Efficient and selective removal of Hg(II) from water using recyclable hierarchical MoS2/Fe3O4 nanocomposites.

Developing practical and cost-effective adsorbents with satisfactory mercury (Hg) remediation capability is indispensable for aquatic environment safety and public health. Herein, a recyclable hierarchical MoS2/Fe3O4 nanocomposite (by in-situ growth of MoS2 nanosheets on the surface of Fe3O4 nanospheres) is presented for the selective removal of Hg(II) from aquatic samples. It exhibited high adsorption capacity (∼1923.5 mg g -1), fast kinetics (k2 ∼ 0.56 mg g -1 min-1), broad working pH range (2-11), excellent selectivity (Kd > 1.0 × 107 mL g -1), and great reusability (removal efficiency > 90% after 20 cycles). In particular, removal efficiencies of up to ∼97% for different Hg(II) concentrations (10-1000 µg L -1) in natural water and industrial effluents confirmed the practicability of MoS2/Fe3O4. The possible mechanism for effective Hg(II) removal was discussed by a series of characterization analyses, which was attributed to the alteration of the MoS2 structure and the surface coordination of Hg-S. The accessibility of surface sulfur sites and the diffusion of Hg(II) in the solid-liquid system were enhanced due to the advantage of the expanded interlayer spacing (0.96 nm) and the hierarchical structure. This study suggests that MoS2/Fe3O4 is a promising material for Hg(II) removal in actual scenarios and provides a feasible approach by rationally constructing hierarchical structures to promote the practical applications of MoS2 in sustainable water treatments.

Isotopic Fractionation Characteristics of Speciated Mercury from Local Biomass Combustion in the Tibetan Plateau.

As the Third Pole of the world, the Tibetan Plateau (TP) is sensitive to anthropogenic influences. Biomass combustion is one of the most important anthropogenic sources of mercury (Hg) emissions in the TP. However, due to the lack of knowledge about Hg emission characteristics and activity levels in the plateau, atmospheric Hg emissions from biomass combustion in the TP are under large uncertainties. Here, based on pilot-scale experiments, we found that particle-bound mercury (PBM; mean of 83.1-87.7 ng/m3) occupied 17.93-49.31% of the total emitted Hg and the PBM δ202Hg values (average -1.65‰ to -0.77‰) were significantly higher than those of the corresponding feeding biomass. The Δ200Hg values of total gaseous mercury and PBM were more negative (-0.08‰ to -0.05‰) than other anthropogenic emissions, providing unique isotopic fingerprints for this sector. Together with the investigated local activity levels, Hg emissions from biomass combustion reached 402 ± 74 kg/a, which were dozens of times higher than previous estimates. The emissions were characterized by conspicuous spatial heterogeneity, concentrated in the northern and central TP. Specialized Hg emissions and the Hg isotope fingerprint of local biomass combustion can aid in evaluating the influence of this sector on the fragile ecosystems of the TP.

Mercury emission characteristics and mechanism in the raw mill system of cement clinker production.

Mercury pollution has attracted worldwide attention due to its toxicity, bioaccumulation and persistence. Cement clinker production is the top emitter of atmospheric mercury in China and the emissions from raw mill systems account for about 85% of all emissions. However, the mercury emission characteristics and mechanisms as a function of time during an operation cycle are still unclear. This study aims to reveal the mercury emission characteristics and mechanisms in cement plants by comprehensively using offline and online field measurements, control experiments and heat transfer analysis. Research results indicated that an intermediate temperature (300-500 °C) desorption and the heterogeneous oxidation of mercury in the precalciner, the selective adsorption of oxidized gaseous mercury (Hg2+) to raw meal, and Hg2+ re-vaporization in the conditioning tower jointly caused an increase in the Hg2+ ratio (15.3%-83.6%) during the mill-off mode. In addition, mercury concentrations remained at approximately 6.5 µg/Nm3 during the mill-on mode while the values reached a peak of 1835.4 µg/Nm3 during the mill-off mode. Thus, atmospheric mercury emissions during the mill-off mode accounted for 35.0%- 71.7% of the emissions during the entire cycle, although the mill-off period only lasted for 5%- 17% of the whole cycle. Our results therefore suggest that supervisory monitoring of mercury in cement clinker production should specify the operating status of raw mills. Mercury control technologies targeting a relatively short period for the mill-off mode can substantially reduce mercury emissions from cement clinker production, and thus, the related impacts on ecosystems and human health.

