The biochemical response to different Cr and Cd concentrations in soils amended with organic wastes

The effects of adding municipal solid waste (MSW) or poultry manure (PM) on the biochemical properties of a soil polluted with Cr and Cd were studied. Soil was mixed with Cr(NO3)3 and Cd(NO3)2 to give three concentrations (0, 100, and 250 mg Cr kg−1 and 0, 100, and 250 mg Cd kg−1) in the soil, which was then treated with MSW at a rate of 10% or PM at a rate of 7.6%. The pH and biochemical parameters were measured at 0 and 120 days. An unamended and no-polluted soil was used as control. Compared with the non-polluted soil, for the 250 mg Cd kg−1 treatment the microbial biomass-C, dehydrogenase, urease, β-glucosidase, phosphatase, and arylsulphatase activities decreases 23%, 26.2%, 36%, 34.8%, 18.4%, and 15.8%, respectively, whereas for 250 mg Cr kg−1 treatment the biochemical parameters were slightly lowest than for 250 mg Cd kg−1 treatment. For 250 mg Cr kg−1 soil + 250 mg Cd kg−1 soil treatment, the inhibition percentages of the biochemical parameters increased. After the application of organic wastes in Cr + Cd polluted soil, the inhibition of biochemical properties was greater with the MSW amendment than with PM, possibly due to its higher humic acid concentration.