Levels and chemistry of atmospheric particulates induced by a spill of heavy metal mining wastes in the Doñana area, Southwest Spain

Abstract

As a result of the collapse of the storage lake dam (property of the Boliden company), pyrite-rich mud layer covered the Guadiamar valley (north of the Doñana Natural Park, SW Spain). The present work focuses on the physico-chemical characterisation of suspended particles during high atmospheric particulate events caused by soil reclamation activities. Intensive sampling of atmospheric particulates during the period 20 May–27 December was carried out at two monitoring stations located at Aznalcázar and in the Guadiamar valley. At Aznalcázar mean daily levels of 191.2 μgTSP m −3 were recorded for the soil reclamation period (July–August 1998), with maximum daily levels of 490 μgTSP m −3. After the reclamation activities TSP progressively decreased down to levels of 90 μgTSP m −3 in September–October, and 40 μgTSP m −3 in November–December. Very high levels of major and trace elements were recorded at the two sampling sites. As for TSP, ambient air levels of major and trace elements increased sharply (two orders of magnitude) in July and August compare with the levels recorded in May and June, and gradually decreased during the autumn and winter seasons. Mean daily levels for July and August at Aznalcázar attained values close to 2 ng m −3 for Ag, Cd, Sn and Tl, 10 ng m −3 for Ni, 100 ng m −3 for Mn, 200 ng m −3 for As and Cu, and 450 ng m −3 for Pb and Zn. In the Guadiamar valley (where the major soil reclamation activities were carried out), the levels achieved were higher than those of Aznalcázar by a factor of 3. In September, the levels recorded at both monitoring stations decreased but were still higher than the initial values by a factor of 5, showing lower standard deviations than those in July–August. Finally, the levels recorded in December were very similar to those of May. As regards the grain-size distribution of minor and trace elements, Cu, Mn and Zn exhibit from 17 to 36% and 59 to 70% of their bulk levels in TSP in the PM2.5 and PM10 fractions, respectively. However, As, Cd, Co, Pb, Sb Se and Tl showed proportions from 20 to 48% and from 80 to 90% TSP in the PM2.5 and PM10 fractions, respectively. The water extractable fraction of major, minor and trace elements in TSP was different for the elements studied. Thus, Cd, Co, Tl, Mn and Se showed a water extractable proportion from 27 to 92% of their bulk content in TSP, Ni, As, Zn and Cu showed an intermediate soluble fraction which ranged from 8 to 10%, and Pb, Sb and Cr were mobile in a proportion <4%.