Analysis and evaluation on the nitrogen pollution in the upper reaches of Ganjiang River

To study the distribution of water pollution in the upper Ganjiang-Taojiang River basin, based on 167 water samples collected in the Taojiang River Basin (in normal water) period, it was determined by on-site and indoor analysis, and the comprehensive pollution index and single-factor pollution index evaluation method were used to assess the nitrate in the watershed. The ammonia and nitrogen pollution status was evaluated. The results showed that: ① The pH value of the main stream of Taojiang River and most of its tributaries are within the limits of surface water environmental quality standards, but 4 of the 17 sampling points in Lianjiang River were affected by small power stations and wineries whose pH value was lower than the standard limit of surface water; ② Nitrous nitrogen was easily oxidized, which was the reason for the lower nitrous nitrogen content in the basin. The concentration of nitrite nitrogen in some areas of the upper reaches of the main stream was slightly higher, the water quality of the Wojiang River and the Lianjiang River was poor, and the river water was in an anoxic or anaerobic state with higher concentration; ③ The overall over-standard rate of nitrate and nitrogen in the basin was 31.7%. Affected by mining areas and livestock and poultry farms, the coefficient of variation of nitrate and nitrogen in the Longjing River and Lianjiang River was large and exceeds the standard seriously which the exceed ratios were 73.3% and 70.6% respectively; ④ Rare earth mines in the basin were widely distributed and had a large number. The use of chemicals such as ammonium sulfate and ammonium bicarbonate, which were widely used in large quantities in the mining and beneficiation process, made the ammonia nitrogen pollution the most serious, and all of them exceeded the surface ammonia nitrogen limit of Class Ⅲ water, among which Grade Ⅲ~Ⅳ water accounted for 51.5%, Grade Ⅳ~Ⅴ water accounted for 8.4%, and water inferior to Grade Grade Ⅴ accounted for 40.1%.