Unintentional persistent organic pollutants in cremation process: Emissions, characteristics, and inventory.

Pollutants produced by cremation furnaces have gradually caused concern because of the increasing rate of cremation around the world. In this study, the levels, patterns, and emission factors of unintentional persistent organic pollutants (UPOPs) from cremation were investigated. The toxic equivalent (TEQ) concentrations (11 % O2 normalized) of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in flue gas ranged from 0.036 to 22 ng TEQ/Nm3, while the levels of polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs) in flue gas samples ranged from 0.0023 to 1.2 ng TEQ/Nm3 and 0.17-44 pg TEQ/Nm3, respectively. The average concentrations of UPOPs in flue gas from car-type furnaces were higher than those from flat-panel furnaces. Secondary chambers and air pollution control devices were effective for controlling UPOPs emissions. However, heat exchangers were not as effective for reducing UPOPs emissions. It was observed that the UPOPs profiles exhibited dissimilarities between fly ash and flue gas samples. HxCDF, OCDD, and PeCDF were the dominant homologs of PCDD/Fs in flue gas, while HxCDF, PeCDF, and HpCDF were the dominant homologs in fly ash. The fractions of MoCBs and MoCNs in fly ash were higher than those in flue gas. Finally, we conducted an assessment of the global emissions of UPOPs from cremation in the years of 2019 and 2021. The total emission of UPOPs in 47 countries was estimated at 239 g TEQ in 2021, which was during the peak period of the COVID-19 pandemic worldwide. The emissions in 2021 increased by approximately 24 % compared to 2019, with the impact of COVID-19 being a significant factor that cannot be disregarded.

Identification and verification of PCDD/Fs indicators from four typical large-scale municipal solid waste incinerations with large sample size in China.

Monitoring PCDD/Fs emissions from municipal solid waste incinerations (MSWIs) is of paramount importance, yet it can be time-consuming and labor-intensive. Predictive models offer an alternative approach for estimating their levels. However, robust models specific to PCDD/Fs were lacking. In this study, we collected 190 PCDD/Fs samples from 4 large-scale MSWIs in China, with the average PCDD/Fs levels and TEQ levels of 0.987 ng/m3 and 0.030 ng TEQ/m3, respectively. We developed and evaluated predictive models, including traditional statistical methods, e.g., linear regression (LR) as well as machine learning models such as back propagation-artificial neural networks (BP ANN) and random forest (RF). Correlation analysis identified 2,3,4,7,8-PeCDF, 1,2,3,6,7,8-HxCDF, 2,3,4,6,7,8-HxCDF were better indicator congeners for PCDD/Fs estimation (R2 > 0.9, p < 0.001). The predictive results favored the RF model, exhibiting a high R2 value and low root mean square error (RMSE) and mean absolute error (MAE). Additionally, the RF model showed excellent prediction ability during external validation, with low absolute relative error (ARE) of 10.9 %-12.6 % for the three indicator congeners in the normal PCDD/F TEQ levels group (<0.1 ng TEQ/m3) and slightly higher ARE values (13.8 %-17.9 %) for the high PCDD/F TEQ levels group (>0.1 ng TEQ/m3). In conclusion, our findings strongly support the RF model's effectiveness in predicting PCDD/Fs TEQ emission from MSWIs.

[Pollution Characteristics and Emission Factors of PCDD/Fs from Iron and Steel Industry].

