Soil Properties Affecting metal Extractability Patterns in Periurban Calcareous Agricultural Soils in the Mediterranean Area

The potential risk of metal accumulation in periurban agricultural areas is a matter for concern. The climate characteristics and carbonate content of calcareous agricultural Mediterranean soils typical in these areas favour metal accumulation at the surface level; however there is also a risk of potential metal mobility. Our study focuses on the soil properties affecting metal mobility in these soils. Metal extractability patterns were assessed in soils after they were spiked with a mixture of Cd, Cu, Pb, and Zn and incubated up to 12 months, using one-step extraction methods (NaNO3, a mixture of low molecular weight organic acids – LMWOA and diethylene triamine pentaacetic acid –DTPA–). The concentration of extractable Cd was 50% lower in the soil with the highest carbonate content. LMWOA-extractable Cu was highest in soils with the lowest organic matter (OM) content at day 1 of the incubation experiment and in soils with the lowest carbonate and recalcitrant OM contents at 12 months. Fine mineral fractions determined the lowest DTPAextractable Cu. The highest Pb retention was in soils with the highest carbonate and clay contents. However, we were unable to establish any soil component affecting Pb extractability patterns. The Zn extractability pattern was related to particle-size distribution, which was highest in soils with a low proportion of fine mineral fractions. To summarise, carbonate, particle-size distribution and OM are relevant to potential metal mobility in these soils. The high DTPA-extractable metal values are evidence of a potential risk of metal mobility in the soils in the study.