Emission of PAHs, NPAHs and OPAHs from residential honeycomb coal briquette combustion

Coal combustion is one of the most significant sources of air pollution in China. In this study, emission factors (EFs) of 15 polycyclic aromatic hydrocarbons (PAHs), 26 nitrated PAHs (NPAHs) and 6 oxygenated PAHs (OPAHs) were determined in five different coals with different geological maturity (vitrinite reflectance <i>R</i>_O = 0.77–1.88%) burned in the form of honeycomb briquettes. The total EFs ranged from 9.82 to 215 mg kg^–1 for PAHs, 0.14 to 1.88 mg kg^–1 for NPAHs and 4.47 to 20.8 mg kg^–1 for OPAHs. Measured EFs and gas-particle partitioning varied depending on the geological maturity. The lowest EFs were found in anthracite. The proportion of PAHs, NPAHs and OPAHs in gaseous phase increasing with increased geological maturity. The coal with higher geological maturity produced more 3-ring PAHs. On the basis of the statistical analysis for the residential sector of China in 2008, PAHs, NPAHs and OPAHs emitted from residential honeycomb coal briquettes were 4.36 Gg, 0.03 Gg and 0.47 Gg in 2007, respectively. By 2020, the emission would decrease to 2.18 Gg, 0.02 Gg and 0.24 Gg for PAHs, NPAHs and OPAHs due to the increasing usage of new energy resources. If only anthracite is used as the residential coal, 93% PAHs, 87% NPAHs and 71% OPAHs would be reduced in 2020

Impact of in-cloud aqueous processes on the chemical compositions and morphology of individual atmospheric aerosols

The composition, morphology, and mixing structure of individual cloud residues (RES) and interstitial particles (INT) at a mountaintop site were investigated. Eight types of particles were identified, including sulfate-rich (S-rich), S-organic matter (OM), aged soot, aged mineral dust, aged fly ash, aged metal, refractory, and aged refractory mixture. A shift of dominant particle types from S-rich (29 %) and aged soot (27 %) in the INT to aged refractory mixture (23 %) and S-OM (22 %) in the RES is observed. In particular, particles with organic shells are enriched in the RES (27 %) relative to the INT (12 %). Our results highlight that the formation of more oxidized organic matter in the cloud contributes to the existence of organic shells after cloud processing. The fractal dimension (D$_{f}$), a morphologic parameter to represent the branching degree of particles, for soot particles in the RES (1.82 ± 0.12) is lower than that in the INT (2.11 ± 0.09), which indicates that in-cloud processes may result in less compact soot. This research emphasizes the role of in-cloud processes in the chemistry and microphysical properties of individual particles. Given that organic coatings may determine the particle hygroscopicity, activation ability, and heterogeneous chemical reactivity, the increase of OM-shelled particles upon in-cloud processes should have considerable implications

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals &lt;1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Does atmospheric processing produce toxic Pb-containing compounds? A case study in suburban Beijing by single particle mass spectrometry

A single particle aerosol mass spectrometry (SPAMS) was deployed to investigate the mixing state and chemical processing of Pb-rich particles in suburban Beijing. Based on a large dataset of mass spectra, Pb-rich particles were classified into Pb-O-Cl-N-S (55%), Pb-N (17%), Pb-N-S (15%), and Pb-EC (7%). Residual coal combustion, industrial activities, and meteorological conditions were identified as main factors regulating the variations of Pb-rich particles in the atmosphere. The highest abundance of the Pb-rich particles was observed during heating period (HP) primarily due to the increase in coal usage. Pb in Pb-O-Cl-N-S type was identified in forms of PbO, PbCl2, and Pb(NO3)(2). Dominantly presented in the form of Pb(NO3)(2), Pb-N type represented the completely transformed Pb-rich particles from PbO/PbCl2 by atmospheric processes. It is found that PbCl2 and PbO could be transformed to Pb(NO3)(2), highly dependent on the amount of NO2 and RH. Significant enhancement of nitrate in Pb-O-Cl-N-S particles was observed when the RH was greater than 60%, emphasizing the importance of heterogeneous hydrolysis of N2O5 on the formation of Pb(NO3)(2). Compared with non-carcinogenic PbCl2/PbO and insoluble PbO, soluble and carcinogenic Pb(NO3)(2) produced by atmospheric processes may significantly enhance negative effects of Pb-rich particles on human health and the ecosystem

