A passive flux denuder for evaluating emissions of ammonia at a dairy farm

Passive samplers have been shown to be an inexpensive alternative to direct sampling. Diffusion denuders have been developed to measure the concentration of species such as ammonia (NH3), which is in equilibrium with particulate ammonium nitrate. Conventional denuder sampling has required active sampling that inherently requires air pumps and, therefore, electrical power. To estimate emissions of NH3 from a fugitive source would require an array of active samplers and meteorological measurements to estimate the flux. A recently developed fabric denuder was configured in an open tube to passively sample NH3 flux. Passive and active samplers were collocated at a dairy farm at the California State University, Fresno, Agricultural Research Facility. During this comparison study, NH3 flux measurements were made at the dairy farm lagoon before and after the lagoon underwent acidification. Comparisons were made of the flux measurements obtained directly from the passive flux denuder and those calculated from an active filter pack sampler and wind velocity. The results show significant correlation between the two methods, although a correction factor needed to be applied to directly compare the two techniques. This passive sampling approach significantly reduces the cost and complexity of sampling and has the potential to economically develop a larger inventory base for ambient NH3 emissions.     

A Passive Flux Denuder for Evaluating Emissions of Ammonia at a Dairy Farm

Abstract

Passive samplers have been shown to be an inexpensive alternative to direct sampling. Diffusion denuders have been developed to measure the concentration of species such as ammonia (NH₃), which is in equilibrium with particulate ammonium nitrate. Conventional denuder sampling that inherently requires air pumps and, therefore, electrical power. To estimate emissions of NH₃ from a fugitive source would require an array of active samplers and meteorological measurements to estimate the flux. A recently developed fabric denuder was configured in an open tube to passively sample NH₃ flux. Passive and active samplers were collocated at a dairy farm at the California State University, Fresno, Agricultural Research Facility. During this comparison study, NH₃ flux measurements were made at the dairy farm lagoon before and after the lagoon underwent acidification. Comparisons were made of the flux measurements obtained directly from the passive flux denuder and those calculated from an active filter pack sampler and wind velocity. The results show significant correlation between the two methods, although a correction factor needed to be applied to directly compare the two techniques. This passive sampling approach significantly reduces the cost and complexity of sampling and has the potential to economically develop a larger inventory base for ambient NH₃ emissions.     

Ammonia emission from grassland and livestock production systems in the UK

Emissions of ammonia were measured from livestock excreta and fertilisers applied to grass swards, from grazed paddocks, from decomposing grass herbage and from an animal house containing dairy cows. Emissions from urine, dung, slurry and fertilisers were determined using a system of wind tunnels with each tunnel covering an area of 1 m(2). Emissions from grazed swards were determined using a micrometeorological mass balance method. From the results of these measurements, together with other published information, an inventory for ammonia emissions has been calculated for grassland and livestock production systems over the UK as a whole. It is estimated that emissions from grassland and cattle and sheep production amount to about 230 kt NH(3)-N annually, while emissions from pig and poultry production amount to about 40 kt and 80 kt NH(3)-N, respectively.     

Field evaluation of the equilibrium concentration technique (JTI method) for measuring ammonia emission from land spread manure or fertiliser

Three experiments were conducted in which intercomparisons were made between the equilibrium concentration technique, developed at JTI, Sweden, and the integrated horizontal flux technique for measuring ammonia emissions following applications of urea fertiliser, cattle slurry and solid pig manure to land. Mean square prediction error analysis was used to compare the emission rates measured by the two techniques. There were no significant differences between the measurement techniques, although there was some evidence that emission rates were overestimated by the equilibrium concentration method relative to the integrated horizontal flux technique at higher emission rates (>400 g.N ha⁻¹ h⁻¹). The equilibrium concentration method provides a practical and relatively inexpensive technique for measuring emissions under ambient conditions from small plots but good sampler preparation, adequate replication of emission measurements and appropriate choice of duration of sampling periods are necessities for obtaining reliable results.     

