紫色丘陵区典型小流域氮素迁移及其环境效应

选择四川盆地中部紫色土丘陵区典型小流域,通过2002～2004年3 a对主要土地利用地类氮素流失、小流域地表水和井水氮素迁移形态、途径与通量的连续观测,研究非点源氮素的来源、去向、迁移特征及其环境效应。结果表明,紫色土坡地氮素主要通过径流与泥沙迁移,坡耕地、居民点氮素流失是小流域非点源氮的主要贡献者,其氮素流失负荷分别为150．4kg、73．84 kg,占小流域氮素迁移总负荷的52．4％、25．7％；紫色丘陵区小流域地表水已呈现明显氮索富营养化特征,地下水硝酸盐污染较为严重,应重视该地区非点源污染控制；小流域氮素迁移的尺度差异明显,坡地以颗粒态氮为主,小流域以硝酸盐为主,氮素迁移的尺度效应可能导致非点源氮污染的异地效应,从而加剧长江三峡水体富营养化压力。

Non-point-source Nitrogen Movement and Its Environmental Effects in a Small Watershed in Hilly Area of Purple Soil

A typical small watershed in hilly area of purple soil in the centnd Sichuan Basin was selected for moni- toting of nitrogen movement. Continuous orientation-observations had been conducted from 2002 through 2004 to monitor nitrogen distribution in runoff,sediment,surface and ground water. Furthermore,we could know nitrogen forms and loads in different moving passes so as to find out characteristics of non-point-source nitrogen pollution and impacts on water environment. Results showed,nitrogenloads from slope cropland and residence accounted for 52.4% and 25.7% of total nitrogen loads in the watershed,indicated slope cropland,residence were main contrib- utors for non-point-source nitrogen in the watershed. Total nitrogen of surface water in this watershed averaged to 2.58 mg/L showed obvious eutriphication. Nitrate nitrogen of the ground water reached to 10.55 mg/L averagely which could not be used as drinking water based on WHO threshold (10.0 mg/L). Scale effects of monitoring showed evidently resulted in contents of nitrogen forms especially particulate and nitrate nitrogen changed a lot from runoff plots to outlet of the watershed. Our research suggests that non-point-source nitrogen pollution is very serious in the hilly area of purple soil and brings to great pressure to local water environment. However,non-point-source nitrogen maybe imposes to water en- vironment of Yangtze River and Three Gorges Reservoirthrough long distance travel of soluble nitrate.