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Carbonaceous aerosols represent an important nexus between air pollution and climate change. Here we collected filter-based PM2.5 samples during summer and autumn in 2015 at one urban and two rural sites in Guangzhou, a megacity in southern China, and got the light absorption by black carbon (BC) and brown carbon (BrC) resolved with a DRI Model 2015 multi-wavelength thermal/optical carbon analyzer apart from determining the organic carbon (OC) and elemental carbon (EC) contents. On average BrC contributed 12-15% of the measured absorption at 405nm (LA405) during summer and 15-19% during autumn with significant increase in the LA405 by BrC at the rural sites. Carbonaceous aerosols, identified as total carbon (TC), yielded average mass absorption efficiency at 405nm (MAE405) that were approximately 45% higher in autumn than in summer, an 83% increase was noted in the average MAE405 for OC, compared with an increase of only 14% in the average MAE405 for EC. The LA405 by BrC showed a good correlation (p 0.1) in autumn, implying greater secondary formation of BrC in summer. The correlations between levoglucosan (a marker of biomass burning) and the LA405 by BrC were significant during autumn but insignificant during summer, suggesting that the observed increase in the LA405 by BrC during autumn in rural areas was largely related to biomass burning. The measurements of light absorption at 550nm presented in this study indicated that the use of the IMPROVE algorithm with an MAE value of 10m2/g for EC to approximate light absorption may be appropriate in areas not strongly affected by fossil fuel combustion; however, this practice would underestimate the absorption of light by PM2.5 in areas heavily affected by vehicle exhausts and coal burning.

Photocatalytic microcompartments have attracted increasing interests in the field of photocatalytic degradation. This work focused on the construction and characterization of a novel photocatalytic microsystem comprising polydopamine-modified TiO2 nanoparticles (NPs) dispersed in clay-based colloidosomes, utilizing partially hydrophobic montmorillonite particles as building blocks for colloidosome membrane assembly. Assessment of photocatalytic activity was performed by photocatalytic degradation of methylene blue and rhodamine B, with the small molecule dyes decomposing within the compartmentalized microsystems. Encapsulation of TiO2 NPs within the clay colloidosomes enhanced the efficiency of photocatalytic degradation. The results showed a selective degradation of methylene blue in the presence of rhodamine B, with associated λMB/λRhB of 2.04. The present study indicates that photocatalytic semiconductor NPs encapsulated in clay colloidosomes form a promising microsystem with great potential for application in environmental remediation.

This paper proposes an approach based on Ordinal Optimization (OO) to solve trajectory planning for automated driving. As most planning approaches based on candidate curves optimize the trajectory curve and the velocity profile separately, this paper formulates the problem as an unified Non-Linear Programming (NLP) model, optimizing the trajectory curve and the acceleration profile (acceleration is the derivative of velocity) simultaneously. Then a hybrid optimization algorithm named OODE, developed by combining the idea of OO and Differential Evolution (DE), is proposed to solve the NLP model. With the acceleration profile optimized “roughly”, OODE computes and compares “rough” (biased but computationally-easier) curve evaluations to select the best curve from candidates, so that a good enough curve can be obtained very efficiently. Then the acceleration profile is optimized again “accurately” with the selected curve. Simulation results show that good enough solutions are ensured with a high probability and our method is capable of working in real time.

Sulfur dioxide (SO2) can enhance the formation of secondary aerosols from biogenic volatile organic compounds (VOCs), but its influence on secondary aerosol formation from anthropogenic VOCs, particularly complex mixtures like vehicle exhaust, remains uncertain. Gasoline vehicle exhaust (GVE) and SO2, a typical pollutant from coal burning, are directly co-introduced into a smog chamber, in this study, to investigate the formation of secondary organic aerosols (SOA) and sulfate aerosols through photooxidation. New particle formation was enhanced, while substantial sulfate was formed through the oxidation of SO2 in the presence of high concentration of SO2. Homogenous oxidation by OH radicals contributed a negligible fraction to the conversion of SO2 to sulfate, and instead the oxidation by stabilized Criegee intermediates (sCIs), formed from alkenes in the exhaust reacting with ozone, dominated the conversion of SO2. After 5 h of photochemical aging, GVE's SOA production factor revealed an increase by 60–200 % in the presence of high concentration of SO2. The increase could principally be attributed to acid-catalyzed SOA formation as evidenced by the strong positive linear correlation (R2 = 0.97) between the SOA production factor and in situ particle acidity calculated by the AIM-II model. A high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) resolved OA's relatively lower oxygen-to-carbon (O : C) (0.44 ± 0.02) and higher hydrogen-to-carbon (H : C) (1.40 ± 0.03) molar ratios for the GVE / SO2 mixture, with a significantly lower estimated average carbon oxidation state (OSc) of −0.51 ± 0.06 than −0.19 ± 0.08 for GVE alone. The relative higher mass loading of OA in the experiments with SO2 might be a significant explanation for the lower SOA oxidation degree.

