Among target groups, aromatic groups accounted for most of VOCs (66-86%), in detail, the concentration of toluene was the highest at all the sampling sites over the sampling periods. Comparison of concentration of benzene, toluene, ethylbenzene, m,p-xylene and oxylene in Italia, Finland, Algeria, Canada, USA, Turkey, Korea, and this study.
INTRODUCTION
Volatile Organic Compounds(VOCs)
- Definition and properties of VOCs
- Toxicity of VOCs
- Sources of VOCs
Although atmospheric concentrations of toluene (3 and D), ethylbenzene (2B and D), xylene (3 and D) are higher than other VOCs, these compounds are not classified as carcinogenic by the IARC and the US EPA ( Chen et al., 2015). There are many types of anthropogenic sources for VOCs, from petroleum refining, painting, fossil fuels, solvent use and other industrial processes (Figure 2) (Ly-Verdu et al., 2010).
Passive air samplers
Previous studies conducted in Turkey, Spain, Canada, etc. showed that the concentration of some VOCs from multiple seasons, years and locations could be identified using passive air samplers (Dumanoglu et al., 2014, Miller et al. al., 2012, Parra et al., 2006, Zhang et al., 2014). In addition, other studies have also studied the influence of environmental conditions and the determination of modeled sampling rates (Pennequincardinal et al., 2005), the comparison of Radiello, 3M OVM and Lanwatsu (Lan and Binh, 2012) and the impact of reductions in the limit value of benzene (Simon et al. , 2004).
Ulsan city, South Korea
- Information of Ulsan
- Previous studies about VOCs in Ulsan
Thus, research on VOC monitoring is constantly being studied and interpreted through various tools and methods. Thus, various domestic and international studies on monitoring and risk assessment of VOCs have been conducted using several tools and Monte Carlo simulation, so research on VOCs in Ulsan is required.
Objectives of this study
VOC sampling
A Radiello® diffusion air sampler (Supelco, co.) was used as a passive air sampler for VOC monitoring. During VOC sampling, the insert was attached to a white diffused body, which is made of microporous polyethylene with a thickness of 1.7 mm, a porosity of 25 µm and a length of the diffuse paste of 18 mm.
Meteorological conditions and Criteria air pollutants (CAPs)
Analysis and QA/QC
As surrogate standards, deuterated VOCs (methylene chloride-d2, 1,2-dichloroethane-d4, benzene-d6, toluene-d8, chlorobenzene-d5, ethylbenzene-d10, 1,2-dichlorobenzene-d4 and 1,4-dichlorobenzene - d4) was also inserted into the cartridges before extraction. Using an ultrasonic bath, samples were extracted for 30 minutes, and then 1 ml of extracts were transferred to a vial. As an internal standard, fluorobenzene was added to the vial before injection into an analytical instrument.
After the pretreatment procedures, the samples were analyzed with a gas chromatograph/mass spectrometer (GC/MS, Agilent 7890N/5975C) (Figure 12). One µL of each sample was injected into the GC in split mode (ratio is 25:1, 30 mL/min) and selective ion monitoring (SIM) mode. For quality control and quality assurance, field blanks, method detection limit (MDL) and instrumental detection limit (IDL) were used for data precision.
In the case of MDL, seven samples with a known concentration as calibration standard 1 (CS 1: 0.1 µg) were analyzed with an analytical procedure of real samples, and for IDL, CS 1 was analyzed for seven times with GC/MS.
Calculation of VOC concentration
Identification of VOC sources
Many types of tools, such as diagnostic ratios (toluene/benzene: T/B and m,p-xylene/ethylbenzene: X/E), principal component analysis (PCA), and correlation analysis, have been used in previous studies to identify the source of VOCs. The T/B ratio provides information about traffic or non-traffic origin (Kerchich and Kerbachi, 2012, Sahu and Saxena, 2015). Benzene is a well-known producer of vehicle exhaust (Shi et al., 2015) and toluene, which is mainly released by the evaporation of solvents such as paints (Zalel and Yuval, 2008).
Second, the X/E ratio indicates the aging of VOCs in the atmosphere, because the lifetimes of benzene and toluene in the atmosphere are 12.5 and 2.0 days, which means they are stable, and ethylbenzene and xylene are 8 and 3 hours, respectively (Liu et al. , 2008). ). Typically, principal component analysis has been used to simplify the number of effect factors by extracting target compounds, meteorological data, or measured air pollutants, and PCA results can show that the emissions of vehicles, industrial complexes, or gas stations could be affected by a specific study area (An et al. ., 2014a, Hsieh et al., 2006, Liu et al., 2008, Ohura et al., 2006). This type of analysis can be divided according to the distribution of parameters such as measured values, meteorological data, air pollutant criteria or any other.
In this study, both methods were applied to check the correlation of each parameter and the relationship can be related to the emission sources.
Risk assessment of VOCs
The hazard identification is the process of determining whether or not target compounds may cause adverse health effects. As previously mentioned, various institutes have classified pollutants into a group (carcinogenic or non-carcinogenic) that may be indicators of chemical toxicity to human health. Finally, the risk characterization is the process of deciding whether or not risk, calculated by some equations, has potential for adverse effects on human health.
