Total non-methane volatile organic compounds (TNMVOC) in the atmosphere ofDelhi

Volatile organic compounds (VOC), more specifically, non-methane volatile o rganic compounds (NMVOC) play a critical role in the atmospheric chemistry. NMVOC, through complex photochemical reactions, contribute to the formatio n of toxic oxidants, such as tropospheric ozone and PAN, which are injuriou s to health and highly phytotoxic. Certain NMVOC have been shown to be high ly toxic, mutagenic and carcinogenic. NMVOC are receiving increasing attent ion in the west on account of their implication for human health and air qu ality. On the other hand, information on NMVOC in India and other developin g countries is not available. As a result, appreciation of potential threat from NMVOC in relation to air quality and public health is sadly lacking a mong planners and policy makers. The paper deals with the estimation of tot al NMVOC at 13 sites in the urban environment of Delhi during November 1994 to June 1995. An inexpensive, labour intensive manual sample collection de vice was used and the air samples were analysed using GC-FID. The results s how that the amount of NMVOC in the ambient environment of Delhi varied bet ween 1.3 and 32.5 ppmv exhibiting wide temporal and seasonal variation. NMV OC levels mostly peaked at 0900 h, which coincide with the peak traffic hou r. The implications of NMVOC build-up in the urban atmosphere are obvious f or air quality. The results of this preliminary study make out a strong cas e for developing a regular monitoring programme for NMVOC in the urban envi ronment of Delhi as well as in other major cities in the region. (C) 1999 E lsevier Science Ltd. All rights reserved.