scholarly journals Characteristics of wintertime VOCs in suburban and urban Beijing: concentrations, emission ratios, and festival effects

2019 ◽  
Vol 19 (12) ◽  
pp. 8021-8036 ◽  
Author(s):  
Kun Li ◽  
Junling Li ◽  
Shengrui Tong ◽  
Weigang Wang ◽  
Ru-Jin Huang ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Urban Areas ◽  
Diurnal Variations ◽  
Urban Site ◽  
Anthropogenic Emissions ◽  
Suburban Areas ◽  
Key Characteristics ◽  
Volatile Organic ◽  
Suburban Site ◽  
Emission Ratios

Abstract. Measurements of volatile organic compounds (VOCs) were performed at a suburban site and an urban site in Beijing during the winter of 2014–2015. The VOC concentrations and emission ratios (ERs) to CO were compared at these two sites. It is found that though the VOC concentrations at the urban site are 2.67±1.15 times of those at the suburban site, the ERs are similar (within a factor of 1.5). It is indicated that (1) the VOCs at suburban areas are mainly from the transportation from the urban areas and (2) the ERs measured at the urban areas are also valid for the surrounding suburban areas. By comparing the diurnal variations and the contribution of anthropogenic emissions at both sites, we find that the photochemical processes are very active at the urban site, and these processes play an important role in the daytime oxygenated VOC (OVOC) formation. The methanol at the urban site and the formic acid at the suburban site probably have additional sources, which are attributed to be solvent use and soil/agriculture, respectively. The festival effects from the Chinese New Year (CNY) were investigated. The VOC concentrations decreased ∼60 % during CNY holidays, probably due to the population migration during festival holidays. In addition, fireworks are found to be an important source of acetonitrile, aromatics, and some OVOCs during the CNY festival and should be controlled more strictly. This study provides key characteristics of wintertime VOCs in suburban and urban Beijing and has implications for better understanding the atmospheric chemistry of VOCs in and around this megacity.

scholarly journals Characteristics of wintertime VOCs in suburban and urban Beijing: concentrations, emission ratios, and festival effects

2019 ◽  
Author(s):  
Kun Li ◽  
Junling Li ◽  
Shengrui Tong ◽  
Weigang Wang ◽  
Ru-Jin Huang ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Urban Areas ◽  
Diurnal Variations ◽  
Urban Site ◽  
Anthropogenic Emissions ◽  
Suburban Areas ◽  
Key Characteristics ◽  
Volatile Organic ◽  
Suburban Site ◽  
Emission Ratios

Abstract. Measurements of volatile organic compounds (VOCs) were performed at a suburban site and an urban site in Beijing during the winter of 2014–2015. The VOC concentrations and emission ratios (ERs) to CO were compared at these two sites. It is found that though the VOC concentrations at the urban site are 2.67 ± 1.15 times of those at the suburban site, the ERs are similar (within a factor of 1.5). It is indicated that: (1) the VOCs at suburban areas are mainly from the transportation from the urban areas; (2) the ERs measured at the urban areas are also valid for the surrounding suburban areas. By comparing the diurnal variations and the contribution of anthropogenic emissions at both sites, we find that the photochemical processes are very active at the urban site, and these processes play an important role in the daytime oxygenated VOCs (OVOCs) formation. The methanol at the urban site and the formic acid at the suburban site probably have additional sources, which are attributed to be solvent use and soil/agriculture, respectively. The festival effects from Chinese New Year (CNY) were investigated. The VOC concentrations decreased ~ 60 % during CNY holidays, probably due to the population migration during festival holidays. In addition, fireworks are found to be an important source of acetonitrile, aromatics, and some OVOCs during CNY festival, and should be controlled more strictly. This study provides key characteristics of wintertime VOCs in suburban and urban Beijing, and has implications for better understanding the atmospheric chemistry of VOCs in and around this megacity.

scholarly journals Source characterization of volatile organic compounds measured by proton-transfer-reaction time-of-flight mass spectrometers in Delhi, India

