Metal(loid) enriched topsoils in a multiple land-use area in Tuscany (Italy): geogenic vs. anthropogenic contributions and associated health risk

The Piana di Scarlino is a partially refilled wetland in the SW of Tuscany (Central Italy) which has hosted chemical and power plants since the 1960s. Presently, in the area there are urban settlements (the main urban center, Follonica, has a population of approx. 25.000), farms, tourist facilities, and industrial districts, mainly based on H2SO4 and TiO2 production as well as waste incineration. In the last two decades the soil and groundwater of the Piana di Scarlino, have been found polluted with arsenic (As) and heavy metals. This prompted local authorities to implement remediation measures and environmental monitoring programs to protect the resident population and the local agricultural produce. In 2013, we initiated an environmental surveillance program in the area within an IPPC permitting procedure for monitoring As and heavy metals and assessing human health implications. The study initially aimed at establishing topsoil data to be used as baseline for long-term monitoring. Overall total As concentration of superficial soils (0-5 cm), collected from 44 sampling sites randomly selected within a circular area up to 1.5 km around the industrial district, was on average 33.8 ± 35.9 µg/g. This value, is approximately 3 times higher than the European baseline and highlights a general enrichment of topsoil As content. This is mainly attributable to widespread geochemical anomalies characterizing Southern Tuscany and to the historical mineral processing and smelting activities carried out in the Scarlino area until the mid-90s. The highest As concentrations were found in soils from sampling sites in the proximity of a pyrite ash dump, where concentrations over 200 µg/g were reached. Average concentrations (32.9 µg/g) from agricultural and grazing soils were also much higher than the baseline for Italian agricultural lands (7.56 µg/g). Although soils from urban sites generally showed the lowest As concentrations, average As concentrations for the urban area (21.8 µg/g) remained over the screening values (20 µg/g) for contaminated soils set by the Italian regulatory framework for residential areas. In this context, we used multi-element analysis supported by techniques for monitoring atmospheric depositions to improve estimation of exposure and related health risks arising from the nearby industrial activities as well as to assess the relative contribution of historical and present-day As sources in the Scarlino area.