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Anthropogenic activities, dominated by emissions of sulfur dioxide (SO2), have perturbed the global sulfur (S) cycle. Uncertainties in timescales of S transport and chemistry in the atmosphere lead to uncertainties in the predicted impact of S emissions. Measurements of cosmogenic 35S may potentially be used to resolve existing uncertainties in the photochemical and chemical transformation of S in the environment. The lack of a simple, effective, and highly sensitive technique to measure 35S activity in samples with low activities may explain the scarcity of published measurements. We present a set of new sample handling and measurement procedures optimized for the measurement of 35S in natural samples with activities as low as 0.20 dpm above background (2σ integration time = 2 hr). We also report simultaneous measurements of aerosol (35SO4) and gas phase (35SO2) collected at inland and coastal locations; the range of observed activities corresponds to SO2 residence lifetimes of 0.2 ± 0.04 (coastal) 22.3 d± 0.04 (inland). These optimized techniques offer the potential for resolving atmospheric processes that occur on 6-12-hour timescales as well as resolving transport phenomena such as stratospheric mixing into the troposphere. [ABSTRACT FROM AUTHOR]