WITHDRAWN: Source apportionment of fine PM by combining high time resolution organic and inorganic chemical composition datasets

Abstract. Chemical composition and hygroscopicity closure of marine aerosol in high time resolution has not been achieved yet due to the difficulty involved in measuring the refractory sea-salt concentration in near-real time. In this study, attempts were made to achieve closure for marine aerosol based on a humidified tandem differential mobility analyser (HTDMA) and a high-resolution time-of-flight aerosol mass spectrometer (AMS) for wintertime aerosol at Mace Head, Ireland. The aerosol hygroscopicity was examined as a growth factor (GF) at 90 % relative humidity (RH). The corresponding GFs of 35, 50, 75, 110 and 165 nm particles were 1.54±0.26, 1.60±0.29, 1.66±0.31, 1.72±0.29 and 1.78±0.30 (mean ± standard deviation), respectively. Two contrasting air masses (continental and marine) were selected to study the temporal variation in hygroscopicity; the results demonstrated a clear diurnal pattern in continental air masses, whereas no diurnal pattern was found in marine air masses. In addition, wintertime aerosol was observed to be largely externally mixed in both of the contrasting air masses. Concurrent high time resolution PM1 (particulate matter <1 µm) chemical composition data from combined AMS and MAAP measurements, comprising organic matter, non-sea-salt sulfate, nitrate, ammonium, sea salt and black carbon (BC), were used to predict aerosol hygroscopicity with the Zdanovskii–Stokes–Robinson (ZSR) mixing rule. Overall, good agreement (an R2 value of 0.824 and a slope of 1.02) was found between the growth factor of 165 nm particles measured by the HTDMA (GF_HTDMA) and the growth factor derived from the AMS + MAAP bulk chemical composition (GF_AMS). Over 95 % of the estimated GF values exhibited less than a 10 % deviation for the whole dataset, and this deviation was mostly attributed to the neglected mixing state as a result of the bulk PM1 composition.

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High time-resolution and time-integrated measurements of particulate metals and elements in an environmental justice community within the Los Angeles Basin: Spatio-temporal trends and source apportionment

Atmospheric Environment X ◽

10.1016/j.aeaoa.2020.100089 ◽

2020 ◽

Vol 7 ◽

pp. 100089

Author(s):

Sina Hasheminassab ◽

Mohammad H. Sowlat ◽

Payam Pakbin ◽

Aaron Katzenstein ◽

Jason Low ◽

...

Keyword(s):

Los Angeles ◽

Environmental Justice ◽

Source Apportionment ◽

Time Resolution ◽

Temporal Trends ◽

High Time ◽

High Time Resolution ◽

Los Angeles Basin ◽

Particulate Metals ◽

Spatio Temporal

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Calibration and evaluation of broad supersaturation scanning (BS2) cloud condensation nuclei counter for rapid measurement of particle hygroscopicity and CCN activity

10.5194/amt-2021-189 ◽

2021 ◽

Author(s):

Najin Kim ◽

Yafang Cheng ◽

Nan Ma ◽

Mira L. Pöhlker ◽

Thomas Klimach ◽

...

Keyword(s):

Particle Size ◽

Chemical Composition ◽

Time Resolution ◽

Calibration Curve ◽

Cloud Condensation Nuclei ◽

Aerosol Particles ◽

High Time ◽

Activity Measurement ◽

High Time Resolution ◽

Ccn Activity

Abstract. For understanding and assessing aerosol-cloud interactions and their impact on climate, reliable measurement data of aerosol particle hygroscopicity and cloud condensation nuclei (CCN) activity are required. The CCN activity of aerosol particles can be determined by scanning particle size and supersaturation (S) in CCN measurements. Compared to the existing differential mobility analyzer (DMA)-CCN activity measurement, a broad supersaturation scanning CCN (BS2-CCN) system, in which particles are exposed to a range of S simultaneously, can measure the CCN activity with a high time-resolution. Based on a monotonic relation between the activation supersaturation of aerosol particles (Saerosol) and the activated fraction (Fact) of the BS2-CCN measurement, we can derive κ, a single hygroscopicity parameter, directly. Here, we describe how the BS2-CCN system can be effectively calibrated and which factors can affect the calibration curve (Fact – Saerosol). For calibration, size-resolved CCN measurements with ammonium sulfate and sodium chloride particles are performed under the three different thermal gradient (dT) conditions (dT = 6, 8, and 10 K). We point out key processes that can affect the calibration curve and thereby need to be considered as follows: First, the shape of the calibration curve is primarily influenced by Smax, the maximum S in the activation tube. We need to determine appropriate Smax depending on particle size and κ to be investigated. To minimize the effect of multiply charged particles, small geometric mean diameter (𝐷𝑔) and 𝜎𝑔 geometric standard deviation (𝜎𝑔) in number size distribution are recommended when generating the calibration aerosols. Last, Fact is affected by particle number concentration and has a decreasing rate of 0.02/100 cm−3 due to the water consumption in the activation tube. For evaluating the BS2-CCN system, inter-comparison experiments between typical DMA-CCN and BS2-CCN measurement were performed with the laboratory-generated aerosol mixture and ambient aerosols. Good agreements of κ values between DMA-CCN and BS2-CCN measurements for both experiments show that the BS2-CCN system can measure CCN activity well compared to the existing measurement, and can measure a broad range of hygroscopicity distribution with a high time-resolution (~1 second vs. few minutes for a standard CCN activity measurement). As the hygroscopicity can be used as a proxy for the chemical composition, our method can also serve as a complementary approach for fast and size-resolved detection/estimation of aerosol chemical composition.

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