摘要
土地利用方式影响流域氮输入的空间分布和氮素的迁移输出过程,与非点源污染的防治密切相关。本文利用加州San Joaquin流域数据,考虑不同土地利用方式的影响,在GIS平台上分析了流域氮输入与输出的关系及其空间分布。本文提出了一个新的指标(F=CN/(L/Q))来衡量河流氮输出的变化趋势,该指标综合考虑了田间产流和河道输移两个过程的影响因子,能够描述土地利用类型对流域氮素迁移转化的影响。在实例研究中,通过该指标能够指示出研究区氮素流失的高风险区,为流域土地利用规划和非点源污染防治提供了重要的科学依据。
Land Use influences the spatial distribution of nitrogen（N） inputs in watersheds and the transporta-tion of N to rivers,and is therefore closely related to non-point pollution.Here we took San Joaquin Valley,one of the most important agricultural areas in the United States,as an example to analyze the impacts of land use on input and riverine N export in this area.Total N loads were monitored at five mainstream sites and four trib-utary sites along San Joaquin River.The spatially explicit calculation of N inputs for the nine corresponding watersheds was conducted with GIS（Geographic Information Systems）.The inputs were calculated as the sum of inorganic fertilizer,organic manure,atmospheric deposition,natural fixation,and crop fixation.The N in water removal and harvest was subtracted.Results showed that total N inputs ranged from 3607 to 12301 kg km-2 yr-1,among which inorganic fertilizer（42%-65%） and organic manure（26%-48%） were the largest sources.The pro-portion of N inputs exported through rivers ranged from 0.1% to 8.87%.A new index：F= LC/NQ was developed to characterize the variability of the fractional N export from the wa-tersheds.CN（Curve Number）,an empirical parameter from SWAT（Soil and Water Analysis Tool）,was used to represent in-field yield of N in agricultural areas.Larger CN indicates larger potential to produce runoff that flushes N into the receiving river channels.L/Q（L： Rivermile,Q： Streamflow） was used to represent the N trans-port processes in river channels.Regression analysis showed that there was a strong linear correlation between F and fractional N export.The index F has the advantage in using readily available factors to predict trends of N loads in areas which have similar climate and landscape.Using the product of F and rate of inorganic fertiliza-tion,agricultural fields that have high risk of N pollution were identified.The larger value of IFR.F indicates in-tensive fertilizer application and high runoff potential.We suggested that management and monitoring practices should be applied intensively in these areas.
出处
《地理科学进展》
CSCD
北大核心
2010年第9期1081-1086,共6页
Progress in Geography
基金
国家水体污染控制与治理科技重大专项(2008ZX07010-006-6)
温州基金项目(XNK07035)
