Heavy metals in soils and sedimentary deposits from Vigarano Mainarda (Ferrara, Northern Italy): characterisation and biomonitoring

This contribution investigates agricultural soils from Vigarano Mainarda in the province of Ferrara (Padanian alluvial Plain, Northern Italy), in order to provide insights into their genesis, to define the geochemical background of the area and to evaluate the existence of anthropogenic contamination. Moreover, environmental risk related to the presence of potentially toxic heavy metals that can be transferred into agricultural products (and consequently bio-accumulated in the food chain) is assessed. The analyses, reported in an extensive supplementary dataset, include XRD, XRF, and ICP-MS data carried out on bulk sediments, tests of metal extraction with aqua regia, as well as analyses of local agricultural products, i.e. biomonitoring which is important in the evaluation of the element mobility. Based on the results, GIS-based geochemical maps were produced and local backgrounds were defined. This approach demonstrated that a high concentration of Cr, Ni (Co, V) is a natural (geogenic) feature of the local alluvial terrains, which in turn is related to the origin and provenance of the sediments, as confirmed by the lack of top enrichment in all the investigated sites. Tests of metal extraction and analyses of agricultural products provide guidelines for agricultural activities, suggesting that extensive use of sewage sludge, industrial slurry and zootechnical manure (that are often rich in metals) should be minimised. The extended dataset reported in this paper shows that the agricultural terrains of the studied alluvial plain are not characterised by anthropogenic heavy metal pollution. In spite of the elevated natural background of Cr and Ni, most of the local agricultural products do not show significant evidence of bio-magnification. Exceptions are represented by forage grass (alfa alfa) and corn (maize) that tend to uptake arsenic and nickel, respectively. This demonstrates that in agricultural areas, a geochemical risk assessment must include both soil and plant investigations.