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1.
ABSTRACT Methane exchange with the atmosphere was measured during three seasons at the Rooney Road landfill in Jefferson County, CO. Substantial spatial and temporal variability in exchange rates were observed. Mean fluxes to the atmosphere were 534, 1290, and 538 mg CH 4/m 2/day, respectively, in the fall of 1994, winter of 1994–1995, and summer of 1995. Median fluxes were 12.42, 8.62, and 5.65 mg CH 4/m 2/day, respectively, during those seasons. Forty-three of 177 measurements had small negative fluxes, suggesting methanotrophic activity in the landfill cover soils. Despite probable methanotrophic activity in cover soils, landfills without gas collection systems may emit substantial CH 4 to the atmosphere, with large spatial and seasonal variability. 相似文献
2.
We have used a global version of the Regional Air Pollution Information and Simulation (RAINS) model to estimate anthropogenic emissions of the air pollution precursors sulphur dioxide (SO 2), nitrogen oxides (NO x), carbon monoxide (CO), primary carbonaceous particles of black carbon (BC), organic carbon (OC) and methane (CH 4). We developed two scenarios to constrain the possible range of future emissions. As a baseline, we investigated the future emission levels that would result from the implementation of the already adopted emission control legislation in each country, based on the current national expectations of economic development. Alternatively, we explored the lowest emission levels that could be achieved with the most advanced emission control technologies that are on the market today. This paper describes data sources and our assumptions on activity data, emission factors and the penetration of pollution control measures. We estimate that, with current expectations on future economic development and with the present air quality legislation, global anthropogenic emissions of SO 2 and NO x would slightly decrease between 2000 and 2030. For carbonaceous particles and CO, reductions between 20% and 35% are computed, while for CH 4 an increase of about 50% is calculated. Full application of currently available emission control technologies, however, could achieve substantially lower emissions levels, with decreases up to 30% for CH 4, 40% for CO and BC, and nearly 80% for SO 2. 相似文献
3.
To investigate whether wind is a significant driving force in the diffusion of CO and CH 4 from the atmosphere into soil, we measured the concentrations of these two gases at two heights above a temperate grass field in Japan and estimated their deposition velocities using micrometeorological techniques. The concentrations were inversely correlated with wind speed, indicating that the local concentrations were influenced by ground sources. The CO and CH 4 concentrations at 0.33 m were usually lower than those at 1.3 m. Although nocturnal data are suspected to be non-stationary, by selecting several periods when the changes of the concentrations were small but larger than analytical precision, we obtained a CO velocity of 2.9 and 3.9×10 −2 cms −1, agreeing with a CO deposition velocity, 3.4×10 −2 cms −1, obtained by applying a method using CO 2 as a tracer. The CH 4 influx obtained by the method using CO 2 as a tracer was 13 ngm −2 s −1. The ranges of the CO deposition velocity and CH 4 influx were similar to those obtained in previous studies in grassfields and in a nearby arable field using a closed-chamber technique. This shows that light winds do not greatly accelerate CO and CH 4 uptake by soil. 相似文献
4.
The objective of this study was to characterize exhaust emissions from a series of handheld, 2-stroke small engines. A total of 23 new and used engines from model years 1981–2003 were studied; these engines spanned three phases of emission control (pre-control, phase-1, phase-2). Measured emissions included carbon monoxide (CO), carbon dioxide (CO 2), nitrogen oxides (NO x), hydrocarbons (HC), fine particulate matter (PM 2.5), and sulfur dioxide (SO 2). Emissions reductions in CO (78%) and HC (52%) were significant between pre-control and phase-2 engines. These reductions can be attributed to improvements in engine design, reduced scavenging losses, and implementation of catalytic exhaust control. Total hydrocarbon emissions were strongly correlated with fuel consumption rates, indicating varying degrees of scavenging losses during the intake/exhaust stroke. The use of a reformulated gasoline containing 10% ethanol resulted in a 15% decrease in HC and a 29% decrease in CO emissions, on average. Increasing oil content of 2-stroke engine fuels results in a substantial increase of PM 2.5 emissions as well as smaller increases in HC and CO emissions. Results from this study enhance existing emission inventories and appear to validate predicted improvements to ambient air quality through implementation of new phase-2 handheld emission standards. 相似文献
5.
