Development of a Buoy-Mounted Sampler and Sensor for the Elemental Analysis of Aerosols Book uri icon

abstract

  • Under project SEA-AER we have built an autonomous aerosol sampler/sensor that is capable of being deployed from buoys or at remote sites on land. Aerosols are collected on filters and x-ray fluorescence (XRF) spectrometry is used to make a quantitative and non-destructive measurement of the elemental concentrations. Fe, Ca, Si, K and S can be analyzed in real time on a set of samples collected over periods of days to weeks to months. Fe and Si are indicators of mineral dust, S has both natural and anthropogenic sources and Ca and K have mineral and seasalt sources. A Jordan Valley A.R. Inc. # EX-310 XRF spectrometer has been modified and coupled to an aerosol sampler. The XRF runs off batteries and contains a Rh x-ray tube and an energy dispersive detector. A 24 place carrousel-type holder allows us to collect and analyze about 20 aerosol samples as well as measure blanks, elemental standards and a XRF calibration filter over the course of the time-series. Samples can be returned to the laboratory for other analyses. The system also contains a special air inlet [which closes when there is rain and/or when sea spray is produced by high winds], an air pump (15 lpm) and flow meters and a suite of meteorological sensors. Computer-based controllers operate the whole instrument by linking the functions of the different modules. We have the ability, through a two-way satellite communication system, to remotely control the operating parameters of the instrument and to relay the xrf data back to the laboratory. In practice, sample holders, containing 25 mm filters, are loaded into the carrousel. One sample holder is then moved under and pushed tightly against the air inlet by means of a motor. Air is pulled through the filter for a set period of time. The aerosol-containing filter is then moved under and pushed up against the XRF spectrometer for a 10 min. elemental analysis. This process can be repeated using the same filter or a new filter until the time series is completed. Our instrument has not yet been tested on a buoy. See www.whoi.edu/science/MCG/aerosols/newbuoy/html for photographs. Funding is by the Ocean Technology section of NSF.

publication date

  • January 2000