Flux Chamber Technique Research Articles

To assess the dynamics of emission effluxes of carbon dioxide (CO2) and methane (CH4) by using the flux chamber technique at Titardi (capped) and Balicha (uncapped) landfill sites of Udaipur, Rajasthan

To assess the dynamics of emission effluxes of carbon dioxide (CO2) and methane (CH4) by using the flux chamber technique at Titardi (capped) and Balicha (uncapped) landfill sites of Udaipur, Rajasthan

Numerical model for static chamber measurement of multi-component landfill gas emissions and its application

The quantitative assessment of landfill gas emissions is essential to assess the performance of the landfill cover and gas collection system. The relative error of the measured surface emission of landfill gas may be induced by the static flux chamber technique. This study aims to quantify effects of the size of the chamber, the insertion depth, pressure differential on the relative errors by using an integrated approach of in situ tests, and numerical modeling. A field experiment study of landfill gas emission is conducted by using a static chamber at one landfill site in Xi’an, Northwest China. Additionally, a two-dimensional axisymmetric numerical model for multi-component gas transport in the soil and the static chamber is developed based on the dusty-gas model (DGM). The proposed model is validated by the field data obtained in this study and a set of experimental data in the literature. The results show that DGM model has a better capacity to predict gas transport under a wider range of permeability compared to Blanc’s method. This is due to the fact that DGM model can explain the interaction among gases (e.g., CH4, CO2, O2, and N2) and the Knudsen diffusion process while these mechanisms are not included in Blanc’s model. Increasing the size and the insertion depth of static chambers can reduce the relative error for the flux of CH4 and CO2. For example, increasing the height of chambers from 0.55 to 1.1 m can decrease relative errors of CH4 and CO2 flux by 17% and 18%, respectively. Moreover, we find that gas emission fluxes for the case with positive pressure differential (∆Pin-out) are greater than that of the case without considering pressure fluctuations. The Monte Carlo method was adopted to carry out the statistical analysis for quantifying the range of relative errors. The agreement of the measured field data and predicted results demonstrated that the proposed model has the capacity to quantify the emission of landfill gas from the landfill cover systems.

Transport mechanisms and emission of landfill gas through various cover soil configurations in an MSW landfill using a static flux chamber technique

This study evaluated the transport mechanisms and emission rates of landfill gas (LFG) from 200- (vegetated with short grass), 300- (vegetated with short grass), and 450-mm-thick (non-vegetated) interim cover soils within a municipal solid waste landfill. LFG emission and diffusion mechanisms were evaluated using static flux chambers and laboratory-scale diffusion columns. Overall, the greatest CH4 and CO2 emissions were consistently observed from the 200-mm-thick cover soil with an average flux rate of 39.2 mg m−2 h−1 and 3.07 × 103 mg m−2 h−1, respectively. In addition to CH4 and CO2, H2S migration through a 450-mm interim cover soil was also evaluated. The H2S emission rate was relatively more uniform at an average of 2.47 × 10−5 mg m−2 h−1. Long-term LFG emission was predicted using an emission model based on a first-order decomposition rate equation and compared with the static flux chamber method. The field-measured CO2, CH4 and H2S emissions were less than the estimated emissions from the emission model, by 22%, 85%, and 91%, respectively. Further, the diffusion coefficients of CH4, CO2, and H2S for the interim cover soils were determined using a laboratory-scale diffusion column test and compared with a three-parameter diffusion model. The measured and estimated diffusion coefficients for the three landfill gases were within the 10% variation limits. Based on these findings, the LFG emission rate varied depending on the physical-chemical properties of the cover soil (e.g., cover thickness, moisture content, compaction ratio, uneven distribution of soil), organic material content and age of buried refuse, and seasonal environmental conditions (such as temperature). Test results showed that fugitive CH4 emissions can be reduced one fourth by utilizing an appropriate cover soil (300-mm to 450-mm, CL) compared to cases with a thinner cover soil.

