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Year 2014

Volume 5, Issue 2 April - June 2014

Abstract: This study analyzed the monthly rainfall data of the Global Precipitation Climatology Centre (GPCC) over Thailand, covering the period of 1971 to 2010 using the Empirical Orthogonal Function (EOF) technique. The most dominant mode accounts for 21.6% of the total variance. The next part was a study of the relationship with ENSO using smoothed anomalies between the Nino 3.4 index and the principal component time series.It was found that the Nino 3.4 SST index leads the rainfall anomalies by 4 months. This study used ENSO events divided into weak and strong intensity classes. It was based on composites of fourteen weak La Nina events, six strong La Nina events, twelve weak El Nino events and six strong El Nino events. It was found that there was high rainfall in La Nina events, whereas there was low rainfall in El Nino events. Also, we constructed the corresponding wind circulation and sea level pressure maps in order to better understand the mechanisms associated with this phenomenon that have affected rainfall variability over Thailand.

Keywords: Rainfall over Thailand, EOF, ENSO. (1.37 M)
Abstract: Three land use types in Thailand; 1) the natural forests (hill evergreen forest (HEF), dry evergreen forest (DEF), moist evergreen forest (MEF) and mixed deciduous forest (MDF)), 2) a reforested forest (ARF) and 3) agricultural field (AG) were studied for their methane fluxes, oxidation potential and kinetics. Net atmospheric methane consumption was observed at all forest and reforested sites, with the montly consumption rate raning from -0.6 mg CH4 m-2 day-1 at the reforested site to 2.4 mg CH4 m-2 day-1 at the hill evergreen forest site. At the agricultural site the net methane emission of 13.6 mg CH4 m-2 day-1 was found. At dry evergreen forest and reforested sites, a clear zonation for active methane oxidation layer was detected along the soil depths. The most active oxidation lied between 15 cm and 40 cm while in agricultural soil no clear active layer was observed. Stratification of active oxidation zones coincided with the trends of inorganic nitrogen content profile. In DEF and ARF soils, high concentration of inorganic nitrogen compounds (usually > 100 mg NO3- or NH4+ ⋅ kg soil-1) was detected in the top 15-cm soil while there was no clear distribution trend found in AG soil. Examining kinetic coefficients of these active layers revealed that soil at all natural forest sites had high affinity for methane (Km of 52 ppmv) but rather low methanotrophic capacity (Vmax of 0.82 nmol⋅g soil-1 ⋅ h-1). Soil at ARF and AG sites, on the other hand, showed low affinity for methane (Km of 724 ppmv and 1454-2362 ppmv, respectively). However, soils at these two sites were capable of oxidizing high concentration of methane (Vmax about 10 nmol ⋅ g soil-1 ⋅ hr-1). These results indicate that land use type significantly affects rates, depth distribution and kinetics of methane oxidation in tropical soils.

Keywords: Methane oxidation, depth distribution, methane oxidation kinetics, and land use. (445 K)
Abstract: This article presents some important concepts of climate models without any mathematical jargon. The purpose is to provide a broad idea on how climate models work. Background information on climate system and natural climate variation is also included.
(40 K)
Abstract: The purpose of this study is to assess the practicality of algal biofuel production and consumption in Bangkok, Thailand based on the environmental impacts of and ability to offset the petroleum equivalents. A life cycle assessment was conducted to determine the environmental impacts of algal biofuels - biodiesel, ethanol, and compressed biomethane - replacing low-sulfur diesel, standard gasoline, and compressed natural gas (CNG), respectively. Three scenarios with two algae strains were compared for the production of biofuels using net energy ratio (NER) and vehicle kilometers traveled (VKT). For B. braunii, the biodiesel and compressed biomethane producing scenario had the highest VKT of 1,220,000 and an NER of 1.26 using a functional unit of 1 hectare of algal ponds. For the “generic” strain, biodiesel and compressed biomethane produced the highest VKT of 1,200,000 with a NER of 1.25. For B. braunii and generic strains, the production of only compressed biomethane showed NERs of 1.45 and 1.50 respectively, but VKTs of 936,000 and 976,000. Environmental impacts from algal biofuels are higher than petroleum fuels in all categories considered. Available land area would yield enough algal biofuels to replace <1% of petroleum fuel usage. While there is a positive energy ratio associated with the production of algal fuels, Bangkok’s planners need to consider the limited land availability and the higher pollution from algal fuels before committing to an algal biofuel program.

Keywords: Algae, biofuels, B. braunii, life cycle assessment, petroleum, renewable.
(309 K)

 

 

ISSN: 1906-4918
Frequency: Quartery
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