title: Size distribution, sources, and seasonality of suspended particles in southern California marine bathing waters.
abstract: In this paper we define seasonal and along-shore variations in suspended particle size distributions (PSDs) at two marine bathing beaches in southern California, using a low-angle light scattering instrument (LISST). Empirical Orthogonal Function (EOF) analysis of the LISST data set (n = 55 651) identified three particle size modes that collectively account for > 90% of the variance in the de-meaned PSD data at six sites along the shoreline at Huntington Beach and Newport Beach: a dinoflagellate mode, a large particle mode, and a small particle mode. These three modes exhibit distinct seasonal patterns, and along-shore distributions, reflecting both the sources of particles and environmental factors that trigger their occurrence. Comparison of volume-based PSDs generated from the LISST and from image analysis of optical micrographs indicates that the LISST performs well when measuring the size distribution of particles associated with dinoflagellate blooms. However, LISST measurements on stormwater-impacted samples consistently yield a rising tail at small particle sizes that may be an artifact arising from the non-spherical nature of inorganic particles in terrestrial runoff. The results presented here demonstrate that PSDs measured by light scattering instruments such as the LISST represent a new data resource for assessing water quality, and managing human health risk, at marine bathing beaches.
authors.affiliation: Department of Chemical Engineering and Materials Science, Henry Samueli School of Engineering, University of California, Irvine, California 92697, USA.
authors.forename: Jong Ho
authors.initials: JH
authors.lastname: Ahn
authors.forename: Stanley B
authors.initials: SB
authors.lastname: Grant
mesh_terms: D000818:Animals; D001494:Baths; D004784:Environmental Monitoring; D006801:Humans; D010316:Particle Size; D011634:Public Health; D011786:Quality Control; D018570:Risk Assessment; D012621:Seasons; D012623:Seawater / Q000032:analysis*; D013550:Swimming; D014872:Water Movements; D014873:Water Pollutants / Q000032:analysis* / Q000633:toxicity
chemical_list: D014873:Water Pollutants