Inverstigation Of Heavy Metal Concentrtaion In Wheat Grain And Human Health Risk Assessment In Shaanxi Province

As one of the staple cereal crops for people worldwide,wheat ingestion and products are the major exposure pathways for heavy metals(HMs).Therefore,it is critical to investigate HMs level in wheat to understand its impact on human health.Shaanxi Province is one of the main cradle of agriculture in China,where the dietary habits of local residents were dominated by wheaten food.For this reason,the object of this study was wheat grain of wheat-cultivional area in Shaanxi Province.This research included 4 prefecture-level cities(Xi’an,Baoji.Xianyang and Weinan),31 counties,and 425 wheat grain samples.Totally six HMs including Cr,Ni,Cu,Cd and Zn were involved in this study.The statistical analysis,heavy metal pollution index(PI),health risk assessment,the principal component analysis(PCA)and correlation analysis were selected for assessing the impact of these metals on human health.The data gathered from Baoji city was taken as an example,these data were processed by Nemero index and geoaccumulation index and combined with the spatial distribution and bioconcentration factor(BCF)to explored absorptive characteristic and pollution sources of heavy metals in wheat grain.Those results would offer scientific references for agricultural soil pollution protection and management in typical agricultural district.The main results were:1.The mean grain concentration levels of HMs in wheat cultivation areas of Guanzhong Plain in Shaanxi Province were lower than the Chinese food hygiene standard(GB 2762-2017)and Limits of eight elemetns Pb,Cd,Cr,Hg,Se,As,Cu and Zn in cereals,legume,tubes and its products(NY 861-2004).There was no directly contamination of wheat grain in the study area.But some sampling points exceeded limits,including a total of 0.24% of Cu(1 point in Xianyang,Liquan),a total of 0.94% of Zn(5 points,3 in Baoji and 1 in Xianyang),and a total of 7.29% of Pb(31 points,23 in Xi’an and 8 in Xianyang).2.The distribution of heavy metals in wheat grain was different in the four cities.Cr and Pb were highest in Xi’an and lowest in Baoji,in order as: Xi’an>Xianyang>Weinan>Baoji.Ni and Cu were highest in Xianyang,in order as Xianyang > Xi’an n>Baoji >Weina.The difference of Cd and Zn was small in four cities,in order as: Weinan>Xianyagn>Xi’an>Baoji.Metal Pollution Index(MPI)of wheat grain samples were lower than 1 in study area,implied that the grain was not contaminated with heavy metals.The order of comprehensive situation of cities was Weinan< Baoji<Xianyang<Xi’an.3.The noncarcinogenic risk assessment indicated existing noncarcinogenic risk by eating wheat grain in study area.Since the hazard index(HI)was higher than 1 excpet Yangling in Xi’an,Fufeng in Baoji and Sanyuan in Xianyang..There were 83.76% points having noncarcinogenic risk.Sampling points focused on the range of Xianyang and Xi’an,where HI was higher than 1.5(27.59%).Those samples were concentrated in Xianyang(Wugong,Liquan,Yongshou and Bin)and Xi’an(Hu,Lantian and Zhouzhi).Sampling points of HI higher than 1.5 was 42.37% in Xianyang,35.49% in Xi’an,19.55% in Weinan,and 7.40% in Baoji.The noncarcinogenic index was as follow as: Xianyang(1.45)>Xi’an(1.34)> Weinan(1.33)>Baoji(1.13).Overall,the noncarcinogenic risk was that Xianyang and Xi’an were higher than Weinan,Baoji was the lowest.There was not carcinogenic risk of heavy metals for wheat grain in study area.4.Taken Baoji as an example to explore the transfer of heavy metals in wheat-soil systems,the order of the BCF was as follows: Zn > Cu > Cd > Ni > Cr >Pb.Zn,Cu and Cd easier transferred from the soil to the wheat grains.There was similarity of special distribution of Cd and Pb between concentration of wheat grain and soil,having medium correlation.So,Cd and Pb in wheat grain were influenced by concentration in soil.Heavy metals of wheat grain of Baoji can be divided into two categories on the basis of PCA.PC1 Cd,Ni,Cu,Zn and Pb were affected by PC1,such as fertilizer,irrigation water and pesticides.Ni was affected by PC2.According to the features of Baoji,there were two potential sources of pollution in wheat grain,source of agricultural activities in soil and source of industrial activities in atmosphere.In conclusion,heavy metals in wheat grain of research area were under the level of the Chinese food hygiene standard,without direct risk and potential carcinogenic risk,but with noncancinogenic risk.Therefore,soil management should focus on metal pollution reduction by various measures.