CARBON DIOXIDE AND METHANE FLUX MEASUREMENTS AT A LARGE UNSANITARY DUMPING SITE IN THE AMAZON REGION

Dumps are important anthropogenic sources of greenhouse gas emissions into the atmosphere, mostly CH4. However, few studies on the subject have been carried out in the Amazon region. Several factors affect the production and emission of dumps gas. The objective of this study was to quantify the spatial variation of CO2 and CH4 production in an Amazon dump and try to associate the relative importance of some environmental factors with the fluxes. This study was carried out in an open-air dump in the metropolitan region of Belém, where approximately 11.0 million Mg of waste was deposited in 25 years, of which 6.4 million Mg was organic. The emission rates of CH4 and CO2 from the surface of the dump were determined using the closed dynamic flux chamber technique. The study was conducted in three cells of different ages, sampled in two moments between the Amazon rainy and dry season. The Aura dump has an area of 30 ha and emits a total of 51.49 Mg CO2 ha-1 month-1 and 3.16 Mg CH4 ha-1 month-1 to the atmosphere. This results in an expressive production of 1,359,961.04 Mg CO2-e year-1, being that 58.54% is due to CH4 flux. The spatial variability in CO2 and CH4 flux is very large, especially for CH4, forming hotspots of high concentrations, and perhaps because of this, the flow has not been correlated with micrometeorological variations.

Effects of water and rice straw management practices on water savings and greenhouse gas emissions from a double-rice paddy field in the Central Plain of Thailand

Abstract Rice-rice (double-rice) cropping in the Central Plain region of Thailand relies heavily on irrigation water inputs for cultivation under flooded conditions, which is increasingly constrained by water scarcity. In this production system, farmers often burn or incorporate rice straw (RS) in the field. The effects of the combined use of water and RS management on irrigated lowland double-rice cropping, with respect to irrigation water savings, grain yields, and greenhouse gas (GHG) emissions, remain largely unknown. Field experiments of two consecutive rice-growing seasons in 2016–2017 were conducted at the Ayutthaya Rice Research Center in Ayutthaya, Thailand, to investigate the effects of different water and RS management practices on irrigation water savings, rice grain yields, and GHG emissions. The treatments consisted of two water regimes (continuous flooding [CF], alternate wetting and drying [AWD; 15 cm threshold water level below the soil surface for irrigation]) and three RS management practices (RS incorporation [RS-I], RS burning [RS-B], without RS incorporation and burning [WRS]). Parameters such as irrigation water inputs, soil characteristics (pH, temperature, water content), above-ground biomass, and grain yields were measured. The static vented flux chamber technique was used to measure GHG emissions (CH4 and N2O fluxes). AWD irrigation significantly reduced water inputs compared to CF in both growing seasons; however, there were more water savings in the dry season. AWD also resulted in higher grain yields compared to CF in both growing seasons. The average CH4 emissions from WRS plots were significantly lower compared to both RS-I and RS-B plots, regardless of the growing seasons. However, RS-I and RS-B plots under AWD had 39% and 63% lower CH4 emissions, respectively, in the wet season, while the corresponding values were 37% and 36%, respectively, in the dry season compared to the average CH4 emissions from these RS treatments under CF. Water and RS management did not significantly influence the average flux of N2O emissions from paddy fields in the wet season; however, CF had a lower average N2O flux than AWD in the dry season. The average flux of N2O emissions were very low compared to the CH4 emissions flux in both seasons. Averaged across two seasons, the yield-scaled global warming potential (GWP) under AWD was reduced by 34% compared to CF, and under WRS it was reduced by 36% and 29% compared to RS-I and RS-B, respectively. RS application, either as soil incorporation or open-field burning, had little or no effect on irrigation water savings and grain yields; however, the yield-scaled GWP was significantly higher from plots with RS-I or RS-B than WRS plots. Among the water regime and RS management practices tested, AWD irrigation without any RS application (soil incorporation or burning) can be employed for maintaining the yield-scaled GWP of irrigated lowland double-rice cropping at a low level.

