Evidence for an unidentified non-photochemical ground-level source of formaldehyde in the Po Valley with potential implications for ozone production

Abstract. Ozone concentrations in the Po Valley of northern Italy often exceed international regulations. As both a source of radicals and an intermediate in the oxidation of most volatile organic compounds (VOCs), formaldehyde (HCHO) is a useful tracer for the oxidative processing of hydrocarbons that leads to ozone production. We investigate the sources of HCHO in the Po Valley using vertical profile measurements acquired from the airship Zeppelin NT over an agricultural region during the PEGASOS 2012 campaign. Using a 1-D model, the total VOC oxidation rate is examined and discussed in the context of formaldehyde and ozone production in the early morning. While model and measurement discrepancies in OH reactivity are small (on average 3.4 ± 13%), HCHO concentrations are underestimated by as much as 1.5 ppb (45%) in the convective mixed layer. A similar underestimate in HCHO was seen in the 2002–2003 FORMAT Po Valley measurements, though the additional source of HCHO was not identified. Oxidation of unmeasured VOC precursors cannot explain the missing HCHO source, as measured OH reactivity is explained by measured VOCs and their calculated oxidation products. We conclude that local direct emissions from agricultural land are the most likely source of missing HCHO. Model calculations demonstrate that radicals from degradation of this non-photochemical HCHO source increase model ozone production rates by as much as 0.6 ppb h−1 (12%) before noon.

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Evidence for an unidentified ground-level source of formaldehyde in the Po Valley with potential implications for ozone production

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-25139-2014 ◽

2014 ◽

Vol 14 (18) ◽

pp. 25139-25165

Author(s):

J. Kaiser ◽

G. M. Wolfe ◽

B. Bohn ◽

S. Broch ◽

H. Fuchs ◽

...

Keyword(s):

Agricultural Land ◽

Ground Level ◽

Early Morning ◽

Oxidation Products ◽

Ozone Production ◽

Model Calculations ◽

Po Valley ◽

International Regulations ◽

Convective Mixed Layer ◽

D Model

Abstract. Ozone concentrations in the Po Valley of Northern Italy often exceed international regulations. As both a source of radicals and an intermediate in the oxidation of most volatile organic compounds (VOCs), formaldehyde (HCHO) is a useful tracer for the oxidative processing of hydrocarbons that leads to ozone production. We investigate the sources of HCHO in the Po Valley using vertical profile measurements acquired from the airship Zeppelin NT over an agricultural region during the PEGASOS 2012 campaign. Using a 1-D model, the total VOC oxidation rate is examined and discussed in the context of formaldehyde and ozone production in the early morning. While model and measurement discrepancies in OH reactivity are small (on average 3.4±11%), HCHO concentrations are underestimated by as much as 1.5 ppb (45%) in the convective mixed layer. A similar underestimate in HCHO was seen in the 2002–2003 FORMAT Po-Valley measurements, though the additional source of HCHO was not identified. Oxidation of unmeasured VOC precursors cannot explain the missing HCHO source, as measured OH reactivity is explained by measured VOCs and their calculated oxidation products. We conclude that local direct emissions from agricultural land are the most likely source of missing HCHO. Model calculations demonstrate that radicals from degradation of this non-photochemical HCHO source increase model ozone production rates by as much as 0.7 ppb h−1 (10%) before noon.

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Agricultural practices and diffuse nitrogen pollution in Denmark: empirical leaching and catchment models

Water Science & Technology ◽

10.2166/wst.1999.0554 ◽

1999 ◽

Vol 39 (12) ◽

pp. 257-264 ◽

Cited By ~ 5

Author(s):

Hans E. Andersen ◽

Brian Kronvang ◽

Søren E. Larsen

Keyword(s):