Carbonaceous aerosols represent an important nexus between air pollution and climate change. Here we collected filter-based PM

Based on field observations and thermodynamic model simulation, the annual trend of PM2.5 acidity and its characteristics on non-hazy and hazy days in fall-winter of 2007-2012 in the Pearl River Delta region were investigated. Total acidity ([H(+)](total)) and in-situ acidity ([H(+)](in-situ)) of PM2.5 significantly decreased (F-test, p0.05) at a rate of -32 ± 1.5 nmol m(-3)year(-1) and -9 ± 1.7 nmol m(-3) year(-1), respectively. The variation of acidity was mainly caused by the change of the PM2.5 component, i.e., the decreasing rates of [H(+)](total) and [H(+)](in-situ) due to the decrease of sulfate (SO4(2-)) exceeded the increasing rate caused by the growth of nitrate (NO3(-)). [H(+)](total), [H(+)](in-situ) and liquid water content on hazy days were 0.9-2.2, 1.2-3.5 and 2.0-3.0 times those on non-hazy days, respectively. On hazy days, the concentration of organic matter (OM) showed significant enhancement when [H(+)](in-situ) increased (t-test, p0.05), while this was not observed on non-hazy days. Moreover, when the acidity was low (i.e., R = [NH4(+)]/(2 × [SO4(2-)]+[NO3(-)])0.6), NH4NO3 was most likely formed via homogenous reaction. When the acidity was high (R ≤ 0.6), the gas-phase formation of NH4NO3 was inhibited, and the proportion of NO3(-) produced via heterogeneous reaction of N2O5 became significant.

Residential cooking in China’s urban areas could be a more significant contributor to organic aerosols when compared to restaurant cooking, yet no source profiles are available for Chinese residential cooking. In this study, a typical nine-floor residential apartment building in urban Guangzhou was selected to investigate the particulate mass emissions and chemical compositions of organic aerosols from Chinese residential cooking. During dinner cooking period, the average of total suspended particle (TSP) mass concentrations increased by a factor of 4.40 compared with that during non-cooking period. Organic matter (OM) was the major component of aerosols from cooking, and accounted for 66.9 % of the TSP mass. Over 90 organic species were identified and quantified, and could explain 14.5 % of OC in cooking emissions. Fatty acids alone shared 75.7 % of the total mass of quantified organic compounds, with palmitic acid as the predominant one. Sterols, monosaccharide anhydrides and polyols were also significant compositions and they together contributed 14.3 % in the total mass of the quantified organic compounds. While cholesterol was detected from western-style cooking, phytosterols were additionally observed from Chinese-style cooking, and campesterol and polyols were only reported in the present study. Chinese residential cooking emission showed small differences in composition patterns of organic compounds when compared to previously report Chinese restaurant cooking emissions, however, large differences existed when compared to western style cooking. Using cholesterol as a tracer for cooking emissions, in Guangzhou we found cooking emissions contributed 3.9–8.2 % of OC in PM2.5. Spatial distributions of cooking emission contribution were consistent with the distributions of population.

24-h PM 2.5 samples were simultaneously collected at six sites in a subtropical city of South China during November–December, 2009. Particle-phase concentrations of polycyclic aromatic hydrocarbons (PAHs) and organic tracers such as hopanes for vehicular emissions (VE), levoglucosan for biomass burning (BB) and picene for coal combustion (CC) were determined. Meanwhile, their gas-phase concentrations were calculated from gas/particle (G/P) partitioning theory using the particle-phase concentrations. The 4 ring PAHs (fluoranthene to chrysene) had lower particle-phase fractions (10%–79%) than other species. Estimated BaP eq and lifetime cancer risk for particle-only (P-only) vs gas + particle (G + P) data sets showed similar values, indicating PAHs with 5–7 rings dominated the carcinogenicity of PAHs. Positive Matrix Factorization (PMF) was applied on both P-only and G + P data sets to estimate the source contributions to PAHs and their toxicity. Three common sources were identified: VE, BB and CC, with CC as the most significant source for both particulate (58%) and total (G + P, 40%) PAHs. While CC exhibited consistent contributions to BaP eq for P-only (66%) vs G + P (62%) solutions, VE and BB contributions were under- and overestimated by 68% and 47%, respectively by the P-only solution, as compared to the G + P solution. The results provide an insight on the impact of G/P partitioning on the source apportionment of PAHs and their toxicity.

