The determination of ambient formaldehyde using a dual coil system and an assessment of dominant factors that influence its abundance in Korea

Abstract

An enhanced dual coil 2,4-dinitrophenylhydrazine (DNPH) derivatization method (dual coil/DNPH) allowed the quantitative determination of formaldehyde (HCHO) in ambient air. In this method, traceable HCHO was collected using a coil sampler connected in series and lacking a long sampling tube. It was then analyzed using liquid chromatography followed by UV detection of the DNPH derivatives. The method is based on the reaction of formaldehyde with DNPH to produce 2,4-dinitrophenylhydrazone. The detection limits (3sigma) were 0.10-0.40 ppbv with a precision ranging from 0.84 to 4.09% RSD. The results of dual coil/DNPH and conventional DNPH cartridge methods were generally well correlated: HCHO (dual coil/DNPH)=0.97 (+/-0.13) vs. HCHO (DNPH Cartridge)+0.33 (+/-0.33), r=0.82. The dual coil/DNPH method was used to measure gaseous HCHO in the atmosphere of Metropolitan Seoul during the summer 2000 and 2001, and in Gwangju during the fall of 2001 and 2002. The daytime mean concentration of HCHO was 4.52 (+/-5.69) and 3.21 (+/-1.27) ppbv in Metropolitan Seoul for 10-12 August 2000 and 29-31 May 2001, respectively, and 1.73 (+/-0.98), 3.04 (+/-2.25), 2.70 (+/-1.70), and 2.01 (+/-2.28) ppbv in Gwangju City during 22-27 September 2001, 17-24 October 2001, 9-13 October 2002, and 28 October to 2 November 2002, respectively. The HCHO in Seoul from 10-12 August 2000 was mainly the result of photochemical processes, while direct emissions from vehicles and long-range transport of air from China contributed during 29-31 May 2001. During 22-27 September 2001, 17-24 October 2001, and 9-13 October 2002 in Gwangju, the HCHO came primarily from photochemical processes, although some air affected by biomass burning admixed in the late afternoon. The increase in the HCHO concentration on 20 October 2001 and from 28 October to 2 November 2002 was attributed mainly to direct emissions from biomass burning in farmland near the measurement site.