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Remote sensing and in situ measurements of methane and ammonia emissions from a megacity dairy complex: Chino, CA

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... Having instruments that can collect high-sensitivity, fast-response in situ measurements of NH 3 are essential for directly measuring NH 3 emissions fluxes (e.g., from animal husbandry, agricultural fertilization) and eddy covariance fluxes (e.g., associated with deposition and evaporation processes), characterizing concentrations and emissions rates in plumes (e.g., from urban areas with emissions dominated by traffic, concentrated animal feeding operations, and wildfires), and sampling from mobile platforms (e.g., instrumented aircraft and ground-based vehicles). There are several techniques and types of instruments that can be used for rapid measurements of atmospheric NH 3 , including mass spectrometric methods (e.g., Nowak et al., 2007) and optical methods based upon open-path absorption (e.g., Miller et al., 2014;Ni et al., 2015), closed-path absorption (e.g., Griffith and Galle, 2000;Ellis et al., 2010;Leen et al., 2013;Martin et al., 2016;Leifer et al., 2017), and photoacoustic spectroscopy (e.g., Schmohl et al., 2002;Pushkarsky et al., 2002;Pogány et al., 2009). The mass spectrometric method has been effectively leveraged aboard research aircraft (Nowak et al., 2007(Nowak et al., , 2010, and the compact footprint associated with the photoacoustic approaches is useful for many applications. ...
... Here we describe the first opportunities to evaluate and carefully characterize the effects of adding passivant to an optical absorption-based, closed-path gas-phase NH 3 monitoring system aboard a research aircraft. We note that although this is not the first aircraft deployment of an opticalbased NH 3 monitor (Leen et al, 2013;Hacker et al., 2016;Schiferl et al., 2016;Miller et al., 2015;Leifer et al., 2017), this is the first opportunity to evaluate the effects and the value of adding a passivant to the sample stream of an optical-based instrument for airborne measurement applications. We start by characterizing the performance of the non-passivated instrument aboard a research aircraft in flight (e.g., precision, detection limit, motion sensitivity, and stability over time) with respect to fluctuations in cabin pressure and cabin temperature and changes in altitude. ...
... PFA tubing then brings sample flow from the inertial inlet box to the QC-TILDAS, which is co-located in the same equipment rack inside the aircraft cabin. As shown in previous studies, PFA tubing and fittings are used wherever possible along the sample pathway, and tubing lengths are kept to a minimum and heated wherever possible (Neuman et al., 1999;Schmohl et al., 2001;Mukhtar et al., 2003;Leifer et al., 2017). Components housed within the aircraft inlet strut are heated to 40 • C. The tubing between the inlet strut and the inertial inlet and between the inertial inlet and the QC-TILDAS are not actively heated; however, they are wrapped in flame-resistant polymer felt (DuPont Nomex) for thermal isolation. ...
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A closed-path quantum-cascade tunable infrared laser direct absorption spectrometer (QC-TILDAS) was outfitted with an inertial inlet for filter-less separation of particles and several custom-designed components including an aircraft inlet, a vibration isolation mounting plate, and a system for optionally adding active continuous passivation for gas-phase measurements of ammonia (NH3) from a research aircraft. The instrument was then deployed on the NSF/NCAR C-130 aircraft during research flights and test flights associated with the Western wildfire Experiment for Cloud chemistry, Aerosol absorption and Nitrogen (WE-CAN) field campaign. The instrument was configured to measure large, rapid gradients in gas-phase NH3, over a range of altitudes, in smoke (e.g., ash and particles), in the boundary layer (e.g., during turbulence and turns), in clouds, and in a hot aircraft cabin (e.g., average aircraft cabin temperatures expected to exceed 30 ∘C during summer deployments). Important design goals were to minimize motion sensitivity, maintain a reasonable detection limit, and minimize NH3 “stickiness” on sampling surfaces to maintain fast time response in flight. The observations indicate that adding a high-frequency vibration to the laser objective in the QC-TILDAS and mounting the QC-TILDAS on a custom-designed vibration isolation plate were successful in minimizing motion sensitivity of the instrument during flight. Allan variance analyses indicate that the in-flight precision of the instrument is 60 ppt at 1 Hz corresponding to a 3σ detection limit of 180 ppt. Zero signals span ±200, or 400 pptv total, with cabin pressure and temperature and altitude in flight. The option for active continuous passivation of the sample flow path with 1H,1H-perfluorooctylamine, a strong perfluorinated base, prevented adsorption of both water and basic species to instrument sampling surfaces. Characterization of the time response in flight and on the ground showed that adding passivant to a “clean” instrument system had little impact on the time response. In contrast, passivant addition greatly improved the time response when sampling surfaces became contaminated prior to a test flight. The observations further show that passivant addition can be used to maintain a rapid response for in situ NH3 measurements over the duration of an airborne field campaign (e.g., ∼2 months) since passivant addition also helps to prevent future buildup of water and basic species on instrument sampling surfaces. Therefore, we recommend the use of active continuous passivation with closed-path NH3 instruments when rapid (>1 Hz) collection of NH3 is important for the scientific objective of a field campaign (e.g., sampling from aircraft or another mobile research platform). Passivant addition can be useful for maintaining optimum operation and data collection in NH3-rich and humid environments or when contamination of sampling surfaces is likely, yet frequent cleaning is not possible. Passivant addition may not be necessary for fast operation, even in polluted environments, if sampling surfaces can be cleaned when the time response has degraded.
... Data are real-time integrated and visualized in Google Earth on a portable computer (Spectre360, HP) using custom software written in MATLAB (MathWorks, MA) that is described elsewhere (Leifer et al., 2018b(Leifer et al., , a, 2016(Leifer et al., , 2014. Real-time visualization facilitates adaptive surveys, wherein the survey route is modified based on real-time data to improve outcomes (Thompson et al., 2015) -in this case to facilitate plume tracking and to ensure transects were near orthogonal to the wind. ...
... The plume inversion model is a three-step process (Leifer et al., 2018a(Leifer et al., , b, 2016. Emissions from focused seep areas were derived from offshore data by first fitting Gaussian function(s) to orthogonal transect C data, termed the data model. ...
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In this study, we present a novel approach for assessing nearshore seepage atmospheric emissions through modeling of air quality station data, specifically a Gaussian plume inversion model. A total of 3 decades of air quality station meteorology and total hydrocarbon concentration, THC, data were analyzed to study emissions from the Coal Oil Point marine seep field offshore California. THC in the seep field directions was significantly elevated and Gaussian with respect to wind direction, θ. An inversion model of the seep field, θ-resolved anomaly, THC′(θ)-derived atmospheric emissions is given. The model inversion is for the far field, which was satisfied by gridding the sonar seepage and treating each grid cell as a separate Gaussian plume. This assumption was validated by offshore in situ data that showed major seep area plumes were Gaussian. Plume total carbon, TC (TC = THC + carbon dioxide, CO2, + carbon monoxide), 18 % was CO2 and 82 % was THC; 85 % of THC was CH4. These compositions were similar to the seabed composition, demonstrating efficient vertical plume transport of dissolved seep gases. Air samples also measured atmospheric alkane plume composition. The inversion model used observed winds and derived the 3-decade-average (1990–2021) field-wide atmospheric emissions of 83 400 ± 12 000 m3 THC d−1 (27 Gg THC yr−1 based on 19.6 g mol−1 for THC). Based on a 50 : 50 air-to-seawater partitioning, this implies seabed emissions of 167 000 m3 THC d−1. Based on atmospheric plume composition, C1–C6 alkane emissions were 19, 1.3, 2.5, 2.2, 1.1, and 0.15 Gg yr−1, respectively. The spatially averaged CH4 emissions over the ∼ 6.3 km2 of 25 × 25 m2 bins with sonar values above noise were 5.7 µM m−2 s−1. The approach can be extended to derive emissions from other dispersed sources such as landfills, industrial sites, or terrestrial seepage if source locations are constrained spatially.
... In some regions both sources are important, particularly in regions of mixed land use, such as Denver and Los Angeles (Sun et al., 2017). The eastern portions of the Los Angeles Air Basin are strongly influenced by mobile sources Kean et al., 2009, Leifer et al., 2017. Fraser and Cass (1998) reported that NH 3 emissions from light-duty motor vehicles equipped with three-way catalytic converters are similar in magnitude to agricultural emissions in the Los Angeles Air Basin. ...
... Likewise, the Santa Margarita site is too far south to be affected by the dairies and also has lower NH 3 concentrations than Camp Paivika. Leifer et al. (2017) reported elevated NH 3 along the south-facing slopes of the San Gabriel and San Bernardino Mountains and along the eastern Interstate 10 corridor extending eastward to Palm Springs. This result confirms the elevated NH 3 concentrations we report for Camp Paivika located on the SW end of the San Bernardino Mountains. ...
Article
We provide updated spatial distribution and inventory data for on-road NH3 emissions for the continental United States (U.S.) On-road NH3 emissions were determined from on-road CO2 emissions data and empirical NH3:CO2 vehicle emissions ratios. Emissions of NH3 from on-road sources in urbanized regions are typically 0.1-1.3tkm-2yr-1 while NH3 emissions in agricultural regions generally range from 0.4-5.5tkm-2yr-1, with a few hotspots as high as 5.5-11.2tkm-2yr-1. Counties with higher vehicle NH3 emissions than from agriculture include 40% of the U.S. Population: The amount of wet inorganic N deposition as NH4+ from the National Atmospheric Deposition Program (NADP) network ranged from 37 to 83% with a mean of 58.7%. Only 4% of the NADP sites across the U.S. had <45% of the N deposition as NH4+ based on data from 2014 to 2016, illustrating the near-universal elevated proportions of NH4+ in deposition across the U.S. Case studies of on-road NH3 emissions in relation to N deposition include four urban sites in Oregon and Washington where the average NH4-N:NO3-N ratio in bulk deposition was 2.3. At urban sites in the greater Los Angeles Basin, bulk deposition of NH4-N and NO3-N were equivalent, while NH4-N:NO3-N in throughfall under shrubs ranged from 0.6 to 1.7. The NH4-N:NO3-N ratio at 7-10 sites in the Lake Tahoe Basin averaged 1.4 and 1.6 in bulk deposition and throughfall, and deposition of NH4-N was strongly correlated with summertime NH3 concentrations. On-road emissions of NH3 should not be ignored as an important source of atmospheric NH3, as a major contributor to particulate air pollution, and as a driver of N deposition in urban and urban-affected regions.