Agricultural Land ◽

Root Zone ◽

Agricultural Practices ◽

Animal Manure ◽

Annual Runoff ◽

N Leaching ◽

N Loss ◽

Total N ◽

Model Calculations ◽

N Removal

An empirical leaching model was applied to data on agricultural practices at the field level within 6 small Danish agricultural catchments in order to document any changes in nitrogen (N) leaching from the root zone during the period 1989-96. The model calculations performed at normal climate revealed an average reduction in N-leaching that amounted to 30% in the loamy catchments and 9% in the sandy catchments. The reductions in N leaching could be ascribed to several improvements in agricultural practices during the study period: (i) regulations on livestock density; (ii) regulations on the utilisation of animal manure; (iii) regulations concerning application practices for manure. The average annual total N-loss from agricultural areas to surface water constituted only 54% of the annual average N leached from the root zone in the three loamy catchments and 17% in the three sandy catchments. Thus, subsurface N-removal processes are capable of removing large amounts of N leached from agricultural land. An empirical model for the annual diffuse N-loss to streams from small catchments is presented. The model predicts annual N-loss as a function of the average annual use of mineral fertiliser and manure in the catchment and the total annual runoff from the unsaturated zone.

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Model calculations of tropospheric ozone production potential following observed convective events

Journal of Geophysical Research Atmospheres ◽

10.1029/jd095id09p14049 ◽

1990 ◽

Vol 95 (D9) ◽

pp. 14049 ◽

Cited By ~ 119

Author(s):

Kenneth E. Pickering ◽

Anne M. Thompson ◽

Russell R. Dickerson ◽

Winston T. Luke ◽

Donna P. McNamara ◽

...

Keyword(s):

Tropospheric Ozone ◽

Ozone Production ◽

Production Potential ◽

Model Calculations

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In-situ measurements and 3-D model calculations of backfill compaction and EDZ development in waste disposal drifts in salt rock

The Mechanical Behavior of Salt – Understanding of THMC Processes in Salt ◽

10.1201/9781315106502-25 ◽

2017 ◽

pp. 215-222

Author(s):

S. Heusermann ◽

U. Heemann

Keyword(s):

Waste Disposal ◽

In Situ Measurements ◽

Salt Rock ◽

Model Calculations ◽

D Model

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An investigation of ozone and planetary boundary layer dynamics over the complex topography of Grenoble combining measurements and modeling

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-3-797-2003 ◽

2003 ◽

Vol 3 (1) ◽

pp. 797-825 ◽

Cited By ~ 1

Author(s):

O. Couach ◽

I Balin ◽

R. Jiménez ◽

P. Ristori ◽

S. Perego ◽

...

Keyword(s):

Boundary Layer ◽

Planetary Boundary Layer ◽

Land Surface ◽

Mesoscale Model ◽

Ozone Production ◽

Horizontal Wind ◽

Maximum Height ◽

Complex Topography ◽

Atmospheric Measurements ◽

Model Calculations

Abstract. This paper concerns an evaluation of ozone (O3) and planetary boundary layer (PBL) dynamics over the complex topography of the Grenoble region through a combination of measurements and mesoscale model (METPHOMOD) predictions for three days, during July 1999. The measurements of O3 and PBL structure were obtained with a Differential Absorption Lidar (DIAL) system, situated 20 km south of Grenoble at Vif (310 m a.s.l.). The combined lidar observations and model calculations are in good agreement with atmospheric measurements obtained with an instrumented aircraft (METAIR). Ozone fluxes were calculated using lidar measurements of ozone vertical profiles concentrations and the horizontal wind speeds measured with a Radar Doppler wind profiler (DEGREANE). The ozone flux patterns indicate that the diurnal cycle of ozone production is controlled by local thermal winds. The convective PBL maximum height was some 2700 m above the land surface while the nighttime residual ozone layer was generally found between 1200 and 2200 m. Finally we evaluate the magnitude of the ozone processes at different altitudes in order to estimate the photochemical ozone production due to the primary pollutants emissions of Grenoble city and the regional network of automobile traffic.

