Regulation Of Heavy Metal Of The Soil In The Indigenous Zinc Smelting Area Of Hezhang County

We studied on the heavy metal of the soil in the indigenous zinc smelting area of Hezhang County in Guizhou province with experiment in the field, the nursery and the laboratory. It will offer basic information for the reclaimed soil in the indigenous zinc smelting area.Using limestone with different thickness on the waste residue for the regulation of the fixation and migration in Caoziping of Hezhang County, then covering clean soil with different thickness on it and planting bean, Chinese cabbage, maize and potato. Using limestone as ventilation can reduce the value of the heavy metal in edible part in the crops after analyzing the heavy metal in the edible part of bean, Chinese cabbage, maize and potato. At the same time we can know that maize is the crop that the enrichment factor of heavy metal is the least and it fit for the reclaimed soil. The enrichment factor of heavy metal of Chinese cabbage is the biggest and unfit for the reclaimed soil. The thickness of limestone covered with 25kg per m2 is better. Dealing with limestone, pure alkali and caustic soda as alkaline channel and analyzing the heavy metal in the soil, we can find that limestone is a good fixing heavy metal sorbent.Pot-experiments were carried out to study heavy metal accumulation in Chinese cabbage planted in the polluted soil from the indigenous zinc smelting area of Hezhang County. The potted soils were treated with addition of humus, EDTA and limestone, respectively. Chemical properties, DTPA-exactable concentrations of Pb, Zn, Cd of soil, Chinese cabbage growth and its accumulation for heavy metal were determined in each pot-experiment. The results showed that available P of soil was increased from 0.5mg/kg to 10mg/kg , DTPA-available Pb, Zn and Cd of substrates dropped by 83.9%,23.1% and 79.4%,respectively, biomass in Chinese cabbage increased by 5.97 times, and Pb, Zn and Cd contents in Chinese cabbage dropped by 97.2% , 94.7% and 89.4%,respectively. It showed that major constraint factors on growth of Chinese cabbage in polluted soil were pH value and available phosphorus. Pb and Cd contents in Chinese cabbage were positive to DTPA-exactable Pb and Cd in soil. Application of limestone was a practical and effective approach to remediate the polluted soil in the indigenous zinc smelting areas.We use limestone, fly ash, organic matter, clay and actived carbon as sorbent to adsorb heavy metal in the laboratory and find that limestone is the best sorbent. We use HNO3 to adjust the pH value of the waste residue and NaOH to adjust the pH value of the polluted soil .The content of Cd can not be detected above pH6.11 in the waste residue and it will increase with the value of pH decreasing. The content of Pb can be examined below pH4.84.There is a different content of the soluble Zn in the different value of pH in the waste residue .Zn in the waste residue will begin to dissolve largely when the value of pH is below about 5.5. The content of the soluble Cd will decrease when the value of pH increase to 9, then it will increase. The content of the soluble Pb and Zn will decrease when the value of pH increase to 9, then it will increase. The content of the exchangeable mode through determinating the chemical speciation of heavy metal in the waste residue and the polluted soil with the five-step extraction treatment is very little and even below to the background soil, but the other content of the various geochemical modes are much higher than that in background soil. The content of the exchangeable mode in the polluted soil is much higher than that in background soil. The content of Cd of the exchangeable mode and the carbonate mode is higher than that in waste residue and the content of Pb and Zn of the exchangeable mode is higher than the background.