The aim of this study was to measure and compare methane oxidation rates of arable and grassland soils that received 7.5t ha⁻¹ y⁻¹ of noncontaminated aerobically treated sewage sludge for ten years. Arable soils showed generally lower methane oxidation rates (from 6 to 15∗10⁻³ h⁻¹) than grassland soils (from 26 to 33∗10³ h⁻¹). Oxidation rate constants (k) of soils amended with sewage sludge were remarkably close to their respective untreated controls, but a soil, that had received a tenfold sewage sludge application (i.e. 75 t ha⁻¹ y⁻¹), showed a statistically significantly higher k-value. Laboratory addition of up to 1000 mg Pb g⁻¹ soil to this soil did not cause any significant change in methane oxidation, but caused a decrease from 13.9 to 10.9×10⁻³ h⁻¹ in the control soil. Addition of Zn was much more toxic than Pb, with a significant decrease at 300 μg g⁻¹ soil rate and an almost complete inhibition at 1500 μg g⁻¹ soil rate. Higher resistance was evident of sewage sludge treated soil in comparison to control soil, for both biomass C and CH₄ oxidation activity.
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