Synthesis and enhanced visible-light responsive of C,N,S-tridoped TiO2 hollow spheres

C,N,S-tridoped TiO2 hollow spheres （labeled as C,N,S-THs） were synthesized using carbon spheres as template and C,N,S-tridoped TiO2 nanoparticles as building blocks. The structure and physicochemical properties of the catalysts were characterized by X- ray diffraction （XRD）, scanning electron microscopy （SEM）, UV-Vis diffuse reflectance spectrum （DRS）, N2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy （XPS） and Photoluminescence emission spectroscopy （PL）. The results showed that the hollow spheres had average diameter of about 200 nm and the shell thickness was about 20 nm. The tridoped TiO2 hollow spheres exhibited strong absorption in the visible-light region. C,N,S-tridoped could narrow the band gap of the THs by mixing the orbit O 2p with C 2p, N 2p and S 3p orbits and shift its optical response from ultraviolet （UV） to the visible-light region. PL analysis indicated that the electron-hole recombination rate of TiO2 hollow spheres had been effectively inhibited when doped with C, N and S elements. The photocatalytic activities of the samples were evaluated for the degradation of X-3B （Reactive Brilliant Red dye, C.I. Reactive Red 2） aqueous solution under visible-light （λ 〉 420 nm） irradiation. It was found that the C,N,S-tridoped TiO2 hollow spheres indicated higher photocatalytic activity than commercial P25 and the undoped counterpart photocatalyst.     

Investigation of potential interferences on the measurement of dissolved reactive phosphate using zirconium oxide-based DGT technique

A diffusive gradients in thin films (DGT) technique based on hydrous zirconium oxide (Zr-oxide) has been recently developed for the measurement of dissolved reactive phosphate (DRP). In this study, the detailed performance of the DGT technique is reported. Spiking experiments revealed that several orthophosphate monoester compounds contributed to the Zr-oxide DGT measurements of DRP. However, such a phenomenon is unlikely to occur during field conditions due to the low concentration of organic P in typical natural waters. The presence of Cl- (up to 106 g/L), SO42- (up to 16 g/L), HCO3- (up to 817 g/L), and AsO2- and AsO 3 4 (both up to 1 mg As/L) in solutions had negligible effects on the measurement of DRP. The threshold concentrations of Cl-, SO42- and HCO3- have been increased from previous reports for the measurements of DRP using other adsorbent-based DGT techniques. The capacity for DGT measurements of DRP decreased with increasing solution pH (4.2-9.2). The lowest capacity (95 μg P/m2 at pH 9.2) was still greater than that of other DGT techniques that are usually used for the measurement of DRP (2-12 μg P/cm2 ). The Zr-oxide binding gel could be stored for up to 2 years without any aging effect. This period of validity was considerably longer than the ferrihydrite binding gel that is commonly used in present DGT devices (6 months). The field application revealed that the concentrations of DRP measured in three fresh water samples using the Zr-oxide DGT technique were in agreement with those of the traditional colorimetric method.     

PM2．5的污染特征及综合防治分析

大气污染严重,空气中尤以PM2.5对人健康损害最大。本文对PM2.5的来源、污染表征、国内外控制标准及综合防治措施作了基本概述,以期对读者有参考。     

稻田表面流去除鱼塘养殖水中的氮、磷效果试验研究

池塘水质对水产养殖非常重要,本研究的目的在于探索稻田面流净化池塘养殖水质的技术途径。在养殖池塘旁稻田内布置9个小区,进行田间面流试验,取水样进行分析。结果表明：在1．5—6．0m^3／h（相应的平均流速为7．5～30m／h）的水力负荷下,鱼池水经稻田表面流处理后可得到一定净化;N、P的去除率与稻田表面流的流量（流速）有关,随流量增大呈减小趋势;在抽穗一扬花期稻田可有效减少养殖水的氮磷含量,在拔节期一孕穗期可显著减少NOf—N含量,有利改善池塘养殖环境。     

贵州省雷暴日数的时空分布、周期及突变特征

利用1961—2011年贵州省87个台站地面雷暴观测资料,对该省境内雷暴日数的时空分布、周期和突变特征进行了分析。结果表明：贵州省雷暴日数年际变化较大,下降趋势显著;雷暴日数的时空分布形态不对称,92．16％正偏,峰度76．47％为正值,48a贵州区域内空间分布在0．05置信水平上服从正态分布。雷暴日数分布地域特征明显,从贵州西南部向东北方向呈梯状递减趋势,安顺市、六盘水市和黔西南州3个地区为雷暴高发区。贵州省逐年雷暴日数存在不太明显的18a左右的长周期以及4—5a和8—9a显著的周期变化。贵州省年雷暴日数的下降是一突变现象,具体是从1995年开始的,突变前后平均雷暴日数相差9．32d。     

