Effect of Cadmium and Lead Contamination on Biological Quality of Soil and Rapeseed (Brassica napus) Growth

Cadmium and lead are heavy metals and cause toxic effects on plants. Soil, as one of the components of the ecosystem of the plant's growing environment and the habitat of diverse organisms, is encountered with a variety of biological stresses. Cadmium and lead have toxic and potential effects on the activity and composition of living organisms. Microbial parameters can be used to evaluate the quality of contaminated soils. The purpose of this study was to evaluate the effects of cadmium and lead contamination on soil quality and plant parameters in order to evaluate phytoremediation of rapeseed. This experiment was conducted in a completely randomized design with three replicates to investigate the effect of cadmium levels (0, 3, 5 and 10 mg/kg soil) and lead levels (0, 100, 300 and 600 mg/kg soil) on rapeseed plant (Brassica napus) in greenhouse conditions. Stem and root length, some physiological characteristics, cadmium and lead concentrations in shoot and root and some biological parameters of soil were evaluated. Based on the results of this study, increasing soil contamination of lead and cadmium lead to a significant increase (P <0.05) in the concentration of these elements in the shoot and root and also in the metabolic coefficient (qco2). Cadmium and lead decreased significantly (P <0.05) plant height, microbial biomass carbon (MBC), microbial respiration and substrate-induced respiration (SIR). Therefore, the elements of cadmium and lead cause changes in rapeseed and microorganisms in the soil.