Rates of CO 2 production in the reaction CO + OH and CO + OH + halocarbon have been used to determine rate constants for some OH + halocarbon reactions at 29.5°C relative to that of k(CO + OH) = 2.69 × 10 ?13 cm 3 molecule ?1 sec ?1. The following rate constants were obtained: k(OH + CH 3Cl) = 3.1 ± 0.8, k(OH + CH 2Cl 2) = 2.7 ± 1.0, k(OH + C 2H 5Cl) = 44.0 ± 25, k(OH + CICH 2CH 2CI) = 6.5, (<29) and k(OH + CH 3CCl 3) = 2.1 (<5.7) cm 3 molecule ?1 sec ?1 × 10 ?14. The k values, CH 2Cl 2 excepted, are in substantial agreement with determinations made in nonoxygen environments. The present results for CH 2Cl 2 are almost certainly in error due to difficulties with the competitive approach used. 相似文献
6.
Abstract Comprehensive field studies were initiated in 2002 to measure emissions of ammonia (NH 3), hydrogen sulfide (H 2S), carbon dioxide (CO 2), methane (CH 4), nonmethane hydrocarbons (NMHC), particulate matter <10 µm in diameter, and total suspended particulate from swine and poultry production buildings in the United States. This paper focuses on the quasicontinuous gas concentration measurement at multiple locations among paired barns in seven states. Documented principles, used in air pollution monitoring at industrial sources, were applied in developing quality assurance (QA) project plans for these studies. Air was sampled from multiple locations with each gas analyzed with one high quality commercial gas analyzer that was located in an environmentally controlled on-farm instrument shelter. A nominal 4 L/min gas sampling system was designed and constructed with Teflon wetted surfaces, bypass pumping, and sample line flow and pressure sensors. Three-way solenoids were used to automatically switch between multiple gas sampling lines with ≥10 min sampling intervals. Inside and outside gas sampling probes were between 10 and 115 m away from the analyzers. Analyzers used chemiluminescence, fluorescence, photoacoustic infrared, and photoionization detectors for NH 3, H 2S, CO 2, CH 4, and NMHC, respectively. Data were collected using personal computer-based data acquisition hardware and software. This paper discusses the methodology of gas concentration measurements and the unique challenges that livestock barns pose for achieving desired accuracy and precision, data representativeness, comparability and completeness, and instrument calibration and maintenance. 相似文献
7.
This paper presents a statistical model that is able to predict carbon monoxide (CO) concentrations as a function of meteorological conditions and various air quality parameters. The experimental work was conducted in an urban atmosphere, where the emissions from cars are prevalent. A mobile air pollution monitoring laboratory was used to collect data, which were divided into two groups: a development group and a testing group. Only the development dataset was used for developing the model. The model was determined by using a stepwise multiple regression modelling procedure. Thirteen independent variables were selected as inputs: non-methane hydrocarbon (NMHC), methane (CH 4), suspended dust, carbon dioxide (CO 2), nitrogen oxide (NO), nitrogen dioxide (NO 2), sulfur dioxide (SO 2), ozone (O 3), wind speed, wind direction, temperature, relative humidity and solar energy. It was found that NO has the most effect on the predicted CO concentration. The contribution of NO to the CO concentration variations was 91.3%. Adding in the terms for NO 2), NMHC and CH 4 improved the model by only a further 2.3%. The derived model was shown to be statistically significant, and model predictions and experimental observations were shown to be consistent. 相似文献
8.