Seasonal and spatial variations of ammonia emissions from an open-lot dairy operation

There is a need for a robust and accurate technique to measure ammonia (NH3) emissions from animal feeding operations (AFOs) to obtain emission inventories and to develop abatement strategies. Two consecutive seasonal studies were conducted to measure NH3 emissions from an open-lot dairy in central Texas in July and December of 2005. Data including NH3 concentrations were collected and NH3 emission fluxes (EFls), emission rates (ERs), and emission factors (EFs) were calculated for the open-lot dairy. A protocol using flux chambers (FCs) was used to determine these NH3 emissions from the open-lot dairy. NH3 concentration measurements were made using chemiluminescence-based analyzers. The ground-level area sources (GLAS) including open lots (cows on earthen corrals), separated solids, primary and secondary lagoons, and milking parlors were sampled to estimate NH3 emissions. The seasonal NH3 EFs were 11.6 +/- 7.1 kg-NH3 yr(-1)head(-1) for the summer and 6.2 +/- 3.7 kg-NH3 yr(-1)head(-1) for the winter season. The estimated annual NH3 EF was 9.4 +/- 5.7 kg-NH3 yr(-1)head(-1) for this open-lot dairy. The estimated NH3 EF for winter was nearly 47% lower than summer EF. Primary and secondary lagoons (approximately 37) and open-lot corrals (approximately 63%) in summer, and open-lot corrals (approximately 95%) in winter were the highest contributors to NH3 emissions for the open-lot dairy. These EF estimates using the FC protocol and real-time analyzer were lower than many previously reported EFs estimated based on nitrogen mass balance and nitrogen content in manure. The difference between the overall emissions from each season was due to ambient temperature variations and loading rates of manure on GLAS. There was spatial variation of NH3 emission from the open-lot earthen corrals due to variable animal density within feeding and shaded and dry divisions of the open lot. This spatial variability was attributed to dispirit manure loading within these areas.     

Intercalibration of a passive wind-vane flux sampler against a continuous-flow denuder for the measurements of atmospheric ammonia concentrations and surface exchange fluxes

A passive wind-vane flux sampler is a simple low-cost device used to estimate long-term vertical fluxes of ammonia in the atmospheric surface boundary layer. The passive flux sampler measures the horizontal flux of ammonia. A vertical gradient of the horizontal flux, combined with micro-meteorological measurements of wind speed and temperature, is used to estimated the vertical flux of ammonia using a modified aerodynamic gradient technique. The passive wind-vane flux sampler gradient was calibrated against a gradient measured with fast response (6 min) continuous-flow denuders. The measurements were carried out at a heathland located in an intensive farming area in the centre of the Netherlands. A field campaign took place over 70 day period in the summer of 1996, during which the sampling periods of the passive wind-vane flux sampler varied between 3 and 9 days. The comparison clearly showed that the long-term measurements with the passive wind-vane flux samplers gave accurate average ammonia deposition values for the field campaign as a whole which deviated by only 18% from the reference flux. However, there was no significant correlation between the fluxes from the passive samplers and the reference method for the individual 10 periods which were compared. Possible explanations found for the lacking correlation were (I) a high percentage number of half-hour emission events within each period resulted in a significant large relative deviation between the fluxes, and (II) uncertainties in the reference method might also explain the lacking correlation. The passive wind-vane flux samplers proved to be a stable method for long-term measurements (months to years) due to a close to 100% optimal functioning during the field campaign.     

Lagrangian dispersion modeling of vehicular emissions from a highway in complex terrain

Transit traffic through the Austrian Alps is of major concern in government policy. Pollutant burdens resulting from such traffic are discussed widely in Austrian politics and have already led to measures to restrict traffic on transit routes. In the course of an environmental assessment study, comprehensive measurements were performed. These included air quality observations using passive samplers, a differential optical absorption spectroscopy system, a mobile and a fixed air quality monitoring station, and meteorological observations. As was evident from several previous studies, dispersion modeling in such areas of complex terrain and, moreover, with frequent calm wind conditions, is difficult to handle. Further, in the case presented here, different pollutant sources had to be treated simultaneously (e.g., road networks, exhaust chimneys from road tunnels, and road tunnel portals). No appropriate system for modeling all these factors has so far appeared in the literature. A prognostic wind field model coupled with a Lagrangian dispersion model is thus presented here and is designed to treat all these factors. A comparison of the modeling system with results from passive samplers and from a fixed air quality monitoring station proved the ability of the model to provide reasonable figures for concentration distributions along the A10.     

