[smyrali]

Hello, I have calculated alkalinity (mg/lt as CaCO3) and salinity (ppt) values and the results showing that there is a negative correlation between them. Is this correlation a general axiom?  How can i prove it? These questions are very significant for my MSc...
Thaks for all the answers!

[Arkcon]

So greater alkalinity is found with lower salinity?  That would seem to be counter to some bodies of water on Earth.  A bit more specificity for your application is needed.

[smyrali]

Yes when salinity values are 0-16 ppt , alkalinity values are 253.21 – 381.12 mg/lt CaCO₃
when salinity values are 28-36 ppt , alkalinity values are 125.32-158.50 mg/lt CaCO₃


There were 6 samples, 2 from the sea on the shoreline, and 4 samples on the beach at different depths.

[smyrali]

are my results strange ? this negative correlation is common to all water bodies?

[Arkcon]

Have you sampled any alkaline lakes, e.g. The Dead Sea, Utah's Great Salt Lake?  Does your application exclude these bodies of water for some reason?  You haven't explicitly said, do you mean marine samples only?  We are to exclude the hypersaline lakes and freshwater bodies?  And estuaries as well?

[smyrali]

Hello again, my samples are marine on the Aegean Sea, Greece where salinity is normal. I also have measured water taken form holes on the beach. These samples were saline,fresh and brackish.

[Arkcon]

Okay, now returning to the original question, you've determined an inverse correlation between salinity and alkalinity in marine samples. 

You've got me excited.  (OK, I'm easily impressed with science topics.)  You want to know if the correlation is significant. 

Well, lets see for starters, what sort of noise (variance) is there in your samples?  I don't see much info on Google, so it's not the most obvious thing in the world, but maybe oceanologists talk about it among themselves all the time.