Significant Source Of Particles Research Articles

Measurement report: Insights into the chemical composition and origin of molecular clusters and potential precursor molecules present in the free troposphere over the southern Indian Ocean: observations from the Maïdo Observatory (2150 m a.s.l., Réunion)

Abstract. New particle formation (NPF) in the free troposphere (FT) is thought to be a significant source of particles over the oceans. The entrainment of particles initially formed in the marine FT is further suspected to be a major contributor to cloud condensation nuclei (CCN) number concentrations in the marine boundary layer (BL). Yet, little is known about the process and, more broadly, about the composition of the marine FT, which remains poorly explored due to access difficulties. Here we report measurements performed in April 2018 at the Maïdo Observatory with a nitrate-based chemical ionization atmospheric pressure interface time-of-flight mass spectrometer, which have allowed the first molecular-level characterization of the remote marine FT composition. A number of molecules and clusters were identified and classified into nine groups according to their chemical composition; among the identified species, the groups containing methanesulfonic acid (MSA) and C2 amines show signals that are on average significantly higher when the site is under conditions representative of the marine FT (compared to the BL). The correlation analysis revealed apparent connections between the signals of the identified compounds and several variables concurrently measured at the site (under FT conditions) or related to air mass history, suggesting that oxalic acid, malonic acid, and observed C2 amines could be of terrestrial origin, with, in addition, a possible marine source for oxalic acid and amines, while iodic acid, sulfur species, and maleic acid have a dominant marine origin. Identification of FT conditions at the site was based on the analysis of the standard deviation of the wind direction; this parameter, which can easily be derived from continuous measurements at the site, is shown in the first part of the study to be a relevant tracer when compared to predictions from the Meso-NH atmospheric model. Similar to other high-altitude sites, FT conditions are mainly encountered at night at Maïdo; therefore, the link to NPF could not be established, and further research is needed to assess the composition of precursors to nanoparticle formation in the marine FT.

New particle formation leads to enhanced cloud condensation nuclei concentrations on the Antarctic Peninsula

Abstract. Few studies have investigated the impact of new particle formation (NPF) on cloud condensation nuclei (CCN) in remote Antarctica, and none has elucidated the relationship between NPF and CCN production. To address that knowledge gap, we continuously measured the number size distribution of 2.5–300 nm particles and CCN number concentrations at King Sejong Station on the Antarctic Peninsula from 1 January to 31 December 2018. Ninety-seven NPF events were detected throughout the year. Clear annual and seasonal patterns of NPF were observed: high concentration and frequency of nucleation-mode particles in summer (December–February: 53 NPF cases) and undetected nucleation-mode particles in winter (June–August: no NPF cases). We estimated the spatial scale of NPF by multiplying the time during which a distinct nucleation mode can be observed at the sampling site by the locally measured wind speed. The estimated median spatial scale of NPF around the Antarctic Peninsula was found to be approximately 155 km, indicating the large scale of NPF events. Air back-trajectory analysis revealed that 80 cases of NPF events were associated with air masses originating over the ocean, followed by sea-ice (12 cases), multiple (3 cases), and land (2 cases) regions. We present and discuss three major NPF categories: (1) marine NPF, (2) sea-ice NPF, and (3) multiple NPF. Satellite estimates for sea-surface dimethylsulfoniopropionate (DMSP; a precursor of gaseous dimethyl sulfide) data showed that the production of oceanic biogenic precursors could be a key component in marine NPF events, whereas halogen compounds released from ice-covered areas could contribute to sea-ice NPF events. Terrestrial sources (wildlife colonies, vegetation, and meltwater ponds) from Antarctica could affect aerosol production in multiple air masses. Out of 97 observed NPF events, 83 cases were characterized by the simultaneous increase in the CCN concentration by 2 %–270 % (median 44 %) in the following 1 to 36 h (median 8 h) after NPF events. Overall, Antarctic NPF events were found to be a significant source of particles with different physical characteristics and related to biogenic sources in and around the Antarctic Peninsula, which subsequently grew to cloud condensation nuclei.

