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Large industrial estates for electrical and electronic waste (e-waste) mechanical dismantling and recycling are gradually replacing outmoded small factories and intensive domestic workshops for e-waste manual and chemical dismantling. However, the air pollution and health risks of persistent organic pollutants during the modern mechanical processing of e-waste, especially obsolete electrical equipment, still remain unclear. Here, unexpectedly high levels (409.3 ng/m 3 ) and health risks of airborne polychlorinated biphenyls (PCBs) were found during the mechanical processing of obsolete electric equipment or parts in a large integrated dismantling industrial estate, which is comparable to or a dozen times higher than those reported during chemical processing. In contrast, the levels (936.0 pg/m 3 ) and health risks of particulate polybrominated diphenyl ethers (PBDEs) were all lower than those of previous studies. PCB emissions (44.9-3300.5 ng/m 3 ) varied significantly across six mechanical dismantling places specifically treating waste motors, electrical appliances, hardware, transformers, and metals, respectively. The high PCB content and mass processing number of obsolete electrical equipment probably result in the highest PCB emissions from the mechanical dismantling of obsolete motors, followed by waste electrical appliances and metals. The PCB non-cancer and cancer risks associated with inhalation and dermal exposure in different mechanical dismantling places were all above the given potential risk limits. In particular, the health risks of dismantling obsolete motor exceeded the definite risk levels. Little difference in PCB emissions and health risks between working and non-working time suggested the importance of PCB volatilization from most e-waste. Such high PCB emissions and health risks of PCBs undoubtedly posed a severe threat to frontline workers, but fortunately, they decreased significantly with the increasing distance from the industrial estate. We highlight that PCB emissions and associated health risks from obsolete electrical equipment with high PCB content during mechanical dismantling activities should be of great concern., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

Dyes adsorption to biochar via hydrogen bonding, and π-π interaction alone have attracted much research attention, however, their synergism in adsorption mechanisms remains largely unnoticed. The synergistic effects of the hydrogen bonding and π-π interaction might improve the adsorption capacity and need more understanding to prepare high-capacity biochar. In this work, we evaluated the adsorption of various dyes on biochar prepared via the activation of potassium bicarbonate and urea (named BC-KN) to explore their synergistic effects. Batch experiments indicated the BC-KN showed a high adsorption capacity to rhodamine B at 4839.0 mg/g, azure B at 4477.7 mg/g, and methylene blue at 2223.0 mg/g, respectively. The mechanism of such significant adsorption was investigated by their comparative experiments, characterizations, and computational analyses. The computational analyses suggested that the synergism of the hydrogen bonding and π-π interaction improves the adsorption energies of BC-KN/RhB system from -10.35 kcal/mol to -20.49 kcal/mol. It can be concluded that the hydrogen bonding and π-π interaction can synergize to significantly improve the adsorption by increasing the π-electron density and shortening the distance of aromatic rings, thus dyes with H-donor show significantly better adsorption capacities. The insight of hydrogen bonding being the governing factor in the synergistic system will help produce high-capacity biochar in removing aromatic dyes and suggest a sustainable technology for the efficient decolorization of dye effluent to minimize its damage to the health and environment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Precise recognition of near-infrared (NIR) signals holds great prospects in optical communication, remote sensing, information security, and anti-counterfeiting. For these applications, filters with good NIR transparency are typically essential components. Currently, such NIR transparent filters are dominated by inorganic materials such as chalcogenide glasses. There are, so far, only a handful of organic molecules with suitable optical properties due to the rarity of organic materials with good NIR transparency and relatively flat absorption over the UV-visible region. Here, it is found that the library of NIR-transparent organic materials can be expanded by forming a charge-transfer complex (CTC) between a donor (D) and an acceptor (A) molecule that are commercially available. Via regulating the DA interaction, the CTC filter shows tunable absorption from the visible to NIR region with a relatively high penetration of NIR radiation (≈80%). The CTC filter can successfully highlight NIR information hidden in a complex environment and allow reading of NIR security images for advanced anti-counterfeiting. Moreover, the CTC filter can be used for viewing protected NIR information with good resolution, and thus provide a convenient tool for different security applications using NIR-encoded information., (© 2022 Wiley-VCH GmbH.)

Humic-like substances (HULIS) are macromolecular complex groups in water-soluble organic compounds (WSOC). pH is a crucial factor that influences the chemical transformations of HULIS in atmospheric particles, but this has been rarely investigated, especially under varying pH conditions. This study attempted to unveil the chemical transformation mechanisms of HULIS under a range of pH conditions using optical methods. The pH-dependent light absorption and fluorescence properties of HULIS were comprehensively analyzed; the acidity coefficient (p K a ) of HULIS in relation to chemical structures was determined, and the hypothetical chemical transformation mechanisms of HULIS with increasing pH were analyzed by optical characterizations. The results suggested that pH greatly impacted the light absorption and fluorescence efficiencies of HULIS in both winter and summer seasons, and p K a was an important inflection point. The p K a of HULIS ranged from 3.5 to 8.0 in winter and 6.4 to 10.0 in summer. The acidic/basic groups were identified as -OH or -NH 2 substituted quinolines, carboxylic aromatics, and pyridines. The pH-sensitive species accounted for about 6% and 21% of HULIS-C (carbon concentrations of HULIS) in winter and summer, respectively. The varying optical spectra with increasing pH might result from charge transfer or complex reactions with HULIS deprotonation.

