Open AccessMeasurement of total nonmethane organic carbon (C y ): Development and application at Chebogue Point, Nova Scotia, during the 1993 North Atlantic Regional Experiment campaign
Author(s) -
Roberts James M.,
Bertman Steven B.,
Jobson Tom,
Niki Hiromi,
Tanner Roger
Publication year - 1998
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/97jd02240
Subject(s) - nova scotia , formaldehyde , mixing ratio , total organic carbon , environmental science , carbon fibers , analytical chemistry (journal) , environmental chemistry , chemistry , atmospheric sciences , physics , materials science , geology , oceanography , composite number , composite material , organic chemistry
A technique was developed for the measurement of total nonmethane organic carbon (C y ) in the gas phase based on cryogenic collection, preseparation of CO, CH 4 and CO 2 , conversion of all carbon to CH 4 , and measurement by flame ionization detector. Collection and recovery efficiencies were found to be essentially quantitative for C 2 ‐C 7 hydrocarbons and better than 95 and 93% for methanol and formaldehyde, respectively. CO 2 prevented the measurement of the C 2 hydrocarbons in atmospheric samples, and system response to ambient water vapor limited the precision of the measurement at very low C y . The measurement system had an estimated uncertainty of 10% at ambient mixing ratios of 100 ppb C, and a detection limit of between 5 and 7 ppb C. C y was measured in Boulder, Colorado, during June of 1993 and at Chebogue Point, Nova Scotia, during the North Atlantic Regional Experiment intensive campaign, August to September 1993. C y values ranged from several hundred ppb C to 11 ppb C in Boulder, and from 177 to below 5 ppb C at Chebogue Point, with medians of 55 and 11 ppb C, respectively. C y was found to correlate with both CO and O 3 at higher levels of those two pollutants. The sum of C y and the C 2 hydrocarbons was virtually always equal to or greater than the sum of the hydrocarbons. Several exceptions to this occurred when high HC values were observed in cannister samples but not C y measurements. These instances were attributed to short‐term perturbations from local sources. There was a net difference between total nonmethane organic carbon and the sum of hydrocarbons and carbonyls of 3.5±7.8 ppb C overall. This difference appears to be broadly correlated with anthropogenic pollution. There does not appear to be a significantly large reservoir of reactive carbon unaccounted for by hydrocarbon or carbonyl measurements.