| This is typical arsenic poisoning in the hardest hit,at the South west prefecture of Guizhou province,high arsenic coal mining and utilization led to the phenomenon of arsenic poisoning from the mid-20 th century so far,high arsenic coal after the direct arsenic pollution disappeared,but coal mining The arsenic pollution caused by the soil has a lasting effect on arsenic exposure to the local population.It is reported that arsenic pollution in Xing Ren area of agricultural crops(rice and wheat)arsenic content exceeds the national food safety standard limit;grain arsenic pollution will cause sustained harm to human health.In this study,it was found that the arsenic content in the grains was not only affected by the total arsenic content of the soil,but also related to the transformation between the iron oxides and the morphologies in the soil.The results were as follows:(1)Acidification of arsenic and iron in the highly arsenic coal mine wastewater,the lowest pH of the contaminated soil dropped to below 3.0,and the arsenic content in the polluted soil reached 3 times of the local background value the above.The increase of iron and arsenic content in soils also changed the proportion of arsenic and iron in soil,and the proportion of arsenic and iron in contaminated soil decreased by about 10%,and that of crystalline iron and arsenic decreased(2 ~ 3%),the reduction of arsenic and iron were converted into non-crystalline state to increase the arsenic and iron in the soil by about 10%,and there was a close relationship between arsenic and iron in the soil.(2)pH value of Soil,Oxidation-reduction potential(Eh),total iron and organic matter complexation affect the morphological changes of arsenic and iron in soil.Cultivation of cattle dung can increase soil pH and reduce soil Eh,the maximum soil pH can be increased by 2 units,soil Eh can be reduced by more than 30 mv.The content of Fe(?)and available arsenic in the soil decreased with the prolongation of the time,but the high concentration of cow dung extract(25% of the volume fraction)inhibited the iron content in the soil.And promote the activation of arsenic in soil,and promote the increase of arsenic content in soil.Adjusting the content of dissolved organic matter in the soil can reduce the arsenic availability in the soil.(3)The contents of iron and arsenic in the iron films on the root surface of rice showed the trend of the jointing period is higher than the maturing stage.However,the content of arsenic in the iron film of rice with high arsenic concentration was higher than that in jointing stage and grain filling stage,and the change trend was different from that of light pollution or non-polluted rice.(4)There was no correlation between arsenic and arsenic content in rice,and there was a significant positive correlation with arsenic content in iron film,and the correlation coefficient was 0.632(p <0.01).The content of arsenic in most of the grains was lower than the food safety standard(0.5 mg/kg)when rice was planted on arsenic-contaminated soils containing large amounts of iron oxides.There was a significant positive correlation between arsenic content and available arsenic content in the same type of rice iron film,and the correlation coefficient was 0.556(p <0.01).Adding organic matter can reduce the amount of arsenic in the soil,but the addition of organic matter to the arsenic-contaminated soil can lead to an increase in arsenic content in the grain.The uptake of arsenic in the soil by rice is affected by a variety of factors.Among them,the conversion between iron oxides may block the absorption of arsenic in rice grains and may reduce the accumulation of arsenic in rice grains.Therefore,considering only the soil pH and the total arsenic content in the soil may not be able to make a scientific and reasonable evaluation of soil arsenic. |
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