Investigating toothbrushing behavior and its aerosol emissions from using electric toothbrushes

Respiratory infectious diseases (RIDs) are generally spread through person-to-person contact. The human oral cavity, in particular, is a significant source of particles that can cause RIDs. Electric toothbrushes, popular for oral cleaning in recent years, work via high-frequency vibration, which can theoretically spread droplets or small-size aerosols containing viruses. However, the particle emission rates and the potential to spread RIDs using electric toothbrushes are still unclear. In this paper, we investigated the particle emissions from using electric toothbrushes by designing a three-step approach, i.e., a preference survey on toothpaste and toothbrush selections, a behavior test on toothpaste usage, and a standardized particle emission test. The results showed that, first, the toothpaste would be rapidly decomposed into foams, and the emission rates quickly increased to a peak within approximately 10s. Then, the particle emissions decreased slightly and entered a steady phase until the 2-min brushing period stopped. Second, more than half of the detected particles were PM1, and almost all were PM5, which can be considered aerosols, and the emissions can reach up to 5433 counts/s. Third, the emissions heavily depended on toothbrush and toothpaste selections, the brushing post, i.e., the teeth. This study suggests that using electric toothbrushes can pose risks of spreading RIDs in enclosed indoor environments such as private homes or, more significantly, public washrooms in school dormitories, airports, train stations, etc. Limited usage of electric toothbrushes and better designs of public washrooms in the context of a global pandemic may be advised.

The effect of the shoeless course on particle concentrations and dust composition in schools

Airborne particles may effect on indoor air quality in schools. One significant particle source is outdoor dust and soil transported indoors on people's shoes, which may be resuspended, and further inhaled by pupils and teachers. In many Finnish schools, shoes are taken off by coat racks near the classrooms (shoe schools). The new course of action is to take shoes off right when entering the building (sock schools). In this study, particle mass and number concentrations, together with chemical composition of the dust were investigated in sock and shoe schools. According to results, PM10 and PM15 concentrations in corridors were significantly higher in shoe schools compared to sock schools (p < 0.05). The shoeless course did not affect on the particle number concentrations, but the increases in the number concentrations originated from diners. The elemental concentrations (Li, Al, Si, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Ba, Pb) in settled dust were also higher in shoe schools compared to sock schools, and the Zn concentrations differed significantly (p < 0.05). In conclusion, this study showed that by taking the shoes off when entering the school building you can enhance the indoor air quality by reducing the particle mass concentrations.

Analysis of levoglucosan and its isomers in atmospheric samples by ion chromatography with electrospray lithium cationisation - Triple quadrupole tandem mass spectrometry

Biomass burning (BB) emissions are a significant source of particles to the atmosphere, especially in the Southern Hemisphere, where the occurrence of anthropogenic and natural wild fires is common. These emissions can threaten human health through increased exposure, whilst simultaneously representing a significant source of trace metals and nutrients to the ocean. One well known method to track BB emissions is through monitoring the atmospheric concentration of specific monosaccharide anhydrides (MAs), specifically levoglucosan and its isomers, mannosan and galactosan. Herein, a new method for the determination of levoglucosan and its isomers in marine and terrestrial aerosol samples is presented, which delivers both high selectivity and sensitivity, through the coupling of ion chromatography and triple quadrupole tandem mass spectrometry. Optimal chromatographic conditions, providing baseline separation for target anhydrosugars in under 8 min, were obtained using a Dionex CarboPacⓇ PA-1 column with an electrolytically generated KOH gradient. To improve the ionisation efficiency for MS detection, an organic make-up solvent was fed into the IC column effluent before the ESI source, and to further increase both sensitivity and selectivity, cationisation of levoglucosan was investigated by adding salts into the make-up solvent, namely, sodium, ammonium and lithium salts. Using positive lithium cationisation with 0.5 mM lithium chloride in methanol as the make-up solvent, delivered at a flow rate of 0.02 mL min–1, the levoglucosan response was improved by factors of 100 and 10, comparing to negative ionisation and positive sodium cationisation, respectively. Detection was carried out in SRM mode for quantitation and identification, achieving an instrumental LOD of 0.10, 0.12 and 0.5 µg L−1 for levoglucosan, mannosan and galactosan, respectively. Finally, the method was applied to the analysis of 41 marine and terrestrial aerosol samples from Australia, its surrounding coastal waters and areas within the remote Southern Ocean, covering a large range of BB marker concentrations.

