中高纬冻融区农业非点源污染中磷富集机制及其时空变化规律研究

The accumulation of agricultural non-point source phosphorus is caused by large-scale agricultural exploitation and seasonal freeze-thaw effects, which has seriously affected the agricultural development of China's mid-high latitude freeze-thaw zone. The purpose of this subject is to study the accumulation mechanism and spatial-temporal variation of phosphorus under the effects of long-term agricultural development and seasonal freezing-thaw treatments by integrating remote sensing inversion in non-point source phosphorus transporting model, and incorporating laboratory simulation experiments with field in situ surveillance. The study site is located at 859 farm which is a typical agricultural exploitation area in China's mid-high latitude freezing-thaw zone. The research includes four parts. Firstly, investigate the response of phosphorus's balance to large-scale agricultural activities, through historical data collation, remote sensing inversion and field surveys. Second, combine in situ monitoring and laboratory simulation of freeze-thaw to create a phosphorus accumulation function between soil-water interface in mid-high latitude freezing-thaw zone. Then couple the response relationship and accumulation function above to eco-hydrological processes simulation to build a farmland non-point source phosphorus transport model that applied to mid-high latitude freeze-thaw zone. Finally, driving the model with multi-source remote sensing data, hydrological data and meteorological data to calculate phosphorus accumulation in the study area since 1965 and analyze the spatial and temporal variation. The research will innovate in studying the response of phosphorus's balance to large-scale agricultural exploitation, creating accumulation function of phosphorus in mid-high latitude freeze-thaw zone and using remote sensing data to drive the phosphorus transport model, it will provide a scientific basis for regional non-point source pollution control and grain security.

大规模农业开发和季节性冻融引起农业非点源污染中磷的富集，严重影响我国中高纬冻融区农业发展。课题以我国中高纬冻融区典型农业开发区-859农场为对象，将遥感反演与非点源污染磷迁移模型相耦合，实验室模拟与野外定点监测相结合，研究长期农业开发和季节性冻融作用下磷素富集机理及其时空变化规律。研究内容包括将历史资料整理、遥感反演和实地调查结合，研究农业开发中磷素平衡响应关系；通过原位监测和室内冻融模拟，建立中高纬冻融区磷素土水界面富集函数；并将磷平衡响应关系、磷素土水界面富集函数纳入到区域生态水文过程模拟中，构建中高纬冻融区农田磷污染物迁移模型；最后利用多源遥感、水文气象数据驱动模型，计算1965年来研究区农业非点源污染中磷的富集，分析时空变化规律。课题将在中高纬高强度农业开发对磷平衡作用机制、冻融区土水界面磷迁移机理和遥感驱动磷迁移模型方面作出创新，为区域非点源污染防治和区域可持续发展提供科学依据。

遵循项目申请书和任务书设定的研究内容和研究目标，项目实施的主要研究内容包括连续四年的原位观测实验与磷素土水界面迁移机理研究、中高纬度冻融区高强度农业开发对土壤磷平衡的影响机制研究和中高纬冻融区农业非点源污染中磷模拟计算与富集的时空变化规律分析。研究表明，中高纬度冻融区土壤磷素在水土界面富集状态与存在的磷素风险，三江平原土壤中磷素的含量显著上升，土壤中磷素存在富集现象，潜在土壤磷素淋溶风险的土地面积增加；在不同的土地利用类型中，耕地和水体面临的磷素淋溶风险最为显著。土地利用变化和过量的化肥输入改变了土壤中原有氮磷比。未来高强度农业开发区磷素管理不能只考虑磷素的限制性，同时也应该考虑磷素的累积和风险。总磷负荷强度在不同的土地利用类型和不同的土壤类型中是不同的。不同土地利用类型的平均总磷负荷强度排序为水田>旱地>湿地>草地>林地。不同土壤类型的平均总磷负荷强度可按降序排列：水稻土>沼泽土>白浆土>草甸土>黑土>暗棕壤。研究表明，气温是影响磷素田面水中磷素含量的主要因素。归一化植被指数可以作为水田田面水生长季营养元素的重要指示器，特别是对溶解性营养元素，比如硝态氮、铵态氮和溶解性磷素。利用土壤磷素流失五因子法分析得出磷素关键源区主要集中在耕地区域，并随时间发生空间迁移，年累积降雨量为土壤磷素关键源区的主要驱动因素。项目成果系统阐述了中高纬度冻融区水土界面土壤磷素富集机理、富集状态和富集驱动因子的研究。揭示了高强度农业开发对土壤中磷素平衡的影响机制，及其对与土壤磷素密切相关因子包括氮素、土壤碳和经植被生产力的影响。这些研究对中高纬度冻融区，特别是对作为国家重要商品粮基地的三江平原具有重要的科学意义和应用价值。