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PH09 Plant Ecotoxicology
(PH111) Critical tissue concentrations of metals in plants.
Houkal, D1, Mortensen, L1, 1 Integral Consulting, Inc., Seattle, WA, USA
ABSTRACT- Screening level ecological risk assessments often include an evaluation of impacts to plants using benchmarks that are based on the metal concentrations in soil. The source of these benchmarks are often toxicity tests where a highly bioavailable form of the metal is applied to the soil. Application of these benchmarks may result in unrealistic estimates of risk as benchmarks may occur at concentrations approaching or below background levels. Typically, metals must be taken up by plants to elicit a toxic effect. In this paper, we explore the development and use of plant tissue-based thresholds for metals in ecological risk assessment. Inter-specific variation in the phytotoxicity of a metal limits the applicability of a single benchmark across species. We also examine the magnitude of inter-specific variation in the context of other sources of variation. Various toxic endpoints are evaluated as to their sensitivity as indicators of phytotoxicity. A framework for developing critical plant tissue concentrations is proposed for selected metals, which can be used to supplement existing soil benchmarks. The costs and benefits of using tissue-based plant thresholds are evaluated.
Key words: metals, phytotoxicity, tissue-based
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