5:15 PM - 7:15 PM
[AAS11-P15] Atmospheric trend of ethylene oxide in the Greater Tokyo Area
Keywords:Ethylene oxide , Reagional chemical transport model, Atmospheric lifetime
Ethylene oxide (EtO) is a toxic chemical which induces cancer. The governments worldwide are now trying to mitigate the ambient concentration of EtO by regulating the total emissions of EtO from the emission sources (medical industries, chemical plants, laboratories, etc.). Chemical transport model (CTM) is the strong tool to understand the chemical and physical behaviors of the atmospheric pollutants, and here in this study, we conducted regional-CTM calculations targeting the Greater Tokyo Area (GTA) in 2017 to clarify the reproducibility of EtO concentrations calculated by CTM to the observed results, as well as to clarify the importance of long-range transport and meteorological factors to EtO concentrations.
Meteorological parameters were calculated by WRFv4.5.1 in the three nested regions: East Asia, whole Japan, and the GTA. The calculated periods were from Dec 16 2016 to Dec 31 2017 of which the first two weeks (Dec 16 2016 ~ Dec 31 2016) were treated as the spin-up periods, and remained whole 2017 were treated as the analyzed term. Applying calculated meteorological inputs, chemical transport modeling calculations were conducted by CMAQv5.4. The emission inventory of EtO for CTM calculation was obtained from PRTR database provided by the Ministry of Economy, Trade and Industry. The temperature dependent kinetic parameters of the reaction of EtO with four radical species (OH, Cl, ClO, and NO3) were estimated by the quantum chemical calculations coupled by the transition state theory, and the obtained kinetics were incorporated into SAPRC-07 gas phase chemical mechanism applied in CTM.
The results suggested that the calculated annual-mean EtO concentrations were ~1 order of magnitude lower than the observed results while the calculated annual-maximum EtO concentrations were about the half of the observed results; indicated that the incorporation of EtO emission inventory obtained by PRTR data was not enough to replicate the ambient concentration of EtO. To amend the underestimation of EtO concentration calculated by CTM, we modified PRTR-based emission inventory according to two assumptions: 1. Taking annual-sales information and introducing ratio of after treatment devices of EtO into account, and 2. Assuming EtO emissions in the whole East Asian regions to consider long range transport. While the improvement of PRTR-based emission inventory successfully replicated annual-maximum EtO concentrations, it still did not capture the annual-mean concentration of EtO, suggesting that global-scale background concentration should be considered in the CTM calculation. Atmospheric lifetime of EtO was derived from the results of the quantum chemical and transition state theory calculations, which suggested ~300 days of the lifetime of EtO in global-scale, and this also suggested the importance of global-scale background concentration of EtO to be considered in CTM results. Seasonal trend of the EtO concentrations in the GTA was analyzed based on the results from CTM and observations, which resulted in relatively high concentrations of EtO occurring during cold seasons due to the lowered planetary boundary layer.
This study was funded by the Ministry of Economy, Trade and Industry. Part of observed data were provided by the Ministry of the Environment.
Meteorological parameters were calculated by WRFv4.5.1 in the three nested regions: East Asia, whole Japan, and the GTA. The calculated periods were from Dec 16 2016 to Dec 31 2017 of which the first two weeks (Dec 16 2016 ~ Dec 31 2016) were treated as the spin-up periods, and remained whole 2017 were treated as the analyzed term. Applying calculated meteorological inputs, chemical transport modeling calculations were conducted by CMAQv5.4. The emission inventory of EtO for CTM calculation was obtained from PRTR database provided by the Ministry of Economy, Trade and Industry. The temperature dependent kinetic parameters of the reaction of EtO with four radical species (OH, Cl, ClO, and NO3) were estimated by the quantum chemical calculations coupled by the transition state theory, and the obtained kinetics were incorporated into SAPRC-07 gas phase chemical mechanism applied in CTM.
The results suggested that the calculated annual-mean EtO concentrations were ~1 order of magnitude lower than the observed results while the calculated annual-maximum EtO concentrations were about the half of the observed results; indicated that the incorporation of EtO emission inventory obtained by PRTR data was not enough to replicate the ambient concentration of EtO. To amend the underestimation of EtO concentration calculated by CTM, we modified PRTR-based emission inventory according to two assumptions: 1. Taking annual-sales information and introducing ratio of after treatment devices of EtO into account, and 2. Assuming EtO emissions in the whole East Asian regions to consider long range transport. While the improvement of PRTR-based emission inventory successfully replicated annual-maximum EtO concentrations, it still did not capture the annual-mean concentration of EtO, suggesting that global-scale background concentration should be considered in the CTM calculation. Atmospheric lifetime of EtO was derived from the results of the quantum chemical and transition state theory calculations, which suggested ~300 days of the lifetime of EtO in global-scale, and this also suggested the importance of global-scale background concentration of EtO to be considered in CTM results. Seasonal trend of the EtO concentrations in the GTA was analyzed based on the results from CTM and observations, which resulted in relatively high concentrations of EtO occurring during cold seasons due to the lowered planetary boundary layer.
This study was funded by the Ministry of Economy, Trade and Industry. Part of observed data were provided by the Ministry of the Environment.