scholarly journals An investigation into the chemistry of HONO in the marine boundary layer at Tudor Hill Marine Atmospheric Observatory in Bermuda

2021 ◽  
Author(s):  
Yuting Zhu ◽  
Youfeng Wang ◽  
Xianliang Zhou ◽  
Yasin Elshorbany ◽  
Chunxiang Ye ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Long Range ◽  
Forest Canopy ◽  
Marine Boundary Layer ◽  
Temporal Variations ◽  
Pollutant Emissions ◽  
Present Measurement ◽  
Photochemical Processes ◽  
Solar Noon ◽  
Marine Air

Abstract. Here we present measurement results of temporal distributions of nitrous acid (HONO) along with several chemical and meteorological parameters during the spring and the late summer of 2019 at Tudor Hill Marine Atmospheric Observatory in Bermuda. Large temporal variations in HONO concentration were controlled by several factors including local pollutant emissions, air mass interaction with the island, and long-range atmospheric transport of HONO precursors. In polluted plumes emitted from local traffic, power plant and cruise ship emissions, HONO and nitrogen oxides (NOx) existed at substantial levels (up to 278 pptv and 48 ppbv, respectively) and NOx-related reactions played dominant roles in daytime formation of HONO. The lowest concentration of HONO was observed in marine air, with median concentrations at ~3 pptv around solar noon and < 1 pptv during the nighttime. Considerably higher levels of HONO were observed during the day in the low-NOx island-influenced air ([NO2] < 1 ppbv), with a median HONO concentration of ~17 pptv. HONO mixing ratios exhibited distinct diurnal cycles that peaked around solar noon and were lowest before sunrise, indicating the importance of photochemical processes for HONO formation. In clean marine air, NOx-related reactions contributed to ~35 % of the daytime HONO source and the photolysis of particulate nitrate (pNO3) can account for the missing source assuming a moderate enhancement factor of 30 relative to gaseous nitric acid photolysis. In low-NOx island-influenced air, the contribution from both NOx-related reactions and pNO3 photolysis accounted for only ~30 % of the daytime HONO production, and the photochemical processes on surfaces of the island, such as the photolysis of nitric acid on the forest canopy, might contributed significantly to the daytime HONO production. The concentrations of HONO, NOx and pNO3 were lower when the site was dominated by the aged marine air in the summer and were higher when the site was dominated by North American air in the spring, reflecting the effects of long-range transport on the reactive nitrogen chemistry in the background marine environments.

scholarly journals Measurements of ambient HONO concentrations and vertical HONO flux above a northern Michigan forest canopy

2012 ◽  
Vol 12 (17) ◽  
pp. 8285-8296 ◽  
Author(s):  
N. Zhang ◽  
X. Zhou ◽  
S. Bertman ◽  
D. Tang ◽  
M. Alaghmand ◽  
...  
Keyword(s):  
Measurement Technique ◽  
Forest Canopy ◽  
Sonic Anemometer ◽  
Flux Measurement ◽  
Measurement Systems ◽  
Ambient Concentration ◽  
Solar Noon ◽  
Absorption Photometer ◽  
Upward Flux ◽  
Northern Michigan

Abstract. Systems have been developed and deployed at a North Michigan forested site to measure ambient HONO and vertical HONO flux. The modified HONO measurement technique is based on aqueous scrubbing of HONO using a coil sampler, followed by azo dye derivatization and detection using a long-path absorption photometer (LPAP). A Na2CO3-coated denuder is used to generate "zero HONO" air for background correction. The lower detection limit of the method, defined by 3 times of the standard deviation of the signal, is 1 pptv for 1-min averages, with an overall uncertainty of ±(1 + 0.05 [HONO]) pptv. The HONO flux measurement technique has been developed based on the relaxed eddy accumulation approach, deploying a 3-D sonic anemometer and two HONO measurement systems. The overall uncertainty is estimated to be within ±(8 × 10−8 + 0.15 FHONO) mol m−2 h−1, with a 20-min averaged data point per 30 min. Ambient HONO and vertical HONO flux were measured simultaneously at the PROPHET site from 17 July to 7 August 2008. The forest canopy was found to be a net HONO source, with a mean upward flux of 0.37 × 10−6 moles m−2 h−1. The HONO flux reached a maximal mean of ~0.7 × 10−6 moles m−2 h−1 around solar noon, contributing a major fraction to the HONO source strength required to sustain the observed ambient concentration of ~70 pptv. There were no significant correlations between [NOx] and daytime HONO flux and between JNO2 × [NO2] and HONO flux, suggesting that NOx was not an important precursor responsible for HONO daytime production on the forest canopy surface in this low-NOx rural environment. Evidence supports the hypothesis that photolysis of HNO3 deposited on the forest canopy surface is a major daytime HONO source.

