| Owing to rice has strong bioaccumulation ability for methylmercury,consumption of rice is the main way of exposure to methylmercury in China's inland residents.However,mercury pollution is unclear in major rice-growing areas of China.Based on the distribution area of rice in China,At the rice harvest season(September and October in 2014,September and October in 2015),we collected the samples of rice plants(including roots,stems,leaves and grain)and its paddy soils.According to different natural environment,five different rice growing areas(northeast rice area,northwest rice area,southern China area,central China area and southwest rice area)were selected from the geographical area,including Heilongjiang Province,Jilin Province,Fujian Province,Guangdong Province,Guizhou Province,Sichuan Province,Zhejiang Province,Jiangsu Province,Jiangxi Province,Anhui Province,Hunan Province,Hubei Province,Xinjiang Uygur Autonomous Region,Guangxi Zhuang Autonomous Region and Chongqing City.The total mercury concentration,soil pH and organic matter were measured,In order to figure out the spatial distribution characteristics of total mercury in the paddy field and its influence factors in the main rice producing areas of China.The results are as follows:1.The distribution of total mercury in paddy soils:1)The soil mercury concentration in paddy field ranged from 4.6 ?g·kg-1 to 535.2 ?g·kg-1 with an average of 54.5 ?g·kg-1,of which 0.88 percent of the samples polluted when compared with 300 ?g·kg-1 of soil environmental quality standard for agricultural land in China(GB15618-1995).2)The SPSS ANOVA test showed that the concentrations of mercury in paddy soil were significantly different(p<0.01,n=684).The soil mercury concentration was the highest in the southwest rice area(79.9 ?g·kg-1)and the maximum value is 535.2 ?g·kg-1.The lowest mercury concentration in paddy soil is northeast(26.8±7.0 ?g·kg-1)and northwest rice area(25.8±19.8 ?g·kg-1).The concentration of mercury in paddy soil increased from north to south.3)There was a significant positive correlation between paddy soils mercury concentration and rainfall(R2=0.2566,p<0.01).Indicating that atmospheric mercury deposition may be one of the major sources of soil mercury in paddy soils.2.The distribution of mercury in paddy soil and rice plants:1)The distribution of the total mercury concentration in the southwest rice area was root>leaf>stem>rice,differ from the distribution of mercury in the other four rice areas,which was leaf>root>stem>rice.This is because the background value of high mercury in the southwest region makes the soil mercury content higher than other rice areas,and the root mercury is mainly from the soil,so the total mercury concentration of the root is higher than the total mercury concentration of the leaves.2)There was a significant positive correlation between total mercury concentration in paddy soil and total mercury concentration in roots(R=0.680,p<0.01),stems(R=0.568,p<0.0)and leaves(R=0.539,p<0.01)of rice,and there was a significant positive correlation between root,stem and leaf(root&stem R=0.670,p<0.01?stem&leaf R=0.630,p<0.01?root&leave R=0.482,p<0.01),indicating that the soil was in the same nutrients are transported up to other parts of the rice plant,which can cause the mercury to migrate more smoothly to the above-ground plants.There is a significant positive correlation between the total mercury content and the organic matter content in the soil(R=0.417,p<0.01).The reason is that the soil organic matter is very strong ability to complex and fix mercury.3.The distribution of total mercury in rice(white rice)and its health risk assessment:1)The total mercury concentration of rice was ranged from 1.06 ?g·kg-1 to 45.13 ?g·kg-1 with an average of 5.46 ?g·kg-1,of which 8.8% of the samples exceed the nationally permitted level of total mercury(20 ?g·kg-1)in food.2)There was a difference in the concentration of mercury between rice producing areas.The highest concentration of mercury is located in Central China,with an average value of 8.31 ?g·kg-1,ranging from 1.06 to 45.13 ?g·kg-1,the lowest rice area is 3.75 ?g·kg-1 and the range is from 1.49 to 22.52 ?g·kg-1 in the northwest.3)China's population of mercury intake of rice per capita in the range of 0.004-0.177 ?g·(kg·d)-1 through the consumption of rice,and China's rice population HRI range from 0.007 to 0.310.Therefore,there is safety in rice consumption in non-point source polluted rice ecosystems in China. |
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