The scope of this project includes: 1) investigating the stationary emission and monitoring the dioxins and heavy metals concentration in ambient air; 2) establishing and updating both dioxin and heavy metals domestic emission inventory; 3) assisting the control, reduction and emergency response of dioxins and heavy metals emission which includes reconsideration and review of emission standards
Dioxin and heavy metal emission surveys were performed at three stationary sources respectively. The dioxin eission investigation includes a boiler using solid recoverd fuel (SRF), a steel making electric arc furnace (EAF) and a secondary lead smelting furnace for dioxin. The dioxin concentration of the steel making EAF was much lower than the emission standard due to the high particle removal efficiency and fast cooling of its air pollution controlling devices (APCD). The secondary lead smelting furnace had a low dioxin emission concentration which indicated that secondary lead smelting furnace was not one of the main dioxin emission source. The boiler demonstrated low dioixin emission concentration due to its low chlorine content SRF and activated carbon injection device. On the other hand, The heavy metal eission investigation includes a coal power plant, a coal-fired cogeneration plant and a gas-fired power plant. The heavy metals concentration of the coal power plant and coal-fired cogeneration plant both meet the corresponding emission standards. The mercury emission concentration, sampled by using Methed 30B, of the gas-fired power plant was extremely low without any effective APCD for mercury removal. Thus, as far as heavy metal emission control is concerned, natural gas is a relatively clean energy source when compared with coal.
Dioixn and heavy metal ambient air monitoring were both conducted twice in this project, the annual average ambient air dioxin concentration was 0.030 pg I-TEQ/m³ (Feburuary 2021: 0.040 pg I-TEQ/m³, August 2021: 0.019 pg I-TEQ/m³)or 0.026 pg WHO-TEQ/m³(Feburuary 2021: 0.034 pg WHO₂₀₀₅-TEQ/m³, August 2021:0.017 pg WHO₂₀₀₅-TEQ/m³). Polychlorinated biphenyl (PCB) concentration was much lower in ambient air with a annual average concentration of 0.0025 WHO₂₀₀₅-TEQ/m³ (Feburuary 2021: 0.0031 pg WHO₂₀₀₅-TEQ/m³，August 2021: 0.0018 pg WHO₂₀₀₅-TEQ/m³). Compared with the monitoring results in the same period of previous years, ambient air dioxin concentration has a decreasing trend. The ambient concentrations of hazardous heavy metals obtained in general air quality monitoring stations met the standards of Taiwanese, European Union and WHO. Metals which are abundant in crust, had higher concentrations than the others. Mercury ambient air concentrations were in the range of 1.80~3.56 ng/m³. The ratio of particulate mercury and gaseous mercury was 2.3%. Both dioxin and heavy metal concentration were lower in August.
The total dioxin emission quantity estimation in 2020 was 47.7 g I-TEQ/year, slightly lower than that in 2019. The main dioxin emission sources consist of coal-fired power plants, steelmaking industries, incinerators and fugitive emission sources (fire, straw and agricultural waste combustion, etc.), which accounts for 82.5% of the total emission. On the other hand, heavy metal emission quantity calculation results were similar to that in 2019. lead, cadmium, mercury, arsenic emission quantity was clacutaled to be 30.1ton/year, 0.755 ton/year, 1.75 ton/year and 2.73 ton/year. The burning sources accounted for over 60% of the total emission amount of each heavy metal which indicated the importance of emission reduction and management for the sources. Regarding the uncertainty analysis of the estimated emission quantity, the emission data for stationary source were calculated based on actual emission tests and database from air pollution fee which demonstrated good reliability. In contrast, due to lack of test data, the estimated emission amount of fugitive sources and mobile sources have lower reliability.
A total of 10 plants of emission reduction counseling were included in this project. The targeted plants consist of 1 cement kiln, 4 industrial waste incinerators, 4 wood boilers and 2 cremator. This work aims to assist domestic emission source in emission reduction by the advices given by experts and also gather imformation for emission standards reconsideration.
The revised emission standards for incinerator, steelmaking sinter, cement kiln and lead secondary production were proposed in this project. Revised emission standards for lead secondary production and cement kiln were official announced in June 29, 2021 and November 2, 2021 respectively. Mercury and Fluorine emission limits for cment kiln are recommended to be added in the next stage of rulemaking. Emission standards for steelmaking sinter should be reviewed due to the improvement of domestic sinters’ air pollution controlling device.
