基于流域单元的海湾农业非点源污染负荷估算研究——以莱州湾为例

Abstract

The control of total amounts of pollutants has become an important measure for controlling water pollution in China and is also an important basis for objective management of water resources. Estuary is one of the regions where the productivity and biodiversity are higher and is utilized by human earlier. Estuary is one of the most valuable ecosystems in the world that has attracted human' s increasing attention. Furthermore,estuary is the most sensitive zone to respond to global changes and a place where the most vigorous interactions between land and sea take place. Estuary is the region where human activities take place more frequently. In particularly,estuaries are the places where a number of rivers enter into seas and receive a large amount of pollutants from lands and human' s life activities. Thus,estuary and coasts are vigorously disturbed by human activities. Conducting research on controlling total amounts of pollutants that enter estuaries from lands is of great significance for protecting marine environment,maintaining ecological health,promoting coastal economic development,rationally utilizing marine resources,and for achieving sustainable development of marine economy. Total amount of pollutants that enter seas is an important index for protecting estuary environment. Because numerous rivers flow into estuaries,estimation of total pollutants brought by rivers into sea is influenced by such factors as monitoring frequency and seasonal changes in flow rates. The agricultural non-point source pollution is an important source of pollution load that enter the estuaries in China. Based on DEM( SRTM Data with 90m resolution) and with the help of Arc Hydro module in ARC / INFO software developed by ESRI company,we conducted hydrological analysis on major rivers that enter Laizhou Bay by using GIS to extract river network,define watershed boundaries and divide the catchments and sub-watered, aiming to provide the basic data platform for estimation of total amounts of pollutants from agricultural non-point pollution. On this basis,we calculated the areas of different types of land use in various sub-basins by overlaying them with land-use thematic map,and estimated total amounts of agricultural pollutants entering into sea by using emission factors and river load ratio of major pollutants. Our results revealed that the annual amounts of COD,NH 3-N,TN and TP that entered into Laizhou Bay was about 666994,94398,114614 and 19574 tons,respectively,accounting for 74. 48%,10. 54%,12. 80% and 2. 18% of total amounts of released pollutants,indicating COD is the major pollutant that enters Laizhou Bay. This studied was planned and conducted under the guidance of the principle of cooperation between land and sea,by taking the estuary as the source and with the idea of tracing sources,to determine watershed unit that influence marine pollution load. This study could provide an estimation method of agricultural non-point source load and the a scientific basis for controlling total amounts of pollutants that flow into Laizhou Bay,and can also serve as a reference for defining the land range during the process of comprehensive management along the coastal zone.