Lagrangian Dispersion Modeling of Vehicular Emissions from a Highway in Complex Terrain

Abstract

Transit traffic through the Austrian Alps is of major concern in government policy. Pollutant burdens resulting from such traffic are discussed widely in Austrian politics and have already led to measures to restrict traffic on transit routes. In the course of an environmental assessment study, comprehensive measurements were performed. These included air quality observations using passive samplers, a differential optical absorption spectroscopy system, a mobile and a fixed air quality monitoring station, and meteorological observations. As was evident from several previous studies, dispersion modeling in such areas of complex terrain and, moreover, with frequent calm wind conditions, is difficult to handle. Further, in the case presented here, different pollutant sources had to be treated simultaneously (e.g., road networks, exhaust chimneys from road tunnels, and road tunnel portals). No appropriate system for modeling all these factors has so far appeared in the literature. A prognostic wind field model coupled with a Lagrangian dispersion model is thus presented here and is designed to treat all these factors. A comparison of the modeling system with results from passive samplers and from a fixed air quality monitoring station proved the ability of the model to provide reasonable figures for concentration distributions along the A10.     

Overview and assessment of techniques to measure ammonia emissions from animal houses: the case of the Netherlands

In order to comply with the ammonia (NH(3)) emission reduction assigned to the Netherlands development of new measures are needed, which should be supported by fast and accurate measurements to arrive at new estimates of the NH(3) emission from each agricultural source. This paper gives an overview of the current methods used in the Netherlands to measure NH(3) emissions from animal houses, and provides alternative methods for some particular situations. For mechanically ventilated animal houses, passive flux samplers placed in the ventilation shafts of the animal house are presented as alternative to measure a larger number of animal houses (replicates) with the same housing system at a low price. For naturally ventilated animal houses, when mixing in the animal house is not good enough to allow measurements within the animal house (internal tracer gas ratio method), two measurement methods are discussed: the Gaussian plume dispersion model, which is usually not suitable for agricultural situations, and the flux frame method, which is not always applicable because of distortion of the flow around the building. Finally, for animal houses with outside yards for the animals, there are at this moment no methods available to measure the NH(3) emissions from these complex situations, although quick box methods (for the outside yards) and a combination of a backward Lagrangian stochastic model with open-path concentration measurements with a tunable diode laser (TDL), look promising.     

Passive sampler for PM10-2.5 aerosol

This study investigates the use of a small passive sampler for aerosol particles to determine particulate matter (PM)10-2.5 concentrations in outdoor air. The passive sampler collects particles by gravity, diffusion, and convective diffusion onto a glass coverslip that is then examined with an optical microscope; digital images are processed with free software and the resultant PM10-2.5 concentrations determined. Both the samplers and the analyses are relatively inexpensive. Passive samplers were collocated with Federal Reference Method (FRM) samplers in Chapel Hill, NC; Phoenix, AZ; and Birmingham, AL; for periods from 5 to 15 days. Particles consisted primarily of inorganic dusts at some sites and a mix of industrial and inorganic materials at other sites. Measured concentrations ranged from < 10 microg/m3 to approximately 40 microg/m3. Overall, PM10-2.5 concentrations measured with the passive samplers were within approximately 1 standard deviation of concentrations measured with the FRM samplers. Concentrations determined with passive samplers depend on assumptions about particle density and shape factors and may also depend somewhat on local wind speed and turbulence; accurate values for these parameters may not be known. The degree of agreement between passive and FRM concentrations measured here suggests that passive measurements may not be overly dependent on accurate knowledge of these parameters.     

