Hi Chris,
I applaud your proposed holistic approach that will cover both modelling and measurement of crude oil contamination. This will obviously take time and so you're proposing a generic Name with the contaminant specified in the long name as a stop-gap. This causes me some concern from an interoperability perspective because it could easily leak out of the oil contamination community into pesticides, metals and so on and there is so much potential for synonyms and even misspellings with plain language descriptions of these. Others in CF may also have views on establishing this as a precedent.
Personally, I would prefer an approach of having a Name specifically targetted at the SeaOWL measurements with the possibility of later replacement through deprecation if it doesn't fit your holistic solution. However, if others share your view and thee are no other dissenters then I wouldn't block your suggestion.
Cheers, Roy.
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From: CF-metadata <cf-metadata-bounces at cgd.ucar.edu> on behalf of Chris Barker <chris.barker at noaa.gov>
Sent: 30 June 2016 19:57
To: Ute Br?nner
Cc: cf-metadata at cgd.ucar.edu; CJ Beegle-Krause; mikegodino at yahoo.com; Tor Nordam; Petter R?nningen; J?rgen Skancke
Subject: Re: [CF-metadata] New standard name for mass_fraction_of_petroleum_in_sea_water
Folks,
A few thoughts here:
As Ute made reference, some of us in the oil spill modeling community have had previous discussions about netcdf standards for oil spills information -- in that case, mostly model results, but there is a lot of overlap with field measurements as well.
So I suggest that as a community we address the whole pile, rather than adding a single new standard name.
I offer up this gitHub repo as a central point for discussion:
https://github.com/NOAA-ORR-ERD/nc_particles
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https://avatars1.githubusercontent.com/u/4809476?v=3&s=400]<
https://github.com/NOAA-ORR-ERD/nc_particles>
GitHub - NOAA-ORR-ERD/nc_particles: Project for ...<
https://github.com/NOAA-ORR-ERD/nc_particles>
github.com
nc_particles - Project for Documentationand Examples of a standard for a netcdf format for Particle Tracking Model results
or we could make a new one for standard names if we like.
In the meantime:
I would like to propose to use a standard name like "mass_fraction_of_contaminant_in_sea_water"
This is a fine idea -- to have _something_ that covers a lot of use cases in the meantime. exactly what the contaminant is, and how it was measured can be in the long name or other meta-data.
Roy wrote:
There is a parameter 'total petroleum hydrocarbons' (TPH) defined as 'A mixture comprising all substances comprising totally of carbon and hydrogen that may be extracted from a sample using an organic solvent. These are presumed sourced from crude oil.'.
having one for TPH is a fine idea as well -- this is a very commonly used convention. The "presumed sourced from cure oil" is a bit odd, but I suppose, correct, if "sourced" in interpreted broadly :-)
I also mention that in my experience of these measurements contamination of water samples is reported in units of micrograms per litre, i.e. mass concentration rather than mass fraction.
yeah, this is a convention that has always bugged me -- as far as I can tell, everyone considers the two equivalent -- i.e. one milligram per liter IS one part per million, and they are used interchangeably. I personally call this "concentration in water", and assume 1kg/liter for the water) -- I don't know that there is a way to express that equivalence in CF or udunits, so I would suggest that the "official" unit be mass fraction -- it's more precise and clearly defined.
I agree that petroleum_hydrocarbons is more specific and therefore preferable.
Is it possible to omit "total", or does it have a specific meaning too and
therefore convey some extra information?
I've always seen "total" in there, usually to distinguish from more specific measurements that capture particular classes of compounds, like PAHs. As "TPH" is in really common use, I suggest we keep it.
https://www3.epa.gov/region1/eco/uep/tph.html
Having read through the SeaOWL specification provided by Mike's link, I see it is something totally new making a combination of fluorescence and backscatter measurements at different wavelengths and using the results in a calibration algorithm to produce measurements of an analyte that WETLabs/SeaBird describe as 'crude oil'. This is NOT the same thing as TPH (a wet chemical measurement), although in most environments the two will be linearly correlated. I therefore now think that it would be best to use the terminology of the instrument manufacturer: i.e. 'crude_oil'.
The use of fluorescence to measure oil in water is fraught with difficulty, and lacking in precision -- it looks like WETLabs has done an admirable job (speaking only from their literature, and a VERY limited understanding of the science) of developing a tool for that purpose (rather than simply using a CDOM tool and expecting it to work), but I seriously doubt that they can distinguish between "crude oil" and petroleum-derived hydrocarbons in general. And I doubt they'd even want to.
For instance, if a refined product is spilled, that is not crude oil, but it is PH, and I'm sure their instrument would measure it.
Also, as Ute pointed out, once released into the environment, crude oil weathers and changes, so it's no longer "crude" strictly speaking.
I suspect the term "crude oil" is being used for marketing, and "TPH" is what they are really trying to measure. I'm sure what they are really trying to do is make the point that their instrument measures hydrocarbons (maybe petroleum derived, rather than other sources of fluorescence.
I can run this by folks in our group that understand all this better than I, if there is still uncertainty
--
Christopher Barker, Ph.D.
Oceanographer
Emergency Response Division
NOAA/NOS/OR&R (206) 526-6959 voice
7600 Sand Point Way NE (206) 526-6329 fax
Seattle, WA 98115 (206) 526-6317 main reception
Chris.Barker at noaa.gov<mailto:Chris.Barker at noaa.gov>
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