Quantification of fugitive emissions from an oil sands tailings pond by eddy covariance

Oil sands tailings ponds are sources of greenhouse gasses (GHG) and air pollutants. The flux chamber technique, typically used to measure emissions from tailings ponds, samples a small area for a short duration, which may not account for the spatial and temporal variability of emissions from oil sands tailings ponds. The eddy covariance (EC) technique, with large spatial coverage and better temporal resolution, is a promising method to improve the accuracy of emission flux quantification. A field campaign was conducted to measure emissions from an oil sands tailings pond in Alberta using an EC system. Average CH4 and CO2 emission fluxes were 4.56 × 10−2 g/(m2-d) and 3.59 g/(m2-d), respectively. Diurnal and daily variations of CH4 and CO2 emission fluxes were strong with relative standard deviations of 97–158%. Nighttime (18:30 to 8:00, inclusive) CH4 average emission flux (6.55 × 10−2 g/(m2-d)) was 2.8 times daytime (8:30 to 18:00, inclusive) CH4 flux (2.32 × 10−2 g/(m2-d)) while nighttime CO2 average emission flux (2.97 g/(m2-d)) was 0.7 times daytime CO2 emission flux (4.29 g/(m2-d)). Pearson correlation test results suggest that short-term (i.e., days to weeks) variations of CH4 and CO2 emission fluxes measured in this study were not strongly (but can be weakly) correlated with meteorological variables or the 90% cumulative flux contour distance. The CH4 and CO2 emission fluxes determined in this study were of the same order of magnitude as those from a previous study that used the EC technique at the same tailings pond. CO2 fluxes in this study were similar while CH4 fluxes in this study were more than an order of magnitude lower than fluxes based on flux chamber measurements conducted by a 3rd party at the same location and in the same month and year. Continuous, real-time, and long-term monitoring of tailings ponds emissions is necessary to reduce uncertainty and improve representativeness and accuracy of emission flux quantification.

Emissions of organic compounds from produced water ponds II: Evaluation of flux chamber measurements with inverse-modeling techniques

ABSTRACTIn this study, the authors apply two different dispersion models to evaluate flux chamber measurements of emissions of 58 organic compounds, including C2–C11 hydrocarbons and methanol, ethanol, and isopropanol from oil- and gas-produced water ponds in the Uintah Basin. Field measurement campaigns using the flux chamber technique were performed at a limited number of produced water ponds in the basin throughout 2013–2016. Inverse-modeling results showed significantly higher emissions than were measured by the flux chamber. Discrepancies between the two methods vary across hydrocarbon compounds and are largest in alcohols due to their physical chemistries. This finding, in combination with findings in a related study using the WATER9 wastewater emission model, suggests that the flux chamber technique may underestimate organic compound emissions, especially alcohols, due to its limited coverage of the pond area and alteration of environmental conditions, especially wind speed. Comparisons of inverse-model estimations with flux chamber measurements varied significantly with the complexity of pond facilities and geometries. Both model results and flux chamber measurements suggest significant contributions from produced water ponds to total organic compound emission from oil and gas productions in the basin.Implications: This research is a component of an extensive study that showed significant amount of hydrocarbon emissions from produced water ponds in the Uintah Basin, Utah. Such findings have important meanings to air quality management agencies in developing control strategies for air pollution in oil and gas fields, especially for the Uintah Basin in which ozone pollutions frequently occurred in winter seasons.

Comprehensive effects of a sedge plant on CH4 and N2O emissions in an estuarine marsh

Although there have been numerous studies focusing on plants' roles in methane (CH4) emissions, the influencing mechanism of wetland plants on nitrous oxide (N2O) emissions has rarely been studied. Here, we test whether wetland plants also play an important role in N2O emissions. Gas fluxes were determined using the in situ static flux chamber technique. We also carried out pore-water extractions, sedge removal experiments and tests of N2O transportation. The brackish marsh acted as a net source of both CH4 and N2O. However, sedge plants played the opposite role in CH4 and N2O emissions. The removal of the sedges led to reduced CH4 emissions and increased accumulation of CH4 inside the sediment. Apart from being a conduit for CH4 transport, the sedges made a greater contribution to CH4 oxidation than CH4 production. The sedges exerted inhibitory effects on the release of N2O. The N2O was barely detectable inside the sediment in both vegetated and vegetation-removed plots. The denitrification measurements and nitrogen addition (the addition rates were equal to 0.028, 0.056 and 0.112 g m−2) experiments suggest that denitrification associated with N2O production occurred mainly in the surface sediment layer. The vascular sedge could transport atmospheric N2O downward into the rhizosphere. The rhizospheric sediment, together with the vascular sedge, became an effective sink of atmospheric N2O.

