Removal of sulphur dioxide from exhaust gases using hazardous and structured packing

The expulsion of sulphur dioxide from hydrocarbon combustion can reach levels higher than accepted by the normative. In order to evaluate the efficiency of separation of SO₂ by different packing systems constructed with materials such as metals or ceramics, the mass transfer and hydrodynamic parameters were evaluated. With the use of mass transfer model, the ININ packing showed higher separation efficiency with respect to Sulzer BX, Mellapak, and Raschig packing: 33.74%, 45.43% and 61.32%, respectively. These results were because the ININ packing has lower corrugation angles and narrower corrugated side than the others. The present work quantifies the improvements in mass transfer, like mass transfer volumetric coefficient and the height of the transfer global units in gas and liquid phase per each packing, using absorption columns with different gas flow managed: 5,000, 4,000 and 3,000 Nm3/h. The hydrodynamic model was used to design the column, as well as to determine the diameter or the cross area of the column per each packing. It is discussed that the ININ packing was one of the best of those tested because it has the highest separation efficiency with the least height of the transfer global units.     

Evolution of vehicle exhaust particles in the atmosphere

Aerosol mass spectrometer (AMS) measurements are used to characterize the evolution of exhaust particulate matter (PM) properties near and downwind of vehicle sources. The AMS provides time-resolved chemically speciated mass loadings and mass-weighted size distributions of nonrefractory PM smaller than 1 microm (NRPM1). Source measurements of aircraft PM show that black carbon particles inhibit nucleation by serving as condensation sinks for the volatile and semi-volatile exhaust gases. Real-world source measurements of ground vehicle PM are obtained by deploying an AMS aboard a mobile laboratory. Characteristic features of the exhaust PM chemical composition and size distribution are discussed. PM mass and number concentrations are used with above-background gas-phase carbon dioxide (CO2) concentrations to calculate on-road emission factors for individual vehicles. Highly variable ratios between particle number and mass concentrations are observed for individual vehicles. NRPM1 mass emission factors measured for on-road diesel vehicles are approximately 50% lower than those from dynamometer studies. Factor analysis of AMS data (FA-AMS) is applied for the first time to map variations in exhaust PM mass downwind of a highway. In this study, above-background vehicle PM concentrations are highest close to the highway and decrease by a factor of 2 by 200 m away from the highway. Comparison with the gas-phase CO2 concentrations indicates that these vehicle PM mass gradients are largely driven by dilution. Secondary aerosol species do not show a similar gradient in absolute mass concentrations; thus, their relative contribution to total ambient PM mass concentrations increases as a function of distance from the highway. FA-AMS of single particle and ensemble data at an urban receptor site shows that condensation of these secondary aerosol species onto vehicle exhaust particles results in spatial and temporal evolution of the size and composition of vehicle exhaust PM on urban and regional scales.     

Carbonaceous species in fine particles at the background sites in Korea between 1994 and 1999

Organic carbon (OC) and elemental carbon (EC) in fine particles (PM_2.5) at two background sites, Kosan and Kangwha in Korea were measured during intensive field studies between 1994 and 1999. Fine particles were collected on pre-fired quartz filters in a low-volume sampler and analyzed using the selective thermal oxidation method with MnO₂ catalyst. The OC and EC concentrations at Kosan located at western tip of Cheju Island in southern Korea are lower than those at Kangwha located at western coastal area in mid-Korean peninsula. Still, the OC concentrations at Kosan are generally higher than those at other background areas in Japan and USA. The EC concentrations at Kosan are lower than or comparable to those at other background areas. The total carbon (TC, sum of OC and EC) to EC ratio values at both sites were higher than those at other background areas in Japan and USA. At Kosan, the OC and EC concentrations when air parcels were from southern China were higher than those when air parcels were coming from northern China. However, at Kangwha, the differences were statistically not clear since most air parcels were from northern China. Except when air parcels were from the North Pacific during summer, the OC and EC concentrations are well correlated indicating that both OC and EC share the same emission/transport characteristics. From the gaseous hydrocarbon data and the OC and EC relationship, it was found that during summer local biogenic emissions of OC might be significant at Kosan.     