Water-soluble organic compounds (WSOC) have a significant impact on aerosol radiative forcing and climate change, and there is considerable uncertainty in predicting and mitigating their climate and environmental effects. Here, the effects of pH on the light absorption properties of WSOC in particulate matter from different typical emission sources and ambient aerosols were systematically investigated using UV-vis spectrophotometer. pH (2-10) had an important impact on the light absorption properties of WSOC. The absorption, aromaticity, and the light absorption capacity of WSOC increased significantly with increasing pH for all samples. The difference absorbance spectra (∆absorbance) showed that the change of light absorption properties with pH was related to the deprotonate of carboxyl and phenolic groups resonating with aromatic and conjugated systems, with the most likely structures being carboxylic acids and phenols. Coal combustion and summer samples exhibited much higher susceptibility of light absorption properties to pH variation (increased by 27.0% and 65.9% relative to the pH 2 level, respectively). Absorption indices of almost all samples were significantly correlated with pH, indicating that the light absorption properties of WSOC may be quantitatively related to pH. The pH-dependent light absorption properties may have profound implications for evaluating the climate impacts of aerosol WSOC such as radiative forcing., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The fragile aquatic ecosystem on the Tibetan Plateau is severely threatened by human activities and climate change. Dissolved organic matter (DOM) is a vital indicator of surface water quality; however, its comprehensive molecular analysis is challenged due to its low concentration (total organic carbon less than 0.5 mg/L) in alpine areas. This study proposes the fluorescence excitation-emission matrix (FEEM) to fingerprint DOM in a typical headstream in the Namco basin, one of the largest lake regions in Tibet. We found that the FEEM can sensitively detect low-concentration pollution traces and the variation of DOM along the flow from the ice sheet, through the wetland, eventually to the estuary of the lake. The fluorescence intensity indices for biodegradable carbon (f T/C ) and humification (HIX em ) responded drastically along the flow. Fluorescence regional integrals (FRIs) clearly reflected the overall increase of protein-like substances and decrease of humus-like substances along the flow, whereas this tendency was reversed when passing through the wetland. The FRIs-derived secondary parameters (HPP, HMP, WLP and SSP) further sensed likely variations in hydrophobicity, humification degree, excited-state fluorophore energy and Stokes shift. Parallel factor analysis (PARAFAC) and two-dimensional correlation spectroscopy (2DCOS) of the FEEM signals witnessed the trade-off among tyrosine-like organics (C1 peak), tryptophan-like byproducts (C2 peak) and humus-like remains (C3 peak) along the flow. The C1 component can be traced back to the vicinity of the ice sheet exit, presumably due to human and animal activities. The wetland can absorb or convert part of the C1 component into C2 or C3 products, demonstrating the function of regulating water quality and buffering environmental impacts. The spectroscopic indicators evaluated in this study may provide tools for diagnosing early traces of water pollution and ecological instability in alpine areas., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Perovskite light-emitting diodes (LEDs) show great potential for next-generation lighting and display technology. Despite intensive studies on single-color devices, there are few reports on perovskite-based white LEDs (Pe-WLEDs). Here, an efficient Pe-WLED based on a blue perovskite and an orange phosphorescent emitter is reported for the first time. It is found that using a simple perovskite/phosphor bilayer emitting structure, there is inefficient energy transfer from the blue perovskite to the orange phosphor, leading to low efficiency and a significant color shift with driving voltage. We address this issue by introducing a quantum-well-like charge-confinement structure for enhancing carrier trapping and thus exciton formation in the phosphorescent emitter. As a result, a high external quantum efficiency of 10.81% is obtained. More interestingly, by tuning the dopant concentration of the phosphorescent emitter using this simple device structure, we can controllably get Pe-WLEDs with very stable white light for display applications or tunable color from warm white to daylight for lighting applications.

Characteristics of atmospheric VOCs (volatile organic compounds) have been extensively studied in megacities in China, however, they are scarcely investigated in medium/small-sized cities in North China Plain (NCP). A comprehensive research on possible sources of VOCs was conducted in a medium-sized city of NCP, from May to September 2019. A total of 143 canister samples of 8 sites in Xuchang city were collected, and 57 VOC species were detected. The average VOC concentrations were 42.6 ± 31.6 μg/m 3 , with 53.7 ± 31.0 μg/m 3 and 32.1 ± 27. 8 μg/m 3 , in the morning and afternoon, respectively. Alkenes and aromatics contributed 80% of the total ozone formation potential (OFP). Aromatics accounted for more than 95% of secondary organic aerosol potential (SOAP). VOCs were dominated by the local emission with significant transport from the southeast direction. PMF analysis extracted 6 sources, which were combustion (33.1%), LPG usage (19.3%), vehicular exhaust & fuel evaporation (15.8%), solvent usage (15.2%), industrial (9.11%) and biogenic (7.51%), respectively and they contributed 33.4%, 17.6%, 12.9%, 18.6%, 9.28% and 8.22% to the OFP, respectively. Combustion and LPG usage were the dominant VOC sources; and combustion, solvent usage and LPG usage were the main sources of OFP in Xuchang city, which were different to megacities in China with a high contribution from vehicular exhaust, solvent usage and industry, suggesting specific control strategies on VOCs need to be implemented in medium-sized city such as Xuchang city., (Copyright © 2020. Published by Elsevier B.V.)

A bromine-substituted thermally activated delayed fluorescent (TADF) molecule AQCzBr2 is designed with both small singlet-triplet splitting (ΔEST) and increased spin-orbit coupling (SOC) to boost intersystem crossing (ISC) for singlet oxygen generation. AQCzBr2 nanoparticles (NPs) demonstrate high productivity of singlet oxygen generation (ΦΔ = 0.91) which allows highly efficient photodynamic therapy toward cancer cells.

Extensive recent efforts have been put on the design of high-performance organic near-infrared (NIR) photothermal agents (PTAs), especially over NIR-II bio-window (1000-1350 nm). So far, the development is mainly limited by the rarity of molecules with good NIR-II response. Here, we report organic nanoparticles of intermolecular charge-transfer complexes (CTCs) with easily programmable optical absorption. By employing different common donor and acceptor molecules to form CTC nanoparticles (CT NPs), absorption peaks of CT NPs can be controllably tuned from the NIR-I to NIR-II region. Notably, CT NPs formed with perylene and TCNQ have a considerably red-shifted absorption peak at 1040 nm and achieves a good photothermal conversion efficiency of 42 % under 1064 nm excitation. These nanoparticles were used for antibacterial application with effective activity towards both Gram-negative and Gram-positive bacteria. This work opens a new avenue into the development of efficient PTAs., (© 2021 Wiley-VCH GmbH.)