The gas phase thermal decomposition rates of the C 1 and C 2-substituted peroxyacyl nitrates (RC(O)OONO 2), PAN (R = CH 3), PPN (R = C 2H 5) and vinyl-PAN (R = CH 2 = CH-) have been measured at ambient temperature (288 - 299 K) and 1 atm. of air. Our results for PAN (k = A exp (-E a/RT), log 10 (A, s -1) = 16.2 ± 1.6, E a = 26.9 ± 2.1 kcal / mol, k 298 = 3.0 × 10 ?4S ?1) are consistent with literature data. Thermal decomposition rates for PPN and vinyl-PAN are similar to that for PAN, with k 298 = 3.0 × 10 ?4S ?1 for PAN, 3.4 × 10 ?4S ?1 for PPN and 3.0 × 10 ?4S ?1 for vinyl-PAN. Implications for the atmospheric persistence of PPN and vinyl-PAN as compared to that of PAN are briefly discussed. 相似文献
9.
ABSTRACT In this paper, methane emissions from municipal wastewater treatment plants and municipal solid waste (MSW) landfills in Jordan for 1994 have been estimated using the methodology developed by the Intergovernmental Panel on Climate Change (IPCC). For this purpose, the 14 domestic wastewater treatment plants in the country were surveyed. Generation rates and characterization of MSW components as well as dumping and landfilling practices were surveyed in order to estimate 1994 CH 4 emissions from these sites. Locally available waste statistics were used in cases where those of the IPCC guidelines were not representative of Jordan's statistics. Methane emissions from domestic wastewater in Jordan were estimated at 4.66 gigagrams (Gg). Total 1994 CH 4 emissions from MSW management facilities in Jordan are estimated at 371.76 Gg—351.12 Gg (94.45%) from sanitary landfills, 19.83 Gg (5.33%) from MSW open dumps, and 0.81 Gg (0.22%) from raw sewage-water dumping ponds. Uncertainties associated with these estimations are presented. 相似文献
10.
Multi-year inventories of biomass burning emissions were established in the Pearl River Delta (PRD) region for the period 2003–2007 based on the collected activity data and emission factors. The results indicated that emissions of sulfur dioxide (SO 2), nitrogen oxide (NO x), ammonia (NH 3), methane (CH 4), organic carbon (OC), non-methane volatile organic compounds (NMVOC), carbon monoxide (CO), and fine particulate matter (PM 2.5) presented clear declining trends. Domestic biofuel burning was the major contributor, accounting for more than 60% of the total emissions. The preliminary temporal profiles were established with MODIS fire count information, showing that higher emissions were observed in winter (from November to March) than other seasons. The emissions were spatially allocated into grid cells with a resolution of 3 km × 3 km, using GIS-based land use data as spatial surrogates. Large amount of emissions were observed mostly in the less developed areas in the PRD region. The uncertainties in biomass burning emission estimates were quantified using Monte Carlo simulation; the results showed that there were higher uncertainties in organic carbon (OC) and elemental carbon (EC) emission estimates, ranging from ?71% to 133% and ?70% to 128%, and relatively lower uncertainties in SO 2, NO x and CO emission estimates. The key uncertainty sources of the developed inventory included emission factors and parameters used for estimating biomass burning amounts. 相似文献
11.
A mass screening of lung function associated with air pollutants for children is limited. This study assessed the association between air pollutants exposure and the lung function of junior high school students in a mass screening program in Taipei city, Taiwan. Among 10,396 students with completed asthma screening questionnaires and anthropometric measures, 2919 students aged 12-16 received the spirometry test. Forced vital capacity (FVC) and forced expiratory flow in 1 s (FEV 1) in association with daily ambient concentrations of particulate matter with diameter of 10 μm or less (PM 10), sulfur dioxide (SO 2), carbon monoxide (CO), nitrogen dioxide (NO 2), and ozone (O 3) were assessed by regression models controlling for the age, gender, height, weight, student living districts, rainfall and temperature. FVC, had a significant negative association with short-term exposure to O 3 and PM 10 measured on the day of spirometry testing. FVC values also were reversely associated with means of SO 2, O 3, NO 2, PM 10 and CO exposed 1 d earlier. An increase of 1-ppm CO was associated with the reduction in FVC for 69.8 mL (95% CI: −115, −24.4 mL) or in FEV 1 for 73.7 mL (95% CI: −118, −29.7 mL). An increase in SO 2 for 1 ppb was associated with the reductions in FVC and FEV 1 for 12.9 mL (95% CI: −20.7, −5.09 mL) and 11.7 mL (95% CI: −19.3, −4.16 mL), respectively. In conclusion, the short-term exposure to O 3 and PM 10 was associated with reducing FVC and FEV 1. CO and SO 2 exposure had a strong 1-d lag effect on FVC and FEV 1. 相似文献
12.
