Viney P. Aneja

Atmospheric nitrogen compounds II: emissions, transport, transformation, deposition and assessment

Abstract The Atmospheric Nitrogen Compounds II: Emissions, Transport, Transformation, Deposition and Assessment workshop was held in Chapel Hill, NC from 7 to 9 June 1999. This international conference, which served as a follow-up to the workshop held in March 1997, was sponsored by: North Carolina Department of Environment and Natural Resources; North Carolina Department of Health and Human Services, North Carolina Office of the State Health Director; Mid-Atlantic Regional Air Management Association; North Carolina Water Resources Research Institute; Air and Waste Management Association, RTP Chapter; the US Environmental Protection Agency and the North Carolina State University (College of Physical and Mathematical Sciences, and North Carolina Agricultural Research Service). The workshop was structured as an open forum at which scientists, policy makers, industry representatives and others could freely share current knowledge and ideas, and included international perspectives. The workshop commenced with international perspectives from the United States, Canada, United Kingdom, the Netherlands, and Denmark. This article summarizes the findings of the workshop and articulates future research needs and ways to address nitrogen/ammonia from intensively managed animal agriculture. The need for developing sustainable solutions for managing the animal waste problem is vital for shaping the future of North Carolina. As part of that process, all aspects of environmental issues (air, water, soil) must be addressed as part of a comprehensive and long-term strategy. There is an urgent need for North Carolina policy makers to create a new, independent organization that will build consensus and mobilize resources to find technologically and economically feasible solutions to this aspect of the animal waste problem.

Characterization of atmospheric ammonia emissions from swine waste storage and treatment lagoons

Fluxes of atmospheric ammonia-nitrogen (NH3-N, where NH3-N 5 (14/17)NH3) from an anaerobic ;2.5 ha (1 ha 5 10,000 m 2 ) commercial hog waste storage lagoon were measured during the summer of 1997 through the spring of 1998 in order to study the seasonal variability in emissions of NH3-N and its relationship to lagoon physicochemical properties. Ammonia-nitrogen fluxes were measured during each season (summer, fall, winter, and spring) using a dynamic flow through chamber system. Measured lagoon physicochemical parameters included surface lagoon temperature (T,8C, ;15 cm below surface), lagoon pH, and Total Kjeldahl Nitrogen (TKN). The pH and TKN of the surface lagoon water ranged from 7 to 8 pH units, and 500 to 750 mg N L 21 , respectively. The largest fluxes were observed during the summer (August 1997) (mean NH3-N flux 5 4017 6 987 m gNm 22 min 21 ). Fluxes decreased through the fall (December 1997) months (844 6 401 m gNm 22 min 21 ) to a minimum flux during the winter (February 1998) months (305 6 154 m gNm 22 min 21 ). Emission rates increased during spring (May 1998) (1706 6 552 m gNm 22 min 21 ), but did not reach the magnitude of fluxes observed during the summer. Lagoon emissions in eastern North Carolina were estimated to constitute ;33% of total NH3-N emissions from commercial hog operations in North Carolina based on current inventories for NH3-N emissions published by the North Carolina Division of Air Quality, North Carolina Department of Environment and Natural Resources. The ammonia flux may be predicted by an observational model log10 (NH3-N flux) 5 0.048 T, 1 2.1.

Ammonia in the atmosphere: a review on emission sources, atmospheric chemistry and deposition on terrestrial bodies

Gaseous ammonia (NH3) is the most abundant alkaline gas in the atmosphere. In addition, it is a major component of total reactive nitrogen. The largest source of NH3 emissions is agriculture, including animal husbandry and NH3-based fertilizer applications. Other sources of NH3 include industrial processes, vehicular emissions and volatilization from soils and oceans. Recent studies have indicated that NH3 emissions have been increasing over the last few decades on a global scale. This is a concern because NH3 plays a significant role in the formation of atmospheric particulate matter, visibility degradation and atmospheric deposition of nitrogen to sensitive ecosystems. Thus, the increase in NH3 emissions negatively influences environmental and public health as well as climate change. For these reasons, it is important to have a clear understanding of the sources, deposition and atmospheric behaviour of NH3. Over the last two decades, a number of research papers have addressed pertinent issues related to NH3 emissions into the atmosphere at global, regional and local scales. This review article integrates the knowledge available on atmospheric NH3 from the literature in a systematic manner, describes the environmental implications of unabated NH3 emissions and provides a scientific basis for developing effective control strategies for NH3.

