•Source contributions to PM2.5 across three sites in Wuhan were investigated.•OC varied greatly at these sites was due to large differences in local emission.•Regional source has much influence on these sites in winter.•A heavy haze event was caused by biomass burning via regional transport.•Mineral dust and industrial sources had the largest impact at industrial site.Fine particle (PM2.5) samples were collected in 2011 and 2012 simultaneously at three sites in Wuhan in an industrial area (ID), downtown Wuhan (DT), and the Wuhan botanical gardens (BG). The annual average concentration of PM2.5 was highest in the industrial area at 180 μg m− 3 and lowest in the botanical gardens, with an average of 93 μg m− 3. The average downtown PM2.5 concentration was 113 μg m− 3. All sites had concentrations well above the World Health Organization (WHO) guidelines and the Chinese air quality standard. The concentration of major constituents of PM2.5 varied seasonally across all sites; specifically, sulfate, nitrate, and organic carbon varied most strongly during spring, followed by summer and fall. Organic carbon varied the most across sites for all seasons, which is attributable to large differences in local source emissions. The major primary sources contributing to OC were vehicle emissions (38.1 ± 8.3%), coal combustion (7.0 ± 6.2%), meat cooking (3.0 ± 1.6%), and biomass burning (3.0 ± 1.0%). All these sources had large seasonal variations across the three sites. Biomass burning had the largest impact at BG, mobile sources had the largest impact at DT, and coal combustion had the largest impact at ID. Mineral dust was a major contributor to PM2.5 (average 16.8 ± 9.6 μg m− 3) and had very homogenous concentrations across the sites during springtime due to regional dust storms, but had much higher concentration at ID during the summer and fall. The results demonstrate the need for both regional and local air pollution control strategies to reduce air pollution in Wuhan. This research contributes to the field of particulate matter studies by providing information about seasonal and regional fluctuations in PM2.5 in large urban areas, which helps advance understanding of the sources responsible for urban haze.Download high-res image (236KB)Download full-size image

•Three LDHs with viable shapes and sizes were synthesized by hydrothermal method.•The ZnAl-LDH exhibit preferable regeneration capability for removal of Cr(VI).•Coexisting anions affect adsorption capacity of LDH due to competitive adsorption.Layered double hydroxide (LDH) materials comprising of Mg/Al, Ni/Al and Zn/Al with molar ratio (M2+/Al3+ = 3) were synthesized via a facile hydrothermal route. The microstructures, morphologies and textural properties of the LDH materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and N2 adsorption–desorption techniques. It was found that the three LDHs with different divalent metal cations were constructed from nanosheets with well-defined shapes and sizes. Adsorption rates and isotherms of the LDH adsorbents for Cr(VI) were investigated in batch experiments. Desorption behaviors and regeneration of Cr(VI)-adsorbed LDHs at the solid liquid interface were also studied. The ZnAl-LDH exhibited excellent sorption capacity (68.07 mg/g) for Cr(VI) and good regeneration performance. The effect of coexisting anions on the adsorption performance revealed that the anions (CO32−, HCO3−) greater impact on the adsorption process due to their larger laminate binding energy and closer affinity for hydrotalcite material.The LDHs exhibit different adsorption capacity of Cr(VI) by the influence of coexisting anions due to the competitive adsorption on surface and anions exchange relative preference. Because the carbonate anions (CO32−) have strong affinity for laminates of LDHs and small ion radius, they showed the greatest impact on the adsorption capacity and the degree of effect is in the sequence CO32− > HCO3− > SO42− > H2PO4− >Cl− > NO3−.