scholarly journals Chemical composition and size distribution of summertime PM<sub>2.5</sub> at a high altitude remote location in the northeast of the Qinghai–Xizang (Tibet) Plateau: insights into aerosol sources and processing in free troposphere

2015 ◽  
Vol 15 (9) ◽  
pp. 5069-5081 ◽  
Author(s):  
J. Z. Xu ◽  
Q. Zhang ◽  
Z. B. Wang ◽  
G. M. Yu ◽  
X. L. Ge ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Organic Carbon ◽  
High Elevation ◽  
Water Soluble ◽  
Tibet Plateau ◽  
Size Distributions ◽  
Total Organic Nitrogen ◽  
Accumulation Mode ◽  
Average Mass ◽  
Tropospheric Aerosols

Abstract. Aerosol filter samples were collected at a high-elevation mountain observatory (4180 m a.s.l.) in the northeastern part of the Qinghai–Xizang (Tibet) Plateau (QXP) during summer 2012 using a low-volume sampler and a micro-orifice uniform deposit impactor (MOUDI). These samples were analyzed for water-soluble inorganic ions (WSIs), organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), and total organic nitrogen (TON) to elucidate the size-resolved chemical composition of free tropospheric aerosols in the QXP region. The average mass concentration of the sum of the analyzed species in PM2.5 (particle matter) (WSIs + OC + EC + TON) was 3.74 μg sm−3, 36% of which was sulfate, 18% OC, 17 % nitrate, 10% ammonium, 6.6% calcium, 6.4% TON, 2.6% EC, 1.5 % sodium, 0.9% chloride, 0.5% magnesium, and 0.3% potassium. The size distributions of sulfate and ammonium peaked in the accumulation mode (0.32–0.56 μm), whereas the size distributions of both nitrate and calcium peaked in the range of 1.8–3.2 μm, suggesting the formation of nitrate on mineral dust. OC, EC and TON were also predominantly found in the accumulation mode. The bulk chemical composition and the average oxidation degree of water-soluble organic matter (WSOM) were assessed using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). WSOM was found to be highly oxidized in all PM2.5 samples with an average oxygen-to-carbon atomic ratio (O / C) of 1.16 and an organic mass-to-organic carbon ratio (OM / OC) of 2.75. The highly oxidized WSOM was likely related to active cloud processing during upslope air mass transport coupled with strongly oxidizing environments caused by snow/ice photochemistry. High average ratios of OC / EC (7.6) and WSOC / OC (0.79) suggested that organic aerosols were primarily made of secondary species. Secondary organic aerosol (SOA) was estimated on average accounting for 80% (62–96%) of the PM2.5, indicating that SOA is an important component of free tropospheric aerosols over the northern QXP.

scholarly journals Insights into the chemical composition of summertime PM<sub>2.5</sub> at the northeast of the Qinghai-Xizang (Tibet) Plateau

2015 ◽  
Vol 15 (1) ◽  
pp. 1307-1341
Author(s):  
J. Xu ◽  
Q. Zhang ◽  
Z. Wang ◽  
G. Yu ◽  
X. Ge ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Organic Carbon ◽  
Organic Aerosol ◽  
High Elevation ◽  
Water Soluble ◽  
Tibet Plateau ◽  
Total Organic Nitrogen ◽  
Accumulation Mode ◽  
Average Mass ◽  
Tropospheric Aerosols