Elevated Gaseous Oxidized Mercury Revealed by a Newly Developed Speciated Atmospheric Mercury Monitoring System.

Gaseous oxidized mercury (Hg2+) monitoring is one of the largest challenges in the mercury research field, where existing methods cannot simultaneously satisfy the measurement requirements of both accuracy and time precision, especially in high-particulate environments. Here, we verified that dual-stage cation exchange membrane (CEM) sampler is incapable of gaseous elemental mercury (Hg0) uptake even if particulate matter is trapped on CEM, whereas the Hg2+ capture efficiency of the sampler is more than 90%. We then developed a Cation Exchange Membrane-Coupled Speciated Atmospheric Mercury Monitoring System (CSAMS) by coupling the dual-stage CEM sampler with the commercial Tekran 2537/1130/1135 system and configuring a new sampling and analysis procedure, so as to improve the monitoring accuracy of Hg2+ and ensure the simultaneous measurement of Hg0, Hg2+, and Hgp in 2 h time resolution. We deployed the CSAMS in urban Beijing in September 2021 and observed an unprecedented elevated Hg2+ during the daytime with an average amplitude of 510 pg m-3. Using a zero-dimensional box model, the elevated Hg2+ production rate was attributed to high atmospheric oxidant concentrations, Hg0 heterogeneous and interfacial oxidation processes on the surface of atmospheric particles, or potential unknown oxidants.

Theoretical insight on electronic structure and photophysical properties of a series of cyclometalated iridium(III) complexes bearing the substituted phenylpyrazole with different electron-donating or electron-accepting groups.

By using the density functional theory (DFT) and time-dependent density functional theory (TDDFT), the electronic structure and photophysical properties of a series of cyclometalated iridium(III) complexes bearing the substituted phenylpyrazole have been theoretically investigated. All studied iridium(III) complexes have the distorted octahedral geometry with cis-C,C, cis-O,O, and trans-N,N chelate disposition. The lowest lying singlet → singlet absorptions of all studied iridium(III) complexes are respectively located at 405 nm, 387 nm, 382 nm, 370 nm, and 387 nm. The calculated emission wavelengths for all studied iridium(III) complexes are 654 nm, 513 nm, 506 nm, 505 nm and 499 nm, respectively. The calculated emission wavelength for complex 4 at the CAM-B3LYP level is in good agreement with the experimental value. From the theoretical results, it can be seen that the electron-donating substituent groups have the important effect on the electronic structure and photophysical properties of all studied iridium(III) complexes. We hope that this study can provide valuable guidance for the design of new phosphorescent organic light-emitting diodes (OLEDs) materials.

Effect of the Coal Preparation Process on Mercury Flows and Emissions in Coal Combustion Systems.

Coal preparation is effective in controlling primary mercury emissions in coal combustion systems; however, the combustion of coal preparation byproducts may cause secondary emissions. The inconsistent coal preparation statistics, unclear mercury distribution characteristics during coal preparation, and limited information regarding the byproduct utilization pathways lead to great uncertainty in the evaluation of the effect of coal preparation in China. This study elucidated the mercury distribution in coal preparation based on the activity levels of 2886 coal preparation plants, coal mercury content database, tested mercury distribution factors of typical plants, and then traced the mercury flows and emissions in the downstream sectors using a cross-industry mercury flow model. We found that coal preparation altered the mercury flows by reducing 68 tonnes of mercury to sectors such as coking and increasing the flows to byproduct utilization sectors. Combusting cleaned coal rather than raw coal reduced the mercury emissions by 47 tonnes; however, this was offset by secondary mercury emissions. Coal gangue spontaneous combustion and the cement kiln coprocessing process were dominant secondary emitters. Our results highlight the necessity of whole-process emission control of atmospheric mercury based on flow maps. Future comprehensive utilization of wastes in China should fully evaluate the potential secondary mercury emissions.

Highly Resolved Inventory of Mercury Release to Water from Anthropogenic Sources in China.