The pollution level, emission characteristics, and emission factors of PCDD/Fs from a number of steel plants were investigated in a particular province of China. The results showed that the concentration of PCDD/Fs was at a low level and decreased by 1-2 orders of magnitude compared with that in 2005-2019. In detail, the concentrations of PCDD/Fs ranged from 0.003-0.557 ng·m-3(I-TEQ), and the mean value was 0.165 ng·m-3 for the sintering process. Moreover, the concentrations of PCDD/Fs ranged from 0.006 to 0.057 ng·m-3, and the mean value was 0.025 ng·m-3 for the electric furnace process. In addition, the concentration of PCDD/Fs in the iron and steel industry from 2005 to 2020 increased first and then decreased, especially after the implementation of the new emission standard and the ultra-low emission control of conventional pollutants such as smoke, showing a significant decline. The results of fingerprint analysis showed that 2,3,7,8-TCDF was the largest congener contributing to the mass concentration, and lower chlorinated PCDFs were increased. This result differed from those of previous studies in which highly chlorinated PCDFs and PCDDs dominated, indicating that the generation source of PCDD/Fs had changed. The congener and isomer profiles of PCDD/Fs in flue gas from the sintering process were similar to those in the flue gas from the electric furnace process. Additionally, showing the characteristics of the typical high-temperature thermal process, the de novo synthesis may be the dominant mechanism of formation of PCDD/Fs in the sintering process and electric furnace process. The emission factor was 0.003-0.5 µg·t-1 (I-TEQ), and the average emission factor was (0.18±0.22) µg·t-1 for the sintering process. The emission factor was 0.04-0.5 µg·t-1, and the average emission factor was (0.27±0.23) µg·t-1 for the electric furnace process. These values were far lower than those of the standard toolkit for identification and quantification of dioxin and furan emissions released by UNEP in 2013 and the emission factors in the dioxin emission inventory of China in 2004. It is suggested that the emission factors of PCDD/Fs in the iron and steel industry of China should be studied and updated.

[Analysis of Ozone Pollution Spatio-temporal Evolution Characteristics and Identification of Its Long-term Variation Driving Factor over Hunan Province].

Despite the alleviation of particulate matter (PM), the ambient ozone (O3) concentration is continuously increasing in Hunan province where the investigation of O3 pollution has been rarely reported. Accordingly, the spatio-temporal evolution of O3 pollution was first analyzed based on hourly air quality data observed by national monitoring stations from 2015 to 2020 over 14 cities in Hunan province. Afterwards, the combination of meteorological data from the European Center for Medium-range Weather Forecast (ECMWF) and the generalized additive model (GAM) was applied to investigate the driving factors of the O3 long-term trend during this period. The results presented obvious diurnal, monthly, and seasonal characteristics of O3 variations. High O3 concentrations occurred in May and September monthly, and the peak O3 season was autumn. Furthermore, the 90th percentile O3 increased at a rate of 4.7 µg·(m3·a)-1 temporally, and high O3 values mainly occurred in the north-eastern region spatially, in contrast to the low O3 values in the western region. The modeling results indicated that the increase in O3 was mainly ascribed to precursor emissions. Furthermore, meteorology promoted a rise in O3 with the impact magnitude of 1 µg·(m3·a)-1. Remarkably, meteorology accelerated the O3 increases in spring, summer, and the eastern region, whereas it restrained increases in autumn, winter, and the northwest. The effect of meteorology on PM10 was different from O3 during this period. Overall, this study highlighted the importance of meteorological impacts when regulating emission reduction measures for O3 abatement. It required greater effort regarding O3 mitigation to offset the side-effect from meteorology in meteorology-sensitive seasons and regions. Additionally, the regional corporation is indispensable to reduce O3 transportation from upwind.

[Discussion of Emissions and Health Risk of Polycyclic Aromatic Hydrocarbons (PAHs) from the Retreading Process of Waste Tires].

The emissions characteristics of 16 kinds of polycyclic aromatic hydrocarbons (PAHs) in ambient air during the waste tire retreading process (open-air storage, mixing, vulcanization, and grinding processes) and in workers' dormitory were analyzed. In addition, the occupational health risk of the workers was evaluated. Results showed that PAHs were detected in all retreading processes and in the workers' dormitory. The highest concentration site was the mixing process, followed by open-air storage and vulcanization process. The lowest concentration point was in the grinding process. The average concentration of PAHs in the workers' dormitory was 11.1 ng·m-3. The PAHs at all sampling points were largely phenanthrene (Phe), fluoranthene (Flu), anthracene (Ant), and pyrene (Pry), which also had a stronger linear correlation with the total PAH concentration. An analysis of the benzene rings showed that three ring and four ring were the majority, while two ring, five ring, and six ring components accounted for less than 10%. Results of the possible influencing factors of the PAHs revealed that the open-air storage and dormitory might be affected by a combustion source, but the mixing, vulcanization, and grinding processes might be affected by rubber oil. The principal component analysis (PCA) and cluster analysis showed that the spatial location of all sites would significantly influence the distribution of PAHs during the tire retreading process. The health risk assessment showed that occupational workers had a lower risk of lifelong cancer, and there was little influence on life expectancy.