Abstract. Aerosol filter samples were collected at a high-elevation mountain observatory in the northeastern part of the Qinghai-Xizang (Tibet) Plateau (QXP) during summer 2012 using a low-volume sampler and a micro-orifice uniform deposit impactor (MOUDI). The aim was to improve our understanding of the chemical composition of free tropospheric aerosols in the QXP region. The samples were analyzed for water-soluble inorganic ions (WSIs), organic carbon (OC), elemental carbon (EC), water soluble organic carbon (WSOC), and total organic nitrogen (TON). The bulk chemical composition and the average oxidation degree of water-soluble organic matter (WSOM) were assessed using a high resolution time-of-flight aerosol mass spectrometer. Furthermore, the concentrations of both primary organic aerosol (POA) and secondary organic aerosol (SOA) were estimated. The average mass concentration of the sum of the analyzed species in PM2.5 (WSIs + OC + EC + TON) was 3.74 μg m−3, 36.2% of which was sulfate, 17.8% OC, 16.9% nitrate, 10.1% ammonium, 6.6% calcium, 6.4% TON, 2.6% EC, 1.5% sodium, 0.9% chloride, 0.5% magnesium, and 0.3% potassium. The size distribution of sulfate and ammonium peaked in the accumulation mode (0.32–0.56 μm), whereas the size distributions of both nitrate and calcium peaked in the range of 1.8–3.2 μm, suggesting the formation of nitrate on mineral dust. OC, EC and TON were also predominantly found in the accumulation mode. High average ratios of OC / EC (7.6) and WSOC / OC (0.79) suggested that organic aerosols were primarily made of secondary species. WSOM was found to be highly oxidized in all PM2.5 samples with the average oxygen-to-carbon atomic ratio (O / C) being 1.16 and organic mass to carbon ratio (OM / OC) being 2.75. The highly oxidized WSOM was likely related to active cloud processing during upslope air mass transport coupled with strongly oxidizing environments caused by snow/ice photochemistry. SOA was estimated on average accounting for 75.3% (46.4–96.4%) of the PM2.5, indicating that SOA accounted for a significant portion of the free tropospheric aerosols over the northern QXP.

scholarly journals Chemical composition, microstructure, and hygroscopic properties of aerosol particles at the Zotino Tall Tower Observatory (ZOTTO), Siberia, during a summer campaign

2015 ◽  
Vol 15 (6) ◽  
pp. 7837-7893
Author(s):  
E. F. Mikhailov ◽  
G. N. Mironov ◽  
C. Pöhlker ◽  
X. Chi ◽  
M. L. Krüger ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Organic Carbon ◽  
Water Uptake ◽  
Aerosol Particles ◽  
Water Soluble ◽  
Submicron Particles ◽  
Hygroscopic Growth ◽  
Accumulation Mode ◽  
Hygroscopic Properties ◽  
Coarse Mode