... The development of reliable IR light sources, initially near-infrared (NIR) diode lasers and later mid-infrared quantum cascade lasers, resulted in an increasing number of spectroscopic instruments on the market. These include cavity ring down systems (CRDS, (Martin et al., 2016;Kamp et al., 2019)), Optical-feedback cavity-enhanced absorption spectrometers (OF-CEAS, (Leen et al., 2013;Leifer et al., 2017)), quantum cascade laser absorption spectrometers (QCLAS, (Whitehead et al., 2008;Ellis et al., 2010;Zöll et al., 2016)), open 25 path Fourier Transform InfraRed systems (FTIR, (D. L. Bjorneberg et al., 2009;Suarez-Bertoa et al., 2017)) and photoacoustic methods (Pogány et al., 2009;von Bobrutzki et al., 2010;Liu et al., 2019). ...
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Ammonia (NH3) in the atmosphere affects both the environment and human health. It is therefore increasingly recognised by policy makers as an important air pollutant that needs to be mitigated. In order to understand the effectiveness of abatement strategies, routine NH3 monitoring is required. Current reference protocols, developed in the 1990s, use daily samplers with offline analysis but there have been a number of technologies developed since, which may be applicable for high time resolution routine monitoring of NH3 at ambient concentrations. The following study is a comprehensive field intercomparison held over an intensively managed grassland in South East Scotland using currently available methods that are reported to be suitable for routine monitoring of ambient NH3. In total 13 instruments took part in the field study. The instruments include: an online ion chromatography system (MARGA, Metrohm-Applikon,NL), two wet chemistry continuous flow analysis systems (AiRRmonia, Mechatronics, NL), a photoacoustic spectrometer (NH3 monitor, LSE, NL), two mini Differential Optical Absorption Spectrometers (miniDOAS; NTB Interstate University of Applied Sciences Buchs, now part of "Eastern Switzerland University of Applied Sciences, CH and RIVM, NL), as well as seven spectrometers using cavity enhanced techniques: a Quantum Cascade Laser Absorption Spectrometer (QCLAS, Aerodyne, Inc. US), Picarro G2103 Analyzer (Picarro US), Economical NH3 Analyser (Los Gatos Research, US), Tiger-i 2000 (Tiger Optics, US) and LaserCEM® gas analyser (AP2E, FR). Assessments of the instruments’ precision at low concentrations ( 0.75). At concentrations below 10 ppb however, instruments fell into two distinct groups and the duplicate instruments, miniDOAS, AiRRmonia, LGR and Picarro were split across the two groups. It was found that identical instruments performed differently at low concentrations, highlighting the impact of the setup, inlet design and operation of the instrument used. Accuracy in determining absolute concentrations in the field was assessed using a calibration-free CRDS Optical Gas Standard (OGS, PTB, DE), serving as an instrumental reference standard. Accuracy was also assessed using well established metrological standards for calibration gases, i) a permeation system (ReGaS1, METAS, CH) and ii) Primary Standard gas Mixtures (PSMs) prepared by gravimetry (NPL, UK). This study showed that though the OGS good performance with respect to sensitivity and linearity with reference gas standards, this in itself is not enough for the OGS to be a field reference standard because a closed path spectrometer has limitations due to losses to surfaces in sampling NH3, which need to be taken into account. Overall, the instruments studied performed well against the standard gases but we note that not every instrument could be calibrated using gas standards due to incompatible inlet designs and limitations in the gas flow rates of the standards. This work provides evidence that though NH3 instrumentation have greatly progressed in measurement precision, there is still further work required to quantify the accuracy of these systems under field conditions. It is the recommendation of this study that the use of instruments for routine monitoring of NH3 needs to be set out in standard operating protocols for inlet set-up, calibration and routine maintenance, in order for datasets to be comparable.
... The plume inversion model is a three-step process (Leifer, Melton, Fischer, et al., 2018;Leifer, Melton, Tratt, et al., 250 2018; Leifer et al., 2016). Emissions from focused seep areas were derived from offshore data by first fitting Gaussian 251 function(s) to orthogonal transect C' data, termed the data model. ...
Preprint
Full-text available
In this study, we present a novel approach for assessing nearshore seepage atmospheric emissions through modeling of air quality station data, specifically, a Gaussian plume inversion model. Three decades of air quality station meteorology and total hydrocarbon concentration, THC, data were analysed to study emissions from the Coal Oil Point marine seep field offshore California. THC in the seep field directions was significantly elevated and Gaussian with respect to wind direction, θ. An inversion model of the seep field anomaly, THC’(θ), derived atmospheric emissions. The model inversion is for the far field, which was satisfied by gridding the sonar seepage and treating each grid cell as a separate Gaussian plume. This assumption was validated by offshore in situ offshore data that showed major seep area plumes were Gaussian. Plume air sample THC was 85 % methane, CH4, and 20 % carbon dioxide, CO2, similar to seabed composition, demonstrating efficient vertical plume transport of dissolved seep gases. Air samples also measured atmospheric alkane plume composition. The inversion model used observed winds and derived the three-decade-average (1990–2021) field-wide atmospheric emissions of 83,500 ± 12,000 m3 THC day−1. Based on a 50:50 air to seawater partitioning, this implies seabed emissions of 167,000 m3 THC dy−1. Based on atmospheric plume composition, C1-C6 alkane emissions were 19, 1.3, 2.5, 2.2, 1.1, and 0.15 Gg yr−1, respectively. The approach can be extended to derive emissions from other dispersed sources such as landfills, industrial sites, or terrestrial seepage if source locations are constrained spatially.
... Sampling line losses introduce up to a factor of 3 uncertainty in the ammonia measurement, corresponding to transmission efficiencies between 33.7 % and 100 % for walls that are a perfect sink and zero sink, respectively. Variable sampling efficiency is a general problem encountered for most ammonia measurements (e.g., Leifer et al., 2017). The uncertainty is smaller for larger molecules; e.g., the sampling efficiency for triethylamine (diffusivity of 0.067 cm 2 s −1 ; Tang et al., 2015) is 61 %. ...
Article
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Here we describe the design and performance of a new water cluster chemical ionization–atmospheric pressure interface time-of-flight mass spectrometer (CI-APi-TOF). The instrument selectively measures trace gases with high proton affinity such as ammonia and dimethylamine, which are important for atmospheric new particle formation and growth. Following the instrument description and characterization, we demonstrate successful measurements at the CERN CLOUD (Cosmics Leaving OUtdoor Droplets) chamber where very low ammonia background levels of ∼4 pptv were achieved (at 278 K and 80 % RH). The limit of detection of the water cluster CI-APi-TOF is estimated to be ∼0.5 pptv for ammonia. Although no direct calibration was performed for dimethylamine (DMA), we estimate its detection limit is at least 3 times lower. Due to the short ion–molecule reaction time and high reagent ion concentrations, ammonia mixing ratios up to at least 10 ppbv can be measured with the instrument without significant reagent ion depletion. Besides the possibility to measure compounds like ammonia and amines (dimethylamine), we demonstrate that the ionization scheme is also suitable for the measurement of trace gases containing iodine. During CLOUD experiments to investigate the formation of new particles from I2, many different iodine-containing species were identified with the water cluster CI-APi-TOF. The compounds included iodic acid and neutral molecular clusters containing up to four iodine atoms. However, the molecular structures of the iodine-containing clusters are ambiguous due to the presence of an unknown number of water molecules. The quantification of iodic acid (HIO3) mixing ratios is performed from an intercomparison with a nitrate CI-APi-TOF. Using this method the detection limit for HIO3 can be estimated as 0.007 pptv. In addition to presenting our measurements obtained at the CLOUD chamber, we discuss the applicability of the water cluster Ci-APi-TOF for atmospheric measurements.
... A remote LWIR HSI system provides numerous capabilities of great interest to the earth sensing community. These capabilities include the ability to remotely monitor trace LWIR-active gas plumes, such as methane (CH 4 ) and ammonia (NH 3 ), both of which have spectroscopic signatures in the LWIR (Leifer et al., 2017). Moreover, gases can be detected concurrently using standard spectral identification algorithms. ...
Article
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We present the first flight data using a Computational Reconfigurable Imaging Spectrometer (CRISP) system. CRISP (Sullenberger et al., 2017) is a novel hyperspectral thermal imaging spectrometer that uses computational imaging to enable high sensitivity measurements (via spectral multiplexing) from smaller, noisier, and less-expensive components (e.g., uncooled microbolometers) making it useful on small space and air platforms with strict size, weight, and power requirements. In contrast to other multiplexing hyperspectral solutions (e.g Michelson interferometer), it does not require moving parts, allowing for a robust system without aggressive engineering solutions. We discuss flight system design and calibration. Spectra from ground targets and gaseous species are compared to performance expectations. We successfully demonstrate the ability to extract airborne longwave infrared (8–12 μm) imagery and spectra from an uncooled camera-based CRISP system.
... A range of flux quantification techniques can be used to derive facility-scale top-down flux estimates using either remote sensing or in situ sampling [13,14]. Remote sensing provides a greater spatial sampling extent at the expense of reduced spatial resolution [15] by either facing towards the emission plume [16,17] or by sampling downwards from above it [18][19][20]. For example, partial column ...
