How to manage potential groundwater contaminations by As, Fe and Mn in lower Po Plain: a proposal from the case study of Cremona

The Legislative Decree 152/06 on environmental regulations also governs polluted site remediation (Part IV). A potentially contaminated site is defined when concentrations exceed the limits reported in the Attachment 5 (Title V). Nevertheless, the Legislative Decree 152/06 considers the possibility of higher limits than Attachment 5 for trace elements in the case of natural high contents by the definition of natural background levels. The lower Po Plain is characterized by high natural concentrations of As, Fe and Mn in groundwater and, at the same time, is one of the most important areas for the Italian productive system, and thus, possible direct sources of As, Fe and Mn or indirect anthropogenic influences could also exist. Therefore, an operative tool is required to determine the natural background levels and to understand if measured high concentrations are attributable to natural backgrounds or to anthropogenic sources/influences, and consequently, to decide on the beginning of the administrative procedure requested by the Legislative Decree 152/09 through the site characterization phase. This work presents a proposal of procedure to manage potentially contaminated site by As, Fe and Mn in the lower Po Plain, that was developed in the framework of a scientific collaboration between the Province of Cremona and the University of Milano-Bicocca. The procedure involves the following four steps, preceded by the derivation of natural background levels as step zero: (1) comparing new measurements to natural background levels; (2) testing the presence of direct anthropogenic sources of As, Fe and Mn; (3) excluding false positives and (4) testing the presence of indirect anthropogenic influences on As, Fe and Mn concentrations. The operative application of the proposed procedure is actually under consideration by the Province of Cremona.