2020 ◽  
Vol 20 (16) ◽  
pp. 9753-9770 ◽  
Author(s):  
Liwei Wang ◽  
Jay G. Slowik ◽  
Nidhi Tripathi ◽  
Deepika Bhattu ◽  
Pragati Rai ◽  
...  
Keyword(s):  
Reaction Time ◽  
Solid Fuel ◽  
Transfer Reaction ◽  
Proton Transfer Reaction ◽  
Urban Site ◽  
Mass Spectrometers ◽  
Mixing Ratios ◽  
Volatile Organic ◽  
Solid Fuel Combustion ◽  
Suburban Site

Abstract. Characteristics and sources of volatile organic compounds (VOCs) were investigated with highly time-resolved simultaneous measurements by two proton-transfer-reaction time-of-flight mass spectrometers (PTR-ToF-MS) at an urban and a suburban site in New Delhi, India, from January to March 2018. During the measurement period, high mixing ratios of VOCs and trace gases were observed, with high nocturnal mixing ratios and strong day–night variations. The positive matrix factorization (PMF) receptor model was applied separately to the two sites, and six major factors of VOCs were identified at both sites, i.e., two factors related to traffic emissions, two to solid fuel combustion, and two secondary factors. At the urban site, traffic-related emissions comprising mostly mono-aromatic compounds were the dominant sources, contributing 56.6 % of the total mixing ratio, compared to 36.0 % at the suburban site. Emissions from various solid fuel combustion processes, particularly in the night, were identified as a significant source of aromatics, phenols and furans at both sites. The secondary factors accounted for 15.9 % of the total VOC concentration at the urban site and for 33.6 % at the suburban site. They were dominated by oxygenated VOCs and exhibited substantially higher contributions during daytime.

scholarly journals Emission and chemistry of organic carbon in the gas and aerosol phase at a sub-urban site near Mexico City in March 2006 during the MILAGRO study

2008 ◽  
Vol 8 (6) ◽  
pp. 21265-21312 ◽  
Author(s):  
J. A. de Gouw ◽  
D. Welsh-Bon ◽  
C. Warneke ◽  
W. C. Kuster ◽  
L. Alexander ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Organic Carbon ◽  
Mexico City ◽  
Organic Aerosol ◽  
Early Morning ◽  
Diurnal Variations ◽  
Urban Site ◽  
Secondary Formation ◽  
The Us ◽  
Emission Ratios

Abstract. Volatile organic compounds (VOCs) and carbonaceous aerosol were measured at a sub-urban site near Mexico City in March of 2006 during the MILAGRO study (Megacity Initiative: Local and Global Research Objectives). Diurnal variations of hydrocarbons, elemental carbon (EC) and hydrocarbon-like organic aerosol (HOA) were dominated by a high peak in the early morning when local emissions accumulated in a shallow boundary layer, and a minimum in the afternoon when the emissions were diluted in a significantly expanded boundary layer and, in case of the reactive gases, removed by OH. In comparison, diurnal variations of species with secondary sources such as the aldehydes, ketones, oxygenated organic aerosol (OOA) and water-soluble organic carbon (WSOC) stayed relatively high in the afternoon indicating strong photochemical formation. Emission ratios of many hydrocarbon species relative to CO were higher in Mexico City than in the US, but we found similar emission ratios for most oxygenated VOCs and organic aerosol. Secondary formation of acetone may be more efficient in Mexico City than in the US, due to higher emissions of alkane precursors from the use of liquefied petroleum gas. Secondary formation of organic aerosol was similar between Mexico City and the US. Combining the data for all measured gas and aerosol species, we describe the budget of total observed organic carbon (TOOC), and find that the enhancement ratio of TOOC relative to CO is conserved between the early morning and mid afternoon despite large compositional changes. Finally, the influence of biomass burning is investigated using the measurements of acetonitrile, which was found to correlate with levoglucosan in the particle phase. Diurnal variations of acetonitrile indicate a contribution from local burning sources. Scatter plots of acetonitrile versus CO suggest that the contribution of biomass burning to the enhancement of most gas and aerosol species was not dominant and perhaps not dissimilar from observations in the US.

