The composition of ambient particulate matter (PM) and its sources were investigated at the Salton Sea, a shrinking saline lake in California. To investigate the influence of playa exposure on PM composition, PM samples were collected during two seasons and at two sites around the Salton Sea. To characterize source composition, soil samples were collected from local playa and desert surfaces. PM and soil samples were analyzed for 15 elements using mass spectrometry and X-ray diffraction. The contribution of sources to PM mass and composition was investigated using Al-referenced enrichment factors (EFs) and source factors resolved from positive matrix factorization (PMF). Playa soils were found to be significantly enriched in Ca, Na, and Se relative to desert soils. PMF analysis resolved the PM10 data with four source factors, identified as Playa-like, Desert-like, Ca-rich, and Se. Playa-like and desert-like sources were estimated to contribute to a daily average of 8.9% and 45% of PM10 mass, respectively. Additionally, playa sources were estimated to contribute to 38–68% of PM10 Na. PM10 Se concentrations showed strong seasonal variations, suggesting a seasonal cycle of Se volatilization and recondensation. These results support the importance of playas as a source of PM mass and a controlling factor of PM composition.

•EFs of black carbon and extinction from light-duty gasoline vehicles were measured.•WG-GDI engine exhibited the highest EFs regardless of the driving cycle.•PFI engine exhibited higher EFs compared to the SG-GDI engine during the US06 cycle.•Cold-start EFs were highest for the WG-GDI.•FTP (US06) values of SSA for WG-GDI were lower than (comparable to) PFI or SG-GDI.Aerosol extinction coefficient (βext) and black carbon (BC) were measured from three light-duty gasoline vehicles (LDGV), including two gasoline direct injection (spray-guided and wall-guided GDI, SG-GDI and WG-GDI, respectively) and a conventional port-fuel injection vehicle (PFI), over the Federal Test Procedure (FTP) and Supplemental FTP (US06) test cycles. Emission factors (EF) of BC and βext in addition to aerosol single scattering albedo (SSA) were determined for different phases or segments of the drive cycles. WG-GDI showed the highest EFBC (13 mg BC/kg fuel and 2.5 mg BC/kg fuel) and EFext (0.1 m2/kg fuel and 0.018 m2/kg fuel) during both FTP and US06 cycles, respectively. EFBC and EFext for the GDI vehicles during cold-start (P1) of the FTP cycle were 7–60 times higher than the PFI vehicle. EFBC and EFext from GDI (PFI) vehicles were lower (higher) on the more aggressive US06 cycle compared to the FTP cycle. During the FTP cycle, a significantly lower SSA was observed for WG-GDI (0.2) while higher SSA values were observed for all vehicles during the US06 cycle (0.28–0.49).Download high-res image (177KB)Download full-size image