scholarly journals Molecular characterization of gaseous and particulate oxygenated compounds at a remote site in Cape Corsica in the western Mediterranean basin

2020 ◽  
Author(s):  
Vincent Michoud ◽  
Elise Hallemans ◽  
Laura Chiappini ◽  
Eva Leoz-Garziandia ◽  
Aurélie Colomb ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Carboxylic Acids ◽  
Organic Aerosol ◽  
Western Mediterranean ◽  
Water Soluble ◽  
Molecular Composition ◽  
Particle Phase ◽  
Western Mediterranean Basin ◽  
Hydroxyl Compounds

Abstract. The characterization of the molecular composition of organic carbon in both gaseous and aerosol is key to understand the processes involved in the formation and aging of secondary organic aerosol. Therefore a technique using active sampling on cartridges and filters and derivatization followed by analysis using a Thermal Desorption-Gas Chromatography/mass spectrometer (TD-GC/MS) has been used to study the molecular composition of organic carbon in both gaseous and aerosol phases during an intensive field campaign which took place in Corsica during the summer 2013: the ChArMEx (Chemistry and Aerosol Mediterranean Experiment) SOP1b (Special Observation Period 1B) campaign. These measurements led to the identification of 51 oxygenated (carbonyl and or hydroxyl) compounds in the gaseous phase with concentrations comprised between 21 ng m−3 and 3900 ng m−3 and of 85 compounds in the particulate phase with concentrations comprised between 0.3 and 277 ng m−3. Comparisons of these measurements with collocated data using other techniques have been conducted showing fair agreement in general for most species except for glyoxal in the gas phase and malonic, tartaric, malic and succinic acids in the particle phase with disagreements that can reach up to a factor of 8 and 20 on average, respectively for the latter two acids. Comparison between the sum of all compounds identified by TD-GC/MS in particle phase with the total Organic Matter (OM) mass reveal that 18 % of the total OM mass can be explained by the compounds measured by TD-GC/MS for the whole campaign. This number increase to 24 % of the total Water Soluble OM (WSOM) measured by PILS-TOC if we consider only the sum of the soluble compounds measured by TD-GC/MS. This highlights the non-negligible fraction of the OM mass identified by these measurements but also the relative important fraction of OM mass remaining unidentified during the campaign and therefore the complexity of characterizing exhaustively the Organic Aerosol (OA) molecular chemical composition. The fraction of OM measured by TD-GC/MS is largely dominated by di-carboxylic acids which represents 49 % of the PM2.5 content detected and quantified by this technique. Other contributions to PM2.5 composition measured by TD-GC/MS are then represented by tri-carboxylic acids (15 %), alcohols (13 %), aldehydes (10 %), di-hydroxy-carboxylic acids (5 %), monocarboxylic acids and ketones (3 % each) and hydroxyl-carboxylic acids (2 %). These results highlight the importance of poly functionalized carboxylic acids for OM while the chemical processes responsible for their formation in both phases remain uncertain. While not measured by TD-GC/MS technique, HUmic-LIke Substances (HULIS) represent the most abundant identified species in the aerosol, contributing for 59 % of the total identified OM mass on average during the campaign. 14 compounds were detected and quantified in both phases allowing the calculation of experimental partitioning coefficient for these species. The comparison of these experimental partitioning coefficients with theoretical ones, estimated by three different models, reveals large discrepancies varying from 2 to 7 orders of magnitude. These results suggest that the supposed instantaneous equilibrium being established between gaseous and particulate phases assuming a homogeneous non-viscous particle phase is questionable.

scholarly journals Molecular characterization of gaseous and particulate oxygenated compounds at a remote site in Cape Corsica in the western Mediterranean Basin

2021 ◽  
Vol 21 (10) ◽  
pp. 8067-8088
Author(s):  
Vincent Michoud ◽  
Elise Hallemans ◽  
Laura Chiappini ◽  
Eva Leoz-Garziandia ◽  
Aurélie Colomb ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Carboxylic Acids ◽  
Organic Aerosol ◽  
Western Mediterranean ◽  
Water Soluble ◽  
Molecular Composition ◽  
Particle Phase ◽  
Western Mediterranean Basin ◽  
Partitioning Coefficients

