Total Particle Number Emissions from Modern Diesel, Natural Gas, and Hybrid Heavy-Duty Vehicles During On-Road Operation

Particle emissions from heavy-duty vehicles (HDVs) have significant environmental and public health impacts. This study measured total particle number emission factors (PNEFs) from six newly certified HDVs powered by diesel and compressed natural gas totaling over 6800 miles of on-road operation in California. Distance-, fuel- and work-based PNEFs were calculated for each vehicle. Distance-based PNEFs of vehicles equipped with original equipment manufacturer (OEM) diesel particulate filters (DPFs) in this study have decreased by 355–3200 times compared to a previous retrofit DPF dynamometer study. Fuel-based PNEFs were consistent with previous studies measuring plume exhaust in the ambient air. Meanwhile, on-road PNEF shows route and technology dependence. For vehicles with OEM DPFs and Selective Catalytic Reduction Systems, PNEFs under highway driving (i.e., 3.34 × 10¹² to 2.29 × 10¹³ particles/mile) were larger than those measured on urban and drayage routes (i.e., 5.06 × 10¹¹ to 1.31 × 10¹³ particles/mile). This is likely because a significant amount of nucleation mode volatile particles were formed when the DPF outlet temperature reached a critical value, usually over 310 °C, which was commonly achieved when vehicle speed sustained over 45 mph. A model year 2013 diesel HDV produced approximately 10 times higher PNEFs during DPF active regeneration events than nonactive regeneration

Chemical Speciation of Vanadium in Particulate Matter Emitted from Diesel Vehicles and Urban Atmospheric Aerosols

We report on the development and application of an integrated set of analytical tools that enable accurate measurement of total, extractable, and, importantly, the oxidation state of vanadium in sub-milligram masses of environmental aerosols and solids. Through rigorous control of blanks, application of magnetic-sector-ICPMS, and miniaturization of the extraction/separation methods we have substantially improved upon published quantification limits. The study focused on the application of these methods to particulate matter (PM) emissions from diesel vehicles, both in baseline configuration without after-treatment and also equipped with advanced PM and NO_<i>x</i> emission controls. Particle size-resolved vanadium speciation data were obtained from dynamometer samples containing total vanadium pools of only 0.2–2 ng and provide some of the first measurements of the oxidation state of vanadium in diesel vehicle PM emissions. The emission rates and the measured fraction of V(V) in PM from diesel engines running without exhaust after-treatment were both low (2–3 ng/mile and 13–16%, respectively). The V(IV) species was measured as the dominant vanadium species in diesel PM emissions. A significantly greater fraction of V(V) (76%) was measured in PM from the engine fitted with a prototype vanadium-based selective catalytic reductors (V-SCR) retrofit. The emission rate of V(V) determined for the V-SCR equipped vehicle (103 ng/mile) was 40-fold greater than that from the baseline vehicle. A clear contrast between the PM size-distributions of V(V) and V(IV) emissions was apparent, with the V(V) distribution characterized by a major single mode in the ultrafine (<0.25 μm) size range and the V(IV) size distribution either flat or with a small maxima in the accumulation mode (0.5–2 μm). The V(V) content of the V-SCR PM (6.6 μg/g) was 400-fold greater than that in PM from baseline (0.016 μg/g) vehicles, and among the highest of all environmental samples examined. Synchrotron based V 1s XANES spectroscopy of vanadium-containing fine-particle PM from the V-SCR identified V₂O₅ as the dominant vanadium species

Using a new inversion matrix for a fast-sizing spectrometer and a photo-acoustic instrument to determine suspended particulate mass over a transient cycle for light-duty vehicles