Synergetic PM2.5 and O3 control strategy for the Yangtze River Delta, China

PM_2.5 concentrations have dramatically reduced in key regions of China during the period 2013–2017, while O₃ has increased. Hence there is an urgent demand to develop a synergetic regional PM_2.5 and O₃ control strategy. This study develops an emission-to-concentration response surface model and proposes a synergetic pathway for PM_2.5 and O₃ control in the Yangtze River Delta (YRD) based on the framework of the Air Benefit and Cost and Attainment Assessment System (ABaCAS). Results suggest that the regional emissions of NOx, SO₂, NH₃, VOCs (volatile organic compounds) and primary PM_2.5 should be reduced by 18%, 23%, 14%, 17% and 33% compared with 2017 to achieve 25% and 5% decreases of PM_2.5 and O₃ in 2025, and that the emission reduction ratios will need to be 50%, 26%, 28%, 28% and 55% to attain the National Ambient Air Quality Standard. To effectively reduce the O₃ pollution in the central and eastern YRD, VOCs controls need to be strengthened to reduce O₃ by 5%, and then NOx reduction should be accelerated for air quality attainment. Meanwhile, control of primary PM_2.5 emissions shall be prioritized to address the severe PM_2.5 pollution in the northern YRD. For most cities in the YRD, the VOCs emission reduction ratio should be higher than that for NOx in Spring and Autumn. NOx control should be increased in summer rather than winter when a strong VOC-limited regime occurs. Besides, regarding the emission control of industrial processes, on-road vehicle and residential sources shall be prioritized and the joint control area should be enlarged to include Shandong, Jiangxi and Hubei Province for effective O₃ control.     

Kinetics of nitrobenzene degradation coupled to indigenous microorganism dissimilatory iron reduction stimulated by emulsified vegetable oil

Widespread contamination by nitrobenzene(NB) in sediments and groundwater requires better understanding of the biogeochemical removal process of the pollutant. NB degradation, coupled with dissimilatory iron reduction, is one of the most efficient pollutant removal methods. However, research on NB degradation coupled to indigenous microorganism dissimilatory iron reduction stimulated by electron donors is still experimental. A model for remediation in an actual polluted site does not currently exist.Therefore, in this study, the dynamics was derived from the Michaelis–Menten model(when the mass ratio of emulsified vegetable oil and NB reached the critical value 91:1). The effect of SO_4~(2-), NO_3~-, Ca~(2+)/Mg~(2+), and the grain size of aquifer media on the dynamics were studied, and the NB degradation dynamic model was then modified based on the most significant factors. Utilizing the model, the remediation time could be calculated in a contaminated site.     

Removal of Cs from water and soil by ammonium-pillared montmorillonite/Fe3O4 composite

To remove cesium ions from water and soil, a novel adsorbent was synthesized by following a one-step co-precipitation method and using non-toxic raw materials. By combining ammonium-pillared montmorillonite (MMT) and magnetic nanoparticles (Fe₃O₄), an MMT/Fe₃O₄ composite was prepared and characterized. The adsorbent exhibited high selectivity of Cs⁺ and could be rapidly separated from the mixed solution under an external magnetic field. Above all, the adsorbent had high removal efficiency in cesium-contaminated samples (water and soil) and also showed good recycling performance, indicating that the MMT/Fe₃O₄ composite could be widely applied to the remediation of cesium-contaminated environments. It was observed that the pH, solid/liquid ratio and initial concentration affected adsorption capacity. In the presence of coexisting ions, the adsorption capacity decreased in the order of Ca^2 + > Mg^2 + > K⁺ > Na⁺, which is consistent with our theoretical prediction. The adsorption behavior of this new adsorbent could be expressed by the pseudo-second-order model and Freundlich isotherm. In addition, the adsorption mechanism of Cs⁺ was NH₄⁺ ion exchange and surface hydroxyl group coordination, with the former being more predominant.     

Highly efficient Zr doped-TiO2/glass fiber photocatalyst and its performance in formaldehyde removal under visible light

Zr-doped-TiO_2 loaded glass fiber(ZT/GF) composite photocatalysts with different Zr/Ti ratios were prepared with a sol–gel process. Zr4+can replace Ti4+in the TiO_2 lattice, which is conducive to forming the anatase phase and reducing the calcination temperature. The glass fiber carrier was responsible for better dispersion and loading of Zr-doped-TiO_2 particles, improving the applicability of the Zr-doped-TiO_2. The ZT/GF photocatalysts were characterized by X-ray diffraction(XRD), scanning electron microscope(SEM), Fourier transform infrared spectroscopy(FT-IR), ultraviolet–visible spectroscopy(UV–vis) and Barrett–Joyner–Halenda(BJH). The performance of photocatalysts with different loading was evaluated in formaldehyde degradation under visible light at room temperature. ZT/GF0.2exhibited the highest activity, with a formaldehyde removal rate as high as 95.14% being observed, which is better than that of the photocatalyst particles alone. The stability of the catalyst was also tested, and ZT/GF exhibited excellent catalytic performance with 94.38%removal efficiency, even after seven uses.     

Implications for emergency response to the severe odor incident occurred in source water: Potential odorants and control strategy

Environmental Science and Pollution Research - Sudden odor incidents occurring in the source water have been a severe problem for water suppliers. In order to apply emergency control measures...