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A large petrochemical complex, dubbed Petro–complex, situated in a rather rural region of Taiwan, was used as a test bed to detect emissions from the Petro–complex to its surroundings. Hourly observations of speciated non–methane hydrocarbons (NMHCs) by the photochemical assessment monitoring stations (PAMSs), as well as the total amounts of NMHCs, SO2, and NOx provided by the air quality stations (AQSs), were utilized to find useful petro–emission indication methods. The analytical aspect of NMHCs either as a speciated form or as total amounts was demonstrated through field comparison to illustrate data quality. Using ethyne to offset traffic influence, the ratios of ethene to ethyne (acetylene) (E/A) and propene to ethyne (P/A) were proven to be effective indicators of petro–emissions owing to pronounced emissions of ethene and propene, revealed as tall spikes in PAMS measurements. SO2 and NOx were also explored as petro–emission indicators mainly for stack sources. By coordinating with three–dimensional modeling, SO2 from petro–emissions could be distinguished from other prominent sources, such as coal–fired power plants. An attempt was also made to use SO2 and NOx as indicators of broader petro–emissions with stringent criteria to minimize traffic interference and increase specificity. Similar findings were observed with the three indicators, that is, volatile organic compounds (VOCs) ratios, SO2 and NOx, to identify the southwest area of the Petro–region as the most affected area, as represented by Taisi station (F2). The percent affected time of a year at F2 was 10%–14%, owing to the dominant wind field of northeast monsoonal (NEM) in the region, as compared with other sites in the east and north of 1–5%. Using VOC ratios as petro–emission indicators is more effective than using other gases, owing to the compositional advantage to minimize traffic interference. [ABSTRACT FROM AUTHOR]

The low-low-temperature electrostatic precipitator (LLT-ESP) is considered one of the mainstream technological approaches for achieving ultra-low ash emissions and has already been applied in many coal-fired power plants. Particulate matter and SO3 can both be removed by LLT-ESP. However, the removal performance of SO3 is relatively lower than that of particulate matter, which is caused by the condensation characteristics of SO3. In this paper, the condensation characteristics of SO3 were investigated on a simulated experimental system, and several measurement and characteristic methods were used to investigate mechanisms. After reducing the flue gas temperature with a heat exchanger, the size distribution of particulate matter, the mass concentration of SO3 on different sizes of particulate matter, as well as the microscopic morphology and elemental composition of particulate matter, were all experimentally studied. The results indicate that gaseous SO3 transformed into a liquid phase by heterogeneous or homogeneous condensation and then adhered to the surface of particulate matter through nucleation–condensation, collision–coalescence, and adsorption reactions. Furthermore, the removal efficiency of SO3 in LLT-ESP was also investigated under various conditions, such as ash concentration and flue gas temperature drop, suggesting that a higher ash concentration and a more significant temperature drop were beneficial for improving SO3 removal efficiency. Nevertheless, it is worth noting that the impact was limited by a further increase in ash concentration and a drop in flue gas temperature. [ABSTRACT FROM AUTHOR]

Condensable particulate matter (CPM) is different from filterable particulate matter (FPM), which could escape from air pollution control devices (APCDs) and pose a great threat to the environment and human health. Thus, modeling and experimental studies were conducted on CPM particle behavior and removal, in a cold electrode electrostatic precipitator (CE−ESP) coupled with a electric field, temperature field and concentration field. A multi−field force coupling model was then established that was based on the mechanical behavior of particles inside the CE−ESP. The results showed that temperature field was beneficial to depositing small size particles and that, the greater the temperature gradient, the higher CPM's removal efficiency. While the electric field tended to gather larger size particles, the greater the voltage provided, the higher the removal efficiency for CPM and FPM. In the multi−field, the augmented coagulation and the removal efficiencies of both CPM and FPM increased significantly, reaching 89% and 98%, respectively. Subsequently, experiments were conducted by a self−made CE−ESP device, which showed the removal efficiencies of CE−ESP of a CPM in a multi−field were 91% and 81% for a coal−fired power plant and a waste incineration plant, respectively. This research could make a great contribution to CPM condensation, aggregation and removal. [ABSTRACT FROM AUTHOR]

