Spatial distribution characteristics of heavy metal content in soil, rice leaf and brown rice in farmland on both sides of No. 205 national road.

Contents of Al,Cd,Cr,Cu,Fe,Ni,Pb,Zn and As in surface soil,rice leaf and brown rice(Oryza sativa L.) in farmland of 200 m range away from No.205 national road without forest belt and their spatial distribution rules were investigated.The results show that the contents of Cd,Cr,Cu,Ni,Pb and Zn in surface soil reach the first grade of Environmental Quality Standard for Soils(GB15618-1995),and the As content exceeds the limit of the third grade.The contents of Al,Cr,Fe,Ni,Zn and As in surface soil,Al,Cd,Cr,Fe and Ni in rice leaf,and Al,Cd,Cr,Cu,Fe and Ni in brown rice on the western side are higher than those on the eastern side,indicating a greater influence of dispersion and deposition of vehicle emissions on the western side,and this phenomenon relates to the easterly prevailing wind.The contents of Ni and Zn in surface soil on the western side,Cd in surface soil on the eastern side,Al and Zn in rice leaf on the western side,Fe in brown rice on the western side and Al in brown rice on the eastern side have a rule of obviously decreasing with the distance away from road edge increasing,and have significant or extremely significant negative correlation with distance away from road edge.Content distributions of some heavy metals in rice leaf and brown rice have an obvious peak value range,reach their peaks inrange of10-20 mawayfrom theroadedge,andhavesignificant or extremely significant positive correlation with contents in surface soil.In brown rice,element As is not detected and the contents of Al,Cd,Cr,Cu and Zn don't exceed the limits of the national food sanitary standards,but the contents of Ni and Pb in some samples are slightly higher.According to principal component analysis,Pb in rice leaf mainly comes from the surface soil and the contents of the other heavy metals in rice leaf are obviously influenced by dispersion and deposition of contaminants from the road.It is suggested that heavy metals accumulate obviously in farmland on both sides of No.205 national road,in which the accumulation of As is the most serious.Contents of heavy metals in rice leaf and brown rice are obviously influenced by dispersion and deposition of vehicle emissions which are concentrated in range of 10-20 m away from the road edge.