scholarly journals Measurements of ambient HONO concentrations and vertical HONO flux above a northern Michigan forest canopy

2012 ◽  
Vol 12 (3) ◽  
pp. 7273-7304 ◽  
Author(s):  
N. Zhang ◽  
X. Zhou ◽  
S. Bertman ◽  
D. Tang ◽  
M. Alaghmand ◽  
...  
Keyword(s):  
Measurement Technique ◽  
Forest Canopy ◽  
Sonic Anemometer ◽  
Flux Measurement ◽  
Rural Environment ◽  
Measurement Systems ◽  
Ambient Concentration ◽  
Solar Noon ◽  
Upward Flux ◽  
Northern Michigan

Abstract. Systems have been developed and deployed at a North Michigan forested site to measure ambient HONO and vertical HONO flux. The modified HONO measurement technique is based on aqueous scrubbing of HONO using a coil sampler, followed by azo dye derivatization and detection using an optical fiber spectrometer with a 1-m long path flow cell. A Na2CO3-coated denuder is used to generate "zero HONO" air for background correction. The lower detection limit of the method, defined by 3 times of the standard deviation of the signal, is 1 pptv for 2-min averages, with an overall uncertainty of ±(1 + 0.05 [HONO]) pptv. The HONO flux measurement technique has been developed based on the relaxed eddy accumulation approach, deploying a 3-D sonic anemometer and two HONO measurement systems. The overall uncertainty is estimated to be within ±(8 × 10−8 + 0.15 FHONO) mol m−2 h−1, with a 20-min averaged data point per 30 min. Ambient HONO and vertical HONO flux were measured simultaneously at the PROPHET site from 17 July to 7 August 2008. The forest canopy was found to be a net HONO source, with a mean upward flux of 0.37 × 10−6 moles m−2 h−1. The HONO flux reached a maximum mean of ~0.7 × 10−6 moles m−2 h−1 around solar noon, contributing a major fraction (~60%) to the HONO source strength required to sustain the observed ambient concentration of ~70 pptv. There was no significant correlation between NOx and daytime HONO flux, suggesting that NOx was not an important precursor responsible for HONO daytime production on the forest canopy surface in the low-NOx rural environment. Evidence suggests that photolysis of HNO3 deposited on the forest canopy surface is a major daytime HONO source.

scholarly journals Contributions of Trans-boundary Transport to the Summertime Air Quality in Beijing, China

2016 ◽  
Author(s):  
Jiarui Wu ◽  
Guohui Li ◽  
Junji Cao ◽  
Naifang Bei ◽  
Yichen Wang ◽  
...  
Keyword(s):  
Air Quality ◽  
Control Strategies ◽  
Dominant Role ◽  
Fine Particulate Matter ◽  
Temporal Variations ◽  
Pollutant Emissions ◽  
Beijing China ◽  
Local Emissions ◽  
Factor Separation ◽  
Good Agreement

