To quantify the contributions of fossil and biomass sources to the wintertime Arctic aerosol burden source apportionment is reported for elemental (EC) and organic carbon (OC) fractions of six PM10 ...samples collected during a wintertime (2012–2013) campaign in Barrow, AK. Radiocarbon apportionment of EC indicates that fossil sources contribute an average of 68 ± 9% (0.01–0.07 μg m–3) in midwinter decreasing to 49 ± 6% (0.02 μg m–3) in late winter. The mean contribution of fossil sources to OC for the campaign was stable at 38 ± 8% (0.04–0.32 μg m–3). Samples were also analyzed for organic tracers, including levoglucosan, for use in a chemical mass balance (CMB) source apportionment model. The CMB model was able to apportion 24–53% and 99% of the OC and EC burdens, respectively, during the campaign, with fossil OC contributions ranging from 25 to 74% (0.02–0.09 μg m–3) and fossil EC contributions ranging from 73 to 94% (0.03–0.07 μg m–3). Back trajectories identified two major wintertime source regions to Barrow: the Russian and North American Arctic. Atmospheric lifetimes of levoglucosan, ranging from 50 to 320 h, revealed variability in wintertime atmospheric processing of this biomass burning tracer. This study allows for unambiguous apportionment of EC to fossil fuel and biomass combustion sources and intercomparison with CMB modeling.
Long‐term measurements of the light absorption coefficient (babs) obtained with a particle soot absorption photometer (PSAP), babs (PSAP), have been previously reported for Barrow, Alaska, and ...Ny‐Ålesund, Spitsbergen, in the Arctic. However, the effects on babs of other aerosol chemical species coexisting with black carbon (BC) have not been critically evaluated. Furthermore, different mass absorption cross section (MAC) values have been used to convert babs to BC mass concentration (MBC = babs/MAC). We used a continuous soot monitoring system (COSMOS), which uses a heated inlet to remove volatile aerosol compounds, to measure babs (babs (COSMOS)) at these sites during 2012–2015. Field measurements and laboratory experiments have suggested that babs (COSMOS) is affected by about 9% on average by sea‐salt aerosols. MBC values derived by COSMOS (MBC (COSMOS)) using a MAC value obtained by our previous studies agreed to within 9% with elemental carbon concentrations at Barrow measured over 11 months. babs (PSAP) was higher than babs (COSMOS), by 22% at Barrow (PM1) and by 43% at Ny‐Ålesund (PM10), presumably due to the contribution of volatile aerosol species to babs (PSAP). Using babs (COSMOS) as a reference, we derived MBC (PSAP) from babs (PSAP) measured since 1998. We also established the seasonal variations of MBC at these sites. Seasonally averaged MBC (PSAP) decreased at a rate of about 0.55 ± 0.30 ng m−3 yr−1. We also compared MBC (COSMOS) and scaled MBC (PSAP) values with previously reported data and evaluated the degree of inconsistency in the previous data.
Key Points
We evaluated the accuracy of black carbon (BC) measurements at Barrow, Alaska, and Ny‐Ålesund, Spitsbergen, in the Arctic
At Barrow, seasonally averaged BC mass concentrations decreased in winter and summer at a rate of 0.55 ± 0.30 ng m−3 yr−1 during 1998–2015
We established seasonal variations of BC at the two sites and evaluated the causes of the inconsistency of the previously reported data
Number
concentrations of ice-nucleating particles (NINP) in the Arctic
were derived from ground-based filter samples. Examined samples had been
collected in Alert (Nunavut, northern Canadian ...archipelago on Ellesmere
Island), Utqiaġvik, formerly known as Barrow (Alaska), Ny-Ålesund
(Svalbard), and at the Villum Research Station (VRS; northern Greenland). For
the former two stations, examined filters span a full yearly cycle. For VRS,
10 weekly samples, mostly from different months of one year, were included.
Samples from Ny-Ålesund were collected during the months from March until
September of one year. At all four stations, highest concentrations were
found in the summer months from roughly June to September. For those stations
with sufficient data coverage, an annual cycle can be seen. The spectra of
NINP observed at the highest temperatures, i.e., those obtained
for summer months, showed the presence of INPs that nucleate ice up to
−5 ∘C. Although the nature of these highly ice-active INPs could
not be determined in this study, it often has been described in the
literature that ice activity observed at such high temperatures originates
from the presence of ice-active material of biogenic origin. Spectra observed
at the lowest temperatures, i.e., those derived for winter months, were on
the lower end of the respective values from the literature on Arctic INPs or
INPs from midlatitude continental sites, to which a comparison is presented
herein. An analysis concerning the origin of INPs that were ice active at
high temperatures was carried out using back trajectories and satellite
information. Both terrestrial locations in the Arctic and the adjacent sea
were found to be possible source areas for highly active INPs.