<p>Integrated particle size distribution (IPSD) is a promising alternative method for estimating particulate matter (PM) emissions at low levels. However, a recent light-duty vehicle (LDV) emissions study showed that particle mass estimated using IPSD (<i>M</i>_IPSD) with the TSI Engine Exhaust Particle Sizer (EEPS) Default Matrix was 56–75% lower than mass derived using the reference gravimetric method (<i>M</i>_Grav) over the Federal Test Procedure (FTP). In this study, <i>M</i>_IPSD calculated with a new inversion matrix, the Soot Matrix, is compared with <i>M</i>_Grav and also photoacoustic soot mass (<i>M</i>_Soot), to evaluate potential improvement of the IPSD method for estimating PM mass emissions from LDVs. In addition, an aerodynamic particle sizer (APS) was used to estimate mass emission rates attributed to larger particles (0.54–2.5 µm in aerodynamic diameter) that are not measured by the EEPS. Based on testing of 10 light-duty vehicles over the FTP cycle, the Soot Matrix significantly improved agreement between <i>M</i>_IPSD and <i>M</i>_Grav by increasing slopes of <i>M</i>_IPSD/<i>M</i>_Grav from 0.45–0.57 to 0.76–1.01 for gasoline direct injected (GDI) vehicles; however, for port-fuel injection (PFI) gasoline vehicles, a significant discrepancy still existed between <i>M</i>_IPSD and <i>M</i>_Grav, with <i>M</i>_IPSD accounting for 34 ± 37% of <i>M</i>_Grav. For all vehicles, strong correlations between <i>M</i>_IPSD and <i>M</i>_Soot were obtained, indicating the IPSD method is capable of capturing mass of soot particles. The discrepancy between the <i>M</i>_IPSD and <i>M</i>_Grav for PFI vehicles, which have relatively low PM emissions (0.22 to 1.83 mg/mile), could be partially due to limited size range of the EEPS by not capturing larger particles (0.54–2.5 µm) that accounts for ∼0.08 mg/mile of PM emission, uncertainties of particle effective density, and/or gas-phase adsorption onto filters that is not detected by <i>in situ</i> aerosol instrumentation.</p> <p>Copyright © 2016 American Association for Aerosol Research</p

Results of ReHo shown as a comparison of KCC maps between homosexual and heterosexual groups in the resting state (two-sample <i>t</i>-test; p<0.05, corrected).

<p>T-score bars are shown on the right. Hot and cold colors indicate increased and decreased ReHo in homosexual group, respectively, compared with heterosexual group. The identified brain regions are the following: (A&B) right precuneus; (C) right superior occipital gyrus; (D) left cuneus; (E) left temporal lobe; (F) right middle occipital gyrus; (G) right extra-nuclear white matter; (H) left inferior occipital; (I) right midbrain; (J) left midbrain; (K) left rectal gyrus.</p

Brain regions showing significantly correlation with the left inferior occipital gyurs in homosexual group (one sample <i>t-</i>test, p<0.05, corrected).

<p>Brain regions showing significantly correlation with the left inferior occipital gyurs in homosexual group (one sample <i>t-</i>test, p<0.05, corrected).</p

Significant correlations of FC in the resting state with Kinsey Scale scores within the homosexual group (correlation analysis, p<0.01, corrected).

<p>R-value are shown on the right. The identified region is right thalamus (A) and right cuneus (B).</p

Demographic data and sexual preference characteristics for 26 homosexual and 26 heterosexual participants.

a<p>All heterosexual participants scored themselves as exclusive heterosexual, whereas none of the homosexual participants scored themselves as heterosexual but at least bisexual.</p>b<p>SD: standard deviation,</p>c<p>p: the age difference between two groups was no statistically significant.</p

Regional homogeneity (ReHo) in the resting state, shown as maps of Kendall’s coefficient of concordance (KCC) within the homosexual group (A) and heterosexual group (B) (one-sample <i>t-</i>test; p<0.05, with multiple correction).

<p>T-sore bars are shown on the right. Hot and cold colors indicate higher or lower than the global mean, respectively.</p

Brain regions showing significant differences in functional connectivity between homosexual and heterosexual groups (two-sample <i>t-</i>test, p<0.05, corrected).

<p>Brain regions showing significant differences in functional connectivity between homosexual and heterosexual groups (two-sample <i>t-</i>test, p<0.05, corrected).</p

Differences in functional connectivity (differences in r-value maps) in the resting state between homosexual and heterosexual groups (two-sample <i>t</i>-test; p<0.05, corrected).

<p>T-score bars are shown on the right. Hot and cold colors indicate increased and decreased FC of homosexual group, respectively, compared with heterosexual group. The identified brain regions are the following: (A) left inferior occipital gyrus; (B) left middle temporal gyrus; (C) right cuneus; (D) left supramarginal gyrus.</p