Article
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Point-source methane emission flux quantification is required to help constrain the global methane budget. Facility-scale fluxes can be derived using in situ methane mole fraction sampling, near-to-source, which may be acquired from an unmanned aerial vehicle (UAV) platform. We test a new non-dispersive infrared methane sensor by mounting it onto a small UAV, which flew downwind of a controlled methane release. Nine UAV flight surveys were conducted on a downwind vertical sampling plane, perpendicular to mean wind direction. The sensor was first packaged in an enclosure prior to sampling which contained a pump and a recording computer, with a total mass of 1.0 kg. The packaged sensor was then characterised to derive a gain factor of 0.92 ± 0.07, independent of water mole fraction, and an Allan deviation precision (at 1 Hz) of ±1.16 ppm. This poor instrumental precision and possible short-term drifts made it non-trivial to define a background mole fraction during UAV surveys, which may be important where any measured signal is small compared to sources of instrumental uncertainty and drift. This rendered the sensor incapable of deriving a meaningful flux from UAV sampling for emissions of the order of 1 g s−1. Nevertheless, the sensor may indeed be useful when sampling mole fraction enhancements of the order of at least 10 ppm (an order of magnitude above the 1 Hz Allan deviation), either from stationary ground-based sampling (in baseline studies) or from mobile sampling downwind of sources with greater source flux than those observed in this study. While many methods utilising low-cost sensors to determine methane flux are being developed, this study highlights the importance of adequately characterising and testing all new sensors before they are used in scientific research.
... We are aware that the sampling line losses introduce some uncertainty on the ammonia measurement. However, this is an effect other in-situ techniques also have to struggle with (see, e.g., Leifer et al. (2017)). We also want to note that the effect is much smaller for larger molecules, e.g., the penetration for triethylamine (diffusivity of 0.067 cm 2 s -1 , Tang et al. (2015)) reaches 61%. ...
Article
Full-text available
A new water cluster Chemical Ionization-Atmospheric Pressure interface-Time Of Flight mass spectrometer (CI-APi-TOF) is introduced. The instrument is designed for the selective measurement of trace gases with high proton affinity, such as ammonia, amines, and diamines that are, for example, relevant for atmospheric new particle formation. Following the instrument description and characterization, we demonstrate successful measurements at the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber where very low ammonia background levels of ~ 4 pptv were achieved (at 278 K and 80 % RH). The estimated level of detection of the water cluster CI-APi-TOF can be estimated as ~ 0.5 pptv for ammonia and it is significantly lower for amines. Due to a short reaction time (
... These methodologies have not commonly been invoked for satellite retrievals because until recently in most such cases the GRD is inadequate for resolving the actual source (Nassar et al., 2017, present a recent countervailing case). Spectral matched filter retrievals have demonstrated significant utility in the inversion of surface fluxes (Leifer et al., 2017;Leifer, Melton, Tratt, et al., 2018), complementary to the approaches more commonly used with satellite data (e.g., Nassar et al., 2014). ...
Article
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Abstract Despite their importance to climate change, significant current and future source uncertainties remain for the most important carbon greenhouse gases (GHGs) methane (CH4) and carbon dioxide (CO2), particularly for the developing world. Mitigation by effective regulation and treaties requires accurate global GHG budgets, which only global‐scale (satellite) remote sensing can deliver. A high spatial and spectral resolution spectrometer is needed; herein, we present the design concept for a Multi‐Order Carbon Spectral Imager (MOCSI). MOCSI is designed for the global measurement of differential GHG column density and source fingerprinting from low Earth orbit. MOCSI includes three wavebands for CH4, CO2, and carbon monoxide (CO), whose altitude weighting functions emphasize the boundary layer, where the dominant GHG anthropogenic and natural sources are still unmixed and therefore most easily discerned against background levels. CO aids discrimination of megacity and fire GHG emissions from other sources and is also a precursor for ozone, which is also an important GHG. High spectral resolution ensures discrimination of target species from interferents, while high spatial resolution enhances sensitivity for discrete source identification and emission quantification. MOCSI is a compact, high‐throughput shortwave‐infrared pushbroom spectrometer that disperses multiple orders of a single grating onto a single focal plane array to minimize size, weight, and power of the instrument. MOCSI is specified to provide spatial and temporal resolution and sensitivity sufficient to address important global science questions related to megacity emissions, shifts in hydrocarbon production, and disaster response, as well as many others.
... Mobile platforms increasing flight altitude (Thorpe et al., 2017). 2-D thermal infrared sensors such as the Spatially Enhanced Broadband Array Spectrograph System (SEBASS, Hackwell et al., 1996), Mako (Warren et al., 2010;Hall et al., 2011) and the airborne Hyperspectral Thermal Emission Spectrometer (HyTES, Hook et al., 2009Hook et al., , 2013 have been successfully applied to identify CH 4 (and CO 2 ) emissions from various types of sources (e.g., oil and gas production sites, power plants, landfills, and diary feedlots; Tratt et al., 2014;Frankenberg et al., 2016;Hulley et al., 2016;Kuai et al., 2016;Leifer et al., 2017b). One advantage of airborne TIR compared to SWIR instruments is that they do not require clear sky and are able to acquire data also during night or cloudy conditions. ...
Article
Methane (CH4) is the second most important anthropogenic greenhouse gas. Its atmospheric concentration is significantly influenced by human activities and has increased over the past years. The adverse effects of such a greenhouse gas on the climate system has identified need to control its emissions. However, an accurate assessment of the different emission sources by existing observations remains challenging. Consequently, the methane budget still has significant uncertainties, especially for local sources. In this study, an attempt was made to quantify emissions for areal sources and complex source regions (about 1 to 90 km2 in area) using passive remote sensing data and in-situ data. The data set was collected during the COMEX (CO2 and MEthane eXperiment) research campaign in California in 2014. It comprised observations of CH4 by airborne remote sensing non-imaging (Methane Airborne MAPper, MAMAP) and imaging (Airborne Visible / Infrared Imaging Spectrometer - Next Generation, AVIRIS-NG) instruments as well as aircraft in-situ observations of CH4 and carbon dioxide (CO2) with a Picarro greenhouse gas in-situ analyser. The main objective was the quantitative analysis of emissions from prominent CH4 sources such as landfills and oil fields and, if present, also accompanying CO2 emissions. In particular, the unique spectroscopic measurements in the short wave infrared region from the MAMAP remote sensing instrument have successfully been used for this purpose. This was also the first time that CH4 emissions from an entire landfill and an oil field complex were quantitatively estimated from airborne remote sensing data. Elevated CH4 concentrations (or 'CH4 plumes') were detected downwind from landfills and across oil fields by remote sensing aircraft surveys using the MAMAP instrument. Following each remote sensing survey, the detected plumes were sampled within the atmospheric boundary layer by in-situ instruments on the same aircraft for atmospheric parameters such as wind information and dry gas mole fractions of CH4 and CO2. These measurements facilitated an independent assessment and verification of the surface fluxes. During the COMEX campaign, four landfills in the Los Angeles Basin were surveyed, where one landfill repeatedly showed a clear emission plume on four flight days. Additionally, an oil field complex in the San Joaquin Valley was investigated on seven days. Emission rates estimated from the MAMAP remote sensing and Picarro in-situ observations via mass balance approaches vary between 11.6 and 17.8 ktCH4/yr for the landfill, and between 31.0 and 47.1 ktCH4/yr for the oil field complex for several overpasses. Case-dependent relative uncertainties are between 17% to 45%. Furthermore, the in-situ and remote sensing based emission rates agree well within the error bars. The reported inventory value of the landfill of 11.5 ktCH4/yr for 2014 by the US Environmental Protection Agency (EPA) is on average 2.8 ktCH4/yr lower than the top-down estimate from this study. The top-down estimates of the oil field complex are consistent with the latest inventory estimate but can differ significantly if basic assumptions of production rates and emission factors are used yielding only around 6 ktCH4/yr. The imaging capabilities of the AVIRIS-NG instrument aboard a simultaneously flown second aircraft additionally allowed the identification of a possible leak in the landfill cover and the exact source positions of the emitters across the oil field complex.
... The ), compared to those in the free troposphere presumably may compensate at least partly for this drawback. As it was found by Leifer et al. (2017), IASI data correlate with enhanced VMRs in the lowest atmospheric layers over strong sources in California. Methane VMR near the surface varied between a background value of 1.98 and perturbations up to 5.0 ppmv. ...
Preprint
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Supplement material for "Methane Variation Over Terrestrial And Marine Arctic Areas (2010 – 2017): IASI Satellite Data" by Yurganov et al.
... The ), compared to those in the free troposphere presumably may compensate at least partly for this drawback. As it was found by Leifer et al. (2017), IASI data correlate with enhanced VMRs in the lowest atmospheric layers over strong sources in California. Methane VMR near the surface varied between a background value of 1.98 and perturbations up to 5.0 ppmv. ...
Preprint
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There is evidence that the winter Arctic sea and summer Arctic land are releasing methane into the atmosphere. Methane concentration in the Arctic lower and upper troposphere was retrieved by NOAA between 2010 and 2017 from IASI data, a thermal IR spectrometer orbiting the Earth on the European MetOp-A satellite. A significant increase in the methane growth rate was found after 2013-2014, in accord with global NOAA/ESRL network observations. This recent methane acceleration may indicate a change of the long-term trend or may relate to the strong El-Niño of 2015-2016. Methane anomalies were calculated by two modes; Mode 1 was referenced to 2010-2012, and Mode 2 was referenced to a specific offshore region in the North Atlantic Ocean (50° N to 83° N). Maps of Mode 1 anomaly reveal several patches of the maximal growth rate over winter-time sea. Siberia demonstrates the fastest growing methane in summer high Northern hemisphere land. Maximal methane Mode 2 anomalies over the Barents Sea coincide with periods of strong and deep mixing of the winter Arctic Ocean water column between November and March. Marine Mode 2 anomalies over the ocean stay close to zero every summer, whereas marine winter Mode 2 anomalies have increased after 2014, doubling in magnitude in 2016 compared to mean values in 2010-2012.
