Photochemical aging of aerosol particles in different air masses arriving at Baengnyeong Island, Korea

Abstract. Atmospheric aerosol particles are a serious health risk, especially in regions like East Asia. We investigated the photochemical aging of ambient aerosols using a potential aerosol mass (PAM) reactor at Baengnyeong Island in the Yellow Sea during 4–12 August 2011. The size distributions and chemical compositions of aerosol particles were measured alternately every 6 min from the ambient air or through the highly oxidizing environment of a potential aerosol mass (PAM) reactor. Particle size and chemical composition were measured by using the combination of a scanning mobility particle sizer (SMPS) and a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Inside the PAM reactor, O3 and OH levels were equivalent to 4.6 days of integrated OH exposure at typical atmospheric conditions. Two types of air masses were distinguished on the basis of the chemical composition and the degree of aging: air transported from China, which was more aged with a higher sulfate concentration and O  :  C ratio, and the air transported across the Korean Peninsula, which was less aged with more organics than sulfate and a lower O  :  C ratio. For both episodes, the particulate sulfate mass concentration increased in the 200–400 nm size range when sampled through the PAM reactor. A decrease in organics was responsible for the loss of mass concentration in 100–200 nm particles when sampled through the PAM reactor for the organics-dominated episode. This loss was especially evident for the m∕z 43 component, which represents less oxidized organics. The m∕z 44 component, which represents further oxidized organics, increased with a shift toward larger sizes for both episodes. It is not possible to quantify the maximum possible organic mass concentration for either episode because only one OH exposure of 4.6 days was used, but it is clear that SO2 was a primary precursor of secondary aerosol in northeast Asia, especially during long-range transport from China. In addition, inorganic nitrate evaporated in the PAM reactor as sulfate was added to the particles. These results suggest that the chemical composition of aerosols and their degree of photochemical aging, particularly for organics, are also crucial in determining aerosol mass concentrations.

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Photochemical aging of organic and inorganic ambient aerosol from the Potential Aerosol Mass (PAM) reactor experiment in East Asia

10.5194/acp-2016-1133 ◽

2017 ◽

Cited By ~ 2

Author(s):

Eunha Kang ◽

Meehye Lee ◽

William H. Brune ◽

Taehyung Lee ◽

Joonyoung Ahn

Keyword(s):

Chemical Composition ◽

Cloud Condensation Nuclei ◽

Northeast Asia ◽

The Yellow Sea ◽

Chemical Compositions ◽

Atmospheric Conditions ◽

Scanning Mobility Particle Sizer ◽

Volatile Organics ◽

Aerosol Mass ◽

Photochemical Aging

Abstract. We investigated the photochemical aging of ambient aerosols using a potential aerosol mass (PAM) reactor at Baegryeong Island in the Yellow Sea during August 4–12, 2011. The size distributions and chemical compositions of the ambient and aged PAM aerosols were measured alternately every 6 min by Scanning Mobility Particle Sizer (SMPS) and High Resolution-Time of Flight-Aerosol Mass Spectrometer (HR-ToF-AMS), respectively. Inside the PAM reactor, the O3 and OH levels were equivalent to approximately 5 days of integrated OH exposure at typical atmospheric conditions. Two types of air masses were distinguished on the basis of the chemical composition and the degree of aging: Sulfate was predominant with higher O : C ratio for the air transported from China and organic concentration was higher than that of sulfate with lower O : C ratio when the air came through the Korean Peninsula. In PAM reactor, sulfate was constantly formed, resulting in the increase of particle mass at 200–400 nm size range. Organics were responsible for an overall loss of mass in 100–200 nm particles. This loss was especially evident for the m/z 43 component representing semi-volatile organics. Conversely, the m/z 44 component corresponding to low-volatile organics increased with a shift toward larger sizes during the organics-dominated episode. Therefore, we hypothesize that the oxidation of semi-volatile organics was facilitated by gas-phase oxidation and partitioning for re-equilibrium between the gas and particle phases. Nitrate evaporated in the PAM reactor upon the addition of sulfate to the particles. These results suggest that the chemical composition of aerosols and their degree of photochemical aging particularly for organics are also crucial in determining aerosol mass concentrations. Because sulfate in the atmosphere was stable for about a week of the nominal lifetime of aerosols, SO2 is a unquestionably primary precursor of secondary aerosol in northeast Asia. In comparison, the contribution of organics to secondary aerosols is more variable during transport in the atmosphere. Notably, an increase in low-volatility organics was associated with sulfate and evident at 200–400 nm, highlighting the role of secondary organic aerosol (SOA) in cloud condensation nuclei (CCN) formation.

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Relationship between the Optical Properties and Chemical Composition of Urban Aerosol Particles in Lithuania

Advances in Meteorology ◽

10.1155/2018/8674173 ◽

2018 ◽

Vol 2018 ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Julija Pauraite ◽

Kristina Plauškaitė ◽

Vadimas Dudoitis ◽

Vidmantas Ulevicius

Keyword(s):

Optical Properties ◽

Chemical Composition ◽

Organic Aerosol ◽

Single Scattering ◽

Chemical Compositions ◽

Spectra Analysis ◽

Average Value ◽

Aerosol Mass ◽

In Situ Investigation

In situ investigation results of aerosol optical properties (absorption and scattering) and chemical composition at an urban background site in Lithuania (Vilnius) are presented. Investigation was performed in May-June 2017 using an aerosol chemical speciation monitor (ACSM), a 7-wavelength Aethalometer and a 3-wavelength integrating Nephelometer. A positive matrix factorisation (PMF) was used for the organic aerosol mass spectra analysis to characterise the sources of ambient organic aerosol (OA). Five OA factors were identified: hydrocarbon-like OA (HOA), biomass-burning OA (BBOA), more and less oxygenated OA (LVOOA and SVOOA, respectively), and local hydrocarbon-like OA (LOA). The average absorption (at 470 nm) and scattering (at 450 nm) coefficients during the entire measurement campaign were 16.59 Mm−1 (standard deviation (SD) = 17.23 Mm−1) and 29.83 Mm−1 (SD = 20.45 Mm−1), respectively. Furthermore, the absorption and scattering Angström exponents (AAE and SAE, respectively) and single-scattering albedo (SSA) were calculated. The average AAE value at 470/660 nm was 0.97 (SD = 0.16) indicating traffic-related black carbon (BCtr) dominance. The average value of SAE (at 450/700 nm) was 1.93 (SD = 0.32) and could be determined by the submicron particle (PM1) dominance versus the supermicron ones (PM > 1 µm). The average value of SSA was 0.62 (SD = 0.13). Several aerosol types showed specific segregation in the SAE versus SSA plot, which underlines different optical properties due to various chemical compositions.

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Processing of biomass burning aerosol in the Eastern Mediterranean during summertime

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-25969-2013 ◽

2013 ◽

Vol 13 (10) ◽

pp. 25969-25999 ◽

Cited By ~ 2

Author(s):

A. Bougiatioti ◽

I. Stavroulas ◽

E. Kostenidou ◽

P. Zarmpas ◽

C. Theodosi ◽

...

Keyword(s):

Chemical Composition ◽

Biomass Burning ◽

Eastern Mediterranean ◽

Late Summer ◽

Organic Aerosol ◽

High Temporal Resolution ◽

Night Time ◽

Air Masses ◽

Aerosol Mass ◽

Atmospheric Processing

Abstract. The aerosol chemical composition in air masses affected by wildfires from the Greek islands of Chios, Euboea and Andros, the Dalmatian Coast and Sicily, during late summer of 2012 was characterized at the remote background site of Finokalia, Crete. Air masses were transported several hundreds of kilometers, arriving at the measurement station after approximately half a day of transport, mostly during night-time. The chemical composition of the particulate matter was studied by different high temporal resolution instruments, including an Aerosol Chemical Speciation Monitor (ACSM) and a seven-wavelength aethalometer. Despite the large distance from emission and long atmospheric processing, a clear biomass burning organic aerosol (BBOA) profile containing characteristic markers is derived from BC measurements and Positive Matrix Factorization (PMF) analysis of the ACSM mass spectra. The ratio of fresh to aged BBOA decreases with increasing atmospheric processing time and BBOA components appear to be converted to oxygenated organic aerosol (OOA). Given that the smoke was mainly transported overnight, it appears that the processing can take place in the dark. These results show that a significant fraction of the BBOA loses its characteristic AMS signature and is transformed to OOA in less than a day. This implies that biomass burning can contribute almost half of the organic aerosol mass in the area during summertime.

