I have values of total nitrogen (mg/m3) collected in seawater samples, but need to convert them into nitrate (mg/L). I found some information converting these types of values in soils, but I am wondering if anyone could direct me to a good resource that would allow me to use a conversion factor in seawater. Thanks!
NO3-N (mg/L)=Total N * (molecular weigth of NO3 / Molecular Weigth of N) * 0.001
0.001 factor is for converting mg/m3 to mg/L
NO3-N (mg/L)=Total N * (62/14)*0,001
This calculation assumes all of the total N is in NO3 form.
Veli Uygur , "This calculation assumes all of the total N is in NO3 form." Right. But is that a reasonable assumption for sea water samples ?
The nitrate concentration in sea Water is highly site dependent. The concentration in a specific site can also difer at differibg sampling time. The Best way is to directly measure it.
@Veli: Thank you for this. I will have to measure it once there. I have data in total nitrogen from previous years and was not sure if there is a way to extrapolate just the nitrate contribution from existing values.
The best you could do would be to get an average from literature for sea environments or for similar sea environments for the proportion of total N that is nitrate-N.
But I wouldn't state the result in any way stronger than "Perhaps the nitrate concentration might have been X - X", and cite the literature for the proportion. I used to have a textbook on biogeochemistry that had these kinds of values on a global scale.
I'm sure if you look at data from sea environments, nitrate-N and total N are not particularly well correlated. There will be so many dynamics with nitrate, ammonia, and organic N species.
Upshot: I wouldn't even try to report nitrate values for samples where you have only total N. But if you have to, be sure you state the tremendous uncertainty in how you got those values.
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