Evaluation of Human Activities Impacts and Study on Species of Heavy Metals in Sediments of Dongjiu and Xijiu Lake, Inlet System of Taihu Lake Catchment, in the Past Century
|School||Nanjing Agricultural College|
|Keywords||Taihu lake Department Lake West Dongjiu Dongjiu Lake Lake sediments Human activities Heavy metal pollution Ecological Risk Chemical speciation Chronology Magnetic susceptibility|
The main rivers in this article on the Taihu Lake basin into the lake Department of Yili River into Taihu Lake before flowing through the two major lakes - Dongjiu sediment cores collected in the West Dongjiu. They DJ5 are the West Dongjiu Lake sediment into the lake at the XJ2 cores and Dongjiu of the lake the lake at sediment cores. The 210Pb isotope geochronology studies show XJ2 core covering the time range from the early 19th century to 2004, and the deposition rate over time rising. DJ5 core can not be applied 137Cs or 210Pb dating pollution stratigraphic control, in this paper we use the method to be dating, DJ5 core era is between the end of the 19th century to 2004. Over time in XJ2 low-frequency magnetic susceptibility and high-frequency magnetic susceptibility showed a trend of increased and then decreased, but the overall trends are gradually increased; frequency magnetic susceptibility exhibited a trend to decrease this variation showed that the impact of human activities on the lake gradually strengthened. XJ2 core magnetic susceptibility level change and human activities, especially the activities of pollution on the environment is closely related to the war and industrial development are the main factors to affect the magnetic susceptibility level of the present study. Through the analysis of XJ2 bottom of core heavy metal content, total and total West Dongjiu heavy metal background values ??effectively bound content get these background values ??is equally applicable to the study of Lake Dongjiu, Then they use the background value of the potential ecological risk index method the XJ2 and DJ5 core of heavy metal pollution and potential ecological risk index method to accumulate. At the same time also by XJ2 core based on the total evaluation methods and evaluation methods based on the total effective bound than research. Potential ecological risk assessment based on the total effective bound content with the curve based on the total amount of the potential ecological risk assessment similar trend, only individual elements of the order is different. Cd element in the comprehensive evaluation of the absolute dominant factor causing heavy metal contamination. Single pollution elements evaluation or comprehensive evaluation of a variety of pollution elements, as time goes on, the Cfi, Eri, Igeo, Cd, and RI have appeared first increased and then decreased. The local accumulation index method validation results show that the state changes in the content can more clearly determine the presence of contamination by heavy metals total effective combination, and not exaggerate the starting time of the element pollution, given the results more realistic. BCR three-step extraction of Cd, Cr, Zn, Cu and Pb elements in XJ2 and DJ5 various combinations of morphological analysis, five tested elements effectively combined with state content and the rise of the percentage of the full description of the man-made the presence of sources of pollution. Changes in total Cd, Cu, Zn and Pb, is by the total effective combination of state-led. In the past century, the measured elements effectively bound levels increased in varying degrees, their combined forms the vertical distribution of significant changes occurred, as time goes on, the core at the bottom of the main chemical speciation caused by anthropogenic emissions by sources replaced by a substantial increase in the form of natural chemical speciation balance is broken. Measured elements are water soluble, exchangeable and bound to carbonate content rising phenomenon, and of Cd, Zn, Cu and Pb in the form of percentage also appeared in a different rate of rise. These changes not only with the elements geochemical nature of the depositional environment, largely pollutant sources, features and content at the same time has a very close relationship. Heavy metals content changing trends and the history of human activity, especially within the catchment of industrial and agricultural production and transportation and other development history match. Water anthropogenic sources of heavy metal pollution in the sediments is easy being hosted in the secondary release risk, high Bioavailability effective bound potential ecological risk. The control study research indicators of heavy metal elements in DJ5 significant decline over XJ2 have. Largely by upstream runoff carries pollutants in downstream transport process, continuously deposited to thereby gradually result in water purification; while the the depositional environments difference between the east and west mountain spring lake, heavy metals geochemical properties and characteristics of pollution sources, pollutants, but also affect the two lakes sediments key factor in effective contents and distribution differences.