The mechanism of indium-assisted growth of (In)GaN nanorods: eliminating nanorod coalescence by indium-enhanced atomic migration.

Both well vertically aligned and uniformly separated (In)GaN nanorods (NRs) were successfully grown on Si(111) substrates by plasma-assisted molecular beam epitaxy. Effects of supplied indium (In) flux on the morphology of (In)GaN NRs were investigated systematically. The scanning electron microscopic analysis and transmission electron microscopic measurements revealed that the presence of In flux can help to inhibit NR coalescence and obtain well-separated (In)GaN NRs. By increasing the supplied In flux, the densities of (In)GaN NRs decreased and the axial growth rates increased. According to the energy dispersive X-ray spectrometry measurements and theoretical calculations, the increase of In content of the NRs enhanced Ga diffusion on the NR sidewalls, which resulted in an increased axial growth rate. A kinetic In-assisted growth model for the well-separated (In)GaN NRs is therefore proposed. The model explains that the presence of In flux not only reduces the density of (In)GaN NRs due to the increase in substrate surface migration of Ga adatoms at nucleation stage but also lead to a remarkable enhancement of axial growth rate at growth stage. Consequently, the NR coalescence was significantly suppressed. The results provide a demonstration of obtaining well-separated (In)GaN NRs and open up further possibility of developing (In)GaN NR-based optoelectronic devices.

Growth of InN Nanowires with Uniform Diameter on Si(111) Substrates: Competition Between Migration and Desorption of In Atoms.

The effects of the growth parameters on the uniformity and the aspect ratio of InN nanowires grown on Si(111) substrates have been studied systematically, and a modified quasi-equilibrium model is proposed. The growth temperature is of great importance for both the nucleation of the nanowires and the migration of In and N atoms, thus affecting the uniformity of the InN nanowires. In order to improve the uniformity of the InN nanowires, both traditional substrate nitridation and pre-In-droplet deposition have been implemented. It is found that the substrate nitridation is favorable for the nucleation of InN nanowires. However, the initial In atoms adhered to the substrate are insufficient to sustain the uniform growth of the InN nanowires. We have found that the initial In droplet on the substrate is not only advantageous for the nucleation of the InN nanowire, but also favorable for the In atom equilibrium between the initial In droplets and the direct In flux. Therefore, InN nanowires with a uniform aspect ratio and optimal diameter can be achieved. The results reported herein provide meaningful insights to understanding the growth kinetics during the InN nanowires growth, and open up great possibilities of developing high-performance group III-nitride-based devices.

[Possible Sources of PCDD/Fs in Atmosphere of a Certain District in Guangdong].

This paper analyzed 17 polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs) by HRGC/HRMS in the flue gas of a certain municipal solid waste incinerator(MSWI) and its surrounding air and other possible sources in Guangdong. It discussed the feature of homologs and main toxic monomers in all samples. It also investigated the relationship among surrounding area, MSWI and possible sources using principle component analysis (PCA) and cluster analysis. The results showed that the concentration of PCDD/Fs was higher in the flue gas than the ambient air, moreover non-effect suffered by prevailing wind direction. The possible sources might be tyre factory and open burning based on spot survey. The concentration of PCDD/Fs was lower in tyre factory than upwind station, but higher at open burning spot than outdrop monitoring station. The analysis of homologs showed that OCDD, 1,2,3,4,6,7,8-HpCDD and 1,2,3,4,6,7,8-HpCDF were the main materials in the flue gas and air, meanwhile OCDF was also found in atmosphere. There was similar feature of 17 PCDD/Fs between surrounding monitoring station and tyre factory, and the same between flue gas and open burning. The further analysis showed that the linearly dependent coefficients of 1,2,3,7,8-PeCDD and 2,3,4,6,7,8-HxCDF were 0.95 and 0.75, respectively. It showed the strong correlation of two monomers in all ambient air samples. The PCA and cluster analysis showed that MSWI influenced the surrounding air, tyre factory had an impact on upwind station, and open burning had a lower effect on outdrop monitoring station.

