Photochemical combustion of organic matter in sea water, for nitrogen, phosphorus and carbon determination

Abstract

AND SUSAN TIBBITTSThe Plymouth Laboratory (Text-figs. 1 and 2) A photochemical reactor, using a medium power mercury arc lamp for oxidation of organic matter in sea water, is described. The decomposition of some known compounds in distilled water and in sea water, using a 380 W lamp, was followed. First order kinetics with rate constants in the range o-2-4'0 h~x were observed. All the nitrogen compounds tested, including urea and some of its derivatives, were oxidized quantitatively. Breakdown of phosphorus compounds was rapid, but polyphosphate esters yielded polyphosphate ion which was only slowly hydrolysed to reactive orthophosphate. If polyphosphate is to be determined, hydrolysis by heating with acid should follow the irradiation. Some samples of English Channel water contained 0-02-O-05 fig-axom P/l. as organic polyphosphate.A technique is described for measuring oxygen consumption during irradiation. It provides a method for measuring total biological oxygen demand or an empirical carbon determination.The decomposition of naturally occurring organic compounds in sea water did not follow first-order reaction kinetics and rate constants declined to about onefifth of their initial values as the reaction progressed. The times required for 98 % oxidation of carbon, nitrogen and phosphorus compounds in sea water were respectively n , 12 and 5 h.Organic nitrogen determinations from some positions in the English Channel are given in graphical form. The fall in the range 2-9 (mean 51) /tg-atom N/l., with little spatial or seasonal variation. There is nearly as much organic as inorganic nitrogen present in these waters.

Fluvial Fluxes of Water, Suspended Particulate Matter, and Nutrients and Potential Impacts on Tropical Coastal Water Biogeochemistry: Oahu, Hawai‘i

“…Filtration through glass fiber filters and freezing can also affect dissolved silica results (American Public Health Association et al 1995), but was not a significant factor in this study due to the high silica concentrations in samples and the small freezing effect (average 2% reduction, Hoover unpublished data). For total organic N and P determinations, an aliquot of thawed sample was UV oxidized to convert dissolved organic compounds to inorganic forms (Armstrong and Tibbits 1968). Oxidized samples then were analyzed for inorganic N and P species using standard colorimetric methods (American Public Health Association et al 1995) on Technicon AAII autoanalyzers.…”

Photochemical formation of biologically available nitrogen from dissolved humic substances in coastal marine systems

“…Samples from the Skidaway River were measured using the UV oxidation method (Armstrong & Tibbitts 1968), while the sample from the Satilla River Estuary was measured using the persulfate oxidation method (Parsons et al 1992). For the Skidaway River samples, a 20 m1 volume was pipetted into a quartz tube with 200 p1 of 30% H 2 0 z , sealed in the tube, and exposed to a UV lamp for 18 h. For the Satilla River Estuary sample, a 40 m1 volume of sample was placed into a 125 m1 Teflon bottle with 6.0 m1 of oxidizing reagent (6.0 g of K2S2O8 in 100 m1 of 1.5 M NaOH) and autoclaved for 30 min and then acidified and buffered (Parsons et al 1992).…”

Gross and net nitrogen uptake and DON release in the euphotic zone of Monterey Bay, California

“…boiling with DeVarda's contained only DO 15 N. Both types of concentrates were transferred to a 100-ml quartz tube, H 2 O 2 was added (50 l per 20 ml seawater), and the concentrates were UV oxidized for 18 h (Armstrong and Tibbits 1968). After the oxidation, all the DON in the sample was then in the form of NO .…”