J1.3 Greenhouse gas emissions from a subtropical cultural-eutrophic lake

Tuesday, 29 April 2008: 9:05 AM
Tangerine A (Wyndham Orlando Resort)
J. Hoyos-Santillan, Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional (Cinvestav), Mexico, Mexico; and A. Sepulveda, F. J. Gutierrez-Mendieta, M. R. Torres-Alvarado, E. Razo-Flores, L. Dendooven, and F. Thalasso

During the past decade the global warming has taken a central role in scientific community, either as a growing research topic or as debate node. Recent studies have shown that freshwater environments contribute significantly to the increase of atmospheric CO2 and CH4 concentrations; the N2O emission contribution still unknown. Most of the research focuses on boreal ecosystems but little is known about tropical or subtropical ones. The aim of our research was to evaluate greenhouse gas emissions from a subtropical eutrophicated lake. The model system chosen was a lake located in an urban area with clear pollution evidences (Lake of Guadalupe, State of Mexico, Mexico). CH4 and N2O fluxes were quantified through the static chamber technique. Additionally, trophic state and pollution indicators were monitored for two years. The lake, of 16 m maximum depth, was characterized by yearly average temperature of 16.5 ± 1.43 ºC and by anoxic conditions below 2.5 m. Total organic carbon was: 42.73 ± 5.7 mg/l; total nitrogen: 6.6 ± 0.8 mg/l; sulphate: 23.0 ± 0.15 mg/l and total coliforms 239 103 MPN/100 ml. The trophic state index (TSI) estimated from 3 parameters was 80 and 91 during the rainy and the dry season respectively; this values classify the lake as hypereutrophic. The average CH4 and N2O emissions were 124.0 and 3.1 mg/m2.d, respectively. These results are discussed with emphasis on the biological process involved. A global carbon and nitrogen mass balance of the lake is also presented.

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