抄録
We surveyed agricultural practices together with nitrogen concentrations in groundwater in Yanbian, Jilin, China. The nitrogenous fertilizer input into the 20 fields investigated was 100- 2190 kg-N/ha/year, (490-2190 kg-N/ha/year for vegetable fields). The nitrogen concentration was found to vary widely in groundwater beneath fields. In respect of nitrate, 65 % of sites exceeded the drinking water standard of 10 mg-N/L. Total nitrogen concentration in river water ranged from 0.7 to 12.6 mg/L; while a higher concentration was seen near Yanji city, as the river went downstream into Tumenjiang the concentration decreased. Using the statistical data, the total nitrogen loads to the water environment of the Yanbian area were estimated to be about 6.4×104 ton-N/year (0.29 ton-N/ha/year). Assuming that this amount of nitrogen goes into water in the environment without any depletion such as by denitrification, the average concentration of nitrogen in the surface water in this area was estimated to be about 12.4 mg/L. Although not so severe nitrogen water pollution is seen in this area, the nitrogen concentration in environmental water may increase in the future. Thus, careful monitoring and nitrogen load management are desirable.
