Template-free synthesis and characterization of K-phillipsite for use in potassium extraction from seawater

Kbphillipsite was prepared using a hydrothermal method. Soluble glass and sodium aluminate were used as raw materials in the absence of an organic template. Investigations regarding the K＋ ions were con- ducted at room temperature to determine the ion-exchange capacity in the seawater sample and the selectivity coefficient of the mixed K＋-Na~ solution. The sample was characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and energy dispersion spectroscopy （EDS）. The K＋ ion- exchange capacity is 51 mg/g in seawater and the selectivity coefficient is 75.1 in the mixed K＋-Na＋ solution. The sample has a selectivity preference for K＋, and therefore can be used to selectively extract potassium from seawater. The sample composed of Si, Al, K, Na, and O exhibits a cross-like shape and is a typical K-phillipsite structure.     

Self-assembly of fibrous ZSM-5 zeolites in the presence of sodium alginate

ZSM-5 zeolites with a fibrous morphology were successfully self-assembled in the presence of sodium alginate. The effect of the sodium alginate concentration, Si/Al molar ratio in the synthesis gel, crystallization temperature and time, and the addition order of the sodium alginate on the morphology of the ZSM-5 zeolites was investigated. The possible formation mechanism of fibrous ZSM-5 zeolite crystals was also proposed. The results indicated that the carboxyl and hydroxyl groups of sodium alginate synergistically induced the self-stacking of ZSM-5 nanocrystals and thus the formation of the fibrous ZSM-5 zeolites. The Si/Al molar ratio of the fibrous ZSM-5 zeolites could be adjusted by controlling the amount of the NaAlO₂ additive; however, high Si/Al molar ratios also hindered the self-stacking of ZSM-5 nanocrystals. A high crystallization temperature (180 °C), a moderate sodium alginate concentration (8.33 g/L), and the addition of sodium alginate prior to tetraethoxysilane were necessary for the formation of fibrous ZSM-5 zeolites.     

Emission of organic carbon,elemental carbon and water-soluble ions from crop straw burning under flaming and smoldering conditions

Emissions from major agricultural residues were measured using a self-designed combustion system. Emission factors (EFs) of organic carbon (OC), elemental carbon (EC), and water-soluble ions (WSIs) (K⁺, NH₄⁺, Na⁺, Mg²⁺, Ca²⁺, Cl⁻, NO₃⁻, SO₄^2–) in smoke from wheat and rice straw were measured under flaming and smoldering conditions. The OC₁/TC (total carbon) was highest (45.8% flaming, 57.7% smoldering) among carbon fractions. The mean EFs for OC (EF_OC) and EC (EF_EC) were 9.2 ± 3.9 and 2.2 ± 0.7 g/kg for wheat straw and 6.4 ± 1.9 and 1.1 ± 0.3 g/kg for rice straw under flaming conditions, while they were 40.8 ± 5.6 and 5.8 ± 1.0 g/kg and 37.6 ± 6.3 and 5.0 ± 1.4 g/kg under smoldering conditions, respectively. Higher EC ratios were observed in particulate matter (PM) mass under flaming conditions. The OC and EC for the two combustion patterns were significantly correlated (p < 0.01, R = 0.95 for wheat straw; p < 0.01, R = 0.97 for rice straw), and a higher positive correlation between OC₃ and EC was observed under both combustion conditions. WSIs emitted from flaming smoke were dominated by Cl⁻ and K⁺, which contributed 3.4% and 2.4% of the PM mass for rice straw and 2.2% and 1.0% for wheat straw, respectively. The EFs of Cl⁻ and K⁺ were 0.73 ± 0.16 and 0.51 ± 0.14 g/kg for wheat straw and 0.25 ± 0.15 and 0.12 ± 0.05 g/kg for rice straw under flaming conditions, while they were 0.42 ± 0.28 and 0.12 ± 0.06 g/kg and 0.30 ± 0.27 and 0.05 ± 0.03 g/kg under smoldering conditions, respectively. Na⁺, Mg²⁺, and NH₄⁺ were vital components in PM, comprising from 0.8% (smoldering) to 3.1% (flaming) of the mass. Strong correlations of Cl⁻ with K⁺, NH₄⁺, and Na⁺ ions were observed in rice straw and the calculated diagnostic ratios of OC/EC, K⁺/Na⁺ and Cl⁻/Na⁺ could be useful to distinguishing crop straw burning from other sources of atmospheric pollution.     