Abstract. In this study we describe the hygroscopic properties of accumulation- and coarse-mode aerosol particles sampled at the Zotino Tall Tower Observatory (ZOTTO) in Central Siberia (61° N; 89° E) from 16 to 21 June 2013. The hygroscopic growth measurements were supplemented with chemical analyses of the samples, including inorganic ions and organic/elemental carbon. In addition, the microstructure and chemical composition of aerosol particles were analyzed by X-ray micro-spectroscopy (STXM-NEXAFS) and transmission electron microscopy (TEM). A mass closure analysis indicates that organic carbon accounted for 61 and 38% of PM in the accumulation mode and coarse mode, respectively. The water soluble fraction of organic matter was estimated to be 52 and 8% of PM in these modes. Sulfate, predominantly in the form of ammoniated sulfate, was the dominant inorganic component in both size modes: ∼34% in the accumulation vs. ∼47% in the coarse mode. The hygroscopic growth measurements were conducted with a filter-based differential hygroscopicity analyzer (FDHA) over the range of 5–99.4% RH in the hydration and dehydration operation modes. The FDHA study indicates that both accumulation and coarse modes exhibit pronounced water uptake approximately at the same RH, starting at ∼70%, while efflorescence occurred at different humidities, i.e., at ∼35% RH for submicron particles vs. ∼50% RH for supermicron particles. This ∼15% RH difference was attributed to higher content of organic material in the submicron particles, which suppresses water release in the dehydration experiments. The kappa mass interaction model (KIM) was applied to characterize and parameterize non-ideal solution behavior and concentration-dependent water uptake by atmospheric aerosol samples in the 5–99.4% RH range. Based on KIM, the volume-based hygroscopicity parameter, κv, was calculated. The κv, ws value related to the water soluble (ws) fraction was estimated to be ∼0.15 for the accumulation mode and ∼0.36 for the coarse mode, respectively. The obtained κv, ws for the accumulation mode is in good agreement with earlier data reported for remote sites in the Amazon rain forest (κv &amp;approx; 0.15) and a Colorado boreal forest (κv &amp;approx; 0.16). We used the Zdanovskii–Stokes–Robinson (ZSR) mixing rule to predict the chemical composition dependent hygroscopicity, κv, p. The obtained κv, p values overestimate the experimental FDHA-KIM-derived κv, ws by factors of 1.8 and 1.5 for the accumulation and coarse modes, respectively. This divergence can be partly explained by incomplete dissolution of the hygroscopic inorganic compounds resulting from kinetic limitations due to a sparingly soluble organic coating. The TEM and STXM-NEXAFS results indicate that aged submicron (>300 nm) and supermicron aerosol particles possess core-shell structures with an inorganic core, and are enriched in organic carbon at the mixed particle surface. The direct FDHA kinetic studies provide a bulk diffusion coefficient of water of ∼10−12 cm2 s−1 indicating a semi-solid state of the organic-rich phase leading to kinetic limitations of water uptake and release during hydration and dehydration cycles. Overall the present ZOTTO data set, obtained in the growing season, has revealed a strong influence of organic carbon on the hygroscopic properties of the ambient aerosols. The sparingly soluble organic coating controls hygroscopic growth, phase transitions, and microstructural rearrangement processes. The observed kinetic limitations can strongly influence the outcome of experiments performed on multi-second time scales, such as the commonly applied HTDMA (Hygroscopicity Tandem Differential Mobility Analyzer) and CCNC (Cloud Condensation Nuclei Counter) measurements.

scholarly journals Seasonal variations in PM10 inorganic composition in the Andean city

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Rasa Zalakeviciute ◽  
Katiuska Alexandrino ◽  
Yves Rybarczyk ◽  
Alexis Debut ◽  
Karla Vizuete ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Inductively Coupled Plasma ◽  
Chemical Elements ◽  
Large Fraction ◽  
Urban Pollution ◽  
Optical Emission ◽  
High Elevation ◽  
Water Soluble ◽  
Wet Season ◽  
Soluble Ions

Abstract Particulate matter (PM) is one of the key pollutants causing health risks worldwide. While the preoccupation for increased concentrations of these particles mainly depends on their sources and thus chemical composition, some regions are yet not well investigated. In this work the composition of chemical elements of atmospheric PM10 (particles with aerodynamic diameters ≤ 10 µm), collected at the urban and suburban sites in high elevation tropical city, were chemically analysed during the dry and wet seasons of 2017–2018. A large fraction (~ 68%) of PM10 composition in Quito, Ecuador is accounted for by water-soluble ions and 16 elements analysed using UV/VIS spectrophotometer and Inductively Coupled Plasma—Optical Emission Spectroscopy (ICP-OES). Hierarchical clustering analysis was performed to study a correlation between the chemical composition of urban pollution and meteorological parameters. The suburban area displays an increase in PM10 concentrations and natural elemental markers during the dry (increased wind intensity, resuspension of soil dust) season. Meanwhile, densely urbanized area shows increased total PM10 concentrations and anthropogenic elemental markers during the wet season, which may point to the worsened combustion and traffic conditions. This might indicate the prevalence of cardiovascular and respiratory problems in motorized areas of the cities in the developing world.

scholarly journals Chemical composition, microstructure, and hygroscopic properties of aerosol particles at the Zotino Tall Tower Observatory (ZOTTO), Siberia, during a summer campaign

