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Mixing state of black carbon (BC) with secondary species has been highlighted as a major uncertainty in assessing its radiative forcing. While recent laboratory simulation has demonstrated that BC could serve as a catalyst to enhance the formation of sulfate, its role in the formation and evolution of secondary aerosols in the real atmosphere remains poorly understood. In the present study, the mixing of BC with sulfate/nitrate in the atmosphere of Guangzhou (China) was directly investigated with a single particle aerosol mass spectrometer (SPAMS). The peak area ratios of sulfate to nitrate (SNRs) for the BC‐containing particles are constantly higher than those of the BC‐free particles (defined as particles with negligible BC signals). Furthermore, the seasonal SNR peak is observed in summer and autumn, and the diurnal peak is found in the afternoon, consistent with the trends of radiation‐related parameters (i.e., solar radiation and temperature), pointing to the BC‐induced photochemical production of sulfate. Such hypothesis is further supported by the multilinear regression and random forest analysis, showing that the variation of SNRs associated with the BC‐containing particles could be well explained (R2 = ∼0.7–0.8) by the radiation‐related parameters (>30% of the variance) and the relative BC content (∼20%) in individual particles, but with limited influence of precursors (SO2/NOx: <5%). Differently, the radiation‐related factors only explain <10% of the SNR variation for the BC‐free particles. These results provide ambient observational evidence pointing to a unique role of BC on the photochemical formation and evolution of sulfate, which merits further quantitative evaluations. Plain Language Summary: Despite ubiquitous in the atmosphere, the potential role of BC black carbon (BC) in the formation and evolution of secondary aerosols in the real atmosphere remains poorly understood. Here, we have investigated the detailed mixing state of BC with sulfate/nitrate in the atmosphere of Guangzhou in real‐time by a Single Particle Aerosol Mass Spectrometer. We show that the distinct seasonal and diurnal variation of the enhanced sulfate/nitrate ratios is most likely driven by the BC catalytic photochemistry. Our results provide first ambient observational evidence, extending the laboratory results to the ambient atmosphere that BC could act as a photoactive and absorbing substrate, leading to an enrichment of sulfate, in particular, during summer and autumn. Thus, the BC emission controls may also mitigate the formation and evolution of sulfate and it is essential to include BC involved photochemistry in the models to account for the evolution and climate impact of BC accurately. Key Points: Enhanced sulfate to nitrate ratios (SNRs) are observed for the black carbon (BC)‐containing particlesThe distinct diurnal variation of the enhanced SNRs is most likely attributed to BC catalytic photochemistrySNRs in individual BC‐containing particles could be well predicted by the radiation‐related parameters and the relative BC content [ABSTRACT FROM AUTHOR]

Nitrogen-containing organic compounds (NOCs) substantially contribute to light-absorbing organic aerosols, although the atmospheric processes responsible for the secondary formation of these compounds are poorly understood. In this study, seasonal atmospheric processing of NOCs is investigated using single-particle mass spectrometry in urban Guangzhou from 2013 to 2014. The relative abundance of NOCs is found to be strongly enhanced when they are internally mixed with photochemically produced secondary oxidized organics (i.e., formate, acetate, pyruvate, methylglyoxal, glyoxylate, oxalate, malonate, and succinate) and ammonium (NH4+). Moreover, both the hourly detected particle number and the relative abundance of NOCs are highly correlated with those of secondary oxidized organics and NH4+. Therefore, it is hypothesized that the secondary formation of NOCs is most likely linked to oxidized organics and NH4+. Results from both multiple linear regression analysis and positive matrix factorization analysis further show that the relative abundance of NOCs could be well predicted (R2 > 0.7, p < 0.01) by oxidized organics and NH4+. Interestingly, the relative abundance of NOCs is inversely correlated with NH4+ , whereas their number fractions are positively correlated. This result suggests that although the formation of NOCs does require the involvement of NH3/NH4+ , the relative amount of NH4+ may have a negative effect. Higher humidity and NOx likely facilitates the conversion of oxidized organics to NOCs. Due to the relatively high oxidized organics and NH3/NH4+ , the relative contributions of NOCs in summer and fall were higher than those in spring and winter. To the best of our knowledge, this is the first direct field observation study reporting a close association between NOCs and both oxidized organics and NH4+. These findings have substantial implications for the role of NH4+ in the atmosphere, particularly in models that predict the evolution and deposition of NOCs. Highlights. NOCs were highly internally mixed with photochemically produced secondary oxidized organics NOCs could be well predicted by the variations of these oxidized organics and NH4+ Higher relative humidity and NOx may facilitate the conversion of these oxidized organics to NOCs [ABSTRACT FROM AUTHOR]

