| Arsenic is one of the major environmental pollutants,it ranks in fifth place in soil pollution caused by heavy meatals in China.The content and situation of arsenic in soil affect the growth of plants and human health directly.Based on the determination of arsenic in soil and wheat in farmlands of Baiyin city,pollution degree,transfer characteristics and chemical behavior characteristics were studied.The main results of this paper were showed as follow.(1)The soil of studied area was polluted by arsenic to some extent.Seriously polluted areas are mainly located in Ya qu shui,Liang jia yao,Su jia dun,Minqin village and Yi du qiang,which are situated near the smelter outfall in the middle and upper reaches of Dongdagou ditch.Pollution of Hao jia chuan and fluoride salt factory were relatively mild,while Li jia ta zi,luo jia wan,Si long kou bei,Xin jian dui which downstream near the Yellow River estuary were in the clean level.The content of arsenic in the soil of Northwest copper processing plant and other there areas where were located in the upsteam of Xidagou ditch were less than the background value of Gansu Province,these areas were not polluted by arsenic.(2)The content characteristics of arsenic in soil profile showed surface gathering similar to other heavy metals.The content in surface higher than those in inner and gradually reduce with the depth increasing,it was close or below to the background value of Gansu Province in 80-100cm depth.Arsenic in soil showed weak migration with precipitation and other factors,the migration mainly concentrated in the 0-40cm depth and stabilized below 40cm.(3)The contents of five forms of arsenic in profile soil were obviously influenced by total arsenic and showed a decreasing trend from top to bottom with the decline of the total arsenic.Contents of loosely bound arsenic(L-As),aluminum arsenic(A1-As),Iron arsenic(Fe-As)were lower and decreased significantly with increasing depth.Below 40cm L-As basically could not be determined and Ca-As,O-As were main forms,and the percentage of Ca-As declining and O-As significantly increased to 50%or more.(4)Arsenic in reserched surface soil and pH,effective phosphorus had some negative correlation,and positively correlated with organic matter content though the correlation was not significant.The correlation between arsenic and carbonate content was not obvious..(5)The main form of arsenic in rhizospheric soil was Ca-As,the content and distribution coefficient of five forms appeared as:Ca-As>O-As>Al-As>Fe-As>L-As.Changes in the total arsenic could significantly affected various forms content.(6)The content distribution and accumulation ability of arsenic in wheat were in order of roots>leaves>husk>stalk>grains.Migration from roots to shoots was weak and the most of arsenic migrate to leaves.Arsenic pollution of soil affected the quality of wheat.The average content of arsenic in grains was 0.52mg/kg,the rate of exceeded rate was 19.23%.Ca-As,Fe-As and L-As had made the main contribution for arsenic absorption of wheat.There were highly significant positive correlation between arsenic in different parts of wheat and total content. |
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