Influences of ions and temperature on performance of carbon nano-particulates in supercapacitors with neutral aqueous electrolytes

A commercial product of carbon nano-particles, Cabot MONACH 1300 pigment black (CMPB), was studied for basic structural information and electrochemical performance in neutral aqueous electrolytes, aiming at applications in supercapacitors. As confirmed by SEM and HRTEM, the CMPB had a hierarchical structure, containing basic 10 nm nano-spheres which combined into ca. 50 nm agglomerates which further aggregated into larger particles of micrometres. The capacitance of this commercial material was found to increase with decreasing the size of hydrous cation (Li⁺ → Na⁺ → K⁺), instead of the cation crystal radius (K⁺ → Na⁺ → Li⁺) when coupled with the same anion (Cl⁻). In electrolytes with the same cation concentration (K⁺), changing the anion from the larger dianion (SO₄²⁻) to the smaller monoanion (Cl⁻) also increased the capacitance at high potential scan rates (>50 mV/s). Increasing electrolyte concentration produced expected effect, including raising the electrode capacitance, but lowering the equivalent series resistance (ESR), charge transfer resistance (CTR), and the diffusion resistance. At higher temperatures, the CMPB exhibited slightly higher capacitance, which does not agree with the Gouy–Chapman theory on electric double layer (EDL). A hypothesis is proposed to account for the capacitance increase with temperature as a result of the CMPB opening up some micro-pores for more ions to access in response to the temperature increase.     

Experimental investigation on thermal properties of silver nanofluids

This paper reports on an experimental investigation of the thermal properties behavior of 0.5 wt% silver nanoparticle-based nanofluids (NF) containing oleic acid (OA) and potassium oleate surfactant (OAK⁺) with concentrations of 0.5, 1, and 1.5 wt% respectively. The experiments were conducted from 20 °C to 80 °C. It was shown that the NF with 1 wt% OAK⁺ yielded the highest thermal behavior enhancement of about 28% at 80 °C compared to deionized water. The thermal performance had higher than the base fluid/nanofluids at approximately 80%. Moreover, the NF containing OAK⁺ showed higher thermal conductivity and dynamics of specific heat capacity than deionized water in all of the experimental conditions in this study. The rheological experiment showed that viscosity of NF was significantly dependant on temperature. As shear rate increased, the shear stress of the NF increased; however, the viscosity of the nanofluids decreased first and then stabilized. It was further found that NF containing OAK⁺ at a range of operating temperatures produced Newtonian behavior.     

Unsteady gravity-driven slender rivulets of a power-law fluid

Unsteady gravity-driven flow of a thin slender rivulet of a non-Newtonian power-law fluid on a plane inclined at an angle α to the horizontal is considered. Unsteady similarity solutions are obtained for both converging sessile rivulets (when 0 < α < π/2) in the case x < 0 with t < 0, and diverging pendent rivulets (when π/2 < α < π) in the case x > 0 with t > 0, where x denotes a coordinate measured down the plane and t denotes time. Numerical and asymptotic methods are used to show that for each value of the power-law index N there are two physically realisable solutions, with cross-sectional profiles that are ‘single-humped’ and ‘double-humped’, respectively. Each solution predicts that at any time t the rivulet widens or narrows according to |x | ^{(2N+1)/2(N+1)} and thickens or thins according to |x | ^N/(N+1) as it flows down the plane; moreover, at any station x, it widens or narrows according to |t | ^?N/2(N+1) and thickens or thins according to |t | ^?N/(N+1). The length of a truncated rivulet of fixed volume is found to behave according to |t | ^N/(2N+1).     

Chemical characteristics of PM2.5 during dust storms and air pollution events in Chengdu,China

Daily fine particulate (PM_2.5) samples were collected in Chengdu from April 2009 to February 2010 to investigate their chemical profiles during dust storms (DSs) and several types of pollution events, including haze (HDs), biomass burning (BBs), and fireworks displays (FDs). The highest PM_2.5 mass concentrations were found during DSs (283.3 μg/m³), followed by FDs (212.7 μg/m³), HDs (187.3 μg/m³), and BBs (130.1 μg/m³). The concentrations of most elements were elevated during DSs and pollution events, except for BBs. Secondary inorganic ions (NO₃^?, SO₄^2?, and NH₄⁺) were enriched during HDs, while PM_2.5 from BBs showed high K⁺ but low SO₄^2?. FDs caused increases in K⁺ and enrichment in SO₄^2?. Ca²⁺ was abundant in DS samples. Ion-balance calculations indicated that PM_2.5 from HDs and FDs was more acidic than on normal days, but DS and BB particles were alkaline. The highest organic carbon (OC) concentration was 26.1 μg/m³ during FDs, followed by BBs (23.6 μg/m³), HDs (19.6 μg/m³), and DSs (18.8 μg/m³). In contrast, elemental carbon (EC) concentration was more abundant during HDs (10.6 μg/m³) and FDs (9.5 μg/m³) than during BBs (6.2 μg/m³) and DSs (6.0 μg/m³). The highest OC/EC ratios were obtained during BBs, with the lowest during HDs. SO₄^2?/K⁺ and TCA/SO₄^2? ratios proved to be effective indicators for differentiating pollution events. Mass balance showed that organic matter, SO₄^2?, and NO₃^? were the dominant chemical components during pollution events, while soil dust was dominant during DSs.     