Coastal areas have become the primary location for nuclear power plant sites due to the convenience of seawater cooling. In China, the diffusion range of thermal discharge water has always been a hot research topic as the basis for sea use areas. The main physical process of heat loss in the numerical simulation of thermal discharge from power plants is heat exchange between the water surface and air. Currently, the methods for calculating this heat loss include the heat flux method and the water surface heat exchange coefficient method. Taking a power plant in Zhejiang as the research object, the MIKE 3 temperature–salinity module (heat flux method) and MIKE ECO Model (water surface heat exchange coefficient method) were used for modeling, and the diffusion of thermal discharge water under different modules was compared and analyzed. The results show that the calculated area of the water temperature rise envelope between the two modules differed significantly under the same conditions. The surface 4 °C temperature rise area, as calculated using ECO Model, was 45.8% smaller than that of the temperature–salinity module. The MIKE 3 temperature–salinity module can simulate the heat accumulation of water under thermal buoyancy, producing a significant thermal stratification phenomenon; the ECO module does not accurately represent the heat exchange process between the water surface and the air, and it does not adequately capture the significant vertical stratification that occurs in real-world scenarios. On this basis, this study not only lays a foundation for further exploring the impact of thermal discharge water from this powerhouse on the structure of surrounding marine biological communities and dissolved oxygen content in water bodies but also provides scientific evidence for the selection of modules when simulating thermal discharge water with the MIKE model. [ABSTRACT FROM AUTHOR]

The SO2 emissions from coal-fired power plants in China have been regulated since 2005 by a mandatory installation of flue gas desulfurization (FGD) devices. In order to verify the effectiveness of FGD systems applied in power plants, Shanxi (a province well-known for the largest coal reserves in China) was selected, and the characteristic and evolution of SO2 densities over 22 regions with large coal-fired power plants during 2005-2012 were investigated by using the satellite remote sensing data from the Ozone Monitoring Instrument (OMI). A unit-based inventory was also employed to study the trend of SO2 emissions from coal-fired power plants in Shanxi. The results show that the operation of FGD systems was successful in reducing SO2 emissions from power plants during 2005-2010: the mean SO2 densities satellite-observed over those regions with power plants operated before 2005 showed a notable decrease of approximate 0.4 DU; the mean SO2 densities over other regions with power plants newly built behind 2006 did not show a statistical increasing trend overall; the mean SO2 density over the whole Shanxi also showed a moderate decline from 2008 to 2010. However, the polluted conditions over Shanxi during 2011-2012 rebounded and the declining trend in mean SO2 density over the whole Shanxi disappeared again. In comparison of unit-based emission inventory, the emissions calculated show a similar trend with SO2 densities satellite-observed during 2005-2010 and still maintain at a lower volume during 2011-2012. By investigating the developments of other emission sources in Shanxi during 2005-2012, it is considered that the rapid expansion of industries with high coal-consumption has played an important role for the increment rise of SO2 emissions. Lack of an independent air quality monitoring network and the purposeful reduced operation rate of FGD systems occurring in some coal-fired power plants have reduced the effectiveness of SO2 emission reduction policy applied in Shanxi. In view that the SO2 pollution in Shanxi has not been well ameliorated, more reasonable and mandatory policies, such as a national-wide independent monitoring network and installation of FGD systems in other large emission sources, should be pushed out in the near future. [ABSTRACT FROM AUTHOR]

Chlorine (Cl) released from coal-fired power plants can be harmful to power equipment, the ecological environment and human health. Here, we investigated the Cl releasing characteristics from four coal-fired power plants (CFPPs) in China's Anhui province based on an ion chromatography analysis of the combustion by-production samples collected from different locations of the power plants. The results showed that Cl content in coals was low (198–367 μg·g−1), which positively correlated with the contents of lead, mercury and total sulfur, but was weakly correlated with the moisture and ash yield in coal. The releasing rate of Cl during coal combustion was highly correlated with temperature and volatile matter, and most Cl is transferred into the flue gas. Dust collector and wet flue gas devices equipped in the CFPPs were robust for removing Cl in the particulate phase, and the fabric filter showed a higher removal efficiency than the electrostatic precipitator. This study can provide theoretical support for Cl pollution control in coal-fired power plants. [ABSTRACT FROM AUTHOR]