Abstract. The characterization of the molecular composition of organic carbon in both gaseous and aerosol is key to understanding the processes involved in the formation and aging of secondary organic aerosol. Therefore a technique using active sampling on cartridges and filters and derivatization followed by analysis using a thermal desorption–gas chromatography–mass spectrometer (TD–GC–MS) has been used. It is aimed at studying the molecular composition of organic carbon in both gaseous and aerosol phases (PM2.5) during an intensive field campaign which took place in Corsica (France) during the summer of 2013: the ChArMEx (Chemistry and Aerosol Mediterranean Experiment) SOP1b (Special Observation Period 1B) campaign. These measurements led to the identification of 51 oxygenated (carbonyl and or hydroxyl) compounds in the gaseous phase with concentrations between 21 and 3900 ng m−3 and of 85 compounds in the particulate phase with concentrations between 0.3 and 277 ng m−3. Comparisons of these measurements with collocated data using other techniques have been conducted, showing fair agreement in general for most species except for glyoxal in the gas phase and malonic, tartaric, malic and succinic acids in the particle phase, with disagreements that can reach up to a factor of 8 and 20 on average, respectively, for the latter two acids. Comparison between the sum of all compounds identified by TD–GC–MS in the particle phase and the total organic matter (OM) mass reveals that on average 18 % of the total OM mass can be explained by the compounds measured by TD–GC–MS. This number increases to 24 % of the total water-soluble OM (WSOM) measured by coupling the Particle Into Liquid Sampler (PILS)-TOC (total organic carbon) if we consider only the sum of the soluble compounds measured by TD–GC–MS. This highlights the important fraction of the OM mass identified by these measurements but also the relative important fraction of OM mass remaining unidentified during the campaign and therefore the complexity of characterizing exhaustively the organic aerosol (OA) molecular chemical composition. The fraction of OM measured by TD–GC–MS is largely dominated by di-carboxylic acids, which represent 49 % of the PM2.5 content detected and quantified by this technique. Other contributions to PM2.5 composition measured by TD–GC–MS are then represented by tri-carboxylic acids (15 %), alcohols (13 %), aldehydes (10 %), di-hydroxy-carboxylic acids (5 %), monocarboxylic acids and ketones (3 % each), and hydroxyl-carboxylic acids (2 %). These results highlight the importance of polyfunctionalized carboxylic acids for OM, while the chemical processes responsible for their formation in both phases remain uncertain. While not measured by the TD–GC–MS technique, humic-like substances (HULISs) represent the most abundant identified species in the aerosol, contributing for 59 % of the total OM mass on average during the campaign. A total of 14 compounds were detected and quantified in both phases, allowing the calculation of experimental partitioning coefficients for these species. The comparison of these experimental partitioning coefficients with theoretical ones, estimated by three different models, reveals large discrepancies varying from 2 to 7 orders of magnitude. These results suggest that the supposed instantaneous equilibrium being established between gaseous and particulate phases assuming a homogeneous non-viscous particle phase is questionable.

scholarly journals Contribution of dust inputs to dissolved organic carbon and water transparency in Mediterranean reservoirs

2012 ◽  
Vol 9 (12) ◽  
pp. 5049-5060 ◽  
Author(s):  
I. de Vicente ◽  
E. Ortega-Retuerta ◽  
R. Morales-Baquero ◽  
I. Reche
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Western Mediterranean ◽  
Water Soluble ◽  
Water Transparency ◽  
Saharan Dust ◽  
Organic Components ◽  
Western Mediterranean Basin ◽  
Run Off ◽  
Atmospheric Inputs

Abstract. The Mediterranean reservoirs receive frequent atmospheric Saharan dust inputs with soil-derived organic components mostly during the stratification periods, when run-off inputs are particularly limited. Here, we quantified and optically characterized the water-soluble organic carbon (WSOC) of the (dry and wet) atmospheric deposition in collectors placed near three reservoirs from the western Mediterranean Basin. In addition, we determined the WSOC contribution to the pool of dissolved organic carbon (DOC) in the reservoirs and the influence of dust-derived chromophoric organic components on the water transparency during their stratification periods. We found synchronous dynamics in the WSOC atmospheric inputs among the three collectors and in the DOC concentrations among the three reservoirs. The DOC concentrations and the WSOC atmospheric inputs were positive and significantly correlated in the most oligotrophic reservoir (Quéntar) and in the reservoir with the highest ratio of surface area to mixing water depth (Cubillas). Despite these correlations, WSOC atmospheric inputs represented less than 10% of the total DOC pool, suggesting that indirect effects of dust inputs on reservoir DOC may also promote these synchronous patterns observed in the reservoirs. Chromophoric components from dust inputs can significantly reduce the water transparency to the ultraviolet radiation (UVR). The depths where UVR at λ = 320 nm was reduced to ten percent of surface intensity (Z10%) decreased 27 cm in Béznar, 49 cm in Cubillas, and 69 cm in Quéntar due to the dust inputs. Therefore, the increasing dust export to the atmosphere may have consequences for the water transparency of aquatic ecosystems located under the influence of the global dust belt.

scholarly journals Modelling organic aerosol concentrations and properties during ChArMEx summer campaigns of 2012 and 2013 in the western Mediterranean region

2017 ◽  
Vol 17 (20) ◽  
pp. 12509-12531 ◽  
Author(s):  
Mounir Chrit ◽  
Karine Sartelet ◽  
Jean Sciare ◽  
Jorge Pey ◽  
Nicolas Marchand ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Organic Aerosols ◽  
Organic Aerosol ◽  
Western Mediterranean ◽  
Water Soluble ◽  
Oxidation Products ◽  
Organic Nitrate ◽  
Air Quality Model ◽  
Remote Site ◽  
Quality Model

Abstract. In the framework of the Chemistry-Aerosol Mediterranean Experiment, a measurement site was set up at a remote site (Ersa) on Corsica Island in the northwestern Mediterranean Sea. Measurement campaigns performed during the summers of 2012 and 2013 showed high organic aerosol concentrations, mostly from biogenic origin. This work aims to represent the organic aerosol concentrations and properties (oxidation state and hydrophilicity) using the air-quality model Polyphemus with a surrogate approach for secondary organic aerosol (SOA) formation. Biogenic precursors are isoprene, monoterpenes and sesquiterpenes. In this work, the following model oxidation products of monoterpenes are added: (i) a carboxylic acid (MBTCA) to represent multi-generation oxidation products in the low-NOx regime, (ii) organic nitrate chemistry and (iii) extremely low-volatility organic compounds (ELVOCs) formed by ozonolysis. The model shows good agreement of measurements of organic concentrations for both 2012 and 2013 summer campaigns. The modelled oxidation property and hydrophilic organic carbon properties of the organic aerosols also agree reasonably well with the measurements. The influence of the different chemical processes added to the model on the oxidation level of organics is studied. Measured and simulated water-soluble organic carbon (WSOC) concentrations show that even at a remote site next to the sea, about 64 % of the organic carbon is soluble. The concentrations of WSOC vary with the origins of the air masses and the composition of organic aerosols. The marine organic emissions only contribute to a few percent of the organic mass in PM1, with maxima above the sea.

scholarly journals Contribution of dust inputs to dissolved organic carbon and water transparency in Mediterranean reservoirs

2012 ◽  
Vol 9 (7) ◽  
pp. 8307-8336
Author(s):  
I. de Vicente ◽  
E. Ortega-Retuerta ◽  
R. Morales-Baquero ◽  
I. Reche
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Organic Compounds ◽  
Western Mediterranean ◽  
Water Soluble ◽  
Water Transparency ◽  
Saharan Dust ◽  
Western Mediterranean Basin ◽  
Run Off ◽  
Atmospheric Inputs