This article shows oily sawdust gasification research on countercurrent installation. Experimental research was on a laboratory scale. The main purpose of the experiment was combustible gas production with higher CH4 concentration. Gas concentrations like CO, CO2, CH4, H2, and CnHm determine syngas composition. The technological parameter’s value defines experimental conditions. Value of this was fuel to air ratio. With fuel to air ratio change, syngas composition was a differential phenomenon where it depended on the process parameters like temperature. Additionally, evaluation of methane formation from CO, H2, and CO2 was done. Methanization coefficients were based on CO and CO2 hydrogenation reactions. Component’s activity was in analogs way to syngas components changed. 相似文献
13.
Abstract The traditional technologies for odor removal of thiol usually create either secondary pollution for scrubbing, adsorption, and absorption processes, or sulfur (S) poisoning for catalytic incineration. This study applied a laboratory-scale radio-frequency plasma reactor to destructive percentage-grade concentrations of odorous dimethyl sulfide (CH 3SCH 3, or DMS). Odor was diminished effectively via reforming DMS into mainly carbon disulfide (CS 2) or sulfur dioxide (SO 2). The removal efficiencies of DMS elevated significantly with a lower feeding concentration of DMS or a higher applied rf power. A greater inlet oxygen (O 2)/DMS molar ratio slightly improved the removal efficiency. In an O 2-free environment, DMS was converted primarily to CS 2, methane (CH 4), acetylene (C 2H 2), ethylene (C 2H 4), and hydrogen (H 2), with traces of hydrogen sulfide (H 2S), methyl mercaptan (CH 3SH), and dimethyl disulfide. In an O 2-containing environment, the species detected were SO 2, CS 2, carbonyl sulfide, carbon dioxide (CO 2), CH 4, C 2H 4, C 2H 2, H 2, formal-dehyde, and methanol. Differences in yield of products were functions of the amounts of added O 2 and the applied power. This study provided useful information for gaining insight into the reaction pathways for the DMS dissociation and the formation of products in the plasmolysis and conversion processes. 相似文献
14.
During the continuous monitoring of atmospheric parameters at the station Cape Point (34°S, 18°E), a smoke plume originating from a controlled fire of 30-yr-old fynbos was observed on 6 May 1997. For this episode, which was associated with a nocturnal inversion and offshore airflow, atmospheric parameters (solar radiation and meteorological data) were considered and the levels of various trace gases compared with those measured at Cape Point in maritime air. Concentration maxima in the morning of 6 May for CO 2, CO, CH 4 and O 3 amounted to 370.3 ppm, 491 ppb, 1730 ppb and 47 ppb, respectively, whilst the mixing ratios of several halocarbons (F-11, F-12, F-113, CCl 4 and CH 3CCl 3) remained at background levels. In the case of CO, the maritime background level for this period was exceeded by a factor of 9.8. Differences in ozone levels of up to 5 ppb between air intakes at 4 and 30 m above the station (located at 230 m above sea level) indicated stratification of the air advected to Cape Point during the plume event. Aerosols within the smoke plume caused the signal of global solar radiation and UV–A to be attenuated from 52.4 to 13.0 mW cm −2 and from 2.3 to 1.3 mW cm −2, respectively, 5 h after the trace gases had reached their maxima. Emission ratios (ERs) calculated for CO and CH 4 relative to CO 2 mixing ratios amounted to 0.042 and 0.0040, respectively, representing one of the first results for fires involving fynbos. The CO ER is somewhat lower than those given in the literature for African savanna fires (average ER=0.048), whilst for CH 4 the ER falls within the range of ERs reported for the flaming (0.0030) and smouldering phases (0.0055) of savanna fires. Non-methane hydrocarbon (NMHC) data obtained from a grab sample collected during the plume event were compared to background levels. The highest ERs (ΔNMHC/ΔCH 4) have been obtained for the C 2–C 3 hydrocarbons (e.g. ethene at 229.3 ppt ppb −1), whilst the C 4–C 7 hydrocarbons were characterised by the lowest ERs (e.g. n-hexane at 1.0 and n-pentane at 0.8 ppt ppb −1). 相似文献
15.
