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Ultraviolet irradiation effects incorporation of nitrate and nitrite nitrogen into aquatic natural organic matter

Journal of Environmental Quality

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,
DOI: 10.2134/jeq2011.0335

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Abstract

One of the concerns regarding the safety and efficacy of ultraviolet radiation for treatment of drinking water and wastewater is the fate of nitrate, particularly its photolysis to nitrite. In this study, 15N NMR was used to establish for the first time that UV irradiation effects the incorporation of nitrate and nitrite nitrogen into aquatic natural organic matter (NOM). Irradiation of 15N-labeled nitrate in aqueous solution with an unfiltered medium pressure mercury lamp resulted in the incorporation of nitrogen into Suwannee River NOM (SRNOM) via nitrosation and other reactions over a range of pH from approximately 3.2 to 8.0, both in the presence and absence of bicarbonate, confirming photonitrosation of the NOM. The major forms of the incorporated label include nitrosophenol, oxime/nitro, pyridine, nitrile, and amide nitrogens. Natural organic matter also catalyzed the reduction of nitrate to ammonia on irradiation. The nitrosophenol and oxime/nitro nitrogens were found to be susceptible to photodegradation on further irradiation when nitrate was removed from the system. At pH 7.5, unfiltered irradiation resulted in the incorporation of 15N-labeled nitrite into SRNOM in the form of amide, nitrile, and pyridine nitrogen. In the presence of bicarbonate at pH 7.4, Pyrex filtered (cutoff below 290–300 nm) irradiation also effected incorporation of nitrite into SRNOM as amide nitrogen. We speculate that nitrosation of NOM from the UV irradiation of nitrate also leads to production of nitrogen gas and nitrous oxide, a process that may be termed photo-chemodenitrification. Irradiation of SRNOM alone resulted in transformation or loss of naturally abundant heterocyclic nitrogens.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Ultraviolet irradiation effects incorporation of nitrate and nitrite nitrogen into aquatic natural organic matter
Series title:
Journal of Environmental Quality
DOI:
10.2134/jeq2011.0335
Volume
41
Issue:
3
Year Published:
2012
Language:
English
Publisher:
American Society of Agronomy
Publisher location:
Madison, WI
Contributing office(s):
Branch of Regional Research-Central Region
Description:
17 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Environmental Quality
First page:
865
Last page:
881
Number of Pages:
17