Abstract. In the present study, the WRF-CHEM model is used to evaluate the contributions of trans-boundary transport to the air quality in Beijing during a persistent air pollution episode from 5 to 14 July 2015 in Beijing-Tianjin-Hebei (BTH), China. Generally, the predicted temporal variations and spatial distributions of PM2.5 (fine particulate matter), O3 (ozone), and NO2 are in good agreement with observations in BTH. The WRF-CHEM model also reproduces reasonably well the temporal variations of aerosol species compared to measurements in Beijing. The factor separation approach is employed to evaluate the contributions of trans-boundary transport of emissions outside of Beijing to the PM2.5 and O3 levels in Beijing. On average, in the afternoon during the simulation episode, the pure local emissions contribute 22.4 % to the O3 level in Beijing, less than 36.6 % from pure emissions outside of Beijing. The O3 concentrations in Beijing are decreased by 5.1 % in the afternoon due to interactions of local emissions with those outside of Beijing. The pure emissions outside of Beijing play a dominant role in the PM2.5 level in Beijing, with a contribution of 61.5 %, much more than 13.7 % from pure Beijing local emissions. The emissions interactions enhance the PM2.5 concentrations in Beijing, with a contribution of 5.9 %. Therefore, the air quality in Beijing is primarily determined by the trans-boundary transport of emissions outside of Beijing during summertime, showing that the cooperation with neighboring provinces to mitigate pollutant emissions is a key for Beijing to improve air quality. Considering the uncertainties in the emission inventory and the meteorological field simulations, further studies need to be performed to improve the WRF-CHEM model simulations to reasonably evaluate trans-boundary transport contributions to the air quality in Beijing for supporting the design and implementation of emission control strategies.

scholarly journals Hypertemporal Imaging Capability of UAS Improves Photogrammetric Tree Canopy Models

2020 ◽  
Vol 12 (8) ◽  
pp. 1238 ◽  
Author(s):  
Andrew Fletcher ◽  
Richard Mather
Keyword(s):  
Forest Canopy ◽  
Near Infrared ◽  
Spectral Band ◽  
Point Clouds ◽  
Tree Canopy ◽  
Solar Elevation ◽  
Spectral Bands ◽  
Eucalyptus Forest ◽  
Dense Point ◽  
Solar Noon

Small uncrewed aerial systems (UASs) generate imagery that can provide detailed information regarding condition and change if the products are reproducible through time. Densified point clouds form the basic information for digital surface models and orthorectified mosaics, so variable dense point reconstruction will introduce uncertainty. Eucalyptus trees typically have sparse and discontinuous canopies with pendulous leaves that present a difficult target for photogrammetry software. We examine how spectral band, season, solar azimuth, elevation, and some processing settings impact completeness and reproducibility of dense point clouds for shrub swamp and Eucalyptus forest canopy. At the study site near solar noon, selecting near infrared camera increased projected tree canopy fourfold, and dense point features more than 2 m above ground were increased sixfold compared to red spectral bands. Near infrared (NIR) imagery improved projected and total dense features two- and threefold, respectively, compared to default green band imagery. The lowest solar elevation captured (25°) consistently improved canopy feature reconstruction in all spectral bands. Although low solar elevations are typically avoided for radiometric reasons, we demonstrate that these conditions improve the detection and reconstruction of complex tree canopy features in natural Eucalyptus forests. Combining imagery sets captured at different solar elevations improved the reproducibility of dense point clouds between seasons. Total dense point cloud features reconstructed were increased by almost 10 million points (20%) when imagery used was NIR combining solar noon and low solar elevation imagery. It is possible to use agricultural multispectral camera rigs to reconstruct Eucalyptus tree canopy and shrub swamp by combining imagery and selecting appropriate spectral bands for processing.

Comparison of Modeled-to-Monitored PM2.5 Exposure Concentrations Resulting from Transportation Emissions in a Near-Road Community

2020 ◽  
Vol 2674 (12) ◽  
pp. 130-143
Author(s):  
Mayra Chavez ◽  
Wen-Whai Li
Keyword(s):  
Air Quality ◽  
Meteorological Data ◽  
Temporal Variations ◽  
Air Pollutant ◽  
Pollutant Emissions ◽  
Spatial And Temporal Variations ◽  
Quality Data ◽  
Background Concentrations ◽  
Regional Background ◽  
Transportation Emissions

