三江平原高强度农业开发情形下土壤残留磷估算及其风险评价

Phosphorus is a key element to crop production. A large amount of artificial phosphorus was input to soil for satisfying the increasing food demand. Mass of artificial phosphorus accumulated in the soil due to intensive agricultural development, exceeding the requirement for the growth of crops, thus forming mass of residual phosphorus in the soil. Soil residual phosphorus plays an important role in the migration and transformation mechanism of phosphorus, it brings potential risk to the surrounding environment and it is also the main cause of the pollution. However, previous studies about the soil residual phosphorus mainly focus on the small spatial scale, and the risk of evaluation is still qualitative. The spatial and temporal distribution of soil residual phosphorus in the regional scale and long time series is still not clear, and the methods for evaluating the risk of soil residual phosphorus quantitatively need to be further studied. In this study, the Sanjiang Plain was selected to be the typical study area, a remote sensing driven model was constructed for estimating soil residual phosphorus from 2000 in the Sanjiang Plain, and its spatial and temporal variation were analyzed. The risk of soil residual phosphorus to the surrounding environment was evaluated quantitatively and the spatial and temporal distribution of risk areas was found. This research gives a help to understand the migration and transformation mechanism of soil residual phosphorus in the conditions of intensity agricultural development, and provides the basis for the prevention of the non-point source pollution and the development of green development strategy of the Sanjiang Plain.

磷是粮食生产所需的关键元素，为了应对全球不断增长的粮食需求，大量的人工磷肥被输入到农田土壤。高强度农业开发使得人工磷肥在土壤中不断累积，超过了作物生长所需要的磷含量，进而在土壤中形成大量的残留磷。土壤残留磷对磷素迁移转化机制有着重要影响，对周边环境产生潜在的风险，是农田面源污染最主要的诱因。然而，现有土壤残留磷研究主要集中在中小尺度，对其带来的风险仍以定性评价为主。区域尺度、长时间序列土壤残留磷的时空分布规律仍不清楚，定量评价土壤残留磷风险的方法需要进一步研究。课题以三江平原为研究对象，通过构建遥感驱动的土壤残留磷估算模型，获取三江平原2000年以来土壤残留磷含量，分析其时空变化规律；定量评价土壤残留磷给周边环境带来的风险，确定风险区的时空分布。课题研究结果有助于深入了解高强度农业条件下土壤残留磷的迁移转化机制，为三江平原面源污染防控和绿色发展策略制定提供依据。

高强度农业开发使得大量的人工磷肥在土壤中累积，超过了作物生长所需要的磷含量，进而在土壤中形成大量的残留磷。土壤残留磷对磷素迁移转化机制有着重要影响，对周边环境产生潜在的风险，是农田面源污染最主要的诱因。为了解决上述问题，本项目选择国家重要的商品粮基地三江平原为典型研究区，利用自主构建的遥感驱动生态水文模型EcoHAT-P计算了三江平原2000-2019年土壤磷含量，同时创建了该研究区基础信息数据库。应用模型计算结果和地理信息技术，分析了近二十年三江平原土壤磷的时空变化规律，利用阈值法确定了土壤磷淋溶的风险区，风险区主要集中于农业用地区。利用计算结果，分析了土壤磷流失的特征，在十年尺度内，流失磷年际变动幅度较大，变化趋势不稳定，其中在2013年流失磷含量为十年内最高，平均流失磷含量约为12 kg/ha，局部地区高于16 kg/ha，在2015年流失现象稍有缓解，呈现出耕地流失大于林草地的现象。采用无人机与高分卫星结合的方法，分析了微地形变化对土壤磷素累积和流失的影响，为土壤磷流失防治提供了技术支持。对比分析了土壤水原位观测数据、SMAP土壤水产品和模型计算结果，得出了这三种方式获取中高纬度冻融区土壤水数据的精度和能力。SMAP土壤水产品在冻融期和非冻融期有效数据提供率分别为27.1% 和57.5%；生态水文模型能够提供研究期内100%的数据，在中高纬度地区这三个土壤水数据集准确率的排序为SMAP>实测数据>模型计算结果。本项目第一次在三江平原计算了长序列（20年）土壤磷含量，同时分析了土壤磷含量的时空变化特征，确定了流失风险区；项目的开展为东北黑土地保护、三江平原粮食的高产稳产以及该地区面源污染防治提供重要的数据和技术支持。