Taking Cu and Zn as examples, the pH-dependent interactions between atmospheric heavy metals (AHMs) and water-soluble organic compounds (WSOCs) in PM 2.5 were analyzed by a combination of UV-vis absorption, Fourier transform infrared (FTIR) spectroscopy and excitation-emission matrix (EEM) fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC). We found metal-H ion exchange, complexation and electrostatic adsorption might occur between AHMs and WSOCs, and were generally enhanced with the increase of pH. Furthermore, these interactions were strengthened with the stepwise addition of [Cu 2+ ] (from 0 to 500 μmol·L -1 ), but had a relatively slight change with the stepwise addition of [Zn 2+ ] (from 0 to 500 μmol·L -1 ) generally. This indicated that the above interactions depended on the types and the concentrations of AHMs. Carboxyl, hydroxyl, carbonyl and aromatic structures of WSOCs were the major binding sites with AHMs. Humic acid-like substances were the dominant components of WSOCs binding with AHMs. The ratios of the apparent fluorescence quantum yields of the low and the high conjugation fractions of WSOCs (Q ExL/H ) declined by more than 28% as adding [Cu 2+ ], indicating the formers had more strong complexing capacity with AHMs. AHMs might significantly impact the light absorption capacity and the wavelength dependence of WSOCs. The humification index (HIX em ) declined more than 15% as adding [Cu 2+ ] at pH 5.6 and 7.5, indicating AHMs might weaken the oxidation capacity of WSOCs. These results implied the interactions between AHMs and WSOCs might play a profound role in atmospheric environment, human health, and global climate change., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

A novel core-shell magnetic Prussian blue-coated Fe 3 O 4 composites (Fe 3 O 4 @PB) were designed and synthesized by in-situ replication and controlled etching of iron oxide (Fe 3 O 4 ) to eliminate Cd (II) from micro-polluted water. The core-shell structure was confirmed by TEM, and the composites were characterized by XRD and FTIR. The pore diameter distribution from BET measurement revealed the micropore-dominated structure of Fe 3 O 4 @PB. The effects of adsorbents dosage, pH, and co-existing ions were investigated. Batch results revealed that the Cd (II) adsorption was very fast initially and reached equilibrium after 4 h. A pH of 6 was favorable for Cd (II) adsorption on Fe 3 O 4 @PB. The adsorption rate reached 98.78% at an initial Cd (II) concentration of 100 μg/L. The adsorption kinetics indicated that the pseudo-first-order and Elovich models could best describe the Cd (II) adsorption onto Fe 3 O 4 @PB, indicating that the sorption of Cd (II) ions on the binding sites of Fe 3 O 4 @PB was the main rate-limiting step of adsorption. The adsorption isotherm well fitted the Freundlich model with a maximum capacity of 9.25 mg·g -1 of Cd (II). The adsorption of Cd (II) on the Fe 3 O 4 @PB was affected by co-existing ions, including Cu (II), Ni (II), and Zn (II), due to the competitive effect of the co-adsorption of Cd (II) with other co-existing ions.

Organic small molecule-based phototheranostics hold great promise for clinical translation by virtue of their distinct chemical structure, easy reproducibility, and high purity. However, reported molecular agents typically have relatively low optical absorbances, particularly over the near-infrared (NIR) region, and this limits their phototheranostic performance. Herein, we first exploit a diradicaloid molecular structure for enhancing NIR absorption to facilitate efficient photoacoustic imaging (PAI)-guided photothermal therapy (PTT). The donor-acceptor interaction in the diradicaloid molecule (DRM) leads to strong charge transfer resulting on obvious diradical characteristics, which is beneficial for NIR absorption. The DRM possesses excellent light-harvesting ability, with a mass extinction coefficient of ∼220 L g -1 cm -1 , which is much higher than those (∼5-100 L g -1 cm -1 ) of typical organic molecules. After assembling into nanoparticles, they show good water dispersibility, good photostability, and impressive performance for PAI-guided PTT in vitro and in vivo . The impressive in vitro and in vivo performances show that developing small molecules with diradicaloid structures can be an effective approach for enhancing NIR harvesting capability for biomedical applications.

Photodynamic therapy (PDT) synergized photothermal therapy (PTT) shows superior clinical application prospects than single PDT or PTT. On the other hand, multimodal imaging can delineate comprehensive information about the lesion site and thus help to improve therapy accuracy. However, integrating all these functions into one single molecule is challenging, let alone balancing and maximizing the efficacy of each function. Herein, a near-infrared (NIR) small molecule (ETTC) with an "acceptor-donor-acceptor" structure was designed and synthesized by coupling rigity and flexibility to simultaneously achieve NIR-II fluorescence imaging (NIR-II FLI), photoacoustic imaging, PTT and PDT. The efficacy of each functionality was well balanced and optimized (NIR-II quantum yield: 3.0%; reactive oxygen species generation: 3.2-fold higher than ICG; photothermal conversion efficiency: 52.8%), which may be attributed to the coupling of the rigid and flexible structures in ETTC to tactically manipulate the energy dissipation paths (non-radiative against radiative decay). As a proof-of-concept, under the effective guidance of local-tumor imaging by PA and whole-body imaging by NIR-II FL, complete tumor eradication was achieved via PDT and PTT combinational therapy. This work provides a novel perspective into conceiving and developing single molecule for efficient versatile biomedical applications.

The excitation-emission matrix (EEM) fluorescence spectroscopy was used to characterize the fluorescence properties of water-soluble organic compounds (WSOCs) in PM 2.5 coupled with parallel factor analysis (PARAFAC). Three main components of WSOCs were extracted from PM 2.5 , i.e., humic-like (fulvic acid-like and humic acid-like) substances (HULIS), and soluble microbial by-product-like or aromatic protein-like, respectively. A fluorescence quenching experiment was designed to systematically analyze the interaction laws of atmospheric heavy metal ions and WSOCs in PM 2.5 . Our study revealed HULIS, especially the humic acid-like substances, might be principal substances binding with metal ions and the strength of interactions was related to the types and concentrations of metal ions. Furthermore, EEM was a powerful tool to understand the interaction laws of atmospheric heavy metal ions and WSOCs in PM 2.5 . This work implied that the interactions of atmospheric heavy metal ions and WSOCs might directly or indirectly play a significant role in atmospheric environment and public health., (Copyright © 2020. Published by Elsevier B.V.)

