Non-point source pollution- Dissolved and solid pollutants are transported into the receiving waters (including rivers, lakes, and reservoirs) through runoff processes from non-specific locations under the action of precipitation (or snowmelt) and cause water eutrophication or other forms of pollution. Compared with point source pollution, non-point source pollution mainly consists of soil sediment particles, nitrogen, phosphorus and other nutrients, pesticides and other harmful substances, straw agricultural film and other solid waste, livestock and poultry manure sewage, aquaculture bait drugs, Rural domestic sewage garbage, various atmospheric particulate matter sedimentation, etc., are caused by surface runoff, soil erosion, farmland drainage, etc., and are characterized by dispersion, concealment, randomness, latentness, accumulation and ambiguity. Therefore, it is difficult to monitor, difficult to quantify, and difficult to study and prevent.
Non-point source pollution has two broad and narrow definitions: broadly refers to various environmental pollutions without fixed sewage outlets. The narrow sense is usually limited to non-point source pollution in the water environment, that is, surface runoff pollution accompanying the precipitation process.
1. The process of rainfall runoff formation, that is, the pollutants accumulated on the surface of the basin are washed by precipitation, and the pollution load is generated on the land slope along with the formation of runoff and sediment transport, and the transport of runoff and sediment in the basin Increase and decay, eventually reaching the river.
2. The process of soil erosion and sediment transport, that is, the migration and transformation process of non-point source pollutants in the river channel.
3. Contaminant conversion process.
The basic content of non-point sources of pollution survey –
Select all or part of the following to investigate according to the needs of the evaluation work:
(1) Overview of non-point pollution sources: the location of raw materials, fuels, wastes, the area of stacking, the form of stacking, the floor covering of the stacking place, the degree of cleaning, and the way of covering the piled objects.
(2) Discharge methods, discharge destinations and treatment of non-point pollution sources: It should be stated whether non-point source pollutants are organized or unorganized; whether they are discharged directly after concentration or after treatment, whether they are discharged separately or with production wastewater Or domestic sewage discharge together.
(3) Sewage data of non-point pollution sources: According to the existing measured data, statistical reports and the main water quality parameters selected according to the physical, chemical and biochemical properties of raw materials, fuels, wastes and wastes causing non-point source pollution, Investigate data on emissions seasons, emissions periods, emissions, emission concentrations, and other changes.