A Preliminary Zonation to Support the Remediation and the Risk Assessment of an Area Contaminated by Potentially Toxic Elements in Murcia Region (SE, Spain)

Abstract

The objective of this work was to evaluate processes affecting soil samples in Portman Bay in order to establish a preliminary zonation of the affected area. For this aim, a complete physical, chemical and mineralogical characterization of sediments, both in surface and at depth was carried out. Portman bay is situated close to the mining region of La Unión., located in the province of Murcia, south-eastern Spain. The entire area around the bay was subject to mining from the time of the Roman Empire to 1991. Since 1957, the wastes from mining operations were discharged directly into the sea in the inner part of the bay, while later on, they were also discharged to sea at a distance of the shore. These wastes mainly consisted in ore materials (galena, pyrite and sphalerite), phyllosilicates, in addition to siderite, iron oxides and sometimes alteration products such as jarosite, alunite, kaolinite and greenalite. Mining activities have produced great amounts of wastes, characterized by high trace elements content, acidic pH and minerals from weathering processes.The results of the applied characterization allowed a preliminary zoning of the risk in the area to be established, and this was the starting point to outline the remediation project.