photo-oxidation of DOP

[kaskiles]

Hi,

I noticed this abstract:
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VC2-44480FG-8&_user=10&_coverDate=10%2F31%2F2001&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1276952130&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=ca363db9eadc5209667e3b0fa1150340

Anyway, it's talking about using a 'low power lamp' to oxidize or maybe mineralize organic phosphorus. Does this mean a light source could be used to convert dissolved organic phosphorus to phosphate, that we could then measure on our hobby test kits?

I did notice that sea salt constituents interfered with the photo-oxidation, but were able to be overcome by dilution of the sample. Would this sort of dilution ruin the hobby grade phosphate test kit accuracy (assuming the DOP is going to PO4...)?

Finally, I assume this photo-oxidation would not act upon the P in bacterioplankton or phytoplankton... If not, would including the water borne suspended fraction just involve letting the sample sit long enough for bacteria and algae to die (or maybe heating it) prior to the light show?

Thanks!

[Randy Holmes-Farley]

I can't pull up the whole article, but I expect it is a UV lamp, not a visible light source.

If you really want to measure organic P, just get the Hach test kit for total phosphorus. It is more tedious than a regular phosphate kit, and I'm not sure such data would be useful to reefers, but it certainly works. :)

What would you do with the data? Do you believe that organic P is something you want to control, and if so, what level would you say is desirable?

Bear in mind that a lot of the organic P may be in things like living bacteria. Bacteria will not necessarily settle out without a centrifuge, but could be filtered out.

[kaskiles]

I'm assuming there is an equilibrium in my system between P in:
PO4 (1) - DOP (2) - suspended/particle/plankton P (3) - refractory dissolved organic P (4)

and I would assume that depending on my setup, the system could run higher/lower in one of the first 3. So by dosing organic carbon, I may measure lower PO4, but some of my measurement difference might just be because it's tied up in 2-4 and not because I've exported it via skimming or GAC. By not providing any surface media, maybe 3 would run higher than normal, etc.

Also, it would be neat to be able to determine the amount in 3 vs the total, to possibly indicate how much P can be physically removed through physical filtration (membrane/sock/floss).

Finally, looking at 2-4 levels with no skimmer and only GAC vs. no GAC and only skimmer would be usful, particularly if I could distinguish between 2 and 3...

I believe the Hach total phosphate uses the persulfate with UV and/or autoclave temperatures. I was just wondering if it was more simple...

[Boomer]

Randy

I posted an answer but it seems I forgot to hit the submit button :(



You are correct it is a low output UV lamp for ozone generation.

A low-power lamp was used for a compact, easy-to-handle and low-ozone-producing manifold.

There are 3 UV lamp ranges

1. Ozone production
2. Ozone destruction
3. UV sterilizing

Kask

Have you seen Ken Feldman studies on TOC and skimmers. They may help you allot. On another note, it is just so much easier to use the HACH PO-24 as Randy suggested, which measures all forms of phosphates .etc, Total, Ortho and Meta. Org = T - (ortho + meta). There is no UV but does require filtering and heating and all accessories are in the kit for that.

PO-24
http://www.hach.com/hc/search.product.details.invoker/PackagingCode=225001/NewLinkLabel=Phosphate,+Total+Ortho-&frasl%3BMeta-,+Test+Kit,+Model+PO-24,+Color+Disc