Background: Organochlorine pesticides (OCPs) are currently still threatening the ecological environment and people’s health. However, studies that investigate OCP pollution levels in an urbanized river network of an entire city with a high density of rivers, such as Shanghai, have rarely been reported. In addition, due to the pressure of high population densities, ecological risk and health hazard assessments of OCPs in river networks are a knowledge gap that needs to be urgently filled. Thus, in this study, the concentrations, distribution, and partitioning of OCPs are evaluated in an ecological and health risk assessment for the urbanized river network of Shanghai. The goal is to establish connections among OCP residues and establish their impacts on ecological and human health. Results: The concentrations of 26 OCPs in the urbanized river network of Shanghai ranged from 43.90 to 342.74 ng/L, with a mean value of 181.34 ng/L. Some OCPs formed triangle-shaped areas with higher local ecological risks than other areas, and there were nine OCPs of high risk in some areas. The health risk assessment results showed that the ranking of the incremental lifetime cancer risk (ILCR) for dermal contact according to age and gender was adults > children > seniors > adolescents, and females > males, while the ranking of the ILCR caused by mistaken oral intake was adults > children > adolescents > seniors, and females > males. The non-carcinogenic risk hazard index (HI) values of both exposure routes were less than one. Conclusion: OCP concentrations in the northern and southern regions of Shanghai were significantly higher than in other regions, and the partition coefficient (K_p) values of the ∑₂₆ OCPs were negatively correlated with the total suspended solids’ (TSS) contents (p < 0.01). The ecological risks were relatively higher in agricultural areas. The ILCR for dermal contact and mistaken oral intake were generally low, except for adults, whose ILCR caused by dermal contact were at moderate risk. In addition, OCPs in river waters did not pose significant non-carcinogenic health hazards for a majority of the people.

Bioremediation has been used as an environmentally-friendly, energy-saving and efficient method for removing pollutants. However, there have been very few studies focusing on the specific antibiotic-degrading microorganisms in the activated sludge and their degradation mechanism. Two strains of cefalexin-degrading bacteria ( Rhizobium sp. (CLX-2) and Klebsiella sp. (CLX-3)) were isolated from the activated sludge in this study. They were capable of rapidly eliminating over 99% of cefalexin at an initial concentration of 10 mg l ⁻¹ within 12 h. The exponential phase of cefalexin degradation happened a little earlier than that of bacterial growth. The first-order kinetic model could elucidate the biodegradation process of cefalexin. The optimized environmental temperature and pH values for rapid biodegradation by these two strains were found to be 30°C and 6.5–7, respectively. Furthermore, two major biodegradation metabolites of CLX-3, 7-amino-3-cephem-4-carboxylic acid and 2-hydroxy-3-phenyl pyrazine were identified using UHPLC-MS and the biodegradation pathway of cefalexin was proposed. Overall, the results showed that Rhizobium sp. (CLX-2) and Klebsiella sp. (CLX-3) could possibly be useful resources for antibiotic pollution remediation.

Yangtze River Basin (YRB) is the largest agricultural and economic corridor in Asia, accounting for 40 % of China's rice production and 49 % of its arable land. Additionally, the Huangpu River (HR), the largest river in Shanghai, features developed agriculture and an extensive shipping industry. Overall, extensive agricultural activities coupled with frequent pesticide applications have resulted in aquatic contamination. This study investigated the spatial distribution and partitioning trends of 57 common pesticides, and assessed their ecological and human health risks in 30 river sections of YRB. We found that the total concentration of pesticides (∑₅₇ pesticides) in the dissolved phase, suspended particulate matter (SPM) phase, and surface sediment ranged 601.82 -2415.91 ng/L, 65.04 -1863.28 ng/L, and 68.54 -424.84 ng/g dry weight, respectively. Organochlorines and pyrethroids were predominant in the SPM phase, while triazines and neonicotinoids were predominant in the dissolved phase. The sources of dichlorodiphenyltrichloroethane (DDT) substances could be attributed to historical residues and vessels' antifouling systems. Most pesticides had strong migration ability and were not readily deposited in sediment. Moreover, sediment was also potential secondary pollution sources of triazines. Organochlorines, pyrethroids, and neonicotinoids posed significant ecological risks, despite its low concentration, traditional organochlorine still poses a certain ecological threat. Children were more susceptible than adults to noncarcinogenic and carcinogenic risks from unintentional oral exposure. Stringent management of pesticides is imperative with ongoing monitoring.

Neonicotinoids are extensively used to prevent and control crop diseases and insect pests. Qilu Lake Basin is an important agricultural area in Southwest China, with huge consumption of neonicotinoids. However, the lack of data on neonicotinoid residues in Qilu Lake Basin challenges us with assessing the environmental contamination levels and the potential risks for the local aquatic ecosystem. Therefore, in this study, the occurrence and spatiotemporal distribution of three neonicotinoids (imidacloprid, clothianidin, and thiamethoxam) in surface waters of Qilu Lake Basin were investigated. Their concentrations ranged from 0.65 ng/L (thiamethoxam in spring) to 1041.21 ng/L (imidacloprid in summer), which exhibited decreasing trends from the surrounding rivers to Qilu Lake. The highest concentrations were observed in summer, owing to the intensive application of pesticides and the heavy precipitation and surface runoff in this season. Imidacloprid and thiamethoxam presented relatively high ecological risks, and clothianidin was the most threatening compound, with high risk quotient values in every season owing to its low predicted no-effect concentration values and high toxicity.