Nocturnal new particle formation events in urban environments

Abstract. Few studies have investigated nocturnal new particle formation (NPF) events, and none of them were conducted in urban environments. Nocturnal NPF can potentially be a significant source of particles in urban areas, and studying them would improve our understanding of nucleation mechanisms. To address this, our study was conducted in an urban environment to investigate the physical characteristics of NPF events, with a particular focus on nocturnal events and the differences between them and the daytime NPF events. Particle number size distribution (PNSD) was measured for 2 weeks at each of 25 sites across an urban environment. A new method was proposed to automatically categorise NPF events based on growth rate (GR) in order to remove the bias related to the manual procedure. Out of 219 observed events, 118 and 101 were categorised into class I and II respectively and 73 happened during the nighttime which included more than 30 % of the events. GR and condensation sink (CS) were calculated and a slight negative relationship between GR and CS was observed. Nocturnal events displayed higher GRs compared to daylight ones which were on average about 10 %. Back trajectory analysis was also conducted to estimate the locations of the sources of daylight and nocturnal precursors. While the precursors related to daylight events originated from different locations with no particular pattern, back-trajectory analysis showed many air masses associated with nocturnal NPF events were transported from over the ocean. Overall, nocturnal NPF events were found to be a significant source of particles in the studied environment with different physical characteristics and/or sources compared to daylight events.

Infiltration of Black Carbon Particles from Residential Woodsmoke into Nearby Homes

In many communities, residential wood burning is the source of a significant fraction of wintertime PM2.5 and produces exposures to nearby residents inside their homes. To evaluate the magnitude of this effect, black carbon particles were measured as a proxy for woodsmoke indoors and outdoors in a community where residential woodsmoke is the only significant particle source. Thirteen indoor/outdoor measurement pairs were obtained at 4 different residences and showed an average indoor/outdoor concentration ratio of 0.78 ± 0.21 for residences without indoor generation. In addition, a time dependent mass balance model was used in conjunction with aethalometer measurements taken over 16 nights at a single residence to estimate an average air exchange rate of 0.26 ± 0.08 h-1, an average deposition loss rate of 0.08 ± 0.03 h-1, and an average penetration factor of 0.97 ± 0.02. Using a mechanistic approach which utilizes these average values in a steady state model, the predicted average infiltration factor was 0.74 for the residence studied. The high values for both measured I/O ratio and modeled infiltration factor show that residential environments provide inhabitants with relatively little protection from recently generated wood smoke particles.

Flow and deposition in and around a finite patch of vegetation

This laboratory study describes the flow and deposition observed in and around a finite patch of vegetation located at the wall of a channel. Two patch densities are considered with 2% and 10% solid volume fraction. The velocity field, measured in and around the patch by acoustic Doppler velocimetry, revealed three distinct zones. First, there is a diverging flow region at the leading edge of the patch, where the flow in line with the patch decelerates, and the bulk of the flow is diverted toward the open channel. Second, there is a fully developed region within the vegetation, where the velocity is uniform across the patch width and along the length of the patch. Third, a shear layer forms at the interface between the patch and adjacent open channel. The pattern of deposition in and around the vegetation was characterized by releasing 12-micron spherical, glass particles and recording net deposition on a set of glass slides. In the diverging region, net deposition increases in the stream-wise direction, as the local velocity decreases. In the fully developed region of the patch, deposition decreases with longitudinal position, as the concentration in the water column is depleted. The deposition pattern is nearly uniform across the patch width, consistent with the velocity field and suggesting that turbulent diffusive flux across the lateral edge of the patch is not a significant source of particles to the patch under the conditions studied here.

