AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Onshore Measurements of Emissions from In-Use Tugboats in Southern California
HANNAH SCHLAERTH, Joseph Ko, Rebecca Sugrue, Chelsea V. Preble, Thomas W. Kirchstetter, George Ban-Weiss, University of Southern California
Abstract Number: 905 Working Group: Urban Aerosols
Abstract Black carbon (BC) emitted from diesel fuel combustion contributes significantly to total particulate matter (PM) emissions that impact air quality and human health. As on-road sources of PM decline due to the wide adoption of emissions control technologies on diesel trucks, understanding off-road emissions sources is becoming more important to further reduce total PM emissions. Tugboats spend most of their operational time near the coast maneuvering large vessels in and out of berth, making them important contributors to near-shore air pollution. However, few studies have measured emission rates from this source-type, and none have successfully investigated how operational parameters affect their emissions. Measurements of emission rates from tugboats are needed to improve and update official governmental emissions inventories for marine vessels, especially since the few measurements that have been made suggest high vessel-to-vessel emissions variability.
Emissions from in-use tugboats were measured from shore as vessels passed by a pier in the Port of Long Beach in Southern California using the plume capture method. BC concentrations were measured using a single particle soot photometer and a custom-built aerosol black carbon detector. Particle number, PM2.5, and CO2 concentrations were measured, respectively, using a model 3007 TSI Condensation Particle Counter, a handheld DustTrak DRX, and a Li-Cor 840a. Fuel-based emission factors were calculated by carbon balance for the three operating modes observed: cruising against current, cruising with current, and towing vessels. Observed emissions variability within the fleet was analyzed by vessel dimensions, build years, and engine power when Automatic Identification System data was available. Preliminary results suggest that BC emission factors from measured tug boats ranged from near-zero to ~1 g/kg, with a mean (± standard deviation) BC emission factor of 0.52 ± 0.37 g/kg. This study offers unique insight into the emission rates of the Southern California tugboat fleet because of the large sample size of unique vessels and repeated observations for vessels under multiple operating conditions.