| When the economic development and the emergence of industrial and mining enterprises, a large number of waste water poured into the bodies of river and lake with heavy metals,then the sediment pollution was formed with the enrichment of heavy metals underwater.The sediment with heavy metal pollution is not only difficult to control,but also become an important endogenous heavy metal pollution for water bodies.Phytoremediation reduces the risk of heavy metals in the external environment by the absorption of heavy metals in sediment with plant growth. And as a cheap and safe repair techniques, Phytoremediation is increasingly used in the treatment of heavy metal contaminated sediments.Currently,the capacity of adsorption and tolerance of heavy metals are not only consider for the plants, how to improve the efficiency of phytoremediation with amendments will be becoming a hotspot in future research.Humic acid and hydroxyapatite were used as amendments to prepare for different proportions of sediments.Water mint,Maidenhair,Iris and Cattails are potted in different proportions of sediments for studing the restoration of Cd、Cu、Pb、Ni to find the best proportion with the maximum repair efficiency.In the pot test of Watermint,the environment with the highest enrichment of Cd、Cu、 Pb、Ni are HAC (5%o),but the Cd improved 14.72% as obviously compared with blank.In the pot test of Cattail,the enrichment of Cu and Pb is low,but HAC(3%o) can improve the efficiency of repairing Cd and Ni with improving 6.72% and 5.02% Compared with the blank sample.In the pot test of Maidenhair,HAC(3%o) and HAP (5%) were the environment with the highest enrichment of Cd,with improving 9.53% and 10.71% Compared with the blank sample.HAP(5%)and HAC(1%)were respectively the environments with the highest enrichment of Pb and Cu with improving 5.20% and 8.15% compared with the blank sample.In the pot test of Iris,HAC(3‰) and HAP(3%) were the environments with the highest enrichment of Cd,with improving10.59% and 5.10% compared with the blank sample.The sediment without plants were extractted by Tessier sequential extraction method, with analyzing the situations of morphological changes by the mechanism in the test and drawing a conclusion that Humic acid and Hydroxyapatite can change the morphological distribution of heavy metals.With the addition of Humic acid,the Cd available state decreased to the minimum of 28.08%,the residual and potentially available state of Cd were rose from 5.60% and 49.66% to the maximum 15.55% and 56.37%.The residual and potentially available state of Pb were decreased from 54.28% and 22.28% down to the minimum 48.11% and 14.86%,resulting in the increase of potentially available state of Pb to the maximum 37.03%.The residual state of Cu decreased from 46.18% down to 32.30%,the potentially available state and available state of Cu were rising to the maximum 14.20% and 56.42%,in the condition of HAC(1‰)and HAC(5%o).The residual state and available state of Ni were changed very little.with mutual transformation among the potentially available state of Ni, which reduced the proportion of carbonate-bound Ni and the improvtion of Fe,Mn and organic fraction.With the addition of Hydroxyapatite,the Cd available state was decreased from 45.08% down to22.50%.The residual and potentially available state of Cd were rose from49.66% and5.26% to 59.58% and 17.92%.the Pb available state were decreased from 22.80% down to 11.20%,The residual state was rose from 54.28% to 61.04%,but the potentially available state changed little.The residual and potentially available state of Cu were rose from 46.18% and 43.36% to 49.28% and 47.69%,with the Cu available state dropping. The residual state of Ni changed little,the Ni available state falled to 1.37% and the potentially available state of Ni was improved to 54.61%. |
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