This study developed an up-to-date and point-source-based inventory of mercury (Hg) releases to water in China by applying probabilistic release factors that combined industry removal efficiencies, reuse of reclaimed water, and receiving water types. In 2017, the national mercury release to water was estimated to be 50 (35-66) tons, in which 47%, 8%, 7%, and 25% were from nonferrous metal smelting, vinyl chloride monomer (VCM) production, coal-fired boilers, and domestic sewage, respectively. Approximately 95% of mercury was released to inland rivers, and the rest was discharged to lakes or coastal water. The significant sources were identified based on their mercury releases to water. The control of mercury release to water in China shall focus on zinc smelting plants, municipal sewage treatment plants, and the VCM production process. For zinc smelting plants, China can tighten the limit of mercury concentration in discharged wastewater and combine Hg-catcher device in traditional integrated treatment. For municipal sewage treatment plants and the VCM production process, promoting processes of Hg-free production can reduce mercury inputs at the source. Our study provides insights for other parties to identify the relevant sources of mercury release to water and to conduct control measures, so as to promote the global convention implementation.

Potential environmental risk of trace elements in fly ash and gypsum from ultra-low emission coal-fired power plants in China.

The ultra-low emission retrofitting (ULE) in China's coal-fired power plants (CFPPs) enhances removal efficiencies of trace elements, which may increase their contents in fly ash and gypsum. However, their potential environmental risks in these wastes have been scarcely evaluated. Experiments indicated that the trace elements in fly ash and gypsum accounted for approximately 92.9-98.2% of the total outputs. Most trace elements in these wastes existed mainly as mobile/leachable forms, except for the Hg in fly ash (residual form). We comprehensively evaluated the potential environmental risks of trace elements in fly ash and gypsum from ULE CFPPs in China using a modified risk assessment approach that integrates a trace element enrichment model for waste, and chemical speciation datasets. We found that nationally, trace elements in gypsum represented low levels of potential risk, even after ULE. However, the potential moderate environmental risk of fly ash has aroused attention because of trace element pollution, where Hg and Cd contributed the major risks. The relatively high risks from fly ash are mainly distributed in Guangxi, Hunan and Hebei provinces. The disposal of fly ash in these areas should be given special attention in the future.

Ozone pollution mitigation in guangxi (south China) driven by meteorology and anthropogenic emissions during the COVID-19 lockdown.

With the implementation of COVID-19 restrictions and consequent improvement in air quality due to the nationwide lockdown, ozone (O3) pollution was generally amplified in China. However, the O3 levels throughout the Guangxi region of South China showed a clear downward trend during the lockdown. To better understand this unusual phenomenon, we investigated the characteristics of conventional pollutants, the influence of meteorological and anthropogenic factors quantified by a multiple linear regression (MLR) model, and the impact of local sources and long-range transport based on a continuous emission monitoring system (CEMS) and the HYSPLIT model. Results show that in Guangxi, the conventional pollutants generally declined during the COVID-19 lockdown period (January 24 to February 9, 2020) compared with their concentrations during 2016-2019, while O3 gradually increased during the resumption (10 February to April 2020) and full operation periods (May and June 2020). Focusing on Beihai, a typical Guangxi region city, the correlations between the daily O3 concentrations and six meteorological parameters (wind speed, visibility, temperature, humidity, precipitation, and atmospheric pressure) and their corresponding regression coefficients indicate that meteorological conditions were generally conducive to O3 pollution mitigation during the lockdown. A 7.84 µg/m3 drop in O3 concentration was driven by meteorology, with other decreases (4.11 µg/m3) explained by reduced anthropogenic emissions of O3 precursors. Taken together, the lower NO2/SO2 ratios (1.25-2.33) and consistencies between real-time monitored primary emissions and ambient concentrations suggest that, with the closure of small-scale industries, residual industrial emissions have become dominant contributors to local primary pollutants. Backward trajectory cluster analyses show that the slump of O3 concentrations in Southern Guangxi could be partly attributed to clean air mass transfer (24-58%) from the South China Sea. Overall, the synergistic effects of the COVID-19 lockdown and meteorological factors intensified O3 reduction in the Guangxi region of South China.

Distribution and emissions of trace elements in coal-fired power plants after ultra-low emission retrofitting.