Mitigation of methane emissions in a pilot-scale biocover system at the AV Miljø Landfill, Denmark: 1. System design and gas distribution

Greenhouse gas mitigation at landfills by methane oxidation in engineered biocover systems is believed to be a cost effective technology, but so far a full quantitative evaluation of the efficiency of the technology in full scale has only been carried out in a few cases. A third generation semi-passive biocover system was constructed at the AV Miljø Landfill, Denmark. The biocover system was fed by landfill gas pumped out of three leachate collection wells. An innovative gas distribution system was used to overcome the commonly observed surface emission hot spot areas resulting from an uneven gas distribution to the active methane oxidation layer, leading to areas with methane overloading. Performed screening of methane and carbon dioxide surface concentrations, as well as flux measurement using a flux chamber at the surface of the biocover, showed homogenous distributions indicating an even gas distribution. This was supported by results from a tracer gas test where the compound HFC-134a was added to the gas inlet over an adequately long time period to obtain tracer gas stationarity in the whole biocover system. Studies of the tracer gas movement within the biocover system showed a very even gas distribution in gas probes installed in the gas distribution layer. Also the flux of tracer gas out of the biocover surface, as measured by flux chamber technique, showed a spatially even distribution.Installed probes logging the temperature and moisture content of the methane oxidation layer at different depths showed elevated temperatures in the layer with temperature differences to the ambient temperature in the range of 25–50°C at the deepest measuring point due to the microbial processes occurring in the layer. The moisture measurements showed that infiltrating precipitation was efficiently drained away from the methane oxidation layer.

Quantifying Methane Oxidation in Cover Soils of the Vancouver Landfill Using the Stable Isotope Technique

The stable isotope technique is a methodology that allows for the quantification of biologically oxidized methane (CH4) in a landfill cover. In this methodology, the oxidized fraction of methane is calculated based on the isotopic signature of the emitted CH4, the preference degree of methanotrophic bacteria in consuming methane with lighter isotopes and the isotopic signature of methane within anaerobic zone of the landfill. This study was conducted in four separate operational phases of the Vancouver landfill (VLF). These four phases were grouped into two areas based on the characteristics of the soil used as interim and/or final cover. Methane emission rates were measured using a flux chamber technique. The methane samples, which was collected from the landfill’s anaerobic zones, the flux chambers, and aerobic soil incubations test, were analysed for isotopic signature. δ13C values for methane generated in the VLF ranged between -54‰ and -58‰. All CH4 samples collected from flux chambers were enriched in 13C with δ13C values ranging between -35‰ to -56‰. The overall average oxidation fractionation factor (αox) at the VLF was 1.0266 ± 0.0037 at 25 °C. Methane oxidation ranged from 3 to 73% with mean values of 28% and 34% for two different areas of the landfill. Results suggested that the overall methane oxidation percentage, for a region with similar climatic conditions to Vancouver, may be considered more or less constant throughout the year. As our objective was to compare different sections and cover soil types across the landfill, the use of chambers to capture emitted methane was deemed appropriate. Keywords: Landfill, LFG, methane emission, methanotrophy, methane oxidation, stable isotope.

Comparison of Two Chamber Methods for Measuring Soil Trace-Gas Fluxes in Bioenergy Cropping Systems

Greenhouse gas emissions from soils are often measured using trace-gas flux chamber techniques without a standardized protocol, raising concerns about measurement accuracy and consistency. To address this, we compared measurements from non-steady-state non-through-flow (NTF) chambers with a non-steady-state through-flow (TF) chamber system in three bioenergy cropping systems located in Wisconsin. Additionally, we investigated the effects of the NTF flux calculation method and deployment time on flux measurements. In all cropping systems, when NTF chambers were deployed for 60 min and a linear regression (LR) flux calculation was used, soil CO2 and N2O fluxes were, on average, 18 and 12% lower, respectively, than fluxes measured with a 15-min deployment. Fluxes calculated with the HMR method, a hybrid of nonlinear and linear approaches, showed no deployment time effects for CO2 and N2O and produced 27 to 32% higher CO2 fluxes and 28 to 33% higher N2O fluxes in all crops than the LR approach with 60-min deployment. Across all crops, CO2 fluxes measured with the TF chamber system were higher by 24.4 to 84.9 mg CO2–C m−2 h−1 than fluxes measured with NTF chambers using either flux calculation method. These results suggest that NTF chamber deployment time should be shortened if the LR approach is used, although detection limits should be considered, and the HMR approach may be more appropriate when long deployment times are necessary. Significant differences in absolute flux values with different chamber types highlight the need for significant effort in determining the accuracy of methods or alternative flux measurement technologies.