Drag reduction for liquid flow through micro-apertures

Pressure drops in the flow through micro-orifices and capillaries were measured for silicone oils, aqueous solutions of polyethylene glycol (PEG), and surfactant aqueous solutions. The diameter of micro-orifices ranged from 5 μm to 400 μm. The corresponding length/diameter ratio was from 4 to 0.05 and capillary diameters were 105 μm and 450 μm. The following results were obtained: silicone oils of 10^?6 m²/s and 10^?5 m²/s in kinematic viscosity generated a reduction of pressure drop (RPD), that is, drag reduction, similar to the RPD of water and a glycerol/water mixture reported in the previous paper by the present authors. When RPD occurred, the pressure drop (PD) of silicone oils of 10^?6 m²/s and 10^?5 m²/s had nearly the same magnitude. Namely, the difference in viscosity did not influence RPD. A 10³ ppm aqueous solution of PEG20000 provided almost the same PD as that of PEG8000 for the 400 μm to 15 μm orifices, but a greater PD than that of PEG8000 for the 10 μm to 5 μm orifices. A non-ionic surfactant and a cationic surfactant were highly effective in RPD compared with anionic surfactants: the non-ionic and cationic surfactant solutions had PD one order of magnitude lower than that of water under some flow conditions in the concentration range from 1 ppm to 10⁴ ppm, but the anionic surfactant solutions did not generate RPD except in the case of the smallest orifice of 5 μm in diameter. The PD of the non-ionic surfactant solution showed a steep rise at a Reynolds number (Re_t) for 400 μm to 15 μm orifices. The Re_t provides the relationship Re_t = K/D, where D is the orifice diameter, and K is a constant of 2 × 10^?2 m for the 100–20 μm orifices irrespective of liquid concentration. Capillary flow experiment revealed that the PEG, non-ionic and cationic surfactant solutions generated RPD also in a laminar flow through the capillary of 105 μm in diameter, but not in the flow through the capillary of 450 μm in diameter. In order to clarify the cause of RPD, an additional experiment was carried out by changing the orifice material from metal to acrylic resin. The result gave a different appearance of RPD, suggesting that RPD is related to an interfacial phenomenon between the liquid and wall. The large RPDs found in the present experiment are very interesting from both academic and practical viewpoints.     

Phase evolution of （K,Na）NbO3 powder prepared by high temperature mixing under hydrothermal conditions

（Na, K）NbO3 （KNN） powders were successfully prepared by high temperature mixing method （HTMM） under hydrothermal conditions to study the effect of reaction time on the formation of KNN for three K＋/（K＋ ＋Na＋） ratios of 0.6, 0.7 and 0.8. The products were characterized by X-ray diffraction （XRD）, scanning electron microscope （SEM）, transmission electron microscopy （TEM） and selected area electron diffraction （SAED）, to show the change of phase and morphology of the as-prepared particles with the K＋/（K＋ ＋ Na＋） molar ratio in the solution. Pure Na-rich KNN monoclinic phase and pure K-rich KNN orthorhombic phase could be obtained quickly after mixing the solutions at high temperature when the K＋/（K＋ ＋Na＋） molar ratio was either 0.6 or 0.8. When the K＋/（K＋ ＋Na＋） molar ratio was 0.7, however, the K-rich KNN orthorhombic phase grain formed first, followed by the Na-rich KNN monoclinic phase grain, with the two phases coexisting in the final product.     

