| With the development of society, heavy metal pollution in soil-plant system gets more and more serious in our country and it receives a lot of publicity. Huludao city, a typical nonferrous metallurgy city, and Yushu city, which lies on the golden corn zone, were regarded as the research areas. The bioavailability of Cu and Cd was analyzed by comparing Cu and Cd accumulation characteristics in the soil-maize system of the regions. On this basis, the factors affecting the Cu and Cd bio-availability were revealed for contributing to related research, future decision-making and environmental protection.(1) Cu concentration in soil ranged from 9.81 to 93.40mg·kg-1 with the average content of 57.90 mg·kg-1 in Huludao city, which was five times higher than Yushu city. And, Cd content was 1.76 mg·kg-1 in Huludao, which enrichment degree was far higher than that of Yushu. It showed that maize soil of Huludao was under the intense human activity intervention and large amount of exogenous input heavy metals influenced soil heavy metal pollution status. The result of geoaccumulation index reflected that different Cu enrichment existed in mostly Huludao maize soil and Cd was partial to severe pollution in the all. Comparatively speaking, Cu and Cd accumulation were not obvious in Yushu maize soil. Belonging to Zinc smelting and chlor alkali industry in Huludao, heavy metal pollution degree in maize soil was much deeper than Yushu.Cu and Cd effective content in Huludao maize soil were both much higher than that of Yushu. But the bioavailability coefficients of Cu and Cd were higher conversely. In addition, the bioavailability coefficients of Cd was lower than Cu obviously. These results were closely connected with the basic physicochemical property and speciation of soil heavy metals. Studying on the different organs of maize plants, the results showed that Cu and Cd contents in maize roots were highest and the lowest contents were in fruits. In the same maize organs, Cu content in maize plants in Huludao city was higher than that of Yushu city. In the study areas transfer coefficient of Cu in plant organs in the descending order was as follows: leaf > root > stem > fruit > bract. The transfer coefficient of Cd was as follows: root > leaf > bract> stem > fruit.Correlation analysis and multiple regression model were applied to analyse the influence of organic matters and p H on Cu and Cd effective contents in study areas. It turned out that Cu available content increased with the increase of p H when the soil p H<7 in Huludao maize soil. And when the soil was alkaline, the effective content of Cu decreased rapidly with the increasing of p H value. But the content of Cu in the maize soil of Yushu had a significant positive correlation with the p H value. The effective state content of Cd and soil p H showed a significant positive linear correlation(R2=0.62,p<0.001) in Huludao. For the maize soil in Yushu, the content of Cd in soil increased with the increase of p H when it was in the 5 ~ 5.75 range. However, the effective content of Cd was negatively correlated with p H. By comparison it can be found that Cu and Cd available contents in Yushu maize soil had a significant positive correlation with soil organic matter, but the correlation was not strong in Huludao city. Natural environment factors are diverse and complex, so the influence factors on the Cu and Cd available contents in different regions are different. |
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