Characterization of Environmental Hazard Maps of Metal Contamination in Guadiamar River Margins

Abstract

This paper presents a methodology to account for uncertainties in mapping of the probability of soil contamination by different heavy metals. The methodology is based on a co-simulation technique using direct sequential simulation of a multivariate set of variables, with each variable simulated based on hard data, the heavy-metal concentrations in the soil, and on soft data, consisting of a previously simulated map of one of the heavy metals. The suggest methodology is based on the influence of the spatial distribution of the heavy-metal concentrations; and on the influence of the soft data dependent on the global correlation with the hard data. With the 10 realizations of the simulated multivariate set, a “hazard” index was calculated for each pixel of the area, based on the simultaneous proportions (joint probabilities) of different levels of all metals. Finally, the intersection of the hazard map, based on the joint dispersion of all contaminants, with the environmental impact map for the different ecosystems, resulted in environmental hazard maps of the Guadiamar river margins. The performances of the multivariate set of co-simulated variables was compared considering two extreme alternatives: i) the soil is considered in need of treatment if all 5 heavy metals simultaneously exceed their concentration limit value at the same location; ii) the soil is considered in need of treatment if at least one heavy metal exceeds its concentration limit at the same location. The proposed simulation methodology improved the delineation of potential areas simultaneously contaminated with different pollutants.