Abstract
The purpose of this study was to assess the negative impact on soil caused by several mining episodes that occurred at Marrancos mine, an old gold/silver mine. The main aims were to: (i) assess the quality of the soil and the delineation of areas potentially contaminated by arsenic; (ii) assess the uncertainty attached to the assignment; and (iii) present a method of stochastic simulation (probability field simulation) as an alternative technique to predict pollutant concentrations of heavy metals, or metalloids, at unsampled locations. Indicator kriging was used to model the uncertainty attached to the concentration values at the unsampled sites and p-field simulation produced probability maps that allowed assessment of the probability that the arsenic concentrations did not exceed a regulatory threshold. The probability maps were then used to identify hazardous areas. About 90 realisations were generated for the variable, meaning 90 equiprobable scenarios for the spatial distribution of arsenic. The use of a potential risk-based standard as contamination threshold shows a wide area of soils classified as hazardous for ecosystems that need further investigation to determine the urgency for remediation.
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