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Mass Extinction Efficiency Approximation for Polydispersed Aerosol Using Harmonic Mean-Type Approximation

Applied Sciences ◽

10.3390/app10238637 ◽

2020 ◽

Vol 10 (23) ◽

pp. 8637

Author(s):

Junshik Um ◽

Seonghyeon Jang ◽

Young Jun Yoon ◽

Seoung Soo Lee ◽

Ji Yi Lee ◽

...

Keyword(s):

Optical Properties ◽

Chemical Composition ◽

Extinction Coefficient ◽

Mass Extinction ◽

Aerosol Particles ◽

Size Distributions ◽

Extinction Efficiency ◽

Type Approximation ◽

Aerosol Mass ◽

Mass Extinction Efficiency

Among many parameters characterizing atmospheric aerosols, aerosol mass extinction efficiency (MEE) is important for understanding the optical properties of aerosols. MEE is expressed as a function of the refractive indices (i.e., composition) and size distributions of aerosol particles. Aerosol MEE is often considered as a size-independent constant that depends only on the chemical composition of aerosol particles. The famous Malm’s reconstruction equation and subsequent revised methods express the extinction coefficient as a function of aerosol mass concentration and MEE. However, the used constant MEE does not take into account the effect of the size distribution of polydispersed chemical composition. Thus, a simplified expression of size-dependent MEE is required for accurate and conventional calculations of the aerosol extinction coefficient and also other optical properties. In this study, a simple parameterization of MEE of polydispersed aerosol particles was developed. The geometric volume–mean diameters of up to 10 µm with lognormal size distributions and varying geometric standard deviations were used to represent the sizes of various aerosol particles (i.e., ammonium sulfate and nitrate, elemental carbon, and sea salt). Integrating representations of separate small mode and large mode particles using a harmonic mean-type approximation generated the flexible and convenient parameterizations of MEE that can be readily used to process in situ observations and adopted in large-scale numerical models. The calculated MEE and the simple forcing efficiency using the method developed in this study showed high correlations with those calculated using the Mie theory without losing accuracy.

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Formation of secondary organic aerosols from gas–phase emissions of heated cooking oils

10.5194/acp-2017-77 ◽

2017 ◽

Author(s):

Tengyu Liu ◽

Zijun Li ◽

ManNin Chan ◽

Chak K. Chan

Keyword(s):

Gas Phase ◽

Corn Oil ◽

Fine Particulate Matter ◽

Ambient Air ◽

Organic Aerosol ◽

Emission Rates ◽

Scanning Mobility Particle Sizer ◽

Unsaturated Fat ◽

Aerosol Mass ◽

Cooking Oils

Abstract. Cooking emissions can potentially contribute to secondary organic aerosol (SOA) but remain poorly understood. In this study, formation of SOA from gas-phase emissions of five heated vegetable oils (i.e. corn, canola, sunflower, peanut and olive oils) was investigated in a potential aerosol mass (PAM) chamber. Experiments were conducted at 19–20 ºC and 65–70 % RH. The characterization instruments included a scanning mobility particle sizer (SMPS) and a high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS). The efficiency of SOA production, in ascending order, was peanut oil, olive oil, canola oil, corn oil and sunflower oil. The major SOA precursors from heated cooking oils were related to the content of mono-unsaturated fat and omega-6 fatty acids in cooking oils. The average production rate of SOA, after aging at an OH exposure of 1.7 × 1011 molecules cm−3 s, was 1.35 ± 0.30 µg min−1, three orders of magnitude lower compared with emission rates of fine particulate matter (PM2.5) from heated cooking oils in previous studies. The mass spectra of cooking SOA highly resemble field-derived COA (cooking-related organic aerosol) in ambient air, with R2 ranging from 0.74 to 0.88, suggesting that COA might not be entirely primary in origin. The average carbon oxidation state (OSc) of SOA was −1.51–−0.81, falling in the range between ambient hydrocarbon-like organic aerosol (HOA) and semi-volatile oxygenated organic aerosol (SV-OOA), indicating that SOA in these experiments was lightly oxidized.

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Chemical composition, sources, and processes of urban aerosols during summertime in northwest China: insights from high-resolution aerosol mass spectrometry

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-12593-2014 ◽

2014 ◽

Vol 14 (23) ◽

pp. 12593-12611 ◽

Cited By ~ 87

Author(s):

J. Xu ◽

Q. Zhang ◽

M. Chen ◽

X. Ge ◽

J. Ren ◽

...