As criteria pollutants from anthropogenic emissions have declined in the US
in the last 2 decades, biomass burning (BB) emissions are becoming more
important for urban air quality. Tracking the ...transported BB emissions and
their impacts is challenging, especially in areas that are also burdened by
anthropogenic sources like the Texas Gulf Coast. During the Corpus Christi
and San Antonio (CCSA) field campaign in spring 2021, two long-range-transport BB events (BB1 and BB2) were identified. The observed patterns of an absorption Ångström exponent (AAE), a high-resolution time-of-flight
aerosol mass spectrometer (HR-ToF-AMS) BB tracer (f60), equivalent
black carbon (eBC), acetonitrile and carbon monoxide (CO) during BB1 and BB2
indicated differences in the mixing of transported BB plumes with local
anthropogenic sources. The combined information from HYSPLIT backward-trajectory (BT) and satellite observations revealed that BB1 had mixed
influence of transported smoke plumes from fires in central Mexico, the
Yucatán Peninsula and the central US, whereas BB2 was influenced by
fires in the central US. The estimated transport times of smoke from the
Mexican fires and the central US fires to our study site were not too
different (48–54 and 24–36 h, respectively), and both events
appeared to have undergone similar levels of atmospheric processing, as
evident in the elemental ratios of bulk organic aerosol (OA). We observed an
aging trend for f44 vs. f60 and f44 vs. f43 as a
function of time during BB2 but not during BB1. Positive matrix
factorization (PMF) analysis of OA showed that BB1 had a mixture of organics
from aged BB emissions with an anthropogenic marine signal, while the oxidized
organic compounds from aged BB emissions dominated the aerosols during BB2.
The size distribution of aerosol composition revealed distinct
characteristics between BB1 and BB2, where BB1 was found to be externally
mixed, exhibiting a combination of BB and anthropogenic marine aerosols. On
the other hand, BB2 exhibited internal mixing dominated by aged BB aerosol. Our analysis from mobile and stationary measurements
highlights that both CO and acetonitrile are likely impacted by local
sources even during the BB events and specifically that acetonitrile cannot
be used as a unique BB tracer for dilute BB plumes in an industrially
influenced location. A suitable volatile organic compound (VOC) tracer would need to be emitted in high
concentrations during BB, resistant to degradation during transport, unique
to BB and able to be measured in the field. This study effectively
demonstrates that AAE and aerosol BB tracers served as precise and effective
tracers in these complex emission scenarios. Network deployment of
multiwavelength photometers holds promise for enhancing our understanding of
BB impacts on air quality and supporting informed decision-making for
effective mitigation strategies in locations with mixed sources and
influence of dilute BB plumes. To demonstrate the relevance of such an
aerosol optical network, we provide evidence of the potential regional
impacts of these transported BB events on urban O3 levels using
measurements from the surface air quality monitoring network in Texas.
Black carbon (BC) contributes to Arctic climate warming, yet source attributions are inaccurate due to lacking observational constraints and uncertainties in emission inventories. Year-round, ...isotope-constrained observations reveal strong seasonal variations in BC sources with a consistent and synchronous pattern at all Arctic sites. These sources were dominated by emissions from fossil fuel combustion in the winter and by biomass burning in the summer. The annual mean source of BC to the circum-Arctic was 39 ± 10% from biomass burning. Comparison of transport-model predictions with the observations showed good agreement for BC concentrations, with larger discrepancies for (fossil/biomass burning) sources. The accuracy of simulated BC concentration, but not of origin, points to misallocations of emissions in the emission inventories. The consistency in seasonal source contributions of BC throughout the Arctic provides strong justification for targeted emission reductions to limit the impact of BC on climate warming in the Arctic and beyond.
Throughout South Asia biomass is commonly used as a fuel source for cooking and heating homes. The smoke from domestic use of these fuels is expected to be a major source of atmospheric particulate ...matter in the region and needs to be characterized for input in regional source apportionment models and global climate models. Biomass fuel samples including coconut leaves, rice straw, jackfruit branches, dried cowdung patties, and biomass briquettes manufactured from compressed biomass material were obtained from Bangladesh. The fuel samples were burned in a wood stove to collect and characterize the particulate matter emissions. The bulk chemical composition including total organic and elemental carbon, sulfate, nitrate, ammonium and chloride ions, and bulk elements such as potassium and sodium did not show conclusive differences among the biomass samples tested. Unique features, however, exist in the detailed organic characterization of the combustion smoke from the different sources. The organic compound fingerprints of the particulate matter are shown to be distinct from one another and distinct from North American wood fuels. Fecal stanols including 5β‐stigmastanol, coprostanol, and cholestanol are found to be good molecular markers for the combustion of cowdung. Additionally, the patterns of methoxyphenols and plant sterols provide a unique signature for each biomass sample and are conducive as source apportionment tracers.
