Abstract. Diffusion in sulfuric acid plays a role in heterogeneous stratospheric processes. Knowledge of diffusion coefficients is required to determine the partitioning of heterogeneous reactions between the bulk and the surface of sulfate aerosol particles. Diffusion coefficients are also needed to analyze time-dependent uptake data to obtain solubilities. In order to provide quantitatively accurate diffusion coefficients, the experimental challenges of measuring solute diffusion in strong electrolyte environments must be overcome. We use a modified diaphragm cell technique and report diffusion coefficients for HC1 and HBr in sulfuric acid solutions from 220 to 300 K. We find that the temperature and viscosity dependence of these measurements follows the equation D = cT/rl, where rl is viscosity, yielding c = 7.8 x 10-8 cm2 cP/s K for HC1 and c = 7.9 x 10-8 cm2 cP/s K for HBr. An empirical equation for predicting diffusion coefficients for other species in sulfuric acid is also presented.

Permafrost degradation is delivering bioavailable dissolved organic matter (DOM) and inorganic nutrients to surface water networks. While these permafrost subsidies represent a small portion of total fluvial DOM and nutrient fluxes, they could influence food webs and net ecosystem carbon balance via priming or nutrient effects that destabilize background DOM. We investigated how addition of biolabile carbon (acetate) and inorganic nutrients (nitrogen and phosphorus) affected DOM decomposition with 28‐day incubations. We incubated late‐summer stream water from 23 locations nested in seven northern or high‐altitude regions in Asia, Europe, and North America. DOM loss ranged from 3% to 52%, showing a variety of longitudinal patterns within stream networks. DOM optical properties varied widely, but DOM showed compositional similarity based on Fourier transform ion cyclotron resonance mass spectrometry (FT‐ICR MS) analysis. Addition of acetate and nutrients decreased bulk DOM mineralization (i.e., negative priming), with more negative effects on biodegradable DOM but neutral or positive effects on stable DOM. Unexpectedly, acetate and nutrients triggered breakdown of colored DOM (CDOM), with median decreases of 1.6% in the control and 22% in the amended treatment. Additionally, the uptake of added acetate was strongly limited by nutrient availability across sites. These findings suggest that biolabile DOM and nutrients released from degrading permafrost may decrease background DOM mineralization but alter stoichiometry and light conditions in receiving waterbodies. We conclude that priming and nutrient effects are coupled in northern aquatic ecosystems and that quantifying two‐way interactions between DOM properties and environmental conditions could resolve conflicting observations about the drivers of DOM in permafrost zone waterways.

Abstract. The solubility of acetone in low-temperature sulfuric acid solutions was studied in a low-pressure Knudsen cell reactor. The time dependence of the uptake coefficient was analyzed to give effective Henry's law coefficients for acetone in 48 -68 wt % sulfuric acid solutions between 210 and 240 K. The measured solubilities suggest that very little acetone will be partitioned into sulfate aerosol particles in the upper troposphere. Addition of ammonium sulfate to the sulfuric acid reduced the solubility slightly. No evidence was observed for reaction of dissolved acetone with itself or with nitric acid under the conditions of these experiments.

Connections among soil, ground, and surface water chemistries characterize nitrogen loss from an agricultural landscape in the upper Missouri River basin."

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