| Soil pollution aroused people’s concern increasingly,as the rapid development of industry and agriculture.Pollutants are into the soil,resulting in progressive deterioration of soil ecological environment.Once the content is over soil self-purification capacity,the pollutants will be into the plant through the roots.It can not only affect its own growth and development,leading to the production and quality of agricultural products reduced,but also accumulate in the crops,further endanger human health through food chain.Therefore,research on the soil pollutants status and distribution is of great significance to understand the pollutants potential risk to ecological environment and human health.Polycyclic aromatic hydrocarbons(PAHs)and heavy metals like cadmium(Cd),chromium(Cr),plumbum(Pb),mercury(Hg)and arsenic(As)are common contaminants in soil.Thus,this study mainly focused on the PAHs in paddy soils in Nansi lake area and five heavy metals in farmland soils around mining areas.The distribution characteristics of these pollutants were analyzed,and further conducted the source analysis and ecological and human health risk assessment.In addition,four fractions(acid-soluble,reducible,oxidizable and residual fractions)of five heavy metals in farmland soil around mining areas were determined.The results showed:1 Source analysis and risk assessment of PAHs in paddy soil in Nansi lake areaBased on the pollution levels of Western Europe and on the nemerow composite index,only the WS region was highly contaminated.Using principal component analysis and Pearson correlation analysis,this study revealed that soil PAHs in this area was mainly affected by soil particle size distribution,of which sand particles had strong adsorption on the high-rings PAHs and clay has significantly negative correlations with PAHs.The dominant source was the coal combustion of coal mining and power plants.Irrigation with petroleum-polluted water was also one of source.Contaminated land exposure assessment(CLEA)model showed PAHs in soil in Nansi lake area cannot threat the health to children and adults,but the risk for children was higher than that for adults.The distribution of exposure ways decreased in the order of oral intake>skin contact>inhalation,and the distribution of sampling sites decreased in the order of:WS>TF>JX>XZ>QH>SZ.2 Source analysis and risk assessment of heavy metals in farmland soil around mining areasFive heavy metals(Cd,Cr,Pb,As,Hg)contents in farmland soil around mining areas were 5.6,1.05,2.03,1.42 and 7.86 times higher than background value of Shandong province respectively.And Cd cotent was over the limited value of national secondary standard.Based on principal component analysis and Pearson correlation analysis,heavy metals were slight influenced by pH and soil cation exchange capacity(CEC).In addition,soil environment affected Cd,As and Hg contents slightly.Correlation between Cr content and free Al and Fe oxide,sand,clay was positive significantly,while correlation between Cr content and silt was negative significantly.Correlation between Pb content and soil organic matter,sand was positive significantly.The result of ecological risk assessment showed that Cr pollution was light,As and Pb were slightly polluted,and Cd and Hg pollution was high.The comprehensive pollution of heavy metals was serious.The dominant source was three industrial wastes emissions and mining activities.Phosphorus fertilizer and pesticides containing heavy metals application was also one of the source.Five heavy metals did not produce cancer and non-cancer risk for human health.3 Chemical Speciation of heavy metals around mining areasThe reducible fraction was the main proportion of Cr,As and Hg in soils,accounted for 62.39%,72.26%and 89.84%respectively.Hard used fraction(K3)was dominated,followed by moderate used fraction(K2)and available fraction(Ki).The content of available fraction was least,accounted for 5.6%,13.41%and 2.22%respectively,so that they can hard to be used by outsiders.Cd and Pb were dominated in K1,accounted for 47.76%and 48.84%respectively,followed by K3 and K2,which indicated they can be easily into the environment and affect creatures.Correlation analysis declared that Cd,Pb and As fractions content had significant correlation with their total content.The influence of soil basic properties to different heavy metal fractions content was same as that to total heavy metals content.The effect of soil environment to Cd fractions content was small.Reducible fraction of Cr was significantly influenced by soil organic matter.Oxidizable fraction of Hg was influenced by cation exchange capacity significantly.Correlation between soil properties and Pb and As fractions was significant.The results of the RAC and RSP risk assessment found that the risk caused by five heavy metal was decreased in the order of Cd>As>Cr>Hg>Pb,and pollution level was decreased in the order of Pb>Cd>Cr>As>Hg.This study established a foundation for the control of pollutants in farmland soil and environmental management.It also provides a scientific basis for the health assessment in this region.So it has double significance of environment and health. |
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