Observed chemical characteristics of long-range transported particles at a marine background site in Korea

Deokjeok Island is located off the west coast of the Korean Peninsula and is a suitable place to monitor the long-range transport of air pollutants from the Asian continent. In addition to pollutants, Asian dust particles are also transported to the island during long-range transport events. Episodic transport of dust and secondary particles was observed during intensive measurements in the spring (March 31-April 11) and fall (October 13-26) of 2009. In this study, the chemical characteristics of long-range-transported particles were investigated based on highly time-resolved ionic measurements with a particle-into-liquid system coupled with an online ion chromatograph (PILS-IC) that simultaneously measures concentrations of cations (Li+, Na , NH4+, K+, Ca2+, Mg2+) and anions (F-, C1-, NO3-, SO42-). The aerosol optical thickness (AOT) distribution retrieved by the modified Bremen Aerosol Retrieval (M-BAER) algorithm from moderate resolution imaging spectroradiometer (MODIS) satellite data confirmed the presence of a thick aerosol plume coming from the Asian continent towards the Korean peninsula. Seven distinctive events involving the long-range transport (LRT) of aerosols were identified and studied, the chemical components of which were strongly related to sector sources. Enrichment of acidic secondary aerosols on mineral dust particles, and even of sea-salt components, during transport was observed in this study. Backward trajectory, chemical analyses, and satellite aerosol retrievals identified two distinct events: a distinctively high [Ca2++Mg2]/[Na+] ratio (>2.0), which was indicative of a preprocessed mineral dust transport event, and a low [Ca2++Mg2+]/[Na+] ratio (<2.0), which was indicative of severe aging of sea-salt components on the processed dust particles. Particulate C1- was depleted by up to 85% in spring and 50% in the fall. A consistent fraction of carbonate replacement (FCR) averaged 0.53 in spring and 0.55 in the fall. Supporting evidences of C1- enrichment on the marine boundary layer prior to a dust front were also found. Supplemental materials are available for this article. Go to the publisher's online edition of the Journal of the Air & Waste Management Association for sector and air mass classifications of clean and LRT cases.     

Isolation and identification of new vasodilative substances in diesel exhaust particles

Background, aim, and scope  

We recently developed a new isolation method for diesel exhaust particles (DEP), involving successive extraction with H₂O, sodium bicarbonate, and sodium hydroxide, in which the sodium hydroxide extract was found to consist of phenolic components. Analysis of the extract revealed that vasodilative-active nitrophenols are in DEP in significantly higher concentrations than those estimated by an earlier method involving a combination of solvent extraction and repeated chromatography. These findings indicated that our new procedure offers a simple, efficient, and reliable method for the isolation and identification of bioactive substances in DEP. This encouraged us to extend our work toward investigating new vasodilatory substances in the sodium bicarbonate extract.     

Sources and emission of greenhouse gases in Danube Delta lakes

Production of methane and carbon dioxide as well as methane concentrations in surface waters and emissions to the atmosphere were investigated in two flow-through lake complexes (Uzlina–Isac and Puiu–Rosu–Rosulet) in the Danube Delta during post-flood conditions in May and low water level in September 2006. Retained nutrients fuelled primary production and remineralisation of bioavailable organic matter. This led to an observable net release of methane, particularly in the lakes Uzlina, Puiu and Rosu in May. Input from the Danube River, from redbuds and benthic release contributed to CH₄ concentrations in surface waters. In addition to significant river input of CO₂, this trace gas was released via aerobic remineralisation within the water column and in top sediments. Emission patterns of CO₂ widely overlapped with those of CH₄. Generally, greenhouse gas emissions peaked in the lake complex adjacent to the Danube River in May due to strong winds and decreased with increasing hydrological distance from the Danube River. Intense remineralisation of organic matter in the Danube Delta lakes results in a net source of atmospheric greenhouse gases.     

