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Contributions of transported Prudhoe Bay oil field emissions to the aerosol population in Utqiaġvik, Alaska
Loss of sea ice is opening the Arctic to increasing development involving oil and gas extraction and shipping. Given the significant impacts of absorbing aerosol and secondary aerosol precursors emitted within the rapidly warming Arctic region, it is necessary to characterize local anthropogenic aerosol sources and compare to natural conditions. From August to September 2015 in Utqiaġvik (Barrow), AK, the chemical composition of individual atmospheric particles was measured by computer-controlled scanning electron microscopy with energy-dispersive X-ray spectroscopy (0.13-4 μm projected area diameter) and real-time single-particle mass spectrometry (0.2-1.5 μm vacuum aerodynamic diameter). During periods influenced by the Arctic Ocean (70 % of the study), our results show that fresh sea spray aerosol contributed ∼ 20 %, by number, of particles between 0.13 and 0.4 μm, 40-70 % between 0.4 and 1 μm, and 80-100 % between 1 and 4 μm particles. In contrast, for periods influenced by emissions from Prudhoe Bay (10 % of the study), the third largest oil field in North America, there was a strong influence from submicron (0.13-1 μm) combustion-derived particles (20-50 % organic carbon, by number; 5-10 % soot by number). While sea spray aerosol still comprised a large fraction of particles (90 % by number from 1 to 4 μm) detected under Prudhoe Bay influence, these particles were internally mixed with sulfate and nitrate indicative of aging processes during transport. In addition, the overall mode of the particle size number distribution shifted from 76 nm during Arctic Ocean influence to 27 nm during Prudhoe Bay influence, with particle concentrations increasing from 130 to 920 cm-3 due to transported particle emissions from the oil fields. The increased contributions of carbonaceous combustion products and partially aged sea spray aerosol should be considered in future Arctic atmospheric composition and climate simulations
Contributions of Transported Prudhoe Bay Oilfield Emissions to the Aerosol Population in Utqiaġvik, Alaska
Loss of sea ice is opening the Arctic to increasing development involving oil and gas extraction and shipping. Given the significant impacts of absorbing aerosol and secondary aerosol precursors emitted within the rapidly warming Arctic region, it is necessary to characterize local anthropogenic aerosol sources and compare to natural conditions. From August to September 2015 in Utqiaġvik (Barrow), AK, the chemical composition of individual atmospheric particles was measured by computer-controlled scanning electron microscopy with energy-dispersive X-ray spectroscopy (0.13-4 μm projected area diameter) and real-time single-particle mass spectrometry (0.2-1.5 μm vacuum aerodynamic diameter). During periods influenced by the Arctic Ocean (70 % of the study), our results show that fresh sea spray aerosol contributed ∼ 20 %, by number, of particles between 0.13 and 0.4 μm, 40-70 % between 0.4 and 1 μm, and 80-100 % between 1 and 4 μm particles. In contrast, for periods influenced by emissions from Prudhoe Bay (10 % of the study), the third largest oil field in North America, there was a strong influence from submicron (0.13-1 μm) combustion-derived particles (20-50 % organic carbon, by number; 5-10 % soot by number). While sea spray aerosol still comprised a large fraction of particles (90 % by number from 1 to 4 μm) detected under Prudhoe Bay influence, these particles were internally mixed with sulfate and nitrate indicative of aging processes during transport. In addition, the overall mode of the particle size number distribution shifted from 76 nm during Arctic Ocean influence to 27 nm during Prudhoe Bay influence, with particle concentrations increasing from 130 to 920 cm-3 due to transported particle emissions from the oil fields. The increased contributions of carbonaceous combustion products and partially aged sea spray aerosol should be considered in future Arctic atmospheric composition and climate simulations
Unexpected Contributions of Sea Spray and Lake Spray Aerosol to Inland Particulate Matter
Sea spray aerosol (SSA) and lake
spray aerosol (LSA) from wave
breaking contribute to particulate matter (PM) in coastal regions
near oceans and freshwater lakes, respectively. However, SSA and LSA
contributions to atmospheric aerosol populations in inland regions
are poorly understood because of difficulties differentiating them
from other inland sources when using bulk particle measurements. Herein,
we show that SSA and LSA episodically contribute to atmospheric aerosol
populations at a rural site in northern Michigan >700 and >25
km from
the nearest seawater and Great Lakes sources, respectively. During
July 2014, individual SSA and LSA particles were identified by single-particle
mass spectrometry and electron microscopy and then combined with air
mass trajectory analysis for source apportionment. SSA comprised up
to 33 and 20% of PM mass (0.5–2.0 μm) during two multiday
transport events from Hudson Bay and a 3% average background outside
these periods. LSA transported from Lake Michigan reached a maximum
of 7% of PM mass (0.5–2 μm) during a daylong high-wind
event and contributed a 3% average background during the remainder
of the study. The observation of SSA and LSA transported inland motivates
further studies of the impacts of wave breaking particles on cloud
formation and air quality at inland locations far from marine and
freshwater sources
Aerosol Emissions from Great Lakes Harmful Algal Blooms
In
freshwater lakes, harmful algal blooms (HABs) of <i>Cyanobacteria</i> (blue-green algae) produce toxins that impact human health. However,
little is known about the lake spray aerosol (LSA) produced from wave-breaking
in freshwater HABs. In this study, LSA were produced in the laboratory
from freshwater samples collected from Lake Michigan and Lake Erie
during HAB and nonbloom conditions. The incorporation of biological
material within the individual HAB-influenced LSA particles was examined
by single-particle mass spectrometry, scanning electron microscopy
with energy-dispersive X-ray spectroscopy, and fluorescence microscopy.
Freshwater with higher blue-green algae content produced higher number
fractions of individual LSA particles that contained biological material,
showing that organic molecules of biological origin are incorporated
in LSA from HABs. The number fraction of individual LSA particles
containing biological material also increased with particle diameter
(greater than 0.5 μm), a size dependence that is consistent
with previous studies of sea spray aerosol impacted by phytoplankton
blooms. Similar to sea spray aerosol, organic carbon markers were
most frequently observed in individual LSA particles less than 0.5
μm in diameter. Understanding the transfer of biological material
from freshwater to the atmosphere via LSA is crucial for determining
health and climate effects of HABs