Rate of pesticide volatilization from soil: an experimental approach with a wind tunnel system applied to trifluralin

Pesticide volatilization to the atmosphere may be a major pathway of dissipation closely linked with environmental, physico-chemical and technical factors. Understanding the volatilization process requires systems that make it possible to control some of these factors. Wind tunnels meet to these criteria. The volatilization flux is determined from a mass balance, using the difference in atmospheric pesticide concentration between the entrance and the exit of the tunnel and the airflow rate. An experiment was carried out in June 2000 to study the repeatability of this technique. Volatilization of trifluralin was measured in three wind tunnels for 8 days with a sampling period varying between 3 h and 2 days. Pesticide concentration was determined by trapping by XAD-2 resin in a two-stage cartridge, solvent extraction and analysis by gas chromatography. Cumulated losses through volatilization reached 30% of the measured application dose after 8 days, with a variability of less than 20% between the three tunnels. Approximately 20% remained in the topsoil (0–2 cm), with a variability of 14% between the three tunnels. The decrease in the volatilization flux over time is coherent with the expected theoretical evolution for a volatile pesticide such as trifluralin and with previous experimental works.     

Ammonia flux from open-lot dairies: development of measurement methodology and emission factors

Ammonia emissions contribute to the formation of secondary particulate matter (PM) and violations of the National Ambient Air Quality Standard. Ammonia mass concentration measurements were made in February 1999 upwind and downwind of an open-lot dairy in California, using a combination of active bubbler and passive filter samplers. Ammonia fluxes were calculated from concentrations measured at 2, 4, and 10 m above ground at three locations on the downwind edge of the dairy, using micrometeorological techniques. A new method was developed to interpolate fluxes at six additional locations from ammonia concentrations measured at a single height, providing measurements at sufficient spatial resolution along the downwind border of the dairy to account for the heterogeneity of the source. PM measured up- and downwind of the dairy demonstrated insignificant ammonium particle formation in the immediate vicinity of the dairy and negligible contribution of dissociated ammonium nitrate to measured ammonia concentrations. Ammonium nitrate concentrations measured downwind of the dairy ranged from 26 to 0.26 microg m(-3) and from 2 to 43% of total PM2.5 mass concentrations. Measured ammonia fluxes showed that liquid manure retention ponds represented relatively minor sources of ammonia in winter on the dairy studied. Ammonia emission factors derived from the measurements ranged from 19 to 143 g head(-1) day(-1), showing an increase with warmer, drier weather and a decrease with increased relative humidity and lower temperatures.     

Lichen biomonitoring of ammonia emission and nitrogen deposition around a pig stockfarm

Effects of high ammonia emissions and nitrogen deposition were investigated on lichens around a pig stockfarm (ca. 7,000 animals) in central Italy. Four sites were selected along a transect at 200, 400, 1000 and 2500 m from the stockfarm, the diversity of epiphytic lichens was measured and transplanted thalli of Xanthoria parietina and Flavoparmelia caperata exposed, together with passive NH3 (diffusion tubes) samplers. Ammonia dramatically decreased from the centre of the stockfarm to the sampled sites, where it was correlated with bark pH. Total lichen diversity was not associated with either NH3 concentrations or bark pH, but the diversity of strictly nitrophytic species was highly correlated with both parameters. Physconia grisea was the best indicator species for NH3 pollution. Total N accumulated in X. parietina and F. caperata was correlated with NH3 concentrations.     

Ammonia Flux from Open-Lot Dairies: Development of Measurement Methodology and Emission Factors

Abstract

Ammonia emissions contribute to the formation of secondary particulate matter (PM) and violations of the National Ambient Air Quality Standard. Ammonia mass concentration measurements were made in February 1999 upwind and downwind of an open-lot dairy in California, using a combination of active bubbler and passive filter samplers. Ammonia fluxes were calculated from concentrations measured at 2, 4, and 10 m above ground at three locations on the downwind edge of the dairy, using micrometeorological techniques. A new method was developed to interpolate fluxes at six additional locations from ammonia concentrations measured at a single height, providing measurements at sufficient spatial resolution along the downwind border of the dairy to account for the heterogeneity of the source. PM measured up- and downwind of the dairy demonstrated insignificant ammonium particle formation in the immediate vicinity of the dairy and negligible contribution of dissociated ammonium nitrate to measured ammonia concentrations. Ammonium nitrate concentrations measured downwind of the dairy ranged from 26 to 0.26 μg m^?3 and from 2 to 43% of total PM_2.5 mass concentrations. Measured ammonia fluxes showed that liquid manure retention ponds represented relatively minor sources of ammonia in winter on the dairy studied. Ammonia emission factors derived from the measurements ranged from 19 to 143 g head^?1 day^?1, showing an increase with warmer, drier weather and a decrease with increased relative humidity and lower temperatures.     

