Understanding Nitrate Concentrations: Are These Rural Wells Safe for Drinking?

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Nitrate concentrations in drinking water exceeding 44.3 mg NO3-/L pose health risks, particularly for infants. Three rural wells reported concentrations of 0.01 mg NO3- N/L, 1.3 mg NO3- N/L, and 20.0 mg NO3- N/L, all of which are below the threshold when converted correctly. The discussion highlights confusion over the units NO3- N/L and NO3-/L, clarifying that NO3- N/L refers specifically to nitrogen from nitrate, while NO3-/L includes the mass of nitrate itself. Participants emphasize the need for proper conversions to assess safety levels accurately, noting that 1 mole of NO3- corresponds to 1 mole of nitrogen but has different weights. Ultimately, the values from the wells do not exceed the safety limit when calculated correctly.
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The question:

Nitrate concentrations exceeding 44.3 mg NO3-/L are a concern in drinking water due to the infant disease, methemoglobinemia.

Nitrate concentrations near three rural wells were reported as 0.01 mg NO3- N/L, 1.3 mg NO3- N/L, and 20.0mg NO3- N/L. Do any of these three wells exceed the 44.3 ppm level?

The problem:

I have no problem with conversions, it's just the units in this case. I've asked peers about the NO3- N/L unit and they said the N stands for nitrogen. If this is so, I don't know what the implications are. Whats the difference between the NO3-/L and NO3- N/L unit?
 
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sdoug041 said:
0.01 mg NO3- N/L

Doesn't make sense to me.

I can easily imagine NO3- reported as 0.01 mg N/L, but the way you have it written it is - to say the least - strange.
 
sdoug041 said:
I have no problem with conversions, it's just the units in this case. I've asked peers about the NO3- N/L unit and they said the N stands for nitrogen. If this is so, I don't know what the implications are. Whats the difference between the NO3-/L and NO3- N/L unit?

Hmm, I've https://www.physicsforums.com/showpost.php?p=2162757&postcount=2"..

But to elaborate a bit more; you have the whole nitrogen cycle, so nitrogen in water (with living stuff in it) is being converted between nitrate, nitrite, ammonia, etc.
Therefore they distinguish between "N/L" nitrogen per liter (the mass of N from all compounds) "NO3- N/L", nitrate nitrogen per liter (just the nitrate nitrogen) and nitrate/L (the mass of nitrate, including oxygen).
 
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But for every mole of NO3-, there is 1 mole of N... So is there no conversions to be made here? I can just simply look at the values and if they are less than 44.3, they don't exceed the limit?
 
sdoug041 said:
So is there no conversions to be made here?

ppm is usually weight/weight, so you need some conversion.
 
But a mg/L is a ppm, at least concerning aqueous solutions.

there is 10^6 mg of water in a litre.

I think I'm still missing something though. It can't be as easy as just looking at the given values...
 
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sdoug041 said:
But for every mole of NO3-, there is 1 mole of N... So is there no conversions to be made here?

Your units are in mg/L, not mol/L. One mole of N doesn't weigh the same as 1 mole of NO3-
 
Ah that is a good point, it's starting to become a little clearer.

So:

(0.01 mg NO3- N/L) x (1 mol N / 14000 mg N) x (1 mol NO3- / 1 mol N) x (62000 mg NO3- / 1 mol NO3-)

= 0.04 mg NO3-/L

Am I understanding this concept correctly?
 
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