| For a long period, the situation that leachate contaminated the farmland around some old landfills in our country has become increasingly serious because of poor impermeable measurements and deficient treatment system of leachate. In-situ combined remediation of contaminated soil by plants and microorganisms is an ideal strategy comparatively, which has been a research hotspot in this field at present. This study is aiming at one farmland soil contaminated by leachate in Chongqing, which has the characteristics that Cd and Pb is out of limits and concentrations of organic pollutants is high and it belongs to compound contamination of heavy metals and organics. Aglaonema Modestum, Spathiphyllum kochii and Calathea makoyana were screened out as remediation plants and the biomass of plants in contaminated soil,accumulative amounts of heavy metals inside plants and remediation effect of the contaminated soil were studied. Aglaonema Modestum and domesticated activated sludge were selected as the tested plant and the inoculating microorganism respectively to conduct the study of combined remediation. The main conclusions are as follows:①Aglaonema Modestum grew well in contaminated soil and had strong tolerance to contaminants. To some extent, Spathiphyllum kochii and Calathea makoyana were toxic in the contaminated soil, but their biomass remained unchanged mainly.Enrichment coefficient of Cd of Aglaonema Modestum, Spathiphyllum kochii and Calathea makoyana were 1.19, 0.92 and 0.60 respectively and Enrichment coefficient of Pb of them were 0.97, 0.72 and 0.72 respectively. Compared with another two plants,Aglaonema Modestum had stronger enrichment capacity on heavy metals. Removal efficiency of Cd and organics of Aglaonema Modestum was better than that of Spathiphyllum kochii and Calathea makoyana, but removal capacities of Pb of Aglaonema Modestum and Calathea makoyana were almost the same.② Addition of activated sludge could improve degradation rates of organics in contaminated soil obviously and reduce the bio-availability of Cd and Pb at the same time. Remediation efficiency of soil was improved dramatically along with the increase of additive amount of activated sludge. Degradation efficiency of organics with activated sludge was the highest when moisture of 20%(m/m), nutrient elements of N:P=3:1(mass ratio), surfactant SDS of 10mg/kg and electron acceptor H2O2 of 10%(m/m) were added into the soil. Fixation effect of Cd with activated sludge was the bestwhen moisture of 10%(m/m), nutrient elements of N:P=3:1(mass ratio), surfactant SDS of 10mg/kg and electron acceptor H2O2 of 5%(m/m) were added into the soil.Fixation effect of Pb with activated sludge was the best when moisture of 10%(m/m),surfactant SDS of 10mg/kg and electron acceptor H2O2 of 15%(m/m) were added into the soil, but nutrient elements of all ratios would increase mobility of Pb.③ Activated sludge could promote the growth of Aglaonema Modestum and improve the plant’s biomass when the experiment of combined remediation of plants and microorganisms was conducted. Addition of activated sludge would reduce concentration of Cd in shoots of the plant, but could increase that in roots. The concentration of Pb in shoots and roots of the plants lowered after adding activated sludge into the soil. Although addition of activated sludge reduced mobility and enrichment capacity of Cd and Pb of Aglaonema Modestum to some extent, it could promote the growth of the plant and improve the biomass of the plant’s shoots and roots,which increased the gross extractive amount of Cd and Pb of the plant substantially and reduced heavy metal content in the soil effectively. Meanwhile, the organics which were difficult to be degraded by indigenous microorganisms in the soil were removed effectively and degradation rates of organics were rising remarkably. Therefore,adoption of combined remediation of appropriate plants and microorganisms can improve remediation efficiency of leachate contaminated soil, which has certain application potential. |
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