Excitation-emission matrix (EEM) fluorescence spectroscopy is a powerful tool for the characterization of dissolved organic matter (DOM) in wastewater systems. It is of particular value if its utility could be extended by connecting the spectral features to hydrophobicity, one of the fundamental physicochemical properties of DOM. In this study, we employed a DAX-8 resin column to fractionate the hydrophobic/philic components of DOM and determine the relative degree of hydrophobicity by adjusting the critical retention factor (k' cr , the ratio of treated water sample volume to column volume). A higher k' cr would result in a higher hydrophobicity of the column effluent. At different k' cr values (5, 10, 25, 50, 100, and 200), the EEM characteristics of the obtained DOM components were inspected, including overall properties (average fluorescence per total organic carbon and UV absorbance), regional properties (fluorescence regional integration (FRI) and its secondary parameters), and energy-related properties (energy level of the excited states, Stokes shift for relaxation of the excited states, and fluorescence lifetime). In case studies of a wastewater membrane bioreactor and an oxidation ditch, plenty of the EEM properties varied significantly with logk' cr (r > 0.9, p < 0.05). The average fluorescence per UV absorbance (reflecting quantum yield), fluorescence proportion at Stokes shift ≥ 1.1 μm -1 , and some secondary FRI parameters presented the best linear fitting with logk' cr , suggesting a smooth variation of the π-conjugated structures with the relative degree of DOM hydrophobicity. This may help to further understand the relationship between EEM fingerprints and DOM hydrophobicity., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Polymeric carbon nitrides (CNs) have been identified as attractive photocatalysts owing to their comparatively low cost and facile modification of their electronic structure. Herein, we report an effective strategy to tune the surface oxygen species linking site of polymeric CN, achieving more effective charge separation. A high photocatalytic hydrogen production rate of approximately 10225 μmol h -1  g -1 under visible light irradiation (λ>420 nm) and an impressive apparent quantum efficiency (AQE) of 5.7 % at 430 nm were recorded. Specifically, thermal treatment under a H 2 and then an air atmosphere allowed the oxygen species linker on the surface of CN to be changed from -C=O to N=C-OH and then -C-O-C-, resulting in unbalanced charge distribution, which significantly enhanced the photogenerated charge separation, further contributing to the high hydrogen production performance. This linker regulation strategy may provide a new path for the development of highly efficient photocatalysts., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Invited for this month's cover is the research group of Rongzhi Chen at the University of Chinese Academy of Sciences and Xinming Wang at Guangzhou Institute of Geochemistry, Chinese Academy of Sciences. The image proposes an effective strategy to tune bonded oxygen species of carbon nitride for improving photocatalytic hydrogen production. The Full Paper itself is available at 10.1002/cssc.202001027., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Since the implementation of the "Air Pollution Prevention and Control Action Plan" (APPCAP) in 2013, the air quality in China has been greatly improved but still much exceeded the WHO guideline limit. Here we employed a novel approach, two-dimensional Si fingerprints, including stable Si isotopic composition (δ 30 Si and Si abundance (Si%), to investigate the annual variations in both primary and secondary sources of PM 2.5 in Beijing during the APPCAP period (2013-2017). The δ 30 Si and Si% values were used as tracers to reflect the variations in primary and secondary sources, respectively. For primary sources, the mean δ 30 Si value of PM 2.5 in 2015-2017 (>-0.5‰) was significantly more positive than that of 2013 (-1.24‰), indicating a dramatic decline in the contribution of 30 Si-depleted sources (i.e., coal burning and industrial emission). For secondary sources, the mean Si% of PM 2.5 increased from 1.2% in 2013 to 4.6% in 2017, suggesting a large decrease in the secondary aerosol contribution from 83% to 42%. It is worth noting that we found the 30 Si-depleted sources showed a rebound trend during 2015-2017. This study reveals the responses of anthropogenic emission sources under strong regulation policies and provides a reference for future policymaking in Beijing and other polluted regions and countries.

Nanoparticles film of copper metal hexacyanoferrates (CuHCF) was fabricated to electrochemically separate Co 2+ in aqueous solutions under various conditions such as applied potential, solution pHs, initial concentrations, contact time and coexisting ions. Results showed that the removal efficiency conducted in reduction potential was obviously higher than that in oxidation potential. The optimal pH for Co 2+ adsorption occurred at 8.0. Coexisting ions studies revealed that Co 2+ could be removed from aqueous solutions containing Li + , Cu 2+ and Al 3+ . Considering that cobalt and lithium are the main metallic elements in LiCoO 2 , the effect of different ionic strengths (IS) of LiNO 3 (0.5, 1, 2, 5, 10) on adsorption was further investigated. Results showed that IS of LiNO 3 had little impact on the removal efficiency of Co 2+ , which indicated the potential of selective recovery of cobalt from LiCoO 2 in spent lithium-ion batteries. X-ray energy-dispersion spectroscopy (EDS) confirmed that the Co 2+ could be adsorbed effectively onto CuHCF film. The adsorption was well described by Langmuir isotherm and the maximum sorption capacity is 218.82 mg/g. The kinetic rate of Co 2+ adsorption was rapid initially and attained equilibrium within 60 min, and the data well fitted the Redlich-Peterson and the Elovich model, implying a chemisorption dominated process., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In this work, a CoCu alloy magnetic unit was implanted in a photocatalytic system to improve photoinduced charge separation efficiency by regulating the electron transfer pathway via a giant magnetoresistance (GMR) effect, which achieved significantly enhanced hydrogen production activity driven by visible light. The amount of H2 produced in 3 h over the Pt@CoCu alloy decorated graphene (G) photocatalyst was about 12.2 times higher than that of Pt/G, and the highest apparent quantum efficiency (AQE) reached 34.4% at 520 nm.

Hydrophobicity and molecular weight (MW) are two fundamental properties of dissolved organic matter (DOM) in wastewater treatment systems. This study proposes fluorescence Stokes shift and specific fluorescence intensity (SFI) as novel indicators of hydrophobicity and MW. These indicators originate from the energy gap and photon efficiency of the fluorescence process and can be readily extracted from a fluorescence excitation-emission matrix (EEM). The statistical linkages between these indicators and hydrophobicity/MW were explored through investigation of DOM across 10 full-scale membrane bioreactors treating municipal wastewater. Stokes shift was found to exhibit a general rule among the hydrophobicity components in the order of hydrophilic substances (HIS) < hydrophobic acids (HOA) < hydrophobic bases (HOB). The Stokes shift of 1.2 μm -1 is a critical border, above which the relative fluorescence correlated significantly with the HOA-related content (Pearson's r = 0.8). With regard to MW distribution (<1, 1-10, 10-100, and >100 kDa), SFI was found to be the most sensitive to the change of MW of <1 kDa proportion, especially at the excitation/emission wavelengths of 200-320/310-550 nm ( r > 0.9). Hydrophobicity-related π conjugation and MW-dependent light exposure might be responsible for the correlations. These fluorescence indicators may be useful for convenient monitoring of DOM in wastewater treatment systems.