Abstract. Mediterranean reservoirs receive frequent Saharan dust inputs with soil-derived organic compounds mostly during stratification periods, when run-off inputs are particularly limited. Here, we quantified and optically characterized the water-soluble organic carbon (WSOC) of the (dry and wet) atmospheric deposition in collectors located near three reservoirs from the Western Mediterranean Basin. In addition, we determined, during the stratification period, the WSOC contribution to the pool of dissolved organic carbon (DOC) and the influence of the chromophoric organic compounds from the dust on water transparency. We found synchrony both in the WSOC atmospheric inputs among collectors and in the DOC dynamics among the three reservoirs. DOC concentrations and WSOC atmospheric inputs were positive and significantly correlated in the two reservoirs more sensitive to atmospheric inputs: the most oligotrophic reservoir (Quentar) and the reservoir with the highest ratio of surface area to mixing water depth (Cubillas). Nevertheless, WSOC atmospheric inputs, during the stratification period, represented less than 10 % of the total DOC pool, suggesting that indirect effects of dust inputs such as primary productivity stimulation may also induce these synchronic patterns. Chromophoric compounds from dust inputs can significantly reduce water transparency to ultraviolet radiation (UVR). The depths where UVR at λ = 320 nm is reduced to ten percent of surface intensity (Z10 %) decreased 15 cm (about 24 %) in Beznar, 17 cm (about 27 %) in Cubillas, and 43 cm (about 39 %) in Quéntar due to dust inputs.

scholarly journals Characterization of Aerosol Composition, Aerosol Acidity and Organic Acid Partitioning at an Agriculture-Intensive Rural Southeastern U.S. Site

2018 ◽  
Author(s):  
Theodora Nah ◽  
Hongyu Guo ◽  
Amy P. Sullivan ◽  
Yunle Chen ◽  
David J. Tanner ◽  
...  
Keyword(s):  
Oxalic Acid ◽  
Organic Acids ◽  
Organic Acid ◽  
Organic Aerosol ◽  
Water Soluble ◽  
Molar Concentration ◽  
Particle Phase ◽  
Aerosol Composition ◽  
Phase Water ◽  
Acetic Acids

Abstract. The implementation of stringent emission regulations has resulted in the decline of anthropogenic pollutants including sulfur dioxide (SO2), nitrogen oxides (NOx) and carbon monoxide (CO). In contrast, ammonia (NH3) emissions are largely unregulated, with emissions projected to increase in the future. We present real-time aerosol and gas measurements from a field study conducted in an agricultural-intensive region in the southeastern U.S. during the fall of 2016 to investigate how NH3 affects particle acidity and SOA formation via the gas-particle partitioning of semi-volatile organic acids. Particle water and pH were determined using the ISORROPIA-II thermodynamic model and validated by comparing predicted inorganic HNO3-NO3− and NH3-NH4+ gas-particle partitioning ratios with measured values. Our results showed that despite the high NH3 concentrations (study average 8.1 ± 5.2 ppb), PM1 were highly acidic with pH values ranging from 0.9 to 3.8, and a study-averaged pH of 2.2 ± 0.6. PM1 pH varied by approximately 1.4 units diurnally. Formic and acetic acids were the most abundant gas-phase organic acids, and oxalate was the most abundant particle-phase water-soluble organic acid anion. Measured particle-phase water-soluble organic acids were on average 6 % of the total non-refractory PM1 organic aerosol mass. The measured molar fraction of oxalic acid in the particle phase (i.e., particle-phase oxalic acid molar concentration divided by the total oxalic acid molar concentration) ranged between 47 and 90 % for PM1 pH 1.2 to 3.4. The measured oxalic acid gas-particle partitioning ratios were in good agreement with their corresponding thermodynamic predictions, calculated based on oxalic acid’s physicochemical properties, ambient temperature, particle water and pH. In contrast, gas-particle partitioning of formic and acetic acids were not well predicted for reasons currently unknown. For this study, higher NH3 concentrations relative to what has been measured in the region in previous studies had minor effects on PM1 organic acids and their influence on the overall organic aerosol and PM1 mass concentrations.

scholarly journals Towards a quasi-complete reconstruction of past atmospheric aerosol load and composition (organic and inorganic) over Europe since 1920 inferred from Alpine ice cores