Argon K-shell and bound-free emission from OMEGA direct-drive implosion cores

We discuss calculations of synthetic spectra for the interpretation and analysis of K-shell and bound-free emission from argon-doped deuterium-filled OMEGA direct-drive implosion cores. The spectra are computed using a model that considers collisional-radiative atomic kinetics, continuum-lowering, detailed Stark-broadened line shapes, line overlapping, and radiation transport effects. The photon energy range covers the moderately optically thick n = 3 → n = 1 and n = 4 → n = 1 line transitions in He- and H-like Ar, their associated satellite lines in Li- and He-like Ar, and several radiative recombination edges. At the high-densities characteristic of implosion cores, the radiative recombination edges substantially shift to lower energies thus overlapping with several line transitions. We discuss the application of the spectra to spectroscopic analysis of doped implosion cores.     

Observation and analysis of near-surface atmospheric aerosol optical properties in urban Beijing

Year-round measurements of the mass concentration and optical properties of fine aerosols (PM_2.5) from June 2009 to May 2010 at an urban site in Beijing were analyzed. The annual mean values of the PM_2.5 mass concentration, absorption coefficient (Ab), scattering coefficient (Sc) and single scattering albedo (SSA) at 525 nm were 67 ± 66 μg/m³, 64 ± 62 Mm⁻¹, 360 ± 405 Mm⁻¹ and 0.82 ± 0.09, respectively. The bulk mass absorption efficiency and scattering efficiency of the PM_2.5 at 525 nm were 0.78 m²/g and 5.55 m²/g, respectively. The Ab and Sc showed a similar diurnal variation with a maximum at night and a minimum in the afternoon, whereas SSA displayed an opposite diurnal pattern. Significant increases in the Ab and Sc were observed in pollution episodes caused by the accumulation of pollutants from both local and regional sources under unfavorable weather conditions. Aerosol loadings in dust events increased by several times in the spring, which had limited effects on the Ab and Sc due to the low absorption and scattering efficiency of dust particles. The frequency of haze days was the highest in autumn because of the high aerosol absorption and scattering under unfavorable weather conditions. The daily PM_2.5 concentration should be controlled to a level lower than 64 μg/m³ to prevent the occurrence of haze days according to its exponentially decreased relationship with visibility.     

Solid-state synthesis of Li[Li0.2Mn0.56Ni0.16Co0.08]O2 cathode materials for lithium-ion batteries

Layered Li[Li_0.2Mn_0.56Ni_0.16Co_0.08]O₂ cathode materials were synthesized via a solid-state reaction for Li-ion batteries, in which lithium hydroxide monohydrate, manganese dioxide, nickel monoxide, and cobalt monoxide were employed as metal precursors. To uncover the relationship between the structure and electrochemical properties of the materials, synthesis conditions such as calcination temperature and time as well as quenching methods were investigated. For the synthesized Li[Li_0.2Mn_0.56Ni_0.16Co_0.08]O₂ materials, the metal components were found to be in the form of Mn⁴⁺, Ni²⁺, and Co³⁺, and their molar ratio was in good agreement with stoichiometric ratio of 0.56:0.16:0.08. Among them, the one synthesized at 800 °C for 12 h and subsequently quenched in air showed the best electrochemical performances, which had an initial discharge specific capacity and coulombic efficiency of 265.6 mAh/g and 84.0%, respectively, and when cycled at 0.5, 1, and 2 C, the corresponding discharge specific capacities were 237.3, 212.6, and 178.6 mAh/g, respectively. After recovered to 0.1 C rate, the discharge specific capacity became 259.5 mAh/g and the capacity loss was only 2.3% of the initial value at 0.1 C. This work suggests that the solid-state synthesis route is easy for preparing high performance Li[Li_0.2Mn_0.56Ni_0.16Co_0.08]O₂ cathode materials for Li-ion batteries.     

Synthesis of potassium sodium niobate powders using an EDTA/citrate complexing sol–gel method

Potassium sodium niobate (KNN) powders were synthesized by a modified sol–gel method, using as starting chemicals potassium carbonate, sodium carbonate, and niobium hydroxide, and, as esterification and chelating agents, respectively, ethylene glycol (EG) and ethylene diamine tetraacetic acid (EDTA)/citrate. The effects of citric acid (CA), EG, and EDTA on the stability of the precursor sol were systemically investigated. The powders and gels were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis-differential scanning calorimetry (TGA-DSC). The results indicated that a stable precursor sol was formed when n(CA):n(Mⁿ⁺) = 3:1, n(EDTA):n(NH₄OH) = 1:3.5, and n(CA):n(EG) = 1:2. The xerogel was calcined at 500–950 °C to prepare the KNN powder. Pure KNN perovskite phase with a cube-like structure was synthesized at 850 °C from the precursor sol for a K/Na molar ratio of 1.2. The formation mechanism of the KNN perovskite phase was also discussed.     

