Real-time measurements of the chemical composition of size-resolved particles during a Santa Ana wind episode, California USA

Size-resolved particle composition, mass and number concentrations, aerosol scattering coefficients, and prevailing meteorological conditions were measured at the Ellen Browning Scripps Memorial Pier located in La Jolla, California on 15 December 1998. Aerosol particles were sampled using a field transportable aerosol time-of-flight mass spectrometer, allowing for the continuous detection and characterization of single particles from a polydisperse sample. An extensive and rapid change in the chemical composition of aerosol particles with aerodynamic diameters between 1.0 and 2.5 μm has been observed during the onset of a Santa Ana Winds condition. Coincident with the observed change in meteorological conditions, a substantial decrease in sea salt particles corresponds to an increase in dust and carbon-containing particles. This paper examines observations of the rapid changes occurring in the chemical composition of single aerosol particles and demonstrates the new types of information that can be obtained by measuring single particle size and composition with high temporal resolution.