In the fall and winter of 2007 to 2011, 167 24-h quartz filter-based fine particle (PM2.5) samples were collected at a regional background site in the central Pearl River Delta. The PM2.5 showed an annual reduction trend with a rate of 8.58 μg m(-3) (p0.01). The OC component of the PM2.5 reduced by 1.10 μg m(-3) yr(-1) (p0.01), while the reduction rates of sulfur dioxide (SO2) and sulfate (SO4(2-)) were 10.2 μg m(-3) yr(-1) (p0.01) and 1.72 μg m(-3) yr(-1) (p0.01), respectively. In contrast, nitrogen oxides (NOx) and nitrate (NO(3-)) presented growth trends with rates of 6.73 μg m(-3) yr(-1) (p0.05) and 0.79 μg m(-3) yr(-1) (p0.05), respectively. The PM2.5 reduction was mainly related to the decrease of primary OC and SO4(2-), and the enhanced conversion efficiency of SO2 to SO4(2-) was related to an increase in the atmospheric oxidizing capacity and a decrease in aerosol acidity. The discrepancy between the annual trends of NOx and NO3(-) was attributable to the small proportion of NO3(-) in the total nitrogen budget.Understanding annual variations of PM2.5 and its chemical composition is crucial in enabling policymakers to formulate and implement control strategies on particulate pollution.

Biogenic organosulfates (OSs) are important markers of secondary organic aerosol (SOA) formation involving cross reactions of biogenic precursors (terpenoids) with anthropogenic pollutants. Until now, there has been rare information about biogenic OSs in the air of highly polluted areas. In this study, fine particle (PM2.5) samples were separately collected in daytime and nighttime from summer to fall 2010 at a site in the central Pearl River Delta (PRD), South China. Pinene-derived nitrooxy-organosulfates (pNOSs) and isoprene-derived OSs (iOSs) were quantified using a liquid chromatograph (LC) coupled with a tandem mass spectrometer (MS/MS) operated in negative electrospray ionization (ESI) mode. The pNOSs with MW 295 exhibited higher levels in fall (151 ± 86.9 ng m(-3)) than summer (52.4 ± 34.0 ng m(-3)), probably owing to the elevated levels of NOx and sulfate in fall when air masses mainly passed through city clusters in the PRD and biomass burning was enhanced. In contrast to observations elsewhere where higher levels occurred at nighttime, pNOS levels in the PRD were higher during the daytime in both seasons, indicating that pNOS formation was likely driven by photochemistry over the PRD. This conclusion is supported by several lines of evidence: the specific pNOS which could be formed through both daytime photochemistry and nighttime NO3 chemistry exhibited no day-night variation in abundance relative to other pNOS isomers; the production of the hydroxynitrate that is the key precursor for this specific pNOS was found to be significant through photochemistry but negligible through NO3 chemistry based on the mechanisms in the Master Chemical Mechanism (MCM). For iOSs, 2-methyltetrol sulfate ester which could be formed from isoprene-derived epoxydiols (IEPOX) under low-NOx conditions showed low concentrations (below the detection limit to 2.09 ng m(-3)), largely due to the depression of IEPOX formation by the high NOx levels over the PRD.

For intelligent vehicles, trajectory prediction for their surrounding traffic participants is the basis of their ego trajectory planning. Since there exist various uncertain factors that influence the driving processes, the participants' future trajectories are uncertain either. Unique deterministic prediction results provided by traditional methods do not involve the probability information of different trajectories, and thus are insufficient. To solve this problem, a probabilistic trajectory prediction model is proposed here, and uncertain future trajectories are designed to be described with position probability distributions at discrete moments. In the proposed model, the predicted participant's motion is decomposed into lateral and longitudinal motions which are independent with each other. Probabilistic trajectories are calculated in these two directions respectively and then are combined into complete ones. Furthermore, the model considers two driving modes(Free driving and Vehicle-following modes) in the longitudinal motion, and thus computes trajectories in different ways. Besides, we also modeled the features of different types of participants and the interaction between their trajectories. Model parameters are identified off-line based on historical trajectory data, therefore only iterative computations are needed when the model is applied on-line. The experimental results show that the proposed method has higher prediction accuracy than the traditional ones, and can meet the demands of real-time applications.