Abstract The toxic effects of lead on human health and the environment have long been a focus of research. To explore sources of lead in Guangzhou, China, we investigated atmospheric lead-containing particles (LCPs) during wintertime using a single particle aerosol mass spectrometer (SPAMS). Based on mass spectral features, LCPs were classified into eight major particle types, including Pb-Cl and Pb-Cl-Li (coal combustion and waste incineration), Pb-Cl-EC and Pb-Cl-OC (diesel trucks and coal combustion), Pb-Cl-Fe (iron and steel industry), Pb-Cl-AlSi (dust), Pb-Sec (secondary formation), and Pb-Cl-Zn (industrial process); these sources (in parentheses) were identified by comparing atmospheric LCP mass spectra with authentic Pb emission source mass spectra. Sampling periods with LCP number fractions (NFs) more than three times the average LCP NF (APF = 4.35%) and below the APF were defined as high LCP NF periods (HLFPs: H1, H3, and H5) and low LCP NF APF periods (LLFPs: L2 and L4), respectively. Diurnal patterns and high Pb-Sec content during LLFPs indicate that photochemical activity and heterogeneous reactions may have controlled Pb-Sec particle formation. The inverse Pb-Cl and Pb-Sec particle diurnal trends during LLFPs suggest the replacement of Cl by sulfate and nitrate. On average over the five periods, ~ 76% of the LCPs likely arose from coal combustion and/or waste incineration, which were dominant sources during all five periods, followed by diesel trucks during LLFPs and iron- and steel-related sources during HLFPs; HLFP LCPs arose mainly from primary emissions. These results can be used to more efficiently control Pb emission sources and prevent harm to human and environmental health from Pb toxicity. Highlights • Lead-containing particles (LCPs) in Guangzhou were characterized using the SPAMS. • Authentic Pb emission sources were determined and used for LCP source apportionment. • ~ 76% of LCPs arose from coal combustion and/or waste incineration. • Photochemical activity/heterogeneous reactions may contribute to Pb-Sec formation. [ABSTRACT FROM AUTHOR]

Size-segregated PM 10 samples were collected in Guangzhou, China during autumn of 2014. Nine amines, including seven aliphatic amines and two heterocyclic amines, were detected using a gas chromatography-mass spectrometer after derivatization by benzenesulfonyl chloride. The total concentration of the nine amines (Ʃamines) was 79.6–140.9 ng m −3 in PM 10 . The most abundant species was methylamine (MA), which had a concentration of 29.2–70.1 ng m −3 . MA, dimethylamine (DMA), diethylamine (DEA) and dibutylamine (DBA) were the predominant amines in the samples and accounted for approximately 80% of Ʃamines in each size segment. Two heterocyclic amines, pyrrolidine (PYR) and morpholine (MOR), were detected in all samples and had average concentrations of 1.14 ± 0.37 and 1.89 ± 0.64 ng m −3 , respectively, in particles with aerodynamic diameters < 3 μm. More than 80% of Ʃamines were found in particles with diameters <1.5 μm, indicating that amines are mainly enriched in fine particles. All amines exhibited a bimodal distribution with a fine mode at 0.49–1.5 μm and a coarse mode at 7.2–10 μm. The maximum contributions of amines to particles (0.21%) and amines-N to water-soluble organic nitrogen (WSON) (3.1%) were found at the sizes < 0.49 μm. The maximum contribution of amines-C to water-soluble organic carbon (WSOC) was 1.6% over the size range of 0.95–1.5 μm. The molar ratio of Ʃamines to ammonium ranged from 0.0068 to 0.0107 in particles with diameters <1.5 μm, and the maximum ratio occurred in the smallest particles (diameter< 0.49 μm). The average dry deposition flux and velocity of Ʃamines in PM 10 were 7.9 ± 1.6 μg m −2 d −1 and 0.084 ± 0.0021 cm s −1 , respectively. The results of this study provide essential information on the contribution of amines to secondary organic aerosols and dry removal mechanisms in urban areas. [ABSTRACT FROM AUTHOR]

