Effect of Lead and Cadmium on Soil Microbial Activities

Abstract

This study aimed to assess the responses of microbial functional
dynamics and enzymes of the soil to different concentrations of
cadmium (Cd), lead (Pb) and a mixture of cadmium and lead
(Cd/Pb). This study was done for 12 weeks in a greenhouse at
26±2°C and the soil moisture content was regularly rectified to
water holding capacity of 60% maintained using deionized water
throughout the incubation period. Soil treatments Cd1, Pb1 and
Cd1/Pb1 demonstrated the highest acid phosphatase activity (780
mg p-nitrophenol/kg/h) while least activity was observed in
Cd3/Pb3 (533 mg p-nitrophenol/kg/h). Soil treatments with the
highest urease activity are Cd3, Pb3 and Cd3/Pb3 (312 mg
N/kg/3h) while the least urease activity was observed in soil
treatment Cd3 (211 mg N/kg/3h). Soil treatment with the highest
microbial biomass carbon was Cd1 (125 mg /kg) while the least
microbial biomass carbon was observed in Cd3/Pb3 (71 mg/kg).
The soil treatment with the most heterotrophic bacteria,
actinomycetes, and fungi counts were Cd2/Pb2 (72.3 ×108 CFU g1
), Cd2 (54×105 CFU g-1
) and Pb1 (33×102 CFU g-1
) respectively
while the least heterotrophic bacteria, actinomycetes, and fungi
counts were Cd3/Pb3 (16.7×108 CFU g-1
), Cd3/Pb3 (33×105 CFU
g
-1
), Cd3/Pb3 (17×102 CFU g-1
) respectively. The most inhibitive
effects of Pb, Cd, or a mixture of Pb/Cd on soil microbes,
enzymes and properties were observed in week 2. The
supplemented concentrations of the metals studied significantly
altered the microbial communities, profiles and activities.