Organic acids as important constituents of organic aerosols not only influence the aerosols' hygroscopic property, but also enhance the formation of new particles and secondary organic aerosols. This study reported organic acids including C14-C32 fatty acids, C4-C9 dicarboxylic acids and aromatic acids in PM2.5 collected during winter 2009 at six typical urban, suburban and rural sites in the Pearl River Delta region. Averaged concentrations of C14-C32 fatty acids, aromatic acids and C4-C9 dicarboxylic acids were 157, 72.5 and 50.7 ng/m3, respectively. They totally accounted for 1.7% of measured organic carbon. C20-C32 fatty acids mainly deriving from higher plant wax showed the highest concentration at the upwind rural site with more vegetation around, while C14-C18 fatty acids were more abundant at urban and suburban sites, and dicarboxylic acids and aromatic acids except 1,4-phthalic acid peaked at the downwind rural site. Succinic and azelaic acid were the most abundant among C4-C9 dicarboxylic acids, and 1,2-phthalic and 1,4-phthalic acid were dominant aromatic acids. Dicarboxylic acids and aromatic acids exhibited significant mutual correlations except for 1,4-phthalic acid, which was probably primarily emitted from combustion of solid wastes containing polyethylene terephthalate plastics. Spatial patterns and correlations with typical source tracers suggested that C14-C32 fatty acids were mainly primary while dicarboxylic and aromatic acids were largely secondary. Principal component analysis resolved six sources including biomass burning, natural higher plant wax, two mixed anthropogenic and two secondary sources; further multiple linear regression revealed their contributions to individual organic acids. It turned out that more than 70% of C14-C18 fatty acids were attributed to anthropogenic sources, about 50%-85% of the C20-C32 fatty acids were attributed to natural sources, 80%-95% of dicarboxylic acids and 1,2-phthalic acid were secondary in contrast with that 81% of 1,4-phthalic acid was primary.

In fall-winter, 2007-2013, visibility and light scattering coefficients (bsp) were measured along with PM2.5 mass concentrations and chemical compositions at a background site in the Pearl River Delta (PRD) region. The daily average visibility increased significantly (p

In January 2013, a long-lasting severe haze episode occurred in Northern and Central China; at its maximum, it covered a land area of approximately 1.4 million km(2). In Wuhan, the largest city in Central China, this event was the most severe haze episode in the 21st century. Aerosol samples of submicron particles (PM1.0) were collected during the long-lasting haze episode at an urban site and a suburban site in Wuhan to investigate the ion characteristics of PM1.0 in this area. The mass concentrations of PM1.0 and its water-soluble inorganic ions (WSIIs) were almost at the same levels at two sites, which indicates that PM1.0 pollution occurs on a regional scale in Wuhan. WSIIs (Na(+), NH4(+), K(+), Mg(2+), Ca(2+), Cl(-), NO3(-) and SO4(2-)) were the dominant chemical species and constituted up to 48.4% and 47.4% of PM1.0 at WD and TH, respectively. The concentrations of PM1.0 and WSIIs on haze days were approximately two times higher than on normal days. The ion balance calculations indicate that the particles were more acidic on haze days than on normal days. The results of the back trajectory analysis imply that the high concentrations of PM1.0 and its water-soluble inorganic ions may be caused by stagnant weather conditions in Wuhan.

Water-soluble organic carbon (WSOC) is a major component of carbonaceous aerosols. However, the detailed information of WSOC origins is still unclear. In the current study, fine particles (PM2.5) were collected at one sub-urban and two rural sites in the Pearl River Delta (PRD) region, south China during fall–winter 2008 to measure WSOC and organic tracers of biomass burning (BB) and secondary organic aerosols (SOA) from isoprene, monoterpenes, β-caryophyllene, aromatics and 2-ring polycyclic aromatic hydrocarbons (PAHs). WSOC concentrations ranged from 7.63 to 11.5 μg C m−3 and accounted for 38.8–57.9% of organic carbon (OC). Both WSOC and water-insoluble organic carbon (WIOC) exhibited higher levels at the sub-urban site than the rural sites. Subtracting BB-derived WSOC (WSOCBB) from measured WSOC, secondary OC (SOC) and primary OC (POC) were estimated that POC exhibited dominance over SOC and contributed 68–79% to OC. Significant correlation between WSOC and EC was observed, suggesting that BB could have important contributions to ambient WSOC in the PRD region during fall–winter. Organic tracers were applied to do source apportionment of WSOC, which further confirmed that BB was the dominant contributor, accounting for 42–47% of measured WSOC. SOC estimated by SOA tracers totally contributed 22–40% of WSOC, among which anthropogenic SOC (sum of aromatics and 2-ring PAHs, 18–25%) exhibited dominance over biogenic SOC (sum of isoprene, monoterpenes and β-caryophyllene, 4–15%). The unexplained WSOC (18–31%) showed a positive correlation with POC, indicating that this portion might be associated with POC aging.