Abstract: Trimethylamine (TMA) plays an important role in atmospheric chemistry, yet its pathway towards aerosol is not clear. We report in this study the measurement of TMA in submicron particles using a single particle aerosol mass spectrometer (SPAMS) in urban Guangzhou, China for the period of 30 April through 22 May, 2010. The number fraction of TMA-containing particles relative to total detected particle number dramatically increased within the occurrence of fogs. It changed from an average of ∼7% for clear days to ∼35% for the fog events. For particles with size larger than 0.5 μm, the fraction could even account up to ∼60%. Averaged relative intensity of TMA was correlated well with relative humidity, indicating the important role of aerosol water content in the gas-to-particle partitioning of TMA. During the fog events, number based size distribution of TMA-containing particles shifted towards larger mode, peaking at droplet mode (0.5–1.2 μm), corresponding to the build-up of aerosol mass, suggesting the significant mass transfer of TMA and other semi-volatile species from gas to aerosol. Results also reveal that most of TMA-containing particles also contained signals from ammonium, nitrate and sulfate. A much larger fraction of TMA-containing particles was found to contain nitrate during the fog events than on clear days. During the fog events, nitrate and sulfate were more strongly associated with TMA compared to ammonia, which was oppositely observed on clear days. These results indicate that gas-to-particle partitioning of TMA in urban Guangzhou occurs preferentially during fog processing. The study could help improve our understanding in fog processing and potential roles of TMA-containing particles in urban Guangzhou. [Copyright &y& Elsevier]

Size distribution aerosol samples were collected at an urban location of Guangzhou in four seasons of 2003–2004 by a MOUDI (Micro-orifice Uniform Deposit Impactor). The particle loading (PM10: 80–397μgm−3) was comparable with some other Asia cities; however, much higher than that of Western Europe and North America. Polycyclic aromatic hydrocarbons (PAHs) were measured by gas chromatography with mass selective detector (GC–MS). Seasonal effects on the size distribution of PAHs are presented. Bimode (accumulation and coarse mode) and unimode (accumulation mode) distributions were observed for low-molecule-weight and high-molecule-weight PAHs. A slight shift to larger particles was found for the accumulation mode in autumn and winter, compared with that of spring and summer. One explanation is that the longer aging process of PAHs in autumn and winter would result in volatilization from finer particles followed by condensation onto coarser particles. Another is there was mixing process of local emission with long-range transported aerosol in autumn and winter. The relative higher value of IcdP/(BghiP+IcdP) and lower value of BghiP/BeP in winter also give evidences to the mixing process. The level of PAHs concentration has been much elevated in recent years. This can be attributed to the fast growth of motor vehicle and energy consumption. [Copyright &y& Elsevier]

Continuous ambient measurement of atmospheric aerosols was performed with a single particle aerosol mass spectrometer (SPAMS) in Guangzhou during summer of 2012. The aerosols mainly consisted of carbonaceous particles as major compositions in submicrometer range, including K-rich (29.8%), internally mixed organics and elemental carbon (ECOC, 13.5%), organic carbon-rich (OC, 18.5%), elemental carbon (EC, 12.3%) and high molecular OC (HMOC, 3.2%), and inorganic types (e.g., Na-rich Na-K, Fe-rich, V-rich, and Cu-rich) as major ones in supermicrometer range. Results show that carbonaceous particles were commonly internally mixed with sulfate and nitrate through atmospheric processing, in particular, with sulfate; inorganic types were dominantly internally mixed with nitrate rather than sulfate, indicative of different evolution processes for carbonaceous and inorganic particles in the atmosphere. It was observed that variations of these particle types were significantly influenced by air mass back trajectories (BTs). Under the influence of continental BTs, carbonaceous types were prevalent, while Na-K and Na-rich types considerably increased when the BTs originated from south marine regions. Number fraction of carbonaceous types exhibited obvious diurnal variation throughout the sampling period, which reflects their relatively stable emission and atmospheric processes. Two EC particle types LC-EC and NaK-EC showed different diurnal distributions, suggesting their different origins. The obtained information on the mixing state and the temporal variation of particle types is essential for developing an understanding on the origin and evolution processes of atmospheric aerosols. [ABSTRACT FROM AUTHOR]