2013 ◽  
Vol 9 (4) ◽  
pp. 1403-1416 ◽  
Author(s):  
S. Preunkert ◽  
M. Legrand
Keyword(s):  
World War Ii ◽  
Organic Carbon ◽  
Atmospheric Aerosol ◽  
Ice Core ◽  
Ice Cores ◽  
Organic Aerosol ◽  
Water Soluble ◽  
Climate Forcing ◽  
World War ◽  
Ice Core Records

Abstract. Seasonally resolved chemical ice core records available from the Col du Dôme glacier (4250 m elevation, French Alps), are here used to reconstruct past aerosol load and composition of the free European troposphere from before World War II to present. Available ice core records include inorganic (Na+, Ca2+, NH4+, Cl−, NO3−, and SO42−) and organic (carboxylates, HCHO, humic-like substances, dissolved organic carbon, water-insoluble organic carbon, and black carbon) compounds and fractions that permit reconstructing the key aerosol components and their changes over the past. It is shown that the atmospheric load of submicron aerosol has been increased by a factor of 3 from the 1921–1951 to 1971–1988 years, mainly as a result of a large increase of sulfate (a factor of 5), ammonium and water-soluble organic aerosol (a factor of 3). Thus, not only growing anthropogenic emissions of sulfur dioxide and ammonia have caused the enhancement of the atmospheric aerosol load but also biogenic emissions producing water-soluble organic aerosol. This unexpected change of biospheric source of organic aerosol after 1950 needs to be considered and further investigated in scenarios dealing with climate forcing by atmospheric aerosol.

scholarly journals On the implications of aerosol liquid water and phase separation for organic aerosol mass

2017 ◽  
Vol 17 (1) ◽  
pp. 343-369 ◽  
Author(s):  
Havala O. T. Pye ◽  
Benjamin N. Murphy ◽  
Lu Xu ◽  
Nga L. Ng ◽  
Annmarie G. Carlton ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Organic Compounds ◽  
Water Uptake ◽  
Liquid Water ◽  
Transport Model ◽  
Organic Aerosol ◽  
Water Soluble ◽  
Organic Nitrates ◽  
Monitoring Networks ◽  
Chemical Transport Model

Abstract. Organic compounds and liquid water are major aerosol constituents in the southeast United States (SE US). Water associated with inorganic constituents (inorganic water) can contribute to the partitioning medium for organic aerosol when relative humidities or organic matter to organic carbon (OM ∕ OC) ratios are high such that separation relative humidities (SRH) are below the ambient relative humidity (RH). As OM ∕ OC ratios in the SE US are often between 1.8 and 2.2, organic aerosol experiences both mixing with inorganic water and separation from it. Regional chemical transport model simulations including inorganic water (but excluding water uptake by organic compounds) in the partitioning medium for secondary organic aerosol (SOA) when RH  >  SRH led to increased SOA concentrations, particularly at night. Water uptake to the organic phase resulted in even greater SOA concentrations as a result of a positive feedback in which water uptake increased SOA, which further increased aerosol water and organic aerosol. Aerosol properties, such as the OM ∕ OC and hygroscopicity parameter (κorg), were captured well by the model compared with measurements during the Southern Oxidant and Aerosol Study (SOAS) 2013. Organic nitrates from monoterpene oxidation were predicted to be the least water-soluble semivolatile species in the model, but most biogenically derived semivolatile species in the Community Multiscale Air Quality (CMAQ) model were highly water soluble and expected to contribute to water-soluble organic carbon (WSOC). Organic aerosol and SOA precursors were abundant at night, but additional improvements in daytime organic aerosol are needed to close the model–measurement gap. When taking into account deviations from ideality, including both inorganic (when RH  >  SRH) and organic water in the organic partitioning medium reduced the mean bias in SOA for routine monitoring networks and improved model performance compared to observations from SOAS. Property updates from this work will be released in CMAQ v5.2.

scholarly journals Mass absorption efficiency of elemental carbon and water-soluble organic carbon in Beijing, China

