POTENTIAL NITRIFICATION RATE AS A TOOL FOR SCREENING TOXICITY IN METAL-CONTAMINATED SOILS

摘要

A potential nitrification rate test (PNR) was used to identify metal toxicity in field-contaminated soils. The test was applied to metal salt-spiked soils, to 27 uncontaminated soils, and to 15 soils that are contaminated by former metal smelting activities. Four agricultural soils (pH 4.5-6.6) were spiked with various rates of CdCl_2 (0-200 mg Cd/kg dry wt) or ZnCl_2: (0- 3,000 mg Cd/kg dry wt) and were equilibrated more than nine months prior to testing. The soil Zn EC50s of the PNR were between 150 and 350 mg Zn/kg dry weight. No continuous decrease of the nitrification with increasing Cd application was observed. The nitrification rate was reduced by between 50 and 80/100 at the highest Cd application in all soils.