Quantitative geomorphic analysis of asbestos dispersion and pollution from natural sources: the case-history of the Pollino National Park, southern Italy

Abstract

A multidisciplinary study has been carried out on the dispersion modalities of asbestos minerals from ophiolites outcrops in the area of the Pollino National Park (Calabria-Lucania border, southern Italy) by integrating geological and geomorphological mapping, quantitative geomorphic analysis, petrological and mineralogical analyses of outcropping crystalline-metamorphic rocks, aerosol analyses, and remote sensing investigations. Large amount of asbestos minerals have been recognized in the ophiolitic suites outcropping at the Calabria-Lucania border. Specifically, tremolite-actinolite and chrysotile have been recognized in the metabasite and serpentinite samples by means of thin sections analyses and X-ray powder diffraction. Asbestos fibres have been also recognized in the aerosols sampled in the study area by SEM-EDS analysis. The spreading out of ophiolite-bearing rocks in areas far away from their outcrops by natural running water (i.e. sheet wash and fluvial processes) has been evaluated by comparing different geomorphic indexes estimated for each of the seven catchment basins of the study area (i.e. the exposure index I and the morphometric parameters Tu and D). The relevant dispersion of the asbestos minerals by running water is a consequence of the cataclastic conditions of the serpentinite outcropping at the Calabria-Lucania border, although the peculiar geomorphological characteristics of each drainage basin play a crucial role in the dispersal of these minerals even far from their outcrops. This study allowed to assess the degree of environmental hazard due to release of asbestos fibres. The comparison of natural and human factors in controlling asbestos release in areas characterized by different morphological conditions revealed that erosional (mainly fluvial) processes promoted an intense spreading of asbestos minerals, even in an area wider than the original ophiolite (mainly serpentinite) outcrops.