scholarly journals Observations of atmospheric mercury in China: a critical review

2015 ◽  
Vol 15 (16) ◽  
pp. 9455-9476 ◽  
Author(s):  
X. W. Fu ◽  
H. Zhang ◽  
B. Yu ◽  
X. Wang ◽  
C.-J. Lin ◽  
...  
Keyword(s):  
Dry Deposition ◽  
Urban Areas ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Urban Site ◽  
Anthropogenic Emissions ◽  
Activity Data ◽  
The Past ◽  
Remote Sites ◽  
The Impact

Abstract. China presently contributes the largest amount of anthropogenic mercury (Hg) emission into the atmosphere in the world. Over the past decade, numerous studies have been conducted to characterize the concentration and forms of atmospheric Hg in China, which provide insights into the spatial and temporal distributions of atmospheric Hg through ground-based measurements at widely diverse geographical locations and during cruise and flight campaigns. In this paper, we present a comprehensive review of the state of understanding in atmospheric Hg in China. Gaseous elemental mercury (GEM) and particulate-bound mercury (PBM) measured at the remote sites in China are substantially elevated compared to the background values in the Northern Hemisphere. In Chinese urban areas, the highly elevated GEM, PBM and gaseous oxidized mercury (GOM) were mainly derived from local anthropogenic Hg emissions, whereas regional anthropogenic emissions and long-range transport from domestic source regions are the primary causes of the elevated GEM and PBM concentrations at remote sites. Using 7–9 years of continuous observations at a remote site and an urban site, a slight increase in atmospheric GEM (2.4–2.5 % yr−1) was identified (paired samples test: p < 0.01), which is in agreement with the increasing domestic anthropogenic emissions. Anthropogenic GEM emission quantity in China estimated through the observed GEM / CO concentration ratios ranged from 632 to 1138 t annually over the past decade, 2–3 times larger than published values using emission activity data. Modeling results and filed measurements show dry deposition is the predominant process for removing Hg from the atmosphere, 2.5–9.0 times larger than wet deposition, due to the elevated atmospheric GEM and PBM concentrations that facilitate dry deposition to terrestrial landscapes. Further studies to reconcile the observed and simulated Hg concentrations, to understand the impact of domestic emission reduction on Hg concentration and deposition and to delineate the role of Hg emission and deposition of China in the global Hg biogeochemical cycle, are needed.

scholarly journals Sesquiterpenes identified as key species for atmospheric chemistry in boreal forest by terpenoid and OVOC measurements

2018 ◽  
Author(s):  
Heidi Hellén ◽  
Arnaud P. Praplan ◽  
Toni Tykkä ◽  
Ilona Ylivinkka ◽  
Ville Vakkari ◽  
...  
Keyword(s):  
Organic Acids ◽  
Boreal Forest ◽  
Atmospheric Chemistry ◽  
Vertical Mixing ◽  
Diurnal Variations ◽  
Oxidation Products ◽  
Key Species ◽  
Seasonal And Diurnal Variations ◽  
Volatile Organic ◽  
Volatile Organic Acids

