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Gas Dynamics in Eutrophic Lake Sediments Affected by Oxygen, Nitrate, and Sulfate

Department of Environmental Sciences, Univ. of Kuopio, Research and Development Unit of Environmental Health, P.O. Box 1627, FIN-70211 Kuopio, Finland

View larger version (32K): [in a new window]   Fig. 1. The continuous water flow system (A–H) with a gas and water tight lid (I–O). Components: reservoir (A), sampling outlet for reservoir water (B), peristaltic pump (C), sediment core (D), bottom cap (E), outflow to drain (F), water sampling with a syringe (G), water sampling with a flask (H), inflow (I), gas trap (J), outflow (K), magnetic stirrer (L), rotating magnet (M), port for electrodes (N), removable clamp (O).

View larger version (36K): [in a new window]   Fig. 2. Redox potential profiles in the deep profundal sediments with (a) the anoxic flow containing SO2-4, (b) the oxic flow containing SO2-4, and in the shallow profundal sediments with (c) the anoxic flow containing SO2-4, (d) the anoxic flow containing NO-3, and (e) the oxic flow containing NO-3.

View larger version (27K): [in a new window]   Fig. 3. Gas fluxes (sum of diffusion and ebullition) from the sediments. (a) CH4 from the deep profundal, (b) CH4 from the shallow profundal, (c) CO2 from the deep profundal, (d) CO2 from the shallow profundal, (e) N2O from the deep profundal, and (f) N2O from the shallow profundal sediments. The averages and standard error of the means are shown. Asterisks denote that increase in NO-3 or SO2-4 concentration affects gas fluxes in a statistically significant manner (***, P < 0.001).

View larger version (26K): [in a new window]   Fig. 4. Fluxes of (a) SO2-4 from the deep profundal, (b) SO2-4 from the shallow profundal, (c) NO-2 + NO-3 from the deep profundal, (d) NO-2 + NO-3 from the shallow profundal, (e) NH+4 from the deep profundal, and (f) NH+4 from the shallow profundal sediments. The averages and standard error of the means are shown.

View larger version (47K): [in a new window]   Fig. 5. Methane production potential (MPP) in the deep profundal sediments (a) after oxic SO2-4 and (b) after anoxic SO2-4 treatments, and in the shallow profundal sediments (c) after anoxic SO2-4 and (d) after oxic NO-3 treatments. The averages and standard error of the means are shown. Statistical differences between the treatments in each layers are marked with a, b, and c (Tukey-B post hoc test).

View larger version (32K): [in a new window]   Fig. 6. Sulfur content in the sediments treated with SO2-4.