2015 ◽  
Vol 15 (15) ◽  
pp. 8847-8869 ◽  
Author(s):  
E. F. Mikhailov ◽  
G. N. Mironov ◽  
C. Pöhlker ◽  
X. Chi ◽  
M. L. Krüger ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Water Uptake ◽  
Aerosol Particles ◽  
Organic Coating ◽  
Water Soluble ◽  
Submicron Particles ◽  
Hygroscopic Growth ◽  
Accumulation Mode ◽  
Hygroscopic Properties ◽  
Coarse Mode

Abstract. In this study we describe the hygroscopic properties of accumulation- and coarse-mode aerosol particles sampled at the Zotino Tall Tower Observatory (ZOTTO) in central Siberia (61° N, 89° E) from 16 to 21 June 2013. The hygroscopic growth measurements were supplemented with chemical analyses of the samples, including inorganic ions and organic/elemental carbon. In addition, the microstructure and chemical compositions of aerosol particles were analyzed by x-ray micro-spectroscopy (STXM-NEXAFS) and transmission electron microscopy (TEM). A mass closure analysis indicates that organic carbon accounted for 61 and 38 % of particulate matter (PM) in the accumulation mode and coarse mode, respectively. The water-soluble fraction of organic matter was estimated to be 52 and 8 % of PM in these modes. Sulfate, predominantly in the form of ammoniated sulfate, was the dominant inorganic component in both size modes: ~ 34 % in the accumulation mode vs. ~ 47 % in the coarse mode. The hygroscopic growth measurements were conducted with a filter-based differential hygroscopicity analyzer (FDHA) over the range of 5–99.4 % RH in the hydration and dehydration operation modes. The FDHA study indicates that both accumulation and coarse modes exhibit pronounced water uptake approximately at the same relative humidity (RH), starting at ~ 70 %, while efflorescence occurred at different humidities, i.e., at ~ 35 % RH for submicron particles vs. ~ 50 % RH for supermicron particles. This ~ 15 % RH difference was attributed to higher content of organic material in the submicron particles, which suppresses water release in the dehydration experiments. The kappa mass interaction model (KIM) was applied to characterize and parameterize non-ideal solution behavior and concentration-dependent water uptake by atmospheric aerosol samples in the 5–99.4 % RH range. Based on KIM, the volume-based hygroscopicity parameter, κv, was calculated. The κv,ws value related to the water-soluble (ws) fraction was estimated to be ~ 0.15 for the accumulation mode and ~ 0.36 for the coarse mode, respectively. The obtained κv,ws for the accumulation mode is in good agreement with earlier data reported for remote sites in the Amazon rain forest (κv &amp;approx; 0.15) and a Colorado mountain forest (κv &amp;approx; 0.16 ). We used the Zdanovskii–Stokes–Robinson (ZSR) mixing rule to predict the chemical composition dependent hygroscopicity, κv,p. The obtained κv,p values overestimate the experimental FDHA-KIM-derived κv,ws by factors of 1.8 and 1.5 for the accumulation and coarse modes, respectively. This divergence can be explained by incomplete dissolution of the hygroscopic inorganic compounds resulting from kinetic limitations due to a sparingly soluble organic coating. The TEM and STXM-NEXAFS results indicate that aged submicron (> 300 nm) and supermicron aerosol particles possess core–shell structures with an inorganic core, and are enriched in organic carbon at the mixed particle surface. The direct FDHA kinetic studies provide a bulk diffusion coefficient of water of ~ 10−12 cm2 s−1 indicating a semi-solid state of the organic-rich phase leading to kinetic limitations of water uptake and release during hydration and dehydration cycles. Overall, the present ZOTTO data set, obtained in the growing season, has revealed a strong influence of organic carbon on the hygroscopic properties of the ambient aerosols. The sparingly soluble organic coating controls hygroscopic growth, phase transitions, and microstructural rearrangement processes. The observed kinetic limitations can strongly influence the outcome of experiments performed on multi-second timescales, such as the commonly applied HTDMA (Hygroscopicity Tandem Differential Mobility Analyzer) and CCNC (Cloud Condensation Nuclei Counter) measurements.