Measuring Ammonia Concentrations and Emissions from Agricultural Land and Liquid Surfaces: A Review

Abstract

Aerial ammonia concentrations (C _g) are measured using acid scrubbers, filter packs, denuders, or optical methods. Using C _g and wind speed or airflow rate, ammonia emission rate or flux can be directly estimated using enclosures or micrometeorological methods. Using nitrogen (N) recovery is not recommended, mainly because the different gaseous N components cannot be separated. Although low cost and replicable, chambers modify environmental conditions and are suitable only for comparing treatments. Wind tunnels do not modify environmental conditions as much as chambers, but they may not be appropriate for determining ammonia fluxes; however, they can be used to compare emissions and test models. Larger wind tunnels that also simulate natural wind profiles may be more useful for comparing treatments than micrometeorological methods because the latter require larger plots and are, thus, difficult to replicate. For determining absolute ammonia flux, the micrometeorological methods are the most suitable because they are nonintrusive. For use with micrometeorological methods, both the passive denuders and optical methods give comparable accuracies, although the latter give real-time C _g but at a higher cost. The passive denuder is wind weighted and also costs less than forced-air C _g measurement methods, but it requires calibration. When ammonia contamination during sample preparation and handling is a concern and separating the gas-phase ammonia and aerosol ammonium is not required, the scrubber is preferred over the passive denuder. The photothermal interferometer, because of its low detection limit and robustness, may hold potential for use in agriculture, but it requires evaluation. With its simpler theoretical basis and fewer restrictions, the integrated horizontal flux (IHF) method is preferable over other micrometeorological methods, particularly for lagoons, where berms and land-lagoon boundaries modify wind flow and flux gradients. With uniform wind flow, the ZINST method requiring measurement at one predetermined height may perform comparably to the IHF method but at a lower cost.     

Partitioning of organochlorine pesticides from water to polyethylene passive samplers

The mass transfer rates and equilibrium partitioning behaviour of 14 diverse organochlorine pesticides (OCP) between water and polyethylene (PE) passive samplers, cut from custom made PE sheets and commercial polyethylene plastic bags, were quantified. Overall mass transfer coefficients, k_O, estimated PE membrane diffusion coefficients, D_PE, and PE-water partitioning coefficients, K_PE-water, are reported. In addition, the partitioning of three polycyclic aromatic hydrocarbons (PAHs) from water to PE is quantified and compared with literature values. K_PE-water values agreed mostly within a factor of two for both passive samplers and also with literature values for the reference PAHs. As PE is expected to exhibit similar sorption behaviour to long-chain alkanes, PE-water partitioning coefficients were compared to hexadecane-water partitioning coefficients estimated with the SPARC online calculator, COSMOtherm and a polyparameter linear free energy relationship based on the Abraham approach. The best correlation for all compounds tested was with COSMOtherm estimated hexadecane-water partitioning coefficients.     

Methods of investigating urban wind fields—physical models

For evaluation of environmental problems in urban areas, models are needed. Physical models and mathematical models are the tools of the trade. Both types of models have advantages and limitations. The emphasis here is on boundary layer wind tunnels, which are well suited for the study of many urban climate situations. The boundary layer flow along the floor of a meteorological wind tunnel is a real flow which approximately represents a scaled down version of the atmospheric boundary layer under conditions of neutral stratification. Therefore, important practical problems involving urban atmospheric conditions can be studied in such wind tunnels by means of geometrically similar models of the urban area. Such problems involve wind forces on structures, pedestrian comfort, and diffusion processes from point sources, such as chimneys, tunnel exhausts and gaseous spills, or from line sources, such as traffic lines. The investigation of these processes in a wind tunnel must be seen, however, as one link only in a chain of actions.     

