Effect of Municipal Solid Waste Compost Application on the Fractions of Various Heavy Metals in Three Soil Textures

The use of municipal solid waste compost has been considered as an appropriate method for the improvement of soil quality in spite of having heavy metals. For this study, three types of soil textures including clay, loam, and sandy loam soil were used. These soils were mixed with five levels of compost treatments (0, 20, 40, 80 and 120 ton/ha) and this research was done using factorial arrangement in a completely randomized design with three replications. After some basic experiments, the content of heavy metals such as Zn, Cu, Ni, Cd, Pb, and Mn were measured in the various sectors. The results showed that increasing the amount of compost application increased the concentration of heavy metals in all solution, organic, carbonate and residual parts of soils as well as soil pH and EC. The increase in the concentration of these elements was more in the clay soil compared to the other two soil textures. Furthermore, the highest amounts of these elements in decreasing order were as follows: residual fractions> carbonate> organic> dissolved parts, respectively. The maximum amount of heavy metals in the solution part belonged to Mn, while Zn accounted for the minimum amount of heavy metal in the sandy loam. According to the results, it is recommended that, in the application of such compost fertilizers, in addition to measuring the heavy metals contents of these fertilizers, the necessary monitoring should be implemented with regular programs.