Then, in the case of carcinogenic compounds, the actual risk can be expected using the equation mentioned above. A standard acceptable HQ means that levels above 1.0 are of potential health concern, whereas those below 1.0 are not harmful to humans (Bunch et al., 2014). In this study, Monte Carlo simulation was used to reduce the uncertainty of the risk assessment (Bunch et al., 2014, Civan et al., 2015).
Therefore, the results of the risk assessment should be evaluated using this simulation (worst or safety case).
RESULTS AND DISCUSSION
Meteorological conditions and criteria air pollutants
- Meteorological data
- CAPs data
However, Figure 17 only shows the OT wind direction in Ulsan and cannot be applied to all sampling sites in this study. CAPs are also one of the important factors to understand the atmospheric environment in the study area. To investigate the contamination levels of CAPs, provided by UIAL, the sampling sites of UIAL and this study were matched (Figure 19).
Large amounts of pollutants will be released from all the industrial complexes in the summer and spring seasons, they can be applied to urban areas. Therefore, concentration of VOCs, which were selected on the basis of 13 VOCs, were compared in this study with those of the KME at the same sampling locations during four seasons (Figure 20). In the case of 1,3-butadiene, the concentration in this study was not detected in all the seasons, on the contrary, that of the UIHE was quite detected in all the seasons.
Compared with the industrial site, the concentration of toluene in this study was much higher than that of UIHE in all seasons, and the concentration of m,p-xylene in UIHE was higher during the four seasons and sites.
Levels and patterns of VOCs
- Seasonal variations of VOC concentration
- Concentration of target compounds
- Fractions of three groups
- Fractions of BTEX
- Concentration of total VOCs at the sampling sites
Concentration of the three groups (a) and fraction of the detailed aromatic group based on annual mean levels (b). The concentration of total VOC and BTEX in the annual mean at each sampling site was compared as shown in Figure 28, and those of the seasonal data were presented in Figures S6–S9. As an industrial site, the concentration at location I2 showed lower concentration of total VOCs than that of other industrial sites.
The concentration of total VOCs at the U1 site was the least in all four seasons because this site is the furthest away from the industrial complexes among sampling sites in Ulsan. Compared to the concentration of total VOCs and BTEX, slightly different patterns were shown at I3 and I4 sites. In addition, BTEX concentration of industrial and urban areas is represented in Figure S10 as are total VOCs (Figure 29).
Comparison with the concentration of total VOC at industrial and urban locations in annual average, summer, autumn, winter and spring.
Spatial distribution of VOCs
Spatial and seasonal variation and source apportionment of volatile organic compounds (VOCs) in a heavily industrialized region. Seasonal and diurnal variations of volatile organic compounds (VOCs) in the atmosphere of Hong Kong. Characterization of volatile organic compounds in the ambient air of industrial area, Environmental Engineering, Yeungnam.
Concentrations of water-soluble particles, gaseous ions, and volatile organic compounds in the ambient air of Ulsan. Spatial and temporal trends of volatile organic compounds (VOC) in a rural area of northern Spain. Volatile organic compounds (VOCs) in air from Nisyros Island (Dodecanese Archipelago, Greece): Natural versus anthropogenic sources.
Ambient levels of volatile organic compounds near the Yokohama Petrochemical Industrial Zone, Japan.
Source identification
Risk assessment
Based on the measured concentrations and some data, including inhalation rate, exposure duration, body weight, etc., a risk assessment for benzene with respect to carcinogenic risk and for toluene, ethylbenzene and xylenes with respect to non-carcinogenic risk was carried out in this study. It can be expected that the carcinogenic risk of benzene can reach a high level in the worst case scenario, such as dangerous chemical accidents. Although the concentration of TEX was higher than other target compounds in all sampling periods in this study, there was no cancer risk to human health due to its low carcinogenicity as a non-carcinogenic compound.
In addition, a risk assessment was performed for 1,2-dichloroethane, vinyl chloride, 1,3-butadiene (carcinogenic compounds) and MTBE (non-carcinogenic compound) (Figure S11). Although the concentration of 1,2-dichloroethane was much lower than that of TEX, the risk was higher than acceptable levels at percentiles ranging from 100% in summer, 70-100% in autumn, 100% in winter and spring. Therefore, the results of this study can be used to determine the limit value of air pollutants or for clean air management.
Carcinogenic risk of benzene (a) and non-carcinogenic risk of toluene (b), ethylbenzene (c) and m,p,o-xylenes (d) using Monte Carlo simulation over four seasons.
CONCLUSIONS
Assessment of the impact of shale gas operations in the Barnett Shale region on airborne volatile organic compounds and potential human health risks. Post-Hurricane Katrina passive sampling of ambient volatile organic compounds in the greater New Orleans area. Exposure of drivers and conductors to noise, heat, dust and volatile organic compounds in Kolkata city state transport special buses.
Environmental risk assessment and concentration trend of atmospheric volatile organic compounds in Hyogo Prefecture, Japan. Volatile organic compounds over the eastern Himalaya, India: temporal variation and source characterization using positive matrix factorization. Personal exposure to volatile organic compounds among outdoor and indoor workers in two Mexican cities.
Source characteristics of volatile organic compounds during periods of high ozone concentrations in Hong Kong, South China.