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The impacts of precursor reduction and meteorology on ground-level ozone in the Greater Toronto Area

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-8197-2014 ◽

2014 ◽

Vol 14 (15) ◽

pp. 8197-8207 ◽

Cited By ~ 21

Author(s):

S. C. Pugliese ◽

J. G. Murphy ◽

J. A. Geddes ◽

J. M. Wang

Keyword(s):

Health Hazard ◽

Ground Level ◽

Ozone Production ◽

Ground Level Ozone ◽

Ozone Concentrations ◽

Greater Toronto Area ◽

High Solar Radiation ◽

Linear Effects ◽

Human Health Hazard ◽

Ozone Levels

Abstract. Tropospheric ozone (O3) is a major component of photochemical smog and is a known human health hazard, as well as a damaging factor for vegetation. Its precursor compounds, nitrogen oxides (NOx) and volatile organic compounds (VOCs), have a variety of anthropogenic and biogenic sources and exhibit non-linear effects on ozone production. As an update to previous studies on ground-level ozone in the Greater Toronto Area (GTA), we present an analysis of NO2, VOC and O3 data from federal and provincial governmental monitoring sites in the GTA from 2000 to 2012. We show that, over the study period, summertime 24 h VOC reactivity and NO2 midday (11:00–15:00) concentrations at all sites decreased significantly; since 2000, all sites experienced a decrease in NO2 of 28–62% and in measured VOC reactivity of at least 53–71%. Comparing 2002–2003 to 2011–2012, the summed reactivity of OH towards NO2 and a suite of measured VOCs decreased from 8.6 to 4.6 s−1. Ratios of reactive VOC pairs indicate that the effective OH concentration experienced by primary pollutants in the GTA has increased significantly over the study period. Despite the continuous decrease in precursor levels, ozone concentrations are not following the same pattern at all stations; it was found that the Canada-wide Standard for ozone continues to be exceeded at all monitoring stations. Additionally, while the years 2008–2011 had consistently lower ozone levels than previous years, 2012 experienced one of the highest recorded summertime ozone concentrations and a large number of smog episodes. We demonstrate that these high ozone observations in 2012 may be a result of the number of days with high solar radiation, the number of stagnant periods and the transport of high ozone levels from upwind regions.

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Integration of Airborne and Ground Observations of Nitryl Chloride in the Seoul Metropolitan Area and the Implications on Regional Oxidation Capacity During KORUS-AQ 2016

10.5194/acp-2018-1216 ◽

2018 ◽

Cited By ~ 2

Author(s):

Daun Jeong ◽

Roger Seco ◽

Dasa Gu ◽

Youngro Lee ◽

Benjamin A. Nault ◽

...

Keyword(s):

Metropolitan Area ◽

Box Model ◽

Ozone Production ◽

Integrated Analysis ◽

Back Trajectory ◽

Night Time ◽

Model Calculations ◽

Nitryl Chloride ◽

Seoul Metropolitan Area ◽

The Impact

Abstract. Nitryl chloride (ClNO2) is a radical reservoir species that releases chlorine radicals upon photolysis. An integrated analysis of the impact of ClNO2 on regional photochemistry in the Seoul Metropolitan Area (SMA) during the Korean-United States-Air Quality (KORUS-AQ) 2016 field campaign is presented. Comprehensive multiplatform observations were conducted aboard the NASA DC-8 and at two ground sites (Olympic Park, OP; Taehwa Research Forest, TRF), representing an urbanized area and a forested region downwind, respectively. The overall diurnal variations of ClNO2 in both sites appeared similar but the night time variation were systematically different. For about half of the observation days at the OP site the level of ClNO2 increased at sunset but rapidly decreased at around midnight. On the other hand, high levels were sustained throughout the night at the TRF site. Significant levels of ClNO2 were sustained at both sites for 4–5 hours after sunrise. Airborne observations, box model calculations, and back trajectory analysis consistently show that this high levels of ClNO2 in the morning is likely due to the transport of air masses within the boundary layer. Box model results show that chlorine radical initiated chemistry can impact the regional photochemistry by elevating net ozone production rate up to ~ 25 % in the morning.

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Comparison of surface ozone simulation among selected regional models in MICS-Asia III – effects of chemistry and vertical transport for the causes of difference

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-603-2019 ◽

2019 ◽

Vol 19 (1) ◽

pp. 603-615 ◽

Cited By ~ 6

Author(s):

Hajime Akimoto ◽

Tatsuya Nagashima ◽

Jie Li ◽

Joshua S. Fu ◽

Dongsheng Ji ◽

...