Experimental quantification of the plastic blunting process for stage II fatigue crack growth in one-phase metallic materials

The plastic blunting process during stage II fatigue crack growth was studied in pure polycrystalline Ni to investigate effects of strain localization and inelastic behavior on the kinematics of crack advance. Correlations were obtained between strain fields ahead of a fatigue crack, crack advance per cycle and crack growth kinetics. Strain fields were quantified using a combination of in situ loading experiments, scanning electron microscopy and digital image correlation for 8 < ΔK < 20 MPa m^1/2 and a fixed load ratio of 0.1. Results indicate that strain localized along a dominant deformation band, which was usually crystallographic and carried mostly pure shear for large loads and was of mixed character for lower loads. Instances of double deformation bands were observed, with bands acting either in a simultaneous or alternating fashion. It was found that the area integral of the opening strain for values larger than a given threshold, an “integrated” strain, had a power-law relationship with ΔK, with the exponent approximately equal to the Paris exponent (m). Therefore, the crack growth rate was proportional to the integrated strain. An analysis based on this correlation and the presence of dominant shear bands indicated that the integrated strain is related to the accumulated displacement in the band. This, in turn, is proportional to the product of the cyclic plastic zone radius and the average shear strain ahead of the tip, which represents a basic length scale for plastic blunting. Assumptions on the load dependence of these quantities, based on their observed spatial variation, allowed estimating $m=2\left(1+\frac{1}{1+n^{\prime }}\right)$, where n′ is the cyclic hardening exponent (0 < n′ < 1). This gives 3 < m < 4, which accounts for about 50% of the observed values of m between 1.5 and 6 for a wide variety of metallic materials.     

Analytical modeling of synthetic fiber ropes subjected to axial loads. Part I: A new continuum model for multilayered fibrous structures

Synthetic fiber ropes are characterized by a very complex architecture and a hierarchical structure. Considering the fiber rope architecture, to pass from fiber to rope structure behavior, two scale transition models are necessary, used in sequence: one is devoted to an assembly of a large number of twisted components (multilayered), whereas the second is suitable for a structure with a central straight core and six helical wires (1 + 6). The part I of this paper first describes the development of a model for the static behavior of a fibrous structure with a large number of twisted components. Tests were then performed on two different structures subjected to axial loads. Using the model presented here the axial stiffness of the structures has been predicted and good agreement with measured values is obtained. A companion paper (Ghoreishi, S.R. et al., in press. Analytical modeling of synthetic fiber ropes, part II: A linear elastic model for 1 + 6 fibrous structures, International Journal of Solids and Structures, doi:10.1016/j.ijsolstr.2006.08.032) presents the second model to predict the mechanical behavior of a 1 + 6 fibrous structure.     

Hydrothermal synthesis of ultrathin hexagonal nickel hydroxide nanosheets

Nickel hydroxide, Ni(OH)₂ is widely used in electrodes of nickel-based alkaline secondary batteries. Ultrathin hexagonal Ni(OH)₂ nanosheets of space group P-3m1 were hydrothermally prepared at 200 °C for 10 h. Their diameter and thickness were 200–300 and 3–5 nm, respectively. Their formation was attributed to the oriented assembly of growing particles, which was assisted by surfactant molecules. The specific surface area of the Ni(OH)₂ nanosheets was 8.66 m²/g. Their magnetization curve exhibited linear paramagnetic behavior across the entire measurement region.     

Measurements of emission spectra from hot,dense germanium plasma in short pulse laser experiments

Heating of thin foil targets by an high power laser at intensities of 10¹⁷–10¹⁹ W/cm² has been studied as a method for producing high temperature, high density samples to investigate X-ray opacity and equation of state. The targets were plastic (parylene-N) foils with a microdot made of a mixture of germanium and titanium buried at depth of 1.5 μm. The L-shell spectra from the germanium and the K-shell spectra from the titanium were taken using crystal spectrometers recording onto film and an ultra fast X-ray streak camera coupled to a conical focussing crystal with a time resolution of 1 ps. The conditions in the microdot were inferred by comparing the measured spectra to synthetic spectra produced by the time-dependent collisional–radiative (CR) models FLY and FLYCHK. The data were also compared to simulated spectra from a number of opacity codes assuming local thermodynamic equilibrium (LTE). Temperature and density gradients were taken into account in the comparisons. The sample conditions were inferred from the CR modelling using FLYCHK to be 800 ± 100 eV and 1.5 ± 0.5 g/cc. The best fit to the LTE models was at a temperature 20% lower than with the CR model. Though the sample departs from LTE significantly useful spectral comparisons can still be made. The results and comparisons are discussed along with improvements to the experimental technique to achieve conditions closer to LTE.     