The present study was conducted within the framework of R&D activities on the development of gasification and reforming technologies for energy and chemical recovery from biomass resources. Gasification of the Japanese cedar wood has been investigated under various operating conditions in a bench-scale externally heated updraft gasifier; this was followed by thermal reforming. Parametric tests by varying the residence times, gasification temperatures, equivalence ratios (ERs) and steam-to-carbon (S/C) ratios were performed to determine their effects on the product gas characteristics. Thermodynamic equilibrium calculations were preformed to predict the equilibrium gas composition and compared with the experimental value.We found that the product gas characteristics in terms of the H 2/CO ratio, CO 2/CO ratio, and CH 4 and lighter hydrocarbons concentrations are significantly affected by the operating conditions used. Increasing the residence time decreased the CO 2/CO ratio; however, a nominal effect was noticed on H 2 concentration as a function of the residence time. At sufficient residence time, increasing the temperature led to higher H 2 yields, CO efficiency and higher heating value (HHV) of the product gas. The presence of steam during gasification effectively enhanced the proportion of H 2 in the product gas. However, higher S/C ratio reduced the HHV of the product gas. Increasing the ER from 0 to 0.3 increased the H 2 yields and CO efficiency and decreased the HHV of the product gas.The evolution of CH 4 and lighter hydrocarbons at low gasification temperatures was relatively higher than that at high temperature gasification. The evolution of CH 4 and lighter hydrocarbons at high gasification temperatures hardly varied over the investigated operating conditions. 相似文献
16.
Many farms have unroofed concrete yards used by livestock. These concrete yards have received little attention as sources of gaseous emissions. From 1997 to 1999 measurements were made of emissions of ammonia (NH 3), nitrous oxide (N 2O) and methane (CH 4) from 11 concrete yards used by livestock. A postal survey was carried out to assess the areas of yards on farms in England and Wales to enable the measurements to be scaled up to estimate national emissions. Using the results of this study NH 3-N emissions from farm concrete yards were calculated to be ca. 35×10 3 t annually. This is 13% of the current estimated total NH 3-N emission from UK livestock. Concrete yards were an insignificant source of N 2O and CH 4 which were both <0.01% of current estimates of agricultural emissions. 相似文献
17.
The effects of ammonia (NH 3) on CH 4 attenuation in landfill cover materials consisting of landfill cover soil (LCS) and aged municipal solid waste (AMSW), at different CH 4 concentrations, were investigated. The CH 4 oxidation capacities of LCS and AMSW were found to be significantly affected by the CH 4 concentration. The maximum oxidation rates for LCS and AMSW were obtained at CH 4 concentrations of 5 % and 20 %( v/v), respectively, within 20 days. CH 4 biological oxidation in AMSW was significantly inhibited by NH 3 at low CH 4 concentrations (5 %, v/v) but highly stimulated at high levels (20 % and 50 %, v/v). Oxidation in LCS was stimulated by NH 3 at all CH 4 concentrations due to the higher conversion of the nitrogen in NH 3 in AMSW than in LCS. NH 3 increases CH 4 oxidation in landfill cover materials. 相似文献
18.
