title: Atmospheric impacts of black carbon emission reductions through the strategic use of biodiesel in California.
abstract: The use of biodiesel as a replacement for petroleum-based diesel fuel has gained interest as a strategy for greenhouse gas emission reductions, energy security, and economic advantage. Biodiesel adoption may also reduce particulate elemental carbon (EC) emissions from conventional diesel engines that are not equipped with after-treatment devices. This study examines the impact of biodiesel blends on EC emissions from a commercial off-road diesel engine and simulates the potential public health benefits and climate benefits. EC emissions from the commercial off-road engine decreased by 76% when ultra-low sulfur commercial diesel (ULSD) fuel was replaced by biodiesel. Model calculations predict that reduced EC emissions translate directly into reduced EC concentrations in the atmosphere, but the concentration of secondary particulate matter was not directly affected by this fuel change. Redistribution of secondary particulate matter components to particles emitted from other sources did change the size distribution and therefore deposition rates of those components. Modification of meteorological variables such as water content and temperature influenced secondary particulate matter formation. Simulations with a source-oriented WRF/Chem model (SOWC) for a severe air pollution episode in California that adopted 75% biodiesel blended with ULSD in all non-road diesel engines reduced surface EC concentrations by up to 50% but changed nitrate and total PM2.5 mass concentrations by less than ±5%. These changes in concentrations will have public health benefits but did not significantly affect radiative forcing at the top of the atmosphere. The removal of EC due to the adoption of biodiesel produced larger coatings of secondary particulate matter on other atmospheric particles containing residual EC leading to enhanced absorption associated with those particles. The net effect was a minor change in atmospheric optical properties despite a large change in atmospheric EC concentrations. These results emphasize the importance of considering EC mixing state in climate research.
authors: Department of Civil and Environmental Engineering, University of California at Davis, 1 Shields Ave, Davis, CA 95616, USA.
authors: Hongliang
authors: H
authors: Zhang
authors: Environmental Chemistry and Technology Program, University of Wisconsin-Madison, 660 North Park Street, Madison, WI 53706, USA; Environmental Engineering Department, Pontificia Bolivariana University-Bucaramanga, Km 7 Vía Piedecuesta, Bucaramanga, Colombia.
authors: Kento T
authors: KT
authors: Magara-Gomez
authors: Environmental Chemistry and Technology Program, University of Wisconsin-Madison, 660 North Park Street, Madison, WI 53706, USA.
authors: Michael R
authors: MR
authors: Olson
authors: Environmental Chemistry and Technology Program, University of Wisconsin-Madison, 660 North Park Street, Madison, WI 53706, USA; Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
authors: Tomoaki
authors: T
authors: Okuda
authors: Environmental Chemistry and Technology Program, University of Wisconsin-Madison, 660 North Park Street, Madison, WI 53706, USA; Madison Area Technical College, 3550 Anderson Street, Madison, WI 53704, USA.
authors: Kenneth A
authors: KA
authors: Walz
authors: Environmental Chemistry and Technology Program, University of Wisconsin-Madison, 660 North Park Street, Madison, WI 53706, USA.
authors: James J
authors: JJ
authors: Schauer
authors: Department of Civil and Environmental Engineering, University of California at Davis, 1 Shields Ave, Davis, CA 95616, USA. Electronic address: mjkleeman@ucdavis.edu.
authors: Michael J
authors: MJ
authors: Kleeman
mesh_terms: D000393:Air Pollutants / Q000032:analysis* / Q000592:standards; D000397:Air Pollution / Q000331:legislation & jurisprudence / Q000517:prevention & control / Q000706:statistics & numerical data*; D001272:Atmosphere; D056804:Biofuels; D002140:California; D004784:Environmental Monitoring; D058735:Environmental Policy; D053260:Soot / Q000032:analysis* / Q000592:standards
chemical_list: D000393:Air Pollutants; D056804:Biofuels; D053260:Soot
keywords: Biodiesel; Black carbon; Off-road engines; SOWC