Effect of lightning activities on surface atmospheric NO, O-3 and submicron particles based on artificially triggered lightning technology: A case study

Lightning can cause a variety of atmospheric chemical reactions because of its high temperature and high pressure. Known as a major natural source of atmospheric nitrogen oxides (NOx), lightning can also affect the abundance of ozone (O-3) and result in the generation of new particles in the atmosphere. This study explores the effect of lightning activities on surface atmospheric nitric oxide (NO), O-3 and submicron particles utilizing artificially triggered lightning experiments. Five lightning flashes were successfully triggered in Guangzhou on 19th August 2014. Concentrations of surface NO, O-3 and submicron particles were observed together with lightning and meteorological parameters. Results show that NO concentration increased rapidly from 0.4 ppbv to 220.5 ppbv after a successful upwind artificially triggered lightning flash. Wind direction played an important role in the enhancement of NO concentration at different levels caused by each triggered lightning flash. O-3 concentration increased from 15.8 ppbv to 28.7 ppbv before triggering lightning. After the first triggered lightning flash, O-3 concentration decreased rapidly to the valley value of 16.9 ppbv because of titration effect. In addition, the number concentration of submicron particles also increased rapidly after successful triggered lightning experiments. The finds resulting from this study give a deeper insight into the impact of lightning on atmospheric chemistry

Gas-to-particle partitioning of atmospheric amines observed at a mountain site in southern China

Amines play an important role in the formation and transformation of atmospheric aerosols. Gaseous phase and PM2.5 samples were collected simultaneously at Nanling Mountains, southern China during autumn 2016 and summer 2017. The site is strongly affected by long distance transport from marine and continental air masses. Five amines, methylamine (MA), dimethylamine (DMA), diethylamine (DEA), dibutylamine (DBA) and morpholine (MOR), were detected by gas chromatography-mass spectrometry (GC-MS) after derivatization. The backward trajectory analyses suggested that different origins of air masses led to seasonal variation of amines. In gaseous phase samples, the average concentrations of total measured amines (Sigma amines) were 193.4 +/- 111.7 ng m(-3) in autumn 2016 and 307.5 +/- 196.7 ng m(-3) in summer 2017. In PM2.5 samples, the average concentrations of Sigma amines were 12.4 +/- 10.8 ng m(-3) in autumn 2016 and 20.7 +/- 11.0 ng m(-3) in summer 2017. MA and DMA were the dominant amines, together contributing approximately 70% to gaseous amines and 80% to particulate amines. A strong linear relationship was found between Sigma amines and NO3- in PM2.5, implying that amines might mainly exist in the form of aminium nitrate. Ammonium (NH4+) was found mostly likely in the form of ammonia sulfate. Approximately 7.4% of the gaseous total amines partitioned to PM2.5. A good linear relationship between the fraction of total atmospheric concentration sorbed by PM2.5 (phi) and the concentrations of O-3 was found, suggesting that O-3 likely played an important factor in the gas-to-particle partitioning of amines. Additionally, under high relative humidity circumstances (92% +/- 7.0%), direct dissolution was a crucial step for gaseous amines partitioning into particles. The ratios of amines-C to water-soluble organic carbon (WSOC) and amines-N to water-soluble organic nitrogen (WSON) were 0.21% and 1.57% in autumn 2016 and 0.54% and 2.08% in summer 2017, respectively. The results of this study provide essential information on the formation mechanism of particulate amines