The scope of this project includes: (1) monitoring of dioxins and heavy metals ambient air concentration (2) establishing and updating both dioxin and heavy metals domestic emission inventory (3) assisting the emission control, emission reduction and emergency response regarding dioxins and heavy metals which includes reconsideration and modification of emission standards The ambient air dioxins and heavy metal were measured in February and August this year. The average concentration of dioxins in 21 counties and cities were 0.021 and 0.015 pg I-TEQ/m³ (dioxins: 0.020 and 0.015 pg WHO₂₀₀₅-TEQ/m³, polychlorinated biphenyl (PCB): 0.0016 and 0.0015 pg WHO₂₀₀₅-TEQ/m³) respectively. The average concentrations were lower than the average value of the monitoring results in the same period of the previous years. The ambient air concentrations of hazardous heavy metals obtained in general air quality monitoring stations were lower than the air quality standards of Taiwan, European Union and WHO. The concentration of heavy metals which were relatively abundant in crust were higher than the other metal elements. The total mass concentrations of 22 analyzed heavy metals accounted for about 2.72% of PM₁₀ concentration. The total dioxins emission quantity was estimated to be 43.07 g I-TEQ/year in 2021, significantly lower than that in 2020. The reduction was mainly caused by the lower agricultural open burning amount in 2021 according to Taiwan Emission Data System version 11.1 (TEDS 11.1). The main dioxin stantionary emission sources consist of coal-fired power plants, steel melting industries and incinerators. The main sources mentioned accounted for 61.8% of the total emission. As for the heavy metal, the emission amount of lead, cadmium, mercury and arsenic was 29.8, 0.728, 1.68 and 2.67 tons respectively in 2021. The emission amounts were similar to that in 2020. In respect of uncertainty analysis and emission level classification, the emission data for stationary source was calculated based on actual emission tests and database from air pollution fee which could demonstrate a better reliability. In contrast, due to the lack of test data, the estimated emission amount of fugitive sources and mobile sources had lower reliability. Fluorine emission concentrations of 6 tested cement kilns were similar. The stack test results were all under 1mg/Nm³. According to studies, the high melting point of the fluoride compound in the manufacturing process led to a larger mass proportion of the substance leaving the system in clinker. The mercury emission concentration of the tested cement kilns ranged for 20 to 50μg/Nm³. The factor causing a higher emission concentration included the type and operation paramters of dedust device and the usage of substitute raw material such as fly ash from coal power plants. A total of 10 plants of emission reduction counseling were included in this project. This part of work aimed to assist emission sources with emission reduction by the advices given by experts. The imformation gathered in these counseling meeting could be used as a reference for future emission standards revision. Among the counseled emission sources, one of the visted cremation furnaces had no air pollution controlling device specificly targeting on dioxin removal. However, through appropriate burning temperature control, the emission source has never exceeded dioxin emission limit. Experts advised that the frequency of bag filter exchanging should be controlled rather than replacing it only if damaged bags was noticed to prevent the potential probability of violating the emission standards. Another cremation furnaces adopted catalyst for dioxin removal but the operation temperature was not enough for catalystic degradation. The visited Refuse-derived fuel (RDF) boiler had an unstable oxygen content in its flue gas according to it stack tests. The oxygen content was crucial for complete combustion to avoid the fabrication of dioxin. Thus, a more stable operation condition was needed for the emission source to lower its dioxin emission. Both of the 2 visited wood boilers had a high particle matter emission. The high dioxin concentration value in their stack tests report might caused by the dioxin adsorbed on particles. Thus, strengthening the maintaince of its bag filter could be an appropriate approach to prevent high dioxin emission. Both of the 2 visited steelmaking sinters had complete series of APCD. However, one of them return the fly ash back to sinter without any pretreatment. This might cause chloride acummulation in the system which lead to potential increase of dioxin emission concentration. Both of the 2 visited fly ash smelting furnaces adopted bag filter as its APCD. One of them recently had dioxin emission concentration violating the emission standard. Due to the positive correlation of its particle and dioxin emission, experts recommended enhancing the maintenance of its particulate matter capturing device. By reconsidering and reviewing of emission control standards, the revised emission standards steelmaking sinter and fly ash smelting furnace were proposed. More stringent dioxin emission standards for the emission sources mentioned above will be applied to existing sources in the draft recommendation.

Dioxin, Heavy Metals, Environmental Monitoring, Emission Reduction