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<p>The type of food crop grown on contaminated soils strongly affects the risk of human exposure to toxic metals. Plant species, crop type, and even cultivar have profound effects on soil-to-crop transfer of metals. For this reason, a more detailed assay of metal transfer coefficients for common crops is needed, as broad generalizations presently used (e.g., "there is negligible transfer of As from soils into fruit crops") may not adequately assess risk to the food chain. Soil tests, historically designed to test for essential plant macro- and micro-nutrients need to be redesigned and recalibrated to estimate risk of human and ecosystem exposure to toxic metals, particularly arsenic, lead and cadmium, through the consumption of food crops and plants. These soil tests ideally need to be sensitive to soil properties such as pH, because toxic metal bioavailability and plant uptake are strongly influenced by differences in soil properties. Some commonly used soil extractants for toxic metals, such as Mehlich 3, are quite insensitive to these soil properties. The specific objectives of the present project are to: 1. Measure the potential for As, Pb and Cd transfer into different vegetable and fruit crops when grown in contaminated soils. 2. Assess the role of soil properties, particularly pH, organic matter content, texture and soil redox potential in affecting phytoavailability of the metals. 3. Assess the effectiveness of soil remediation techniques, including stabilization (by soil amendments) and phytoextraction (by hyperaccumulator plants). Develop web-based educational materials and conduct outreach to ag. advisors, testing labs, farms and gardening communities, elucidating the behavior of toxic metals in soil, their potential for crop uptake and the pros and cons of different methods of soil testing for toxic metals and remediation of contaminated soils. We will provide interpretation of the potential health impacts of these tests and describe inherent limitations or uncertainties in the tests. Soil remediation approaches with proven effectiveness will be described and explained. </p>
<p>NON-TECHNICAL SUMMARY: Toxic metals in food and water are now known to pose a greater hazard to human health than previously believed. Contaminated soils are an important source of human exposure to these toxins, particularly in urban and previously industrial areas. This project will define the conditions under which arsenic and lead transfer from soils into crops can be minimized, identify crops prone to uptake of these toxic metals, and test methods of amending or remediating soils to remove or stabilize the metals in less soluble forms. The experimental approach will utilize field and greenhouse studies of crops with known tendencies to bioaccumulate these metals, and measure the transfer of toxic metals from contaminated soils into the edible plant tissues. The goal of this project is to reduce exposure of gardeners and consumers to toxic metals in vegetables, fruits and other food crops through science-based management of soils to reduce toxic metal uptake into crops, and through selection of crops which tend to exclude these toxic metals. </p>