Concentration Dependent Effect of Heavy Metals on Soil Carbon Mineralization

Abstract

The present laboratory investigation was conducted to assess the effect of heavy metals on carbon mineralization. Soil was treated with three concentrations (50, 100 and 150 µmol g-1 soil) of two heavy metals (Cd and Zn) in a factorial combination of treatments replicated four times. Determination of carbon mineralization was carried out at 3, 7, 14, 21, 28, 42 and 56 days after metal treatments.. The amount of CO2-C released from heavy metal treated soils was found to be decreased at an increasing rate during the first 28 days, followed by slow release as incubation progressed. The total amounts of CO2-C released were 448, 382 and 348 mg kg-1 soil respectively for soils treated with 50, 100 and 150 µmol g-1 soil of Zn. The corresponding figures for Cd treated soils were 406, 354 and 282 mg kg-1 soil implying that dose-dependent reduction in cumulative CO2-C released from soils. The inhibition of carbon mineralization was found to be high in Cd treated soils than that of Zn treated. Therefore, tolerance and adaptation of the microbial community is likely to be related to the concentration and the type of metal. According to the results, carbon mineralization can be considered as possible indicator of soil pollution by means of heavy metals.