... Meanwhile, sources of methane are located on the land surface, they may increase its mixing ratios up to 3-4 ppmv (parts per million by volume), i.e. doubling its background (Leifer et al., 2017). At such high mixing ratios the instrument can be capable of examining the lower troposphere even with reduced sensitivity. ...
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English translation. To be published in the "Current problems in remote sensing of the Earth from space", v. 14, No ?, 2017 (in Russian), http://jr.rse.cosmos.ru/?lang=eng European orbital IASI/MetOP-A interferometer TIR radiation data were processed by NOAA for methane profiles and uploaded in a publicly accessible archive. Satellite measurements for the middle and high latitudes of the Northern Hemisphere reveal a concentration growth rate of 4-9 ppbv/year in 2010-2013 and up to 12-17 ppbv/year in the 2015-2016. Global estimates based on surface measurements of NOAA at coastal stations for the same periods show an increase from 5-6 ppbv/year after 2007 to 9-12 ppbv/year last two years. Satellite data allow analyzing the methane concentration both over land and over the Arctic seas in the absence of near-surface temperature inversions. The results of remote measurements are compared with direct aircraft measurements in summer-autumn Alaska during the CARVE experiment. The maximum anomalies of methane (in comparison with a relatively clean area between Scandinavia and Iceland) were observed in November-December over the sea surface along the coasts of Norway, Novaya Zemlya, Svalbard and other regions of the Arctic. Anomalies were insignificant in summer. Over the years, the winter anomalies (contrasts) grew: the maximum rate was recorded for the area to the west of Novaya Zemlya (9.4 ± 3.7) ppbv/year. Above Alaska, the anomaly of methane concentration in summer, when the microbilogical sources are active, increased at a rate (2.6 ± 1.0) ppbv/year. The locations of the maxima of the anomaly around Svalbard correspond to the observed methane seeps from the seabed and the predicted regions of dissociation of methane hydrates. The observed methane acceleration during the last two years does not necessarily indicate a long-term tendency: 2015-2016 was a strong El-Niño period.
... Meanwhile, sources of methane are located on the land surface, they may increase its mixing ratios up to 3-4 ppmv (parts per million by volume), i.e. doubling its background (Leifer et al., 2017). At such high mixing ratios the instrument can be capable of examining the lower troposphere even with reduced sensitivity. ...
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European orbital IASI/MetOP-A interferometer TIR radiation data were processed by NOAA for methane profiles and uploaded in a publicly accessible archive. Satellite measurements for the middle and high latitudes of the Northern Hemisphere reveal a concentration growth rate of 4–9 ppbv/year in 2010–2013 and up to 12–17 ppbv/year in the 2015–2016. Global estimates based on surface measurements of NOAA at coastal stations for the same periods show an increase from 5-6 ppbv/year after 2007 to 9–12 ppbv/year last two years. Satellite data allow analyzing the methane concentration both over land and over the Arctic seas in the absence of near-surface temperature inversions. The results of remote measurements are compared with direct aircraft measurements in summer-autumn Alaska during the CARVE experiment. The maximum anomalies of methane (in comparison with a relatively clean area between Scandinavia and Iceland) were observed in November-December over the sea surface along the coasts of Norway, Novaya Zemlya, Svalbard and other regions of the Arctic. Anomalies were insignificant in summer. Over the years, the winter anomalies (contrasts) grew: the maximum rate was recorded for the area to the west of Novaya Zemlya (9.4±3.7) ppbv/year. Above Alaska, the anomaly of methane concentration in summer, when the microbilogical sources are active, increased at a rate (2.6±1.0) ppbv/year. The locations of the maxima of the anomaly around Svalbard correspond to the observed methane seeps from the seabed and the predicted regions of dissociation of methane hydrates. The observed methane acceleration during the last two years does not necessarily indicate a long-term tendency: 2015–2016 was a strong El- Niño period.
... Meanwhile, sources of methane are located on the land surface, they may increase its mixing ratios up to 3-4 ppmv (parts per million by volume), i.e. doubling its background (Leifer et al., 2017). At such high mixing ratios the instrument can be capable of examining the lower troposphere even with reduced sensitivity. ...
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The atmosphere is composed of nitrogen, oxygen and argon, a variety of trace gases, and particles or aerosols from a variety of sources. Reactive, trace gases have short mean residence time in the atmosphere and large spatial and temporal variations in concentration. Many trace gases are removed by reaction with hydroxyl radical and deposition in rainfall or dryfall at the Earth's surface. The upper atmosphere, the stratosphere, contains ozone that screens ultraviolet light from the Earth's surface. Chlorofluorocarbons released by humans lead to the loss of stratospheric ozone, which might eventually render the Earth's land surface uninhabitable. Changes in the composition of the atmosphere, especially rising concentrations of CO2, CH4, and N2O, will lead to climatic changes over much of the Earth's surface.
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Hydrogen sulfide (H 2 S) is responsible for many incidents of occupational toxic exposure, especially in the petroleum industry. The clinical effects of H 2 S depend on its concentration and the duration of exposure. H 2 S is immediately fatal when concentrations are over 500-1000 parts per million (ppm) but exposure to lower concentrations, such as 10-500 ppm, can cause various respiratory symptoms that range from rhinitis to acute respiratory failure. H 2 S may also affect multiple organs, causing temporary or permanent derangements in the nervous, cardiovascular, renal, hepatic, and hematological systems. We present a case of occupational exposure to H 2 S leading to multi-organ involvement, acute respiratory failure, organizing pneumonia, and shock resembling acute sepsis. The patient also developed mild obstructive and restrictive pulmonary disease and peripheral neuropathy.
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Mid-upper tropospheric methane (CH4), as an operational product at NOAA's (National Oceanic and Atmospheric Administration) Comprehensive Large Array-data Stewardship System (CLASS), has been retrieved from the Infrared Atmospheric Sounding Interferometer (IASI) since 2008. This paper provides a description of the retrieval method and the validation using 596 CH4 vertical profiles from aircraft measurements by the HIAPER Pole-to-Pole Observations (HIPPO) program over the Pacific Ocean. The number of degrees of freedom for the CH4 retrieval is mostly less than 1.5, and it decreases under cloudy conditions. The retrievals show greatest sensitivity between 100–600 hPa in the tropics and 200–750 hPa in the mid- to high latitude. Validation is accomplished using aircraft measurements (convolved by applying the monthly mean averaging kernels) collocated with all the retrieved profiles within 200 km and on the same day, and the results show that, on average, a larger error of CH4 occurs at 300–500 hPa. The bias in the trapezoid of 374–477 hPa is −1.74% with a residual standard deviation of 1.20%, and at layer 596–753 hPa the bias is −0.69% with a residual standard deviation of 1.07%. The retrieval error is relatively larger in the high northern latitude regions and/or under cloudy conditions. The main reasons for this negative bias include the uncertainty in the spectroscopy near the methane Q branch and/or the empirical bias correction, plus residual cloud contamination in the cloud-cleared radiances. It is expected for NOAA to generate the CH4 product for 20 + years using a similar algorithm from three similar thermal infrared sensors: Atmospheric Infrared Sounder (AIRS), IASI and the Cross-track Infrared Sounder (CrIS). Such a unique product will provide a supplementary to the current ground-based observation network, particularly in the Arctic, for monitoring the CH4 cycle, its transport and trend associated with climate change.
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The Border Air Quality and Meteorology study (BAQS-Met) was an intensive field campaign conducted in Southwestern Ontario during the summer of 2007. The focus of BAQS-Met was determining the causes of the formation of ozone and fine particulate matter (PM<sub>2.5</sub>), and of the regional significance of trans-boundary transport and lake breeze circulations on that formation. Fast (1 Hz) measurements of ammonia were acquired using a Quantum Cascade Laser Tunable Infrared Differential Absorption Spectrometer (QC-TILDAS) at the Harrow supersite. Measurements of PM<sub>2.5</sub> ammonium, sulfate and nitrate were made using an Ambient Ion Monitor Ion Chromatograph (AIM-IC) with hourly time resolution.The median mixing ratio of ammonia was 2.5 ppb, with occasional high spikes at night resulting from local emissions. Measurements were used to assess major local emissions of NH<sub>3</sub>, diurnal profiles and gas-particle partitioning. The measurements were compared with results from A Unified Regional Air-quality Modelling System (AURAMS). While the fraction of total ammonia (NH<sub>x</sub>≡NH<sub>3</sub> + NH<sub>4</sub><sup>+</sup>) observed in the gas phase peaks between 0.1 and 0.8, AURAMS tended to predict fractions of either less than 0.05 or greater than 0.8. The model frequently predicted acidic aerosol, in contrast withobservations whereinNH<sub>x</sub> always exceeded the observed equivalents of sulfate. One explanation for our observations is that the net flux of ammonia from the land surface to the atmosphere increases when aerosol sulfate is present, effectively buffering the mixing ratio of gas phase ammonia, a process not included in the model. We explore the impact of a bi-directional flux parameterization on the predicted gas-particle partitioning of atmospheric ammonia.
