Selected enzyme activities of urban heavy metal-polluted soils in the presence and absence of an oligochaete, Lampito mauritii (Kinberg)

Soils samples collected from five different areas (S1-S5) around electroplating industries in the city of Coimbatore were analysed for the activities of selected enzymes (cellulase, phosphatase, amylase, urease, and invertase) in the presence and absence of the earthworm Lampito mauritii (Kinberg). Heavy metal analysis of soils showed that chromium (<504 mg/kg) and copper (<28.1 mg/kg) contents were much higher than cadmium (<10.60 mg/kg) except in S5, where cadmium (10.6 mg/kg) was higher than the copper. Except for phosphatase, the activities of all enzymes increased with increasing period of incubation under laboratory conditions, both with and without earthworms. The results of the three-way ANOVA (effect of three factors- worms-with and without addition, soil and incubation time), however, showed that there was no significant difference between enzyme activities (with and without earthworm) and soil and incubation time for amylase and urease activity. Further, no significant difference was found between soils for cellulase activity and between all the above factors for urease activity. The results concluded that though the earthworms died at the end of the incubation period, the resultant increase or decrease in the enzymatic activity may be attributed to the metabolic activities of the worms during their lifetime in the experimental container. Also, the worms after death may have provided suitable substrate for the growth of the microorganisms thereby influencing enzyme activity. (C) 2012 Elsevier B.V. All rights reserved.