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High methane emissions from a midlatitude reservoir draining an agricultural watershed
Citation:
Beaulieu, J., R. Smolenski, C. Nietch, A. Townsend-Small, AND M. Elovitz. High methane emissions from a midlatitude reservoir draining an agricultural watershed. ENVIRONMENTAL SCIENCE & TECHNOLOGY. ACS Publications, Washington, DC, 48(19):11100-11108, (2014).
Impact/Purpose:
To inform the public.
Description:
To assess the magnitude of methane (CH4) emissions from reservoirs in mid-latitude agricultural regions, we measured CH4 and carbon dioxide (CO2) emission rates from William H. Harsha Lake, an agricultural impacted reservoir located in southwestern Ohio, USA, over a thirteen month period. The reservoir was a strong source of CH4¬ throughout the year, emitting on average 176 ± 36 g C m-2 d-1, comparable to tropical reservoirs. Contrary to our initial hypothesis, the largest CH4 emissions were during summer stratified conditions, not during fall turnover. The river - reservoir transition zone emitted CH4 at rates an order of magnitude higher than the rest of the reservoir, and total carbon emissions (i.e., CH4 + CO2) were also greater at the transition zone, indicating that the river delta supported greater carbon mineralization rates than elsewhere. This work indicates that mid-latitude agricultural impacted reservoirs may be a larger source of CH4 to the atmosphere than currently recognized, particularly if river deltas are consistent CH4 hot spots. We estimate that CH4 emissions from agricultural reservoirs could be a significant component of total anthropogenic CH4 emissions in the USA.