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We use in situ observations from the Interagency Monitoring of PROtected Visual Environments (IMPROVE) network, the Midwest Ammonia Monitoring Project, 11 surface site campaigns as well as Infrared Atmospheric Sounding Interferometer (IASI) satellite measurements with the GEOS-Chem model to investigate inorganic aerosol loading and atmospheric ammonia concentrations over the United States. IASI observations suggest that current ammonia emissions are underestimated in California and in the springtime in the Midwest. In California this underestimate likely drives the underestimate in nitrate formation in the GEOS-Chem model. However in the remaining continental United States we find that the nitrate simulation is biased high by a factor of 1.5 or more year-round. None of the uncertainties in precursor emissions, the uptake efficiency of N<sub>2</sub>O<sub>5</sub> on aerosols, OH concentrations, the reaction rate for the formation of nitric acid, or the dry deposition velocity of nitric acid are able to explain this. We find that reducing nitric acid concentrations to 2/3 of their simulated values corrects the bias in nitrate (as well as ammonium) in the US. However the mechanism for this potential reduction is unclear and may be a combination of errors in chemistry, deposition and sub-grid near-surface gradients. This "updated" simulation reproduces PM and ammonia loading and captures the strong seasonal and spatial gradients in gas-particle partitioning across the United States. We estimate that nitrogen makes up 15–35% of inorganic fine PM mass over the US, and that this fraction is likely to increase in the coming decade, both with decreases in sulfur emissions and increases in ammonia emissions.
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Ammonia (NH3) plays an increasingly important role in the global biogeochemical cycle of reactive nitrogen as well as in aerosol formation and climate. We present extensive and nearly continuous global ammonia measurements made by the Atmospheric Infrared Sounder (AIRS) from the Aqua satellite to identify and quantify major persistent and episodic sources as well as to characterize seasonality. We examine the 13-year period from September 2002 through August 2015 with a retrieval algorithm using an optimal estimation technique with a set of three, spatially and temporally uniform a priori profiles. Vertical profiles show good agreement (∼ 5–15 %) between AIRS NH3 and the in situ profiles from the winter 2013 DISCOVER-AQ (DISCOVER-Air Quality) field campaign in central California, despite the likely biases due to spatial resolution differences between the two instruments. The AIRS instrument captures the strongest consistent NH3 concentrations due to emissions from the anthropogenic (agricultural) source regions, such as South Asia (India/Pakistan), China, the United States (US), parts of Europe, Southeast (SE) Asia (Thailand/Myanmar/Laos), the central portion of South America, as well as Western and Northern Africa. These correspond primarily to irrigated croplands, as well as regions with heavy precipitation, with extensive animal feeding operations and fertilizer applications where a summer maximum and a secondary spring maximum are reliably observable. In the Southern Hemisphere (SH) regular agricultural fires contribute to a spring maximum. Regions of strong episodic emissions include Russia and Alaska as well as parts of South America, Africa, and Indonesia. Biomass burning, especially wildfires, dominate these episodic NH3 high concentrations.
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Global increasing of atmospheric methane since 2007-2008 after a decade of its stability requires its investigation and explanation. Locations and nature of growing methane sources are still under discussion. Recent warming of the Arctic stimulated speculations about dissociation of methane hydrates in the Arctic seabed and a new climatic positive feedback. Unfortunately, regular measurements of methane concentrations over the surface of the Arctic Ocean are lacking. Satellite methane retrievals obtained at the Thermal IR (TIR) spectral region are possible year round, day and night. In this paper methane low tropospheric satellite retrievals over the Arctic Ocean from spectrometers using the band near 1300 cm-1 were analyzed. There have been found favorable and unfavorable areas and periods for satellite TIR measurements. Temperature contrast, defined here as the temperature difference between the surface and the altitude of 4 km, was used as a parameter characterizing sensitivity to the lower troposphere: data with the temperature contrast less than 10°C were discarded as unrepresentative for the lower troposphere. Maximal positive methane anomalies were observed along coasts of Norway, Novaya Zemlya, and Spitsbergen in November - December. According to preliminary estimates, the seas of the Western Arctic are responsible for ~68% of total emission from the Arctic Ocean. East Siberian Arctic Shelf (ESAS) contributes ~12% of marine emission in the Arctic. Arctic Ocean methane emission comprise ~68% of the Arctic land emission to the North from 60° N. Satellite data since 2002 do not confirm conclusively a decisive role of the Arctic Ocean sources for the global CH4 acceleration after 2007. © 2016, Space Research Institute of the Russian Academy of Sciences. All rights reserved.
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The wealth of air quality information provided by satellite infrared observations of ammonia (NH3), carbon monoxide (CO), formic acid (HCOOH), and methanol (CH3OH) is currently being explored and used for a number of applications, especially at regional or global scales. These applications include air quality monitoring, trend analysis, emissions, and model evaluation. This study provides one of the first direct validations of Tropospheric Emission Spectrometer (TES) satellite-retrieved profiles of NH3, CH3OH, and HCOOH through comparisons with coincident aircraft profiles. The comparisons are performed over the Canadian oil sands region during the intensive field campaign (August–September, 2013) in support of the Joint Canada–Alberta Implementation Plan for Oil Sands Monitoring (JOSM). The satellite/aircraft comparisons over this region during this period produced errors of (i) +0.08 ± 0.25 ppbv for NH3, (ii) +7.5 ± 23 ppbv for CO, (iii) +0.19 ± 0.46 ppbv for HCOOH, and (iv) −1.1 ± 0.39 ppbv for CH3OH. These values mostly agree with previously estimated retrieval errors; however, the relatively large negative bias in CH3OH and the significantly greater positive bias for larger HCOOH and CO values observed during this study warrant further investigation. Satellite and aircraft ammonia observations during the field campaign are also used in an initial effort to perform preliminary evaluations of Environment Canada's Global Environmental Multi-scale – Modelling Air quality and CHemistry (GEM-MACH) air quality modelling system at high resolution (2.5 × 2.5 km2). These initial results indicate a model underprediction of ~ 0.6 ppbv (~ 60 %) for NH3, during the field campaign period. The TES/model CO comparison differences are ~ +20 ppbv (~ +20 %), but given that under these conditions the TES/aircraft comparisons also show a small positive TES CO bias indicates that the overall model underprediction of CO is closer to ~ 10 % at 681 hPa (~ 3 km) during this period.
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Localized anthropogenic sources of atmospheric CH4 are highly uncertain and temporally variable. Airborne remote measurement is an effective method to detect and quantify these emissions. In a campaign context, the science yield can be dramatically increased by real-time retrievals that allow operators to coordinate multiple measurements of the most active areas. This can improve science outcomes for both single- and multiple-platform missions. We describe a case study of the NASA/ESA CO2 and Methane Experiment (COMEX) campaign in California during June and August/September 2014. COMEX was a multi-platform campaign to measure CH4 plumes released from anthropogenic sources including oil and gas infrastructure. We discuss principles for real-time spectral signature detection and measurement, and report performance on the NASA Next Generation Airborne Visible Infrared Spectrometer (AVIRIS-NG). AVIRIS-NG successfully detected CH4 plumes in real-time at Gb s−1 data rates, characterizing fugitive releases in concert with other in situ and remote instruments. The teams used these real-time CH4 detections to coordinate measurements across multiple platforms, including airborne in situ, airborne non-imaging remote sensing, and ground-based in situ instruments. To our knowledge this is the first reported use of real-time trace gas signature detection in an airborne science campaign, and presages many future applications.
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A long-term and comprehensive emission monitoring study was conducted at a large U.S. Midwest dairy farm. The monitoring effort was part of a national monitoring study that included swine, dairy, and poultry operations. The monitored farm was a 3400-cow operation. Monitoring of greenhouse gases (GHG) was conducted in two freestall barns and milking center for 28 months. The monitoring setup and equipment installation followed an approved site monitoring plan, a quality assurance project plan, and instrument or method-specific standard operating procedures. Gas concentrations, ventilation controllers, temperature and relative humidity, barn static pressure, and weather conditions were continuously monitored. In addition, animal inventory, mass, density, and milk production were recorded. As many as 563 valid daily mean data were obtained for each of the methane and carbon dioxide emissions between September 2007 and February 2010, and 98 daily means of valid nitrous oxide measurements that began on September 2009. The average daily mean (±SD) cow-specific emissions from identical freestall barns 1 and 2 were 12.6±1.9 and 12.1±2.0 kg d-1 hd-1, 373±80 and 356±74 g d-1 hd-1, and 564±919 and 551±852 mg d-1 hd-1 for carbon dioxide, methane, and nitrous oxide, respectively. Emissions were also normalized to individual cows, and units of floor area, milk production, and live mass. Methane and nitrous oxide contributed 42% and 0.7% to the total emissions of carbon dioxide equivalents (CO2 e). The total CO2 e emission rates (including the milking center) were 25.57 and 24.86 kg d-1 hd-1 for barns 1 and 2, respectively. Characteristics of the GHG emissions are presented and compared with the literature.
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In order to optimize the Phellinus Linteus fermentation process, the fermentation temperature, the inoculum size, the rotation speed and the bottling capacity have been regarded as the independent variables and the fermentation yield has been considered as the dependent variable. The quadratic regression orthogonal rotating combination design method has been adopted to build the model for Phellinus Linteus fermentation process. And this model has been also analyzed in this paper. The results have shown that the most important factors which affect the fermentation yield include the fermentation temperature, the inoculum size, the rotation speed and the bottling volume. There exists the significant interaction between the inoculum size and the bottling volume. The optimal fermentation conditions of Phellinus Linteus are: the bottling volume is 120mL, the inoculum size is 17mL, the temperature is 26°C and the rotation speed is 135r/min. At this time, the theoretical extreme value of fermentation mycelium production is 24.51mg/mL. The experimental results have shown that the model fits well with the actual situation and the credibility is higher.