Measurement of particulate concentrations produced during bulk material handling at the Tarragona harbor

Bulk material handling can be a significant source of particles in harbor areas. The atmospheric impact of a number of loading/unloading activities of diverse raw materials has been assessed from continuous measurements of ambient particle concentrations recorded close to the emission sources. Two experimental campaigns have been carried out in the Tarragona port to document the impact of specific handling operations and bulk materials. Dusty bulk materials such as silica–manganese powder, tapioca, coal, clinker and lucerne were dealt with during the experiments. The highest impacts on ambient particle concentrations were recorded during handling of clinker. For this material and silica–manganese powder, high concentrations were recorded in the fine grain size (<2.5 μm). The lowest impacts on particulate matter concentrations were recorded during handling of tapioca and lucerne, mainly in the coarse grain size (2–5–10 μm). The effectiveness of several emission abatement measures, such as ground watering to diminish coal particle resuspension, was demonstrated to reduce ambient concentrations by up to two orders of magnitude. The importance of other good practices in specific handling operations, such as controlling the height of the shovel discharge, was also evidenced by these experiments. The results obtained can be further utilized as a useful experimental database for emission factor estimations.

Characteristics of Atmospheric Metals during Dry Monsoon Season in the Coastal Region of Western Taiwan

his study investigated the characteristics (elemental concentrations, size distributions, and dry deposition flux) of aerosol particles in the coastal region of western Taiwan during the dry monsoon (fall and winter) season. Factor analysis results show that resuspended soil dust is a significant source of particles. However, factor analysis is unable to define specific emission sources of noncrustal metals, probably because these metals are mixed by long-distance transportation, regardless of their sources. On average, coarse mode particles (with aerodynamic diameters of larger than 1.0 μm) contribute 66% of the total particle mass. These coarse particles represent 53%, 64%, 62%, and 44% of the mass of elements Al, Ca, Fe, and Ti, respectively. Coarse particles predominate dry deposition fluxes because the average percentages of dry deposition fluxes attributed to fine particles are only 0.2%, 0.2%, 0.18%, 0.22% and 0.19% of the total particle mass, the Al mass, the Ca mass, the Pb mass and the Ni mass, respectively. Both atmospheric concentrations and dry deposition fluxes of Al, Ca, Fe, Mn and Sr are strongly influenced by crustal sources. For Pb, Zn, Ni, Ba, Cu and Cr, the parent aerosol is soil-oriented but the dry deposition is not. Neither the parent aerosol nor the dry deposition of V and Cd is influenced by crustal sources. Enrichment factors of most metal crust elements are considerably lower in dry deposition than in the parent aerosol. Fractionation factor analysis results show that the crustal component of a metal element in a parent aerosol is fractionated from the atmosphere by a dry deposition sequence. Although the noncrustal sources are not important in dry deposition, noncrustal elements can be easily fractionated between particles and dry deposits. Among the elements investigated, Pb had the highest fractionation factor of 12.1.

A one‐dimensional sectional model to simulate multicomponent aerosol dynamics in the marine boundary layer: 2. Model application

The dynamics of aerosols in the marine boundary layer (MBL) are simulated with the marine boundary layer aerosol model (MARBLES), a one‐dimensional, multicomponent sectional aerosol model [Fitzgerald et al., this issue; Gelbard et al., this issue]. First, to illustrate how the various aerosol processes influence the particle size distribution, the model was run with one or two processes operating on the same initial size distribution. Because of current interest in the effects of cloud processing of aerosols and exchange of aerosols with the free troposphere (FT) on marine aerosol size distributions, these two processes are examined in considerable detail. The simulations show that the effect of cloud processing (characteristic double‐peaked size distribution) in the upper part of the MBL is manifested at the surface on a timescale that is much faster than changes due to exchange with the FT, assuming a typical exchange velocity of 0.6 cm s−1. The model predicts that the FT can be a significant source of particles for the MBL in the size range of the cloud‐processing minimum, between the unactivated interstitial particles and the cloud condensation nuclei (CCN) which have grown as a result of conversion of dissolved SO2 to sulfate in cloud droplets. The model was also used to simulate the evolution of the aerosol size distribution in an air mass advecting from the east coast of the United States out over the ocean for up to 10 days. The modification of a continental aerosol size distribution to one that is remote marine in character occurs on a timescale of 6–8 days. Nucleation was not observed in the base case 10‐day advection simulation which assumed rather typical meteorological conditions. However, significant nucleation was predicted under a more favorable (albeit, atypical) combination of conditions which included significant precipitation scavenging (5 mm h−1 of rain for 12 hours), colder temperatures by 10°C (283 K at the surface decreasing to 278 K at 1000 m) and a high DMS flux (40 μmol m−2 d−1). In a test of model self initialization, long‐term (8–10 days) predictions of marine aerosol size distributions were found to be essentially independent of initial conditions.