Morphological and chemical composition characteristics of summertime atmospheric particles collected at Tokchok Island,Korea

Determination of the chemical compositions of atmospheric single particles in the Yellow Sea region is critical for evaluating the environmental impact caused by air pollutants emitted from mainland China and the Korean peninsula. After ambient aerosol particles were collected by the Dekati PM10 cascade impactor on July 17–23, 2007 at Tokchok Island (approximately 50 km west of the Korean coast nearby Seoul), Korea, overall 2000 particles (on stage 2 and 3 with cut-off diameters of 2.5–10 μm and 1.0–2.5 μm, respectively) in 10 samples were determined by using low-Z particle electron probe X-ray microanalysis. X-ray spectral and secondary electron image (SEI) data showed that soil-derived and sea-salt particles which had reacted or were mixed with SO₂ and NO_x (or their acidic products) outnumbered the primary and “genuine” ones (59.2% vs. 19.2% in the stage 2 fraction and 41.3% vs. 9.9% in the stage 3 fraction). Moreover, particles containing nitrate in the secondary soil-derived species greatly outnumbered those containing sulfate. Organic particles, mainly consisting of marine biogenic species, were more abundant in the stage 2 fraction than in the stage 3 fraction (11.6% vs. 5.1%). Their relative abundance was greater than the sum of carbon-rich, K-containing, Fe-containing, and fly ash particles, which exhibited low frequencies in all the samples. In addition, many droplets rich in C, N, O, and S were observed. They tended to be small, exhibiting a dark round shape on SEI, and generally included 8–20 at.% C, 0–12 at.% N, 60–80 at.% O, and 4–10 at.% S (sometimes with <3 at.% Mg and Na). They were attributed to be a mixture of carbonaceous matter, H₂SO₄, and NH₄HSO₄/(NH₄)₂SO₄, mostly from the reaction of atmospheric SO₂ with NH₃ under high relative humidity. The analysis of the relationship between the aerosol particle compositions and 72-h backward air-mass trajectories suggests that ambient aerosols at Tokchok Island are strongly affected not only by seawater from the Yellow Sea but also by anthropogenic pollutants emitted from China and the Seoul–Incheon metropolis, resulting in the dominance of complex secondary aerosol particles.     

Characterization of exhaust particles from military vehicles fueled with diesel,gasoline, and JP-8

Diluted exhaust from selected military aircraft ground-support equipment (AGE) was analyzed for particulate mass, elemental carbon (EC) and organic carbon (OC), SO4(2-), and size distributions. The experiments occurred at idle and load conditions and utilized a chassis dynamometer. The selected AGE vehicles operated on gasoline, diesel, and JP-8. These military vehicles exhibited concentrations, size distributions, and emission factors in the same range as those reported for nonmilitary vehicles. The diesel and JP-8 emission rates for PM ranged from 0.092 to 1.1 g/kg fuel. The EC contributed less and the OC contributed more to the particulate mass than reported in recent studies of vehicle emissions. Overall, the particle size distribution varied significantly with engine condition, with the number of accumulation mode particles and the count median diameter (CMD) increasing as engine load increased. The SO4(2-) analyses showed that the distribution of SO4(2-) mass mirrored the distribution of particle mass.     

Concentrations of carbon gases and oxygen and their emission ratios from the combustion of rice hulls in a wind tunnel

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 [CO₂] was high, >0.2, except when burning occurred at high wind speeds. Distinct differences in the carbon ratios of emitted carbon gases (CO₂, CO, CH₄, and nonmethane volatile organic compounds [NMVOC]) were found between high and low wind speeds: at high wind speeds, flames were usually present, and the CO₂ contribution to total carbon gases was higher; at low wind speeds, the NMVOC and CH₄ contributions to total carbon gases were greater. Therefore, a compensatory relationship existed between NMVOC and CH₄ and CO₂. Additionally, the ratio of [consumed O₂] to [CO₂] was <1 during the smoldering phase of combustion and >1 during the charcoal phase, synchronous with changes in [CH₄] and [NMVOC].     

National emissions inventory and future trends in greenhouse gases and other air pollutants from civil airports in China

Environmental Science and Pollution Research - Civil aviation is an important source of air pollutants, but this field has received insufficient attention in China. Based on the standard emissions...     

Enhancement of the daily performance of solar still by exhaust gases under hot and cold climate conditions

Environmental Science and Pollution Research - A study is presented on the enhancement of solar still (SS) performance by using chimney exhaust gases (EGs) passing through chimney channels under...     

