This study presents the changes in dissolved sulfate concentration and isotope composition of Icelandic river waters between the peak of SO2 emissions in the United States and Europe and the present. Chloride concentration in Icelandic rivers has not changed much since 1972. The overall average change from 1972−1973 to 1996−2004 was −3%, indicating insignificant sea-salt contribution changes. More than 99% of the river-dissolved sulfur was in the form of sulfate. There are three main sources for dissolved sulfate in the rivers: rocks, sea-salts, and anthropogenic. Total dissolved sulfate, tdSO42-, and non-sea-salt sulfate, nssSO42-, decreased in all of the rivers from the early 1970s to 1996−2004. The percentage decrease varies from 13% to 65%. The decrease is smallest in rivers were there is considerable rock-derived dissolved SO42-. The overall average decrease was 39% for tdSO42- and 46% for nssSO42-. The anthropogenic sulfate fraction has declined making most of the river waters δ34S values of sulfate higher through time. The overall decline in river sulfate and increase in δ34S, while SO2 emissions from Iceland has been increasing, demonstrates the response of river chemistry in the remote North Atlantic to the decline in man-made emissions of SO2 in North America and Europe.
Carbon isotopic oscillations are useful to elucidate the stratigraphy and biogeochemical events around the Precambrian–Cambrian transition. New isotopic data from the Manykaj and Emyaksin formations of the eastern Anabar Uplift (Siberia) help to correlate the Lower Cambrian and Neoproterozoic–Cambrian transitional beds across the Siberian Platform. The similarity of trends and amplitudes of the carbon isotopic curves, together with biostratigraphic and sequence-stratigraphic markers from the Anabar Uplift, provide a precise correlation with the southern part of the Siberian Platform. Diagenesis of argillaceous limestones of the Emyaksin Formation has apparently not affected the primary isotopic variations. The resulting curve is nearly identical in sections about 100 km apart in the Tommotian–Atdabanian portion of the formation. Relatively frequent and pronounced isotopic oscillations in the lower beds of the Emyaksin Formation fit between features I and II of the southern Siberian isotopic reference scale but are undetected therein owing to the depositional hiatus at the base of the Tommotian Stage in its type section. This confirms the transgressive onlap from the north suggested by previous studies, and makes the appearance of the Cambrian skeletal fossils on the Siberian Platform less abrupt. The hiatus in the south appears to embrace at least two biostratigraphic zones as recognized in the north. The case is strengthened for a pre-Tommotian Cambrian Stage in Siberia, the biostratigraphic framework for which has been elaborated earlier.
Sulfate deposited onto the Antarctic ice sheet originates from a mixture of sulfur sources. Two 100 m long ice cores from Dronning Maud Land have been studied by means of sulfur isotopic analysis and detailed ion analysis to reveal temporal and spatial differences in the influencing sulfur source. The two ice cores represent the coastal area and the polar plateau, respectively. The isotopic signals were similar within each ice core, indicating no temporal change of influencing sources during the last 1100 yr. The mean values at the two different sites were also similar: 14.6 ± 0.3% and 14.7 ± 0.3‰, respectively.The similarity remains between calculated non-sea-salt values when a sulfate-depleted sea-salt aerosol is assumed in the costal core. When the influence of sporadic explosive volcanic eruptions is subtracted from the signal, the isotopic value from the polar plateau(15.4 ± 0.6‰) is significantly lower than prescribed values for marine biogenic sulfur. This suggests that one or more additional sources contribute to the sulfate budget. Several possible contributors are discussed in the context of former sulfur isotopic signals presented from Antarctica.
