Heavy Metal Pollution Characteristics And Risk Assessment Of Soil And Plant In A Mining Area Of Henan

In this paper,the soil,crops and dominant plants in a mining area in Henan are studied.By collecting the soil around the mining area,the total amount,morphological characteristics,pollution sources,spatial distribution and pollution evaluation of heavy metals are discussed,and the content and correlation of heavy metals in crops and rhizosphere soil are analyzed,and health risk models are used.To assess the human hazards caused by the intake of crops,investigate the species of the dominant plants in the mining area,analyze the heavy metal content and cumulative characteristics in the body,and select the high accumulative plants of heavy metals,and draw the following conclusions:(1)Among the heavy metals in the soil of the study area,only the content of Pb,Cd and Cr exceeded the two level standard of national soil environment,among which,Cd has the most serious pollution to the soil.Most of the heavy metals are of high variability,it indicates that the distribution of heavy metals in the mining area is relatively uneven and the difference is relatively large,which is greatly influenced by mining activities.(2)The morphological characteristics of heavy metals show that Cd mainly exists as acid extractable state,Pb mainly exists in reducible state,Cu mainly exists in oxidizable state,Zn and Cr mainly exist in residue state.Multivariate statistical analysis showed that Pb、Zn、Cu and Cr may have the same pollution sources,Cd and Zn may also belong to the same pollution source.The spatial distribution characteristics show that the distribution of heavy metals in the mining area is higher than that in the west,the main pollution area is located in the southeast part of the mining area.(3)Pollution assessment showed that Cd has the largest pollution index in single factor pollution index and the ratio of serious pollution grade is the highest.The evaluation of comprehensive pollution index showed that the ratio of heavy pollution in the sample reached 69.69%,and the mean value of the comprehensive pollution index of mild,moderate and severe pollution were 1.49,2.47 and 7.86 respectively.The level of soil pollution is in the degree of severe pollution totally.The potential ecological risk index is 187.61-3256.06 and the risk level is extremely strong。(4)The contents of heavy metals Pb,Cd and Cr of crops in the study area were higher than the limit of food contamination limits and food hygiene standards,and Cd was more serious for crop pollution.The trend of heavy metal concentration in different crops is shown as follows: Leaf vegetables> Root vegetables> Cereal corn.The most serious pollution of Cd in the rhizosphere soil of crops.Correlation analysis showed that only Pb and Cd in root vegetables were significantly correlated with heavy metals Pb and Cd in rhizosphere soil。(5)The total risk of non-carcinogenesis caused by the way of crop intake to adults and children is 4.52 and 8.99 respectively,which is far greater than the safety limit1.The total risk of carcinogenesis is 6.16x10-3 and 4.02x10-3,which is far beyond the limit of USEPA and it causes significant harm to the human body.(6)The dominant plants in this survey were mainly herbaceous plants,Gramineae and Compositae are the majority,most of them were local native plant.The content of heavy metals in the dominant plants is higher than that in the underground part.The contents of Cd and Cr in plants exceed the normal range of contents in plants,All plants did not reach the critical value of the hyperaccumulator.(7)A comprehensive view of the characteristics of plant enrichment and the characteristics of transportation,the green bristlegrass and fleabane have tolerance to heavy metal Pb,Wormwood and vitex are resistant to heavy metals Zn,Wormwood and miscanthus floridulus are resistant to heavy metal Cd,reed is tolerable to heavy metal Cr and honeysuckle is tolerable to heavy metal Cu.It can be seen that the remediation plant of contaminated soil in the mining area can be selected from the group consisting of green bristlegrass,fleabane,asiatic wormwood,vitex,miscanthus floridulus,reed and honeysuckle.