Abstract: Exposure of young mothers and newborns to organochlorine pesticides (OCPs) were assessed by measuring the levels of OCPs in human milk (HM) and maternal blood (MB) and umbilical cord blood (UCB) samples from Guangzou in China. 21 OCPs were analyzed using gas chromatography/mass spectrometry (GC/MS). The results showed that the median levels (ranges) of total HCHs (four HCH isomers) in HM, MB and UBC were 54.7 (5.7–159.3), 43.7 (1.9–386.6), and 20.2 (4.0–103.2) ng/g lipid, respectively; and the median concentration of total DDTs (DDT and its metabolites) were 2114.6 (329.1–6164.6), 1676.0(283.4–6167.7), and 1287.8(189.6–3296.0) ng/g lipid, respectively. On a lipid basis, the chemical concentrations were in the order HM>MB>UCB. Comparison with literature data showed that the levels of ∑DTTs and ∑HCHs in milk and maternal blood samples were within the range reported in samples in other Chinese provinces and higher than those in developed or industrialized countries, but significantly lower than contaminated area such as in India. The predominant pollutant in the HCH family is β-HCH. p,p′-DDE is a predominant pollutant in all DDEs and DDDs and DDTs for all the samples tested, and accounted for more than 80% of total HCHs and DDTs. [Copyright &y& Elsevier]

Traffic restriction (TR) is a widely adopted control measure in case of heavy air pollution particularly in urban areas, yet it is hard to evaluate the effect of TR on reducing VOC emissions based on monitoring data since ambient VOC mixing ratios are influenced not only by source emissions but also by meteorological conditions and atmospheric degradation. Here we collected air samples for analysis of VOCs before, during and after a TR drill carried out in Guangzhou in September 2010 at both a roadside and a rooftop (∼50 m above the ground) site. TR measures mainly included the “odd-even license” rule and banning high-emitting “yellow label” vehicles. The mixing ratios of non-methane hydrocarbons (NMHCs) did not show significant changes at the roadside site with total NMHCs of 39.0 ± 11.8 ppbv during non-TR period and 39.1 ± 14.8 ppbv during TR period, whereas total NMHCs decreased from 30.4 ± 14.3 ppbv during the non-TR period to 22.1 ± 10.6 ppbv during the TR period at rooftop site. However, the ratios of methyl tert-butyl ether (MTBE), benzene and toluene against carbon monoxide (MTBE/CO, T/CO and B/CO) at the both sampling sites dropped significantly. The ratios of toluene to benzene (T/B) instead increased significantly. Changes in these ratios all consistently indicated reduced input from traffic emissions particularly gasoline vehicles. Source attribution by positive matrix factorization (PMF) confirmed that during the TR period gasoline vehicles contributed less VOCs in percentages while industrial sources, biomass burning and LPG shared larger percentages. Assuming that emissions from industrial sources remained unchanged during the TR and non-TR periods, we further used the PMF-retrieved contribution percentages to deduce the reduction rate of traffic-related VOC emissions, and obtained a reduction rate of 31% based on monitoring data at the roadside site and of 34% based on the monitoring data at the rooftop site. Considering VOC emissions from all sources in Guangzhou city, the TR control measures adopted could reduce VOC up to 15%. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) have attracted an increasing concern in China's megacities. However, rare information is available on the spatial and seasonal variations of inhalation cancer risk (ICR) due to PAH exposure and their relations to specific sources. In this study, year-round PM 2.5 samples were collected from 2013 to 2014 by high-volume samplers at four sites (one urban, two rural and one roadside station) in Guangzhou in the highly industrialized and densely populated Pearl River Delta (PRD) region and analyzed for 26 polycyclic aromatic hydrocarbons (PAHs) together with molecular tracers including levoglucosan, hopanes and elemental carbon. Higher molecular weight PAHs (5-ring or above) accounted for 64.3–87.5% of total PAHs. Estimated annual averages of benzo( a )pyrene-equivalent carcinogenic potency (BaP eq ) were 1.37, 2.31 and 1.56 ng/m 3 at urban SZ, rural JL and rural WQS, respectively, much higher than that at the roadside station YJ in an urban street canyon. ICR of PAHs in wintertime reached 2.2 × 10 −4 , nearly 3 times that in summer; and cancer risk of PAHs was surprisingly higher at the rural site than at other sites. Source contributions by positive matrix factorization (PMF) in the aid of molecular tracers revealed that overall coal combustion and biomass burning altogether contributed 73.8% of total PAHs and 85.2% of BaP eq , and particularly in winter biomass burning became the most significant source of total PAHs and BaP eq (51.8% and 52.5%), followed by coal combustion (32.0% and 39.1%) and vehicle emission (16.2% and 8.4%). The findings of this work suggest that even in China's megacities like Guangzhou, limiting biomass burning may benefit PAHs pollution control and cancer risk reduction. [ABSTRACT FROM AUTHOR]