Volatile organic compounds in some urban locations in United States

Volatile organic compounds (VOCs) have been determined to be human risk factors in urban environments, as well as primary contributors to the formation of photochemical oxidants. Ambient air quality measurements of 54 VOCs including hydrocarbons, halogenated hydrocarbons and carbonyls were conducted in or near 13 urban locations in the United States during September 1996 to August 1997. Air samples were collected and analyzed in accordance with US Environmental Protection Agency-approved methods. The target compounds most commonly found were benzene, toluene, xylene and ethylbenzene. These aromatic compounds were highly correlated and proportionally related in a manner suggesting that the primary contributors were mobile sources in all the urban locations studied. Concentrations of total hydrocarbons ranged between 1.39 and 11.93 parts per billion, by volume (ppbv). Ambient air levels of halogenated hydrocarbons appeared to exhibit unique spatial variations, and no single factor seemed to explain trends for this group of compounds. The highest halogenated hydrocarbon concentrations ranged from 0.24 ppbv for methylene chloride to 1.22 ppbv for chloromethane. At participating urban locations for the year of data considered, levels of carbonyls were higher than the level of the other organic compound groups, suggesting that emissions from motor vehicles and photochemical reactions strongly influence ambient air concentrations of carbonyls. Of the most prevalent carbonyls, formaldehyde and acetaldehyde were the dominant compounds, ranging from 1.5-7.4 ppbv for formaldehyde, to 0.8-2.7 ppbv for acetaldehyde.

Measurements and analysis of criteria pollutants in New Delhi, India

Ambient concentrations of carbon monoxide (CO), nitrogen oxides (NOx), sulfur dioxide (SO2), and total suspended particulates (TSP) were measured from January 1997 to November 1998 in the center of downtown [the Income Tax Office (ITO) located on B.S.G. Marg] New Delhi, India. The data consist of 24-h averages of SO2, NOx, and TSP as well as 8 and 24-h averages of CO. The measurements were made in an effort to characterize air pollution in the urban environment of New Delhi and assist in the development of an air quality index. The yearly average CO, NOx, SO2, and TSP concentrations for 1997 and 1998 were found to be 4810+/-2287 and 5772+/-2116 microg/m3, 83+/-35 and 64+/-22 microg/m3, 20+/-8 and 23+/-7 microg/m3, and 409+/-110 and 365+/-100 microg/m3, respectively. In general, the maximum CO, SO2, NOx, and TSP values occurred during the winter with minimum values occurring during the summer, which can be attributed to a combination of meteorological conditions and photochemical activity in the region. The ratio of CO/NOx (approximately 50) indicates that mobile sources are the predominant contributors for these two compounds in the urban air pollution problem in New Delhi. The ratio of SO2/NOx (approximately 0.6) indicates that point sources are contributing to SO2 pollution in the city. The averaged background CO concentrations in New Delhi were also calculated (approximately 1939 microg/m3) which exceed those for Eastern USA (approximately 500 microg/m3). Further, all measured concentrations exceeded the US National Ambient Air Quality Standards (NAAQS) except for SO2. TSP was identified as exceeding the standard on the most frequent basis.

