Environmental assessment of mining industry solid pollution in the mercurial district of Azzaba, northeast Algeria

To date, there have been few detailed studies regarding the impact of mining and metallogenic activities on solid fractions in the Azzaba mercurial district (northeast Algeria) despite its importance and global similarity with large Hg mines. To assess the degree, distribution, and sources of pollution, a physical inventory of apparent pollution was developed, and several samples of mining waste, process waste, sediment, and soil were collected on regional and local scales to determine the concentration of Hg and other metals according to their existing mineralogical association. Several physico-chemical parameters that are known to influence the pollution distribution are realized. The extremely high concentrations of all metals exceed all norms and predominantly characterize the metallurgic and mining areas; the metal concentrations significantly decrease at significant low distances from these sources. The geo-accumulation index, which is the most realistic assessment method, demonstrates that soils and sediments near waste dumps and abandoned Hg mines are extremely polluted by all analyzed metals. The pollution by these metals decreases significantly with distance, which indicates a limited dispersion. The results of a clustering analysis and an integrated pollution index suggest that waste dumps, which are composed of calcine and condensation wastes, are the main source of pollution. Correlations and principal component analysis reveal the important role of hosting carbonate rocks in limiting pollution and differentiating calcine wastes from condensation waste, which has an extremely high Hg concentration (˃1 %).