Composition and size distribution of metals in diesel exhaust particulates

Abstract

This study characterizes the size distribution and composition of metals in diesel exhaust particulates (DEPs) emitting from four driving conditions. We quantified 17 metals in DEPs (34-1000 nm) with a total concentration ranging from 5.4-7.0 microg/m(3). Depending on driving conditions, ultrafine (<100 nm) and accumulation-mode DEPs carried up to 41% and 75% of the quantified metals, respectively. The size distribution of individual metals consistently indicates that under a medium (60%) engine load, more than three fourths of quantified metals partitioned in accumulation-mode DEPs, indicating prominent heterogeneous condensation. Enhancing the engine load up to 100% significantly increased metals in ultrafine DEPs around 1.8 times, particularly in DEP < 66 nm, suggesting enhanced metal nucleation. Under the maximum engine load, metals and elemental carbon showed an opposite trend in size distribution, providing tailpipe evidence that metals may catalyze oxidation of DEPs during combustion. Among the identified metals, Fe (2.3-3.9 microg/m(3)) was most abundant contributing to more than 43% of quantified metals, followed by Li, V, and Pb. Although As and Cd together contributed to less than 2% of the total quantified metals in DEP (<1 microm), their concentrations peaked in ultrafine DEPs under the maximum engine load, indicating that a decrease in engine loads can reduce amounts and toxicity of ultrafine DEPs.

Effect of Operating and Sampling Conditions on the Exhaust Gas Composition of Small-Scale Power Generators

“…The PM trend illustrates how fuel oxidation was more efficient at higher engine loads. This is in agreement with previous studies [13], [17], where the lower PM mass emission rates at medium load conditions were explained by the fact that manufacturers optimize the engines for medium load applications. Additionally, literature reported an average PM mass emission rate for 18 back-up gen-sets which slightly increased when switching from medium to high load conditions [13].…”

“…The increase of both Mn and Pb can be explained by corrosion of the engine, a process that is enhanced at higher load/temperature conditions [37]. These results are in accordance to literature data, reporting higher element concentrations (µg m −3 ) for increasing load conditions [17], [19]. It is furthermore reported in literature that Cr, Fe, Ti and Ni could originate from wear and corrosion processes [7], [38].…”

“…Recent literature data quantify 17 metals in diesel exhaust particles ranging from 5.4 to 7.0 µg m −3 [17], which is the same order of magnitude as our results. However, one should be careful when comparing the order of magnitude of elemental concentrations, since it strongly depends on the studied PM source.…”

An Overview of Airborne Nanoparticle Filtration and Thermal Rebound Theory

“…The examples of nanoparticle combustion sources are transportation (Buseck and Adachi, 2008;Lim et al, 2008;Lim et al, 2009;Yin et al, 2012), indoor fumes, smoking (Hofmann et al, 2009;Van Dijk et al, 2011), cooking (Wallace et al, 2004;Torkmahalleh et al, 2012), heating (Jung et al, 2006), biomass, burning (Weimer et al, 2009), etc. Nanoparticles are produced from other sources as well such as from polymers (Tsai et al, 2008;Motzkus et al, 2012), cleaning, laser printers , photocopiers, agriculture (Buseck and Adachi, 2008), and welding.…”

Diesel Exhaust Particles Enhance <b><i>MUC4</i></b> Expression in NCI-H292 Cells and Nasal Epithelial Cells via the p38/CREB Pathway

“…The elemental carbon core has a large surface area, and hundreds of chemicals and transition metals are attached to it. Those attached to the elemental carbon core, especially transition metals, are supposed to participate in the generation of reactive oxygen species (ROS), which increase inflammation in the respiratory system [13]. Much concern related to the mechanisms by which DEPs exert their harmful effects involves ROS generation and oxidative stress in the exposed cells, and accumulating evidence supports the important role of oxidative stress in the harmful effects of DEPs.…”