Dose-related changes in respiration and enzymatic activities in soils amended with mobile platinum and gold

This study assessed the effect of amendment of Australian soils (acidic, organic matter, Fe-rich, alkaline and silt-rich soils) with mobile platinum and gold (0 to 2000 mg kg(-1)) on soil respiration and the activity of seven key soil enzymes. Platinum amendment significantly reduced soil respiration at almost all concentrations (p < 0.05) in all soils except in organic matter-rich soil where up to 2-fold stimulation occurred at concentrations of up to 500 mg kg(-1). Amendments with mobile Au-complexes also inhibited soil respiration irrespective of soil type, except for the Fe-rich soil. Platinum and Au amendments also impaired enzyme activities across most concentrations and soils, except alkaline soils. Overall, while mobile Au appears to be somewhat more toxic to soil microbial communities than Pt, toxicity levels appear to be largely determined by soil properties.