Edge measurements during ICRF heating on the PLT Tokamak

Edge measurements have been conducted on the PLT Tokamak under a variety of operating conditions in order to ascertain the relevant processes at work in coupling r.f. power to plasmas. The edge density is found to increase significantly with the application of ICRF, and electron heating occurs in the vicinity of the Faraday shield surrounding with antenna. Spectroscopic measurements indicate that the energized antenna is significant particle source. The relative increase of metallic impurities was found to be approximately 2.7 times larger than the corresponding increase in deuterium. In addition, the relative increase of deuterium and impurities was approximately 3-4 times greater at the energized antenna than at other locations around the torus. Model calculations show that for deuterium released from the Faraday shield, the Dalpha emission is localized radially to a region within 4 cm of the antenna. A correlation was found between the edge density and the Dalpha intensity that justifies its use as a measure of the particle source rate.

Energetic (&gt;60 eV) atmospheric photoelectrons

Data from the low altitude plasma instrument (LAPI) on Dynamics Explorer 2 document a population of high‐energy (up to 800 eV) atmospheric photoelectrons that has not been reported in the published literature. The source of these photoelectrons is postulated to be the soft X ray portion of the whole Sun spectrum. This conclusion is supported by (1) sunrise‐sunset characteristics that track those of the classical (&lt;60 eV) EUV‐produced photoelectrons and (2) theoretical results from two models that incorporate the soft X ray portion of the solar spectrum. The models include K shell ionization effects and predict peaks in the photoelectron spectrum due to Auger electrons emitted from oxygen and nitrogen. The peak for nitrogen is observed as predicted, but the peak for oxygen is barely observable. Excellent quantitative agreement is achieved between theory and experiment by using reasonable adjustments to the few published soft X ray spectra based on solar activity. The upflowing energetic photoelectrons provide a heretofore unknown source of electrons to the magnetosphere. They occur whenever and wherever the Sun is up, that is, at all invariant latitudes. Their density is low, but they are steady and ubiquitous. If scattering and trapping occur on closed field lines, then these photoelectrons could contribute as a significant particle source and thus represent a new facet of magnetosphere‐ionosphere coupling.

Electron energization in the geomagnetic tail current sheet

Electron motion in the distant tail current sheet is evaluated and found to violate the guiding center approximation at energies ≳ 100 eV. Most electrons within the energy range ˜10−1 ‐ 10² keV that enter the current sheet become trapped within the magnetic field reversal region. These electrons then convect earthward and gain energy from the cross‐tail electric field. If the energy spectrum of electrons entering the current sheet is similar to that of electrons from the boundary layer surrounding the magneto tail, the energy gain from the electric field produces electron energy spectra comparable to those observed in the earth's plasma sheet. Thus current sheet interactions can be a significant source of particles and energy for plasma sheet electrons as well as for plasma sheet ions. A small fraction of electrons within the current sheet has its pitch angles scattered so as to be ejected from the current sheet within the atmospheric loss cone. These electrons can account for the electron precipitation near the high‐latitude boundary of energetic electrons, which is approximately isotropic in pitch angle up to at least several hundred keV. Current sheet interaction should cause approximately isotropic auroral precipitation up to several hundred keV energies, which extends to significantly lower latitudes for ions than for electrons in agreement with low‐altitude satellite observations. Electron precipitation associated with diffuse aurora generally has a transition at 1–10 keV to anisotropic pitch angle distributions. Such electron precipitation cannot be explained by current sheet interactions, but it can be explained by pitch angle diffusion driven by plasma turbulence.