scholarly journals Size distributions, sources and source areas of water-soluble organic carbon in urban background air

2008 ◽  
Vol 8 (18) ◽  
pp. 5635-5647 ◽  
Author(s):  
H. Timonen ◽  
S. Saarikoski ◽  
O. Tolonen-Kivimäki ◽  
M. Aurela ◽  
K. Saarnio ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Inorganic Ions ◽  
Water Soluble ◽  
Size Distributions ◽  
Wood Combustion ◽  
Urban Background ◽  
Source Areas ◽  
Water Soluble Organic Carbon ◽  
Soluble Organic Carbon ◽  
Different Sources

Abstract. This paper represents the results of one year long measurement period of the size distributions of water-soluble organic carbon (WSOC), inorganic ions and gravimetric mass of particulate matter. Measurements were done at an urban background station (SMEAR III) by using a micro-orifice uniform deposit impactor (MOUDI). The site is located in northern European boreal region in Helsinki, Finland. The WSOC size distribution measurements were completed with the chemical analysis of inorganic ions, organic carbon (OC) and monosaccharide anhydrides from the filter samples (particle aerodynamic diameter smaller than 1 μm, PM1). Gravimetric mass concentration varied during the MOUDI samplings between 3.4 and 55.0 μg m−3 and the WSOC concentrations were between 0.3 and 7.4 μg m−3. On average, water-soluble particulate organic matter (WSPOM, WSOC multiplied by 1.6 to convert the analyzed carbon mass to organic matter mass) comprised 25±7.7% and 7.5±3.4% of aerosol PM1 mass and the PM1–10 mass, respectively. Inorganic ions contributed 33±12% and 28±19% of the analyzed PM1 and PM1–10 aerosol mass. Five different aerosol categories corresponding to different sources or source areas were identified (long-range transport aerosols, biomass burning aerosols from wild land fires and from small-scale wood combustion, aerosols originating from marine areas and from the clean arctic areas). Categories were identified mainly using levoglucosan concentration level for wood combustion and air mass backward trajectories for other groups. Clear differences in WSOC concentrations and size distributions originating from different sources or source areas were observed, although there are also many other factors which might affect the results. E.g. the local conditions and sources of volatile organic compounds (VOCs) and aerosols as well as various transformation processes are likely to have an impact on the measured aerosol composition. Using the source categories, it was identified that especially the oxidation products of biogenic VOCs in summer had a clear effect on WSOC concentrations.

scholarly journals Dicarboxylic acids, oxoacids, benzoic acid, <i>α</i>-dicarbonyls, WSOC, OC, and ions in spring aerosols from Okinawa Island in the western North Pacific Rim: size distributions and formation processes

2016 ◽  
Vol 16 (8) ◽  
pp. 5263-5282 ◽  
Author(s):  
Dhananjay K. Deshmukh ◽  
Kimitaka Kawamura ◽  
Manuel Lazaar ◽  
Bhagawati Kunwar ◽  
Suresh K. R. Boreddy
Keyword(s):  
Organic Carbon ◽  
Benzoic Acid ◽  
Biomass Burning ◽  
Unsaturated Fatty Acids ◽  
Glyoxylic Acid ◽  
Water Soluble ◽  
Size Distributions ◽  
Strong Correlations ◽  
Coarse Mode ◽  
Fine Mode

