Processes affecting molecular and stable isotope compositions of sediment gas in estuarine waters along the southern Baltic coast (Poland)

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• 作者：Michał Woszczyk ; Maciej J. Kotarba ; Michael Whiticar ; Carsten Schubert
• 关键词：Greenhouse gas ; Coastal lake ; Biogeochemistry ; Stable isotopes ; Baltic
• 刊名：Biogeochemistry
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：131
• 期：1-2
• 页码：203-228
• 全文大小：2204KB
• 刊物类别：Earth and Environmental Science
• 刊物主题：Biogeosciences; Ecosystems; Environmental Chemistry; Life Sciences, general;
• 出版者：Springer International Publishing
• ISSN：1573-515X
• 卷排序：131

文摘

This paper investigates the molecular and stable isotope compositions of sediment gases from seven coastal lakes along the southern Baltic coast in Poland. The aim is to extend the knowledge of the genesis and distribution of microbial gases in the zone of mixing of fresh and salt waters with special attention to the effect of salinity, climate-related seasonality, and vertical sediment mixing. We found differences in the compositions of gas between the studied lakes and within each lake. These differences are mainly controlled by lake water depth and the presence of macrophytes. Due to the dissolution of rising bubbles in highly oxygenated water, the concentrations of CH₄ and CO₂ show up to 67% decline along the water column in favor of N₂ and O₂. On the other hand, in vegetated parts of the lakes, the CH₄ is depleted in favor of CO₂, and the residual CH₄ and CO₂ are enriched in 13C. Despite the fact that the coastal lakes display highly oxidizing conditions in the water column and that the bottom sediments are mixed by wind waves the CH₄ reveals rather low oxidation. On the basis of the CH₄/N₂ ratio we established that there are differences in the intensity of ebullition throughout the lakes. Higher intensities of ebullition were found in shallower parts of the lakes. Salinity has no effect on the stable C and H isotope composition of sediment gas. It seems, however, that salinity affects the molecular composition of hydrocarbons via preferential oxidation of CH₄ under higher salinity conditions.