Abstract. Concentrations of terpenoids (isoprene, monoterpenes, sesquiterpenes) and oxygenated volatile organic compounds (OVOCs, i.e. aldehydes, alcohols, acetates and volatile organic acids) were investigated during two years at a boreal forest site in Hyytiälä, Finland, using in situ gas chromatograph-mass spectrometers (GC-MS). Seasonal and diurnal variations of terpenoid and OVOC concentrations as well as their relationship with meteorological factors were studied. Of the studied VOCs, C2-C7 unbranched volatile organic acids (VOAs) were found to have the highest concentrations mainly due to their low reactivity. Of the terpenoids, monoterpenes (MTs) had highest concentrations at the site, but also 7 different highly reactive sesquiterpenes (SQTs) were detected. Monthly and daily mean concentrations of most terpenoids, aldehydes and VOAs were found to be highly dependent on the temperature. Highest exponential correlation with temperature was found for a SQT (β-caryophyllene) in summer. The diurnal variations of the concentrations could be explained by sources, sinks and vertical mixing. Especially the diurnal variations of MT concentrations were strongly affected by vertical mixing. Based on the temperature correlations and mixing layer height simple proxies were developed for estimating MT and SQT concentrations. To estimate the importance of different compound groups and compounds for the local atmospheric chemistry, reactivity with main oxidants (OH, NO3 and O3) and production rates of oxidation products (OxPR) were calculated. MTs dominated OH and NO3 radical chemistry, but SQTs had a major impact on ozone chemistry, even though concentrations of SQT were 30 times lower than MT concentrations. SQTs were the most important also for the production of oxidation products. Since SQTs have high secondary organic aerosol (SOA) yields, results clearly indicate the importance of SQTs for local SOA production.

scholarly journals Temporal variations in CO<sub>2</sub> and CO at Ahmedabad in western India

2015 ◽  
Vol 15 (22) ◽  
pp. 32185-32238 ◽  
Author(s):  
N. Chandra ◽  
S. Lal ◽  
S. Venkataramani ◽  
P. K. Patra ◽  
V. Sheel
Keyword(s):  
Atmospheric Chemistry ◽  
Urban Areas ◽  
Fossil Fuel ◽  
Transport Model ◽  
Urban Site ◽  
Urban Region ◽  
Western India ◽  
Study Region ◽  
Late Night ◽  
South West Monsoon

Abstract. About 70 % of the anthropogenic CO2 is emitted from the megacities and urban areas of the world. In-situ simultaneous measurements of carbon dioxide (CO2) and carbon monoxide (CO) have been made using a state-of-the-art laser based cavity ring down spectroscopy technique at Ahmedabad, an urban site in western India, from November 2013 to May 2015 with a break during March to June 2014. Annual average concentrations of CO2 and CO have been found to be 413.0 ± 13.7 ppm and 0.50 ± 0.37 ppm respectively. Both the species show strong seasonality, with lower concentrations of 400.3 ± 6.8 ppm and 0.19 ± 0.13 ppm, respectively during the south-west monsoon, and higher values of 419.6 ± 22.8 ppm and 0.72 ± 0.68 ppm, respectively in autumn (SON). Strong diurnal variations are also observed for both the species. The common factors for diurnal cycles of CO2 and CO are the vertical mixing and rush hour traffic, while the influence of biospheric fluxes is also seen in CO2 diurnal cycle. Using CO and CO2 covariation, we differentiate the anthropogenic and biospheric components of CO2 and found that significant contributions of biospheric respiration and anthropogenic emission in the late night (00:00–05:00 IST) and evening rush hours (18:00–22:00 IST) respectively. We compute total yearly emission of CO to be 69.2 ± 0.07 Gg for the study region using the observed CO : CO2 correlation slope and bottom-up CO2 emission inventory. This calculated emission of CO is 52 % larger than the estimated emission of CO by the EDGAR inventory. The observations of CO2 have been compared with an atmospheric chemistry transport model (i.e., ACTM), which incorporates various components of CO2 fluxes. ACTM is able to capture the basic variabilities, but both diurnal and seasonal amplitudes are largely underestimated compared to the observations. We attribute this underestimation by model to uncertainties in terrestrial biosphere fluxes and coarse model resolution. The fossil fuel signal from the model shows fairly good correlation with observed CO2 variations, which supports the overall dominance of fossil fuel emissions over the biospheric fluxes in this urban region.

scholarly journals Effect of COVID-19 lockdown on regional pollution in Ireland

2021 ◽  
Author(s):  
Teresa K. Spohn ◽  
Damien Martin ◽  
Michael Geever ◽  
Colin O’Dowd
Keyword(s):  
Urban Areas ◽  
Initial Increase ◽  
Emission Sources ◽  
Particle Measurements ◽  
Wind Speeds ◽  
Suburban Areas ◽  
Average Wind ◽  
Volatile Organic ◽  
Rural Sites ◽  
Agricultural Regions