Beijing and its surrounding areas implemented a series of stringent measures to ensure good air quality during the Asia-Pacific Economic Cooperation (APEC) summit. These measures included restrictions on traffic, constructions, and industrial activities. The diurnal variations of carbonyls, 24-h PM 2.5 , and its chemical species were investigated before, during, after APEC, and the 2015 summer. The average concentrations of carbonyls, formaldehyde, acetaldehyde, and acetone were decreased by 65.2%, 78.6%, 41.5%, and 55.6% during APEC, respectively. The concentrations of propene equivalent, the ozone formation potential, and the contribution to OH· removal by carbonyls during APEC were approximately 27-33% of those during the preceding interval. The temporal variation of carbonyls during APEC was similar to that of other air pollutants, except for O 3 ; however, the diurnal variation of carbonyls was consistent with that of O 3 , with the highest values at noon and the lowest ones at night during APEC. Large variations in C1/C2 (0.95-9.41) and C2/C3 (5.70-15.71) were observed during the sampling period. The correlations analysis, diagnostical ratios, and diurnal variations of carbonyls indicated that primary sources were not an important source and secondary formation was the dominant source of atmospheric carbonyls during the entire period. The control measures not only reduced primary carbonyl emissions but also dramatically reduced secondary carbonyl precursors, such as NO x and volatile organic compounds (VOCs), resulting in the low level of carbonyls during APEC. In addition, the potential health effects of carbonyls were evaluated and the cancer risk from formaldehyde and acetaldehyde was significantly higher before APEC than during the other intervals.

Different mole ratios ( n Cu  :  n Ni = x  :  y ) of hybrid copper-nickel metal hexacyanoferrates (Cu x Ni y HCFs) were prepared to explore their morphologies, structure, electrochemical properties and the feasibility of electrochemical adsorption of cobalt ions. Cyclic voltammetry (CV), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) indicated that the x  :  y ratio of Cu x Ni y HCF nanoparticles can be easily controlled as designed using a wet chemical coprecipitation method. The crystallite size and formal potential of Cu x Ni y HCF films showed an insignificant change when 0 ≤ x  :  y < 0.3. Given the shape of the CV curves, this might be due to Cu 2+ ions being inserted into the NiHCF framework as countercations to maintain the electrical neutrality of the structure. On the other hand, crystallite size depended linearly on the x  :  y ratio when x  :  y > 0.3. This is because Cu tended to replace Ni sites in the lattice structure at higher molar ratios of x  :  y . Cu x Ni y HCF films inherited good electrochemical reversibility from the CuHCFs, in view of the cyclic voltammograms; in particular, Cu 1 Ni 2 HCF exhibited long-term cycling stability and high surface coverage. The adsorption of Co 2+ fitted the Langmuir isotherm model well, and the kinetic data can be well described by a pseudo-second order model, which may imply that Co 2+ adsorption is controlled by chemical adsorption. The diffusion process was dominated by both intraparticle diffusion and surface diffusion., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Two novel highly selective quinoline-based fluorescent probes (1 and 2) with an aggregation induced emission (AIE) feature have been designed and synthesized for the rapid analysis of Cu2+ ions in aqueous media and on paper strips with a fluorescence quenching mechanism. Moreover, probes 1 and 2 exhibit excellent sensitivity and anti-interference for Cu2+ detection, and the detection limits are as low as 1.3 × 10-8 M and 8.5 × 10-8 M, respectively, which are much lower than the allowable standard of Cu2+ (∼20 μM) in drinking water (EPA). More importantly, these two probes were successfully applied for the determination of Cu2+ in real aqueous samples and fabrication of simple device test strips for rapid and on-site detection of Cu2+ ions. Interestingly, they can also be regenerated by adding an excess of S2-. Additionally, the crystallographic structure of probe 1 was confirmed through a single crystal X-ray study. Job's plot analysis and ESI-MS spectroscopic studies reflect the 1 : 1 complexation of the 1-Cu2+ and 2-Cu2+ complexes. Furthermore, DFT/TDDFT calculations were performed in order to help in understanding the electronic properties of the complexes and the chelation-induced quenching mechanism.

This study systematically investigated the correlations between fluorescence distributions characterized by the excitation-emission matrix (EEM) and hydrophobic/hydrophilic composition of dissolved organic matter (DOM) in membrane bioreactors (MBRs). On the basis of samples from 10 full-scale MBRs, we performed point-to-point comparisons among different components using an EEM fluorescence quotient (FQ) method and obtained a hydrophobic/hydrophilic fluorophore distribution map via Wilcoxon signed rank test. Hydrophobic acids/bases (HOA/HOB) concentrated in the low-wavelength region [excitation wavelength (Ex) < 235 nm], while hydrophilic substances (HIS) were enriched in the region of Ex > 235 nm [especially with emission wavelength (Em) = 300-360 nm]. Quantitatively, EEM regional contribution to whole wavelength fluorescence was found to significantly correlate with the hydrophobic/hydrophilic proportions of DOM, with Pearson's coefficients of 0.94 and 0.78 ( p < 0.01) for HOA and HIS, respectively. We established a linear regression model showing the HOA proportion as a function of the EEM regional contribution at (Ex, Em) = (200-285, 340-465 nm), with R 2 = 0.876, which was validated via leave-one-out cross-validation and Monte Carlo simulation. This study shows a statistically hydrophobicity-dependent fluorescence property across different MBRs, and it might be applied to provide a quick estimation of hydrophobic/hydrophilic composition of DOM in wastewater treatment systems based on EEM monitoring.

