Environmental Engineering Reference
In-Depth Information
In 2005, non-taxed, red dye diesel fuel throughput for Bay Area refineries was
found to be about 250,000 gal/day. State Board of Equalization tax refund records
indicated that about 20% of clear diesel produced in California is used in off-road
equipment. Assuming all red-dye diesel produced in the Bay Area is used locally,
total off-road diesel consumption was estimated to be about 440,000 gal/day, or
45% of on-road usage, and roughly half the OFFROAD2007 estimate, a finding
similar to that of a fuel-based study at the national level (Kean et al., 2000).
As an additional check of the inventory, we compared ratios of toxic com-
pounds in the inventory with corresponding ratios measured in ambient air.
Elemental carbon estimated via the IMPROVE method was used as a surrogate for
diesel PM in this comparison. The relative mass and risk from various compounds
in the emissions inventory was generally well correlated with ambient concen-
trations. Diesel emissions dominated the risk in both ambient samples and the
emissions inventory, contributing about 75% in the ambient data and 85% in the
inventory, followed by 1,3-butadiene and benzene, each contributing 7-11% in
the ambient data and 3-7% in the inventory. The ambient data show a risk from
carbon tetrachloride of about 4% but the inventory does not; this compound is no
longer produced and measured concentrations reflect global background.
5. Summary
Analyses based on both measurements and emissions estimates suggest that diesel
PM contributes the greatest cancer risk from TAC (between 75% and 85%) in the
Bay Area. Regional maps of TAC emissions show that the highest risk weighted
emissions occur in core urban areas and along major freeways. Such analyses have
helped to inform and focus TAC mitigation measures at the Bay Area Air Quality
Management District.
References
Kean, A.J.; Sawyer, R.F.; Harley, R.A. (2000)
J. Air & Waste Manage. Assoc.
50, 1929-1939.
Martien et al., (2009) Presented at the 30th NATO/SPS International Technical Meeting on Air
Pollution Modelling and its Application, May 18-22.
Reid S.B.; Sullivan D.C.; and Penfold B.M. (2006) Preparation of emission inventories of toxic
air contaminants for the Bay Area. Final report 2 prepared for the Bay Area Air Quality
Management District, San Francisco, CA, by Sonoma Technology, Inc., Petaluma, CA, STI-
906020.07-2771-FR2, July.
