INVESTIGATION ON THE SPATIAL AND TEMPORAL VARIATIONS OF VOLATILE ORGANIC COMPOUNDS (VOCs) IN ULSAN

Abstract

Large amounts of Volatile Organic Compounds (VOCs) are emitted from industrial facilities, and they can cause harmful effects to human health. Once emitted to the atmosphere, VOCs are dispersed into surrounding areas and directly inhaled by residents. Ulsan, known as the largest industrial city of South Korea, has many kinds of factories related to petrochemical, automobile, non-ferrous, and shipbuilding industries. Large VOC emissions are expected in Ulsan, thus continuous and intensive monitoring is required. The aim of this study is to investigate the levels, pattern, spatial distribution, main sources, and risk levels of VOCs in Ulsan, South Korea. In this study, VOC monitoring in Ulsan was conducted using passive air sampler (Radiello 130 packed with 530 mg of active charcoal with particle size of 35-50 mesh). The samplers were deployed at 14 sites in Ulsan during summer (02-31 July (30 days) and 31 July-29 August, 2014 (30 days)), fall (08 October-07 November (30 days) and 07 November-05 December, 2014 (30 days)), winter (08 January-03 February (26 days) and 03 February-03 March, 2015 (30 days)), and spring (10 April-08 May (28 days) and 08 May-07 June, 2015 (30 days)). Sampling sites were divided into urban (U1-U8) and industrial (I1-I6) areas. The target compounds were 28 VOCs which were classified into three groups, including aromatic, halogenated, and others (alkene and oxygenated). Radiello cartridges were extracted, and the extracts were analyzed using a gas chromatograph/mass spectrometer (Agilent 7890A/5975C). The target VOCs were generally detected at all sampling sites, indicating that VOCs are ubiquitous in Ulsan and not good for human health. Particularly, there were no significant differences in seasonal concentration of VOCs, because many industrial facilities, located in Ulsan, emit VOCs continuously regardless of weather. Among target groups, aromatic groups accounted for most of VOCs (66-86%), in detail, concentration of toluene was highest at all the sampling sites over the sampling periods. Also, most of total VOC concentrations were relatively high at industrial sites and low at urban sites. According to the spatial distributions of VOCs, all major industries of Ulsan seem to be the important VOC sources, especially automobile industrial complexes. To identify main sources of VOCs, a variety of statistical tools were used. As a result, non-traffic sources were dominant in Ulsan, and several compounds had a good correlation, indicating similar emission sources. Although there are many kinds of industrial facilities in Ulsan, risk was not serious according to risk assessment of benzene, toluene, ethylbenzene, and xylenes (BTEX). Through this preliminary study, we could identify seasonal major sources and risk levels of VOCs in Ulsan. This study is the first comprehensive study for VOCs including high resolution monitoring in Ulsan, therefore, it can be applied to other national industrial complexes in South Korea.