Black carbon (BC) aerosols impact climate and air quality. Since BC from fossil versus biomass combustion have different optical properties and different abilities to penetrate the lungs, it is ...important to better understand their relative contributions in strongly affected regions such as South Asia. This study reports the first year-round 14C-based source apportionment of elemental carbon (EC), the mass-based correspondent to BC, using as regional receptor sites the international Maldives Climate Observatory in Hanimaadhoo (MCOH) and the mountaintop observatory of the Indian Institute of Tropical Meteorology in Sinhagad, India (SINH). For the highly-polluted winter season (December-March), the fractional contribution to EC from biomass burning (fbio) was 53 5% (n = 6) at MCOH and 56 3% at SINH (n = 5). The fbio for the non-winter remainder was 53 11% (n = 6) at MCOH and 48 8% (n = 7) at SINH. This observation-based constraint on near-equal contributions from biomass burning and fossil fuel combustion at both sites compare with predictions from eight technology-based emission inventory (EI) models for India of (fbio)EI spanning 55-88%, suggesting that most current EI for Indian BC systematically under predict the relative contribution of fossil fuel combustion. A continued iterative testing of bottom-up EI with top-down observational source constraints has the potential to lead to reduced uncertainties regarding EC sources and emissions to the benefit of both models of climate and air quality as well as guide efficient policies to mitigate emissions.
Prescribed burning is a significant source of fine particulate matter (PM2.5) in the southeastern United States. However, limited data exist on the emission characteristics from this source. Various ...organic and inorganic compounds both in the gas and particle phase were measured in the emissions of prescribed burnings conducted at two pine-dominated forest areas in Georgia. The measurements of volatile organic compounds (VOCs) and PM2.5 allowed the determination of emission factors for the flaming and smoldering stages of prescribed burnings. The VOC emission factors from smoldering were distinctly higher than those from flaming except for ethene, ethyne, and organic nitrate compounds. VOC emission factors show that emissions of certain aromatic compounds and terpenes such as α and β-pinenes, which are important precursors for secondary organic aerosol (SOA), are much higher from active prescribed burnings than from fireplace wood and laboratory open burning studies. Levoglucosan is the major particulate organic compound (POC) emitted for all these studies, though its emission relative to total organic carbon (mg/g OC) differs significantly. Furthermore, cholesterol, an important fingerprint for meat cooking, was observed only in our in situ study indicating a significant release from the soil and soil organisms during open burning. Source apportionment of ambient primary fine particulate OC measured at two urban receptor locations 20−25 km downwind yields 74 ±11% during and immediately after the burns using our new in situ profile. In comparison with the previous source profile from laboratory simulations, however, this OC contribution is on average 27 ±5% lower.
The air quality of the Texas Gulf Coast region historically has been
influenced heavily by regional shipping emissions. However, the effects of
the recently established North American Emissions ...Control Area on aerosol
concentrations and properties in this region are presently unknown. In order
to better understand the current sources and processing mechanisms
influencing coastal aerosol near Houston, a high-resolution time-of-flight
aerosol mass spectrometer (HR-ToF-AMS) was deployed for 3 weeks at a
coastal location during May–June 2016. Total mass loadings of organic and
inorganic non-refractory aerosol components during onshore flow periods were
similar to those published before establishment of the regulations. Based on
estimated methanesulfonic acid (MSA) mass loadings and published biogenic
MSA / non-sea-salt sulfate (nss-SO4) ratios, an average of over 75 %
of the observed nss-SO4 was from anthropogenic sources, predominantly
shipping emissions. Mass spectral analysis indicated that for periods with
similar backward-trajectory-averaged meteorological conditions, air masses
influenced by shipping emissions had an increased mass fraction of ions
related to carboxylic acids and larger oxygen-to-carbon ratios than those
that avoided shipping lanes, suggesting that shipping emissions increase
marine organic aerosol (OA) oxidation state. Amine fragment mass loadings
were correlated positively with anthropogenic nss-SO4 during onshore
flow, implying anthropogenic–biogenic interaction in marine OA production.
Model calculations also suggest that advection of shipping-derived aerosol
may enhance inland aqueous-phase secondary OA production. These results imply
a continuing role of shipping emissions on aerosol properties over the Gulf
of Mexico and suggest that further regulation of shipping fuel sulfur content
will reduce coastal submicron aerosol mass loadings near Houston.
The trends in secondary organic aerosol at a remote location are studied using atmospheric fine particulate matter samples collected at Seney National Wildlife Refuge (NWR) in northern Michigan. ...Detailed analysis of particle-phase organic compounds revealed very low concentra tions of primary anthropogenic emissions and relatively high levels of organic di-, tri-, and tetracarboxylic acids thought to be indicators of secondary organic aerosols. Seasonal changes in these organic compounds were tracked by analyzing composites of monthly average samples. The concentration of aromatic and aliphatic dicarboxylic acids peak in July and taper off in the fall, which coincides with fine particle organic carbon concentration. In contrast, a chemical mass balance model used to quantify primary sources of particulate matter shows higher contributions from primary emissions in the winter. Complementing the monthly average concentrations, event-based composites of high volume samples were used to track the different species of secondary organic aerosol at the Seney NWR location. The distribution of aliphatic diacids and the aromatic di- and triacids varied with different atmospheric conditions, which suggests different precursor gases for these secondary organic aerosol components. The aliphatic diacid concentrations track with ambient concentrations of particle-phase pinonic acid. In addition, back-trajectories for the eight event-based composites are compared to the organic acid distributions and are linked to the distribution of organic acids present in the composites.
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