Environmental application of millimetre-scale sponge iron (s-Fe(0)) particles (III): The effect of surface silver.

To enhance the dechlorination reactivity of millimetric sponge iron (s-Fe(0)), a facile one-pot method was used to decorate s-Fe(0) with Ag(+) ions under ambient conditions. The results recorded by X-ray diffraction patterns, X-ray photoelectron spectra and high-resolution transmission electron microscopy demonstrated that the growth of Ag(0) was dominated primarily by (111) plane with a mean length of ∼20 nm. The roles of Ag(0) loading, catalyst dosage, particle size, initial pH and contaminant concentration were assessed during the removal of pentachlorophenol (PCP). Catalyst recyclability was also studied. The results revealed that 3-5mm s-Fe(0) particles with 5 wt% Ag(0) loading exhibited the best performance with a dose of 3.0 g per 60 mL PCP solution. In addition, the dechlorination of PCP followed two-step, pseudo-first-order reaction kinetics, and Ag(0)-s-Fe(0) was advantageous compared with bimetals of nanoscale zero-valent iron, iron power and iron flakes. The dechlorination mechanism of PCP over Ag(0)-s-Fe(0) was attributed to the surface Ag(0) decoration, which catalyzed the formation of reactive hydrogen atoms for indirect reaction, and the direct electron transfer via Fe-Ag(0) galvanic cells for direct reaction. This suggests that Ag-based bimetals of s-Fe(0) have great potential in the pretreatment of organic halogen compounds in aqueous solution.

[Emission of PCDD/Fs from Crematories and Its Influencing Factors].

To analysis the influencing factors for the emssions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) as structure of crematory, air pollution control device (APCD) and funeral objects, etc, we collected and measured the PCDD/Fs emissions in flue gas from 13 crematories in China. Then we proposed some supervision suggestions on measures of pollution control and management. The results indicated that the emission levels of PCDD/Fs (as the toxic equivalent concentration, TEQ) was ranged in a large gap from 0.027 to 15.8 ng x m(-3), and the average was 3.2 ng x m(-3). Emissions factor of PCDD/Fs (as TEQ) from 13 crematories varied between 45.9 and 22 236 ng x body(-1), and the average was 4 738 ng x body(-1). The emissions of PCDD/Fs from flat incinerators were generally lower, whereas higher ratio up to the national discharge standard, than that of car type incinerators. Congener distribution of PCDD/Fs in flue gas from 13 crematories were different from each other. Since the emission of PCDD/Fs from some crematories remains in high level, it is necessary to control pollution from the source, improve the pollution control technology, and strengthen government supervision, by following measures: 11 cremating funeral objects separately from corpse; 22 adding one

[Analysis of polycyclic aromatic hydrocarbons in air samples by gas chromatography-triple quadrupole mass spectrometry].

A method of gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC-MS/MS) has been optimized for the determination of polycyclic aromatic hydrocarbons (PAHs) in air samples. In the analysis step, isotope dilution was introduced to the quantification of PAHs. The GC-MS/MS method was applied to the analysis of the real air samples around a big petrochemical power plant in South China. The results were compared with those obtained by gas chromatography coupled to mass spectrometry (GC-MS). The results showed that better selectivity and sensitivity were obtained by GC-MS/MS. It was found that the external standard of deuterated-PAHs and internal standard of hexamethyl benzene were disturbed seriously with GC-MS, and the problems were both solved effectively by GC-MS/MS. Therefore more accurate quantification results of PAHs were obtained with GC-MS/MS. For the analysis of real samples, the RSDs of relative response factors ranged from 2.60% to 15.6% in standard curves; the recoveries of deuterated-PAHs ranged from 55.2% to 82.3%; the recoveries of spiked samples ranged from 98.9% to 111%; the RSDs of parallel specimens ranged from 6.50% to 18.4%; the concentrations of field blank samples ranged from not detected to 44.3 pg/m3; and the concentrations of library blank samples ranged from not detected to 36.5 pg/m3. The study indicated that the application of GC-MS/MS on the analysis of PAHs in air samples was recommended.