Various hazardous trace elements emitted from anthropogenic activities are attracting increasing public awareness. This study comprehensively explored the distribution and emissions of trace elements in coal-fired power plants (CFPPs) after ultra-low emission retrofitting by conducting field experiments, literature surveys, and model calculations. High levels of volatile Hg and semi-volatile As/Pb were mainly observed in fly ash and gypsum (96.6%-98.5%), while the proportion of non-volatile Cr in bottom ash was 9.23%. The Hg and As/Pb removal efficiencies were remarkably improved by ultra-low emission retrofitting, increasing by 5.67% and 2.08%/2.63%, respectively. However, ULE retrofitting only slightly affected (0.17%) non-volatile elements. These improvements were mainly attributed to the low-low-temperature electrostatic precipitator. Owing to the enhanced particle-capturing efficiencies, the concentrations of trace elements in the emitted gas of the tested CFPPs were low, ranging from 0.21-1.50 µg/m3, but accounted for a high proportion of the gas phase (61.8%-100%). Based on the national database of coal quality and their behaviour in CFPPs, we found that most of the concentrations of trace elements emitted from Chinese CFPPs were significantly lower than the internationally existing emission limits. However, owing to the skewed distribution characteristics of the emitted concentrations, we suggest issuing or revising the corresponding emission limits and improving the control of intense trace element pollution in China.

Impact of emission reductions and meteorology changes on atmospheric mercury concentrations during the COVID-19 lockdown.

Controlling anthropogenic mercury emissions is an ongoing effort and the effect of atmospheric mercury mitigation is expected to be impacted by accelerating climate change. The lockdown measures to restrict the spread of Coronavirus Disease 2019 (COVID-19) and the following unfavorable meteorology in Beijing provided a natural experiment to examine how air mercury responds to strict control measures when the climate becomes humid and warm. Based on a high-time resolution emission inventory and generalized additive model, we found that air mercury concentration responded almost linearly to the changes in mercury emissions when excluding the impact of other factors. Existing pollution control and additional lockdown measures reduced mercury emissions by 16.7 and 12.5 kg/d during lockdown, respectively, which correspondingly reduced the concentrations of atmospheric mercury by 0.10 and 0.07 ng/m3. Emission reductions from cement clinker production contributed to the largest decrease in atmospheric mercury, implying potential mitigation effects in this sector since it is currently the number one emitter in China. However, changes in meteorology raised atmospheric mercury by 0.41 ng/m3. The increases in relative humidity (9.5%) and temperature (1.2 °C) significantly offset the effect of emission reduction by 0.17 and 0.09 ng/m3, respectively, which highlights the challenge of air mercury control in humid and warm weather and the significance of understanding mercury behavior in the atmosphere and at atmospheric interfaces, especially the impact from relative humidity.

Long-term study of heavy metal pollution in the northern Hangzhou Bay of China: temporal and spatial distribution, contamination evaluation, and potential ecological risk.

Coastal ecosystem is vulnerable to heavy metal contamination. The northern Hangzhou Bay is under intensifying impact of anthropogenic activities. To reveal the heavy metal pollution status in the coastal environment of the Hangzhou Bay, a long-term investigation into the heavy metal contamination during 2011 to 2016 was initiated. Seawater and sediment samples of 25 locations depending on the sewage outlet locations in the northern Hangzhou Bay were collected to analyze the concentrations and temporal and spatial distribution of Cu, Pb, Zn, Cd, Hg, and As. Pollution condition, ecological risk, and potential sources were additionally analyzed. Results show that the annual mean concentrations of Cu, Pb, Zn, Cd, Hg, and As were 2.13-4.59, 0.212-1.480, 7.81-20.34, 0.054-0.279, 0.026-0.090, and 1.08-2.57 µg/L in the seawater, and were 16.34-28.35, 16.25-26.33, 67.32-97.61, 0.084-0.185, 0.029-0.061, and 6.09-14.08 µg/L in the sediments. A decreasing trend in Cu, Pb, Zn, Cd, and Hg concentrations and an increasing trend in As of the seawater were observed. However, in the sediment, the heavy metals demonstrated a rising trend, except for Hg. The single-factor pollution index showed an increasing trend in Cd and As in the seawater, depicting an enhanced pollution of Cd and As, while in the sediments, Cu, Pb, and As were in pollution-free level (average Geo-accumulation index (Igeo) values below 0) in general, and only occasional slight pollution occurred in individual years, e.g., As with 0.403 in 2016. The mean Igeo values of Cd ranged from - 0.865 to 0.274 during 2011 to 2016, indicating that the pollution level of Cd was slight, but is likely to increase in the forthcoming years. The level of heavy metal contamination in sediments was low in 2011 (5.853) and 2012 (5.172), and moderate during 2013 to 2016 (in the range of 6.107 to 7.598), while the degree of potential ecological risk was low in the study period, except moderate in 2013 (125.107). The highest contamination degree and potential ecological risk appeared in 2013 (Cd = 7.598; RI = 125.107), while Cd and Hg contributed over 75% of the ecological risk. Overall, the results show low pollution level and low potential ecological risk in the northern Hangzhou Bay; however, more attention should be paid to the potential ecological risk due to Hg and Cd. Graphical abstract Spatial distribution of the heavy metal levels in the sediment of the coastal environment of the northern Hangzhou Bay on a long-term basis.