Keyword(s):

Surface Ozone ◽

Early Morning ◽

Photochemical Activity ◽

Vertical Transport ◽

Ozone Production ◽

Phase Iii ◽

Regional Models ◽

Mixing Ratios ◽

The Difference ◽

Intercomparison Study

Abstract. In order to clarify the causes of variability among the model outputs for surface ozone in the Model Intercomparison Study Asia Phase III (MICS-Asia III), three regional models, CMAQ v.5.0.2, CMAQ v.4.7.1, and NAQPMS (abbreviated as NAQM in this paper), have been selected. Detailed analyses of monthly averaged diurnal variation have been performed for selected grids covering the metropolitan areas of Beijing and Tokyo and at a remote oceanic site, Oki. The chemical reaction mechanism, SAPRC99, used in the CMAQ models tended to give a higher net chemical ozone production than CBM-Z used in NAQM, agreeing with previous studies. Inclusion of the heterogeneous “renoxification” reaction of HNO3 (on soot surface)→NO+NO2 only in NAQM would give a higher NO concentration resulting in a better agreement with observational data for NO and nighttime O3 mixing ratios. In addition to chemical processes, the difference in the vertical transport of O3 was found to affect the simulated results significantly. Particularly, the increase in downward O3 flux from the upper layer to the surface after dawn was found to be substantially different among the models. Larger early morning vertical transport of O3 simulated by CMAQ 5.0.2 is thought to be the reason for higher daytime O3 in July in this model. All three models overestimated the daytime ozone by ca. 20 ppbv at the remote site Oki in July, where in situ photochemical activity is minimal.

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OH and HO<sub>2</sub> radical chemistry in a midlatitude forest: Measurements and model comparisons

10.5194/acp-2019-726 ◽

2019 ◽

Cited By ~ 2

Author(s):

Michelle L. Lew ◽

Pamela S. Rickly ◽

Brandon P. Bottorff ◽

Sofia Sklaveniti ◽

Thierry Léonardis ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Global Climate ◽

Oxidation Products ◽

Chemical Mechanism ◽

Ozone Production ◽

Peroxy Radicals ◽

Mixing Ratios ◽

Photolysis Rates ◽

Model Predictions ◽

Ho2 Radical

Abstract. Reactions of the hydroxyl (OH) and peroxy radicals (HO2 and RO2) play a central role in the chemistry of the atmosphere. In addition to controlling the lifetimes of many trace gases important to issues of global climate change, OH radical reactions initiate the oxidation of volatile organic compounds (VOCs) which can lead to the production of ozone and secondary organic aerosols in the atmosphere. Previous measurements of these radicals in forest environments characterized by high mixing ratios of isoprene and low mixing ratios of nitrogen oxides (NOx) have shown serious discrepancies with modeled concentrations. These results bring into question our understanding of the atmospheric chemistry of isoprene and other biogenic VOCs under low NOx conditions. During the summer of 2015, OH and HO2 radical concentrations as well as total OH reactivity were measured using Laser-Induced Fluorescence - Fluorescence Assay by Gas Expansion (LIF-FAGE) techniques as part of the Indiana Radical, Reactivity and Ozone Production Intercomparison (IRRONIC). This campaign took place in a forested area near the Indiana University, Bloomington campus characterized by high mixing ratios of isoprene and low mixing ratios of NOx. Supporting measurements of photolysis rates, VOCs, NOx, and other species were used to constrain a zero-dimensional box model based on the Regional Atmospheric Chemistry Mechanism (RACM2) and the Master Chemical Mechanism (MCM). Using an OH chemical scavenger technique, the study revealed the presence of an interference with the LIF-FAGE measurements of OH that increased with both ambient concentrations of ozone and temperature. Subtraction of the interference resulted in measured OH concentrations that were in better agreement with model predictions, although the model still underestimated the measured concentrations, likely due to an underestimation of the concentration of NO at this site. Measurements of HO2 radical concentrations during the campaign included a fraction of isoprene-based peroxy radicals (HO2* = HO2 + αRO2) and were found to agree with model predictions. On average, the measured reactivity was consistent with that calculated from measured OH sinks to within 20 %, with modeled oxidation products accounting for the missing reactivity, although significant missing reactivity (approximately 40 % of the total measured reactivity) was observed on some days.

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