Variations Of Polluted Soil Physicochemical Properties And Heavy Metals Bioavailability After Biochar Remediation

In recent years, due to the rapid development of mining and smelting industry, metal smelting process emissions waste residue, waste water and waste gas, which contain heavy metal into the soil through various channels, resulting in the surrounding soil ecological system is destroyed, and soil environmental quality is declining. The security of soil environment is not only related to the whole ecological environment security, but also is very important to the safe of agricultural production. At present, the technologies for remediation heavy metal contaminated soil are various. Using biochar with special structure for the remediation of heavy metal contaminated soil provides a new practical technique, has become the research hotspot in the world..This study aimed at farmland near zine smelter which was polluted by heavy metal,using field experiment adding different concentration(0, 5, 10, 15 g/kg) of biochar, and planting ordinary glycine max, by measuring each constituent content of different treatments soil and plants, discusses the variations of polluted soil physicochemical properties and heavy metals bioavailability after biochar remediation. The main results are as follows:(1) With the increase of applying biochar content, pH of soil gradually increased, EC value of the soil increased. After planting glycine max, the conductivity of soil has a little increase, the impact of biochar on the soil conductivity is still exist, and increased with the applying of biochar.(2) The application of biochar can significantly improve the content of organic matter in the soil, and increased with the applying of biochar, with the control group of 14.4g/kg gradually increased to 17.3g/kg, increased by 20.3%. After planting glycine max, the organic matter content in the soil was further improved, the control group of 15.4g/kg increased to 23.3g/kg, which increased by 51.7%. Compared with non-planting crops, the influence of the biochar is more significant.(3) Biochar application could increase the content of N, P and K in soil; After planting glycine max, concentration of N and P in the soil was not affected, still increase with biochar’s application, but the content of K in the soil would decrease when Compared with non-planting crops, and the effects of biochar to K content of soil almost disappeared, K content is no longer changes with the addition of biochar.(4) After the addition of biochar, the total content of humus substances increased, and the compositions of humus in the soil were changed. The HA decreased with the addition of biochar. FA and HM content increased with the addition of biochar. After planting glycine max, the compositions of humus in the soil along with the change same as non-planting.But the trends of HA and FA decreased, while the trend of the change of HM increased.(5) Biochar add into the soil will affect the formation distribution of heavy metals in soil, which reduced obviously the bioavailability of heavy metals in the soil. After planting glycine max, the effect of biochar on the bioavailability of heavy metals in soil remains, and the changes are basically the same.(6) The accumulation of heavy metals were diverse in different parts of glycine max plant, Cu and Ni mainly accumulated in the roots of glycine max plant, the amounts of Cd, Pb, Zn were high which were accumulated in the stems and leaves of glycine max plant. Biochar applied into the soil can effectively reduce glycine max’s plant absorption of heavy metal accumulation in the soil, especially heavy metal accumulation at the root of the plant are significantly decreased. But the heavy metal accumulation of glycine max seeds was significantly higher than Food Sanitation Standards. It cannot to be eaten directly.