AbstractThis study examines the regional impact of the COVID-19 lockdown restrictions on pollution in Ireland by comparing the 2020 measurements of ozone (O3), nitrogen dioxide (NO2), and particulate matter (PM) from monitoring stations around the country to the previous 3-year average. Results indicate that O3 was 5.6% lower and 13.7% higher than previous years during the lockdown at rural and suburban sites, respectively. NO2 decreased by 50.7% in urban areas, but increased slightly in agricultural regions, consistent with satellite observations. PM concentrations did not change significantly compared to previous years; however, a reduction in the signal variability in the smaller size particle measurements may be the result of different emission sources. The reduction in NO2 likely increased the ratio of volatile organic compounds (VOCs) to NOx (nitrogen oxides), creating a NOx limited environment, which resulted in an initial increase in O3 in suburban areas, and the lower than usual levels observed at rural sites. Meteorology showed higher than average wind speeds prior to lockdown, which likely acted to disperse PM and NO2.

scholarly journals Temporal variability and sources of VOCs in urban areas of Eastern Mediterranean

2016 ◽  
Author(s):  
Christos Kaltsonoudis ◽  
Evangelia Kostenidou ◽  
Kalliopi Florou ◽  
Magda Psichoudaki ◽  
Spyros N. Pandis
Keyword(s):  
Biomass Burning ◽  
Urban Areas ◽  
Eastern Mediterranean ◽  
Proton Transfer Reaction ◽  
Oxidation Products ◽  
Residential Heating ◽  
Volatile Organic ◽  
Biogenic Compounds ◽  
The City ◽  
Emission Ratios

Abstract. During the summer of 2012 volatile organic compounds (VOCs) were monitored by Proton Transfer Reaction – Mass Spectrometry (PTR-MS) in urban backgrounds sites, in Athens and Patras, two of the largest cities in Greece. Also during the winter of 2013 PTR-MS measurements were conducted in the center of the city of Athens. Positive matrix factorization (PMF) was applied to the VOC measurements to gain insights about their sources. In summer most of the measured VOCs were due to biogenic and traffic emissions. Isoprene, monoterpenes and several oxygenated VOCs (oVOCs) originated mainly from vegetation either directly or as oxidation products. Isoprene average concentrations in Patras and Athens were 1 ppb and 0.7 ppb respectively while the monoterpene concentrations were 0.3 ppb and 0.9 ppb respectively. Traffic was the main source of aromatic compounds during summer. For Patras and Athens the average concentrations of benzene were 0.1 ppb and 0.2 ppb, of toluene 0.3 ppb and 0.8 ppb and of the xylenes 0.3 ppb and 0.7 ppb respectively. Winter measurements in Athens revealed that biomass burning used for residential heating was a major VOC source contributing both biogenic compounds such as isoprene and the monoterpenes, and aromatic VOCs. Several episodes related to biomass burning were identified and emission ratios (ER) and emission factors (EF) were estimated.

scholarly journals Modeling Biogenic and Anthropogenic Secondary Organic Aerosol in China

2016 ◽  
Author(s):  
Jianlin Hu ◽  
Peng Wang ◽  
Qi Ying ◽  
Hongliang Zhang ◽  
Jianjun Chen ◽  
...  
Keyword(s):  
Urban Areas ◽  
Secondary Organic Aerosol ◽  
Temporal Distribution ◽  
Organic Aerosol ◽  
Sensitivity Analyses ◽  
Biogenic Emissions ◽  
Anthropogenic Emissions ◽  
Volatile Components ◽  
Volatile Organic ◽  
Isoprene Oxidation

