Activity and Thermodynamic Parameters of Urease Enzymes in Soils Treated with Some Heavy Metals Under Different Temperatures and Moisture Levels

Abstract

Incubation studies were conducted to reveal effected heavy metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) add at critical concentrations to soils with different texture on urease activity and thermodynamic parameters (Ea and Q10) incubated under different temperatures (10, 20, 30, 40, 50, 60 and 70) °C for 14 days under field capacity and waterlogged moisture levels. Urease activity was measured and thermodynamic parameters were calculated. Results showed that the urease activity increased with increasing temperature of incubation from 10 to 50°C then the activity decreased as temperature increased above 50°C at both moisture levels and at all heavy metals treatments. Increasing moisture level from field capacity to water-logged significantly (P=0.05) decreased urease activity, while increased Ea value, at all heavy metals treatments. The soil texture significantly affected urease activity and thermodynamic parameters (Ea and Q10). Results also indicated that effect of heavy metals on urease and thermodynamic parameters differed according to the soil temperature and the moisture level.