Pollution Of Heavymetalsin Thesediments From Rivers In Chongqing Main City Zone

Sediment is accumulation of pollutants in water environment,and can provide thehistorical polution information.Pollutants which deposit in sediment can be eleased andreturned to overlying water,and cause secondary pollution when vironmental conditionschanged.It is significance to study the sediment condition of a water environment for waterpolution.Heavy metals is a most important index in water pollution indexes,and can cause toxiceffect to ecological environment.Because heavy metals can be adsorbed to surface ofsuspended particle,and migrate and precipitate together,study ofheavy metal pollution insediments have usefully environmental representative of heavy metal pollution of water.Surfacesediment and water samplesoftributary in main urban area of Chongqing are collected. Heavymetal element include Cd, Ni, Cu, Fe, Cd, Zn and V content are determined and used indistribution characteristics analysis.Methods of geoaccumulation index, enrichment factor,potential ecological risk index and comprehensive contamination index are used toassesseheavy metal pollution in the sediment oftributary of Yangtze River and Jialing River inmain urban area of Chongqing.The highest concentration of Zn in surface sediment of secondary river appeared in Funiuriver, hou river and huaxi river account for the second, the average value was3.9,2.9and2.9times higher than the background value respectively;44.6%of the V value in sampling siteswas higher than background value of soil and the highest was2.4times higher than backgroundvalue; The concentration of Cr in sediment of Nanxikou river, Tiaodeng river, Qingshui river,Funiu river and Huaxi river was relatively high, which account for21.8%of the rivers with theconcentration of Cr2times higher than background value; Cu and Ni were almost close withthe background value;The heavy metal pollution of Cr,Ni,Cu,and Zn in Nanxikou river ofsecondary river was serious. Part of the area of Tiaodeng river were seriously polluted by Crand Zn. The concentration of Cr,Ni,Cu and Zn which was2times higher than the backgroundvalue account for21.8%,5.5%,10.9%and43.6%respectively.The risk assessment of secondaryriver in downtown area indicated that the pollution level by V and Cr in secondary river wasmoderate,by Zn and Cr was relatively low,by Zn and Cr in Tiaodeng river was above themoderate, by Cr, Cu and Zn in Nanxikou river was moderate-strong and strong. The sequenceof the heavy metal pollution caused by human activity is Zn＞Cu＞Cr＞Ni＞V, the source ofheavy metal in Tiaodeng river,Nanxikou river was mainly caused by human activity,the heavymetal pollution by Zn in Funiu river, Hou river, Huaxi river,Nanxikou river and Kuxi river wascaused by human activity.The potential ecological risk by heavy metal (Zn,Cu,Cr,Ni and V)was relatively low,Cu in Nanxikou river was strong-extremely strong,Zn in some part ofTiaodeng river was moderate,V,Cr,Ni,Cu and Zn were slight;The comprehensive pollution level of heavy metal (V,Cr,Ni,Cu and Zn) appeared the highest in Nanxikou river. Funiuriver,qingshui river,shuangxi river and Tiaodeng river were strongly polluted,Jilan river,Heishuitan river, Kuxi river and Lancao river were at the level of polluted, Chaoyangriver,Wubu river,Changtang river,Huaxi river were at the level of slightly polluted,Houriver,Liangtan river and Yulin river were at the level of influence，Daxi river,Jiantan river andChaoyang river were slightly polluted and were within the range of standard, the comprehensivepollution index was gradually increasing from upper stream to downstream in most of the rivers.the regional spatial distribution of heavy metal elements in Longjinghu lake, Chongqingcity. on the whole, with new and old sediment area of the mixing heavy metals overall relativelynew submerged area is high, some elements such as Cr, V, etc in the lake area content isrelatively high;The sediment vertical distribution shows that heavy metals V, Mn, Ni and Crhave content gradually increased in recent years, and the enrichment of intensity graduallyincreased.Land use type of Longjinghu lake upstream area is given priority to with agriculture,heavy metals in sediment content is less affected by the industry, and is mainly derived fromsoil and rock weathering erosion.Human activities affect cadmium (Cd) content in Longjinghulake, vanadium (V) content for main area of Longjinghu, Longjinggou and Zhaojiaxi have signsof exogenous input, the regional Cu, Ni, Zn, Fe and Mn mainly from natural weathering rocksoil;Potential ecological risk index of V, Cr, Ni, Cu, Zn and Mn in sediment of Longjinghu lakeis slight level, the regional Cd as strong or very strong,and the potential ecological risk ishigher.Pollution of Heavy metals (V, Cr, Ni, Cu and Zn) in main area of Longjinghu lake, LongJing gou area and Zhaojiaxi is relatively heavy, for the pollution level of influence lever.