Rl. Tanner et al., CONCENTRATIONS OF CARBONYL-COMPOUNDS AND THE CARBON ISOTOPY OF FORMALDEHYDE AT A COASTAL SITE IN NOVA-SCOTIA DURING THE NARE SUMMER INTENSIVE, JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 101(D22), 1996, pp. 28961-28970
The concentrations of gaseous atmospheric carbonyl compounds have been
measured at a coastal site on the southern tip of Nova Scotia during
August 1993 as part of the National Oceanic and Atmospheric Administra
tion's North Atlantic Regional Experiment (NARE) summer intensive. The
DNPH-cartridge technique was used for sampling, with analysis by HPLC
with UV absorbance detection. The carbon isotopic content of formalde
hyde was measured using a novel collection technique on bisulfite-coat
ed fillers followed by accelerator mass spectrometric determination of
C-14 content and C-13/C-12 isotopic ratios. Results from this study i
ndicate that quantifiable levels above about 100 parts per trillion by
volume were found at the Chebogue Point, Nova Scotia, site for severa
l carbonyls, formaldehyde, acetaldehyde, acetone, propionaldehyde, met
hyl ethyl ketone, and benzaldehyde, for most 6-hour sampling periods.
Six-hour averaged formaldehyde levels of <0.5 to about 3.5 parts per b
illion were found during periods of local influence and during influen
ce of continental air masses crossing eastern Canada and northeastern
US. In contrast, background levels of formaldehyde of 200-400 pptv wer
e found under conditions of predominantly marine back trajectories. La
rge fractions of contemporary carbon (of the order of 80%) were found
in collected formaldehyde samples for all transport regimes and formal
dehyde concentrations, suggesting that biogenic sources of hydrocarbon
precursors to formaldehyde predominated during the summer season.