Nine amine species in atmospheric particles during haze and low-pollution days with low and high relative humidity (RH) were analyzed in urban Guangzhou, China. The mean concentrations of total measured amines (Ʃamines) in fine particles were 208 ± 127, 63.7 ± 21.3, and 120 ± 20.1 ng m−3 during haze, low pollution-low RH (LP-LRH), and low pollution-high RH (LP-HRH) episodes, respectively. The dominant amine species were methylamine (MA), dimethylamine (DMA), diethylamine (DEA) and dibutylamine (DBA), which in total accounted for 82–91% of the Ʃamines during different pollution episodes. The contributions of Ʃamines-C to water-soluble organic carbon (WSOC) and Ʃamines-N to water-soluble organic nitrogen (WSON) were 1.52% and 2.49% during haze, 1.24% and 1.96% during LP-LRH, and 2.00 and 2.98% during LP-HRH days, respectively. The mass proportion of Ʃamines in fine particles was higher during LP-HRH periods (0.19%) than during haze and LP-LRH periods (0.16%). The mass proportion of DBA in Ʃamines increased from 7% during haze and LP-LRH episodes to 25% during LP-HRH episodes. Compared with other amines, DBA showed a stronger linear relationship with RH (r = 0.867, p < 0.01), which demonstrates its high sensitivity to high RH conditions. Meteorological parameters (including RH, the mixed layer depth, wind speed and temperature), the oxidizing capacity (ozone concentration), and gaseous pollutants (NO x and SO 2) correlated with amines under different pollution conditions. Under high RH, acid-base reactions were the dominant pathway for the gas-to-particle distribution of amines in urban areas, while direct dissolution dominated in the background site. To our knowledge, this study is the first attempt to conduct in situ measurements of particulate amines during different pollution conditions in China, and further research is needed to in-depth understanding of the influence of amines on haze formation. • Stagnant meteorology could cause aerosol amines accumulation. • Relative humidity (RH) was a significant factor influencing the enrichment of aerosol amines. • Acid-base reaction is dominant in amines gas-particle partitioning during high RH in urban. [ABSTRACT FROM AUTHOR]