Managing ammonia emissions from livestock production in Europe

Around 75% of European ammonia (NH(3)) emissions come from livestock production. Emissions occur at all stages of manure management: from buildings housing livestock; during manure storage; following manure application to land; and from urine deposited by livestock on pastures during grazing. Ammoniacal nitrogen (total ammoniacal-nitrogen, TAN) in livestock excreta is the main source of NH(3). At each stage of manure management TAN may be lost, mainly as NH(3), and the remainder passed to the next stage. Hence, measures to reduce NH(3) emissions at the various stages of manure management are interdependent, and the accumulative reduction achieved by combinations of measures is not simply additive. This TAN-flow concept enables rapid and easy estimation of the consequences of NH(3) abatement at one stage of manure management (upstream) on NH(3) emissions at later stages (downstream), and gives unbiased assessment of the most cost-effective measures. We conclude that rapid incorporation of manures into arable land is one of the most cost-effective measures to reduce NH(3) emissions, while covering manure stores and applying slurry by band spreader or injection are more cost-effective than measures to reduce emissions from buildings. These measures are likely to rank highly in most European countries.     

Measuring ammonia concentrations and emissions from agricultural land and liquid surfaces: a review

Aerial ammonia concentrations (Cg) are measured using acid scrubbers, filter packs, denuders, or optical methods. Using Cg and wind speed or airflow rate, ammonia emission rate or flux can be directly estimated using enclosures or micrometeorological methods. Using nitrogen (N) recovery is not recommended, mainly because the different gaseous N components cannot be separated. Although low cost and replicable, chambers modify environmental conditions and are suitable only for comparing treatments. Wind tunnels do not modify environmental conditions as much as chambers, but they may not be appropriate for determining ammonia fluxes; however, they can be used to compare emissions and test models. Larger wind tunnels that also simulate natural wind profiles may be more useful for comparing treatments than micrometeorological methods because the latter require larger plots and are, thus, difficult to replicate. For determining absolute ammonia flux, the micrometeorological methods are the most suitable because they are nonintrusive. For use with micrometeorological methods, both the passive denuders and optical methods give comparable accuracies, although the latter give real-time Cg but at a higher cost. The passive denuder is wind weighted and also costs less than forced-air Cg measurement methods, but it requires calibration. When ammonia contamination during sample preparation and handling is a concern and separating the gas-phase ammonia and aerosol ammonium is not required, the scrubber is preferred over the passive denuder. The photothermal interferometer, because of its low detection limit and robustness, may hold potential for use in agriculture, but it requires evaluation. With its simpler theoretical basis and fewer restrictions, the integrated horizontal flux (IHF) method is preferable over other micrometeorological methods, particularly for lagoons, where berms and land-lagoon boundaries modify wind flow and flux gradients. With uniform wind flow, the ZINST method requiring measurement at one predetermined height may perform comparably to the IHF method but at a lower cost.     

Comparison of Analytical Techniques for Measuring Hydrocarbon Emissions from the Manufacture of Fiberglass-Reinforced Plastics

ABSTRACT

Research Triangle Institute and the U.S. Environmental Protection Agency conducted several projects to measure hydrocarbon emissions associated with the manufacture of fiberglass-reinforced plastics. The purpose of these projects was to evaluate pollution prevention techniques to reduce emissions by altering raw materials, application equipment, and operator technique. Analytical techniques were developed to reduce the cost of these emission measurements. Emissions from a small test mold in a temporary total enclosure (TTE) correlated with emissions from full-size production molds in a separate TTE. Gravimetric mass balance measurements inside the TTE generally agreed to within ± 30 % with total hydrocarbon (THC) measurements in the TTE exhaust duct. Pure styrene evaporation tests served as quality control checks for THC measurements and generally agreed to within ± 5 %.