[Determination of aniline in water and fish by liquid chromatography-tandem mass spectrometry].

A fast analytical method for the determination of aniline in water and fish meat by liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed. The water sample was mixed with acetonitrile by 4:1 (v/v) and the fish sample was extracted by 2.00 mL acetonitrile for each gram of sample, and then the extracts of water and fish samples were centrifuged at 5,000 r/min for 5 min. The separation was performed on a reversed-phase C18 column using mobile phases of acetonitrile-0.5% (v/v) formic acid aqueous solution (85:15, v/v). Aniline was separated within 3 min. The calibration curve was linear in the range of 0.5-500 pg/L with R2 > 0.999. The limits of detection (LODs) were 0.50 µg/L and 1.00 µg/kg and the limits of quantification (LOQs) were 1.00 µg/L and 2.00 µg/kg for aniline in water and fish meat, respectively. The average recoveries of aniline in water were 93.7% at the spiked level of 40 ng and 86.7% at the spiked level of 400 ng (n = 5). The average recoveries of aniline in fish were 96.8%, 92.6% and 81.8% at the spiked levels of 5, 50 and 500 ng respectively (n = 5). The relative standard deviations were 1.5%-9.2%. Thirteen water samples and twelve fish samples were collected from a reservoir polluted by aniline and the maximum contents found were 1,943. 6 µg/L in water and 60.8 µg/kg in fish. The method is suitable for the determination of aniline residues in water and fish with the characteristics of easy operation, high accuracy and precision.

[Concentrations and distribution characteristics of PCDD/Fs in spent etching solution and its copper salt recycling products].

Concentrations of 17 PCDD/Fs congeners in spent etching solution and its copper salt recycling products were determined by the high resolution gas chromatography-high resolution mass spectrometry (HRGC-HRMS). The PCDD/F concentrations and corresponding WHO-TEQ (toxic equivalent quantity) values were in the range of 0-3 460 pg.L (mean= 616 pg.L-1) and 0-246 pg.L-1 (mean = 42.9 pg.L-1) , respectively, in the spent etching solution, and 1.08-24.6 ng.kg-1 (mean = 8.83 ng.kg-1) and 0.112-0.715 ng.kg-1 (mean = 0.338 ng.kg-1), respectively, in the copper salt products. The established purification treatment technique could remove most of the PCDD/Fs in the etching solution. Of the copper products, higher PCDD/F concentrations were detected in industrial products than in feed grade and plating grade products. Similar distribution characteristics were found for PCDD/ Fs in all copper salt products as the followings: 1. PCDFs were more abundant than PCDDs, 2. high chlorinated congeners were more abundant than low chlorinated congeners, except for 2,3,7,8-TCDF in the copper sulfate products.

[Characterization of water-soluble inorganic ions in PM2.5 and PM1.0 in summer in Guangzhou].

PM2.5 and PM1.0 samples were collected simultaneously during July of 2008 in Guangzhou. The concentrations of water-soluble inorganic ions (Na+, NH4+, K+, Mg2+, Ca2+, F-, Cl-, NO3-, and SO4(2-)) were determined by ion chromatography. Meteorological parameters, atmospheric scattering, visibility, and concentrations of trace gases (SO2, NO2, and O3) for this period were also recorded. The results showed the total water-soluble inorganic ions concentrations were (25.5 +/- 10.9) microg x m(-1) and (22. 7 +/- 10.5) microg x m(-3) in PM2.5 and PM1.0, which occupied (47.9 +/- 4.3)% and (49.3 +/- 4.3)% of PM mass respectively. Sulfate was the most abundant ion and contributed (25.8 +/- 4.0)% of PM2.5 mass and (27.5 +/- 4.5)% of PM1.0 mass respectively. High temperature and high ozone level favored the formation of sulfate from sulfur dioxide, while the high relative humidity favored the formation of nitrate were observed. Moreover, sulfate, nitrate, and ammonium in PM2.5 and PM1.0 had great impact on the scattering coefficient and visibility degradation.