26 research outputs found
Emissions
This chapter assesses the current state of the science regarding the composition, intensity, and drivers of wildland fire emissions in the USA and Canada. Globally and in the USA wildland fires are a major source of gases and aerosols which have significant air quality impacts and climate interactions. Wildland fire smoke can trigger severe pollution episodes with substantial effects on public health. Fire emissions can degrade air quality at considerable distances downwind, hampering efforts by air regulators to meet air standards. Fires are a major global source of aerosols which affect the climate system by absorbing and scattering radiation and by altering optical properties, coverage, and lifetime of clouds. A thorough understanding of fire emissions is essential for effectively addressing societal and climate consequences of wildland fire smoke
Increased cytotoxicity of oxidized flame soot
AbstractCombustion–generated particles released into the atmosphere undergo reactions with oxidants, which can change the particles’ physiochemical characteristics. In this work, we compare the physical and chemical properties and cellular response of particles fresh from a flame with those oxidized by ozone and nitrogen dioxide. The reaction with ozone and nitrogen dioxide does not significantly modify the physical characteristics of the particles (primary particle size, fractal dimension, and surface area). However, oxidation affects the chemical characteristics of the particles, creating more oxygen and nitrogen containing functional groups, and increases their hydrophilicity. In addition, oxidized soot generates more reactive oxygen species, as measured by the dithiothreitol (DTT) assay. Furthermore, oxidized soot is 1.5 – 2 times more toxic than soot that was not reacted with ozone, but the inflammatory response, measured by interleukin–8 (IL–8) secretion, is unchanged. These results imply that combustion–generated particles released into the atmosphere will have an increased toxicity on or after high ozone days
Characterization of Particle Emissions and Fate of Nanomaterials During Incineration
As the use of nanotechnology in consumer products continues to grow, it is inevitable that some nanomaterials will end up in the waste stream and will be incinerated. Through laboratory-scale incineration of paper and plastic wastes containing nanomaterials, we assessed their effect on emissions of particulate matter (PM) and the effect of incineration on the nanomaterials themselves. The presence of nanomaterials did not significantly influence the particle number emission factor. The PM size distribution was not affected except at very high mass loadings (10 wt%) of the nanomaterial, in which case the PM shifted toward smaller sizes; such loadings are not expected to be present in many consumer products. Metal oxide nanomaterials reduced emissions of particle-bound polycyclic aromatic hydrocarbons. Most of the nanomaterials that remained in the bottom ash retained their original size and morphology but formed large aggregates. Only small amounts of the nanomaterials (0.023–180 mg g−1 of nanomaterial) partitioned into PM, and the emission factors of nanomaterials from an incinerator equipped with an electrostatic precipitator are expected to be low. However, a sustainable disposal method for nanomaterials in the bottom ash is needed, as a majority of them partitioned into this fraction and may thus end up in landfills upon disposal of the ash
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Sampling Artifacts from Conductive Silicone Tubing
We report evidence that carbon impregnated conductive silicone tubing used in aerosol sampling systems can introduce two types of experimental artifacts: 1) silicon tubing dynamically absorbs carbon dioxide gas, requiring greater than 5 minutes to reach equilibrium and 2) silicone tubing emits organic contaminants containing siloxane that adsorb onto particles traveling through it and onto downstream quartz fiber filters. The consequence can be substantial for engine exhaust measurements as both artifacts directly impact calculations of particulate mass-based emission indices. The emission of contaminants from the silicone tubing can result in overestimation of organic particle mass concentrations based on real-time aerosol mass spectrometry and the off-line thermal analysis of quartz filters. The adsorption of siloxane contaminants can affect the surface properties of aerosol particles; we observed a marked reduction in the water-affinity of soot particles passed through conductive silicone tubing. These combined observations suggest that the silicone tubing artifacts may have wide consequence for the aerosol community and should, therefore, be used with caution. Gentle heating, physical and chemical properties of the particle carriers, exposure to solvents, and tubing age may influence siloxane uptake. The amount of contamination is expected to increase as the tubing surface area increases and as the particle surface area increases. The effect is observed at ambient temperature and enhanced by mild heating (<100 oC). Further evaluation is warranted
