Effect of cadmium contamination with sewage sludge and phosphate fertiliser amendments on soil enzyme activities, microbial structure and available cadmium

Abstract

The effect of Cd pollution (50 mgkg -1 ), with and without sewage sludge (Sw) and phosphate fertiliser (P) addition on soil biochemical activity and available Cd was assessed in a 112 day soil incubation experiment. The availability of Cd decreased with incubation time and was reduced by the sludge and P additions resulting in the following order, Cd>P+Cd>Sw+Cd. With the exception urease and NAGase activities, all other enzyme activities were negatively correlated with available Cd. The total culturable bacterial population was significantly higher with the addition of sewage sludge alone (Sw) than the control during the incubation period (P<0.05). The number of fluorescent pseudomonas decreased with time, but was significantly increased by the addition of sewage sludge. The total fungal populations decreased with time in all treatments, whilst the addition of sewage sludge and phosphate fertilisers increased the fungal population. Addition of sewage sludge in the presence of Cd increased the fungal populations in relation to the addition of Cd alone. The results support the view that Cd contamination has a large detrimental effect on nutrient cycling and microbial activity and the effects of Cd were reduced by P and sewage sludge additions

The effects of heavy metal pollution on enzyme activities and basal soil respiration of roadside soils

“…Also, ASA had a significant negative correlation with total Cu content, and APA had significant negative correlations with total Ni and Fe contents (P<0.05). Several studies demonstrated that enzyme activities decreased with increasing heavy metal concentrations (Karaca et al 2002;Kızılkaya 2004). Tyler (1974) found that there were approximately straight regression lines between enzymatic activity or respiration rate and log Cu+Zn concentration, with highly significant negative regression coefficients for urease and acid phosphatase activity as well as respiration rate.…”

Application of different organic wastes in a soil polluted by cadmium: Effects on soil biological properties

“…1). Also and according to Karaca et al (2002), phosphatase activity decreased when Cd increased in soil. However the results obtained in the urease and β-glucosidase activities are not in agreement with other authors.…”

“…Soil microbial growth and enzyme activities are affected by high concentrations of Cd (Moreno et al, 1999;Landi et al, 2000;Karaca et al, 2002;Moreno et al, 2006). The normal concentration of Cd in soils is between 0.1 and 1.0 mg kg − 1 .…”

Chemical and microbiological attributes of an oxisol treated with successive applications of sewage sludge¹

“…The protease activity has the function to catalyze the hydrolysis of protein-N, giving rise to a mixture of amino acids which in turn decompose to ammonium-N (ammonification reaction), available to plants and microorganisms (Karaca et al, 2002), or are oxidized to nitrate (nitrification reaction); no significant treatment effects were observed on the enzyme activity. These results disagree with those of Melo (2006), who reported increased protease activity in two Oxisols treated with increasing SS rates up to 60 t ha -1 (SS from Barueri, State of São Paulo).…”