Improving VOCs control strategies based on source characteristics and chemical reactivity in a typical coastal city of South China through measurement and emission inventory.

In China, the corresponding control directives for volatile organic compounds (VOCs) have been based on primary emissions, rarely considering reactive speciation. To seek more effective VOCs control strategies, we investigated 107 VOC species in a typical coastal city (Beihai) of South China, from August to November 2018. Meanwhile, a high-resolution anthropogenic VOCs monthly emission inventory (EI) was established for 2018. For source apportionments (SAs) reliability, comparisons of source structures derived from positive matrix factorization (PMF) and EI were made mainly in terms of reaction losses, uncertainties and specific ratios. Finally, for the source-end control, a comprehensive reactivity control index (RCI) was established by combing SAs with reactive speciation profiles. Ambient measurements showed that the average concentration of VOCs was 26.38 ppbv, dominated by alkanes (36.7%) and oxygenated volatile organic compounds (OVOCs) (29.4%). VOC reactivity was estimated using ozone formation potential (52.35 ppbv) and propylene-equivalent concentration (4.22 ppbv). EI results displayed that the entire VOC, OFP, and propylene-equivalent emissions were 40.98 Gg, 67.98 Gg, and 105.93 Gg, respectively. Comparisons of source structures indicated that VOC SAs agreed within ±100% between two perspectives. Both PMF and EI results showed that petrochemical industry (24.0% and 33.0%), food processing and associated combustion (19.1% and 29.2%) were the significant contributors of anthropogenic VOCs, followed by other industrial processes (22.2% and 13.3%), transportation (18.9% and 12.0%), and solvent utilization (9.1% and10.5%). Aimed at VOCs abatement according to RCI: for terminal control, fifteen ambient highly reactive species (predominantly alkenes and alkanes) were targeted; for source control, the predominant anthropogenic sources (food industry, solvent usage, petrochemical industry and transportation) and their emitted highly reactive species were determined. Particularly, with low levels of ambient VOC and primary emissions, in this VOC and NOx double-controlled regime, crude disorganized emission from food industry contributed a high RCI.

Possible environmental effects on the spread of COVID-19 in China.

At the end of 2019, a novel coronavirus, designated as SARS-CoV-2, emerged in Wuhan, China and was identified as the causal pathogen of COVID-19. The epidemic scale of COVID-19 has increased dramatically, with confirmed cases increasing across China and globally. Understanding the potential affecting factors involved in COVID-19 transmission will be of great significance in containing the spread of the epidemic. Environmental and meteorological factors might impact the occurrence of COVID-19, as these have been linked to various diseases, including severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), whose causative pathogens belong to the same virus family as SARS-CoV-2. We collected daily data of COVID-19 confirmed cases, air quality and meteorological variables of 33 locations in China for the outbreak period of 29 January 2020 to 15 February 2020. The association between air quality index (AQI) and confirmed cases was estimated through a Poisson regression model, and the effects of temperature and humidity on the AQI-confirmed cases association were analyzed. The results show that the effect of AQI on confirmed cases associated with an increase in each unit of AQI was statistically significant in several cities. The lag effect of AQI on the confirmed cases was statistically significant on lag day 1 (relative risk (RR) = 1.0009, 95% confidence interval (CI): 1.0004, 1.0013), day 2 (RR = 1.0007, 95% CI: 1.0003, 1.0012) and day 3 (RR = 1.0008, 95% CI: 1.0003, 1.0012). The AQI effect on the confirmed cases might be stronger in the temperature range of 10 °C ≤ T < 20 °C than in other temperature ranges, while the RR of COVID-19 transmission associated with AQI was higher in the relative humidity (RH) range of 10% ≤ RH < 20%. Results may suggest an enhanced impact of AQI on the COVID-19 spread under low RH.