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We use the estimated lifetime of methane (CH4), the current methane concentration, and its annual growth rate to calculate the global methane emission rate. The upper and lower limits of the annual global methane emission rate, depending on loss of CH4 into the stratosphere and methane consuming bacteria, amounts to 648.0 Mt a-1 and 608.0 Mt a-1. These values are in reasonable agreement with satellite and with much more accurate in situ measurements of methane. We estimate a mean tropospheric and mass-weighted temperature related to the reaction rate and employ a mean OH-concentration to calculate a mean methane lifetime. The estimated atmospheric lifetime of methane amounts to 8.28 years and 8.84 years, respectively. In order to improve the analysis a realistic 3D-calculations should be performed.
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[1] Airborne observations from the CalNex campaign in May and June 2010 are used to investigate the role of ammonia (NH3) in fine particulate matter (PM2.5) formation and surface air quality in California and test the key processes relevant to inorganic aerosol formation in the GEOS-Chem model. Concentrations of ammonia throughout California, sulfur dioxide (SO2) in the Central Valley, and ammonium nitrate in the Los Angeles (LA) area are underestimated several-fold in the model. We find that model concentrations are relatively insensitive to uncertainties in gas-particle partitioning and deposition processes in the region. Conversely, increases to anthropogenic livestock ammonia emissions (by a factor of 5) and anthropogenic sulfur dioxide emissions in the Central Valley (by a factor of 3 - 10) and a reduction of anthropogenic NOx emissions (by 30 %), substantially reduces the bias in the simulation of gases (SO2, NH3, HNO3) throughout California and PM2.5 near LA, although the exact magnitudes of emissions in the region remain uncertain. Using these modified emissions, we investigate year-round PM2.5 air quality in California. The model reproduces the wintertime maximum in surface ammonium nitrate concentrations in the Central Valley (regional mean concentrations are 3 times higher in December than in June), associated with lower planetary boundary layer heights and colder temperatures, and the wintertime minimum in the LA region (regional mean concentrations are 2 times higher in June than December) associated with ammonia-limitation. Year-round, we attribute at least 50 % of the inorganic PM2.5 mass simulated throughout California to anthropogenic ammonia emissions.
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Significance Successful regulation of greenhouse gas emissions requires knowledge of current methane emission sources. Existing state regulations in California and Massachusetts require ∼15% greenhouse gas emissions reductions from current levels by 2020. However, government estimates for total US methane emissions may be biased by 50%, and estimates of individual source sectors are even more uncertain. This study uses atmospheric methane observations to reduce this level of uncertainty. We find greenhouse gas emissions from agriculture and fossil fuel extraction and processing (i.e., oil and/or natural gas) are likely a factor of two or greater than cited in existing studies. Effective national and state greenhouse gas reduction strategies may be difficult to develop without appropriate estimates of methane emissions from these source sectors.
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Livestock constitutes an integral component of Indian agriculture sector and also a major source of GHGs emissions. The study presents a detailed inventory of GHG emissions at district/state level from different age-groups, indigenous and exotic breed of different Indian livestock categories estimated using the recent census 2003 and country-specific emission coefficients based on IPCC guidelines. The total methane emission including enteric fermentation and manure management of livestock was estimated at 11.75 Tg/year for the year 2003. Enteric fermentation constitutes ~91 % of the total methane emissions from Indian livestock. Dairy buffalo and indigenous dairy cattle together contribute 60 % of the methane emissions. The total nitrous oxide emission from Indian livestock for the year 2003 is estimated at 1.42 Gg/year, with 86.1 % contribution from poultry. The total GHGs emission from Indian livestock is estimated at 247.2 Mt in terms of CO2 equivalent emissions. Although the Indian livestock contributes substantially to the methane budget, the per capita emission is only 24.23 kgCH4/animal/year. Using the remote sensing derived potential feed/fodder area available for livestock, the average methane flux was calculated as 74.4 kg/ha. The spatial patterns derived in GIS environment indicated the regions with high GHGs emissions that need to be focused subsequently for mitigation measures. The projected estimates indicate a likely increase of 40 % in methane emissions from buffalo population.
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■ This article presents an overview of the theoretical and practical issues associated with the development, analysis, and application of detection algorithms to exploit hyperspectral imaging data. We focus on techniques that exploit spectral information exclusively to make decisions regarding the type of each pixel—target or nontarget—on a pixel-by-pixel basis in an image. First we describe the fundamental structure of the hyperspectral data and explain how these data influence the signal models used for the development and theoretical analysis of detection algorithms. Next we discuss the approach used to derive detection algorithms, the performance metrics necessary for the evaluation of these algorithms, and a taxonomy that presents the various algorithms in a systematic manner. We derive the basic algorithms in each family, explain how they work, and provide results for their theoretical performance. We conclude with empirical results that use hyperspectral imaging data from the HYDICE and Hyperion sensors to illustrate the operation and performance of various detectors.
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Adsorption of dynamically diluted ammonia at part-per-billion to low part-per-million concentrations in dry nitrogen was studied with treated and non-treated stainless steel and polymer test tubes. The treatments included electropolishing and two types of coatings based on amorphous silicon. Cavity ring-down spectroscopy with an external cavity diode laser operating in the near-infrared wavelength range was used to monitor the adsorption process in real time in continuous-flow conditions to obtain quantitative assessment of the adsorptive properties of the studied surfaces. The investigated polymers were all less adsorptive than any of the treated or non-treated stainless steel surfaces. Some of the commercial coatings reduced the adsorption loss of stainless steel by a factor of ten or more. Polyvinylidene fluoride was found to be superior (less adsorption) to the four other studied polymer coatings. The number of adsorbed ammonia molecules per surface area obtained at different ammonia gas phase concentrations was modeled with Langmuir and Freundlich isotherms. The time behavior of the adsorption–desorption process occurring in the time scale of seconds and minutes was simulated with a simple kinetic model.
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Anthropogenic emissions of NOx (nitric oxide (NO) + nitrogen dioxide (NO2)), which in sunlight can be oxidized to form nitric acid (HNO3), can react with ammonia (NH3) to form ammonium nitrate particles. Ammonium nitrate formation was observed from the NOAA WP-3D aircraft over Houston during the 2006 Texas Air Quality Study with fast-response measurements of NH3, HNO3, particle composition, and particle size distribution. Typically, NH3 mixing ratios over the urban area ranged from 0.2 to 3 ppbv and were predominantly from area sources. No NH3 enhancements were observed in emission plumes from power plants. The few plumes with high NH3 levels from point source emissions that were sampled are analyzed in detail. While the paucity of NH3 data in emission inventories made point source identification difficult, one plume was traced to NH3 release from an industrial accident. NH3 mixing ratios in these plumes ranged from 5 to 80 ppbv. In these plumes, the NH3 enhancement correlated with a decrease in HNO3 mixing ratio and an increase in particulate NO3- concentration indicating ammonium nitrate formation. The ammonium nitrate aerosol mass budget in the plumes was analyzed to assess the quantitative agreement between the gas and aerosol phase measurements. The thermodynamic equilibrium between the gas and aerosol phase was examined for one flight by comparing the modeled dissociation constant for ammonium nitrate with NH3 and HNO3 measurements. The high levels of NH3 in these plumes shifted the equilibrium toward favorable thermodynamic conditions for the condensation of ammonium nitrate onto particles.
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The doubling of atmospheric methane (CH4) during the twentieth century due largely to growth in anthropogenic emissions has made CH4 the second largest contributor behind carbon dioxide to anthropogenic forcing of climate change. However, the global CH4 budget and its decadal evolution remain poorly quantified despite re-evaluations that include the IPCC Fourth Assessment Report. Potentially, the aggregation of national anthropogenic emission inventories as reported to the United Nations Framework Convention on Climate Change could document the changing anthropogenic emission since 1990, as could other “bottom–up” inventories such as EDGAR. As an examination of the recent CH4 budget evolution, we compare two constructions of CH4 source history, one based on an aggregation of national emission inventories, the other version 4 of EDGAR, each in combination with alternative natural CH4 emissions, for consistency with observed atmospheric mixing ratio and carbon isotope content (δC(CH4)). We conclude that despite the utility of isotopic constraints on budget evolution, the level of uncertainty in sink strengths and their isotopic fractionation limits the confidence in constructing anthropogenic emission histories over recent decades.
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Eleven instruments for the measurement of ambient concentrations of atmospheric ammonia gas (NH3), based on eight different measurement methods were inter-compared above an intensively managed agricultural field in late summer 2008 in S. Scotland. To test the instruments over a wide range of concentrations, the field was fertilised with urea midway through the experiment, leading to an increase in the average concentration from 10 to 100 ppbv. The instruments deployed included three wet-chemistry systems, one with offline analysis (annular rotating batch denuder, RBD) and two with online-analysis (Annular Denuder sampling with online Analysis, AMANDA; AiRRmonia), two Quantum Cascade Laser Absorption Spectrometers (a large-cell dual system, DUAL-QCLAS, and a compact system, c-QCLAS), two photo-acoustic spectrometers (WaSul-Flux, Nitrolux-100), a Cavity Ring Down Spectrosmeter (CRDS), a Chemical Ionisation Mass Spectrometer (CIMS), an ion mobility spectrometer (IMS) and an Open-Path Fourier Transform Infra-Red (OP-FTIR) spectroscopy. Each instrument was compared with each other and with the average concentration of all instruments. An overall good agreement of hourly average concentrations between the instruments (R2>0.84), was observed for NH3 concentrations at the field of up to 120 ppbv with the slopes against the average ranging from 0.67 (DUAL-QCLAS) to 1.13 (AiRRmonia) with intercepts of –0.74 ppbv (RBD) to +2.69 ppbv (CIMS). More variability was found for performance for lower concentrations (
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An integration method is proposed to get a particular solution for second order linear differential equations, with constant coefficients. If the equation y″ + py′ + qy = f(x) has two real characteristic roots, and one of them is given as λ, a particular solution can be got from twice integration directly and repressed as y*= exp(- (λ + p)x)[∫ (exp((2λ + p)x)∫a(x)dx)dx] . When two roots are equal, the particular solution has more concise form. The most important is that the method given in this article can be used in equations with different inhomogeneous terms, involving the two types of functions explained in the text book, and other nonlinear functions.
