An evaluation of extractants for assessment of metal phytoavailability to guide reclamation practices in acidic soilscapes in northern regions

Abstract

Although soil organic matter and nutrient bioavailability in metal-impacted soilscapes of Sudbury, Ontario, are potentially limiting full ecological recovery, total metal content was used as the critical driver for a 2008 ecological risk assessment. The current greenhouse study evaluated chemical extractants to predict bioavailability of nutrients and contaminant metals to indigenous grasses (Deschampsia). Single extraction methods (0.01Mstrontium nitrate, water, 0.01Mcalcium chloride, 0.1Msodium nitrate, 1.0 M ammonium nitrate, 0.1 M lithium nitrate, 1.0 M magnesium chloride, 0.11 M acetic acid, 1.0 M ammonium acetate, 0.05 M ammonium-EDTA, pore water) were examined to assess availability of potentially phytotoxic metals and nutrients in smelter-impacted soils. Extraction procedures to predict phytoavailability were either soil concentration or plant tissue concentration and element dependent. Total and extractable metal concentrations were more correlated for regional contaminant metals (e.g., copper, lead, arsenic, selenium) released by the smelting industry than non-contaminant ones (e.g., iron, calcium, potassium, boron, zinc, molybdenum). The lack of relationship between total and extractable concentrations for most non-contaminant metals suggests total concentration is not a good indicator of phytoavailability for nutrient elements. Stronger correlations between shoot tissue and extractable concentrations were observed for less aggressive extractants (pore water, water, lithium nitrate) reflecting their suitability in predicting phytoavailability over most aggressive ones (except ammonium nitrate).