Aromatic hydrocarbons (AHs) are both hazardous air pollutants and important precursors to ozone and secondary organic aerosols. Here we investigated 14 C6-C9 AHs at one urban, one suburban and two rural sites in the Pearl River Delta region during November-December 2009. The ratios of individual aromatics to acetylene were compared among these contrasting sites to indicate their difference in source contributions from solvent use and vehicle emissions. Ratios of toluene to benzene (T/B) in urban (1.8) and suburban (1.6) were near that of vehicle emissions. Higher T/B of 2.5 at the rural site downwind the industry zones reflected substantial contribution of solvent use while T/B of 0.8 at the upwind rural site reflected the impact of biomass burning. Source apportionment by positive matrix factorization (PMF) revealed that solvent use, vehicle exhaust and biomass burning altogether accounted for 89-94% of observed AHs. Vehicle exhaust was the major source for benzene with a share of 43-70% and biomass burning in particular contributed 30% to benzene in the upwind rural site; toluene, C8-aromatics and C9-aromatics, however, were mainly from solvent use, with contribution percentages of 47-59%, 52-59% and 41-64%, respectively.

During November-December 2010 aerosol scattering coefficients were monitored using a single-waved (525 nm) Nephelometer at a regional monitoring station in the central Pearl River Delta region and 24-hr fine particle (PM2.5) samples were also collected during the period using quartz filters for the analysis of major chemical components including organic carbon (OC), elemental carbon (EC), sulfate, nitrate and ammonium. In average, these five components accounted for about 85% of PM2.5 mass and contributed 42% (OC), 19% (SO42−), 12% (NO3−), 8.4% (NH4+) and 3.7% (EC), to PM2.5 mass. A relatively higher mass scattering efficiency of 5.3 m2/g was obtained for fine particles based on the linear regression between scattering coefficients and PM2.5 mass concentrations. Chemical extinction budget based on IMPROVE approach revealed that ammonium sulfate, particulate organic matter, ammonium nitrate and EC in average contributed about 32%, 28%, 20% and 6% to the light extinction coefficients, respectively.

[1] Fine particles (PM2.5) were collected using filter-based high-volume samplers during summer-winter 2008 at a rural site in the central Pearl River Delta (PRD), south China, to determine typical secondary organic aerosol (SOA) tracers from significant biogenic (isoprene, monoterpenes, and sesquiterpenes) and anthropogenic (aromatics) precursors. Average isoprene SOA tracers were significantly higher during summer (126 ng m−3) than during fall-winter (25.1 ng m−3), owing largely to the higher isoprene emission and reaction rates in summer. Average monoterpene SOA tracers during summer (11.6 ng m−3) and fall-winter (16.4 ng m−3) showed much less difference compared to isoprene SOA tracers, probably resulting from the counteracting effects of temperature on the precursor emission/tracer formation and on gas/particle partitioning. The concentrations of the aromatics' SOA tracer (2,3-dihydroxy-4-oxopentanoic acid) ranged from 1.70 to 52.0 ng m−3 with an average of 15.1 ng m−3, which was the highest reported in ambient air. The secondary organic carbon (SOC) estimated by the SOA-tracer method averaged 3.07 μg C m−3 in summer and 2.00 μg C m−3 in fall-winter, contributing 38.4% and 8.7% to OC, respectively. During summer, aromatics-SOC and isoprene-SOC reached 2.25 ± 1.5 μg C m−3 and 0.64 ± 0.7 μg C m−3 and accounted for 76% and 18% of the estimated SOC, respectively, while during fall-winter, aromatics-SOC (1.64 ± 1.4 μg C m−3) was dominant with a share of 79% in total estimated SOC. These results indicated that anthropogenic aromatics were dominant SOC precursors in the highly industrialized and urbanized PRD region. During summer, SOC levels estimated by elemental carbon (EC) tracer method were not only consistent with but also correlated well with those by SOA-tracer method. During fall-winter, however, SOC by SOA-tracer method was only about one third of that by EC-tracer method. Their gaps were significantly correlated with the biomass burning tracer levoglucosan, indicating that input from biomass burning emission with very high ratios of OC/EC during fall-winter would result in an overestimate of SOC by EC-tracer method. Therefore cautions should be taken when estimating SOC by EC-tracer method, especially when biomass burning exhibits significant influences.