LAUSR

Abstract Oxygen ( 16 O, 17 O and 18 O) and sulfur ( 32 S, 33 S, 34 S and 36 S) isotope ratios of and major ion (Na + , Ca 2 + , Cl − , NO 3 − and SO 4 2 − ) concentrations in lakes, ponds and creeks from Deception Island, Antarctic Peninsula were analyzed to study the sources of sulfate, its oxidation, and the surficial processes of the dissolved sulfate. The positive relationship between the δ 34 S sulfate (8.1‰ to 17.3‰) and the Cl − /SO 4 2 − molar ratio suggests mixing of sulfate from atmospheric deposition and from oxidation of sulfide minerals. The average sea salt fraction (28%) and δ 34 S nss values (from 5.6‰ to 15.9‰) indicate that a combination of sea salt and marine biogenic sulfide provide the high δ 34 S end-member of the dissolved sulfates. The relatively low δ 18 O sulfate (from − 4.6‰ to 0.7‰) of Deception Island water suggests a role of local water in the formation of sulfate. Slightly negative but mass-dependent Δ 17 O sulfate values imply that atmospheric oxidation by O 3 and H 2 O 2 are negligible, while these values might suggest a significant role of oxidation by molecular oxygen and OH. The distinctly low δ 34 S sulfate value of two samples (DCW-2 and DCW-3) suggests the input of sulfate from sulfide oxidation. Slight elevation of δ 34 S sulfate values up to 17.3‰ compared to a typical atmospheric value indicates a minimal role for dissimilatory microbial sulfate reduction of Deception Island water and sediments. Both Δ 33 S sulfate and Δ 36 S sulfate values are homogeneous and near zero, implying that the dominant atmospheric oxidation process is tropospheric and that there are minimal to no contributions of stratospheric sulfate to Deception Island water.