Environment Canada and the Canadian Association of Petroleum Producers (CAPP) have embarked on a five year program to develop, standardize, and validate a battery of soil toxicity tests which can be used to assess the relative toxicity of contaminants in soils to terrestrial organisms. These tests must be applicable to soil conditions typically found in Canadian environments and the test species must be representative of the species of soil invertebrates or plants inhabiting soil ecosystems in Canada. Two of the tests being considered for development are a seed germination test and a seedling growth test using whole soils. The battery of plant species that is being considered for testing includes thirteen species representing six dicotyledonous families and 17 species representing two monocotyledonous families. The species of plants with one exception (Arabidopsis sp.) are representative of both above- and below-ground crop plants grown in agricultural lands across Canada, as well as non-crop plants that are also widely distributed in Canada. One of the objectives of the project is to screen 30 plant species and select ten species that are suitable for toxicity assessment of contaminated soils.
In addition to selection of the most appropriate test species, research has focused on test method development. Comparison of toxicity test endpoints from reference tests permitted the assessment of the variation associated with each endpoint (root length, stem length, wet and dry mass of stem and root) for each species tested to date. The tests were performed using boric acid as the reference toxicant and an artificial soil and a fieldcollected reference soil as control soils. The methods and results from toxicity tests have been summarized and presented with recommendations regarding test species, methods, endpoints, and conditions.