The accuracy of environmental risk assessment depends upon selecting appropriate matrices to extract the most risk-relevant portion of contaminant(s) from the soil. Here, we applied the chelatants EDTA and tartaric acid to extract a metal-contaminated soil. Pistia stratiotes was applied as an indicator plant to measure accumulation from the metal-laden bulk solutions generated, in a hydroponic experiment lasting 15 days. Speciation modeling was used to elucidate key geo-chemical mechanisms impacting matrix and metal-specific uptake revealed by experimental work. The highest concentrations of soil-borne metals were extracted from soil by EDTA (7.4% for Cd), but their uptake and translocation to the plant were restricted due to the formation of stable metal complexes predominantly with DOC. Tartaric acid solubilized metals to a lesser extent (4.6% for Cd), but a higher proportion was plant available due to its presence mainly in the form of bivalent metal cations. The water extraction showed the lowest metal extraction (e.g., 3.9% for Cd), but the metal species behaved similarly to those extracted by tartaric acid. This study demonstrates that not all extractions are equal and that metal-specific speciation will impact accurate risk assessment in soil (water)-plant systems. In the case of EDTA, a deleterious impact on DOC leaching is an obvious drawback. As such, further work should now determine soil and not only metal-specific impacts of chelatants on the extraction of environmentally relevant portions of metal(loid)s.

Biochar Engineering Technology Research Center of Guangdong Province School of Environmental and Chemical Engineering Foshan University Foshan 528000 Guangdong China

Department of Agroenvironmental Chemistry and Plant Nutrition Faculty of Agrobiology Food and Natural Resources Czech University of Life Sciences Prague 165 00 Prague 6 Czech Republic

Department of Environmental Geosciences Faculty of Environmental Sciences Czech University of Life Sciences Prague Kamýcká 129 Suchdol 165 00 Prague 6 Czech Republic

Department of Soil Science and Soil Protection Faculty of Agrobiology Food and Natural Resources Czech University of Life Sciences Prague 165 00 Prague 6 Czech Republic

Key Laboratory of Soil Contamination Bioremediation of Zhejiang Province Zhejiang A and F University Hangzhou 311300 Zhejiang China

The James Hutton Institute Craigiebuckler Aberdeen AB15 8QH UK

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Environ Sci Pollut Res Int. 2023 Jul;30(31):77947. doi: 10.1007/s11356-023-27966-3. PubMed

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AMOchar: an amorphous MnOx functionalized biochar to stabilize metal(loid)s in soil and optimize phytostabilization