For human health benefits it is crucial to see if carcinogenic air pollutants like polycyclic aromatic hydrocarbons (PAHs) are reduced accordingly along with the control of the criteria pollutants including fine particles (PM 2.5 ). A number of studies documented that enhanced temporary emission control during the 2014 Asia-Pacific Economic Cooperation summit (APEC) in Beijing resulted in substantial drops of observed ambient PM 2.5 , as well as PAHs, in urban areas of Beijing, yet it is not clear whether PM 2.5 -bound PAHs in the rural areas were also lowered during the APEC. Here filter-based PM 2.5 samples were collected at a rural site in northeast of Beijing, and analyzed for 25 PAHs before (Oct. 27-Nov. 2, 2014), during (Nov. 3-12, 2014) and after (Nov. 13, 2014-Jan. 14, 2015) the APEC. Observed concentrations of PM 2.5, OC and EC during the APEC dropped by about 30%, however, average PM 2.5 -bound PAHs and their incremental lifetime cancer risk (ILCR), 25.65 ng/m 3 and 3.2 × 10 -4 , remained almost unchanged when compared to that of 25.48 ng/m 3 and 3.5 × 10 -4 , respectively, before the APEC. After the APEC with the start of wintertime central heating in urban Beijing on Nov. 15, 2014, average total concentration of PAHs and their ILCR highly elevated and reached 118.25 ng/m 3 and 1.5 × 10 -3 , respectively. Source apportioning by positive matrix factorization (PMF) revealed that coal combustion was the largest source that contributed 63.2% (16.1 ng/m 3 ), 78.5% (20.1 ng/m 3 ) and 56.1% (66.3 ng/m 3 ) to the total PAHs before, during and after the APEC, respectively. Uncontrolled residential coal use during the APEC was found to be the reason for unabated levels of PAHs, and the largely aggravated PAHs after the APEC was resulted from increased coal consumption for wintertime residential heating. Our results suggested reducing emission from residential coal combustion is crucial to mitigate carcinogenic PAHs in ambient air, especially in rural areas., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Daily PM 2.5 samples were collected during winter 2012 and summer 2013 at an urban site in Lanzhou and were analyzed for chemical compounds including water soluble inorganic ions (WSIN), trace elements, water soluble organic carbon (WSOC), carbonaceous species (OC/EC), polycyclic aromatic hydrocarbons (PAHs), and humic-like substances (HULIS). The seasonal-average reconstructed PM 2.5 mass was 120.5μgm -3 in winter and 34.1μgm -3 in summer. The top three groups of species in PM 2.5 were OC (35.4±13.9μgm -3 ), WSIN (34.89±14.21μgm -3 ), and EC (13.80±5.41μgm -3 ) in winter and WSIN (11.25±3.25μgm -3 ), OC (9.74±3.30μgm -3 ), and EC (4.44±2.00μgm -3 ) in summer. EC exceeded SO 4 2- on most of the days. Several anthropogenic produced primary pollutants such as PAHs, Cl - , Pb, Cd and OCpri were 4-22 times higher in winter than summer. Carcinogenic substances such as Arsenic, BaP, Pb, and Cd in PM 2.5 exceeded the WHO guideline limits by 274%, 153%, 23% and 7%, respectively. Positive Matric Factorization analysis identified seven source factors including steel industry, secondary aerosols, coal combustion, power plants, vehicle emissions, crustal dust, and smelting industry, which contributed 7.1%, 33.0%, 28.7%, 3.12%, 8.8%, 13.3%, and 6.0%, respectively, to PM 2.5 in winter, and 6.7%, 14.8%, 3.1%, 3.4%, 25.2%, 11.6% and 35.2% in summer. Smelting industry and steel industry were identified for the first time as sources of PM 2.5 in this city, and power plant was distinguished from industrial boiler and residential coal burning., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Based on the field measurements in Barrow, Alaska within the period of April-May 2015, we investigate the sources and variations of elemental carbon (EC) and organic carbon (OC) in the surface layer of snowpack on sea ice, and estimate their effects on the sea ice albedo. Results show that the snow OC in Barrow are from natural sources (e.g. terrestrial higher plants and micro-organisms) mainly, as well as biomass burning (e.g. forest fires and straw combustion) as an important part. Both EC and OC can accumulate at the snow surface with snow melt. The variations in EC and OC and liquid water content in the snow layer are well consistent during the snow-melting period. A higher rate of snow melt implied a more efficient enrichment of EC and OC. In the last phase of snow melt, the concentration increased to a maximum of 16.2 ng/g for EC and 128 ng/g for OC, which is ∼10 times larger than those before snow melt onset. Except for the dominant influence of melt amplification mechanism, the variation in concentrations of EC and OC could be disturbed by the air temperature fluctuation and snowfall. Our study indicates that the light-absorbing impurities contributed 1.6%-5.1% to the reduction in sea ice albedo with melt during the measurement period. The significant period of light-absorbing impurities influencing on sea ice albedo begins with the rapid melting of overlying snow and ends before the melt ponds formed widely, which lasted for about 10 days in Barrow, 2015., (Copyright © 2017 Science China Press. Published by Elsevier B.V. All rights reserved.)

