村镇面源氮磷污染及其蓄积影响规律研究

Nitrogen and phosphorus non-point source (NPS) pollution particularly its accumulation caused by point sources is very serious at the beginning of the rainy season in suburb towns and villages. This problem has become the primary causes of deterioration in water quality at the beginning of the rainy season in China. However, little scientific research has been done in this area. This project aims to study nitrogen and phosphorus NPS pollution and its accumulation effects in Sijiao, a village located inside the railfall catchment area of Hedi Reservoir in Leizhou Peninsula of Southern China. The studies will cover the followings: (1) Analyze the changes of nitrogen and phosphorus concentration in rainfall streams down through woodlands, farmlands, orchards, and impervious underlying surfaces based on field experiments of nitrogen and phosphorus NPS pollution and the change characteristics of the accumulation pollution in representative rural areas. (2) Perform laboratory investigation on migration and conversion mechanism of nitrogen and phosphorus pollutants including accumulation pollutants in different underlying surfaces through artificial rain and large variable slope soil trough experiments under various conditions of rainfall amount and duration, slope, and added accumulation pollution to reveal the quantitative characteristics of pollution accumulation of nitrogen and phosphorus along rainfall runoffs.（3）Establish mathematic modeling for nitrogen and phosphorus migration and conversion characteristics according to field observations and results of indoor slope soil trough experiments; optimize the reservoir pollution loading model based on the discrete hydraulics and water quality models established by the authors. The study results can serve as the scientific basis for the analysis of the deterioration in water quality caused from the early rainwater. This work can also be applied for improving water quality of Hedi Reservoir as well as planning work for control mechanism of excessive nutrients.

村镇面源氮磷污染尤其是点源蓄积造成的蓄积污染在降雨初期较为严重，已是我国降雨初期水体水质恶化的主要因素，但研究工作开展尚少。本项目以湛江市鹤地水库集雨区内石角村为例，开展村镇面源氮磷污染及其蓄积影响规律研究。具体为：(1)开展农村典型小区氮磷面源污染和蓄积污染随径流变化规律的原位实验，分析流经林地、农田、果园及不透水下垫面的降雨径流中氮磷浓度变化规律；(2)在人工降雨、大型可变坡土槽的受控环境下，设置不同降雨量、历时、坡度及叠加蓄积污染物等条件，研究氮磷污染物（包括蓄积污染物）在不同下垫面迁移转换的机理，揭示氮磷蓄积污染物随降雨径流变化的规律；(3)基于野外监测及室内土槽实验结果，构建氮磷迁移转换规律数学模型；并以申请人已建鹤地水库分布式水文水质模型为基础，完善库区污染负荷模型。研究成果可为降雨初期水体水质恶化的成因分析提供科学依据，并可应用于鹤地水库水质改善及富营养化控制方案的制定工作。

村镇面源氮磷污染尤其是降雨初期形成的蓄积污染较为严重，是我国水体水质恶化和富营养化的重要因素。本课题在广东海洋大学后山120亩生态用地建立国家自然科学基金面源污染试验基地，开展了村镇面源氮磷污染及其蓄积污染随径流变化规律的大型野外试验；根据在蓄积污染池、农田污水池及双室混合池的监测结果，分析了蓄积氮磷污染在不同下垫面迁移转换的机理，并建立了定量关系；并以湛江市后坛村作为村镇典型小区，分别在林地、农田、果园等各类下垫面及集中排污口处开展原位监测，揭示了村镇林地、农田、果园的氮磷面源污染随降雨径流变化的规律。. 根据蓄积氮磷污染在土壤下垫面迁移转换的机理和氮磷面源污染随降雨径流变化的规律，结合人工降雨、大型可变坡土槽的实验结果，将不同土地类型的氮磷污染随地表径流的迁移转换规律采用定量公式进行表达，构建了相应的数学模型。在以上研究成果的基础上，结合课题组建立的鹤地水库分布式水文水质模型，进一步完善了鹤地水库库区初期降雨污染负荷模型，并在鹤地水库饮用水源富营养化控制和水污染防治工作中得以应用。本研究成果围绕我国氮磷面源污染研究的薄弱点，分析降雨初期水体水质恶化的成因，为控制面源污染提供了科学依据。