Residents living in near-road communities are exposed to traffic-related air pollutants, which can adversely affect their health. Near-road communities are expected to observe significant spatial and temporal variations in pollutant concentrations. Determining these variations in the surrounding areas can help raise awareness among government agencies of these underserved communities living near highways. This study conducted traffic and air quality measurements along with emission and dispersion modeling of the exposure to transportation emissions of a near-road urban community adjacent to the US 54 highway (US 54), with annual average daily traffic (AADT) of 107,237. The objectives of this study were (i) to develop spatial and temporal patterns of pollutant concentration variation and (ii) to apportion the differences in exposure concentrations to background concentrations and those that are contributed from major highways. It was observed that: (a) particulate matter (PM2.5) in near-road communities is dominated by the regional background concentrations which account for more than 85% of the pollution; and (b) only near-road receptors are affected by the traffic-related air pollutant emissions from major highways while spatial and temporal variations of PM2.5 concentrations in near-road communities are less influenced by local traffic, subsiding rapidly to negligible concentrations at 300 m from the road. Modeled PM2.5 concentrations were compared with monitored data. For better air quality impact assessments, higher quality data such as time-specific traffic volume and fleet information as well as site-specific meteorological data could help yield more accurate concentration predictions. Modeled-to-monitored comparison shows that air quality in near-road communities is dominated by regional background concentrations.

Formation of sulfuric and nitric acid in the atmosphere during long-range transport

Tellus ◽  
1981 ◽  
Vol 33 (2) ◽  
pp. 132-141 ◽  
Author(s):  
H. Rodhe ◽  
P. Crutzen ◽  
A. Vanderpol
Keyword(s):  
Nitric Acid ◽  
Long Range ◽  
Long Range Transport ◽  
Range Transport

scholarly journals Evidence for renoxification in the tropical marine boundary layer

2017 ◽  
Vol 17 (6) ◽  
pp. 4081-4092 ◽  
Author(s):  
Chris Reed ◽  
Mathew J. Evans ◽  
Leigh R. Crilley ◽  
William J. Bloss ◽  
Tomás Sherwen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Organic Nitrogen ◽  
Marine Boundary Layer ◽  
Model Simulation ◽  
Cape Verde ◽  
Box Model ◽  
Nitrogen Species ◽  
Dominant Source ◽  
Mixing Ratios ◽  
Solar Noon

Abstract. We present 2 years of NOx observations from the Cape Verde Atmospheric Observatory located in the tropical Atlantic boundary layer. We find that NOx mixing ratios peak around solar noon (at 20–30 pptV depending on season), which is counter to box model simulations that show a midday minimum due to OH conversion of NO2 to HNO3. Production of NOx via decomposition of organic nitrogen species and the photolysis of HNO3 appear insufficient to provide the observed noontime maximum. A rapid photolysis of nitrate aerosol to produce HONO and NO2, however, is able to simulate the observed diurnal cycle. This would make it the dominant source of NOx at this remote marine boundary layer site, overturning the previous paradigm according to which the transport of organic nitrogen species, such as PAN, is the dominant source. We show that observed mixing ratios (November–December 2015) of HONO at Cape Verde (∼ 3.5 pptV peak at solar noon) are consistent with this route for NOx production. Reactions between the nitrate radical and halogen hydroxides which have been postulated in the literature appear to improve the box model simulation of NOx. This rapid conversion of aerosol phase nitrate to NOx changes our perspective of the NOx cycling chemistry in the tropical marine boundary layer, suggesting a more chemically complex environment than previously thought.

Modeling temporal variations in global residential energy consumption and pollutant emissions

2016 ◽  
Vol 184 ◽  
pp. 820-829 ◽  
Author(s):  
Han Chen ◽  
Ye Huang ◽  
Huizhong Shen ◽  
Yilin Chen ◽  
Muye Ru ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Temporal Variations ◽  
Pollutant Emissions ◽  
Residential Energy ◽  
Residential Energy Consumption

scholarly journals Concentrations of OH and HO<sub>2</sub> radicals during NAMBLEX: measurements and steady state analysis

2005 ◽  
Vol 5 (6) ◽  
pp. 12403-12464 ◽  
Author(s):  
S. C. Smith ◽  
J. D. Lee ◽  
W. J. Bloss ◽  
G. P. Johnson ◽  
D. E. Heard
Keyword(s):  
Boundary Layer ◽  
Steady State ◽  
Detection Limit ◽  
Diurnal Variation ◽  
Marine Boundary Layer ◽  
Chemical Conversion ◽  
Early Morning ◽  
Research Station ◽  
Solar Noon ◽  
Mean Concentration