CHARACTERIZATION OF NON-METHANE HYDROCARBONS IN THE RURAL SOUTHEAST UNITED STATES

Measurements of non-methane hydrocarbons, as well as ozone, meteorological and trace gas data, made at four rural sites located within the southeastern United States as a part of the Southern Oxidants Study are compared. The C2–C10 hydrocarbons were obtained during the 1200–1300 local time period, once every six days from September 1992 through October 1993. The light molecular weight alkanes (ethane, propane, n-butane, iso-butane, ethene and acetylene) display a seasonal variation of a winter maximum and summer minimum. Isoprene was virtually non-existent during the winter at all sites, and averaged from 9.8 ppbC (Yorkville, Georgia) to 21.15 ppbC (Centreville, Alabama) during the summer. The C10 terpene concentration was largest during the summer period with averages ranging between 3.19 ppbC (Centreville, Alabama) and 6.38 ppbC (Oak Grove, Mississippi); winter time concentrations ranged from 1.25 to 1.9 ppbC for all sites. Propylene-equivalent concentrations were calculated to account for differences in reaction rates between the hydroxyl radical and individual hydrocarbons, and to thereby estimate their relative contribution to ozone, especially in regard to the highly reactive biogenic compounds such as isoprene. The propy-equivalent concentrations from the biogenics represent at least 65% of the total non-methane hydrocarbon sum at these four sites during the summer season. A plot of ozone versus NOγ-NO highlights the NOx limited relationship of this region.

Analysis of ammonia, ammonium aerosols and acid gases in the atmosphere at a commercial hog farm in eastern North Carolina, USA

Abstract Measurements of atmospheric ammonia, acid gases, and ammonium aerosols were made at a commercial hog farm in Eastern North Carolina, USA, during September through December of 1997. Annular denuder systems (ADS) were used to sample gaseous (hydrogen chloride, nitrous acid, nitric acid, sulfur dioxide and ammonia) and fine aerosol (ammonium, chloride, nitrate, and sulfate) species. Ammonia and ammonium concentrations were determined by colorimetric analysis of the sample extracts. The acid gases and remaining fine particle ionic species were determined by ion chromatographic analysis of the sample extracts. Mean concentrations of the gaseous hydrogen chloride, nitrous acid, nitric acid, sulfur dioxide and ammonia were 0.743 μg/m 3 , 0.255 μg/m 3 , 0.154 μg/m 3 , 2.968 μg/m 3 , and 10.48 μg/m 3 , respectively. Mean concentrations of the fine particle chloride, nitrate, sulfate and ammonium were 0.321 μg/m 3 , 0.548 μg/m 3 , 3.247 μg/m 3 , and 1.102 μg/m 3 , respectively. The fine aerosol fraction was dominated by ammonium sulfate particles. A linear regression of sulfate versus ammonium by equivalent concentration showed a slope of 0.715 and r 2 of 0.88. An emission factor for total ammonia nitrogen flux was estimated using a simple box model as approximately 5 to 10 kg animal −1 year −1 .

PHOTOCHEMISTRY OF OZONE FORMATION IN ATLANTA, GA-MODELS AND MEASUREMENTS*

Chemical measurements made during an air pollution event in Atlanta, GA have been compared with results from several photochemical simulations. Measurements included Os, primary reactive organic gases (ROG), aldehydes, PAN, total reactive nitrogen (NO,,) and HzOz, with vertical profiles for primary ROG. Photochemical models using two different chemical representations and a range of assumptions about winds, vertical mixing and emissions were used to simulate the event. Results show that assumptions about vertical mixing can cause a variation in simulated surface concentrations of primary hydrocarbons of a factor of two or more. A tendency to underestimate isoprene was found in comparison with measured vertical profiles. The models tend to overestimate concentrations of HCHO, H,02 and PAN in comparison with measurements. Peak 0s and concurrent NO, from helicopter measurements was used as a basis for evaluating individual model scenarios. Scenarios were developed with different Op-NO,-ROG sensitivity, but only the NO,-sensitive scenarios are consistent with measured 09, NO, and isoprene. Key word index: Ozone, nitrogen oxides, hydrocarbons, photochemical smog, hydrogen, peroxide.