Keyword(s):

Chemical Composition ◽

High Resolution ◽

Coal Combustion ◽

Northwest China ◽

Temporal Variations ◽

Organic Mass ◽

Scanning Mobility Particle Sizer ◽

Aerosol Mass ◽

Early Afternoon ◽

Particle Sizer

Abstract. An Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was deployed along with a scanning mobility particle sizer (SMPS) and a multi-angle absorption photometer (MAAP) to measure the temporal variations of the mass loading, chemical composition, and size distribution of submicron particulate matter (PM1) in Lanzhou, northwest China, during 11 July–7 August 2012. The average (PM1 mass concentration including non-refractory (PM1 (NR-(PM1) measured by HR-ToF-AMS and black carbon (BC) measured by MAAP during this study was 24.5 μg m−3 (ranging from 0.86 to 105 μg m−3), with a mean composition consisting of 47% organics, 16% sulfate, 12% BC, 11% ammonium, 10% nitrate, and 4% chloride. Organic aerosol (OA) on average consisted of 70% carbon, 21% oxygen, 8% hydrogen, and 1% nitrogen, with the average oxygen-to-carbon ratio (O / C) of 0.33 and organic mass-to-carbon ratio (OM / OC) of 1.58. Positive matrix factorization (PMF) of the high-resolution organic mass spectra identified four distinct factors which represent, respectively, two primary OA (POA) emission sources (traffic and food cooking) and two secondary OA (SOA) types – a fresher, semi-volatile oxygenated OA (SV-OOA) and a more aged, low-volatility oxygenated OA (LV-OOA). Traffic-related hydrocarbon-like OA (HOA) and BC displayed distinct diurnal patterns, both with peak at ~ 07:00–11:00 (BJT: UTC +8), corresponding to the morning rush hours, while cooking-emission related OA (COA) peaked during three meal periods. The diurnal profiles of sulfate and LV-OOA displayed a broad peak between ~ 07:00 and 15:00, while those of nitrate, ammonium, and SV-OOA showed a narrower peak between ~ 08:00–13:00. The later morning and early afternoon maximum in the diurnal profiles of secondary aerosol species was likely caused by downward mixing of pollutants aloft, which were likely produced in the residual layer decoupled from the boundary layer during nighttime. The mass spectrum of SV-OOA was similar to that of coal combustion aerosol and likely influenced by coal combustion activities in Lanzhou during summer. The sources of BC were estimated by a linear decomposition algorithm that uses the time series of the NR-PM1 components. Our results indicate that a main source of BC was local traffic (47%) and that transport of regionally processed air masses also contributed significantly to BC observed in Lanzhou. Finally, the concentration and source of polycyclic aromatic hydrocarbons (PAHs) were evaluated.

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Correlation of black carbon aerosol and carbon monoxide in the high-altitude environment of Mt. Huang in Eastern China

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-9735-2011 ◽

2011 ◽

Vol 11 (18) ◽

pp. 9735-9747 ◽

Cited By ~ 57

Author(s):

X. L. Pan ◽

Y. Kanaya ◽

Z. F. Wang ◽

Y. Liu ◽

P. Pochanart ◽

...

Keyword(s):

