Re: Explain these standards please - urgent

[ttweed@wildrockies.org (Tony Tweedale)]

(I prepared this before seeing marco k's succint reply, but I'll post it
anyway, as it adds a bit more)...
--

if the N stands for "normalized" (e.g. to 7% oxygen), then it would be
ng/m3, a common unit for dioxin stack levels.  Very roughly ppq (assuming a
g of H2O is one milliter)?  But strictly speaking, ng/m3 is a weight/volume
unit, so it's not directly convertable to ppq (you have to figure the
respective atomic weights of the numerator & denominator--ie the pollutant
& the gas it's carried in).  I've forgotten what the purpose & significance
of normalizing air emissions concentrations is...obviously the % of oxygen
changes the volume of a given number of gaseous molecules., but..
---

>5) on dioxins, why does it say ng/Nm3? shouldn't it be per cubic meter, not
>cubic nanometer?  Perhaps the N is not nano, since n is usually nano; per
>cubic meter sounds good to me; but check the
>number to see if nanograms per cubic meter is what is meant. One ppm would
>be one gram per cubic meter I believe.  A billionth
>ppm would be one nanogram per cubic meter; seems like the measurement
>should be parts per trillion or quadrillion, not million.
>It would be a fearsome thing to have 70 ppms of dioxins, I think, although
>far more exists in some superfund sites;
>and most would say 70 ppt is way too high for human safety, I believe;
>maybe parts per quadrillion would be about right;
>that would be grams per million cubic meters according to my rough
>calculations, but maybe someone else can tackle this one.