Acetaldehyde (CH 3CHO) and acetone (CH 3C(O)CH 3) concentrations in ambient air, in snowpack air, and bulk snow were determined at Alert, Nunavut, Canada, as a part of the Polar Sunrise Experiment (PSE): ALERT 2000. During the period of continuous sunlight, vertical profiles of ambient and snowpack air exhibited large concentration gradients through the top ∼10 cm of the snowpack, implying a flux of carbonyl compounds from the surface to the atmosphere. From vertical profile and eddy diffusivity measurements made simultaneously on 22 April, acetaldehyde and acetone fluxes of 4.2(±2.1)×10 8 and 6.2(±4.2)×10 8 molecules cm −2 s −1 were derived, respectively. For this day, the sources and sinks of CH 3CHO from gas phase chemistry were estimated. The result showed that the snowpack flux of CH 3CHO to the atmosphere was as large as the calculated CH 3CHO loss rate from known atmospheric gas phase reactions, and at least 40 times larger (in the surface layer) than the volumetric rate of acetaldehyde produced from the assumed main atmospheric gas phase reaction, i.e. reaction of ethane with hydroxyl radicals. In addition, acetaldehyde bulk snow phase measurements showed that acetaldehyde was produced in or on the snow phase, likely from a photochemical origin. The time series for the observed CH 3C(O)CH 3, ozone (O 3), and propane during PSE 1995, PSE 1998, and ALERT 2000 showed a consistent anti-correlation between acetone and O 3 and between acetone and propane. However, our data and model simulations showed that the acetone increase during ozone depletion events cannot be explained by gas phase chemistry involving propane oxidation. These results suggest that the snowpack is a significant source of acetaldehyde and acetone to the Arctic boundary layer. 相似文献
19.
Rice hulls are widely burnt in agricultural fields in Asia because it is difficult to find other uses for them. Farmers burn rice hulls usually under incomplete combustion conditions to avoid accidental fires. In this study we investigated carbon gas emissions from rice hull fires at controlled wind speeds in a wind tunnel to clarify the effect of wind on such fires. Burning of the rice hulls resulted in relatively incomplete combustion: the ratio of [CO] to [CO 2] was high, >0.2, except when burning occurred at high wind speeds. Distinct differences in the carbon ratios of emitted carbon gases (CO 2, CO, CH 4, and nonmethane volatile organic compounds [NMVOC]) were found between high and low wind speeds: at high wind speeds, flames were usually present, and the CO 2 contribution to total carbon gases was higher; at low wind speeds, the NMVOC and CH 4 contributions to total carbon gases were greater. Therefore, a compensatory relationship existed between NMVOC and CH 4 and CO 2. Additionally, the ratio of [consumed O 2] to [CO 2] was <1 during the smoldering phase of combustion and >1 during the charcoal phase, synchronous with changes in [CH 4] and [NMVOC]. 相似文献
20.
We measured toxic air pollutants along Oba Akran road in Lagos to evaluate pedestrian exposure. PM 10, CO, O 3, NO 2, SO 2, CH 4, noise, wind velocity and temperature were measured simultaneously with portable analyzers. Our results showed that pedestrian exposure to PM 10 (with an average of 274.6 μg m −3 for all samples) and CO (with an average of 19.27 ppm for all samples) was relatively high. CO is a traffic-related pollutant, so the influence of the local traffic emissions on CO levels is strong. The high concentration of the PM 10 measured at the three environments also suggests that the traffic is a major source of ultrafine particles. The overall average concentrations for the 72-day experimental period for SO 2, NO 2 and O 3 are 101.2, 62.5 and 0.32 ppb respectively, all of which are below the US national ambient air quality standards. Strong traffic impacts can be observed from the concentrations of some of these pollutants measured in these three environments. Most clear is a reflection of diesel truck traffic activity rich in black carbon concentrations. The diurnal variation of O 3 and NO 2 also showed that NO 2 was depleted by photochemically formed O 3 during the day and replenished at night as O 3 was destroyed. A multivariate statistical analysis (Principal Component Analysis, Factor Analysis) has been applied to a set of data in order to determine the contribution of different sources. It was found that the main principal components, extracted from the air pollution data, were related to gasoline combustion, oil combustion and ozone interactions. 相似文献
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