Carbon Monoxide ◽

High Altitude ◽

Black Carbon ◽

Mass Concentration ◽

Eastern China ◽

Chemical Compositions ◽

Strong Positive Correlation ◽

Mixing Ratio ◽

Air Masses ◽

The Impact

Abstract. Understanding the relationship between black carbon (BC) and carbon monoxide (CO) will help improve BC emission inventories and the evaluation of global/regional climate forcing effects. In the present work, the BC (PM1) mass concentration and CO mixing ratio were continuously measured at a high-altitude background station on the summit of Mt. Huang (30.16° N, 118.26° E, 1840 m a.s.l.). Annual mean BC mass concentration was 1004.5 ± 895.5 ng m−3 with maxima in spring and autumn, and annual mean CO mixing ratio was 424.1 ± 159.2 ppbv. A large increase of CO was observed in the cold season, implying the contribution from the large-scale domestic coal/biofuel combustion for heating. The BC-CO relationship was found to show different seasonal features but strong positive correlation (R>0.8). In Mt. Huang area, the ΔBC/ΔCO ratio showed unimodal diurnal variations and had a maximum during the day (09:00–17:00 LST) and minimum at night (21:00–04:00 LST) in all seasons, indicating the impact of planetary boundary layer and the intrusion of clean air masses from the high troposphere. Back trajectory cluster analysis showed that the ΔBC/ΔCO ratio of plumes from the Eastern China (Jiangsu, Zhejiang provinces and Shanghai) was 8.8 ± 0.9 ng m−3 ppbv−1. Transportation and industry were deemed as controlling factors of the BC-CO relationship in this region. The ΔBC/ΔCO ratios for air masses from Northern China (Anhui, Henan, Shanxi and Shandong provinces) and southern China (Jiangxi, Fujian and Hunan provinces) were quite similar with mean values of 6.5 ± 0.4 and 6.5 ± 0.2 ng m−3 ppbv−1 respectively. The case studies combined with satellite observations demonstrated that the ΔBC/ΔCO ratio for biomass burning (BB) plumes were 10.3 ± 0.3 and 11.6 ± 0.5ng m−3 ppbv−1, significantly higher than those during non-BB impacted periods. The loss of BC during transport was also investigated on the basis of the ΔBC/ΔCO-RH (relative humidity) relationship along air mass pathways. The results showed that BC particles from Eastern China area was much more easily removed from atmosphere than other inland regions due to the higher RH along transport pathway, implying the importance of chemical compositions and mixing states on BC residence time in the atmosphere.

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Formation of secondary organic aerosols from gas-phase emissions of heated cooking oils

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-7333-2017 ◽

2017 ◽

Vol 17 (12) ◽

pp. 7333-7344 ◽

Cited By ~ 25

Author(s):

Tengyu Liu ◽

Zijun Li ◽

ManNin Chan ◽

Chak K. Chan

Keyword(s):

Gas Phase ◽

Corn Oil ◽

Fine Particulate Matter ◽

Ambient Air ◽

Organic Aerosol ◽

Emission Rates ◽

Monounsaturated Fat ◽

Scanning Mobility Particle Sizer ◽

Aerosol Mass ◽

Cooking Oils

Abstract. Cooking emissions can potentially contribute to secondary organic aerosol (SOA) but remain poorly understood. In this study, formation of SOA from gas-phase emissions of five heated vegetable oils (i.e., corn, canola, sunflower, peanut and olive oils) was investigated in a potential aerosol mass (PAM) chamber. Experiments were conducted at 19–20 °C and 65–70 % relative humidity (RH). The characterization instruments included a scanning mobility particle sizer (SMPS) and a high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS). The efficiency of SOA production, in ascending order, was peanut oil, olive oil, canola oil, corn oil and sunflower oil. The major SOA precursors from heated cooking oils were related to the content of monounsaturated fat and omega-6 fatty acids in cooking oils. The average production rate of SOA, after aging at an OH exposure of 1. 7 × 1011 molecules cm−3 s, was 1. 35 ± 0. 30 µg min−1, 3 orders of magnitude lower compared with emission rates of fine particulate matter (PM2. 5) from heated cooking oils in previous studies. The mass spectra of cooking SOA highly resemble field-derived COA (cooking-related organic aerosol) in ambient air, with R2 ranging from 0.74 to 0.88. The average carbon oxidation state (OSc) of SOA was −1.51 to −0.81, falling in the range between ambient hydrocarbon-like organic aerosol (HOA) and semi-volatile oxygenated organic aerosol (SV-OOA), indicating that SOA in these experiments was lightly oxidized.

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Chemical characteristics of submicron particles at the central Tibetan Plateau: insights from aerosol mass spectrometry

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-427-2018 ◽

2018 ◽

Vol 18 (1) ◽

pp. 427-443 ◽

Cited By ~ 19

Author(s):

Jianzhong Xu ◽

Qi Zhang ◽

Jinsen Shi ◽

Xinlei Ge ◽

Conghui Xie ◽

...

Keyword(s):

