Study On Bioavailability Determination Of Heavy Metals In Four Typical Soils

Currently, with the widely use of waste water, sludge and other solid waste, the soil polluted problem is very serious. The full amount of the heavy metal pollution is detected in the soil environmental monitoring. But the full amount could not refer to the transmission to the plant. There is not direct relationship between the full amount of heavy metal and biological effectiveness. The characteristics of the biological effectiveness could evaluate the trend of heavy metal transmission in the plant. In this study, we make the sewage aludge as the source of heavy metal, and measure the bioavailability of the mixture of soil and sewage sludge with plant seedings. And compared with the chemical extraction method, we can set up a standard method to measure the bioavailability with different soils. The results show that:(1) When the concentration of EDTA-2NA is 0.05 mol·L^-1, the chelating ability is very effective. And the EDTA-2NA is a good soil extractant. CaCl2 and HAc-NaAc, as acid inorganic extraction, has better extraction efficiency, compared with Cu, Zn, and Ni.(2) When the concentration of EDTA-2NA is 0.05 mol·L^-1, the content of Cu and Zn in the extraction liquid increase with the soil water ratio increases. When the concentration of DTPA is 0.05 mol·L^-1, the content of Cu and Zn stay the same with the different soil water ratio. Therefore, the 1:10 is the best soil water ratio.(3) With the wheat seeding method, the bioavailable heavy metal content decreases in such order: Cu, Zn, Ni, Cd. The Ni and Cd content of EDTA and DTPA extraction method is larger than wheat seeding method. The correlation is obtained between the content of Cu, Zn and seeding method.(4) The heavy metal content in the sludge treatment is larger than the CK treatment for the four types of soil. Because of the absorbtion of the root, the heavy metal content on the root is not increased with the increasing sludge concentration.(5) The optimization of wheat seeding method has been founded. 14 days is fit for the seed growing. The seeds is shined 12 hours every day. In these 14 days, the growth of wheat is in good condition, and the wheats tend to be prosperous with the decreasing sludge concentration.(6) The trend of number of plant and the dry weight on the root is just the same. But the dry weight of the root and on the root is opposite. The biomass reaches the largest content when the sludge concentration is 5%. The best sludge amount of heavy metal bioavailability could be measured by the wheat seeding method.