Effects of Inorganic and Organic Amendments on the Predicted Bioavailability of As, Cd, Pb and Zn in Kitchen Garden Soils

International audienceModerately contaminated garden soils can benefit from gentle remediation options such as soil amendments, which improve soil functions and agronomic potentialities while decreasing environmental and human risk. This study aimed to analyze the effects of doses of variouscommon soil amendments generally applied by gardeners on the predicted bioavailability (i.e.,extractability) of metal(loid)s (i.e., As, Cd, Pb, and Zn) in contaminated kitchen garden soils. Fourteen different amendment mixes (i.e., a green waste compost with two degrees of maturity used alone and in combination with zeolite, three organic fertilizers, two calcareous amendments, two natural siliceous or alumino-silicate amendments, and one potting soil) were tested on three different garden soils with diverse sources of contamination and physico-chemical characteristics. Chemically extractable metal(loid)s were analyzed using 0.05 M EDTA extraction and 1 M NH4NO3 extraction. In one soil sample, potting soil showedsignificant potential to reduce the availability of As, as analyzed by both extractants. This amendment also effectively reduced the Pb extractability in the geogenic-contaminated soil, as did other high-organic matter amendments such as various application rates of composts. Zeolite and zeolite-compost mixes demonstrated success on various metal(loid)s and therefore could be a promising emerging amendment mix. Other efficient amendments include crushed horn, which effectively reduced available Zn in all soils, as well as available Pb. The application of bone meal similarly reduced the extractable As, Pb, and Zn in various soils. The two applications of limes were effective against Cd, As, Pb, and Zn in the different soils studied. This study provided evidence that it is possible to reduce the extractability and thus the environmental availability of the metal(loid)s applied with available and affordable amendments. The results depended on the physico-chemicalsoil parameters and metal(loid)s considered. There is no single solution, which implies that tests must be carried out before any implementation activities on the kitchen gardens