Direct measurement of denitrification loss from soils. I. Laboratory evaluation of acetylene inhibition of nitrous oxide reduction
The rate and extent of denitrification in soils incubated under helium atmospheres in the presence of acetylene (C/sub 2/, H/sub 2/) concentrations ranging from 0.1 to 5.0% (vol/vol) was equivalent to that measured in the absence of C/sub 2/H/sub 2/. In the absence of C/sub 2/H/sub 2/, gaseous nitrogen (N) appeared as a mixture of nitrous oxide (N/sub 2/O) and dinitrogen (N/sub 2/), usually dominated by N/sub 2/, whereas in the presence of C/sub 2/H/sub 2/ gaseous N appeared exclusively as N/sub 2/O. An C/sub 2/H/sub 2/ concentration of 1.0% was also sufficient to maintain inhibition of N/sub 2/O reduction even when the soil nitrate supply had been exhausted. Overall respiration of incubation systems, measured as carbon dioxide evolution, was also unaffected by the presence of C/sub 2/H/sub 2/. Similar findings were obtained when soils were incubated under argon-oxygen (4:1) atmospheres containing 1.0% C/sub 2/H/sub 2/. The inhibitory effect of C/sub 2/H/sub 2/ was virtually instantaneous when a 1.0% C/sub 2/H/sub 2/ concentration was established in an actively denitrifying soil. Diffusion of C/sub 2/H/sub 2/ into soils packed to their maximum bulk density and held at 5% air-filled porosity was also sufficiently rapid to induce essentially complete inhibition of N/sub 2/O reduction during incubation in air using a /sup 15/N-labeled nitrate addition to the soil. The extent of denitrification varied among soils and ranged from 54 to 154 ..mu..g N/g under helium atmospheres, and from 15 to 106 ..mu..g N/g under argon-oxygen atmospheres, after 200 hours incubation. Ratios of N/sub 2//N/sub 2/O were essentially the same whether measured directly or calculated from the difference in N/sub 2/O production in the presence and absence of C/sub 2/H/sub 2/. The findings are discussed with respect to the use of the C/sub 2/H/sub 2/ inhibition technique for direct infield measurement of denitrification. 17 references, 6 figures, 2 tables.
- Research Organization:
- Univ. of California, Riverside
- OSTI ID:
- 6218013
- Journal Information:
- Soil Sci. Soc. Am. J.; (United States), Vol. 43:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
NITROUS OXIDE
INHIBITION
SOILS
DENITRIFICATION
ACETYLENE
ECOLOGICAL CONCENTRATION
INCUBATION
LOSSES
NITROGEN
ALKYNES
CHALCOGENIDES
CHEMICAL REACTIONS
ELEMENTS
HYDROCARBONS
NITROGEN COMPOUNDS
NITROGEN OXIDES
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
510100* - Environment
Terrestrial- Basic Studies- (-1989)