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Figures 1-6 (Click on individual panels to enlarge)
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The SMS [Carlson et al., 1988]
consists of a partially-submerged, rotating glass cylinder
supported by a small catamaran. The cylinder collects a thin
layer of water (~40-60 micron thickness) by viscous retention.
The theoretical basis for the sampling mechanism has been
described by Levich [1962] and verified experimentally by
Cinbis [1992]. A flow stream duplexer selects either the microlayer
or subsurface line from the SMS and routes the water to both
the extraction system and the fluorometry package. The SCIMS
extraction system (Figures 1-6) employs a collection of digitally-controlled
peristaltic and syringe pumps, multiport switching valves,
and a three-axis positioner (Figure 1). Two syringe pumps
are used in a push-pull arrangement to draw and filter microlayer
water and to force it through a Michrom BioResources (M-B)
solid phase sorption macrotrap (polystyrene divinylbenzene,
50 microliter bed volume (Figure 2)). The M-B macrotrap is
then alternately purged and rinsed with high purity nitrogen
and distilled water using two additional syringe pumps before
elution of adsorbed surfactants from the trap with methanol
from a fifth pump. Control of the extraction cycle is realized
using a laptop PC with two RS-485 serial multidrop lines for
the pumps, 3-axis arm and multiport valves (Figure 3). A National
Instruments DAQCard-1200 multifunction card drives the servo
amplifier for the skimmer motor and provides digital I/O for
the flow duplexer and power relays. The physical layout is
shown in Figure 4 and Figure 5.
A full-featured software package
with graphical user interface and display has been developed
for the WIN32 environment (Figure 6). The software package integrates
three separate applications: the SCIMS control interface,
the fluorometry data acquisition interface, and a set of test
bench tools for development/ modification of the SCIMS extraction
sequence. The software interface capabilities include:  Control
dialogs for all subsystems 
Status displays/system monitoring
Single vial and auto-fill (micro 100 vial) modes
CDOM fluorescence acquisition/display
Date/time stamping/annotation
Error handling
Fully remote operation via WLAN. |
