On the arsenic source mobilisation and its natural enrichment in the sediments of a high mountain cirque in the Pyrenees

Abstract

Recently arsenic contamination and its environmental and human health problems have been raising concerns worldwide. The occurrence of natural high levels of arsenic contamination has generally been reported for low altitude environments. Here we report a study conducted to assess the extent of arsenic mobilisation/transportation from previously identified arsenic source areas in a high altitude cirque of the Pyrenees as well as the potential contribution of As by snow. The concentration of arsenic in sediments of several tributaries was enriched up to about ten folds due to mobilisation of arsenic from the source areas within the catchment. The highest arsenic enrichments were found in an area dominated by quartzite and slate formation in the southern side of the basin, and it generally diminished towards the major lake downstream, possible due to mixing with sediments from non-source areas. At these sites arsenic exceeded the hazard quotient (HQ) limits for the protection of aquatic life. The potential hazard of the As-enriched sediments may be further enhanced outside the catchment as samples collected downstream the cirque have also shown arsenic concentration exceeding HQ unity. The arsenic concentrations in the water collected at a number of sites exceeded its guide value for the protection of aquatic life. The potential As contribution by snow in the area was low and was largely of lithospheric origin. The PCA analysis showed strong association of arsenic in sediments with the sediment mineralogical composition (Fe2O3, TiO2 and Mn). Arsenic in water was positively correlated with its concentration in the sediments and could potentially increase if the environmental/climate conditions change.

Climate change enhances the mobilisation of naturally occurring metals in high altitude environments

“…shale, schist) are potential geological source of As and other metals. Geogenic inputs of TEs have been reported in the waters and sediments of this zone, particularly in the east side (Garrido, 2002;Zaharescu et al, 2009b) (Figure 1). …”

“…It also corresponded to the sedimentation laminae along the profile, likely produced during spring thaw, which implies sediments were not disturbed by mixing. Furthermore, sediment metal content from the present study was compared to surface sediment data collected throughout the catchment (Zaharescu et al, 2009a andZaharescu et al, 2009b). Climate data were provided by the Spanish National Institute of Meteorology, Madrid (INM) and covered the period 1972-2005. 2.4 Particle size distribution.…”

Riparian ecosystem in the alpine connectome. Terrestrial-aquatic and terrestrial-terrestrial interactions in high elevation lakes

“…the legumes, since mycorrhizal colonisation has been related with Pb plant uptake under low soil metal concentrations (Wong et al, 2007). Or, plant's naturally high sensitivity to Pb (Kabata-Pendias and Pendias, 2001) could also have determined changes in vegetation composition along a natural Pb stress gradient, particularly in metamorphic areas where Pb is at higher bedrock concentrations, as reported for the central Pyrenees (Catalan et al, 2006;Zaharescu et al, 2009).…”

“…To test for relationships between lake chemistry and riparian vegetation composition, < 2cm depth littoral sediments and water ± 5m off the littoral (for small waterbodies, the distance was less) were sampled using standard protocols employed in Zaharescu et al (2009). The sediments comprised fragmented rocks, coarse sands, and fine materials.…”

“…Lake and riparian sediments at high elevations are generally dominated by catchment bedrock denudation products, and autochthonous organic matter fixation (Zaharescu et al, 2009 and2016a). Results of the MFSO of riparian vegetation composition against sediment nutrients, major and trace elements contents resulted in a bi-dimensional solution, with Mg and Pb able to reliably predict the vegetation composition (cumulative r =0.74; Table 3 and Fig.…”