Abstract. Size-segregated aerosols (nine stages from < 0.43 to > 11.3 µm in diameter) were collected at Cape Hedo, Okinawa, in spring 2008 and analyzed for water-soluble diacids (C2–C12), ω-oxoacids (ωC2–ωC9), pyruvic acid, benzoic acid, and α-dicarbonyls (C2–C3) as well as water-soluble organic carbon (WSOC), organic carbon (OC), and major ions (Na+, NH4+, K+, Mg2+, Ca2+, Cl−, NO3−, SO42−, and MSA−). In all the size-segregated aerosols, oxalic acid (C2) was found to be the most abundant species, followed by malonic and succinic acids, whereas glyoxylic acid (ωC2) was the dominant oxoacid and glyoxal (Gly) was more abundant than methylglyoxal. Diacids (C2–C5), ωC2, and Gly as well as WSOC and OC peaked at fine mode (0.65–1.1 µm) whereas azelaic (C9) and 9-oxononanoic (ωC9) acids peaked at coarse mode (3.3–4.7 µm). Sulfate and ammonium were enriched in fine mode, whereas sodium and chloride were in coarse mode. Strong correlations of C2–C5 diacids, ωC2 and Gly with sulfate were observed in fine mode (r =  0.86–0.99), indicating a commonality in their secondary formation. Their significant correlations with liquid water content in fine mode (r =  0.82–0.95) further suggest an importance of the aqueous-phase production in Okinawa aerosols. They may also have been directly emitted from biomass burning in fine mode as supported by strong correlations with potassium (r =  0.85–0.96), which is a tracer of biomass burning. Bimodal size distributions of longer-chain diacid (C9) and oxoacid (ωC9) with a major peak in the coarse mode suggest that they were emitted from the sea surface microlayers and/or produced by heterogeneous oxidation of biogenic unsaturated fatty acids on sea salt particles.

scholarly journals CHEMICAL COMPOSITION OF AEROSOLS IN THE WEST COAST OF TAIWAN STRAIT, CHINA

2019 ◽  
Vol XLII-3/W9 ◽  
pp. 233-237
Author(s):  
L. Zhao ◽  
C. Yang
Keyword(s):  
Chemical Composition ◽  
Mass Spectrometer ◽  
Single Particle ◽  
Inorganic Ions ◽  
Water Soluble ◽  
Ion Concentration ◽  
Aerosol Mass Spectrometer ◽  
Average Mass ◽  
Inorganic Ion ◽  
Aerosol Mass

Abstract. The chemical composition of aerosols was investigated using regular environmental air quality observation, a single particle aerosol mass spectrometer (SPAMS 0515) and an ambient ion monitor (URG 9000D) in Xiamen in 2018. The results showed that the annual average mass concentrations of PM2.5 was 22 μm/m3, and concentrations of water-soluble inorganic ions was 9.94 μm/m3 which accounted for 45.2% of PM2.5. SO42−, NO3− and NH4+ were main components of secondary reactions which contributed more than 77 percent of water-soluble inorganic ion concentration. As a coastal city, Cl− and Na+ contributed 13.9 percent of water-soluble inorganic ion concentration. Based on single particle aerosol mass spectrometer analysing, mobile sources emission was the most important sources of particle matter which contributed over 30%.

scholarly journals Chemical composition and aerosol size distribution of the middle mountain range in the Nepal Himalayas during the 2009 pre-monsoon season

2010 ◽  
Vol 10 (6) ◽  
pp. 15629-15670
Author(s):  
P. Shrestha ◽  
A. P. Barros ◽  
A. Khlystov
Keyword(s):  
Boundary Layer ◽  
Chemical Composition ◽  
Organic Carbon ◽  
Size Distribution ◽  
Elemental Carbon ◽  
Monsoon Season ◽  
Number Concentration ◽  
Water Soluble ◽  
Aerosol Size Distribution ◽  
Aerosol Number Concentration

