2002 Test Methods for Assessing Toxicity in Contaminated Soil Presentation

Stantec Consulting Ltd.

From past experience, earthworms seem especially sensitive to the structure and condition of the test soils and, although earthworms can survive in soil with little structure, they rarely reproduce. Since earthworms inhabit soils, they need to be able to move through the soil to live, and they are sensitive to the physical properties of soil, including texture and structure, moisture content, pH, particle aggregation, and aeration of the test soil. In tests where earthworm survival, reproduction, and growth were inhibited, it was unclear whether the observed responses were due to the contaminants in the soil or to the structure and physicochemical characteristics of the soil being tested. In an earlier phase of this project, Stantec Consulting Ltd. (Stantec) conducted a literature review for Petroleum Technology Alliance Canada (PTAC) on the use of soil conditioners to amend ‘suboptimal’ soils to improve their ability to support earthworm reproduction. Based on the findings of the literature review, four soil conditioners were identified for use in Phase 2 of this project. Phase 2 was designed to evaluate the effectiveness of peat, coir, perlite and
gypsum at five amendment levels (0, 2.5, 5, 10 and 15%) to improve the structure and physical characteristics of a clay and a sand reference soil. An experimental negative control soil was also included in the test design; it was an artificial soil (AS) recommended by the Environment Canada biological test method (EC, 2004). The AS was included in the assessment as an internal QA/QC measure of test organism health and performance, technician proficiency, and experimental conditions. Tests were conducted with the earthworm, Eisenia andrei. The goal of the project was to identify potential soil conditioner/amendment level combinations that would improve the physical characteristics of test soils and be suitable and effective for use in toxicity testing. Acceptable soil conditioner/amendment combinations could then be used in future toxicity tests when working with difficult soils, to determine the effects of contaminants on earthworm survival, growth, and reproduction, while reducing the effect of suboptimal soil properties on the test organism.

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