Effect of travel speed and vertical load on the subsoil force and displacement under a smooth steel roller

A smooth steel roller was tested in an indoor soil bin. Subsoil forces and displacements were measured at depths of 50, 100, 150, and 200 mm. Roller operating conditions included roller travel speed, the vertical load, and number of passes. Three travel speeds, 1, 3, and 5 km h^?1 and three vertical loads 20, 40, and 60 kN were tested. The draft needed to move the roller was also recorded. For multiple passes, subsoil forces were increased by 30% if vertical load increased by 50%; while the roller draft increased by 20%. For a single pass, no significant differences detected between the subsoil forces at speeds of 1 and 3 km h^?1; when the roller traveled at 5 km h^?1 with a vertical load of 60 kN, the subsoil force was approximately reduced by 30% compared to those at lower travel speeds. For both single and multiple passes, increasing travel speed did not significantly increase subsoil forces and displacement below 150-mm depth; however, the power required to drive the roller was significantly increased. Higher travel speed was more effective in creating larger subsoil displacement and subsoil forces within 100-mm from the soil surface. For similar effects below 100-mm, lower travel speed was found appropriate.     

Preparation and Li+ storage properties of hierarchical hollow porous carbon spheres

Hollow ordered porous carbon spheres (HOPCS) with a hierarchical structure were prepared by templating with hollow ordered mesoporous silica spheres (HOMSS). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that HOPCS exhibited a spherical hollow morphology. High-resolution TEM, small angle X-ray diffraction (SAXRD) and N₂ sorption measurements confirmed that HOPCS inversely replicated the unconnected hexagonal-stacked pore structure of HOMSS, and possessed ordered porosity. HOPCS exhibited a higher storage capacity for Li⁺ ion battery (LIB) of 527.6 mA h/g, and good cycling performance. A large capacity loss during the first discharge–charge cycle was found attributed to the high content of micropores. The cycling performance was derived from the hierarchical structure.     

Chemical characteristics of PM2.5 during haze episodes in the urban of Fuzhou,China

Atmospheric fine particles (PM_2.5) were collected in this study with middle volume samplers in Fuzhou, China, during both normal days and haze days in summer (September 2007) and winter (January 2008). The concentrations, distributions, and sources of polycyclic aromatic hydrocarbons (PAHs), organic carbon (OC), elemental carbon (EC), and water soluble inorganic ions (WSIIs) were determinated. The results showed that the concentrations of PM_2.5, PAHs, OC, EC, and WSIIs were in the orders of haze > normal and winter > summer. The dominant PAHs of PM_2.5 in Fuzhou were Fluo, Pyr, Chr, BbF, BkF, BaP, BghiP, and IcdP, which represented about 80.0% of the total PAHs during different sampling periods. The BaPeq concentrations of ∑PAHs were 0.78, 0.99, 1.22, and 2.43 ng/m³ in summer normal, summer haze, winter normal, and winter haze, respectively. Secondary pollutants (SO₄^2?, NO₃^?, NH₄⁺, and OC) were the major chemical compositions of PM_2.5, accounting for 69.0%, 55.1%, 63.4%, and 64.9% of PM_2.5 mass in summer normal, summer haze, winter normal, and winter haze, respectively. Correspondingly, secondary organic carbon (SOC) in Fuzhou accounted for 20.1%, 48.6%, 24.5%, and 50.5% of OC. The average values of nitrogen oxidation ratio (NOR) and sulfur oxidation ratio (SOR) were higher in haze days (0.08 and 0.27) than in normal days (0.05 and 0.22). Higher OC/EC ratios were also found in haze days (5.0) than in normal days (3.3). Correlation analysis demonstrated that visibility had positive correlations with wind speed, and negative correlations with relative humidity and major air pollutants. Overall, the enrichments of PM_2.5, OC, EC, SO₄^2?, and NO₃^? promoted haze formation. Furthermore, the diagnostic ratios of IcdP/(IcdP + BghiP), IcdP/BghiP, OC/EC, and NO₃^?/SO₄^2? indicated that vehicle exhaust and coal consumption were the main sources of pollutants in Fuzhou.