| China is the country with the largest rice production and consumption in the world,but the phenomenon of rice cadmium pollution is quite serious.The eastern Hunan region is dominated by hills,and Liling City is a typical area of hilly river ditch.In this paper,the rice fields in Liling City were selected as research objects to study the distribution characteristics of typical cadmium-contaminated soil-rice system elements in hilly areas.The occurrence state of heavy metal elements in soil was studied.K-Si-Ca mineral fertilizer was applied on the basis of conventional fertilization in local paddy fields.And the effect of mineral fertilizer on the cadmium-contaminated farmland was studied.Heavy metal pollution assessment of rice soil was carried out using a variety of heavy metal pollution assessment methods.Finally,the sources of heavy metal pollution,the differences of rice varieties,the relationship between elements in brown rice and the effects of mineral fertilizer were discussed.The main conclusions are as follows:(1)The average Cd content of early rice brown rice was about 3.8 times of the national standard,and the average content of Cd in late rice brown rice was about 10.4 times of the national standard.The average As content of early rice brown rice was about 1.1 times of the national standard.The other elements in the early and late rice did not exceed the national standard value.(2)Light rare earth elements are enriched in early rice soil and late rice soil,and rare earth elements are mainly derived from Soil-forming parent rock.The values of ?Eu and ?Ce in the early and late rice soils were basically the same,indicating that the physical and chemical conditions of early and late rice soil formation were consistent.(3)The average content of Cd in brown rice is higher than that of the corresponding soil,and the average content of other elements is lower than that of soil.There is a strong negative correlation between Cd and Cu in brown rice.The absorption of Cd by rice inhibits the absorption of Cu and Zn.(4)There was Morphological analysis of heavy metals in conventional soil.And found that the proportion of weak acid dissolved state was from large to small: Cd>Zn>Pb>Ni>Cu>As>Cr.It indicated that the biological activity of Cd was the highest and Cr was the lowest.Cd,Zn and Pb were the three elements with the highest biological activity in rice soil.And the proportion of weak acid dissolved Cd to total Cd averaged 45.77%,indicating that Cd is very lively in farmland soil.(5)The single factor index method,the geological accumulation index method,the enrichment factor method and the potential ecological hazard index method were used to comprehensively evaluate the pollution status of soil heavy metals,indicating that the soil is mainly Cd and Pb pollution.And Cd is moderately polluted,Pb is light to moderate pollution.The cluster analysis method and factor analysis method were used to analyze the source of soil pollution.It was found that the sources of Cd and Pb pollution in farmland were mainly Panjiachong lead-zinc deposit.(6)The cadmium-contaminated farmland was treated with mineral fertilizers of different strengths.It was found that after applying the mineral fertilizer,the pH value of the soil was almost unchanged,and the Cd content of brown rice increased slightly.The biological activity of soil Cd did not change much.In this study,the mineral fertilizer did not have a significant effect on remediating cadmium pollution in farmland and inhibiting the absorption of cadmium by rice. |
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