Measurement and Analysis of the Relationship between Ammonia, Acid Gases, and Fine Particles in Eastern North Carolina

Abstract An annular denuder system, which consisted of a cyclone separator; two diffusion denuders coated with sodium carbonate and citric acid, respectively; and a filter pack consisting of Teflon and nylon filters in series, was used to measure acid gases, ammonia (NH3), and fine particles in the atmosphere from April 1998 to March 1999 in eastern North Carolina (i.e., an NH3−rich environment). The sodium carbonate denuders yielded average acid gas concentrations of 0.23 μg/m3 hydrochloric acid (standard deviation [SD] ± 0.2 μg/m3); 1.14 μg/m3 nitric acid (SD ± 0.81 μg/m3), and 1.61 μg/m3 sulfuric acid (SD ± 1.58 μg/m3). The citric acid denuders yielded an average concentration of 17.89 μg/m3 NH3 (SD ± 15.03 μg/m3). The filters yielded average fine aerosol concentrations of 1.64 μg/m3 ammonium (NH4 +;SD ± 1.26 μg/m3); 0.26 μg/m3 chloride (SD ± 0.69 μg/m3), 1.92 μg/m3 nitrate (SD ± 1.09 μg/m3), and 3.18 μg/m3 sulfate (SO4 2−; SD ± 3.12 μg/m3). From seasonal variation, the measured particulates (NH4 +,SO4 2−, and nitrate) showed larger peak concentrations during summer, suggesting that the gas-to-particle conversion was efficient during summer. The aerosol fraction in this study area indicated the domination of ammonium sulfate particles because of the local abundance of NH3, and the long-range transport of SO4 2− based on back trajectory analysis. Relative humidity effects on gas-to-particle conversion processes were analyzed by particulate NH4 + concentration originally formed from the neutralization processes with the secondary pollutants in the atmosphere.

Measurements and analysis of reactive nitrogen species in the rural troposphere of Southeast United States: Southern oxidant study site SONIA

Ambient concentrations of reactive nitrogen compounds as well as total NO, were measured during June and early July 1992 at a rural site, site SONIA, in the central Piedmont region of North Carolina as a part of the Southern Oxidants Study. The measurements of reactive nitrogen species were made in an effort to provide a comprehensive understanding of nitrogen chemistry and to investigate the total nitrogen budget at the site. NO, NO, and NO showed diurnal variations with maxima in the morning between 0600 and 0900 EST. The maximum NO,, concentration reached was _ 14.5 ppbv, and the maximum concentrations of NO and NO, were 5.4 and 7.8 ppbv, respectively. The mean NO, mixing ratio was found to be 2.88 + 1.58 ppbv (n = 743) with an average daily maximum of 3.6 ppbv. The mean mixing ratios of NO and NO, were found to be 0.15 f 0.29 ppbv (n = 785) and 1.31 + 0.99 ppbv (n = 769). Average daily maxima of NO and NO, were 0.4 and 2.0 ppbv, respectively. HNO, and PAN showed diurnal variation with maxima in the afternoon and minimum in the night, and mean mixing ratios were found to be 0.67 + 0.33 ppbv (n = 250) and 0.40 + 0.24 ppbv (n = 578). The fractions of individual reactive nitrogen species to total NO, were investigated and contrasted to the results from a remote marine site and rural continental sites. As in two other rural continental sites in the U.S., NO, was found to be the most abundant constituent (~45%) of NO,; while HNO, was the most abundant compound in NO, measured at a remote marine site. The discrepancy between the NO, partitioning at site SONIA and the marine site is attributed to the influence of local and regional anthropogenic sources of NO, and the continental origin of the majority of air masses encountered at the site. The NO,/NO, ratio and NO, ( = NO, - NO,) were used as an indicator of the chemical age of airmasses. The NO&O, ratio showed strong positive correlations with the photochemical oxidants HNO, (r = 0.76), PAN (r = 0.68) and 0, (r = 0.79) measured at the site. Positive correlations were found between surface wind direction and both the magnitude of NO, and the NO,/NO, ratio. These correlations suggest that synoptic meteorological conditions and transport of NO, are important in the distribution of NO, and its relationship with photochemical oxidants at the site. The ozone production efficiency was illustrated by correlation of 0, and NO, and compared with other published measurements made in the Southeast U.S., and published results from a 3D Eulerian model simulation. Key word index: Reactive nitrogen species, atmospheric budget, ozone, oxidants, modeling.