Transfer Characteristics Of Heavy Metals In Soil-Corn-Broiler System And Risk Assessment

With the development of economy and society, more attention has been paid to the pollution of heavy metals. Farmland environment has been damaged seriously due to continuous exploitation of industrial and mining enterprises. One of the main problems is the pollution of heavy metals in soil, which should have a direct impact on crops and threaten human health through the food chain. So the pollution of heavy metals in soil has attracted much attention of the environmental and food safety experts in recent years.In this study, a farmland in Hainan industrial and mining areas has been selected to study the transfer characteristics of heavy metals in soil-corn-broilers system, and their risks have been evaluated, in order to control the pollution of heavy metals in soil and provid real and reliable basis for safe and reasonable usage. Testing and analysis of Cu, Zn,Pb and Cd in the sample were performed by flame atomic absorption spectroscopy. Detail studies are briefly described as follows:1. The soil of an industrial and mining areas of Hainan has been polluted seriously by the heavy metals, the sequence of exceeding the standard of the quantity limit is Cd>Zn>Cu>Pb. Potential ecological risk coefficient of the heavy matals in the soil changes between 82.45 and 6904.52. The average value is 723.18, showing that the soil in the experiment zone has been polluted strongly by the heavy metals. Zn ion contributes to the biggest potential ecological risk index. The average value of the potential ecological risk of the four heavy metals indicates that the pollution of Pb in this area is medium; the pollution of Cu,Cd were strong; the pollution of Zn was very strong. The sequence of the potential ecological risks of the 4 heavy metals in the soil is Zn>Cd>Cu>Pb.2. The corn that growing in the mining area of Hainan is also contaminated by heavy metals. The sequence of different organs of corn that is polluted by the heavy metal is the root, the stem and the leaf, the cob and the corn grain. The quality variation of the metal Zn and Pb changes is more clear than the metal Cu and Cd in various organs of plants. The corn that can be eated in the corn plang is contaminated seriously by the heavy metals. The over-limit ratio of the single factor pollution index of the heavy metal Cu, Zn, Pb and Cd was 76.37%, 45.24%, 100% and 100%, respectively. Target damage coefficients(THQ) show that the sequence that impact the health of local residents is Pb>Cd>Zn, and Cu has been found threatening.3. The broiler that is feeded by the locally grown corn was also contaminated by heavy metals. The content of heavy metals in chicken liver is the largest volume among the different organs of broiler. The average quatitiy of Cu, Zn, Pb, Cd respectively is 10.53mg/kg, 48.40mg/kg, 2.95mg/kg and 1.73mg/kg, which is followed by chicken gizzards, chicken breast, chicken leg. The maximum over-limit ratio of the 4 heavy metals is Cu(98%) in chicken liver samples, and Zn is the lowest(71%) in the chicken leg samples. Target damage coefficients(THQ) show that the influence by eating chicken gizzards on the health of local residents is Cd > Pb, while the threaten has not yet found for Cu and Zn; The sequence of impacting on local residents health by eating chicken liver is Cd>Pb>Zn>Cu; The influence on the health of local residents by eating chicken leg meat is Pb >Cd, and the influence on the health from Cu and Zn have not been found.4. Two concepts(enrichment factor and transfer coefficient) are introduced in this work. The enrichment factor of the 4 heavy metals of root is the largest in the soil-maize system, followed by stems and leaves, corn on the cob and corn kernels. The greatest accumulation coefficient is 98.59% for Cd in the root and the minimal is 8.29% for Pb in grains of corn. The enrichment coefficients of the 4 heavy metal in the chicken liver were as follows: the largest in corn-broiler system, followed by chicken gizzards, chicken breast, and chicken leg meat. The enrichment factor of Cd in hepatic is maximum 98.53% and the Cu in chicken leg is 10.17%.The migration coefficient of heavy metal in soil-maize system is in the order of Cd> Zn > Pb >Cu, in which the transfer coefficient of Cd that transferred from soil to root is the largest 0.595%; while the transfer coefficient of Cu is the lowest 0.003%. The migration coefficient of heavy metal in corn is in the order of Cd>Pb>Zn>Cu. The migration coefficients of heavy metal in corn-chicken system is in the order of Cd> Zn > Pb >Cu, in which the migration coefficient of Cd that transferred from corn to liver is the largest 10.42% and Cu transfered from corn to root is the lowest 2.03%. The migration coefficient of heavy metal in organs is in the order of Cd>Pb>Zn>Cu, with the largest accumulation coefficient of 2.59% for Cd in the liver, the lowest accumulation coefficient of 0.006% for Cu in chicken breast.