近30年中国农业源氮磷排放的格局特征与水环境影响

揭示农业源氮磷排放的空间格局、变化特征及其与水环境状况的关系,对于农业面源污染治理投入的合理配置以及区域农业生产结构优化均至关重要。基于这种认识,建立参数化估算模型测算了1990—2017年中国省域尺度的农业源氮磷排放;从总排放量、单位面积排放量和排放重心迁移三个方面研究农业源氮磷排放的变化特征,并通过相关分析与回归分析揭示农业源氮磷排放与水环境状况的关系。研究发现：1990—2017年中国农业源氮磷排放整体上呈随机分布,表明氮磷排放在省际之间并无显著的相互依赖性,主要受省内因素影响。研究期内年均氮磷总排放量最高的省份依次是河南、山东、四川、湖北、河北、安徽和江苏省,格局特征相对稳定但排放重心经历了东西向的往复式转移并具有北偏西方向的总体转移趋势,其中,氮、磷排放的重心分别向北偏西33.52°和15.45°方向转移了33.94 km及52.31 km。在格局研究基础上,结合空间维的格局特征和时间维的变化特征,将31个省份的氮磷排放划分为高排放增长型、高排放平稳型、高排放倒“U”型、中排放增长型、中排放倒“U”型、低排放增长型、低排放倒“U”型和低排放近似“U”型八类,并利用2017年的自动监测站水质数据进一步验证了氮磷排放与水环境状况的关系。研究结果可作为农业面源污染治理中重点区域瞄准的依据。

Spatial pattern and water environmental impact of nitrogen and phosphorus emissions from agricultural sources in China in recent 30 years

It is important and valuable to reveal the spatial pattern,changing characteristics of nitrogen and phosphorus emissions from agricultural sources and the relationship between them and water environment for rational allocation of investment in agricultural non-point source pollution control and optimization of regional agricultural structure.Based on this understanding,a series of parametric models were established to estimate the agricultural source nitrogen and phosphorus emissions in China from 1990 to 2017.Then,the changing characteristics of nitrogen and phosphorus emissions from agricultural sources were studied from three aspects including total emissions,nitrogen and phosphorus emissions per unit area and migration of emission center,and the relationship between nitrogen and phosphorus emissions from agricultural sources and water environment was revealed through correlation and regression analysis.The study found that the nitrogen and phosphorus emissions from agricultural sources in China were distributed randomly between provinces,indicating that there was no significant interprovincial dependence of nitrogen and phosphorus emissions,which were mainly influenced by internal factors of each province.Throughout the study period,the provinces with the highest annual total nitrogen and phosphorus emissions were Henan,Shandong,Sichuan,Hubei,Hebei,Anhui and Jiangsu provinces.The pattern was relatively stable,but the emission center experienced a reciprocating transfer from east to west and had an overall transfer trend in the northwest direction.Among them,the center of gravity of nitrogen and phosphorus emissions shifted 33.94 km and 52.31 km respectively in the direction of north by west 33.52°and 15.45°.Based on the pattern research and combined with pattern characteristics of spatial dimension and changing characteristics of time dimension,nitrogen and phosphorus emissions of 31 provincial-level regions were divided into 8 categories,namely,high emission growth type,high emission stable type,high emission inverted"U"shape type,medium emission growth type,medium emission inverted"U"shape type,low emission growth type,low emission inverted"U"shape type,and low emission approximate"U"shape type.Furthermore,the water quality data from automatic monitoring stations in 2017 were used to verify the relationship between nitrogen and phosphorus emissions and water environment.The results can be used as the basis for identifying key regions in agricultural non-point source pollution control.