Analysis Of Heavy Metal Pollution Characteristics And Risk Assessment Of Coking By-products And Plant Soils And Spatial Variability In Soil

China is a big coal country,and the coal chemical industry has created a heavy burden on the environment while developing its national economy.The coking plant belongs to the coal coke processing industry.The main wastes of the coking plant include coking sludge,tar residue,coke powder,sulfur paste and coking wastewater.The coking waste will cause serious pollution in the area of the coking plant and the surrounding environment.Industrial production will change the soil ecological environment in the plant area,and have a serious adverse effect on the plant area and the surrounding ecological environment.Heavy metals are an important pollution evaluation indicator.The analysis of the content and occurrence of heavy metals in the wastes of coking plants,and the research on the content of heavy metals,spatial variability and risk assessment of the soil of the plant are conducive to further strengthening the utilization of waste resources.And integrated management.This study selects the coking sludge,tar residue,coke powder,sulfur paste,coking wastewater and the surface soil around the solid waste storage area in three typical coking plants in central,western and southern Shanxi Province as the research objects.Absorption spectroscopy was used to determine the contents of 7 heavy metals including Cu,Ni,Pb,Zn,Mn,Cd,and Cr in solid waste,wastewater and surrounding surface soil.The results showed that the contents of heavy metals in different wastes are different.The contents of Zn,Pb and Mn in the heavy metals in coking sludge and tar residue are relatively high.Among them,the three heavy metals are located in the B plant in the west of Shanxi and the C plant in the south.The content of the three elements in the B plant even exceeds 200 mg/kg;the highest content of Zn in the coke powder is more than 50 mg/kg,and the content of Pb and Mn in the coke powder of the B plant is relatively high.The content of Zn and Cr in the sulfur paste is higher,and the content of Zn and Cr in the A plant in central Shanxi are both in the range of 50-160mg/kg;the content of the influent and effluent of coking wastewater is the highest.The heavy metals are all Zn,the Zn content in the influent water is between 0.40-0.65 mg/L,and the Zn content in the effluent water is between 0.35-0.45 mg/L.Through analysis and risk assessment of the occurrence of heavy metals in solid waste,the results show that the proportion of extractable heavy metals in coking sludge,tar residue,and sulfur paste is relatively high in oxidizable state and residue state,indicating that when the p H changes Heavy metals are more effective to plants;the extractable state of Zn in the coking sludge accounts for about 50%,and the mobility is relatively strong.The extractable state of Pb and Mn accounts for about 20%-60%;B.The oxidizable state of heavy metals that can be extracted from plant C tar residue is relatively high,and the oxidizable state Zn accounts for about 40% of the total Zn;the pollution of Pb and Zn in the tar residue is serious;the components of coke powder and tar residue are similar,mainly including Quartz,iron ore and other substances,due to the high content of fixed carbon,so Zn and Mn mainly exist in the form of acid exchangeable,carbonate combined state and residue state.Acid extractable Zn and Mn in coke powder of B and C plants The proportions of elements are in the range of20%-40%;sulfur paste contains a large number of S and SO bonds,which are easy to combine with heavy metals and increase the proportion of extractable heavy metals.The proportion of extractable Zn and Cr in Plant A is about 70%-90%;For coking sludge,Cd,Cu,Ni,Pb,Zn,Mn are polluted to different degrees,which cause heavy pollution of tar residue and extremely high ecological risk.In addition to Cd,there are heavy metals with high content.Influence of Pb,Pb and Zn in sulfur paste have low to moderate pollution;although the content of Cd in each solid waste is low,its high toxicity response coefficient is the main reason for the high to extremely high ecological risk of solid waste;human health The risk assessment results show that the Cr element in the coking sludge,the coking solid wastes are likely to cause a certain health risk to the staff of the coking plant,and the main exposure route is ingestion and skin contact.Further research on the distribution of heavy metals in the surface soil of the coking plant found that the levels of Mn,Zn,Pb,and Cu in the horizontal surface soil surrounding the solid waste storage area in the coking plant are relatively high,and the content of Mn is between300-800 mg/kg,and Zn And Cu are more than 50 mg/kg,and Pb is in the range of 20 – 150mg/kg;principal component analysis shows that Ni,Cd,and Mn in the soil of Plant A are greatly affected by the coking plant,and the elements of Ni,Pb in the soil of Plant B are greatly affected by the coking plant.Related to the coking plant,the Mn,Cd,and Cr in the soil of the C plant are relatively affected by the coking plant;the heavy metal residue in the soil accounts for a relatively high proportion,and the extractable Mn is mainly in the acid extractable state and easily reducible state.Both are between 10% and 50%.Zn and Pb are mainly in acid extractable state.The residual state of Zn accounts for a relatively large proportion,the proportion of acid extractable state is less than 20%,and the proportion of acid extractable state of Pb is basically greater than 20%;Mn,Cu,and Zn all have bright spatial variability in the vertical direction: as the vertical depth increases,the total amount of Mn increases,and the total amount of Cu and Zn decreases,and acid extractable Mn gradually accounts for the proportion Decrease,the proportion of easily reducible Mn increases,and Cu gradually transforms into non-extractable form;combined with the principal component analysis,it is found that the spatial variability of Cu and Mn in the soil of Plant B and Plant C is relatively large due to natural factors.The ecological risk assessment of soil heavy metal pollution shows that the pollution degree of Cu,Pb and Cd is relatively serious,and the higher ecological risk of soil heavy metals is caused by Cd.The human health risk assessment shows that both adults and children in the coking plant may face certain Cr exposures.Carcinogenic risk.