Pollution Characteristics And Risk Assessment Of Mercury And Arsenic In The Farmland Soil And Crop From Baiyin

Farmland soil is a place that directly supplies production and food for all humans.Its quality and status relate to the health of human beings and ecosystems.Sewage irrigation has solved the shortage of agricultural water as well as incre ased the content of heavy metals in farmland soil and crops,and then via food chain harms human health.Therefore,it is necessary to investigate the pollution status of heavy metals(especially Hg and As)and evaluate their risks in the farmland soil and crop,which is of great importance to the treatment of heavy metal pollution in soil,the improvement of soil environmental quality,and the protection of human health.Baiyin is a typical industrial and mining city,located in northwest China.The paper chooses the farmland soil and crop from Baiyin as research object.By methods of field investigation and lab analysis,this paper focuses on the pollution state of Hg and As in farmland soil,the pollution characteristics of Hg and As in wheat and corn,and the effects of Hg and As on human health and ecosystem.The main results are showed as follows:(1)Compared with the soil background values of Gansu and level?of environmental quality standard for soils in China,the farmland soil of wheat and corn from Dongdagou stream is polluted by Hg and As in different degrees while Xidagou stream is of no pollution.(2)Most Hg and As are easy to accumulate in leaves for wheat while they are easy to accumulate in roots for corn.(3)Residual fractions for Hg(RES-Hg)and As(RES-As)occupy the highest percentage in farmland soil of wheat and corn,indicating a weak mobility of Hg and As in farmland soil.(4)The crop oral intake hazard quotients(HQ)of both Hg and As in wheat and corn for children are approximately 2 times higher than that for adults,indicating that children are much easier to be exposed to the risk of wheat and corn contaminated by Hg and As.The crop oral intake is the main exposure route to cause non-carcinogenic and carcinogenic risk for local residents.(5)Mercury in farmland soil of wheat and corn belongs to extremely strong ecological pollution and As belongs to mild ecological pollution.The comprehensive potential ecological hazard index(RI)of soils are higher than 1200,which indicate the heavy metals pollution are very strong level.All in all,this paper make clear the pollution status of Hg and As in the farmland soil crop-system from Baiyin district,and also shed lights on their spatial distribution patterns and potential poulltion sources,which provides reliable foundation for the comprehensive prevention and control of Hg and As pollution for local government.The contaminated crops have a negative impact on the health of residents through the crop oral intake.It is suggested that local government should strengthen the management and detection of industrial sewage,and carry out the remediation of contaminated farmland soil.Besides,the residents should adjust the distribution of agriculture cropping pattern and food crops which should not be planted in the farmland soil of Dongdagou stream.All of these measures should be effectively implemented to protect the health of local residents.