The Impact of Heavy Metal Interactions with pH, Organic Matter and Clays on Soil Toxicity, Under Wastewater and Biosolid Reuse

An experiment of randomized block design, was conducted in a soil which was simulated to create equidistant levels between the desired characteristics of soil, such as clay, organic matter, pH, electrical conductivity, heavy metals and micro and macro nutrients, respectively. These simulated soil characteristics were attained by applying the appropriate quantities of the following substances on virgin soil: (i)- sterile fine particle sand of the type, (ii)- CaO, biosolids (iii)- mixtures of salts of heavy metals, for the enhancement of the equidistant levels between the soil characteristics, and (iv)- biosolids for the enhancement of the organic matter. The aim of the experiment was the investigation of the relation between soil toxicity as expressed by the soil toxicity indices and the interactive elemental contribution in heavy metals and the impact of incubation time over a period of 358 days. The studied interactions included heavy metals with pH, organic matter, clay, electrical conductivity, heavy metals and micro and macro nutrients. The regression analysis of the experimental soil data produced numerous statistically significant elemental interactions that ultimately contributed significant levels of heavy metals related to soil toxicity and was thus shown that these interactive activities constitute important regulatory factors of soil toxicity.