Physico-chemical characterisation of atmospheric aerosols in a rural area affected by the aznalcollar toxic spill, south-west Spain during the soil reclamation activities

Abstract

High levels of atmospheric contamination due to the re-suspension of pyrite particles from the mining waste slurry were recorded in the Guadiamar valley (the Guadiamar is a tributary of the Guadalquivir river) after the toxic spill of Aznalcóllar, north of the Doñana Natural Park (SW Spain). Major high-particulate events occurred during the extraction of the pyrite-rich mud layer, which covered an extensive area of the valley downstream of the confluence of the Agrio and Guadiamar rivers. This study deals with the monitoring of the ambient air quality at two stations near the village of Aznalcázar in the central part of the flooded area. Although the Spanish legal limit for atmospheric particles and lead in environmental air were not exceeded, high daily levels of total suspended particles (TSP) and of some elements with an environmental significance (As, Cd, Cu, Mn, Ni, Pb, Sn, Tl and Zn) were recorded at Aznalcázar and in the Guadiamar valley during soil reclamation (July–August 1998). Despite a progressive decrease in TSP levels through September–October 1998, background was higher than the levels for the May–June period. Evolution of levels for most of the elements studied showed a similar trend. The exceptions were copper, which was partially increased by other emission sources such as fumigation activities, and sodium, which remained at relatively constant levels during the study period because of its marine origin. The physico-chemical characterisation of the atmospheric particulates allowed us to determine the major grain size modes of the pyrite related elements and the solubility of the potentially toxic elements, and to identify the major particulate types present in the atmosphere in the area. Secondary and tertiary aromatic amines (i.e. alkyldiphenylamines and phenylcarbazoles, respectively) were identified in the suspended particles and in the vapour phase collected at the same station as the TSP samples. As some of these aromatic amines had been previously identified in the pyrite sludge, it is assumed that fine sludge particles containing aromatic amines were re-suspended in the atmosphere. The highest concentrations of aromatic amines in the particulate phase were recorded in August 1998 during the pyrite slurry extraction in the proximity of the Aznalcazár sampling site. Despite a sharp drop in the suspended particles of the aromatic amine concentrations, a significant concentration was detected in the vapour phase (<1.2 mm) during autumn, probably because of longer residence time in the atmosphere. Although health hazards associated with the presence of these aromatic amines are unknown, their acute toxicity exceeded that of urban aerosols.