Effects of ethylenediaminetetraacetic acid and ammonium sulfate on Pb and Cr distribution in Kochia scoparia from compost

In a municipal solid waste (MSW) compost field, Kochia scoparia , an easy-to-grow weed plant, gradually invaded the experiment site and became the dominant species after 4 years' succession. Ethylenediaminetetraacetic acid (EDTA) solution at five rates 0, 25, 50 mmol L-1, 25 mmol L-1 + 1 g L-1 ammonium sulfate (NH4)2SO4, and 50 mmol L-1 + 1 g L-1 (NH4)2SO4 was added to the tested plant root medium. The effects of EDTA and (NH4)2SO4 on Pb and Cr distribution in K. scoparia were investigated. Results suggested that plant biomass increased greatly with height, showing an 'inversion pyramid' pattern in spatial structure. At the level of 50 mmol L-1 EDTA, single additions and combined additions with (NH4)2SO4 increased Pb and Cr concentrations in plant shoots at different heights. Lead and Cr uptakes increased toward the top of the shoot. Combined application of 50 mmol L-1 EDTA and (NH4)2SO4 increased Pb uptakes by 21.6, 19.2, 111.3, 124.3, and 154.0 % in 0-30, 30-60, 60-90, 90-120, and over 120 cm spatial shoots, respectively, as compared to those of controls. The increment for Cr uptake was 244.5, 281.7, 100.0, 77.2, and 187.4 %. The relationship between Pb and Cr concentrations in plant shoots and spatial height was found to be positively linear and statistically significant at 1 % level at 50 mmol L-1 EDTA alone and 25 mmol L-1 EDTA together with (NH4)2SO4. Results presented here indicated that K. scoparia had potential in removal of Pb and Cr from MSW compost with the combined application of EDTA and (NH4)2SO4.