Impact of VOCs emission from iron and steel industry on regional O3 and PM2.5 pollutions.

Iron and steel industry emission is an important industrial source of air pollution. However, little is known about the relationship between volatile organic compounds (VOCs) emitted and regional air pollution. In this study, VOCs emissions from a typical iron and steel plant in Yangtze River Delta (YRD, China) were monitored from April 2018 to March 2019. The ozone formation potential (OFP) and secondary organic aerosol (SOA) formation of VOCs were calculated to reveal the influence of VOCs emissions on regional ozone and particulate pollution, and the sensitivity analysis approach was performed to explore the qualitative and quantitative relationships between VOCs and O3, as well as VOCs and PM2.5. The VOCs concentration was 93.76 ± 266.97 ppbv during the study. The OFP was 760.08 ± 2391.90 µg m-3, and aromatics were the predominant precursors, contributing 54.05% of the total OFP. Furthermore, the SOA estimated by fractional aerosol coefficient (FAC) and time-resolved (TR) methods were 6.032 ± 13.347 µg m-3 and 0.971 ± 4.650 µg m-3, accounting for 8.65-26.39% (13.78 ± 7.46%) and 1.55-4.20% (2.22 ± 1.23%) of the PM2.5 concentrations, respectively. The results indicated that VOCs were more sensitive to O3 pollution in high pollution domains, whereas VOCs were more sensitive to PM2.5 pollution in low pollution domains. We concluded that reducing VOCs emissions might be effective in alleviating photochemical pollution episodes in areas around iron and steel industry, and the haze pollution occurred in these regions may be caused by the primary emission of PM, and the contribution of SOA was relatively small.

A sensitive and rapid bacterial antibiotic susceptibility test method by surface enhanced Raman spectroscopy.

This study aims to develop a rapid bacterial antibiotic susceptibility test (AST) method by Bacteria-aptamer@AgNPs-surface enhanced Raman spectroscopy (SERS) and further evaluate the influence of different antibiotics on the Raman intensity of bacteria. The Raman intensity of Escherichia coli O157:H7 (E. coli O157:H7) and Staphylococcus aureus (S. aureus) in the presence of different concentrations of antibiotics in 2 h was detected by Bacteria-aptamer@AgNPs-SERS in this study. Our results found that the bacteria Raman signal peak at 735 cm-1 and the minimum inhibitory concentration (MIC) value was determined in 1 h according to Raman signals. In 2 h, the bacteria Raman signal growth at sub-MIC concentrations of four different kinds of antibiotics and the bacteria colony-forming unit (CFU) have similar enhancements. SERS utilizes special functions of rough metal surfaces and offers a huge enhancement of Raman intensities with reduced fluorescence backgrounds, which makes it an ultrasensitive tool of detection. This rapid AST method and the enhancement effect should be of value in search of new antibiotic drugs.

Theoretical perspective on the electronic structure and photophysical properties for a series of mixed-carbene tris-cyclometalated iridium(iii) complexes.

The electronic structure and photophysical properties of four mixed-carbene tris-cyclometalated iridium(iii) complexes have been theoretically investigated by the density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. The effect of varying the main ligand by introducing different ring structures on the photophysical properties of the studied complexes has been explored. All studied complexes have slightly distorted octahedral geometries. The complex with a rigid skeletal structural main ligand possesses the smallest difference between the recombination energy of hole transport and recombination energy of electron transport among these complexes, enhancing the charge transfer balance. The lowest energy emission wavelength calculated is in very good agreement with the available experimental value. This study will provide useful information for the design of new phosphorescent organic light-emitting diode (OLED) materials.

Characteristics and health risk assessment of volatile organic compounds (VOCs) in restaurants in Shanghai.