Evaporative light scattering detection (ELSD) was applied to quantify HULIS (humic-like substances) for the first time in 2012 winter and 2013 summer at an urban site in Lanzhou. Water soluble organic carbon (WSOC), water soluble inorganic ions, and carbonaceous species (OC/EC) were also analyzed. The results show that OM (Organic Matter=OC×1.6, constituting 45.8% to PM 2.5 ) was the most abundant species, followed by SNA (SO 4 2- +NO 3 - +NH 4 + , constituting 23.4% to PM 2.5 ). The chemical species were in the order of: OC>EC>SO 4 2- >NO 3 - >NH 4 + >Cl - >Ca 2+ >K + . The annual average concentration of HULIS was 4.70μg/m -3 and HULISc (carbon content of HULIS) contributed 6.19% to PM 2.5 and 45.6% to WSOC, indicating that HULIS was the most important components of WSOC. The concentration of HULIS was 2.14±0.80μg/m 3 in summer and 7.24±2.77μg/m 3 in winter, respectively. The concentrations of HULIS were relatively low and stable in summer, while high and varied dramatically in winter. The abundance of HULISc in WSOC shows a more concentrated distribution in Lanzhou, with a range between 0.28-0.57. The ratios of HULIS/K + were 6.25±1.41 and 6.14±1.96 in summer and winter, respectively, suggesting there were other significant sources in addition to biomass burning emissions. HULIS and WSOC exhibited similar seasonal variation and had a strong positive correlation. In addition to the good relationship (0.89) between HULIS and Cl - in winter, the great enhancement of HULIS with significantly high Cl - and relatively low K + in winter indicated that residential coal burning was probably an important HULIS source in winter. Correlation and back trajectory analysis suggested that biomass burning and secondary formation were also important HULIS sources and the contribution of HULIS from dust could be neglected. Adverse meteorological conditions were also important factors for the accumulation of HULIS in winter., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Foshan is a major international ceramic center and the most polluted city in the Pearl River Delta (PRD). Here we present the results of the first long-term PM2.5 (particles <2.5μm) sampling and chemical characterization study of the city. A total of 2774 samples were collected at six sites from 2008 to 2014, and analyzed for water soluble species, elements and carbonaceous species. The major constituents of PM2.5 were sulfate, OC (Organic Carbon), nitrate, ammonium and EC (Elemental Carbon), which accounted for 50%-88% of PM2.5. PM2.5 and the most abundant chemical species decreased from 2008 to 2011, but rebounded in 2012-2013. After 2008, the chemical composition of PM2.5 changed dramatically due to the implementation of pollution control measures. From 2008 to 2011, SO4(2-) and NO3(-) were the two largest components; subsequently, however, OC was the largest component. The respective contributions of SO4(2-), NO3(-) and OC to the sum of water soluble species and carbonaceous species were 30.5%, 22.9% and 19.9% in 2008; and 20.2%, 16.5% and 30.2% in 2014. Distinct differences in nitrate and sulfate, and in mass ratio [NO3(-)]/[SO4(2-)] imply that mobile sources tended to more important in Foshan during 2012-2014. The results indicate that pollution control measures implemented during 2008-2014 had a large effect on anthropogenic elements (Pb, As, Cd, Zn and Cu) and water soluble species, but little influence on crustal elements (V, Mn, Ti, Ba and Fe) and carbonaceous species. The PMF method was used for source apportionment of PM2.5. Industry (including the ceramic industry and coal combustion), vehicles and dust were the three most important sources and comprised 39.2%, 20.0% and 18.4% of PM2.5 in 2008, respectively. However, secondary aerosols, vehicles and industry were the three most important sources and comprised 29.5%, 22.4% and 20.4% of PM2.5 in 2014, respectively. During the seven year study interval, the contributions of primary sources (industry and dust) decreased significantly, but secondary sources increased dramatically. Industry, dust and vehicles contributed 36.6μgm(-3), 13.9μgm(-3), and 9.2μgm(-3) to the reduction of PM2.5, respectively., (Copyright © 2016 Elsevier B.V. All rights reserved.)

For the first time, ambient carbonyls were measured in a rural area in southern China from August 2012 to February 2013 to investigate their distribution characteristics and sources. Formaldehyde, acetaldehyde, and acetone were the three most abundant carbonyls, which accounted for 83-95 % of total seven carbonyls identified. The O3 formation potential of carbonyls in summer (59.55 μg/m(3)) was approximately ten times greater than that (6.37 μg/m(3)) in winter, and calculated photolysis rates were significantly faster in summer than those in winter, suggesting intensive photochemical activities in summer. Seasonal and diurnal variations of carbonyls showed that (1) the concentration of total carbonyls in summer (12.62 ± 10.83 μg/m(3)) was approximately five times greater than that in winter (2.33 ± 0.90 μg/m(3)), and a similar trend applied to the three abundant carbonyls; (2) the average summer to winter (S/W) ratio of formaldehyde and acetaldehyde was 10-13, and the S/W ratio of acetone was ~2.59; and (3) the highest concentrations of the three carbonyls and total carbonyls occurred at 14:00-16:00 with high temperature and intensive sunlight, especially in summer. These variations provided direct evidence for significant photochemical production of ambient carbonyls. Average C1/C2 ratios (3.07 ± 1.62) in summer were much greater than those (1.28 ± 0.25) in winter, and average C2/C3 ratios (35.09 ± 58.67) in summer were significantly greater than those (4.75 ± 2.12) in winter, both cases indirectly implying positive photochemical productions in summer. Especially, strong correlations (R(2) = 0.63-0.98) of temperature and sunlight intensity with the three abundant carbonyls and total carbonyls were observed, indicating a similar causal source such as significant photochemical production.

Size segragated samples were collected during high polluted winter haze days in 2006 in Beijing, China. Twenty nine elements and 9 water soluble ions were determined. Heavy metals of Zn, Pb, Mn, Cu, As, Cr, Ni, V and Cd were deeply studied considering their toxic effect on human being. Among these heavy metals, the levels of Mn, As and Cd exceeded the reference values of National Ambient Air Quality Standard (GB3095-2012) and guidelines of World Health Organization. By estimation, high percentage of atmospheric heavy metals in PM2.5 indicates it is an effective way to control atmospheric heavy metals by PM2.5 controlling. Pb, Cd, and Zn show mostly in accumulation mode, V, Mn and Cu exist mostly in both coarse and accumulation modes, and Ni and Cr exist in all of the three modes. Considering the health effect, the breakthrough rates of atmospheric heavy metals into pulmonary alveoli are: Pb (62.1%) > As (58.1%) > Cd (57.9%) > Zn (57.7%) > Cu (55.8%) > Ni (53.5%) > Cr (52.2%) > Mn (49.2%) > V (43.5%). Positive matrix factorization method was applied for source apportionment of studied heavy metals combined with some marker elements and ions such as K, As, SO4(2-) etc., and four factors (dust, vehicle, aged and transportation, unknown) are identified and the size distribution contribution of them to atmospheric heavy metals are discussed.

This study firstly focused on non-methane hydrocarbons (NMHCs) during three successive days with haze episode (16-18 August 2006) in Beijing. Concentrations of alkanes, alkenes, aromatic hydrocarbons, and ethyne all peaked at traffic rush hour, implying vehicular emission; and alkanes also peaked at non-traffic rush hour in the daytime, implying additional source. Especially, alkanes and aromatics clearly showed higher levels in the nighttime than that in the daytime, implying their active photochemical reactions in the daytime. Correlation coefficients (R (2)) showed that propane, n-butane, i-butane, ethene, propene, and benzene correlated with ethyne (R (2) = 0.61-0.66), suggesting that their main source is vehicular emission; 2-methylpentane and n-hexane correlated with i-pentane (R (2) = 0.61-0.64), suggesting that gasoline evaporation is their main source; and ethylbezene, m-/p-xylene, and o-xylene correlated with toluene (R (2) = 0.60-0.79), suggesting that their main source is similar to that of toluene (e.g., solvent usage). The R (2) of ethyne, i-pentane, and toluene with total NMHCs were 0.58, 0.76, and 0.60, respectively, indicating that ambient hydrocarbons are associated with vehicular emission, gasoline evaporation, and solvent usage. The sources of other hydrocarbons (e.g., ethane) might be natural gas leakage, biogenic emission, or long-range transport of air pollutants. Measured higher mean B/T ratio (0.78 ± 0.27) was caused by the more intensive photochemical activity of toluene than benzene, still indicating the dominant emission from vehicles.

