GC×GC measurements of C<sub>7</sub>-C<sub>11</sub> aromatic and n-alkane hydrocarbons on Crete, in air from Eastern Europe during the MINOS campaign

Abstract

Abstract. During the Mediterranean Intensive OxidantStudy (MINOS) campaign in August 2001 gas-phase organic compounds were measured using comprehensive twodimensional gas chromatography (GC×GC) at the Finokalia ground station, Crete. In this paper, C 7 −C 11 aromatic and n-alkane measurements are presented and interpreted. The mean mixing ratios of the hydrocarbons varied from 1±1 pptv (i-propylbenzene) to 43±36 pptv (toluene). The observed mixing ratios showed strong day-to-day variations and generally higher levels during the first half of the campaign. Mean diel profiles showed maxima at local midnight and late morning, and minima in the early morning and evening. Results from analysis using a simplified box model suggest that both the chemical sink (i.e. reaction with OH) and the variability of source strengths were the causes of the observed variations in hydrocarbon mixing ratios. The logarithms of hydrocarbon concentrations were negatively correlated with the OH concentrations integral over a day prior to the hydrocarbon measurements. Slopes of the regression lines derived from these correlations for different compounds are compared with literature rate constants for their reactions with OH. The slopes for most compounds agree reasonably well with the literature rate constants. A sequential reaction model has been applied to the interpretation of the relationship between ethylbenzene and two of its potential products, i.e. acetophenone and benzeneacetaldehyde. campaign are estimated using the sequential reaction model and related data. They lie in the range of about 0.5-2.5 days.

Origin of anthropogenic hydrocarbons and halocarbons measured in the summertime european outflow (on Crete in 2001)

“…This is consistent with the range of the air mass ages estimated with toluene/benzene ratios (15-35 h, Salisbury et al, 2003) and ethylbenzene/acetophenone ratios (15-59 h, Xu et al, 2003). The coefficient b of this study has an absolute value of 0.23 and is significantly lower than the value of ∼0.5 found during PEM-West B and at Amsterdam Island in the Indian Ocean (Jobson et al, 1999;Williams et al, 2001) but higher than the value of 0.18 found for the Harvard Forest site (Jobson et al, 1999).…”

“…The concentration of OH was taken as the mean value measured during periods 1 and 2 (4.0×10 6 molecules cm −3 , Berresheim et al, 2003). Finally, transport times of 24 h and 48 h were considered to cover the range estimated by using toluene/benzene and ethylbenzene/acetophenone ratios (Xu et al, 2003) for the corresponding periods.…”

Comprehensive two-dimensional gas chromatography (GC × GC) measurements of volatile organic compounds in the atmosphere

“…On the other hand, they also suggest that the anthropogenic impact on the air chemistry at the site may still be important, considering the high reactivity of the compounds. More detailed analysis and interpretation of the hydrocarbon data are presented in Xu et al (2003).…”

“…This paper describes the instrumental set-up as well as the identification and quantification techniques. An atmospheric chemistry analysis and interpretation of the quantitative data are given in a separate paper (Xu et al, 2003).…”

Caracterização de amostras petroquímicas e derivados utilizando cromatografia gasosa bidimensional abrangente (GCxGC)

“…Xu e colaboradores 48 desenvolveram um sistema muito interessante para monitoramento in situ de VOC ("Volatile Organic Compounds", Compostos Orgânicos Voláteis) na atmosfera de Creta, envolvendo um equipamento GCxGC-FID com modulador criogênico de duplo jato. A coleta e a pré-concentração "on-line" dos analitos de interesse foram realizadas utilizando-se "traps" refrigerados e filtros de carvão ativo.…”