The Color, Rb/Sr Value And Environmental Significance Of The Sediments In The Niuyue Lake In The Middle Reaches Of The Yangtze River

In this paper,the characteristics of climate change in the short time scale（nearly70 years）in the oxbow lake district were analyzed by combining the magnetometric index,chromaticity（red degree,yellow degree）and Rb/Sr value of the sediment particle size of the Tian’e lake（TE）,zhongzhou（ZZ-2）and the Chiba lake（CB-1）in Jingjiang section of Hubei province.Using human activity coefficient（AF）and the geological accumulation index(I_geo)method to obtain the human activities on the lake of heavy metal pollution.The results are as follows:1.three drilling through the chromaticity and Rb/Sr value analysis can better instructions lakes short scale（nearly 70）climate characteristics.Bottom-up is divided into five stages:the first stage until the 1950 s,the climate is warm and humid to dry;The second phase in the 1950 s to 60 s,from dry to warm humid climate change;The third stage in the 1960s-70s,warm humid climate to warm and dry.The fourth stage of the 1970s-80s,by the warm and dry to mild moist climate change;The fifth stage in the 1980s-the 21st century,moderate to warm moist climate by wet to dry again.2.the sources of heavy metals in sediment is mainly atmospheric sedimentation and sewage discharge.（1）the Jianli and Shishou since 1978,the use of leaded gasoline,car exhaust emissions,car tire wear caused by heavy metals Pb and Zn by atmospheric precipitation in water,sediment concentration（2）increase in the number of Jianli and Shishou power plant and machinery factory,the factory fuel combustion gasification and exhaust emissions of pollutants such as wastewater as Pb,Zn,Mn and other heavy metals pollution sources.（3）Jianli and Shishou in order to improve the agricultural yield and total output of crop fertilizer quantity increase.Phosphate fertilizer use,especially the use of nitrogen fertilizer,agricultural technology improvement,greenhouses and plastic into agricultural production lead to heavy metals in sediments and Pb content increase.3.After 1949,with the economic development of Jingzhou City（with the example of Shishou and Jianli）,the industrial base was improved and the transportation network realized,leading to the increase of heavy metal elements Pb,Zn and Mn in sediments.Heavy metal pollution in the drilling of three oxbow lakes starts at about the same time and is divided into three stages:First,Pb pollution reached the first level in the 1950s-1980s,Zn and Mn did not reach the pollution level;Phase II Pb reached level II in 1982,Zn reached level I in 1994 and Mn did not reach level II in the 1980s and early 2000s;After phase III,Pb contamination was reduced to the first level of pollution and Zn was also reduced to the uncontaminated level after reaching the first level of pollution between 1990 and 2009,during which time Mn reached the first level of pollution.4.The change of heavy metal pollution level in three oxbow lake sediments bore is consistent with the economic development of Jingzhou and the development of three major industries.However,the level of pollution is low,which is mainly related to the food processing industry,textile industry,paper industry,plastics products and building materials metal industry in Jingzhou City,and less large heavy industrial enterprises.The trend of increasing pollution level after 1949 and falling back after the high pollution level in the 1980s is mainly due to the rapid development of secondary industry in the 1980s,which has increased heavy metal pollution.