Hydrogeochemistry and chemical weathering in a periglacial environment of Maritime Antarctica

Recent pedological investigation indicated that the presence of sulfides and additions of seabird guano in Maritime Antarctica accelerates the weathering process, but chemical weathering remains little studied, underestimated and underdiagnosed in cold environments. The present work evaluates characteristics of soils and hydrogeochemical processes in Barton Peninsula, a typical periglacial environment of Maritime Antarctica. Four pedons were selected, described, sampled and classified according to the U.S. Soil Taxonomy. Soil morphological, physical and chemical properties were analyzed. Fifty eight surface water samples were collected and analyzed. Samples were filtered, acidified and analyzed (Al, Ca, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, S, Si and Zn) by ICP-OES after the appropriate treatments. We identified four different water groups: i) calcium and magnesium bicarbonate waters on non-sulfated substrates; ii) acidic sodium sulfate or magnesium calcium sulfate waters in sulfate substrates; iii) neutral alkaline waters on phosphatic substrates; iv) sodium hyperchloride alkaline waters in coastal marine areas. The hydrogeochemical composition can be predicted by lithology, landform and bird nesting density. Higher concentrations of metals in running waters indicate the process of sulfide oxidation. Our results show that seabirds activity promotes a sea-land bio-transfer of nutrients resulting in ornitheutrophication, identified by positive hydrogeochemical anomaly (high nutrients) in soils and waters. Sulfated and ornithogenic soils present deeper weathering (sulfurization and phosphatization processes), which cannot be underestimated. The assessment of hydrogeochemical background is a suitable tool for preservation of terrestrial ecosystems in this part of Antarctica.