Volatile organic compounds (VOCs) are important precursors of ozone and atmospheric particulates that have attracted extensive attention worldwide. Cooking emissions, the chemical characteristics of which vary dramatically due to different cooking styles, are a main source of ambient VOCs, especially in large cities. This research focused on the emission characteristics of VOCs from six types of restaurants in Shanghai: hot pot (HP), Sichuan cuisine (SC), Cantonese cuisine (CS), seafood (SF), Western fast food (WFF), and authentic Shanghai cuisine (ASC). It was found that HP, which discharged cooking fumes indoors, produced the highest mass concentration of VOCs (1900.2 ± 364.8 µg m-3), followed by SC (1403.7 ± 403.8 µg m-3), WFF (656.0 ± 156.9 µg m-3), SF (638.6 ± 145.1 µg m-3), CC (632.7 ± 127.7 µg m-3), and ASC (612.3 ± 51.3 µg m-3), the cooking fumes from which were collected by emission extraction stacks. Additionally, the VOC species from each cuisine were mainly low carbon substances. Alkanes were the major VOC pollutants from all six cuisines, accounting for 34.4-71.7%. The coefficient divergence values were 0.287-0.593, suggesting that there were differences between the cuisines in the present study. Ozone formation potential and secondary organic aerosol formation potential indicated that O-VOCs and aromatics were the largest contributors. Health risk assessment of VOCs via non-carcinogenic risk values (HQ) and carcinogenic risk values (RISK) indicated that frying, grilling, and stir-frying had relatively large impacts on human health. VOCs collected in emission extraction stacks were significantly higher risk compared with those in the indoor environment, but the RISK score of the HP restaurant was larger, second only to SC. The HQ and RISK values of 1,3-butadiene, acetaldehyde, and trichloroethylene in the HP restaurant all exceeded US EPA standards, indicating that long-term exposure in an HP restaurant would have a significant impact on human health and might carry a potential cancer risk.

Theoretical insight into the photophysical properties of six heteroleptic Ir(iii) phosphorescent complexes bearing ppy-type ligands.

By using density functional theory and time-dependent density functional theory, the geometrical, electronic and photophysical properties of six complexes with two ppy-type ligands and one acetylacetone anion around the Ir center have been explored. The lowest energy absorption wavelengths are located at 414 nm for 1, 434 nm for 2, 434 nm for 3, 421 nm for 4, 436 nm for 5, and 425 nm for 6, respectively. The lowest energy emissions of these complexes are localized at 617, 492, 633, 634, 491 and 491 nm, respectively, for complexes 1-6, simulated in CH2Cl2 medium at the M062X level. The calculated lowest lying absorption wavelength and the lowest energy emission wavelength for complex 3 are very close to the available experimental values. The position and number of the incorporated electron-withdrawing fluorine substituents have some effect on the electronic and photophysical properties of these studied complexes.

Emission characteristics of fine particulate matter from ultra-low emission power plants.

As one of the highest energy consuming and polluting industries, the power generation industry is an important source of particulate matter emissions. Recently, implementation of ultra-low emission technology has changed the emission characteristic of fine particulate matter (PM2.5). In this study, PM2.5 emitted from four typical power plants in China was sampled using a dilution channel sampling system, and analyzed for elements, water-soluble ions and carbonaceous fractions. The results showed that PM2.5 concentrations emitted from the four power plants were 0.78 ±â€¯0.16, 0.63 ±â€¯0.09, 0.29 ±â€¯0.07 and 0.28 ±â€¯0.01 mg m-3, respectively. Emission factors were 0.004-0.005 g/kg coal, nearly 1-2 orders of magnitude lower than those reported in previous studies. The highest proportions of PM2.5 consisted of organic carbon (OC), SO42-, elemental carbon (EC), NH4+, Al and Cl-. Coefficients of divergence (CDs) were in the ranges 0.22-0.41 (for an individual plant), 0.43-0.69 (among different plants), and 0.60-0.99 (in previous studies). The results indicated that the source profiles of each tested power plant were relatively similar, but differed from those in previous studies. Enrichment factors showed elevated Se and Hg, in accordance with the source markers Se and As. Comparing source profiles with previous studies, the proportion of OC, EC and NH4+ were higher, while the proportion of Al in PM2.5 were relatively lower. The OC/EC ratio became concentrated at ∼5. Results from this study can be used for source apportionment and emission inventory calculations after implementation of ultra-low emission technologies.