| The research area is located in the downstream of Wanshan mercury mining area,and the mercury pollution in farmland was more serious.In this study,the spatial distribution characteristics of total mercury and methylmercury in soil and rice were studied through investigation and analysis of paddy soil and rice in the region;The effects of these measures on the absorption of accumulated mercury in rice were studied through the screening of rice varieties with low mercury accumulation and field experiments on the application of soil conditioner and water regulation on the basis of planting rice varieties with low mercury accumulation.The main findings are as follows:The variation range of total mercury(THg)content in paddy soil was 1.09?56.60mg/kg,methylmercury(MeHg)was 0.218 ? 14.56 ?g/kg.The distribution of THg and MeHg in rice fields is different.The different spatial distribution of soil THg and MeHg is caused by mercury-containing Wawu River water and its sediment carrying water,as well as the water flow in rice field canals.In addition,the spatial distribution of soil sulfur is also an important factor affecting the spatial distribution of methyl mercury in rice fields.The content of available mercury and MeHg in soil was negatively correlated with organic matter and positively correlated with available zinc.Secondly,the effective mercury was negatively correlated with available potassium and alkali-hydrolyzed nitrogen,and positively correlated with available manganese.The THg content range of rice is 10.70 ?g/kg ? 160.29 ?g/kg,the range of MeHg content is 0.746 ?g/kg ? 40.32 ?g/kg.There is a significant positive correlation between total mercury and MeHg in rice and THg in soil,MeHg and available mercury,especially MeHg.Besides soil mercury,there was a significant negative correlation between THg and MeHg content in rice and soil p H,OM,and a significant positive correlation with available phosphorus in soil.In addition,there was a significant negative correlation between available potassium and available iron and available manganese in rice.Of the 11 rice varieties planted in mercury-contaminated soil,two rice varieties,Quanyou 822 and Yixiangyou 800,had the highest THg and MeHg levels.T16 rice varieties had the strongest cumulative ability to accumulate total mercury and MeHg in rice,and the content of THg and MeHg in rice was lower,and the bioconcentration coefficient and the transport coefficient between organizations were relatively small.Therefore,Jingliangyou Huazhan is a rice variety with low mercury accumulation ability.On the basis of planting rice variety Jingliangyou Huazhan,organic fertilizer and biochar were applied to mercury contaminated soil.The results showed that soil conditioning agents had an effect on rice uptake of cumulative THg and MeHg,especially MeHg.The decrease rate of MeHg content in rice was 7.44% ? 39.93%after the application of 150?300 kg/mu of biochar.The increase rate of MeHg content in rice was 44.83% ? 149.00% after applying soil organic fertilizer at 700 ? 2000kg/mu dose.As can be seen,biochar(150 kg/mu)applied to inhibit the accumulation of mercury in rice is better than organic fertilizer,and low amount of biochar can effectively reduce the accumulation of THg and MeHg in rice.Therefore,the combination of rice variety Jingliangyou Huazhan and low amount of biochar is an effective measure to reduce the mercury content of rice.Compared with the normal management mode,the total mercury content of rice decreased by 38.05% and the MeHg content increased by 26.07% under the condition of long-term flooding.The intermittent irrigation method can reduce the accumulation of THg and MeHg by 43.94% and 8.16%,respectively,and it also reduces the transport capacity of THg between rice tissues.Therefore,the management of intermittent irrigation is an effective measure to reduce the absorption,accumulation and transport of mercury in rice.(4)The screening of sulfur-oxidizing bacteria(SOB),which can reduce soil mercury activity,combined with biochar,can reduce soil available mercury and inhibit the accumulation of THg in rice. |
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