Abstract. Aerosol particle number size distribution and chemical composition were measured at two low altitude sites, one urban and one relatively pristine valley, in Central Nepal during the 2009 pre-monsoon season (May–June). This is the first time that aerosol size distribution and chemical composition were measured simultaneously at lower elevation in the Middle Himalayan region in Nepal. The aerosol size distribution was measured using a Scanning Mobility Particle Sizer (SMPS, 14~340 nm), and the chemical composition of the filter samples collected during the field campaign was analyzed in the laboratory. Teflon membrane filters were used for ion chromatography (IC) and water-soluble organic carbon and nitrogen analysis. Quartz fiber filters were used for organic carbon and elemental carbon analysis. Multi-lognormal fits to the measured aerosol size distribution indicated a consistent larger mode around 100 nm which is usually the oldest, most processed background aerosol. The smaller mode was located around 20 nm, which is indicative of fresh but not necessarily local aerosol. The diurnal cycle of the aerosol number concentration showed the presence of two peaks (early morning and evening), during the transitional period of boundary layer growth and collapse. The increase in number concentration during the peak period was observed for the entire size distribution. Although the possible contribution of local emissions in size ranges similar to the larger mode cannot be completely ruled out, another plausible explanation is the mixing of aged elevated aerosol in the residual layer during the morning period as suggested by previous studies. Similarly, the evening time concentration peaks when the boundary layer becomes shallow concurrent with increase in local activity. A decrease in aerosol number concentration was observed during the nighttime with the development of cold (downslope) mountain winds that force the low level warmer air in the valley to rise. The mountain valley wind mechanisms induced by the topography along with the valley geometry appear to have a strong control in the diurnal cycle of the aerosol size distribution. During the sampling period, the chemical composition of PM2.5 was dominated by organic matter at both sites. Organic carbon (OC) comprised the major fraction (64~68%) of the aerosol concentration followed by ionic species (24~26% mainly SO42- and NH4+). Elemental Carbon (EC) compromised 7~10% of the total composition. A large fraction of OC was found to be water soluble (nearly 27% at both sites).

scholarly journals Size distributions, sources and source areas of water-soluble organic carbon in urban background air

2008 ◽  
Vol 8 (2) ◽  
pp. 7847-7881 ◽  
Author(s):  
H. Timonen ◽  
S. Saarikoski ◽  
O. Tolonen-Kivimäki ◽  
M. Aurela ◽  
K. Saarnio ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Inorganic Ions ◽  
Water Soluble ◽  
Small Scale ◽  
Size Distributions ◽  
Urban Background ◽  
Source Areas ◽  
Water Soluble Organic Carbon ◽  
Soluble Organic Carbon ◽  
Different Sources

Abstract. This paper represents the results of one year long measurement period of the size distributions of water-soluble organic carbon (WSOC), inorganic ions and gravimetric mass of particulate matter. Measurements were done at an urban background station (SMEAR III) by using a micro-orifice uniform deposit impactor (MOUDI). The site is located in northern European boreal region in Helsinki, Finland. The WSOC size distribution measurements were completed with the chemical analysis of inorganic ions, organic carbon (OC) and monosaccharide anhydrides from the filter samples. During the measurements gravimetric mass in the MOUDI collections varied between 3.4 and 55.0 μg m−3 and the WSOC concentration was between 0.3 and 7.4 μg m−3. On average, water-soluble particulate organic matter (WSPOM, WSOC multiplied by 1.6) comprised 25±7.7% and 7.5±3.4% of aerosol PM1 mass and the PM1−10 mass, respectively. Inorganic ions contributed 33±12% and 28±19% of the analyzed PM1 and PM1−10 aerosol mass. Five different aerosol categories corresponding to different sources or source areas were identified (long-range transport aerosols, biomass burning aerosols from wild land fires and from small-scale wood combustion, aerosols originating from marine areas and from the clean arctic areas). Clear differences in WSOC concentrations and size distributions originating from different sources or source areas were observed, although there are also many other factors which might affect the results. E.g. the local conditions and sources of volatile organic compounds (VOCs) and aerosols as well as various transformation processes are likely to have an impact on the measured aerosol composition. Using the source categories, it was identified that especially the oxidation products of biogenic VOCs in summer had a clear effect on WSOC concentrations.

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