Kinetic pathways for the anaerobic decomposition of Ludwigia inclinata

Abstract

This study is aimed at using kinetic modeling to investigate the yield of mineralization products from anaerobic decomposition of the aquatic macrophyte Ludwigia inclinata. The initial hypothesis was that the decay of different fractions of detritus and the kinetics of gases productions are both positively correlated to temperature. The plants and water samples were collected from a tropical oxbow lake; the anaerobic decomposition was described using incubations maintained at controlled temperatures. The methane and carbon dioxide productions were determined daily by gas chromatography. The mass loss of detritus owing to leaching and chemical oxidation was also measured, with the results being used to develop a mathematical (kinetic) model considering the heterogeneity of the resource and three mineralization pathways: (i) oxidation of the labile particulate organic carbon; (ii) formation of dissolved organic carbon leached from the detritus, and subsequent oxidation of those compounds; and (iii) oxidation of refractory particulate organic carbon (RPOC). The temperature did not affect the leaching rate constant or the mineralization of labile and dissolved fractions. On the other hand, the mineralization of RPOC was improved with increasing temperatures. The yield of CO 2 formation was higher at 20.1°C and decreased with increasing temperatures. The methanogenesis was significantly affected by the temperature; it abbreviated the beginning of the process and increased the CH 4 yield. Conversely as hypothesized, the results suggest that the increase in temperature improved the decay rates of RPOC, but did not affect the leaching process and the subsequent leachate oxidation. Furthermore, the rising temperatures had positive correlation with methanogenesis and negative with CO 2 production.

Emissão de metano por decomposição de resíduo florestal inundado

“…Tal combinação deve ter favorecido a produção de CH 4 , pois no intervalo de 10 a 45 ºC a taxa de crescimento da população microbiana duplica a cada 10 °C de aumento na temperatura da água (Rittmann & McCarty, 2001). Em adição, temperaturas maiores que 20 ºC aumentam a solubilização da matéria orgânica (Gujer & Zehnder, 1983), ao mesmo tempo em que favorecem a produção de CH 4 , confirmando que o processo de metanogênese é mais sensível à variação deste parâmetro se comparado aos demais processos de mineralização (Romeiro & Bianchini Jr., 2008;Bianchini Jr. et al, 2010).…”

Decomposition of aquatic macrophytes from Cantá stream (Roraima, Brazil): kinetics approach

“…For an oxbow lake Ballester and Santos (2001) reported maximum rates of gas formation between the 80º and 90º days of incubation, with formation of CO 2 and CH 4 and, in general, prevalence of gas production over consumption. Assays on anaerobic decomposition of Ludwigia sedoides in different temperatures indicated that CO 2 formation were produced from the first day of decomposition; in relation to methanogenesis, this gases formation presented different genesis periods: 15 th day at 29.9 °C and 99 th at 15.0 °C (Romeiro and Bianchini Jr., 2008).…”

As Rotas De Liberação Do Carbono Dos Detritos De Macrófitas Aquáticas

“…Contudo, em condições anaeróbias, o aumento da temperatura constitui-se num fator extremamente importante para a geração de CH 4 . A esse respeito, verifi cou-se na decomposição de Ludwigia inclinata (Romeiro & Bianchini Jr. 2008) que a produção de metano correspondeu de 0,4 a 9,8% de perda de massa dos detritos em função do aumento da temperatura (de 15 a 30ºC). Os maiores rendimentos de metano em temperaturas mais elevadas também foram observados na decomposição de Egeria najas (CH 4 =13,4% a 18ºC; CH 4 =28,6% a 27ºC) (Bitar et al 2006).…”