摘要
Agriculture is still the biggest contributor of non-point source (NPS) pollution to water bodies andrunoff discharges of nutrients and other chemicals are one of the most important pathways. This studywas conducted during 1998～1999 in a typical watershed with complex agriculture and forestry systems aswell as dotted farmer villages, in a transitional region between the mid- and northern subtropical zones ofChina. Continuous sampling of stream water was performed regularly at a weekly frequency, with additionalsampling after all major rainfall events. The discharges of N and P nutrients and suspended materials weremeasured and the total and area-averaged annual discharges of all components were calculated. The resultsshowed an uneven seasonal distribution of nutrient discharges with summer storms contributing most tothe total fluxes. This study demonstrated a high dependence of runoff volume on rainfall but the overallrunoff coefficients were dependent on land use type and watershed size. The area-averaged annual dischargesvaried greatly among the sub-watersheds with different sizes and land use structures. This is the first studyestimating the area-averaged annual discharges of N and P in the hilly areas of subtropical China, which were1.5 g m-2 a-1 and 0.1 g m-2 a-1, respectively, providing important reference values for the assessment ofregional agricultural non-point source pollution.
Agriculture is still the biggest contributor of non-point source (NPS)pollution to water bodies and runoff discharges of nutrients and other chemicals are one of the mostimportant pathways. This study was conducted during 1998～1999 in a typical watershed with complexagriculture and forestry systems as well as dotted farmer villages, in a transitional region betweenthe mid- and northern subtropical zones of China. Continuous sampling of stream water was performedregularly at a weekly frequency, with additional sampling after all major rainfall events. Thedischarges of N and P nutrients and suspended materials were measured and the total andarea-averaged annual discharges of all components were calculated. The results showed an unevenseasonal distribution of nutrient discharges with summer storms contributing most to the totalfluxes. This study demonstrated a high dependence of runoff volume on rainfall but the overallrunoff coefficients were dependent on land use type and watershed size. The area-averaged annualdischarges varied greatly among the sub-watersheds with different sizes and land use structures.This is the first study estimating the area-averaged annual discharges of N and P in the hilly areasof subtropical China, which were 1.5 g m^(-2) a^(-1) and 0.1 g m^(-2) a^(-1), respectively,providing important reference values for the assessment of regional agricultural non-point sourcepollution.
基金
Project supported by the International Foundation of Science(No.C/2661-1)
the National Key Basic Research Support Foundation of China(No.G1999011809).
