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Hello,

I am currently working on putting together a methodology for a monitoring programme of a brackish lagoon on the coast of Samos (a greek island close to Turkey). It is not a deep lagoon (about 1m at the most) the lagoon is cut off from the sea by a road though there is a small channel linking it to the sea- but we believe that not much if any sea water enters here. The site used to be home to a salt extraction factory, which may have contributed to the salinity of the ambient water.

My current problem is how to take water samples that are representative of the water body in terms of its salinity. Any advice you could give on this would be much appreciated. Questions:

- Can samples be taken from around the edge of lagoon or would they need to be taken in the middle to be representative?
- Would vertical profiles of salinity need to be taken i.e.will the lagoon be stratified or will there be a gradient of salinity from the top of the water column down. If so then a sample from the surface may not be representative.
- Could we use a thief type sampler to sample different depths of the water- if we are using waders (would wading mix the water column?)

Any help is very much appreciated! Feel free to give any advice even if it not a direct answer to one of the questions above. Thank you.

Alex
Volunteer at Archipelagos Marine Institute

Answer
It is not uncommon to have a profile of salinity differences across a body of water. So please plan on taking a couple of transits across the pond and taking samples at least at the midpoints, but even better if you can, depending upon the size of the lagoon, take 4-5 samples on each transit.
The water in the lagoon will likely be stratified. Omega instruments, for one, makes a good instrument which is not too expensive and will measure salinity in the range from 0.1 to 10%.
http://www.omega.com/googlebase/product.html?pn=CDH45&gclid=CjwKEAiAi52mBRDkq5bX
Yes, you will probably have vertical and horizontal salinity profiles, and unusual discontinuities in the vicinity of the outlet or inlet.
I would not recommend a thief. IF you are looking for gross analyses of concentration, then the thief is fine, but it will not allow you to develop a profile because when you transfer the contents to a flask for analyses, the profile will be lost.
Wading will mix the water column somewhat. I'd rather see you use a log platform or a platform created out of some 55 gallon drums and towed from one site to the other very slowly. Check with your professor or sponsoring agency to see if they will pay for the purchase of the Omega measurement device. It's less than 100 Eu. So it will be economical and as accurate as any device.  Just remember to take distilled water with you on your float and decontaminate the instrument before each measurement profile. I would also have the measurements made in front of the floating platform because the pulling of the platform will disturb the profile.
Good luck and let me know if you need a hand plotting the information, as I have some suggestions there as well.
Dave Russell
DLR@mindspring.com

Environmental Science

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David L. Russell, PE

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I`m a Chemical,Civil and Environmental Engineer and have a number of projects in all phases of the environment. I have worked in the chemical industry and am active in professional societies, and am currently on an industrial wastes committee for the Water Environment Federation, and have taught courses in remediation in the US and abroad. I have written one book on Remediation of petroleum Contaminated Sites, and have a second book on PRACTICAL WASTEWATER TREATMENT to be published by John Wiley in September, 2006. I've also written over 30 articles on various elements of environmental problems and cleanup. Most Recently, I have addressed a NATO Scientific and Techical Conference on Ecoterrorism, and have worked with the same group on remediation of sites contaminated with Chemical Warfare Agent materials and othe materials as well. . I can answer q`s about Chemical and Environmental Engineering, land development, air pollution, water pollution, soil and water cleanup, combustion, international environmental problems, industrial processes chemical processes. Civil and Environmental and Chemical Engineering. Overall, I have over 35 years of experience in this area. Note: I do not answer homework questions

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I love work in the third world and developing areas because it is challenging and one can get a sense of accomplishment.

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