Formaldehyde (HCHO) is the most abundant carbonyl compound in the atmosphere, and vehicle exhaust emission is one of its important anthropogenic sources. However, there is still uncertainty regarding HCHO flux from vehicle emission as well as from other sources. Herein, automobile source was characterized using HCHO carbon isotopic ratio to assess its contributions to atmospheric flux and demonstrate the complex production/consumption processes during combustion in engine cylinder and subsequent catalytic treatment of exhaust. Vehicle exhausts were sampled under different idling states and HCHO carbon isotopic ratios were measured by gas chromatograph–combustion–isotopic ratio mass spectrometry (GC–C–IRMS). The HCHO directly emitted from stand-alone engines (gasoline and diesel) running at different load was also sampled and measured. The HCHO carbon isotopic ratios were from −30.8 to −25.7‰ for gasoline engine, and from −26.2 to −20.7‰ for diesel engine, respectively. For diesel vehicle without catalytic converter, the HCHO carbon isotopic ratios were −22.1 ± 2.1‰, and for gasoline vehicle with catalytic converter, the ratios were −21.4 ± 0.7‰. Most of the HCHO carbon isotopic ratios were heavier than the fuel isotopic ratios (from −29 to −27‰). For gasoline vehicle, the isotopic fractionation (Δ13C) between HCHO and fuel isotopic ratios was 7.4 ± 0.7‰, which was higher than that of HCHO from stand-alone gasoline engine (Δ13Cmax = 2.7‰), suggesting additional consumption by the catalytic converter. For diesel vehicle without catalytic converter, Δ13C was 5.7 ± 2.0‰, similar to that of stand-alone diesel engine. In general, the carbon isotopic signatures of HCHO emitted from automobiles were not sensitive to idling states or to other vehicle parameters in our study condition. On comparing these HCHO carbon isotopic data with those of past studies, the atmospheric HCHO in a bus station in Guangzhou might mainly come from vehicle emission for the accordance of carbon isotopic data. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes a new built single particle laser desorption/ionization time of flight mass spectrometer capable of determining the size and chemical compositions of individual aerosol particles in real-time. The instrument was compactly designed with bipolar grid reflectron mass analyzers for higher mass resolution. It measures 90cm long×70cm wide×170cm high, weights ∼170kg and has a total power consumption of less than 2000W. Standard polystyrene latex particles (PSL) and metallic solution were used to perform size and mass calibration, respectively, and the effect of inlet pressure of the aerodynamic lens on size calibration was also investigated. The instrument was first used for the ambient aerosol detection in Guangzhou City, China, and the preliminary measurements show its’ ability to characterize the atmospheric aerosol particles containing different chemical compositions with diameters ranging from 250 to 2000nm and a total hit rate above 30%. The preliminary measurements also show that the aerosol particles in Guangzhou, China can be mainly classified into five types, which are rich K, rich Na, Nark, carbonaceous, and metal containing, and their formations are also generally discussed. [Copyright &y& Elsevier]

Abstract: The concentrations and compositions of free and bound organic acids in total suspended particles from typical urban, suburban and forest park sites of Guangzhou were determined in this study. The free form of organic acids (solvent extractable) in aerosols in Guangzhou varied with site and season. The suburban samples contained the highest contents of alkanoic, alkenoic and dicarboxylic acids. These findings were consistent with a higher supply of hydrocarbons and NOx in the suburban area. However, concentrations of aromatic acids were similar in the urban, suburban and forest park sites. Generally, winter season samples of the acids from anthropogenic sources contained more organic acids than summer season samples due to stronger removal by wet deposition in the summer. For the acids from botanic sources, the summer season samples were higher. In addition to the free acids, bound acids (solvent non-extractable) mainly formed by esterification of free acids were also found in the samples. In general, bound acids were higher than free acids. Esterification is mainly controlled by the pKa of organic acids and the atmospheric pH value. This explains why aromatic and dicarboxylic acids occur mainly as bound forms and why the samples from urban sites contained high levels of bound acids as the pH of rain water can reach 4.53. Concentrations of alkanoic and alkenoic acids in the aerosols of Guangzhou were much higher than those in the other areas studied. [ABSTRACT FROM AUTHOR]

PM2. 5 samples were collected at five sites in Guangzhou and Hong Kong, Pearl River Delta Region (PRDR), China in both summer and winter during 2004–2005. Elemental carbon (EC) and organic carbon (OC) in these samples were measured. The OC and EC concentrations ranked in the order of urban Guangzhou > urban Hong Kong > background Hong Kong. Total carbonaceous aerosol (TCA) contributed less to PM2. 5 in urban Guangzhou (32–35%) than that in urban Hong Kong (43–57%). The reason may be that, as an major industrial city in South China, Guangzhou would receive large amounts of inorganic aerosol from all kinds of industries, however, as a trade center and seaport, urban Hong Kong would mainly receive organic aerosol and EC from container vessels and heavy-duty diesel trucks. At Hong Kong background site Hok Tsui, relatively lower contribution of TCA to PM2. 5 may result from contributions of marine inorganic aerosol and inland China pollutant. Strong correlation (R 2=0. 76–0. 83) between OC and EC indicates minor fluctuation of emission and the secondary organic aerosol (SOA) formation in urban Guangzhou. Weak correlation between OC and EC in Hong Kong can be related to the impact of the long-range transported aerosol from inland China. Averagely, secondary OC (SOC) concentrations were 3. 8–5. 9 and 10. 2–12. 8μgm−3, respectively, accounting for 21–32% and 36–42% of OC in summer and winter in Guangzhou. The average values of 4. 2–6. 8% for SOA/ PM2. 5 indicate that SOA was minor component in PM2. 5 in Guangzhou. [Copyright &y& Elsevier]