Chemical Evaluation of Odor Reduction by Soil Injection of Animal Manure

Field application of animal manure is a major cause of odor nuisance in the local environment. Therefore, there is a need for methods for measuring the effect of technologies for reducing odor after manure application. In this work, chemical methods were used to identify key odorants from field application of pig manure based on experiments with surface application by trailing hoses and soil injection. Results from three consecutive years of field trials with full-scale equipment are reported. Methods applied were: membrane inlet mass spectrometry (MIMS), proton-transfer-reaction mass spectrometry (PTR-MS), gold-film hydrogen sulfide (H₂S) detection, all performed on site, and thermal desorption gas chromatography with mass spectrometry (TD-GC/MS) based on laboratory analyses of field samples. Samples were collected from a static flux chamber often used for obtaining samples for dynamic olfactometry. While all methods were capable of detecting relevant odorants, PTR-MS gave the most comprehensive results. Based on odor threshold values, 4-methylphenol, H₂S, and methanethiol are suggested as key odorants. Significant odorant reductions by soil injection were consistently observed in all trials. The flux chamber technique was demonstrated to be associated with critical errors due to compound instabilities in the chamber. This was most apparent for H₂S, on a time scale of a few minutes, and on a longer time scale for methanethiol.

Atmospheric Mercury Fluxes in a Southern Boreal Forest and Wetland

Total gaseous mercury (TGM) fluxes from the forest floor and a boreal wetland were measured by a flux chamber technique coupled with an automatic mercury vapour analyser. The fluxes were measured at three sampling sites in southern Finland, 61°14′ N, 25°04′ E in summer 2007, with additionally in situ TGM concentrations in the air at one of the sites and mercury bulk deposition at another. Most of the flux data were collected during the daytime. At one of the sites, diurnal flux behaviour was studied, and a clear cycle with an afternoon maximum and a night minimum was observed. The highest emissions (up to 3.5 ng m−2 h−1) were observed at the forest floor site having a moss and grass cover. At the wetland and litter-rich forest floor sites, the emissions were below 1 ng m−2 h−1 and sometimes negative (down to −1.0 ng m−2 h−1), indicating mercury uptake. The measured average fluxes in August were 0.9 ± 1.1 and 0.2 ± 0.3 ng m−2 h−1 for the forest floor sites and wetland sites, respectively. The flux data were compared with the mercury bulk deposition, which proved to be of the same magnitude, but opposite in sign. At the mossy forest floor site, the extrapolated TGM emissions were 130% of the Hg deposition in August 2007. Comparison with other studies showed that the fluxes in background areas are relatively uniform, regardless of measurement site location and method used. Airborne TGM remained at the background level during the study, with an average value of 1.3 ± 0.2 ng m−3; it frequently showed a diurnal cycle pattern.

An Initial Investigation into the Use of a Flux Chamber Technique to Measure Soil-Atmosphere Gas Exchanges from Application of Biosolids to UK Soils

While a significant amount of work has been conducted to assess the concentration of pollutants in soils and waterways near land that has been amended with biosolids, a relatively small body of research investigating emissions to atmosphere is available in the literature. Some studies have indicated that while the CO2emissions from soils decrease with fertiliser application, the CH4and N2O emissions might be increased, offsetting the benefit. The objective of the research presented in this paper was to address this gap, by the use of a flux chamber technique to measure soil-atmosphere gas exchanges from the application of biosolids to land. This was done by applying three different types of biosolids to soils and measuring gases at the soil-atmosphere interface. The measurements were taken on areas with three different types of vegetation. The gases were collected using a flux chamber technique and analysed by gas chromatography. The results presented here are preliminary findings of an ongoing experiment. Insignificant variation appeared to occur between different areas of vegetation; however, small variations in gas concentrations were observed indicating a need for continued monitoring of soil-atmosphere gas exchanges to determine the long-term impacts on the atmosphere and the environment.

