长江经济带农田氮素平衡特征与污染风险评估分析

Characteristics of Nitrogen Balance Model and Pollution Risk Assessment in Yangtze River Economic Zone

以长江经济带11省市作为研究对象,利用农田生态系统氮素平衡模型对研究区129个地级市氮素输入输出情况进行估算,分析了氮素盈余的空间分布特征。在此基础上耦合坡度、年度侵蚀性降雨量、侵蚀性降雨天数、距离河流距离、农田氮素盈余量等因子确定了农田氮素污染风险等级。结果表明:2015年研究区农田生态系统氮素输入总量为1.809×107 t,输出总量1.392×107 t,盈余量为4.177×106 t,平均盈余态氮养分负荷为87.5 kg·hm−2;湖北、云南、四川等省盈余总量均超过5.0×105 t,而上海、江西、安徽等省份较小;单位面积盈余量较大区域主要分布在云南省、湖北省大部、江苏省北部及湖南省中南部地区。氮素利用效率结果显示研究区氮素利用效率较低,与世界农业发达国家相比仍停留在过去粗放式发展的模式中。从风险等级角度来看,研究区整体处于氮素污染高风险状态,高风险及极高风险区占比达64.1%,尤其以重庆、贵州、云南等省市为甚。通过与北方地区氮素污染潜势结果对比分析,可以看出研究区内由于河网密集、侵蚀性降水强度大以及坡度较大等因素的影响而导致其污染等级远高于北方地区。该研究明确了2015年长江经济带氮养分平衡状况以及污染风险等级的空间分布特征,对于解决农业面源氮污染防治具有重要的理论和现实意义。

In this study,11 provinces in Yangtze River economic zone have been selected to conduct quantitative estimate and analysis of N nutrient input-and-output and spatial distribution for 129 prefecture-level cities by utilizing agro-ecosystem N nutrient balance model.Factors including slope,annual erosive precipitation,erosive rainfall days,distances from the river and agro-ecosystem N nutrient surplus were coupled with model outcomes to obtain the agro-ecosystem N nutrient pollution risks.The result demonstrated that the total amount of N nutrient inputs were 1.809×107 t,the outputs were 1.392×107 t,the surplus were 4.177×106 t and the average nutrient balance load was 87.5 kg·hm−2.The surplus in Hubei,Yunnan and Sichuan were over 5.0×105 t,while the surplus was comparatively small in Shanghai,Jiangxi and Anhui.Surplus per unit area in Yunnan,Central Hubei,Northern Jiangsu and South-Central Hunan were higher than other regions.The efficiency analysis results indicated that the nitrogen utilization efficiency in study area was low compared with agricultural well-developed countries around the world,and our study area still stayed in rough development mode.From the perspective of risk level,the risk of study area was high and high-risk and extreme high-risk areas proportion was 64.1%which included Chongqing,Guizhou,and Yunnan.By comparing with nitrogen pollution potential analysis in the northern region,dense river networks,large erosive precipitation intensity,and large slopes were the main reasons resulted in higher N nutrient pollution risks.Furthermore,N nutrient balance budget and spatial characteristics of pollution risk are analyzed which is able to provide theoretical and practical helps in N nutrient pollution control.