The Spatial Distribution Of Heavy Metals Of The Typical Tanning Industry

Leather industry provides leather products for people and satisfies people’s life needs.However,leather manufacturing process will produce a large number of toxic and polluting substances,which,if not controlled,will have serious consequences on the ecological environment and human health.The pollution of wastewater and solid waste from leather industry is often paid attention to by people.As for soil pollution,it is the result of slow action of various activities,which is often ignored by people.Especially in some developing countries,there are a large number of tanneries.Due to the backward technical level and people’s neglect in the past,industrial polluted sites gradually appear.Meanwhile,with the expansion and development of cities,the land is re-planned and utilized,and the pollution problem of industrial sites urgently needs to be solved.This paper studies the distribution rule of heavy metals in tanning site,evaluates the pollution status of heavy metals in the site,and provides a scientific theoretical basis for land risk management.This study selected a typical historical leather industry zone in Zhejiang province and divided the site into industrial zone,residential area,farmland and road according to the actual historical land use.Cr in the surface sediments(Ⅵ),zinc(total),Pb,Cu,Cr,Ni,Hg and As 8 classes in spatial distribution characteristic of heavy metal element and its influencing factors were studied.The risk assessment of heavy metals in the site was made by using single index method,Nemero comprehensive index method,land accumulation index method and potential ecological risk index method respectively.The health risk assessment of heavy metals in leather tanning sites was carried out by using the human health risk assessment model of the us environmental protection agency(USEPA).The main conclusions are as follows:(1)The research field of 8 kinds of heavy metal element Cr(Ⅵ),Zn,Cu,Cr(total),Pb,Ni,Hg and As monitoring average soil background values are 3.5,1.8,1.3,2.0,1.7,0.7,2.3,and 0.4 times.Cr(Ⅵ),Hg,Cr(total),Zn,Pb are high pollution concentration.(2)The level of heavy metals,according to the spatial distribution of 8 kinds of heavy metal element Cr(Ⅵ),Zn,Cu,Cr(total),Pb,Ni,Hg and As the overall spatial distribution exists consistency,highest in industrial area,followed by residential areas,and at last the farmland.Cr(total)is highly correlated with Zn,Pb and Cu,and heavy metals Cr(total)and Zn are mainly derived from leather industry activities.Cu and Pb may come from vehicle exhaust deposition.Hg may have originated from coal burning activities in the early leather industry.Ni and As represent the release of soil parent material.(3)The spatial distribution of Cr(Ⅵ)and Cr(total)is different,and Cr(Ⅵ)is restored to Cr(Ⅲ)to a certain extent.PH size has the same distribution rule as Cr(Ⅵ),high pH is related to Cr(Ⅵ)stability,that is,the point Cr(Ⅵ)with high pH is also relatively high.The distribution of Cr is almost in line with the distribution of tanning factories,and the northeast direction is the location of the industrial zone.The concentration was high in the northeast direction,and Cr(Ⅵ)was reduced in this direction.So Cr(Ⅵ)is relatively high at a high pH.(4)Single pollution index evaluation results showed that Cr(Ⅵ)reached the level of moderate pollution,and the other 7 heavy metals were all within the safety line.The result of Nemero comprehensive pollution index is moderate pollution.The cumulative pollution index evaluation shows that Cu,Cr(total),Pb,Ni,Hg and As heavy metal elements in the monitoring points are at the pollution-free level,while Cr(Ⅵ)is at the moderate pollution level.Zn is pollution-free to moderate pollution level.According to the evaluation results of potential ecological risk index,Eri,Cr(Ⅵ)and Hg have medium potential risks.The potential risks of Zn,Cu,Pb,Ni,Cr and As are slight.The comprehensive potential risk index RI shows that the potential risk is medium.(5)The non-carcinogenic risk assessment results of the tanning site show that both adults and children’s non-carcinogenic risks are within the acceptable range.(6)The carcinogenic risk assessment result of the leather processing site shows that there are carcinogenic risks for children and adults.The adult cancer risk related to Cr(Ⅵ)of heavy metals and the As,children’s risk of cancer related to heavy metal for Cr,Pb and As(Ⅵ).Therefore,planning of child-related land-use types is not recommended.