Characterization of the fugitive particulate emissions from construction mud/dirt carryout.

Although the fugitive dust associated with construction mud/dirt carryout can represent a substantial portion of the particulate matter (PM) emissions inventory in nonattainment areas, it has not been well characterized by direct sampling methods. In this paper, a research program is described that directly determined both PM10 and PM2.5 (particles < or =10 and 2.5 microm in classical aerodynamic diameter, respectively) emission factors for mud/dirt carryout from a major construction project located in metropolitan Kansas City, MO. The program also assessed the contribution of automotive emissions to the total PM2.5 burden and determined the baseline emissions from the test road. As part of the study, both time-integrated and continuous exposure-profiling methods were used to assess the PM emissions, including particle size and elemental composition. This research resulted in overall PM10 and PM2.5 emission factors of 6 and 0.2 g/vehicle, respectively. Although PM10 is within the range of prior U.S. Environmental Protection Agency (EPA) guidance, the PM2.5 emission factor is far lower than previous estimates published by EPA. In addition, based on both the particle size and chemical data obtained in the study, a major portion of the PM2.5 emissions appears to be attributable to automotive exhaust from light-duty, gasoline-powered vehicles and not to the fugitive dust associated with reentrained mud/dirt carryout.

Speciation of gas-phase and fine particle emissions from burning of foliar fuels.

Fine particle matter with aerodynamic diameter <2.5 microm (PM2.5) and gas-phase emissions from open burning of six fine (foliar) fuels common to fire-prone U.S. ecosystems are investigated. PM2.5 distribution is unimodal within the 10-450 nm range, indicative of an accumulation mode. Smoldering relative to flaming combustion shows smaller particle number density per unit time and median size. Over 100 individual organic compounds in the primarily carbonaceous (>70% by mass) PM2.5 are chemically speciated by gas chromatography/mass spectrometry. Expressed as a percent of PM2.5 mass, emission ranges by organic compound class are as follows: n-alkane (0.1-2%), polycyclic aromatic hydrocarbon (PAH) (0.02-0.2%), n-alkanoic acid (1-3%), n-alkanedioic acid (0.06-0.3%), n-alkenoic acid (0.3-3%), resin acid (0.5-6%), triterpenoid (0.2-0.5%), methoxyphenol (0.5-3%), and phytosterol (0.2-0.6%). A molecular tracer of biomass combustion, the sugar levoglucosan is abundant and constitutes a remarkably narrow PM2.5 mass range (2.8-3.6%). Organic chemical signatures in PM2.5 from open combustion of fine fuels differ with those of residential wood combustion and other related sources, making them functional for source-receptor modeling of PM. Inorganic matter [PM2.5 - (organic compounds + elemental carbon)] on average is estimated to make up 8% of the PM2.5. Wavelength dispersive X-ray fluorescence spectroscopy and ion chromatography identify 3% of PM2.5 as elements and water-soluble ions, respectively. Compared with residential wood burning, the PM2.5 of fine fuel combustion is nitrate enriched but shows lower potassium levels. Gas-phase C2-C13 hydrocarbon and C2-C9 carbonyl emissions are speciated by respective EPA Methods T0-15 and T0-11A. They comprise mainly low molecular weight C2-C3 compounds and hazardous air pollutants (48 wt % of total quantified volatile organic carbon).

Thermochemistry of Oxo Transfer from Coordinated Nitrite in the Dinitro(5,10,15,20-tetrakis(o-pivalamidophenyl)porphinato)iron(III) Anion.

The thermochemistry of oxo transfer from coordinated nitrite in the dinitro(5,10,15,20-tetrakis(o-pivalamidophenyl)porphinato)iron(III) anion, ion-paired with the tetrapropylammonium ion, {[Fe(III)TpivPP(NO(2))(2)](-)Pr(4)N(+)}, has been evaluated in acetonitrile solution. This oxo-transfer half-reaction of {[Fe(III)TpivPP(NO(2))(2)](-)Pr(4)N(+)} has been assessed on the basis of the determination of the E(1/2) = +0.54 V vs SHE for the reversible [Fe(II/III)TpivPP(NO)(NO(2))](-)(/0) couple and the measurement of the formation constants for the association of NO and NO(2)(-) with the mononitroiron(III) porphyrin derivative. The formation constant for nitric oxide association, K(NO), has the value (1.21 +/- 0.08) x 10(3). The stability constant, K(2), for association of a second nitro ligand in 0.0100 M tetrapropylammonium perchlorate medium has been estimated as 2.18 x 10(3). The oxo-transfer half-reaction free energy, DeltaG degrees ((X/XO)), for addition of oxygen to [Fe(II)TpivPP(NO)(NO(2))](-) to form {[Fe(III)TpivPP(NO(2))(2)](-)Pr(4)N(+)} has been found to be -50 kJ/mol.