In this work, we investigate the ability of a data assimilation technique and space-borne observations to quantify and monitor changes in nitrogen oxides (NOx) emissions over Northwestern Greece for the summers of 2018 and 2019. In this region, four lignite-burning power plants are located. The data assimilation technique, based on the Ensemble Kalman Filter method, is employed to combine space-borne atmospheric observations from the high spatial resolution Sentinel-5 Precursor (S5P) Tropospheric Monitoring Instrument (TROPOMI) and simulations using the LOTOS-EUROS Chemical Transport model. The Copernicus Atmosphere Monitoring Service-Regional European emissions (CAMS-REG, version 4.2) inventory based on the year 2015 is used as the a priori emissions in the simulations. Surface measurements of nitrogen dioxide (NO2) from air quality stations operating in the region are compared with the model surface NO2 output using either the a priori (base run) or the a posteriori (assimilated run) NOx emissions. Relative to the a priori emissions, the assimilation suggests a strong decrease in concentrations for the station located near the largest power plant, by 80% in 2019 and by 67% in 2018. Concerning the estimated annual a posteriori NOx emissions, it was found that, for the pixels hosting the two largest power plants, the assimilated run results in emissions decreased by ~40–50% for 2018 compared to 2015, whereas a larger decrease, of ~70% for both power plants, was found for 2019, after assimilating the space-born observations. For the same power plants, the European Pollutant Release and Transfer Register (E-PRTR) reports decreased emissions in 2018 and 2019 compared to 2015 (−35% and −38% in 2018, −62% and −72% in 2019), in good agreement with the estimated emissions. We further compare the a posteriori emissions to the reported energy production of the power plants during the summer of 2018 and 2019. Mean decreases of about −35% and−63% in NOx emissions are estimated for the two larger power plants in summer of 2018 and 2019, respectively, which are supported by similar decreases in the reported energy production of the power plants (~−30% and −70%, respectively). [ABSTRACT FROM AUTHOR]

The concentration of atmospheric carbon dioxide (CO2) has increased rapidly worldwide, aggravating the global greenhouse effect, and coal-fired power plants are one of the biggest contributors of greenhouse gas emissions in China. However, efficient methods that can quantify CO2 emissions from individual coal-fired power plants with high accuracy are needed. In this study, we estimated the CO2 emissions of large-scale coal-fired power plants using Orbiting Carbon Observatory-2 (OCO-2) satellite data based on remote sensing inversions and bottom-up methods. First, we mapped the distribution of coal-fired power plants, displaying the total installed capacity, and identified two appropriate targets, the Waigaoqiao and Qinbei power plants in Shanghai and Henan, respectively. Then, an improved Gaussian plume model method was applied for CO2 emission estimations, with input parameters including the geographic coordinates of point sources, wind vectors from the atmospheric reanalysis of the global climate, and OCO-2 observations. The application of the Gaussian model was improved by using wind data with higher temporal and spatial resolutions, employing the physically based unit conversion method, and interpolating OCO-2 observations into different resolutions. Consequently, CO2 emissions were estimated to be 23.06 ± 2.82 (95% CI) Mt/yr using the Gaussian model and 16.28 Mt/yr using the bottom-up method for the Waigaoqiao Power Plant, and 14.58 ± 3.37 (95% CI) and 14.08 Mt/yr for the Qinbei Power Plant, respectively. These estimates were compared with three standard databases for validation: the Carbon Monitoring for Action database, the China coal-fired Power Plant Emissions Database, and the Carbon Brief database. The comparison found that previous emission inventories spanning different time frames might have overestimated the CO2 emissions of one of two Chinese power plants on the two days that the measurements were made. Our study contributes to quantifying CO2 emissions from point sources and helps in advancing satellite-based monitoring techniques of emission sources in the future; this helps in reducing errors due to human intervention in bottom-up statistical methods. [ABSTRACT FROM AUTHOR]

This review focuses on providing the history of measurement efforts to quantify and characterize the compounds of reactive mercury (RM), and the current status of measurement methods and knowledge. RM collectively represents gaseous oxidized mercury (GOM) and that bound to particles. The presence of RM was first recognized through measurement of coal-fired power plant emissions. Once discovered, researchers focused on developing methods for measuring RM in ambient air. First, tubular KCl-coated denuders were used for stack gas measurements, followed by mist chambers and annular denuders for ambient air measurements. For ~15 years, thermal desorption of an annular KCl denuder in the Tekran® speciation system was thought to be the gold standard for ambient GOM measurements. Research over the past ~10 years has shown that the KCl denuder does not collect GOM compounds with equal efficiency, and there are interferences with collection. Using a membrane-based system and an automated system—the Detector for Oxidized mercury System (DOHGS)—concentrations measured with the KCl denuder in the Tekran speciation system underestimate GOM concentrations by 1.3 to 13 times. Using nylon membranes it has been demonstrated that GOM/RM chemistry varies across space and time, and that this depends on the oxidant chemistry of the air. Future work should focus on development of better surfaces for collecting GOM/RM compounds, analytical methods to characterize GOM/RM chemistry, and high-resolution, calibrated measurement systems. [ABSTRACT FROM AUTHOR]

