The Effects Of Different Remediations On Bioavailability Of Heavy Metals In Vegetable Soils In Hangzhou

Heavy metals were introduced to soil environment from crustal mainly via anthropogenic industry activities and then threaten human health by bioaccumulation. Heavy metal contaminated soil is a vital origin of trance elements residues in crops. The results of heavy metals evaluation, which was carried out in five typical vegetable farms in Hangzhou, indicated that these soils were not polluted by Pb, Cu and Zn as their concentrations and Nemerow pollution index 0.7 were under environmental quality standards for all soils. While soil Cr, As and Cd need to be alarmed, since parts of soil sample plots were slight or moderate contaminated by them. In addition, the heavy metal enrichment factor of leafy vegetable, mushroom and root vegetable were much stronger than in solanaceous vegetable, legumes and melon vegetables.Different remediation technologies were then carried out based on the survey results. The results of phytoremediation pot trial showed that ryegrass obtained better efficiency of Cu, Cr and Cd eliminant and Pb, Cr and Cd retention, while bermudagrass was more efficient on Pb and Cr rprotein and tolerant for multiple heavy metal contamination. With the deepening heavy metal contamination, much compost was required to preserve normal growth as trance elements could obstruct nutrients assimilation by plants. According to the pot trial, the property of selected soils sample could be improved by planting ryegrass combined with 20% compost(w/w) addition; the light polluted soils could be optimized by ryegrass cultivation combined with 10% compost(w/w) addition; the moderate contaminated vegetable soils could be remediated via adding 20% compost(w/w) combined with ryegrass cultivation. Furthermore, the detail remediation strategy could be adjusted in accordance with key pollutants and pollution levels.The results of heavy metal immobilization pot trial showed that application of biochar or fly ash worked well not only in acid soils but also in neutral soils. A better ameliorative effect of inhibiting heavy metal leaching was observed in fly ash treatments than in biochar groups, but its neutralization effect was relatively short-term. While biochar addition got more improvement of crop yield, bioconcentration factor(BCF) decrease and soil properties. The sustained release effect of fly ash or biochar was also obtained in this pot trial. In addition, the tolerance of solanaceous vegetable for compost was better than foliage vegetable. According to the pot trial, 5% biochar(w/w) combined with 20% compost(w/w) were selected as optimum reclamations for planting foliage vegetable and solanaceous vegetable in Liangzhu soil, while the remediation strategy that combined 5% fly ash(w/w) with 10%(w/w) compost was a better choice for foliage vegetable and solanaceous vegetable cultivation in Qiaosi soil.