Zbiorniki zaporowe jako źródło emisji gazów cieplarnianych

Obserwowane w ostatnich latach globalne ocieplenie klimatu stymuluje badania dotyczące emisji gazów szklarniowych do atmosfery zarówno ze środowisk wodnych, jak i lądowych. Za główną przyczynę efektu cieplarnianego uważa się nadmierną emisję CO2 i CH4 . Nie ma wątpliwości, że oceany pełnią kluczową rolę w globalnej wymianie gazów, ale istnieją też mocne dowody, że wody śródlądowe (zwłaszcza zbiorniki zaporowe) mogą odgrywać nieproporcjonalną do swej wielkości rolę w globalnej dynamice gazów szklarniowych. Zachodzące w zbiornikach zaporowych procesy rozkładu materii organicznej są bowiem źródłem emisji dwóch głównych gazów szklarniowych: metanu i ditlenku węgla. Oszacowano, że ok. 7% gazów szklarniowych emitowanych ze źródeł antropogenicznych stanowią gazy węglowe emitowane ze zbiorników zaporowych. W pracy zebrano informacje dotyczące emisji węglowych gazów szklarniowych ze zbiorników zaporowych w różnych strefach klimatycznych. Opisano mechanizmy tworzenia, ścieżki transportu oraz główne przemiany tych gazów w ekosystemach słodkowodnych.

In aspect of global warming, scientists conducting intensive research on greenhouse gas emissions into the atmosphere from both aquatic and terrestrial environments. Excessive emissions of CO2 and CH4 are considered as the main cause of the greenhouse effect. There is no doubt that the oceans play a key role in the global exchange of gases, but there are also strong evidences that inland waters (particularly reservoirs) may play a disproportionate to their size role in the global dynamic of greenhouse gases. During the impoundment dam reservoir a certain area of land covered with vegetation is flooded, and in existing reservoir, organic matter is produced in the process of primary production and delivered from the catchment. The collected organic material dies, shall be deposited in the bottom sediments, where it is decomposed by bacteria. Depending on the oxygen conditions, CO2 or CO2 and CH4 are the end product of decomposition. Because during transport of gases to the interface water - atmosphere they are transformed microbiologically, the amount of greenhouse gases released from the sediment is not equal to the size of the emitted into the atmosphere. It was estimated that approximately 7% of greenhouse gas carbon emissions from anthropogenic sources are the gases emitted from reservoirs. The most information in the literature on greenhouse gas emissions from reservoirs, concerns reservoirs which are located in tropical and boreal climatic zone. The few reports on the temperate zone. The results show that both CO2 and CH4 emissions from boreal reservoirs are small compared to the ones in the tropics. This is certainly due to the water temperature. Besides the huge difference of emissions in different climate zones also between reservoirs in the same climatic zone the differences in the greenhouse gas emissions can be significant. This indicates that there are other factors that significantly regulate greenhouse gas emissions from reservoirs into the atmosphere. These are: the content and type of organic matter deposited in the bottom sediments and the reservoir age. Hydroelectric reservoirs have long been considered as "clean" energy source. However, some scientists prove that hydropower is a significant contributor to greenhouse gas emissions and is not "climate-friendly". The results of calculations indicate that the impact of a modern gas plant on the warming is greater than high-emission boreal reservoir, but the tropical reservoir can have tens of times greater impact on the global warming than the gas plant. In this work the information about the carbon greenhouse gases emissions from reservoirs in different climatic zones is collected. The mechanisms of the formation, transport pathways and main transformation of these gases in freshwater ecosystems were described.