Measured isoprene emission rates of plants in California landscapes: comparison to estimates from taxonomic relationships

Isoprene emission rates of 64 plant species found in California's urban and natural landscapes were measured using a dynamic flow-through chamber enclosure technique. Species were selected to provide data for previously unmeasured species and to test estimates of isoprene emission rates based upon taxonomic relationships developed for compilation of biogenic emission inventories as proposed by Benjamin et al. (1996, Atmospheric Environment 30, 1437–1452). Branch-level isoprene emission rates ranged from undetectable for 47 species, to 54 μg g⁻¹ h⁻¹ for Quercus kelloggii, California black oak. Isoprene emission rate estimates based on taxonomy agreed well with our measurements for species within the same genus, with the exception of the Quercus genus for which a wide range of isoprene emission rates have been reported. As expected, family-level estimates based on taxonomy showed greater deviation from our measured values than did genus-based estimates. The data developed in the present study support use of a taxonomic predictive methodology, especially if previous measurements within specific families, sub-families, and genera are extensive, and the results of such assignment are treated with proper caution. A taxonomic approach may be most useful where plant species in natural and urban landscapes are numerous, such as in California, where no experimental measurements are available for thousands of species.     

Current and future emissions of selected heavy metals to the atmosphere from anthropogenic sources in Europe

Current atmospheric emissions of As, Cd, Cr, Ni, and Pb (reference year 2000) from major anthropogenic sources in Europe are presented in this paper. Combustion of fuels in stationary sources was the main emission source for As, Cd, Cr, and Ni (more than a half of the total anthropogenic emissions), while combustion of gasoline was the main source of for lead. There is a continuous reduction of heavy metal emissions in Europe during the last 40 years. Better knowledge of heavy metal sources, emissions, pathways, and fate in the environment, and progress in developing efficient emission control equipment has resulted in more efficient regulatory efforts to curb heavy metal emissions from anthropogenic sources very substantially. There is a potential for further reduction of these emissions until the year 2010 up to about 40% for As, Cd, Cr, and Ni and about 57% for Pb, as estimated within various emission scenarios presented in the paper.     

Emissions of gases and particles from biomass burning during the 20th century using satellite data and an historical reconstruction

A new dataset of emissions of trace gases and particles resulting from biomass burning has been developed for the historical and the recent period (1900–2005). The purpose of this work is to provide a consistent gridded emissions dataset of atmospheric chemical species from 1900 to 2005 for chemistry-climate simulations. The inventory is built in two steps. First, fire emissions are estimated for the recent period (1997–2005) using satellite products (GBA2000 burnt areas and ATSR fire hotspots); the temporal and spatial distribution of the CO₂ emissions for the 1997–2005 period is estimated through a calibration of ATSR fire hotspots. The historical inventory, covering the 1900–2000 period on a decadal basis, is derived from the historical reconstruction of burned areas from Mouillot and Field (2005). The historical emissions estimates are forced, for each main ecosystem, to agree with the recent inventory estimates, ensuring consistency between past and recent emissions.The methodology used for estimating the fire emissions is discussed, together with the time evolution of biomass burning emissions during the 20th century, first at the global scale and then for specific regions. The results are compared with the distributions provided by other inventories and results of inverse modeling studies.     

Chemical composition and source apportionment of PM2.5 particles in the Sihwa area, Korea

To investigate the chemical characteristics of fine particles in the Sihwa area, Korea, atmospheric aerosol samples were collected using a dichotomous PM10 sampler and two URG PM2.5 cyclone samplers during five intensive sampling periods between February 1998 and February 1999. The Inductively Coupled Plasma (ICP)-Atomic Emission Spectrometry (AES)/ICP-Mass Spectrometry (MS), ion chromatograph (IC), and thermal manganese dioxide oxidation (TMO) methods were used to analyze the trace elements, ionic species, and carbonaceous species, respectively. Backward trajectory analysis, factor analysis, and a chemical mass balance (CMB) model were used to estimate quantitatively source contributions to PM2.5 particles collected in the Sihwa area. The results of PM2.5 source apportionment using the CMB7 receptor model showed that (NH4)2SO4 was, on average, the major contributor to PM2.5 particles, followed by nontraffic organic carbon (OC) emission, NH4NO3, agricultural waste burning, motor vehicle emission, road dust, waste incineration, marine aerosol, and others. Here, the nontraffic OC sources include primary anthropogenic OC emitted from the industrial complex zone, secondary OC, and organic species from distant sources. The source impact of waste incineration emission became significant when the dominant wind directions were from southwest and west sectors during the sampling periods. It was found that PM2.5 particles in the Sihwa area were influenced mainly by both anthropogenic local sources and long-range transport and transformation of air pollutants.     

