143 research outputs found

    Climate-Based Suitability Assessment for Methane Mitigation by Water Saving Technology in Paddy Fields of the Central Plain of Thailand

    Get PDF
    The alternate wetting and drying (AWD) water management technique has been identified as one of the most promising options for mitigating methane (CH4_{4}) emissions from rice cultivation. By its nature, however, this option is limited only to paddy fields where farmers have sustained access to irrigation water. In addition, large amounts of rainfall often make it difficult to drain water from paddy fields. Therefore, it is necessary to understand the specific conditions and suitability of an area in which AWD is foreseen to be applied before its CH4_{4} mitigation potential can be assessed in view of planning regional and national mitigation actions. In this study, we applied a methodology developed for assessing the climatic suitability of AWD to paddy fields in the central plain of Thailand in order to determine the potential spatial and temporal boundaries given by climatic and soil parameters that could impact on the applicability of AWD. Related to this, we also assessed the CH4_{4} mitigation potential in the target provinces. Results showed that the entire area of the six target provinces was climatically suitable for AWD in both the major (wet) and second (dry) rice seasons. A sensitivity analysis accounting for uncertainties in soil percolation and suitability classification indicated that these settings did not affect the results of the suitability assessment, although they changed to some extent the distribution of moderate and high climatic suitability areas in the major rice season. Following the methodologies of the Intergovernmental Panel on Climate Change Guidelines, we estimated that the AWD scenario could reduce annual CH4_{4} emissions by 32% compared with the emissions in the baseline (continuously flooded) scenario. The potential of AWD for annual CH4_{4} emission reduction was estimated to be 57,600 t CH4_{4} year−1^{-1}, equivalent to 1.61 Mt CO2_{2}-eq year−1^{-1}, in the target provinces. However, we recognize the possibility that other parameters not included in our current approach may significantly influence the suitability of AWD and thus propose areas for further improvement derived from these limitations. All in all, our results will be instrumental in guiding practitioners at all levels involved in water management for rice cultivation

    Strategies to Suppress Hydrogen-Consuming Microorganisms Affect Macro and Micro Scale Structure and Microbiology of Granular Sludge

    Get PDF
    Treatment of anaerobic granules with heat and two chemical treatments, contacting with 2-bromoethanesulfonate (BES) and with BESþChloroform, were applied to suppress hydrogen-consuming microorganisms. Three mesophilic expanded granular sludge bed (EGSB) reactors— RHeat, RBES, and RBESþChlo—were inoculated with the treated sludges and fed with synthetic sugar-based wastewater (5 gCOD L 1, HRT 20–12 h). Morphological integrity of granules and bacterial communities were assessed by quantitative image analysis and 16S rRNA gene based techniques, respectively. Hydrogen production in RHeat was under 300mLH2 L 1 day 1, with a transient peak of 1,000 mLH2 L 1 day 1 after decreasing HRT. In RBESþChlo hydrogen production rate did not exceed 300mLH2 L 1 day 1 and there was granule fragmentation, release of free filaments from aggregates, and decrease of granule density. In RBES, there was an initial period with unstable hydrogen production, but a pulse of BES triggered its production rate to 700 200mLH2 L 1 day 1. This strategy did not affect granules structure significantly. Bacteria branching within Clostridiaceae and Ruminococcaceae were present in this sludge. This work demonstrates that, methods applied to suppress H2-consuming microorganisms can cause changes in the macro- and microstructure of granular sludge, which can be incompatible with the operation of high-rate reactors.European Community fund FEDER Contract grant number: FCOMP-01-0124-FEDER-007087; PTDC/BIO/69745/2006; SFRH/ BD/29823/2006; SFRH/BD/48965/2008Fundação para a Ciência e a Tecnologia (FCT

    On the independence of hydrogen production from methanogenic suppressor in olive mill wastewater

