Polybrominated diphenyl ethers (PBDEs) in the Danjiangkou Reservoir, China: identification of priority PBDE congeners.

Although the production of polybrominated diphenyl ethers (PBDEs) has been phased out over the past decade worldwide, they are still potentially hazardous to the environment due to their persistence and toxicity. This study investigated the levels of 55 PBDEs in water and sediments from the Danjiangkou Reservoir, China. The levels of PBDEs were in the range of not detected (ND)-286.67 ng/L in water and ND-236.04 ng/g in sediments. BDE209 was the predominant PBDE congener and constituted 15-50% and 44-68% of the total PBDEs in water and sediments, respectively. Commercial pentaBDE products (70-5DE, DE-71) were the dominant source of tetraBDE, pentaBDE, and hexaBDE, while commercial octaBDE (79-8DE) and decaBDE (102E and 82-0DE) products were the main sources of nonaBDE and decaBDE in water. PBDEs in sediments mainly stemmed from commercial decaBDE products and combustion sources. BDE-209 posed high ecological risks to aquatic organisms and dominated the total ecological risks of PBDEs. No cancer risks and non-cancer risks were observed for PBDEs. A ranking method based on four criteria, i.e., detection frequency, concentration, ecological risk, and health risks, was proposed, and 17 PBDEs were identified as high priority PBDEs for future monitoring and management in the Danjiangkou Reservoir.

Occurrence and removal of antibiotics and antibiotic resistance genes in natural and constructed riverine wetlands in Beijing, China.

Simultaneous elimination of antibiotics and antibiotic resistance genes (ARGs) is rarely investigated in full-scale riverine wetlands. Here, we compared the occurrence, abundance, and removal of 60 antibiotics and 27 ARGs in natural (Yeya Lake (YL)) and constructed (Bai River (BR)) riverine wetlands in Beijing, China. The concentrations of antibiotics in YL wetland were ND-51.9 ng/L in water and ND-37.9 ng/g in sediments. Significantly higher concentrations were found in BR wetland (ND-546 ng/L in water and ND-118 ng/g in sediments), which locates at the downstream of a reclaimed water treatment plant. The abundances of ARGs in YL and BR wetlands were up to 5.33 × 105 and 8.41 × 105 copies/mL in water, and 1.60 × 107 and 4.67 × 108 copies/g in sediments, respectively. These results suggest that wastewater greatly contributes to the elevated abundance of antibiotics and ARGs in both water and sediments. Compared to summer, higher levels of antibiotics in water were found in winter due to the higher usage, slower attenuation and the limited dilution. But higher abundances of ARGs were found in summer than in winter, in accordance with the favored microbial growth at higher temperature as denoted by copies of 16S rRNA. Compared to BR wetland, YL wetland achieved better removal of antibiotics and ΣARGs, with average removal efficiencies of 70.0% and 87.5%. Antibiotics, ARGs and environmental factors showed strong correlations in water samples from YL wetland. However, in BR wetland that receives urban wastewater effluents, no correlation between antibiotics and ARGs was found although the distribution of antibiotics was affected by aquatic environmental factors. These results indicate that subinhibitory concentrations of antibiotics may stimulate the prevalence of ARGs in natural wetlands.

Antibiotics in water and sediments of Danjiangkou Reservoir, China: Spatiotemporal distribution and indicator screening.

Danjiangkou Reservoir is the largest artificial freshwater lake in China. The occurrence and spatiotemporal distribution of 77 antibiotics in water and sediment samples from Danjiangkou Reservoir were investigated. Approximately 90% of the detectable concentrations of the 61 and 54 antibiotics found in water and sediment samples were lower than 5.0 ng/L and 1.0 ng/g, respectively. Sulfamethoxazole was the most abundant antibiotic found in water (1.65-149 ng/L, median 6.25 ng/L). In sediment samples, macrolides were frequently detected (42.7-54.5%) at concentrations of ND-4.34 ng/g. Greater diversity and higher levels of antibiotics were generally found in both water and sediment samples in spring than in the other seasons. Composition profiles of antibiotics differed between the two tributary river basins of Danjiangkou Reservoir, indicating different sources of contamination and the influence of water and sediment properties. Four criteria, namely widespread occurrence, correlation with the total antibiotic concentration, and risk to aquatic organisms or to human health, were suggested to select specific indicators for monitoring and pollution control of antibiotics. Five antibiotics were selected as appropriate indicators for Danjiangkou Reservoir, namely sulfamethoxazole, trimethoprim, clarithromycin, roxithromycin, and anhydrochlortetracycline. This study adds to the understanding of the occurrence of antibiotics in water reservoirs and can assist authorities in regulating antibiotic contamination and designing effective strategies for risk minimization.

A duodecennial national synthesis of antibiotics in China's major rivers and seas (2005-2016).

The occurrence of 94 antibiotics in water and sediments from seven major rivers and four seas in China during 2005-2016 was reviewed. Twelve antibiotics were most frequently detected in both water and sediment samples, including 3 sulfonamides (SAs), 2 tetracyclines (TCs), 4 fluoroquinolones (FQs), and 3 macrolides (MLs). Their median concentrations were below 100ng/L and 100ng/g in river water and sediments, respectively. The highest median concentrations were found in water (1.30-176ng/L) and sediments (0.15-110ng/g) in the Hai River, due to its larger population density, higher consumption of antibiotics, and lower water flow. The concentrations of TCs and FQs were higher in the Pearl River sediments, due to their extensive use in aquaculture. The Yangtze River showed lower median concentrations of antibiotics in both water (1.33-17.3ng/L) and sediments (0.31-14.8ng/g), resulting from its larger catchment size, and higher precipitation and water flow. The Yellow River exhibited lower median concentrations of antibiotics in sediments (0.04-9.04ng/g), probably due to low organic matter content in sediments and high suspended particle content in water. Organic carbon normalized distribution coefficients (Koc) of antibiotics were positively correlated with the octanol/water partition coefficients (Kow) of antibiotics, and the correlation for MLs with a macrocyclic lactone ring was different from that of SAs, FQs, and TCs, likely due to their much larger molecular size. Among China's major rivers, the Hai River had the highest ecotoxicological risk from antibiotics to algae, invertebrate, fish, and plant.

Antibiotics in water and sediments of rivers and coastal area of Zhuhai City, Pearl River estuary, south China.

The occurrence, spatiotemporal distribution and ecological risks of 27 antibiotics in water and sediments from rivers and coastal area of Zhuhai, Pearl River estuary, south China were investigated. Higher concentrations of antibiotics were found in river water in dry season than those in wet season (p < 0.01), especially for quinolones (QNs) (6.36-463 ng/L) and aminoglycosides (AGs) (94.9-458 ng/L). In coastal water samples, the concentrations of antibiotics were up to 419 ng/L and 357 ng/L in dry season and wet season, respectively. Higher concentrations of antibiotics in coastal sediment samples were observed in wet season compared with those in dry season (p < 0.01). This may be ascribed to the greater discharge of antibiotics from mariculture and surface sediment flushing in wet season, leading to the accumulation of polluted sediments in the estuary. Redundancy analysis showed that the concentrations of antibiotics in water were correlated with biological/chemical oxygen demand, ammonia nitrogen, and/or total nitrogen (TN). In addition, sediment organic matter (SOC) and TN strongly affected the distribution of antibiotics in sediments. Ecological risk assessment based on risk quotients (RQs) indicated that most antibiotics in water samples posed insignificant risk to fish and green algae, and insignificant to medium risk to daphnid.