The possibility to discriminate between different emission sources and between natural and anthropogenic contributions is a key issue for planning efficient air pollution reduction and mitigation strategies. Moreover, the knowledge of the particulate matter (PM) chemical composition for the different size fractions is recognized as increasingly important, in particular with respect to health effects of exposed population. This study is focused on the characterization of PM10 and PM2.5 main sources located in the Civitavecchia harbor-industrial area (Central Italy), namely a large coal-fired power plant, a natural gas power plant, the harbor area, the vehicular traffic (due to both the local traffic and the highway crossing the area) and small industrial activities. The approach was based on PM10/PM2.5 samples monthly collected for one year and a further relative chemical characterization of organic and inorganic fractions. Wind-select sensors, allowing a selective PM10 and PM2.5 sampling downwind to specific emission sources, were used for the overall sampling. This methodology manages to explain specific emission patterns and to assess the concentration levels of the micro pollutants emitted by local sources and particularly toxic for health. A descriptive statistical analysis of data was performed, also verifying the occurrence of legislative threshold exceedances. Moreover, in order to highlight the contribution of specific sources, the differences in the measured micro pollutants concentrations between wind directions, PM size fractions and sampling sites have been investigated, as well as the seasonal trends of pollutants concentrations. These results allow to highlight that the applied methodology represents a valid support in source apportionment studies. [ABSTRACT FROM AUTHOR]

We report on the continuous ambient measurements of total gaseous mercury (TGM) and several ancillary air quality parameters that were collected in Colorado Springs, CO. This urban area, which is located adjacent to the Front Range of the Rocky Mountains, is the second largest metropolitan area in Colorado and has a centrally located coal-fired power plant that installed mercury (Hg) emission controls the year prior to our study. There are few other Hg point sources within the city. Our results, which were obtained from a measurement site < 1 km from the power plant, show a distinct diel pattern in TGM, with peak concentrations occurring during the night (1.7 ± 0.3 ng m−3) and minimum concentrations mid-day (1.5 ± 0.2 ng m−3). The TGM concentrations were not correlated with wind originating from the direction of the plant or with sulfur dioxide (SO2) mixing ratios, and they were not elevated when the atmospheric mixing height was above the effective stack height. These findings suggest that the current Hg emissions from the CFPP did not significantly influence local TGM, and they are consistent with the facility's relatively low reported annual emissions of 0.20 kg Hg per year. Instead, variability in the regional signal, diurnal meteorological conditions, and/or near-surface emission sources appears to more greatly influence TGM at this urban site. [ABSTRACT FROM AUTHOR]

Anhui is one of the highest provincial emitters of air pollutants in China due to its large coal consumption in coal-fired plants. In this study, the total emissions of nitrogen oxides (NOx), sulfur dioxide (SO2) and particulate matter (PM) from coal-fired power plants in Anhui were investigated to assess the impact of control measures on the atmospheric emissions based upon continuous emission monitoring systems (CEMS). The total NOx, SO2 and PM emissions significantly decreased from 2013 to 2017 and they were estimated at 24.5 kt, 14.8 kt and 3.0 kt in 2017, respectively. The emission reductions of approximately 79.0%, 70.1% and 81.2% were achieved in 2017 compared with a 2013 baseline, respectively, due to the application of high-efficiency emission control measures, including the desulfurization, denitration and dust-removing devices and selective catalytic reduction (SCR). The NOx, SO2 and PM emission intensities were 0.125 g kWh−1, 0.076 g kWh−1 and 0.015 g kWh−1 in 2017, respectively, which were lower than the average of national coal-fired units. The coal-fired units with ≥600 MW generated 80.6% of the total electricity amount while they were estimated to account for 70.5% of total NOx, 70.1% of total SO2 and 71.9% of total PM. Their seasonal emissions showed a significant correlation to the power generation with the maximum correlation found in summer (July and August) and winter (January and December). The major regional contributors are the cities along the Huai River Basin and Yangtze River Basin, such as Huainan, Huaibei, Tongling, Maanshan and Wuhu, and the highest emission occurred in Huainan, accounting for approximately 26–40% of total emission from all the power plants. Our results indicated that the application of desulfurization, denitration and dust-removing devices has played an important role in controlling air pollutant emissions from coal-fired power plants. [ABSTRACT FROM AUTHOR]