    Get PDF
    Anaerobic degradation of olive mill wastewater (OMW) at concentrations ranging from 2 to 100 g/L of chemical oxygen demand (COD) was assessed in batch assays. Methane was the main final product obtained for the lower concentrations tested. For 25 g COD/L, H2 was temporarily produced, albeit H2 depletion occurred, likely due to homoacetogenesis, since acetate was formed concomitantly. Hydrogen was produced and accumulated permanently in the assays containing 50 g COD/L of OMW. Methanogenesis and homoacetogenesis were naturally inhibited, suggesting that hydrogen recovery from OMW can be performed without the addition of methanogenic suppressors such as 2-bromoethanosulfonate. This fact opens new perspectives for the utilization of high OMW concentrations in a two-stage valorisation process combining biohydrogen and biomethane production.The authors thank the FCT Strategic Project PEst-OE/EQB/LA0023/2013, the FCT Project RECI/BBB-EBI/0179/2012, the Project "BioEnv - Biotechnology and Bioengineering for a sustainable world", REF. NORTE-07-0124-FEDER-000048, co-funded by the Programa Operacional Regional do Norte (ON.2 - O Novo Norte), QREN, FEDER. Also through the project PTDC/ENR/69755/2006 and grants given to Marta Goncalves SFRH/BD/40746/2007, Jose Carlos Costa SFRH/BDP/48962/2008 and Angela A Abreu SFRH/BPD/82000/2011

    Using isotope dilution assays to understand speciation changes in Cd, Zn, Pb and Fe in a soil model system under simulated flooding conditions

    Get PDF
    Flooded soils are systems with complex chemistry and understanding the mechanisms that control the mobility and bioavailability of metals in these soils is important for their management. This work uses stable metal multi-element isotopic dilution combined with sequential extraction assays to help understand the changes in solid and solution speciation of Cd, Fe, Pb and Zn in a contaminated soil following submergence. However, it is necessary to ensure that the isotopic dilution principles, originally developed for aerobic soils, are not compromised; in particular due to the presence of non-labile colloids in the solution phase. In particular, no studies examining the validity of these assays in systems where rapid pH and Eh changes are occurring due to fermentation reactions have been published. Thus sucrose (0.42% and 1.26% added C) was used as a carbon source to stimulate bacterial mediated fermentation reactions allowing changes in Cd, Zn, Fe and Pb isotopic exchangeability, speciation and solution chemistry to be examined after 10, 20 and 42 days of submergence. Without the addition of added C, submergence for 42 days only produced minor changes in the speciation of the metals in solid or solution phases. However, the presence of easily labile carbon produced significant responses depending on the quantity of C added. Assessments of whether fermentation products caused over-estimation of the isotopically exchangeable pool of metals (E-values) were made by measuring concentrations with and without a resin purification step. Results showed generally good agreement over a pH range of 4–7 for Pb, Cd, Zn and Fe and demonstrate that fermentation by-products do not induce the formation of non-exchangeable metal colloids. E-value concentrations were compared with fractions extracted using a modified Tessier sequential extraction. With no carbonate phases present in the soils, the E-values for Cd, Zn, Fe and Pb compared favourably with the concentrations of metal present in the combined solution, exchangeable and specifically adsorbed fractions. This provided additional evidence that the conditions for the isotopic dilution assays were not violated as these fractions should be isotopically exchangeable. Combining results from the different treatments and stages of the reduction process, strong pH dependence was found for the isotopically exchangeable and the solution pools of Cd, Zn and Pb

    Variations of Energy Fluxes and Ecosystem Evapotranspiration in a Young Secondary Dry Dipterocarp Forest in Western Thailand

    No full text
    Deforestation, followed by abandonment and forest regeneration, has become one of the dominant types of land cover changes in the tropics. This study applied the eddy covariance (EC) technique to quantify the energy budget and evapotranspiration in a regenerated secondary dry dipterocarp forest in Western Thailand. The mean annual net radiation was 126.69, 129.61, and 125.65 W m−2 day−1 in 2009, 2010, and 2011, respectively. On average, fluxes of this energy were disaggregated into latent heat (61%), sensible heat (27%), and soil heat flux (1%). While the number of energy exchanges was not significantly different between these years, there were distinct seasonal patterns within a year. In the wet season, more than 79% of energy fluxes were in the form of latent heat, while during the dry season, this was in the form of sensible heat. The energy closure in this forest ecosystem was 86% and 85% in 2010 and 2011, respectively, and varied between 84–87% in the dry season and 83–84% in the wet season. The seasonality of these energy fluxes and energy closure can be explained by rainfall, soil moisture, and water vapor deficit. The rates of evapotranspiration also significantly varied between the wet (average 6.40 mm day−1) and dry seasons (3.26 mm day−1)
    • …
    corecore