Immobilization And Phytoremediation Of Heavy Metal Polluted Soil

Heavy metals are the most important soil pollutants nowadays, soil pollution with heavymetals have affected the health of residents and the environmental safety. This work exploredthe properties of honeycomb briquette combustion residue (HBCR), the effect of composts ofHBCR and certain organic materials on the immobilization of heavy metals in soil, and theeffect of the soil water moisture content on the immobilization of Pb in soil with solublephosphate, materials containing sulfur and certain organic materials were also applied to leadsmelting polluted soil to investigate their effects on the phytoextraction of heavy metals fromsoil. The main results of this work include,i)HBCR was a kind of strong basic, high electric conductivity solid waste, its trace metalcontents were relatively low, washing with water or dilute acid can substantially reduce itsalkalinity and electric conductivity. The surface area of HBCR was between5.09-14.0m2g-1.ii)Water washed HBCR was composted with sludge or/and wheat straw, then thesecomposts were added into heavy metal polluted soil and incubated. The results indicated that,amendments with HBCR or its composts can reduce the DTPA-Pb, Cd and Zn concentrationsof soil for6.13-9.36%,4.09%-12.4%and2.05%-4.24%, respectively. Compared with the soilamended with water washed HBCR, amendments with the composts reduced the DTPA-Pbconcentrations, while those of DTPA-Zn and Cd and Olsen-P were increased. Composts ofHBCR and sludge, wheat straw all resulted in lower plant yields and heavy metal uptakes.iii)a Pb-spiked soil was amended with monopotasium phosphate, phosphoric acid ormonocalcium phosphate, and incubated at the soil moisture contents at2%,10%or25%.After incubation, the analysis indicated that, increasing soil moisture contents resulted inlower DTPA-Pb concentrations. Amendments with monopotassium phosphate resulted inlower DTPA-Pb concentrations compared with other P sources. Higher soil moisture contentsresulted in higher phosphorus availability and lower soil pH. Soil amended with phosphoricacid had higher P availability compared with other P sources. Concentrations of Ca8-P in soildecreased in the sequence of monopotassium phosphate amended soil, monocalcliumphosphate amended soil and phosphoric acid amended soil.iv)A lead smelting polluted soil was amended with sulfur-containing materials or organic materials and incubated. The results indicated that, amendments with sulfur, sludge compostor chicken manure resulted in higher uptake of Cd and Zn by the Sedum plumbizincicola, theuptake of Cd increased104-158μg pot-1, that of Zn increased0.63-1.72mg pot-1, however,these differences were not significant statistically (P>0.05). Amendment with chicken manurehad the highest yield, while that with the sodium thiosulfate had the lowest, however, thedifference was not significant (P>0.05). Amendment with tea seed cake and thiosulfateresulted in lower uptake of Zn and Cd in the shoot of the plant. The results indicated thatsulfur, sludge compost and chicken manure may be used to enhance the uptake of the heavymetals in the lead smelting polluted soil in Henan Province.