| In this study,283 pairs of rice grain and corresponding surface soil(0-20cm)samples were collected from 8 districts of Fujian Province(i.e.,Fuzhou,Quanzhou,Putian,Zhangzhou,Sanming,Ningde,Nanping and Longyan cities)to identify the concentrations and spatial relationship of Mercury(Hg)and arsenic(As)in the soil-indica rice system..The correlations among soil concentrations of Hg,As and basic soil physical-chemical properties,Hg,As transfer characteristics in soil-rice grain system were also studied in this paper.The main results were as follows:1.The soil concentrations of total Hg varied from 0.017 to 1.827 mg·kg-1,which 37%samples exceeded the class ? standards of Chinese soil environmental quality standards.Soil available Hg concentrations ranged from 0.001 to 0.054 mg·kg-1.Total soil As concentrations still within the class ? limit of national soil environmental quality and ranged from 0.001 to 0.054 mg·kg-1.Soil available As concentrations ranged from 0030 to 3.835 mg·kg-1.The results based on correlation analyses demonstrated that positive significant correlations were observed between soil available Hg,CEC and clay content(<0.002 mm)with total soil Hg.Soil organic matter,CEC and clay content play important role on soil available Hg.In addition,soil pH,organic matter,free ion,CEC,clay content and available As both showed very positive significant correlations with total soil As.2.The Hg concentrations in the brown rice ranged from 0.131 to 41.78 ?g·kg-1,among which just 3.2%rice grain samples exceeded the national limit of pollutants in food(GB 2762-2012).The As concentrations in the brown rice varied from 0.015 to 0.944 mg·kg-1 and from 0.001 to 0.210 mg·kg-1 for inorganic As.Although the As concentrations of brown rice in hybrid indica rice were lower than that in conventional indica rice,statistical analyses showed that no significant differences of inorganic As and total Hg were found between them.Similarly,no significant differences of inorganic As and total Hg contents in brown rice were observed between two-line hybrid indica and three-line hybrid indica.Moreover,the results also showed that very significant positive correlation was showed between inorganic As and total As in brown rice.3.Accumulation factors of Hg in brown rice from soil were varied with indica rice(Oryza saliva L.)cultivates,which ranging from 0.001 to 0.557(total Hg)and from 0.010 to 8.438(available Hg).Accumulation factors of Hg in two-line hybrid indica were always lower than that of three-line hybrid indica,however,the accumulation factors in conventional indica were similar with that in hybrid indica.Accumulation factors of brown rice As ranged from 0.001 to 0.816 and 0.004 to 1.277,respectively for total As and available As.While,those for brown rice inorganic As,the accumulation factors varied from 0.001 to 0.812(total As)and from 0.004 to 1.277(available As).Comparing two-line hybrid indica with three-line hybrid indica,no significant differences of accumulation factors were existed,as well as between hybrid indica and conventional indica.4.The best regression equation based on brown rice Hg and inorganic As contents combining with the threshold values in the standard of food hygiene(brown rice Hg ?0.02mg·kg-1,brown rice inorganic As ? 0.2 mg·kg-1)were used to determine the Hg and As threshold values for soils of sampling areas cultivated with rice.The safety threshold values of soil total Hg and available Hg were 0.793 mg·kg-1 and 0.009 mg·kg-1,respectively,which were calculated with ?you673 and PeizaTaifeng.The safety threshold value for soil total As and available As were calculated with Teyou 627 and Quanzhen 10,respectively,which were 12.16 and 1.652 mg·kg-1.Therefore,this can make sure that brown rice Hg and inorganic As contents in the rest of most indica rice cultivars are within the pollutants limit values of food. |
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