2011 ◽  
Vol 11 (22) ◽  
pp. 11497-11510 ◽  
Author(s):  
Y. Cheng ◽  
K.-B. He ◽  
M. Zheng ◽  
F.-K. Duan ◽  
Z.-Y. Du ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Biomass Burning ◽  
Light Absorption ◽  
Elemental Carbon ◽  
Organic Aerosol ◽  
Absorption Efficiency ◽  
Water Soluble ◽  
Water Soluble Organic Carbon ◽  
Soluble Organic Carbon ◽  
Mass Absorption Efficiency

Abstract. The mass absorption efficiency (MAE) of elemental carbon (EC) in Beijing was quantified using a thermal-optical carbon analyzer. The MAE measured at 632 nm was 8.45±1.71 and 9.41±1.92 m2 g−1 during winter and summer respectively. The daily variation of MAE was found to coincide with the abundance of organic carbon (OC), especially the OC to EC ratio, perhaps due to the enhancement by coating with organic aerosol (especially secondary organic aerosol, SOA) or the artifacts resulting from the redistribution of liquid-like organic particles during the filter-based absorption measurements. Using a converting approach that accounts for the discrepancy caused by measurements methods of both light absorption and EC concentration, previously published MAE values were converted to the equivalent-MAE, which is the estimated value if using the same measurement methods as used in this study. The equivalent-MAE was found to be much lower in the regions heavily impacted by biomass burning (e.g., below 2.7 m2 g−1 for two Indian cities). Results from source samples (including diesel exhaust samples and biomass smoke samples) also demonstrated that emissions from biomass burning would decrease the MAE of EC. Moreover, optical properties of water-soluble organic carbon (WSOC) in Beijing were presented. Light absorption by WSOC exhibited strong wavelength (λ) dependence such that absorption varied approximately as λ−7, which was characteristic of the brown carbon spectra. The MAE of WSOC (measured at 365 nm) was 1.79±0.24 and 0.71±0.20 m2 g−1 during winter and summer respectively. The large discrepancy between the MAE of WSOC during winter and summer was attributed to the difference in the precursors of SOA such that anthropogenic volatile organic compounds (AVOCs) should be more important as the precursors of SOA in winter. The MAE of WSOC in Beijing was much higher than results from the southeastern United States which were obtained using the same method as used in this study, perhaps due to the stronger emissions of biomass burning in China.

scholarly journals Construction of soil defined media using quantitative exometabolomic analysis of soil metabolites

2017 ◽  
Author(s):  
Stefan Jenkins ◽  
Tami L Swenson ◽  
Rebecca Lau ◽  
Andrea Rocha ◽  
Alex Aaring ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Molecular Weight ◽  
Organic Carbon ◽  
Quantitative Information ◽  
Water Soluble ◽  
Gas Chromatography Mass Spectrometry ◽  
Isolation And Characterization ◽  
Defined Media ◽  
Chromatography Mass Spectrometry

Exometabolomics enables analysis of metabolite utilization of low molecular weight organic substances by soil isolates. Environmentally-based defined media are needed to examine ecologically relevant patterns of substrate utilization. Here, we describe an approach for the construction of defined media using untargeted characterization of water soluble soil metabolites. To broadly characterize soil metabolites, both liquid chromatography mass spectrometry (LC/MS) and gas chromatography mass spectrometry (GC/MS) were used. With this approach, 96 metabolites were identified, including amino acids, amino acid derivatives, sugars, sugar alcohols, mono- and di-carboxylic acids, osmolytes, nucleobases, and nucleosides. From this pool of metabolites, 25 were quantified. Water soluble organic carbon was fractionated by molecular weight and measured to determine the fraction of carbon accounted for by the quantified metabolites. This revealed that, much like soil microbial community structures, these soil metabolites have an uneven quantitative distribution, with a single metabolite, trehalose accounting for 9.9 percent of the (< 1 kDa) water extractable organic carbon. This quantitative information was used to formulate two soil defined media (SDM), one containing 23 metabolites (SDM1) and one containing 46 (SDM2). To evaluate SDM for supporting the growth of bacteria found at this field site, we examined the growth of 30 phylogenetically diverse soil isolates obtained using standard R2A medium. The simpler SDM1 supported the growth of up to 13 isolates while the more complex SDM2 supported up to 25 isolates. One isolate, Pseudomonas corrugata strain FW300-N2E2 was selected for a time-series exometabolomics analysis to investigate SDM1 substrate preferences. Interestingly, it was found that this organism preferred lower-abundance substrates such as guanine, glycine, proline and arginine and glucose and did not utilize the more abundant substrates maltose, mannitol, trehalose and uridine. These results demonstrate the viability and utility of using exometabolomics to construct a tractable environmentally relevant media. We anticipate that this approach can be expanded to other environments to enhance isolation and characterization of diverse microbial communities.

