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Reaction of Nitric Oxide with Acetylene and Oxygen: Implications for Denitrification Assays
Author(s) -
McKenney D. J.,
Wang S. W.,
Drury C. F.
Publication year - 1997
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1997.03615995006100050012x
Subject(s) - loam , chemistry , denitrification , acetylene , oxygen , nitric oxide , nitrogen , environmental chemistry , soil water , mineralogy , soil science , environmental science , organic chemistry
Nitric oxide reacts with C 2 H 2 at ambient temperature under aerobic conditions with relatively large quantities of O 2 present. We used a gas‐flow system at 20°C to determine the extent, if any, of reaction of NO with C 2 H 2 under nearly anaerobic conditions with addition of trace (<500 µL L −1 ) quantities of O 2 , and to determine whether the process could account for the apparent C 2 H 2 inhibition of NO production in soil. Results showed that reaction occurred only when critical trace quantities of O 2 were present. For example, if [NO] was in the range 0.5 to 2.5 µL L −1 , which is typical of concentrations in our soil studies, approximately 200 to 300 µL O 2 L −1 was required before measurable NO loss was observed. The reaction was first order with respect to NO and variable order, becoming zero order, with respect to O 2 when [O 2 ] exceeded ≈400 µL L −1 and maximum NO depletion rates (≈0.01–0.06 µL L −1 s −1 ) were obtained. The effect of C 2 H 2 on NO production with addition of O 2 (≈20–730 µL L −1 ) in Brookston clay loam (fine‐loamy, mixed, mesic Typic Argiaquoll) and Fox sandy loam (fine‐loamy over sandy or sandy‐skeletal, mixed, mesic Typic Hapludalf) under conditions similar to the gas‐phase studies was also investigated. Depletion of NO in the presence of C 2 H 2 vs. [O 2 ] followed the same pattern with similar rates as the gasphase process. A simplified C 2 H 2 ‐catalyzed scheme for the oxidation of NO to NO 2 provides a plausible, partial explanation for these results. Since NO depletion requires only trace amounts of O 2 , the results suggest that in many previous studies involving assays of NO or N 2 O production based on C 2 H 2 inhibition, significant gas‐phase reaction may have occurred leading to serious errors of interpretation.