Potentially harmful elements in terraced agroecosystems of NE Italy: Geogenic vs anthropogenic enrichment

One of the most important man-induced land transformations since many centuries is the terraced landform, an agricultural technique that characterizes many agroecosystems all over the world. In this study, our objectives were: i) to evaluate the background level of heavy metals in soils of a terraced ecosystem in the proximity of the Dolomites Natural Park, in northern Italy; ii) to ascertain the metal concentration range and spatial distribution; iii) to identify possible contamination of some sites, and the related environmental hazard. Six different terraced landforms were selected; totally, 32 representative soil profiles were opened and sampled. Specific analyses of 15 potentially harmful trace elements (Sb, As, Be, Cd, Co, Cr, Hg, Ni, Pb, Cu, Se, Sn, Tl, V and Zn) were carried out in the laboratory by ICPMS after digestion with aqua regia. Background levels of heavy metals in the soils investigated are consistent with currently recorded trace element concentrations of soils from Western Europe. A geological matrix effect may be accounted for metal release by parent material weathering. Nevertheless, metal accumulation in surface horizons at some sites has been recorded, and may be ascribed to atmospheric input. The extreme parts of the territory investigated, moreover, present significant concentrations of some metals. In particular, Cu, Pb and Zn contents in surface horizons suggest an anthropogenic enrichment. The human contribution could be due to past mine activities in the close vicinity, and metals have been probably vehicled southward through stream and/or wind transport. Moreover, Sn shows amounts overall above the allowed legislation threshold. In some cases it was not possible to assess if the presence, or the concentration level, of a metal could be related to natural sources or to recent, or past, human activities. (C) 2014 Elsevier B. V. All rights reserved.