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Mixtures of O3 and excess NH3 react at 30° C to produce O2, H20, N2O, N2, and solid NH4NO3. The amounts of the gas phase products, relative to the ozone consumed, are 1.05, 0.31, 0.032, and 0.031, respectively. Neither H2 nor NH4NO2 was produced. For [NH3]/[O3]0 ratios < 50, the disappearance rate of O3 was first order in [O3] and increased slowly with increasing [NH3]/[O3]0 to an upper limiting value of 0.21 min-1, where [O3]0 is the initial pressure of O3. As the reaction proceeded and the [NH3]/[O3] ratio passed 120 (or if [NH3]/[O3]0 > 120), the rate shifted to three halves order in [O3] and was proportional to [NH3](-1/2). The reaction is interpreted as a chain mechanism with the heterogeneous decay of O3 as the initiating step. Nitrogenous products come from oxidation of HNO with O3, followed by reaction with NH3.
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Agricultural ammonia (NH3) emissions are highly uncertain, with high spatio-temporal variability and a lack of widespread in-situ measurements. Regional NH3 emission estimates with mass-balance or emission ratio approaches are uncertain due to variable NH3 sources and sinks as well as unknown plume correlations with other dairy source tracers. We characterize the spatial distributions of NH3 and methane (CH4) dairy plumes using in-situ surface and airborne measurements in the Tulare dairy feedlot region of the San Joaquin Valley, California during the NASA DISCOVER-AQ 2013 field campaign. Surface NH3 and CH4 mixing ratios exhibit large variability with maxima localized downwind of individual dairy feedlots. The geometric mean NH3:CH4 enhancement ratio derived from surface measurements is 0.15 ± 0.03 ppmv ppmv−1. Individual dairy feedlots with spatially distinct NH3 and CH4 source pathways led to statistically significant correlations between NH3 and CH4 in only 68% of the 69 downwind plumes sampled. At longer sampling distances, NH3:CH4 enhancement ratio decreases of at least 20-30% suggest the potential for NH3 deposition as a loss term for plumes within a few kilometers downwind of feedlots. Aircraft boundary layer transect measurements directly above surface mobile measurements in the dairy region show comparable gradients and geometric mean enhancement ratios within measurement uncertainties,even when including NH3 partitioning to sub-micron particles. Individual NH3 and CH4 plumes sampled at close proximity where losses are minimal are not necessarily correlated due to lack of mixing and distinct source pathways. Our analyses have important implications for constraining NH3 sink and plume variability influences on regional NH3 emission estimates and for improving NH3 emission inventory spatial allocations.
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In recent years, methane (CH4) has received increasing scientific attention because it is the most abundant non-CO2 atmospheric greenhouse gas (GHG) and controls numerous chemical reactions in the troposphere and stratosphere. However, there is much that is unknown about CH4 sources and sinks and their evolution over time. Here we show that near-surface cavities in the uppermost vadose zone are now actively removing atmospheric CH4. Through seasonal geochemical tracing of air in the atmosphere, soil and underground at diverse geographic and climatic locations in Spain, our results show that complete consumption of CH4 is favoured in the subsurface atmosphere under near vapour-saturation conditions and without significant intervention of methanotrophic bacteria. Overall, our results indicate that subterranean atmospheres may be acting as sinks for atmospheric CH4 on a daily scale. However, this terrestrial sink has not yet been considered in CH4 budget balances.
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Five different types of tubing materials, namely, polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP), high density polyethylene (HDPE), and polyvinyl chloride (PVC) were evaluated for ammonia adsorption at two nominal ammonia concentration values (1 and 10ppm) at similar to 24 degrees C. All tubing sections were 2.5 m in length and 4.76 mm in i.d. except the HDPE which had an i.d. of 4.32 mm. Mass balance was used to determine ammonia (as ammonium-nitrogen (N)) adsorbed on the inside of the tubing versus the total N recovered in the tubing plus the gas scrubbers (primary and secondary). No tubing significantly differed in N adsorption. Averaged for both ammonia concentrations, N adsorption as percent of total N ranged from 0.15% (PVC) to 1.69% (FEP). Hence, the least expensive PVC tubing may represent the best option under conditions similar to those used in this study. The gas scrubber design used in this study had excellent trapping efficiency (> 99%).
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The Toxic Substances Control Act Chemical Substance Inventory lists >84,000 chemicals used in commerce (http://www.epa.gov/oppt/existingchemicals/pubs/tscainventory/basic.html). With chemicals having a multitude of uses, persons are potentially at risk daily for exposure to chemicals as a result of an acute chemical incident (lasting <72 hours). Depending on the level of exposure and the type of chemical, exposure can result in morbidity and, in some cases, mortality. 1999-2008. The Hazardous Substances Emergency Events Surveillance (HSEES) system was operated by the Agency for Toxic Substances and Disease Registry during January 1991-September 2009 to collect data that would enable researchers to describe the public health consequences of chemical incidents and to develop activities aimed at reducing the harm from such incidents. This report identifies the top five chemicals that caused injuries in the nine states (Colorado, Iowa, Minnesota, New York, North Carolina, Oregon, Texas, Washington, and Wisconsin) that participated in HSEES during its last 10 full years of data collection (1999-2008). Of the 57,975 incidents that were reported, 54,989 (95%) involved the release of only one chemical. The top five chemicals associated with injury were carbon monoxide (2,364), ammonia (1,153), chlorine (763), hydrochloric acid (326), and sulfuric acid (318). Carbon monoxide and ammonia by far caused the most injuries, deaths, and evacuations. Chlorine, while not in the top 10 chemicals released, was in the top five chemicals associated with injury because of its hazardous properties. Multiple measures can be taken to prevent injuries associated with the top five chemicals. Because many carbon monoxide releases occur in residential settings, use of carbon monoxide detectors can prevent injuries. Substituting chemicals with less lethal alternatives can result in mitigating injuries associated with ammonia. Routine maintenance of equipment and engineering controls can reduce injuries associated with chlorine and sulfuric acid, and proper chemical handling training can reduce injuries associated with hydrochloric acid. Public Health Implications: Understanding the most frequently reported locations where carbon monoxide, ammonia, chlorine, hydrochloric acid, and sulfuric acid are released along with the most frequently reported contributing factors can help mitigate injuries associated with these releases. Prevention initiatives should focus on educating the public and workers about the dangers of these chemicals and about proper handling of these chemicals along with routine maintenance of equipment.
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Different types of tubing and operating conditions may be involved when measuring ammonia (NH3) concentrations and its emissions from animal production facilities. Prices of commercially available tubing vary substantially. A question that has often come up but has not been well investigated is how the tubing type (e.g., PVC vs. FEP) may impact the certainty of NH3 concentration measurement. The study reported here was conducted to address this issue in that it assessed and compared the magnitude of NH3 adsorption to different types of commercially available tubing under conditions that may be present in animal feeding operation (AFO) air emission studies. The types of tubing evaluated were: Teflon (PFA and FEP tubing), HDPE (clear plastic tubing), and PVC (vinyl tubing). Each tested tubing had a length of 30.5 m (100 ft) and an inside diameter of 6.35 mm (0.25 in.). Five nominal NH3 levels of 10, 20, 40, 80, and 160 ppm, generated with poultry manure, were passed through the tested tubing at an airflow rate of 8 L min-1 (0.28 CFM) for 60 min. Simultaneous measurements of NH3 concentrations at the inlet and outlet of the tested tubing were made with two photoacoustic gas spectrometers (1% repeatability of measured value and 0.2-ppm NH3 detection limit). Although the Teflon tubing had significantly lower NH3 adsorption than the HDPE or PVC tubing, all the tested tubing showed <3% NH3 differences between the inlet and outlet concentrations after the 60-min exposure and mostly <1% for NH3 levels >40 ppm. The results of this study thus suggest that the HDPE and PVC tubing offer viable, more economical air sampling options for AFO NH3 emission studies. © 2012 American Society of Agricultural and Biological Engineers.
Article
Ammonia (NH3) and carbon monoxide (CO) are primary pollutants emitted to the Earth's atmosphere from common as well as distinct sources associated with anthropogenic and natural activities. The seasonal and global distributions and correlations of NH3 and CO from the Tropospheric Emission Spectrometer (TES) satellite observations and GEOS-Chem model simulations for 2007 are investigated to evaluate how well the global and seasonal pollutant sources are prescribed in the model. Although the GEOS-Chem simulations of NH3 and CO atmospheric mixing ratio values are lower than the TES satellite observations, the global distribution patterns from the model reasonably agree with the observations, indicating that the model represents the general location of the source regions and the seasonal enhancements of NH3 and CO globally over large regional scales. In regions and seasons where biomass burning is the dominant source of both NH3 and CO emissions into the atmosphere, there are strong NH3:CO correlations, which is consistent with the relationship demonstrated by surface measurements over fires. In regions where the enhanced NH3 and CO are known to be produced by different sources, the NH3:CO correlations from TES observations and model simulations are weak or non-existent. For biomass burning regions the NH3:CO ratios are 0.015 (TES) and 0.013 (GEOS-Chem). In regions of high-population density, known heavy traffic, and limited biomass burning sources, such as the rapidly developing areas of South Asia and northern China, which include mixtures of megacities, industrial, and agricultural areas, the two species show weaker but still positive correlations and NH3:CO ratios of 0.051 (TES) and 0.036 (GEOS-Chem). These enhancement ratios of NH3 relative to CO are useful in constraining NH3 emission inventories when CO emission inventories are better known for some events or regions (i.e. biomass burning).
