Variation in microbial biomass and enzymatic activities in metal contaminated soils during storage at low temperature (4°C)

ABSTRACT Microbial response to soil storage at low temperature in limed and unlimed samples has not been investigated. For this study, soil samples were kept at 4°C for six weeks. Soil microbial biomass was determined using phospholipid fatty acid analysis (PLFA). Nine enzymes were targeted including β-glucosidase (BG), cellobiohydrolase (CBH), β-N-acetylglucosaminidase (NAGase), aryl sulfatase (AS), acid phosphatase (AP), alkaline phosphatase (AlP), glycine aminopeptidase (GAP), leucine aminopeptidase (LAP), and peroxidase (PER). PLFA results revealed a significant increase in total microbial biomass in limed area compared to unlimed soil samples. Microbial biomass decreased during the first two weeks of storage and remained unchanged thereafter for both limed and unlimed samples. Analysis of microbial activities revealed that most enzymes inconsistently decreased over time during storage at 4°C. Activities of BG, CBH, NAGase, AlP, AS, GAP, LAP were significantly higher in limed compared to the unlimed samples. Overall, the levels of activities of most enzymes in limed soils decreased significantly after the second week of storage and remained unchanged thereafter. The reduction of enzyme activity in the unlimed soil samples varied over time, with some enzymes such as LAP increasing on the sixth week. PER activity decreased after two weeks and increased thereafter.