The impact of slurry application technique on nitrous oxide emission from agricultural soils

Direct nitrous oxide (N2O) emissions from fertilized soils are generally estimated using emission factors. However, the emission factors for N2O emission of applied slurry are not well quantified. The effect of slurry application technique on N2O emission was quantified in field experiments in the Netherlands in order to derive N2O emission factors for (shallow) injected and surface-applied cattle and pig slurries. Fluxes of N2O were measured using a closed flux chamber technique and a photo-acoustic infra-red gasmonitor. Fluxes of N2O were measured 64–83 times on grassland on sandy and clay soils and maize land on sandy soil, in the period 2007–2009. There were large differences in total N2O emission between the years, and differences between treatments were not consistent over the years and sites. The average emission factor of all treatments and years (n=35) was 0.9% of the N applied, which is close to the default IPCC emission factor of 1%. However, the range in emission was large, i.e. from −0.2% to 7.0%. The average emission factor for grassland was 1.7% of the N applied for calcium ammonium nitrate (CAN), 0.4% for shallow injected cattle slurry, and 0.1% for surface-applied cattle slurry. For maize land, the average emission factor for CAN was 0.1% of the N applied, for injected cattle slurry 0.9% and for surface-applied cattle slurry 0.4%. The emission factors for pig slurry applied to maize land were higher than for cattle slurry; 3.6% for injected pig slurry and 0.9% for surface-applied pig slurry. Increasing the N application rate on maize land resulted in higher emission factors for CAN, injected cattle slurry, and injected pig slurry. Concluding, on both grassland and maize land (shallow) injection of slurry increased the average emission factor of N2O in comparison to surface application. Differentiation of N2O emission factors which takes specific factors into account, such as N type and rate and application technique, can improve the quantification of N2O emission from agricultural soils and is needed to derive most efficient options for mitigation.

Measurement of carbon dioxide fluxes in a free-air carbon dioxide enrichment experiment using the closed flux chamber technique

Abstract Carbon dioxide (CO2) fluxes, composing net ecosystem exchange (NEE), ecosystem respiration (ER), and soil respiration (SR) were measured in a temperate heathland exposed to elevated CO2 by the FACE (free-air carbon enrichment) technique, raising the atmospheric CO2 concentration from c. 380 μmol mol−1 to 510 μmol mol−1. All CO2 fluxes were measured by the static chamber methodology. Although the FACE technique enriches the atmosphere with CO2 to a fixed level, the above ground CO2 concentrations may nevertheless locally vary strongly (from about ambient to ∼1000 μmol mol−1). Deployment of static chambers to FACE experiments should therefore be performed with great care in order to ensure reproducible conditions with respect to chamber headspace CO2 concentration. We demonstrate that that the fluxes measured by closed chambers relate linearly to the initial headspace CO2 concentration. When changing the initial headspace CO2 concentration from 380 to 510 μmol mol−1 the net CO2 assimilation expressed by NEE increased instantaneously 1.51 times in control plots and 1.71 times in FACE plots. By contrast, ER in control plots decreased, being 0.87 times that measured at the low CO2 concentration, and the flux also decreased in FACE plots, to 0.79 times that at low concentration. Similar SR in control plots was decreased 0.94 times in control plots and 0.88 times in FACE plots. We found that a useful method to achieve stable and reproducible chamber headspace and soil CO2 concentration prior to commencement of flux measurements was to turn off the FACE system at least 10 min in advance. Within 10 min a new equilibrium was established between the soil and atmosphere, apparently due to CO2 degassing from the top soil. The observed increase in SR in response to increased CO2 persisted for up to 18 h during which measurements should be performed. Soil CO2 concentrations were increased by up to 500 μmol mol−1 by the FACE treatment, substantially more than the 130 μmol mol−1 enrichment achieved in the atmosphere suggesting that the increased SR flux was caused by increased belowground respiration.