scholarly journals Characterization and source apportionment of submicron aerosol with aerosol mass spectrometer during the PRIDE-PRD 2006 campaign

2011 ◽  
Vol 11 (14) ◽  
pp. 6911-6929 ◽  
Author(s):  
R. Xiao ◽  
N. Takegawa ◽  
M. Zheng ◽  
Y. Kondo ◽  
Y. Miyazaki ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Urban Areas ◽  
Organic Aerosol ◽  
Water Soluble ◽  
Aerosol Formation ◽  
Aerosol Mass Spectrometer ◽  
Air Masses ◽  
Submicron Aerosol ◽  
Pmf Model ◽  
Aerosol Mass

Abstract. Size-resolved chemical compositions of non-refractory submicron aerosol were measured using an Aerodyne quadrupole aerosol mass spectrometer (Q-AMS) at the rural site Back Garden (BG), located ~50 km northwest of Guangzhou in July 2006. This paper characterized the submicron aerosol particles of regional air pollution in Pearl River Delta (PRD) in the southern China. Organics and sulfate dominated the submicron aerosol compositions, with average mass concentrations of 11.8 ± 8.4 μg m−3 and 13.5 ± 8.7 μg m−3, respectively. Unlike other air masses, the air masses originated from Southeast-South and passing through the PRD urban areas exhibited distinct bimodal size distribution characteristics for both organics and sulfate: the first mode peaked at vacuum aerodynamic diameters (Dva) ∼200 nm and the second mode occurred at Dva from 300–700 nm. With the information from AMS, it was found from this study that the first mode of organics in PRD regional air masses was contributed by both secondary organic aerosol formation and combustion-related emissions, which is different from most findings in other urban areas (first mode of organics primarily from combustion-related emissions). The analysis of AMS mass spectra data by positive matrix factorization (PMF) model identified three sources of submicron organic aerosol including hydrocarbon-like organic aerosol (HOA), low volatility oxygenated organic aerosol (LV-OOA) and semi-volatile oxygenated organic aerosol (SV-OOA). The strong correlation between HOA and EC indicated primary combustion emissions as the major source of HOA while a close correlation between SV-OOA and semi-volatile secondary species nitrate as well as between LV-OOA and nonvolatile secondary species sulfate suggested secondary aerosol formation as the major source of SV-OOA and LV-OOA at the BG site. However, LV-OOA was more aged than SV-OOA as its spectra was highly correlated with the reference spectra of fulvic acid, an indicator of aged and oxygenated aerosol. The origin of HOA and OOA (the sum of LV-OOA and SV-OOA) has been further confirmed by the statistics that primary organic carbon (POC) and secondary organic carbon (SOC), estimated by the EC tracer method, were closely correlated with HOA and OOA, respectively. The results of the EC tracer method and of the PMF model revealed that primary organic aerosol (POA) constituted ~34–47 % of OA mass and secondary organic aerosol (SOA) constituted ~53–66 % of regional organic aerosol in PRD during summer season. The presence of abundant SOA was consistent with water soluble organic carbon (WSOC) results (accounting for ~60 % of OC on average) by Miyazaki et al. (2009) for the same campaign. OOA correlated well with WSOC at the BG site, indicating that most OOA were water soluble. More specifically, approximately 86 % of LV-OOA and 61 % of SV-OOA were estimated as water soluble species on the basis of carbon content comparison.

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