The comparison of fossil carbon fraction and greenhouse gas emissions through an analysis of exhaust gases from urban solid waste incineration facilities

In this study, in order to understand accurate calculation of greenhouse gas emissions of urban solid waste incineration facilities, which are major waste incineration facilities, and problems likely to occur at this time, emissions were calculated by classifying calculation methods into 3 types. For the comparison of calculation methods, the waste characteristics ratio, dry substance content by waste characteristics, carbon content in dry substance, and ¹²C content were analyzed; and in particular, CO₂ concentration in incineration gases and ¹²C content were analyzed together. In this study, 3 types of calculation methods were made through the assay value, and by using each calculation method, emissions of urban solid waste incineration facilities were calculated then compared. As a result of comparison, with Calculation Method A, which used the default value as presented in the IPCC guidelines, greenhouse gas emissions were calculated for the urban solid waste incineration facilities A and B at 244.43 ton CO₂/day and 322.09 ton CO₂/day, respectively. Hence, it showed a lot of difference from Calculation Methods B and C, which used the assay value of this study. It is determined that this was because the default value as presented in IPCC, as the world average value, could not reflect the characteristics of urban solid waste incineration facilities. Calculation Method B indicated 163.31 ton CO₂/day and 230.34 ton CO₂/day respectively for the urban solid waste incineration facilities A and B; also, Calculation Method C indicated 151.79 ton CO₂/day and 218.99 ton CO₂/day, respectively.

Implications: This study intends to compare greenhouse gas emissions calculated using ¹²C content default value provided by the IPCC (Intergovernmental Panel on Climate Change) with greenhouse gas emissions calculated using ¹²C content and waste assay value that can reflect the characteristics of the target urban solid waste incineration facilities. Also, the concentration and ¹²C content were calculated by directly collecting incineration gases of the target urban solid waste incineration facilities, and greenhouse gas emissions of the target urban solid waste incineration facilities through this survey were compared with greenhouse gas emissions, which used the previously calculated assay value of solid waste.     

A study on the evaluations of emission factors and uncertainty ranges for methane and nitrous oxide from combined-cycle power plant in Korea

In this research, in order to develop technology/country-specific emission factors of methane (CH₄) and nitrous oxide (N₂O), a total of 585 samples from eight gas-fired turbine combined cycle (GTCC) power plants were measured and analyzed. The research found that the emission factor for CH₄ stood at “0.82 kg/TJ”, which was an 18 % lower than the emission factor for liquefied natural gas (LNG) GTCC “1 kg/TJ” presented by Intergovernmental Panel on Climate Change (IPCC). The result was 8 % up when compared with the emission factor of Japan which stands at “0.75 kg/TJ”. The emission factor for N₂O was “0.65 kg/TJ”, which is significantly lower than “3 kg/TJ” of the emission factor for LNG GTCC presented by IPCC, but over six times higher than the default N₂O emission factor of LNG. The evaluation of uncertainty was conducted based on the estimated non-CO₂ emission factors, and the ranges of uncertainty for CH₄ and N₂O were between ?12.96 and +13.89 %, and ?11.43 and +12.86 %, respectively, which is significantly lower than uncertainties presented by IPCC. These differences proved that non-CO₂ emissions can change depending on combustion technologies; therefore, it is vital to establish country/technology-specific emission factors.     

Historical and future emission of hazardous air pollutants (HAPs) from gas-fired combustion in Beijing,China

Environmental Science and Pollution Research - The consumption of natural gas in Beijing has increased in the past decade due to energy structure adjustments and air pollution abatement. In this...     

