Thursday, August 20, 2009

The Theory, the pitfalls, the execution, intial results

I now have enough samples with some that do not fit the mold to understand what I am seeing.
The Theory - was that pH would allow me to tell if fresh water (and thus water with bacteria) was influencing the beaches.

The pitfalls - Although it is a determined fact that the pH of fresh water in this area is more acidic than the Estuary of Long Island Sound, there are other factors which will affect the reading.
Temperature will drive CO2 out of the water and you will get a more basic reading.
Fresh water does indeed "float" on top of the saltier and denser Long Island Sound Water.
There maybe still another temperature defendant reaction which makes the water more basic as the temperature climbs.

Because of these variables, I have also been measuring chlorides (simple way to measure salinity) and there is a good correlation between the intrusion of fresh water and pH.

Measurements were conducted of beach water (3 feet deep), shellfish waters (up to 20 feet deep) and spots in the Sound itself (up to 80 feet deep).
Outfalls from treatment plants and rivers were also measured.
This is a minimum of 20 samples a week.
All samples are taken at about 1 foot depth.
Samples were measured for pH and chlorides along with the normal bacteria densities I would perform.
Duplicate samples were used to determine validity of samples and testing and that is where the first surprise occurred. On one sample set. there was no duplication between either chloride of pH.
Since we also maintain a log of rain events and weather conditions, we could see that a 0.2" rain the night before had not mixed yet.
Tides are known and added in to the mix.
pH and chloride levels matched with information we already had deduced on tidal currents in 2 places.

Initial results - What I believe is this is an excellent method to determine flow and current in the shoreline.
Since the flows in the shoreline is difficult at best this provided a tool to assist determining this for different tide levels.
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