Research On The Nutrient Loss Under Different Land Use In The West Of Taihu Lake Basin

Taihu Lake Basin is located in China's eastern region, one of domestic economical developed areas. Along with the rapid economic development, large amounts of pollutants disperse into the Taihu Lake, causing water quality of Taihu Lake continues to deteriorate. Particularly agricultural non-point source pollution has a large share. The paper taken shore different land use and near shore sediment in the west of Taihu Lake Basin as the research object. The paper had studied the soil and sediment characteristics and relations from the view of nutritive elements , and discussed movement tendency of nutritive elements, and evaluated the soil and sediment in study area.Nutritive elements of different land use types were significant difference. This was mainly due to the fertilizer and different nature of plants. Correlation analysis showed that the soil organic carbon and total nitrogen had better relevance, organic carbon and total phosphorus had the limited relevance. Total nitrogen and effective nitrogen, total phosphorus and effective phosphorus had shown better correlation in soil. The characteristics of distribution of pollution elements nitrogen and phosphorus in sediment displayed for Yixing > Huzhou > Changxing. Nutritive elements of shore sediment under different land use were significant different. Correlation analysis showed sediment the nutritive elements had better relevance, and it showed that the nutritive elements in sediment had close relationship.All the nutritive elements (organic matter, total nitrogen, total phosphorus, effective nitrogen, effective phosphorus), the average value of different land type sample were higher than the near shore sediment .It showed that the nutritive elements in loss soil dispersed into the water body. Nutritive elements of forest land and grass land in all the profit margin were less than mulberry land and cultivate land . It showed that the forest land and grass land in unit quality contributed less nutrients to the eutrophication of Taihu Lake, but mulberry land and cultivate land in unit quality contributed bigger rate to the eutrophication of Taihu Lake. The loss rate of nutrients for mulberry land declined more than other land use types. It showed that mulberry land in unit quality contributed more nutrients to the Taihu Lake. The average value of effective nitrogen proportion of different land samples decreased with forest land > mulberry land >grass land>cultivate land. But the average value of effective phosphorus proportion for different land samples decreased with mulberry land >cultivate land>grass land > forest land. Different land use in the west of Taihu Lake drain the total nitrogen load to the water body of Taihu Lake were 2092t/a, 934t/a, 644t/a, 67t/a for cultivate land, mulberry land forest land and grass land respectively; The total phosphorus load to the water body of Taihu Lake were 275t/a, 170t/a, 44t/a, 6t/a for cultivate land, mulberry land, forest land and grass land respectively.The supply of nutritive elements was extremely abundant, which was caused by over-fertilization. The nitrogen supply degree was better than other nutritive elements. This can greatly increase the potential risk of the non-point source pollution, especially the risk of nitrogen. The pollution of nutritive elements in sediment were not very serious , the order was Yixing country> Huzhou city> Changxing country.Based on the above fact and the conclusion and the correlative conferences, we calculated the year load quantity of total nitrogen and total phosphorus for different land use in the west region of Taihu Lake in this paper, and to provided the reference values in Taihu Lake area. The load quantity of total nitrogen and total phosphorus for different land use can provide important parameters for non-point source pollution model.