Chemical Composition ◽

High Resolution ◽

Tibetan Plateau ◽

Mass Transport ◽

Mass Concentration ◽

Organic Aerosol ◽

Early Morning ◽

Monsoon Period ◽

Air Mass ◽

Aerosol Mass

Abstract. Recent studies have revealed a significant influx of anthropogenic aerosol from South Asia to the Himalayas and Tibetan Plateau (TP) during pre-monsoon period. In order to characterize the chemical composition, sources, and transport processes of aerosol in this area, we carried out a field study during June 2015 by deploying a suite of online instruments including an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-AMS) and a multi-angle absorption photometer (MAAP) at Nam Co station (90∘57′ E, 30∘46′ N; 4730 m a.s.l.) at the central of the TP. The measurements were made at a period when the transition from pre-monsoon to monsoon occurred. The average ambient mass concentration of submicron particulate matter (PM1) over the whole campaign was ∼ 2.0 µg m−3, with organics accounting for 68 %, followed by sulfate (15 %), black carbon (8 %), ammonium (7 %), and nitrate (2 %). Relatively higher aerosol mass concentration episodes were observed during the pre-monsoon period, whereas persistently low aerosol concentrations were observed during the monsoon period. However, the chemical composition of aerosol during the higher aerosol concentration episodes in the pre-monsoon season was on a case-by-case basis, depending on the prevailing meteorological conditions and air mass transport routes. Most of the chemical species exhibited significant diurnal variations with higher values occurring during afternoon and lower values during early morning, whereas nitrate peaked during early morning in association with higher relative humidity and lower air temperature. Organic aerosol (OA), with an oxygen-to-carbon ratio (O ∕ C) of 0.94, was more oxidized during the pre-monsoon period than during monsoon (average O ∕ C ratio of 0.72), and an average O ∕ C was 0.88 over the entire campaign period, suggesting overall highly oxygenated aerosol in the central TP. Positive matrix factorization of the high-resolution mass spectra of OA identified two oxygenated organic aerosol (OOA) factors: a less oxidized OOA (LO-OOA) and a more oxidized OOA (MO-OOA). The MO-OOA dominated during the pre-monsoon period, whereas LO-OOA dominated during monsoon. The sensitivity of air mass transport during pre-monsoon with synoptic process was also evaluated with a 3-D chemical transport model.

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Aerosol effective density measurement using scanning mobility particle sizer and quartz crystal microbalance with the estimation of involved uncertainty

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-8-12887-2015 ◽

2015 ◽

Vol 8 (12) ◽

pp. 12887-12931

Author(s):

B. Sarangi ◽

S. G. Aggarwal ◽

D. Sinha ◽

P. K. Gupta

Keyword(s):

Quartz Crystal Microbalance ◽

Mass Concentration ◽

Quartz Crystal ◽

Aerosol Particles ◽

Particle Mass ◽

Effective Density ◽

Substantial Contribution ◽

New Delhi ◽

Scanning Mobility Particle Sizer ◽

Particle Sizer

Abstract. In this work, we have used scanning mobility particle sizer (SMPS) and quartz crystal microbalance (QCM) to estimate the effective density of aerosol particles. This approach is tested for aerosolized particles generated from the solution of standard materials of known density, i.e. ammonium sulfate (AS), ammonium nitrate (AN) and sodium chloride (SC), and also applied for ambient measurement in New Delhi. We also discuss uncertainty involved in the measurement. In this method, dried particles are introduced in to a differential mobility analyzer (DMA), where size segregation was done based on particle electrical mobility. At the downstream of DMA, the aerosol stream is subdivided into two parts. One is sent to a condensation particle counter (CPC) to measure particle number concentration, whereas other one is sent to QCM to measure the particle mass concentration simultaneously. Based on particle volume derived from size distribution data of SMPS and mass concentration data obtained from QCM, the mean effective density (ρeff) with uncertainty of inorganic salt particles (for particle count mean diameter (CMD) over a size range 10 to 478 nm), i.e. AS, SC and AN is estimated to be 1.76 ± 0.24, 2.08 ± 0.19 and 1.69 ± 0.28 g cm−3, which are comparable with the material density (ρ) values, 1.77, 2.17 and 1.72 g cm−3, respectively. Among individual uncertainty components, repeatability of particle mass obtained by QCM, QCM crystal frequency, CPC counting efficiency, and equivalence of CPC and QCM derived volume are the major contributors to the expanded uncertainty (at k = 2) in comparison to other components, e.g. diffusion correction, charge correction, etc. Effective density for ambient particles at the beginning of winter period in New Delhi is measured to be 1.28 ± 0.12 g cm−3. It was found that in general, mid-day effective density of ambient aerosols increases with increase in CMD of particle size measurement but particle photochemistry is an important factor to govern this trend. It is further observed that the CMD has good correlation with O3, SO2 and ambient RH, suggesting that possibly sulfate secondary materials have substantial contribution in particle effective density. This approach can be useful for real-time measurement of effective density of both laboratory generated and ambient aerosol particles, which is very important for studying the physico-chemical property of particles.

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