Emission Control in River Network System of the Taihu Basin for Water Quality Assurance of Water Environmentally Sensitive Areas

Ecological risk assessment under the PSR framework and its application to shallow urban lakes

Shallow urban lakes are naturally vulnerable to ecosystem degradation. Rapid urbanization in recent decades has led to a variety of aquatic problems such as eutrophication, algal blooms, and biodiversity loss, increasing the risk to lake-wide ecological sustainability. Instead of a simple binary assessment of ecological risk, holistic evaluation frameworks that consider multiple stressors and receptors can provide a more comprehensive assessment of overall ecological risk. In this study, we analyzed a combined dataset of government statistics, remote sensing images, and 1 year of field measurements to develop an index system for urban lake ecological risk assessment based on the pressure-state-response (PSR) framework. We used the developed ecological safety index (ESI) system to evaluate the ecological risk for three urban lakes in Jiangsu Province, China: Lake Yangcheng-LYC, Lake Changdang-LCD, and Lake Tashan-LTS. LYC and LTS were classified as "mostly safe" and "generally recognized as safe," respectively, while LCD was assessed as having "potential ecological risk." Our data suggest that socioeconomic pressure and aquatic health are the two main factors affecting the ecological risk in both LYC and LCD. The ecological risk of LTS could be improved more effectively if regional management plans are well implemented. Our study highlights the pressure of external wastewater loading, low forest-grassland coverage, and lake shoreline damage on the three selected urban lakes. The findings of this study can inform watershed management for lake ecosystem restoration and environmental sustainability.

Insights into antibiotic stewardship of lake-rivers-basin complex systems for resistance risk control

Antibiotic stewardship is hindered by a lack of consideration for complicated environmental fate of antibiotics and their role in resistance development, while the current methodology of eco-toxicological risk assessment has not been fully protective against their potential to select for antibiotic resistance. To address this problem, we established a novel methodologic framework to perform comprehensive environmental risk assessment of antibiotics in terms of resistance development, which was based on selection effect, phenotype resistance level, heteroresistance frequency, as well as prevalence and stability of antibiotic resistance genes. We tracked the contribution of antibiotic load reduction to the mitigation of environmental risk of resistance development by fate and transport modeling. The method was instantiated in a lake-river network-basin complex system, taking the Taihu Basin as a case study. Overall, antibiotic load posed no eco-toxicological risk but an average medium-level environmental risk for resistance development in Taihu Lake. The effect of antibiotic load on resistance risk was both seasonal-dependent and category-dependent, while quinolones posed the greatest environmental risk for resistance development. Mass-flow analysis indicated that temporal-spatial variation in hydrological regime and antibiotic fate together exerted a significant effect on antibiotic load in the system. By apportioning antibiotic load to riverine influx, we identified the hotspots for load reduction and predicted the beneficial response of resistance risk under load-reduction scenarios. Our study proposed a risk-oriented strategy of basin-scaled antibiotic load reduction for environmental risk control of resistance development.

Study of ecological compensation in complex river networks based on a mathematical model

Transboundary water pollution has resulted in increasing conflicts between upstream and downstream administrative districts. Ecological compensation is an efficient means of restricting pollutant discharge and achieving sustainable utilization of water resources. The tri-provincial region of Taihu Basin is a typical river networks area. Pollutant flux across provincial boundaries in the Taihu Basin is hard to determine due to complex hydrologic and hydrodynamic conditions. In this study, ecological compensation estimation for the tri-provincial area based on a mathematical model is investigated for better environmental management. River discharge and water quality are predicted with the one-dimensional mathematical model and validated with field measurements. Different ecological compensation criteria are identified considering the notable regional discrepancy in sewage treatment costs. Finally, the total compensation payment is estimated. Our study indicates that Shanghai should be the receiver of payment from both Jiangsu and Zhenjiang in 2013, with 305 million and 300 million CNY, respectively. Zhejiang also contributes more pollutants to Jiangsu, and the compensation to Jiangsu is estimated as 9.3 million CNY. The proposed ecological compensation method provides an efficient way for solving the transboundary conflicts in a complex river networks area and is instructive for future policy-making.