Intercomparison of four different in-situ techniques for ambient formaldehyde measurements in urban air

[摘要] Results from an intercomparison of several currently used in-situ techniquesfor the measurement of atmospheric formaldehyde (CH₂O) are presented.The measurements were carried out at Bresso, an urban site in the peripheryof Milan (Italy) as part of the FORMAT-I field campaign. Eight instrumentswere employed by six independent research groups using four differenttechniques: Differential Optical Absorption Spectroscopy (DOAS), FourierTransform Infra Red (FTIR) interferometry, the fluorimetric Hantzschreaction technique (five instruments) and a chromatographic techniqueemploying C18-DNPH-cartridges (2,4-dinitrophenylhydrazine). White typemulti-reflection systems were employed for the optical techniques in orderto avoid spatial CH₂O gradients and ensure the sampling of nearly thesame air mass by all instruments. Between 23 and 31 July 2002, up to 13 ppbvof CH₂O were observed. The concentrations lay well above the detectionlimits of all instruments. The formaldehyde concentrations determined withDOAS, FTIR and the Hantzsch instruments were found to agree within ±11%,with the exception of one Hantzsch instrument, which gavesystematically higher values. The two hour integrated samples by DNPHyielded up to 25% lower concentrations than the data of the continuouslymeasuring instruments averaged over the same time period. The consistencybetween the DOAS and the Hantzsch method was better than during previousintercomparisons in ambient air with slopes of the regression line notsignificantly differing from one. The differences between the individualHantzsch instruments could be attributed in part to the calibrationstandards used. Possible systematic errors of the methods are discussed.

[学科分类] 大气科学