The Ecological Risk Assessment Of Cd In The Culti-Vated Soils Around The Ni-Mo Polymetallic Mining Area,Songlin,Zunyi

With the development of industrial civilization,further exploitation and utilization of natural resources by human beings.In particular,the destruction of the ecological environment caused by the production activities of industry and mining industry.At present,the soil Cd pollution in our country has been paid much attention,deterioration of ecological environment,cultivated soil degeneration and a series of environment problems over all restrict development of agriculture in our country.The series of black rock contain chemical element,so it be named as “ Multi-element enrichment layer”and by divided into the“natural source”of heavy metal pollution in soil.Cd is the one of dispersive elements in natural,it have stong features in biological toxicity.In this paper were collected typical region in south China as research area of Xiaozhuliushui and houzhuang's Ni-Mo mine on black rock soil,in Zunyi.Collect the samples in dry land,paddy field and botany of study area use system method,analysis the average content of Cd and source in samples and spatial distribution characteristics.At the last use geo-accumulation index(Igeo)and potential ecological risk index(Eir)to valuate the dry land and paddy field pollution degree of study area,the result show that cultivated land in the study area was polluted by Cd universally,paddy soils have a high potential risk.The results of this paper provide a reliable scientific basis for the prevention and control of black rock's soil environmental pollution,environmental quality assessment and planning of agricultural producti-on.The main results obtained in this paper are as follows:1)The distinguish avarage content of Cd in dry land,paddy field and botany is1.60ug/g,2.21ug/g and 0.51ug/g,among rang is 1.01~3.13ug/g,0.97~5.13ug/g and0.02~2.28ug/g.The content of Cd in dry land,paddy field and botany have similarity of the terrain and position,on same type samples the position low soil layer thick and fertile.The position closer the deposit the more higher of Cd's content.The positions both sides of the road get into Xiaozhuliushui have high content,it may be have a same source of transport dust settlement.2)The distinguish avarage content in dry land,paddy field and botany in theNi-Mo mine of Xiaozhuliushui and houzhuang is 1.52ug/g,2.30ug/g,0.50ug/g,1.69ug/g,1.97ug/gand 0.58ug/g;The variation coefficient is 42.11%,57.83%,72.80%,49.70%,32.99%and 128.15%.The dry land of Xiaozhuliushui are light-medium and secondary grade pollution.The proportion of light-medium grade is 66.7 percentage.The aveluate of potential ecological risk index is secondary and high grade,among secondary grade is major.The proportion of light-medium,secondary and high grade in paddy field is37.5%,37.5% and 25%;The proportion sum of second high and high grade of Eir achieve 62.5%.The Igeo and Eir of paddy field is more higher than dry land in Xiaozhuliushui.3)The light-medium have 3 samples,secondary is 1 samples and medium-heavy pollution is 1 samples of dry land,among light-medium and secondary grad pollution proportion is 80%,the major Eir is secondary and second high grade;The contaminat grade of paddy field are light-medium and secondary grad pollution,the major Eir is cecond high and high grade,among high potential ecological risk index proportion is higher.4)The content of Cd in paddy field is highest in different species samples types.The Igeo of paddy field is more higher than dry land,because the low position,thick fertile and moist become the “gather”.But the dry land is thin and dry than paddy land that can't collect the heavy metal Cd element,the content of in dry land is lower than Paddy field universal,the potential ecological risk index of paddy land is higher than dry land and cover dry land samples.5)The soil on black rock Ni-Mo mine layer was polluted by Cd and the grade is more than light-medium in Songlin,some one achieve medium-heavy grade,the grade of all samples between the lowest and highest grade in geo-accumulation index.The major of potential ecological risk index is second high and high grade,the grade of all samples between the lowest and highest grade in potential ecological risk index.To compare two mine spots of Ni-Mo Polymetallic,the soil of Xiaozhuliushui black rock Ni-Mo mine area was polluted by Cd is higher than houzhuang's,and have higher potential ecological risk index.It maybe the Ni-Mo mine spots was developmented to the full in Xiaozhuliushui,but houzhuang was non't and be sealedby government ministry.The Stacking field of slag was expose be located above settlements cultivated land.6)The content of Cd in Ni-Mo mine area is higher than the stand of National standards for food safety and contaminants by limited in food than cereal crop by limited lower 0.1ug/g and vegetables by limited lower 0.05ug/g.