Dr. Maurice
I don't think the brown material is a "biofilm" since the time required to
run the water through cotton wool is too short. I think that what you have
is interference by lignins or other types of bio-polymers. Try using a
filter, like Millipore, that does not adsorb your marker prior to the cotton
wool. You could also use a molecular seive that would let you marker pass
through and retard the interfering compounds. Just a thought.
> I am a hydrogeologist using an optical brightnener for groundwater
> tracing. We inject the tracer into a borehole/ soakaway/ sinking
> stream. We then use small balls of cotton wool (approx. 5 cm
> diameter) to detect the optical brightener in springs, boreholes and
> rivers, to prove groundwater connections. I have found that in the
> river we need to sample, the cotton wool becomes coated in a brown
> slime, presumably a form of biofilm, preventing the absorbtion of the
> fluorescent tracer. I have tried covering the cotton wool in netting,
> cloth, plastic mesh and wire mesh, but the cotton wool still becomes
> coated in the biofilm. I know absolutely nothing about biofilms but
> wonder if there is any method of preventing the cotton wool becoming
> coated in biofilm, yet still allowing the water to flow through the
> cotton wool and the optical brightener to be absorbed. Perhaps there
> is some treatment I could apply to the cotton wool? Any advice would
> be greatly appreciated.
>
> Louise Maurice
--
DeWayne Townsend, Ph.D.
d-town at maroon.tc.umn.edu
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