The Deep Challenge Of Nitrate Pollution In River Water Of China

Nitrate pollution of surface water has attracted global attention, and the issue is becoming increasingly significant in China. To identify the pollution status, sources, and potential non-carcinogenic health risks of nitrate in China's river water, nitrate data from 71 major rivers from 30 provinces were systematically collected. The spatial distribution of nitrate concentrations in river water was analyzed, and the main nitrate pollution sources were revealed based on the presence of nitrogen and oxygen isotopes of nitrate. The results show that approximately 7.83% of samples in China exceeded the national drinking water standard for nitrate (45 mg/L). The concentrations of nitrate in Mudan River (Linkou County), Haihe (Beijing), and Yangtze River estuary (Shanghai) exceed 90 mg/L, which indicates severe pollution. The characteristic values of delta N-15 and delta O-18 of river water in China range from -23.5 parts per thousand to 26.99 parts per thousand and - 12.7 parts per thousand to 83.5 parts per thousand, indicate many sources including inorganic fertilizer, soil nitrogen, wastewater or manure. The primary sources of nitrate in river water of Northeast, Northwest, Southwest, and South China were manure, septicwaste, inorganic fertilizer, and soil organic matter nitrification. Manure and septic waste were the major source of nitrate in Central, East, and North China. Correlation analysis revealed that the nitrate concentrations of surface water has a positive relationship with GDP, nitrogen fertilizer application usage, wastewater discharge, and population in China. Non-carcinogenic risk of nitratewas identified in 80% of the regions in China, and potential moderate non-carcinogenic risk areas are Shanghai, Beijing, and Shaanxi. It is urgent to solve the problem of pollution and prevent the further pollution of China's river water. Though the new "10-point Water Plan" issued by the Chinese government solved previous problems, it will take decades to control and repair polluted surface water. (C) 2021 Elsevier B.V. All rights reserved.