The Water Environmental Characteristic And Its Evolutionary Trends Of Poyang Lake

With the rapid development of economy and society, the water demand and deterioration of water environment has become more and more serious, which severely restricted the development of world economy. Currently, the problems of water resources missing and water environment depravation were increasingly outstanding, and human activities were one of the main driving factors. Reflects this, comprehensively systematically studied the water environmental characteristic and its evolutionary trends of Lake, appears extremely essential, and the conclusions would provide a scientific basis for water resources protection and management.In recent years, the Poyang Lake water area shrinking, causing serious soil erosion, siltation of rivers and lake, river and lake bed elevation, resulting in Poyang Lake flood storage capacity greatly reduced, more and more Lakes region frequently flooded, and it showed a trend of gradually increasing. Poor agricultural production and land use patterns, the increasingly serious air pollution and the large number of pesticide and fertilizer application, cause the increased input of the nutrients into the lake (such as nitrogen, phosphorus, etc.) and POPs, the deterioration of water environment.Base on the international cooperation projects of water environmental and biodiversity study in Poyang Lake area, the national natural science funds of researching isotopes hydrology in edge deep-water zone of Poyang Lake as well as environment protection and the comprehensive exploitation and utilization of resources in Poyang Lake which has become a central topic for social and economic development in Jiangxi Province, this paper taken Poyang Lake Basin as an example. This dissertation had systematically researched the water chemical characteristics, geochemical characteristics, water quality, hydrologic characteristic, and the evolutionary trends of water environmental. The result revealed the spatial-temporal distribution characteristics of water chemical, the characteristics of water circulation, the characteristics of geochemical.Based on analyzed the status of the water environment and water quality, its water environment evaluation function of Poyang Lake Basin; the characteristics of nutrient salt, its seasonal variation, and the main sources and transport mechanism of water pollution of edge water; the factor of evolutionary trends of water environmental, this dissertation provided a better insight into contributing issues as well as suggestions for future exploitation in the area.The main conclusions have been summarized as follows:The pH of Water in Poyang Lake Basin was slightly acidic to alkaline and the buffer action of acid and alkali were strong; the electrical conductivity of water was below average of the world river. The average salinity in water of Poyang Lake district was 75.5mg/L. According to the distribution of water hardness, hardness in the lake of central was higher than stream outlet. The main hydrochemical type of Poyang Lake was type of, followed by, and then. Ca2+ was the dominant cation, accounted for more than55% of total cations respectively and HCO3-,SO42- was the principal anions. Minerals weathering play a controlling role in chemical composition of Poyang Lake Basin. The concentration of 87Sr/86Sr of lake outlet was higher than lake region and the marginal zone was much less than the deepwater area, while the center of deepwater area was on the high side.From an overall perspective, the isotopic composition of the Poyang Lake was in the range -6.5‰—4‰, and it has no obviously annual change. The isotopic composition of Ganjiang River approached snowprecipitationline, which relevant to year-round high temperatures, plenty of water and Broad valley. The stable isotopes were significantly different between the high water period, low water period and average flow period. The concentration of the isotopes in marginal zone was higher than the central region and the concentration of isotopes was the highest in the small lakes of the margin of Poyang Lake.Poyang Lake was polluted by N and P, which had subjected to eutrophication status at some extent. The eutrophication in Poyang Lake Basin will be heavier and the low water Period was more serious than the high water period. The Poyang Lake nutrients came mainly from five branches. The heavy metal pollution of water environment was light, however, heavy metal can transform in the system of water-sediment and enrich in aquatic plants and aquatic organism. Based on analyzed organochlorine pesticides, the results showed that the pollution was not serious, and DDTs in water and sediment may be derived from recent inputs, except having the use of the aged agricultural. Water environmental function and the water environmental quality appraisal showed that the nature reserve of water and landscape water had been seriously polluted, followed by fishery water, and other water was relatively good.The major ions of edge water were mainly derived from the weathering of carbonate rock. The water circle of edge water was obviously different from river water and lake water, as the main source of water was the surface runoff and rainfall, which results in water, could not be exchanged with outside environment. The concentrations of nutrients were increased year by year, at which had subjected to eutrophication. Isotopic studies suggested that the industrial sewage, life sewage, agricultural wastewater, and soil erosion were the main sources of water pollution.Temperature in Poyang Lake Basin tended to raise, in addition, the amount of water tended to decrease. Poyang Lake water level was expected to continual dropping, and water environmental gradually deteriorates. For the letting out of a large volume of industrial sewage, life sewage, and agricultural nonpoint source pollution had increased gradually, it will cause water quality malignization, make aquatic ecosystem structure destroy, weaken purification functional function of lake, and then lead to a series of environmental problems.Combined with the actual situation and the conclusions of Poyang Lake Basin, the theoretical conclusions have been summarized as follows:Eutrophication was the most serious problem in the seasonal lake with abundant rainfall, agricultural development, and industrial backwardness. The construction of water conservancy facilities, city development and economy development had a prominent impact on water environment. The water quality, hydrologic characteristic, and water circulation of edge water was obviously different from river water and lake water, while they had the similar hydrochemical type. The concentrations of nutrients were increased year by year, and studies suggested that the industrial sewage, life sewage, agricultural wastewater, and soil erosion were the main sources of water pollution. The odds were higher that eutrophication and the dispersion of schistosomiasis of edge water than river water and lake water.