10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Simultaneous Measurements of Lung Deposited Surface Area, Particle Number Concentration, Particle Size, and Black Carbon Concentration to Characterize Near-roadway and Biomass Source Emissions
MARILYN WURTH, Brian P. Frank, Gil H. LaDuke, Oliver Rattigan, H. Dirk Felton, Jake Lindberg, Nicole Vitillo, Patricia Fritz, Thomas Wainman, New York State Dept. of Environmental Conservation
Abstract Number: 1504 Working Group: Instrumentation
Abstract There is currently an uncertainty about the appropriate metric to use for characterizing ambient ultrafine particles (UFP) and whether such metrics should be source specific. Some researchers have suggested particle surface area – including lung deposited surface area (LDSA) - as a more relevant exposure metric to consider when evaluating health risk because UFP have such a large surface area per unit mass. Studies report a range of particle number concentration (PNC) and LDSA measurements in different environments including urban areas impacted by traffic and residential areas with biomass combustion sources. Differences in source particle size distributions are expected to affect LDSA measurements directly since aerodynamic particle diameter is a key determinant of respiratory tract deposition. More research is needed to investigate how LDSA relates to both particle size and PNC to better understand how UFP and LDSA change spatially and temporally.
This study utilizes portable instruments to obtain simultaneous measurements of multiple characteristics of UFP in different ambient environments to investigate the use of LDSA as an exposure metric. Collocated and simultaneous measurements were conducted for LDSA (Partector, Naneos, Inc.), PNC (CPC 3007, TSI, Inc.), geometric mean particle diameter (NanoScan, TSI, Inc), and black carbon concentration (microAeth MA300, Aeth Labs). Measurements were conducted in three ambient urban environments impacted by traffic emissions: proximate roadway (<5m to roadway), near roadway (<100 m to roadway), and urban background. The LDSA/PNC ratio was evaluated as a potential exposure metric that conceptually represents the percentage of an exposure to a given particle number concentration that is deposited in the lungs; it is also loosely correlated to particle diameter. The results show that both LDSA/PNC and particle diameter in these environments have a nonlinear relationship with PNC. These relationships can be further divided into 3 distinct regimes which are a function of particle diameter, each with a different correlation to PNC. These results have implications both for understanding the differences and similarities of UFP behavior in proximate and near-roadway environments, and in evaluating their potential health impacts. A similar evaluation is performed using a parallel set of simultaneous source measurements from a biomass combustion source in order to investigate the impact of source aerosol on these characterization measurements. A combined metric assessment may help define source profiles and their relative contributions, explain relationships between measurements, and identify which metrics are most useful to evaluate air quality.