Abstract. A revised Community Multiscale Air Quality (CMAQ) model with updated secondary organic aerosol (SOA) yields and more detailed description of SOA formation from isoprene oxidation was applied to study the spatial and temporal distribution of SOA in China in the entire year of 2013. Predicted organic carbon (OC), elemental carbon and volatile organic compounds agreed favorably with observations at several urban areas, although the high OC concentrations in wintertime in Beijing were under-predicted. Predicted summer SOA was generally higher (10–15 µg m−3) due to large contributions of isoprene (country average, 61 %). Wintertime SOA was slightly lower and was mostly due to emissions of alkane and aromatic compounds (51 %). Contributions of monoterpenes SOA were relatively constant (8–10 %). Overall, biogenic SOA accounted for approximately 75 % of total SOA in summer, 50–60 % in autumn and spring, and 24 % in winter. Sichuan Basin had the highest predicted SOA concentrations in the country in all seasons, with hourly concentrations up to 50 µg m−3. Approximately half of the SOA in all seasons was due to the traditional equilibrium partitioning of semi-volatile components followed by oligomerization, while the remaining SOA was mainly due to reactive surface uptake of isoprene epoxide (5–14 %), glyoxal (14–25 %) and methylglyoxal (23–28 %). Sensitivity analyses showed that formation of SOA from biogenic emissions was significantly enhanced due to anthropogenic emissions. Removing all anthropogenic emissions while keeping the biogenic emissions unchanged led to total SOA concentrations of less than 1 µg m−3, which suggests that manmade emissions facilitated biogenic SOA formation and controlling anthropogenic emissions would result in reduction of both anthropogenic and biogenic SOA.

scholarly journals Emission and chemistry of organic carbon in the gas and aerosol phase at a sub-urban site near Mexico City in March 2006 during the MILAGRO study

2009 ◽  
Vol 9 (10) ◽  
pp. 3425-3442 ◽  
Author(s):  
J. A. de Gouw ◽  
D. Welsh-Bon ◽  
C. Warneke ◽  
W. C. Kuster ◽  
L. Alexander ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Organic Carbon ◽  
Mexico City ◽  
Organic Aerosol ◽  
Early Morning ◽  
Diurnal Variations ◽  
Urban Site ◽  
Secondary Formation ◽  
The U.S ◽  
Emission Ratios

Abstract. Volatile organic compounds (VOCs) and carbonaceous aerosol were measured at a sub-urban site near Mexico City in March of 2006 during the MILAGRO study (Megacity Initiative: Local and Global Research Objectives). Diurnal variations of hydrocarbons, elemental carbon (EC) and hydrocarbon-like organic aerosol (HOA) were dominated by a high peak in the early morning when local emissions accumulated in a shallow boundary layer, and a minimum in the afternoon when the emissions were diluted in a significantly expanded boundary layer and, in case of the reactive gases, removed by OH. In comparison, diurnal variations of species with secondary sources such as the aldehydes, ketones, oxygenated organic aerosol (OOA) and water-soluble organic carbon (WSOC) stayed relatively high in the afternoon indicating strong photochemical formation. Emission ratios of many hydrocarbon species relative to CO were higher in Mexico City than in the U.S., but we found similar emission ratios for most oxygenated VOCs and organic aerosol. Secondary formation of acetone may be more efficient in Mexico City than in the U.S., due to higher emissions of alkane precursors from the use of liquefied petroleum gas. Secondary formation of organic aerosol was similar between Mexico City and the U.S. Combining the data for all measured gas and aerosol species, we describe the budget of total observed organic carbon (TOOC), and find that the enhancement ratio of TOOC relative to CO is conserved between the early morning and mid afternoon despite large compositional changes. Finally, the influence of biomass burning is investigated using the measurements of acetonitrile, which was found to correlate with levoglucosan in the particle phase. Diurnal variations of acetonitrile indicate a contribution from local burning sources. Scatter plots of acetonitrile versus CO suggest that the contribution of biomass burning to the enhancement of most gas and aerosol species was not dominant and perhaps not dissimilar from observations in the U.S.

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