Abstract: Indoor and outdoor concentration levels of 21 carbonyl compounds and five BTEX (benzene, toluene, ethylbenzene and xylenes) were measured in four hospitals of Guangzhou from 2nd January to 20th March 2004. Samples were collected in five consecutive daytimes for each hospital. Among most of the samples, acetone was the most abundant carbonyl, followed by acetaldehyde, 2-butanone or formaldehyde. Toluene was the most abundant BTEX and the others were at similar levels. The relatively higher acetone concentrations might have resulted from the high level of background in Guangzhou area due to emission of the factories and LPG-fuel vehicles, and also for the special weather conditions during sampling time. The high concentration of acetaldehyde, which was even higher than that of formaldehyde, might be resulted from the wide use of ethanol in hospital. The partial oxidation of ethanol may form acetaldehyde. The indoor concentrations of carbonyls and BTEX were found a little higher than their outdoor counterparts with only a few exceptions, which showed the anthropogenic sources for these compounds. The low correlations between most carbonyls and BTEX concentrations might be caused by their complex sources. Finally, the human exposure levels of formaldehyde and acetaldehyde in hospitals are discussed. [Copyright &y& Elsevier]

Abstract: Ambient levels of carbonyl compounds and their possible sources, vehicular exhaust and cooking exhaust, were studied at seven places in Guangzhou, including five districts (a residential area, an industrial area, a botanical garden, a downtown area and a semi-rural area), a bus station and a restaurant during the period of June–September 2003. Nineteen carbonyl compounds were identified in the ambient air, of which acetone was the most abundant carbonyl, followed by formaldehyde and acetaldehyde. Only little changes were found in carbonyl concentration levels in the five different districts because of their dispersion and mixture in the atmosphere in summer. The lower correlations between the carbonyls’ concentrations might result from the mixture of carbonyls derived from different sources, including strong photochemical reactions at noon in summer. Formaldehyde and acetaldehyde were the main carbonyls in bus station, while straight-chain carbonyls were comparatively abundant in cooking exhaust. Besides vehicular exhaust, cooking might be another major source of carbonyl compounds in Guangzhou City, especially for high molecular weight carbonyls. [Copyright &y& Elsevier]

Amines are ubiquitous in the environment and pose potential impacts on atmospheric chemistry; however, their seasonal variations and atmospheric processes remain unclear. In this study, a single-particle aerosol mass spectrometer is employed to investigate the seasonal variations of amine-containing particles as well as the oxidation of trimethylamine (TMA) in the urban region of Guangzhou, China. Number fractions of the amine-containing particles exhibit distinct seasonal variations, with higher fractions in spring and summer. Four amines, namely, TMA, diethylamine (DEA), dipropylamine, and tripropylamine are observed over all the seasons. DEA and TMA are the most dominant and account for approximately 90% of all these amine-containing particles. They are mainly clustered into eight types, comprised of internally mixed organics and elemental carbon (OCEC), OC–K, EC, Metal–rich, Dust, NaK–EC, Amine–rich, and high molecular weight organic compounds. DEA and TMA distribute differently over particle types and exhibit a distinct mixing state because of their different physicochemical properties. Compared with TMA, DEA is associated with more sulfate. The possible oxidation of TMA is also investigated, and the results indicate the potential contribution of aqueous oxidation or NO 3 radical oxidation to the formation of TMA oxide. Overall, the results improve the comprehension of the formation and evolution processes of amines in atmospheric environment. • The number fraction of amine-containing particles in spring/summer is higher. • Trimethylamine and diethylamine distribute differently over particle types. • Compared with trimethylamine, diethylamine is associated with more sulfate. • A large fraction of trimethylamine is observed to be oxidized mainly at night. [ABSTRACT FROM AUTHOR]