Using indicator kriging for the evaluation of arsenic potential contamination in an abandoned mining area (Portugal) I.M.H.R. Antunes ⁎, M.T.D. Albuquerque CVRM-Geossystems Centre, ISTUL, Lisbon and Polytechnic Institute of Castelo Branco, 6001-909 Castelo Branco, Portugal HIGHLIGHTS ► Arsenic is associated with sulfide mineralization and is toxic in the environment at low levels. ► Intrinsic and specific vulnerabilities quantify anthropogenic activities. ► Arsenic anomalies are mainly associated with the water drainage from abandoned mining activities. ► The waters are not fit for human consumption. abstract article info Article history: Received 10 August 2012 Received in revised form 1 October 2012 Accepted 1 October 2012 Available online 5 December 2012 Keywords: Sulfide mines Arsenic Waters Contamination Indicator kriging Segura Mining and mineral-processing activities can modify the environment in a variety of ways. Sulfide mineralization is notorious for producing waters with high metal contents. Arsenic is commonly associated with sulfide miner- alization and is considered to be toxic in the environment at low levels. The studied abandoned mining area is located in central Portugal and the resulting tailings and rejected materials were deposited and exposed to the air and water for the last 50 years. Sixteen water sample-points were collected. One of these was collected outside the mining influence, with the aim of obtaining a reference background. The risk assessment, concerning the proximity to abandoned mineralized deposits, needs the evaluation of intrinsic and specific vulnerabilities aiming the quantification of the anthropogenic activities. In this study, two indicator variables were constructed. The first one (I 1 ), a specific vulnerability, considers the arsenic water supply standard value (0.05 mg/L), and the probability of it being exceeded is dependent on the geologic and hydrological characteristics of the studied area and also on the anthropogenic activities. The second one (I 2 ), an intrinsic vulnerability, considers arsenic background limit as cut-off value, and depends only on the geologic and hydro-geological characteristics of the studied area. At Segura, the arsenic water content found during December 2006 (1.190 mg/L) was higher than the arsenic water content detected in October 2006 (0.636 mg/L) which could be associated to the arsenic released from Fe oxy-hydroxide. At Segura abandoned mining area, the iso-probability maps of October 2006 and December 2006, show strong anomalies associated with the water drainage from abandoned mining activities. Near the village, the probability of exceeding the arsenic background value is high but lower than the probability of exceeding the arsenic water supply value. The arsenic anomalies indicate a high probability for water arsenic contamination and those waters should not be used for human consumption. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Portuguese polymetallic mining activities were very important for the economy and were actively developed until the early 1970s. Since then, metal production has declined and most of the mines are now closed and/or have been abandoned. Mining activities extract and process valu- able pit materials, which have large surfaces and are very susceptible to both erosion and chemical weathering, causing a potential danger to the environment. The abandoned mining sites are frequently located close to occupied rural areas (Allen et al., 1996) and some of the waters are used for agriculture or human consumption without any assessment of environmental and human health risks (e.g., Antunes et al., 2002; Abreu et al., 2008; Carvalho et al., 2009; Gomes et al., 2010). In general, high concentrations of metals and metalloids in tailings are due to sulfide oxidation and the subsequent redistribution of trace metals and metalloids by secondary Fe precipitates and phase for- mation, as well as adsorption on clay fraction (Carlsson et al., 2002; Heikkinen and Räisänen, 2009). Elevated arsenic levels in surface waters are commonly associated with sulfide mineralizations (e.g., Antunes et al., 2002; Lee et al., 2007; Carvalho et al., 2009) and are considered to be toxic in the environment at low levels. In addition, arsenic Science of the Total Environment 442 (2013) 545–552 ⁎ Corresponding author. Tel.: +351 272339900; fax: +351 272339901. E-mail address: imantunes@ipcb.pt (I.M.H.R. Antunes). 0048-9697/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.scitotenv.2012.10.010 Contents lists available at SciVerse ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv