Ulsan is the city where national industrial complexes are located, and the air quality of the entire region is affected by various air pollutants emitted from industrial complexes. Volatile organic compounds, which are discharged in large quantities f...
Ulsan is the city where national industrial complexes are located, and the air quality of the entire region is affected by various air pollutants emitted from industrial complexes. Volatile organic compounds, which are discharged in large quantities from industrial complexes, contain many substances that are harmful to the human body and have high carcinogenic potential even at low concentrations, so continuous monitoring and management are required. In addition, it is a major cause of ultrafine dust that generates secondary organic aerosols through chemical and photochemical reactions, and affects ozone concentration as a precursor of ozone. Although VOCs are important, measurement items and measurement cycles are limited, and there are not enough measurement stations in Ulsan, so it is difficult to grasp the emission sources and pollution status of the region in detail.
In this study, the concentration of VOCs emitted from national industrial complexes in Ulsan was measured using a Selected-ion flow tube mass spectrometry(SIFT-MS) capable of real-time quantitative analysis of VOCs and the characteristics of VOCs emissions in the industrial complex. In addition, the photochemical ozone generation potential (POCP) of VOCs, which act as a major factor in ozone production, was calculated to examine VOCs substances that affect the ozone concentration in the region. Finally, by conducting a risk assessment on carcinogenic VOCs, it was intended to identify substances that need to be reduced first in terms of risk and provide scientific evidence to improve air quality in the region.
Ulsan-Mipo National Industrial Complex and Onsan National Industrial Complex were divided into five zones, and movement measurements were conducted with vehicles equipped with SIFT-MS. Measurements were performed 7 to 11 times for each area, and the VOCs of 84 substances were measured simultaneously. As a result of the measurement, it was found that the VOCs detected at a high concentration in the Ulsan industrial complex were alcohols and epoxy, and particularly, the concentrations of methyl alcohol, ethylene oxide, and propylene oxide were high. The sum of VOCs concentrations (TVOCs) was the highest in Zone B, where various industries such as petroleum refining, petrochemical, and waste treatment are concentrated.
As a result of ozone formation potential analysis, pentane, methanol, and xylene were found to be substances with high ozone production contribution. Pentane and methanol have lower atmospheric emissions and a lower POCP index than xylene, but their contribution to ozone formation is high due to their high concentration in the atmosphere. Since there is no photochemical pollutant monitoring station in the Ulsan, ozone precursors are not monitored at all times. In order to manage the continuously rising ozone concentration, it is essential to measure substances with high ozone formation contribution at all times.
As a result of conducting a risk evaluation on nine types of carcinogenic VOCs, the cancer risk value was 2.1E-4, exceeding the standard for excess cancer risk of 1.0E-6 to 1.0E-4. The carcinogenic risk of ethylene oxide, propylene oxide, benzene, formaldehyde, acetaldehyde, and 1,3-butadiene exceeded 1.0E-6. The hazard index (HQ), which represents the non-cancer risk, did not exceed 1 for individual substances, but the integrated non-cancer risk (HI), which combines all the risks of the target substances, was found to be more than 1. As a result of the risk assessment, it is necessary to continuously monitor ethylene oxide, propylene oxide, and aldehyde, which have a high risk of cancer, and to prepare measures to reduce them in emission sources. To this end, it is necessary to install additional hazardous air pollutant monitoring stations in Ulsan, and regular monitoring of carcinogenic VOCs is required.
In this study, since VOCs measurement in industrial complexes was performed only during the daytime, additional measurements are required at night to understand the daily fluctuation characteristics of VOCs. In addition, in some high-concentration areas, it is necessary to conduct fixed measurements to identify seasonal behavior and weather effects of VOCs. Comparing the results of this study with the measurement results of VOCs in areas near industrial complexes and non-contaminated areas, identifying the impact of VOCs emitted from industrial complexes remains an additional task.