Long-term observations of suspended particulate matter (SPM), by particle size class, are important to characterize the dynamics of estuaries, yet are challenging to achieve. Towards this end, we have recently integrated an in-situ laser diffraction sensor, the LISST-100, in the SATURN observation network for the Columbia River coastal margin. The SATURN network measures physical and biogeochemical variables across the river-to-continental shelf continuum. Sediment concentrations were already measured at multiple SATURN stations, but without of particle size resolution. The LISST-100 was deployed in SATURN-03, a lower estuary station designed for multi-level sampling, via pumping ports, with a single instrumentation package installed on land. This set-up poses substantial challenges, including the integrity of particle sizes during the pumping process. Here, we will report on the deployment strategy, on quality control procedures, and on early results. Our early focus is on (a) the spring-neap variability of sediment concentrations and of size distributions, and associated implications for the contrasting intensity of the ETM in neaps and springs; (b) the response of the vertical distribution of the sediments over the water column, to varying tides and river discharges; and (c) the correlation of sediments with density structure and optical water properties. Prior deployments of LISST-100 sensors in the freshwater side of the Columbia River, by other researchers, provided useful guidance for our deployments. This work is supported by the NSF cooperative agreement OCE-0424602. SATURN observations and simulations are integral to the Northwest Association of Networked Ocean Observing Systems (NANOOS).
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