Technical Note: A flux chamber for measuring gas emissions from rabbits

Atmospheric pollution related to gas emissions from livestock production has become an issue of increasing interest. International commitments bind countries to provide annual reports on national emissions, however there is a lack of information regarding the estimation of emissions from rabbit farms. There are several methodologies available to measure gas emissions, the flux chamber technique being one of the most commonly used. In this study, a flux chamber was designed to measure emissions from small farm animals and their manure, as well as the methodology to calculate ventilation fluxes appropriate for each experiment. After the chamber was constructed, two experiments were carried out to test its operation, design and construction. Firstly, carbon dioxide emissions from fattening rabbits were measured for 24 and 48 h. Emissions from fattening rabbit manure were then measured for one-hour periods. The operation of the flux chamber was satisfactory during both experiments and notes were taken of possible improvements in performance through future research. Recommendations for its use are also summarized.

A comparative assessment of four methods for estimating ammonia emissions at microclimatic locations in a dairy building

Ammonia emissions were estimated at five microclimatic locations in a free stall dairy building using four different methods. Measurements were performed simultaneously with the different methods to enable comparison. In the first method, the rate of ammonia emission from manure was theoretically modeled utilizing Fick's law and boundary layer theory. In the second method, recirculation flux-chamber technique was used to model ammonia emission from manure. In the third and fourth methods, respectively, carbon dioxide and methane balances were employed to calculate ammonia emission. The mean ammonia emissions measured from the five locations using the different methods ranged from 0.10 to 0.15 g m(-2) h(-1). The percentage of variation of ammonia emission from the different location ranged between 8 and 52% for the different methods. Recorded ammonia emission rates in the dairy building were from 0.04 to 0.25 g m(-2) h(-1). The percentage of variation in ammonia, carbon dioxide, methane, and manure properties in the building was 50%. Two-way statistical analysis of variance showed that there were no significant differences (p > 0.63) between the four different methods or between the measurements obtained at the five locations (p > 0.90).

Identification of Seasonal Variations in Volatile Sulfur Compound Formation and Release from the Secondary Treatment System at a Large Wastewater Treatment Plant

The purpose of this study was to identify, quantify, and determine source locations of significant volatile sulfur compounds (VSCs) associated with the activated sludge treatment process at a large wastewater treatment plant. Flux chamber and wastewater headspace sampling techniques were used to capture odorous gases followed by gas chromatography mass spectrometry analysis. Olfactometric analysis corroborated the results from the chemical analysis. Dimethylsulfide (DMS) and dimethyldisulfide (DMDS) concentrations in wastewater were strongly correlated with sludge blanket depth [DMDS: r = 0.86 (p < 0.001, df = 24) and DMS: r = 0.72 (p < 0.001, df = 24)]. A strong statistical correlation also was established between concentrations of these two odorants in the gas samples and the recognition odor concentration [DMS: r = 0.85 (p < 0.001, df = 13) and DMDS: r = 0.81 (p < 0.001, df = 13)]. Results indicate that settled sludge in the anoxic environment of the secondary sedimentation basin is the most important contributor to the formation of VSCs in the activated sludge treatment system.

Greenhouse Gas Emission Potential of the Municipal Solid Waste Disposal Sites in Thailand

Open dumping and landfilling are the prevalent solid waste disposal practices in Thailand. Surveys on the disposal sites revealed the presence of 95 landfills and 330 open dumps. Methane emission potential at these sites was estimated by three methods. Results of the Intergovernmental Panel on Climate Change (IPCC) method, Landfill Gas Emission model (LandGEM), and closed flux chamber technique were compared. The methane emission potential of 366 Gg/yr using the IPCC method was higher than the estimations of the LandGEM and closed flux chamber method of 115 Gg/yr and 103 Gg/yr, respectively. An understanding of the methane emission potential initiated the analysis of upgrading the open dumps into landfills, adding landfills to meet the future needs and utilization of landfill gases. Upgrading the open dumps to landfills increased the methane emission rates and their utilization potential. Approximately 20 additional landfills may be required to meet future demands. Landfill gas (LFG) utilization appears to be feasible in the large-scale landfills.