| Coal and surrounding rock minerals were rich in a variety of toxic and harmful trace elements,which were easier to be released into the surrounding environment during the processes of coal resources exploitation.It will inevitably lead to the heavy metals(HMs)contamination of atmosphere,water body and soil of natural environment,even posed a threat to human health through the food chain enrichment.This paper selected the Sunan mining area of Huaibei coalfield as the research object,and 59 topsoil samples,8 gangue samples,24 soil profiles and 67 maize plants were collected.The distribution characteristics of HMs pollution in the soil-maize system(S-Ps),the occurrence speciations and vertical migration of HMs,and the accumulation characteristics of maize plants near the coal gangue mountain in this study area were investigated.Meanwhile,the health risk of HMs via intaking maize grain were also evaluated.The main research findings were as follows:(1)Except for Mn without the standard limits,other six elements did not exceed the grade II standard for national soil environmental quality.The mean concentrations of Cu,Ni and Cd exceeded the corresponding limits of soil background values in Anhui Province by 1.25-,1.63-,and 2.58-fold,respectively,and the average contents of Mn and Zn was higher than that of coal gangue samples.The integrated evaluation results suggested Cd was the most significant ecological risk factor in this mining area,while other HMs were all at the slight risk level.Moreover,multivariate statistical results indicated that Pb,Cu and Zn were mainly affected by the transportation of coal mining areas,Mn and Cd were mainly originated from the combined pollution of coal dust and agricultural production activities,whereas Ni and Cr could be interpreted as the combined effect of parent material and coal mining.Kriging spatial interpolation results showed that except for local areas in the southeastern part of Sunan mining area,Mn and Cu had similar spatial distribution characteristics,whereas other HMs possessed their own regional differences.(2)In the maize plant(immature period),Mn,Cu,and Zn mainly absorbed and accumulated in leaf parts,and Pb,Cd,Ni accumulated mostly in stem parts,whereas Cr principally accumulated in root parts.In mature stage,Pb was transformed from the stem parts to root parts,while Cd and Ni was transformed from the stem parts to leafparts.The forms of topsoil were dominated by the percentage of residual form,and available form Cd was the highest,whereas Cr was the most stable in the environmental.Except for Luling(LL)profile samples,Mn,Cu,Ni and Zn in other samples gradually decreased with deep increasing,and showing obvious vertical migration characteristics.(3)The accumulation and transport of Cd was the most significant by maize parts,and the potential migration of HMs from the root parts of maize to the edible organs was stronger.Various speciations in soil could promote or inhibit the absorption processes of HMs in maize root.Under the exposure path of food intake,the health risk of HMs to children was much higher than that of adults,and the size of health risk index was in the sequence of Cr > Cd > Zn > Pb > Ni > Cu. |
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