A first study of nonmethane hydrocarbons (NMHCs) on hazy and normal days was performed in Foshan for providing deep insight into the local deteriorating air quality. Ethane, propane, i-pentane, ethene, propene, ethyne, benzene, and toluene were eight most abundant compounds, accounting for 71%-85% of total NMHCs. Most hydrocarbons showed much higher levels on hazy days than normal days together with hydrocarbon/ethyne ratios and diurnal variations, indicating hazy days are more dominated by vehicular emission. Correlation coefficients (R(2)) of ethane, propane, ethane, propene, benzene, and total NMHCs with ethyne were 0.62-0.83, indicating these compounds are mainly related to vehicular emission. R(2) analysis indicated that solvent usage is responsible for toluene and other aromatic hydrocarbons (e.g., ethylbezene). Benzene/toluene (B/T) ratio was 0.44±0.23 during whole sampling periods, again indicating vehicular emission is the dominant source. Lower B/T ratio (0.30±0.14) on hazy days than that (0.58±0.21) on normal days suggested that solvent usage emitted toluene.

Size distributions of 29 elements in aerosols collected at urban, rural and curbside sites in Beijing were studied. High levels of Mn, Ni, As, Cd and Pb indicate the pollution of toxic heavy metals cannot be neglected in Beijing. Principal component analysis (PCA) indicates 4 sources of combustion emission, crust related sources, traffic related sources and volatile species from coal combustion. The elements can be roughly divided into 3 groups by size distribution and enrichment factors method (EFs). Group 1 elements are crust related and mainly found within coarse mode including Al, Mg, Ca, Sc, Ti, Fe, Sr, Zr and Ba; Group 2 elements are fossil fuel related and mostly concentrated in accumulation mode including S, As, Se, Ag, Cd, Tl and Pb; Group 3 elements are multi-source related and show multi-mode distribution including Be, Na, K, Cr, Mn, Co, Ni, Cu, Zn, Ga, Mo, Sn and Sb. The EFs of Be, S, Cr, Co, Ni, Cu, Ga, Se, Mo, Ag, Cd, Sb, Tl and Pb show higher values in winter than in summer indicating sources of coal combustion for heating in winter. The abundance of Cu and Sb in coarse mode is about 2-6 times higher at curbside site than at urban site indicating their traffic sources. Coal burning may be the major source of Pb in Beijing since the phase out of leaded gasoline, as the EFs of Pb are comparable at both urban and curbside sites, and about two times higher in winter than that in summer.

Foshan is the most air-polluted city in Pearl River Delta. Non-methane hydrocarbons (NMHCs) were investigated for the first time in Foshan in winter 2008. Ethene, ethane, ethyne, propane, i-pentane, and toluene were the most abundant hydrocarbons and observed to be higher in Foshan than those in many other cities in China. Different from other cities, ethene and ethane were observed to be the two highest compounds in Foshan. Generally, the most abundant hydrocarbons showed high mixing ratios in the morning (0930-1030 hours), decreased to the lowest level in the afternoon (1430-1530 hours), and increased to higher value in the evening (1930-2030 hours). But i-pentane exhibited a different diurnal pattern with the highest level (13.4 ± 5.8 ppbv) in the afternoon, implying the acceleration of solvent evaporation resulting from higher temperature. Correlation coefficients (R(2) = 66% for n = 6 at 95% confidence level) of the individual hydrocarbons with ethyne and i-pentane indicated vehicular emissions were the main sources of ethene, propene, i-butene, isoprene, benzene and toluene, while gasoline evaporation was responsible for n-pentane, n-hexane, and n-heptane. The good correlation of most of the hydrocarbons with ethyne, indicating vehicular emissions, were the main sources of NMHCs. B/T ratio was 0.36 ± 0.06, implying vehicular emissions acted as the major contributors as well as additional emissions of toluene emitted from solvent usage. According to investigation, it also suggested that LPG leakage was the main source of propane, while NG leakage was responsible for ethane in Foshan City.

Diurnal air samples were collected from the E-waste dismantling region Guiyu and the underwear industry region Chendian. This was the first report to present the diurnal variation of PBDEs in the atmosphere. The average concentrations of 11 PBDE congeners were 11,742 pgm(-3) in the daytime, and 4830 pgm(-3) at night in Guiyu, while the concentrations were lower in Chendian with 376 pgm(-3) in the daytime, and 237 pgm(-3) at night. BDE-209 accounted for 22% and 31.3% of the total PBDEs in Guiyu and Chendian, respectively. The diurnal variation trends of BDE-47, -99, -153, -183, and -209 were also analyzed in detail in the two regions.

The chemical characteristics (water-soluble ions and carbonaceous species) of PM2.5 in Guangzhou were measured during a typical haze episode. Most of the chemical species in PM2.5 showed significant difference between normal and haze days. The highest contributors to PM2.5 were organic carbon (OC), nitrate, and sulfate in haze days and were OC, sulfate, and elemental carbon (EC) in normal days. The concentrations of secondary species such as, NO3(-), SO4(2-), and NH4(+) in haze days were 6.5, 3.9, and 5.3 times higher than those in normal days, respectively, while primary species (EC, Ca(2+), K(+)) show similar increase from normal to haze days by a factor about 2.2-2.4. OC/EC ratio ranged from 2.8 to 6.2 with an average of 4.7 and the estimation on a minimum OC/EC ratio showed that SOC (secondary organic carbon) accounted more than 36.6% for the total organic carbon in haze days. The significantly increase in the secondary species (SOC, NO3(-), SO4(2-), and NH4(+)), especially in NO3(-), caused the worst air quality in this region. Simultaneously, the result illustrated that the serious air pollution in haze episodes was strongly correlated with the meteorological conditions. During the sampling periods, air pollution and visibility had a good relationship with the air mass transport distance; the shorter air masses transport distance, the worse air quality and visibility in Guangzhou, indicating the strong domination of local sources contributing to haze formation. High concentration of the secondary aerosol in haze episodes was likely due to the higher oxidation rates of sulfur and nitrogen species.

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: 80-397 microg m(-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.