 25.7–118.4, 13.8–36.1, 1.36–12.6, and 1.75–8.64 mg d-1 (1000 people)−1, respectively. In popular vacation area, the illicit drug consumption rates (Cis-TRM, MTP and MEP) were 1.6–2.6 times higher at the peak of the summer holiday season than at the beginning of the summer.

Bacterial degradation is an important clearance pathway for organic contaminants from highly human-impacted environments. However, it is not fully understood how organic contaminants are selected for degradation by bacteria and genes in aquatic environments. In this study, PAH degrading bacterial genera and PAH-degradation-related genes (PAHDGs) in sediments collected from the Pearl River (PR), the Pearl River Estuary (PRE) and the South China Sea (SCS), among which there were distinct differences in anthropogenic impact, were analyzed using metagenomic approaches. The diversity and abundance of PAH degrading genera and PAHDGs in the PR were substantially higher than those in the PRE and the SCS and were significantly correlated with the total PAH concentration. PAHDGs involved with the three key processes of PAH degradation (ring cleavage, side chain and central aromatic processes) were significantly correlated with each other in the sediments. In particular, plasmid-related PAHDGs were abundant in the PR sediments, indicating plasmid-mediated horizontal transfer of these genes between bacteria or the overgrowth of the bacteria containing these plasmids under the stresses of PAHs. Our results suggest that PAH degrading bacteria and genes were rich in PAH-polluted aquatic environments, which could facilitate the removal of PAHs by bacteria.

Industrial discharges of perfluorooctanoic acid (PFOA) to the Ohio River, contaminating water systems near Parkersburg, WV, were previously associated with nearby residents' serum PFOA concentrations above US general population medians. Ohio River PFOA concentrations downstream are elevated, suggesting Mid-Ohio River Valley residents are exposed through drinking water.Quantify PFOA and 10 other per- and polyfluoroalkyl substances (PFAS) in Mid-Ohio River Valley resident sera collected between 1991 and 2013 and determine whether the Ohio River and Ohio River Aquifer are exposure sources.We measured eleven PFAS in 1608 sera from 931 participants. Serum PFOA concentration and water source associations were assessed using linear mixed-effects models. We estimated between-sample serum PFOA using one-compartment pharmacokinetics for participants with multiple samples.In serum samples collected as early as 1991, PFOA (median = 7.6 ng/mL) was detected in 99.9% of sera; 47% had concentrations greater than US population 95th percentiles. Five other PFAS were detected in greater than 82% of samples; median other PFAS concentrations were similar to the US general population. Serum PFOA was significantly associated with water source, sampling year, age at sampling, tap water consumption, pregnancy, gravidity and breastfeeding. Serum PFOA was 40–60% lower with granular activated carbon (GAC) use. Repeated measurements and pharmacokinetics suggest serum PFOA peaked 2000–2006 for participants using water without GAC treatment; where GAC was used, serum PFOA concentrations decreased from 1991 to 2012.Mid-Ohio River Valley residents appear to have PFOA, but not other PFAS, serum concentrations above US population levels. Drinking water from the Ohio River and Ohio River Aquifer, primarily contaminated by industrial discharges 209–666 km upstream, is likely the primary exposure source. GAC treatment of drinking water mitigates, but does not eliminate, PFOA exposure.

The novel eco-friendly algaecidal naphthoquinone derivate was used to control harmful algal bloom causing species Stephanodiscus and, its effect was assessed on other undesired and non-targeted microbial communities. We conducted a mesocosm experiment to investigate the effects of this novel algaecide on native microbial communities rearing in water collected from Nakdonggang River. Upon treatment of the mesocosm with the naphthoquinone derivate the concentration of Chl-a decreased from 20.4 μg L−1 to 9.5 μg L−1 after 2 days. The turbidity has also shown decrement (exhibited 15.5 NTU on the 7th day). The concentrations of DOC and phosphate in the treatment were slightly higher than those in the control due to the decomposition of dead Stephanodiscus, whereas the DO and pH in the treated condition were slightly lower than those in the control; which was due to increment of organic acids and higher degradation activity. Results showed that bacterial abundance were not significantly different but community composition were slightly different as revealed by NGS (Next generation sequencing). The variation in HNF (Heterotrophic nanoflagellates) revealed that the bacterial community composition changed following the change in bacterial abundance. During the treatment, the abundance of Stephanodiscus was significantly reduced by more than 80% after 6 days, and the abundance of ciliates and the dominant species, Halteria grandinella, had shown marked decline. The abundance of zooplankton sharply decreased to 5 ind. L−1on the 8th day but increased again by the end of the study period. The Shannon-Wiener diversity index of phytoplankton, ciliates and zooplankton in the treated mesocosm increased significantly after 4, 7 and 8 days, respectively. The marked changes in the ecosystem structure were observed in treatment compare to control. However, the beneficial microalgal populations were not affected which indicated possibility of restoration of treated ecosystem and regain of healthy community structure after certain period.

Mining activities have contaminated many riverine floodplains with arsenic (As). When floodplain soils become anoxic under water-saturated conditions, As can be released from the solid phase. Several microbially-driven As solubilization processes and numerous influential factors were recognized in the past. However, the interplay and relative importance of soil properties and the influence of environmental factors such as temperature remain poorly understood, especially considering the (co)variation of soil properties in a floodplain. We conducted anoxic microcosm experiments at 10, 17.5, and 25 °C using 65 representative soils from the mining-impacted Ogosta River floodplain in Bulgaria. To investigate the processes of As solubilization and its quantitative variation we followed the As and Fe redox dynamics in the solid and the dissolved phase and monitored a range of other solution parameters including pH, Eh, dissolved organic C, and dissolved Mn. We related soil properties to dissolved As observed after 20 days of microcosm incubation to identify key soil properties for As solubilization. Our results evidenced reductive dissolution of As-bearing Fe(III)-oxyhydroxides as the main cause for high solubilization. The availability of nutrients, most likely organic C as the source of energy for microorganisms, was found to limit this process. Following the vertical nutrient gradient common in vegetated soil, we observed several hundred μM dissolved As after 1–2 weeks for some topsoils (0–20 cm), while for subsoils (20–40 cm) with comparable total As levels only minor solubilization was observed. While high Mn contents were found to inhibit As solubilization, the opposite applied for higher temperature (Q10 2.3–6.1 for range 10–25 °C). Our results suggest that flooding of nutrient-rich surface layers might be more problematic than water-saturation of nutrient-poor subsoil layers, especially in summer floodings when soil temperature is higher than in winter or spring.