Article
Airborne thermal-infrared (TIR) imaging spectrometry techniques have been used to detect and track methane and other gaseous emissions from a variety of discrete sources in diverse environmental settings, and to enable estimation of the strength of each plume. The high spatial resolution (1–2 m) permits attribution of chemical plumes to their source, while the moderate spectral resolution (44 nm across the 7.5–13.5 μm TIR band) enables identification and quantification of the gaseous plume constituents, even when one is present in considerably greater concentration than the others. Raw imagery was quantitatively analyzed using matched filtering and adaptive coherence techniques. Experiments under controlled conditions demonstrated successful detection of methane point sources at release rates as low as 2.2 kg/h (~ 1 dm3/s at NTP).
Article
Monitoring ammonia (NH3) concentrations on a global to regional scale is a challenge. Due to the limited availability of reliable ground-based measurements, the determination of NH3 distributions generally relies on model calculations. Novel remotely sensed NH3 burdens provide valuable insights to complement traditional assessments. This paper presents a first quantitative comparison between IASI satellite observations and LOTOS-EUROS model results over Europe and Western Russia. A methodology to account for the variable retrieval sensitivity of the measurements is described. Four years of data (2008-2011) highlight three main agricultural hotspot areas in Europe: the Po Valley, the continental part of Northwestern Europe and the Ebro Valley. The spatial comparison reveals a good overall agreement of the NH3 distributions in these source regions but also over remote areas and over sea when transport is observed. On average, the measured columns exceed the modeled ones, except for a few cases. Large discrepancies over several industrial areas in Eastern Europe and Russia point to underestimated emissions in the underlying inventories. The temporal analysis over the three hotspot areas reveals that the seasonality is well captured by the model when the lower sensitivity of the satellite measurements in the colder months is taken into account. Comparison of the daily time series indicates possible misrepresentations of the timing and magnitude of the emissions. Finally, specific attention to biomass burning events shows that modeled plumes are less spread out than the observed ones. This is confirmed for the 2010 Russian fires with a comparison using in-situ observations.
Article
Ammonia (NH3) is a key precursor species to atmospheric fine particulate matter, with strong implications for regional air quality and global climate change. NH3 from vehicles accounts for a significant fraction of total emissions of NH3 in urban areas. A mobile platform is developed to measure NH3, CO, and CO2 from the top of a passenger car. The mobile platform conducted 87 hours of on-road measurements, covering 4500 km in New Jersey and California. The average on-road emission factor (EF) in CA is 0.49±0.06 g NH3 per kg fuel and agrees with previous studies in CA (0.3-0.8 g/kg). The mean on-road NH3:CO emission ratio is 0.029±0.005, and there is no systematic difference between NJ and CA. On-road NH3 EFs increase with road gradient by an enhancement of 53 mg/kg fuel per percentage of gradient. On-road NH3 EFs show higher values in both stop-and-go driving conditions and freeway speeds with a minimum near 70 km/h. Consistent with prior studies, the on-road emission ratios suggest a highly skewed distribution of NH3 emitters. Comparisons with existing NJ and CA on-road emission inventories indicate that there may be an underestimation of on-road NH3 emissions in both NJ and CA. We demonstrate that mobile, open-path measurements provide a unique tool to help quantitatively understand the on-road NH3 emissions in urban and suburban settings.
Article
We use a model of agricultural sources of ammonia (NH3) coupled to a chemical transport model to estimate the impact of U.S. food export on particulate matter concentrations (PM2.5). We find that food export accounts for 11% of total U.S NH3 emissions (13% of agricultural emissions) and that it increases the population-weighted exposure of the U.S. population to PM2.5 by 0.36 μgm-3 on average. Most of the increase is from particulate nitrate, reflecting the interplay between agricultural (NH3) and combustion emissions (NO, SO2). Eliminating NH3 emissions from food export would achieve greater health benefits than the reduction of the National Ambient Air Quality Standards for PM2.5 from 15 to 12μgm-3. Valuation of the increased premature mortality associated with PM2.5 from food export (36 billion US$ per year) amounts to 54% of the gross food export value. Livestock operations in densely populated areas have particularly large health costs. Decreasing SO2 and NOx emissions will indirectly reduce health impact of food export as an ancillary benefit.
Article
The potent greenhouse gas, methane, CH4, originates from a wide range of anthropogenic and natural sources. A ground-based, satellite-scale, transcontinental (Florida to California) survey was conducted to understand better emissions from key sources including wetlands, forest fire, and geologic sources, as well as to acquire desert background values and lower atmosphere vertical profiling in the San Bernardino Mountains. A total of 6600 measurements along 7020 km of roadways were made by flame ion detection, gas chromatography (GC) onboard a recreational vehicle in 2010, and during a second survey with a cavity ring-down spectrometer system in Southern California in 2012. Significant vibration reduction efforts allowed near continuous mobile GC measurements.Nocturnal CH4 measurements tended to be higher compared to daytime values, sometime significantly, for similar sources and were concluded due to day/night meteorological differences. The lowest GC observations were 1.80 ppm, observed in the California desert, ∼60 ppb less than minimum desert CH4 observed in 2012. Thanks to smoke visualization of a brush fire plume, the flux from the fire was estimated at 0.15 kiloton day−1. Geologic CH4 emissions from the La Brea tar pit and surrounding areas were surprisingly strong, with peak concentrations of nearly 50 ppm and highly elevated CH4 concentrations extending over at least ∼100 km2, and accounting potentially for a significant fraction of the LA basin CH4 emissions. Geologic CO2 emissions also were observed.
Major aspects of the circulation through the atmospheric environment of a number of gaseous nitrogen pollutants have been estimated, including source magnitudes, residual atmospheric concentrations, and scavenging processes. The compounds considered include the major nitrogen oxide pollutants, as well as ammonia and nitrous oxide. Background concentrations of the various nitrogen compounds have been estimated. In the global atmospheric nitrogen cycle, pollutant emissions of NO2 play only a minor role relative to the natural sources. The atmospheric nitrogen cycle is apparently dominated by natural emissions of ammonia, nitric oxide, and nitrous oxide. Scavenging mechanisms for removing nitrogen compounds from the atmosphere include surface reactions, the formation of nitrate and ammonium aerosols, and the biological reduction of nitrous oxide. Photochemical processes in the stratosphere are well known in the nitrous oxide cycle, but they appear to be less important than biological processes.
Article
We examined how adsorption and desorption of gases from inlets and a cell could affect the accuracy of closed-cell FTIR measurements of carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), nitric oxide (NO), nitrogen dioxide (NO2), methanol (CH3OH), acetic acid (CH3COOH), and ammonia (NH3). When standards were delivered to the cell through a stainless steel inlet, temporarily reduced transmission was observed for CH3OH and NH3. However, a halocarbon wax coated inlet (normally used on the system) had excellent transmission (comparable to room temperature Teflon) for both CH3OH and NH3, even at temperatures as low as 5°C. Thus the wax is valuable for coating sampling system components that cannot be fashioned from Teflon. The instrument had a delayed response (~10-40 s) for NH3 only, which was attributed to passivation of the Pyrex multipass cell. To determine sampling artifacts that could arise from the complex sample matrix presented by smoke, the closed-cell FTIR system was intercompared with an open-path FTIR system (which is immune to sampling artifacts) in well-mixed smoke. A similar cell passivation delay for NH3 was the only artifact found in this test. Overall, the results suggest that ~10 s is sufficient to detect >80% of an NH3/CO ratio sampled by our fast-flow, closed-cell system. Longer sampling times or consecutive samples return better results. In field campaigns the closed-cell system sampling times were normally 10 to >100 s so NH3 was probably underestimated by 5-15%.
Article
A new ammonia (NH3) analyzer was developed based on off-axis integrated cavity output spectroscopy. Its feasibility was demonstrated by making tropospheric measurements in flights aboard the Department of Energy Gulfstream-1 aircraft. The ammonia analyzer consists of an optical cell, quantum-cascade laser, gas sampling system, control and data acquisition electronics, and analysis software. The NH3 mixing ratio is determined from high-resolution absorption spectra obtained by tuning the laser wavelength over the NH3 fundamental vibration band near 9.67 μm. Excellent linearity is obtained over a wide dynamic range (0 - 101 ppbv) with a response time (1/e) of 2 Hz and a precision of ±90 pptv (1σ in 1 s). Two research flights were conducted over the Yakima Valley in Washington State. In the first flight, the ammonia gas sensor was used to identify signatures of livestock from local dairy farms with high vertical and spatial resolution under low wind and calm atmospheric conditions. In the second flight, the NH3 spectrometer captured livestock emission signals under windy conditions. Our results demonstrate that this new ammonia spectrometer is capable of providing fast, precise, and accurate in situ observations of ammonia aboard airborne platforms to advance our understanding of atmospheric compositions and aerosol formation.
Article
The aerosol producing reaction between ammonia and sulfur dioxide was studied experimentally in a concentric flow reactor. The reactions were conducted at NH3 to SO2 reactant ratios of 7:1, 1:1, and 1:7, with reactant concentrations ranging from 950 ppm to 16 200 ppm. Only trace amounts of water vapor (≤10 ppm) were present, and all reactions were carried out at 25°C and atmospheric pressure. The reaction proceeded at significant rates, even at the lower concentrations, apparently producing two solid compounds. Results of chemical analyses showed that changes in the NH3 to SO2 ratio in the solid product roughly corresponded to similar changes in the same ratio in the gas phase. Particle sizes up to 7.5 μm were measured, but the majority of the aerosol particles were in the submicron range. Classical nucleation theory indicates that ammonium amido sulfite ((NH3)2·SO2) may be significantly less volatile than amidosulfurous acid (NH3·SO2) at these conditions. Thus the sulfite is the favored reaction product except when large excesses of sulfur dioxide are present.