Monitoring of environmental contaminants in raw bovine milk and estimates of dietary intakes of children in South Korea

Persistent organic pollutants (POPs) are ubiquitous residual contaminants in the environment and in the food chain. Milk is an important matrix for monitoring POP contamination. This study determined the concentrations of POPs including polybrominated diphenyl ethers (PBDEs), hexachlorobenzene (HCB), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and dioxin-like polychlorinated biphenyls (DL-PCBs) in raw bovine milk, and the data was used to estimate dietary intakes in South Korea. The average concentrations of PBDEs, HCB, PCDD/Fs, and DL-PCBs in raw milk were 0.29 ng g⁻¹ fat, 0.50 ng g⁻¹ fat, 0.27 pg TEQ g⁻¹ fat, and 0.33 pg TEQ g⁻¹ fat, respectively. No significant relationship was found between the concentrations of analytes and the regions sampled. The dietary intakes of PBDEs from the consumption of milk was calculated to be 0.26, 0.10, and 0.05 ng kg⁻¹ bw d⁻¹ for the group of ages 0–6, 7–12, and 13–19, respectively. The dietary intakes of HCB was calculated to be 0.44, 0.16, and 0.09 ng kg⁻¹ bw d⁻¹ for the group of ages 0–6, 7–12, and 13–19, respectively. The dietary intakes of PCDD/Fs and DL-PCBs was calculated to be 0.78, 0.29, and 0.16 pg TEQ kg⁻¹ bw d⁻¹ for the group of ages 0–6, 7–12, and 13–19, respectively. These results indicated that the residual levels of PBDEs, HCB, PCDD/Fs, and DL-PCBs in raw bovine milk were within safe levels.     

Definition of yearly emission factor of dust and greenhouse gases through continuous measurements in swine husbandry

The object of this study was to develop an accurate estimation method to evaluate the contribution of the various compartments of swine husbandry to dust and GHG (greenhouse gases, CO₂, CH₄ and N₂O) emission into the atmosphere during one year of observation.A weaning, a gestation, a farrowing and a fattening room in an intensive pig house were observed in three different periods (Autumn–Winter, Springtime and Summer, monitoring at least 60% of each period (20% at the beginning, in the middle and at the end) of each cycle).During monitoring, live weight, average live weight gain, number of animals and its variation, type of feed and feeding time were taken into account to evaluate their influence on PM₁₀, or the fraction of suspended particulate matter with an aerodynamic diameter less than or equal to 10 μm [Emission Inventory Guidebook, 2007. B1100 Particle Emissions from Animal Husbandry Activities. Available from: <http://reports.eea.europa.eu/EMEPCORINAIR5/en/B1100vs1.pdf> (accessed October 2008)] and to define GHG emission.The selected piggery had a ventilation control system using a free running impeller to monitor continuously real-time environmental and management parameters with an accuracy of 5%.PM₁₀ concentration was monitored by a sampler (Haz Dust EPAM 5000), either continuously or through traditional gravimetric technique, and the mean value of dust amount collected on the membranes was utilized as a correction factor to be applied to continuously collected data.PM₁₀ concentration amount incoming from inlets was removed from PM₁₀ emission calculation, to estimate the real contribution of pig house dust pollution into atmosphere.Mean yearly emission factor of PM₁₀ was measured in 2 g d^?1 LU^?1 for the weaning room, 0.09 g d^?1 LU^?1 for the farrowing room, 2.59 g d^?1 LU^?1 for the fattening room and 1.23 g d^?1 LU^?1 for the gestation room. The highest PM₁₀ concentration and emission per LU was recorded in the fattening compartment while the lowest value was recorded in the farrowing room.CO₂, CH₄ and N₂O concentrations were continuously measured in the exhaust ducts using an infrared photoacoustic detector IPD (Brüel & Kjaer, Multi-gas Monitor Type 1302, Multipoint Sampler and Doser Type 1303) sampling data every 15 min, for the 60% of the cycles.Yearly emission factor for CO₂ was measured in 5997 g d^?1 LU^?1 for the weaning room, 1278 g d^?1 LU^?1 for the farrowing room, 13,636 g d^?1 LU^?1 for the fattening room and 8851 g d^?1 LU^?1 for the gestation room.Yearly emission factor for CH₄ was measured in 24.57 g d^?1 LU^?1 for the weaning room, 4.68 g d^?1 LU^?1 for the farrowing room, 189.82 g d^?1 LU^?1 for the fattening room and 132.12 g d^?1 LU^?1 for the gestation room.Yearly emission factor for N₂O was measured in 3.62 g d^?1 LU^?1 for the weaning room, 0.66 g d^?1 LU^?1 for the farrowing room, 3.26 g d^?1 LU^?1 for the fattening room and 2.72 g d^?1 LU^?1 for the gestation room.