Minghao Han | Chemical and Environmental Engineering PhD Candidate

Time: 10:00 AM

Date: Friday, July 31

Location: Hybrid; CE-CERT RM 105 and Zoom (ID: 97011421476 Passcode: 616685)

Title: Atmospheric Measurement Systems for Characterizing Emissions and Secondary Aerosol Formation

Abstract:  Secondary organic aerosol (SOA), a major component of atmospheric fine particulate matter, affects air quality and climate. This dissertation examines its formation from ambient precursor mixtures and tire emissions and describes a drone-based sampler for ship plumes. During the Southern California Investigation of Low Cloud and Land Aerosol campaign, an OFR with controlled temperature and relative humidity sampled 47 cloud-free legs over the Southern California Bight. Mean ambient OA was 1.455 µg m⁻³ in free-tropospheric (FT) air and 0.702 µg m⁻³ in boundary-layer (BL) air; mean OFR-derived OA was 2.610 and 1.973 µg m⁻³, respectively. Ambient and OFR-derived OA showed a modest association (Spearman ρ = 0.33). Within flights, similar ambient OA accompanied different OFR-derived OA and vice versa; thus, ambient OA did not reliably indicate OA formed from sampled gases. Effective SOA emission rates from 152 whole tires were measured at 20–90 °C. Rates increased by several orders of magnitude with temperature and spanned more than two orders of magnitude among used tires at 50 °C. Scaling these rates to externally exposed tire surfaces of light-duty vehicles in the South Coast Air Basin yielded annual-average estimates of 83.1 and 258.5 kg day⁻¹. The two values reflect separate daytime parked-tire temperature assignments, not confidence bounds or ambient SOA burden. Parked tires dominated both estimates. A variable-volume drone-based sampler was fabricated to collect ship-plume air near ambient pressure for postflight analysis. Components were tested separately; sample recovery and flight performance of the complete sampler remain untested.