[Characteristics and Health Risk Assessment of Trace Elements in Atmospheric PM1 During Autumn and Winter in Qingdao].

From November 1,2018 to January 31,2019 (OP2018-2019) and from November 1,2019 to January 20, 2020 (OP2019-2020), PM1 measurement was conducted daily for two consecutive years. The concentration of trace elements in the atmospheric PM1 in Qingdao in autumn and winter was analyzed. The observation period was divided into four air quality levels (Level Ⅰ, Level Ⅱ, Level Ⅲ, and Level Ⅳ), and the characteristics and sources of the concentration of trace elements in PM1 were analyzed. The non-carcinogenic risks (Zn, Pb, Mn, Cu, and V) and carcinogenic risks (As, Cr, Ni, Cd, and Co) of different people with different air quality levels were evaluated. The results showed that the changes in total metal element concentrations were associated with changes in Ca, K, and Al concentrations at different air quality classes during OP2019-2020 compared to those during OP2018-2019 and were more influenced by dust and biomass combustion sources. Compared with that during OP2018-2019, the V concentration in different air quality levels (Level Ⅰ, Level Ⅱ, Level Ⅲ, and Level Ⅳ) during OP2019-2020 decreased by 19.0%, 60.5%, 82.7%, and 77.5%, respectively. This was presumed to be related to the implementation of the Domestic Emission Control Area (DECA) policy for ships, which led to the significant reduction in V concentration due to the change in fuel quality of ships in the waters around Qingdao. The results of the enrichment factor, the ratio method, and the backward trajectory of airflow further indicated that the changes in V concentrations were mainly influenced by the DECA policy. However, after the implementation of the DECA, the V/Ni value as a limit for judging the influence of ship sources in the area required further exploration. The health risk assessment results showed that the risk factor of Mn ranged from 0.07 to 1.22 during OP2018-2019 and OP2019-2020. It was recommended to strengthen the management and control of Mn-containing pollution sources. The lifetime carcinogenic risk (ILCR) value of As and Cd under different air qualities during OP2018-2019 and OP2019-2020 was lower than 10-4 but higher than 10-6, indicating that there was a carcinogenic probability, although it was still at an acceptable level. During OP2018-2019, when the air quality was Ⅳ, the ILCR value of Cr was higher than 10-4, and there was a risk of cancer.

[Effect of a Wet Flue Gas Desulphurization System on the Emission of PM2.5 from Coal-Fired Power Plants].

Wet flue gas desulphurization (WFGD) is wildly used to control SO2 emission from coal-fired power plants. The influence of WFGD on particulate matter (PM) emission has recently drawn significant public attentions in China. In this study, PM2.5 was collected at both the inlet and outlet from three WFGD units, including a single scrubber lime-stone-gypsum FGD unit, a cascade scrubber lime-stone-gypsum FGD unit, and a seawater FGD unit. PM2.5 mass concentrations and their chemical compositions were analyzed. A method to calculate the addition and removal ratios is proposed according to the concertation of PM2.5 components, such as Ti, Pb, Cr, and V. The results indicate that the removal ratio was similar between the three WFGD units (77.1% on average). However, the addition ratio varied significantly. The performance of the cascade scrubber lime-stone-gypsum FGD unit was best, with a lower addition ratio of 8.6%, which is attributed to the weaker evaporation of desulphurization slurry droplets in their second tower under the low temperature of the flue gas. The addition ratio of the seawater FGD unit was also low (23.9%) because of its low concentration of solids in the seawater. The addition ratio of the single scrubber lime-stone-gypsum FGD system was highest, with a value of 162.3%, which was probably due to the low efficiency of the de-mister.

[Application of a Two-stage Virtual Impactor in Measuring of PM10 and PM2.5 Emissions from Stationary Sources].

Recently, the Ministry of Environmental Protection of China started the development of emission inventories in fifteen Chinese cities. It includes the esmission of PM10 and PM2.5 from stationary sources. However, there is no national standard method in China for stationary source PM10 and PM2.5 sampling. In this study, a two-stage virtual impactor was developed for sampling PM10 and PM2.5 from stationary sources. Its performance was evaluated for four types of sataionary sources, i.e., coal-fired power plant, waste incineration, circulating fluid bed, and converter steelmaking. These four tested emission sources were equipped with high efficiency PM control devices. PM2.5 mass concentrations measured in the chimneys of these emission sources were (0.93±0.03), (3.3±0.65), (0.59±0.04), and (0.15±0.04) mg·m-3, respectively, while the PM10 mass concentrations were (1.13±0.11), (6.9±0.86), (1.12±0.16), and (0.43±0.15) mg·m-3, respectively.

[Characteristics of Water-Soluble Inorganic Ions in PM2.5 Emitted from Coal-Fired Power Plants].

To characterize the primary PM2.5 emission from coal-fired power plants in China, and to quantitatively evaluate the effects of flue gas denitrification and desulfurization on PM2.5 emission, a pulverized coal fired (PC) power plant and a circulating fluidized bed (CFB) plant were selected for measuring the mass concentration and water-soluble ion composition of PM2.5 in flue gas. The results showed that the mass concentration of PM2.5 generated from the CFB was much higher than that from the PC, while the mass concentrations of PM2.5 emitted from these two plants were very similar, because the CFB was equipped with an electrostatic-bag precipitator (EBP) with higher PM2.5 removal efficiency than the common electrostatic precipitator (ESP). Although the total concentration of water-soluble ions in PM2.5 generated from the PC was lower than that from the CFB, the total concentration of water-soluble ions in PM2.5 emitted from the PC was much higher than that from the CFB, which implied that PM2.5 emission from the PC was greatly affected by the flue gas treatment installations. For example, the flue gas denitrification system produced H2SO4 mist, part of which reacted with the excessive NH3 in the flue gas to form NH4HSO4 in PM2.5 and to increase the acidity of PM2.5. In addition, the escaping of desulfurization solution during the flue gas desulfurization process could also introduce NH4+ and SO2- into PM2.5. Therefore, although the main water-soluble ions in PM2.5 generated from both of the plants were Ca2+ and SO(4)2-, the major cation was changed to NH4+ when emitted from PC.

[Characteristics of water soluble inorganic ions in fine particles emitted from coal-fired power plants].

Currently, China suffers from serious pollution of fine particulate matter (PM2.5). Coal-fired power plant is one of the most important sources of PM2.5 in the atmosphere. To achieve the national goals of total emission reductions of sulfur dioxide (SO2) and nitrogen oxides (NO(x)) during the 11th and 12th Five-Year Plan, most of coal-fired power plants in China have installed or will install flue gas desulfurization (FGD) and flue gas denitrification (DNO(x)) systems. As a result, the secondary PM2.5, generated from gaseous pollutants in the atmosphere, would be decreased. However, the physical and chemical characteristics of PM2.5 in flue gas would be affected, and the emission of primary PM2.5 might be increased. This paper summarized the size distributions of PM2.5 and its water soluble ions emitted from coal-fired power plants, and highlighted the effects of FGD and DNO(x) on PM2.5 emission, especially on water soluble ions (such as SO4(2-), Ca2+ and NH4+) in PM2.5. Under the current condition of serious PM2.5 pollution and wide application of FGD and DNO(x), quantitative study on the effects of FGD and DNO(x) installation on emission characteristics of PM2.5 from coal-fired power plants is of great necessity.