Abstract. OH and HO2 concentrations were measured simultaneously at the Mace Head Atmospheric Research Station in the summer of 2002 during the NAMBLEX (North Atlantic Marine Boundary Layer EXperiment) field campaign. OH was measured by laser-induced fluorescence employing the FAGE (Fluorescence Assay by Gas Expansion) technique, with a mean daytime detection limit of 2.7×105 molecule cm−3 (5 min acquisition period; signal-to-noise ratio = 1). HO2 was detected as OH following its chemical conversion through addition of NO, with a mean detection limit of 4.4×106 molecule cm−3. The diurnal variation of OH was measured on 24 days, and that of HO2 on 17 days. The local solar noon OH concentrations ranged between (3–8)×106 molecule cm−3, with a 24 h mean concentration of 9.1×105 molecule cm−3. The local solar noon HO2 concentrations were (0.9–2.1)×108 molecule cm−3 (3.5–8.2 pptv), with a 24 h mean concentration of 4.2×107 molecule cm−3. HO2 radicals in the range (2–3)×107 molecule cm−3 were observed at night. During NAMBLEX, a comprehensive suite of supporting measurements enabled a detailed study of the behaviour of HOx radicals under primarily clean marine conditions. Case study periods highlight the typical radical levels observed under different conditions. Steady state expressions are used to calculate OH and HO2 concentrations and to evaluate the effect of different free-radical sources and sinks. The diurnally averaged calculated to measured OH ratio was 1.04±0.36, but the ratio displays a distinct diurnal variation, being less than 1 during the early morning and late afternoon/evening, and greater than 1 in the middle of the day. For HO2 there was an overprediction, with the agreement between calculated and measured concentrations improved by including reaction with measured IO and BrO radicals and uptake to aerosols. Increasing the concentration of IO radicals included in the calculations to above that measured by a DOAS instrument with an absorption path located mainly over the ocean, reflecting the domination of the inter-tidal region as an iodine source at Mace Head, led to further improvement. The results are compared with previous measurements at Mace Head, and elsewhere in the remote marine boundary layer.

scholarly journals Atmospheric new particle formation as source of CCN in the Eastern Mediterranean marine boundary layer

2015 ◽  
Vol 15 (7) ◽  
pp. 11143-11178 ◽  
Author(s):  
N. Kalivitis ◽  
V.-M. Kerminen ◽  
G. Kouvarakis ◽  
I. Stavroulas ◽  
A. Bougiatioti ◽  
...  
Keyword(s):  
Organic Material ◽  
Marine Boundary Layer ◽  
Size Range ◽  
Eastern Mediterranean ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Particle Formation ◽  
New Particle Formation ◽  
Multiple Sources ◽  
Marine Air

Abstract. While Cloud Condensation Nuclei (CCN) production associated with atmospheric new particle formation (NPF) is thought to be frequent throughout the continental boundary layers, few studies on this phenomenon in marine air exist. Here, based on simultaneous measurement of particle number size distributions, CCN properties and aerosol chemical composition, we present the first direct evidence on CCN production resulting from NPF in the Eastern Mediterranean atmosphere. We show that condensation of both gaseous sulfuric acid and organic compounds from multiple sources leads to the rapid growth of nucleated particles to CCN sizes in this environment during the summertime. Sub-100 nm particles were found to be substantially less hygroscopic than larger particles during the period with active NPF and growth (0.2–0.4 lower κ between the 60 and 120 nm particles), probably due to enrichment of organic material in the sub-100 nm size range. The aerosol hygroscopicity tended to be at minimum just before the noon and at maximum in afternoon, which was very likely due to the higher sulfate to organic ratios and higher degree of oxidation of the organic material during the afternoon. Simultaneously to the formation of new particles during daytime, particles formed in the previous day or even earlier were growing into the size range relevant to cloud droplet activation, and the particles formed in the atmosphere were possibly mixed with long-range transported particles.

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