Toxicity of Silver Nanoparticles at the Air-Liquid Interface
Silver nanoparticles are one of the most prevalent nanomaterials in consumer products. Some of these products are likely to be aerosolized, making silver nanoparticles a high priority for inhalation toxicity assessment. To study the inhalation toxicity of silver nanoparticles, we have exposed cultured lung cells to them at the air-liquid interface. Cells were exposed to suspensions of silver or nickel oxide (positive control) nanoparticles at concentrations of 2.6, 6.6, and 13.2 μg cm−2 (volume concentrations of 10, 25, and 50 μg ml−1) and to 0.7 μg cm−2 silver or 2.1 μg cm−2 nickel oxide aerosol at the air-liquid interface. Unlike a number of in vitro studies employing suspensions of silver nanoparticles, which have shown strong toxic effects, both suspensions and aerosolized nanoparticles caused negligible cytotoxicity and only a mild inflammatory response, in agreement with animal exposures. Additionally, we have developed a novel method using a differential mobility analyzer to select aerosolized nanoparticles of a single diameter to assess the size-dependent toxicity of silver nanoparticles
Effects of Aftermarket Control Technologies on Gas and Particle Phase Oxidative Potential from Diesel Engine Emissions
Particulate
matter (PM) originating from diesel combustion is a
public health concern due to its association with adverse effects
on respiratory and cardiovascular diseases and lung cancer. This study
investigated emissions from three stationary diesel engines (gensets)
and varying power output (230 kW, 400 kW, and 600 kW) at 50% and 90%
load to determine concentrations of gaseous (GROS) and PM reactive
oxygen species (PMROS). In addition, the influence of three modern
emission control technologies on ROS emissions was evaluated: active
and passive diesel particulate filters (A-DPF and P-DPF) and a diesel
oxidation catalyst (DOC). PMROS made up 30–50% of the total
ROS measured without aftermarket controls. All applied controls removed
PMROS by more than 75% on average. However, the oxidative potential
of PM downstream of these devices was not diminished at the same rate
and particles surviving the A-PDF had an even higher oxidative potential
on a per PM mass basis compared to the particles emitted by uncontrolled
gensets. Further, the GROS as compared to PMROS emissions were not
reduced with the same efficiency (<36%). GROS concentrations were
highest with the DOC in use, indicating continued formation of GROS
with this control. Correlation analyses showed that PMROS and to a
lesser extent GROS have a good correlation with semivolatile organic
carbon (OC1) subfraction. In addition, results suggest that chemical
composition, rather than PM size, is responsible for differences in
the PM oxidative potential
Emissions of Polycyclic Aromatic Hydrocarbons, Polychlorinated Dibenzo‑<i>p</i>‑Dioxins, and Dibenzofurans from Incineration of Nanomaterials
Disposal
of some nanomaterial-laden waste through incineration
is inevitable, and nanomaterials’ influence on combustion byproduct
formation under high-temperature, oxidative conditions is not well
understood. This work reports the formation of polycyclic aromatic
hydrocarbons (PAHs) and polychlorinated-dibenzo-<i>p</i>-dioxins and dibenzofurans (PCDD/Fs) from incineration of paper and
plastic waste containing various nanomaterials, including titania,
nickel oxide, silver, ceria, iron oxide, quantum dots, and C<sub>60</sub>-fullerene, in a laboratory-scale furnace. The presence of nanomaterials
in the waste stream resulted in higher emissions of some PAH species
and lower emissions of others, depending on the type of waste. The
major PAH species formed were phenanthrene and anthracene, and emissions
were sensitive to the amount of nanomaterials in the waste. Generally,
there were no significant differences in emission factors for the
larger PAH species when nanomaterials were added to the waste. The
total PAH emission factors were on average ∼6 times higher
for waste spiked with nanomaterials v. their bulk counterparts. Emissions
of chlorinated dioxins from polyÂ(vinyl chloride) (PVC) waste were
not detected; however, chlorinated furans were formed at elevated
concentrations with wastes containing silver and titania nanomaterials,
and toxicity was attributable mainly to 2,3,4,7,8-pentachlorodibenzofuran.
The combination of high specific surface area and catalytic, including
electrocatalytic, properties of nanomaterials might be responsible
for affecting the formation of toxic pollutants during incineration