Characteristics of secondary inorganic aerosol and sulfate species in size-fractionated aerosol particles in Shanghai

Sulfate, nitrate and ammonium(SNA) are the dominant species in secondary inorganic aerosol, and are considered an important factor in regional haze formation. Size-fractionated aerosol particles for a whole year were collected to study the size distribution of SNA as well as their chemical species in Shanghai. SNA mainly accumulated in fine particles and the highest average ratio of SNA to particulate matter(PM) was observed to be 47% in the fine size fraction(0.49–0.95 μm). Higher sulfur oxidation ratio and nitrogen oxidation ratio values were observed in PM of fine size less than 0.95 μm. Ion balance calculations indicated that more secondary sulfate and nitrate would be generated in PM of fine size(0.49–0.95 μm). Sulfur K-edge X-ray absorption near-edge structure(XANES) spectra of typical samples were analyzed. Results revealed that sulfur mainly existed as sulfate with a proportion(atomic basis) more than 73% in all size of PM and even higher at 90% in fine particles. Sulfate mainly existed as(NH4)2SO4 and gypsum in PM of Shanghai. Compared to non-haze days, a dramatic increase of(NH4)2SO4 content was found in fine particles on haze days only, which suggested the promoting impact of(NH4)2SO4 on haze formation. According to the result of air mass backward trajectory analysis, more(NH4)2SO4 would be generated during the periods of air mass stagnation. Based on XANES, analysis of sulfate species in size-fractionated aerosol particles can be an effective way to evaluate the impact of sulfate aerosols on regional haze formation.     

Understanding nutrient build-up on urban road surfaces

This article discusses the outcomes of a research project on nutrients build-up on urban road surfaces.Nutrient build-up was investigated on road sites belonging to residential,industrial and commercial land use.Collected build-up samples were separated into five particle size ranges and were tested for total nitrogen (TN),total phosphorus (TP) and sub species of nutrients,namely,NO 2- ,NO 3- ,TKN and PO 43-.Multivariate analytical techniques were used to analyse the data and to develop detailed understanding on build- up.Data analysis revealed that the solids loads on urban road surfaces are highly influenced by factors such as land use,antecedent dry period and traffic volume.However,the nutrient build-up process was found to be independent of the type of land use.It was solely dependent on the particle size of solids build-up.Most of the nutrients were associated with the particle size range 150 μm.Therefore,the removal of particles below 150 μm from road surfaces is of importance for the removal of nitrogen and phosphorus from road surface solids build-up.It is also important to consider the difference in the composition of nitrogen and phosphorus build-up in the context of designing effective stormwater quality mitigation strategies.     

Effects of physical and chemical characteristics of surface sediments in the formation of shallow lake algae-induced black bloom

Surface sediments are closely related to lake black blooms. The dissolved oxygen （DO） distribution and its penetration depth in surface sediments as well as the migration and transformation of redox sensitive elements such as Fe and S at the sediment-water interface are important factors that could influence the formation of the black bloom. In this study, dredged and undredged sediment cores with different surface properties were used to simulate black blooms in the laboratory. The Micro Profiling System was employed to explore features of the DO and ∑H2S distribution at the sediment-water interface. Physical and chemical characteristics in sediments and pore waters were also analyzed. The results showed that sediment dredging effectively suppressed the black blooms. In the undredged treatment, DO penetration depth was only 50 μm. Fe^2＋ concentrations, ∑H2S concentrations, and ∑H2S production rates were remarkably higher in surface sediments and pore waters compared to control and dredged treatments. Furthermore, depletion of DO and accumulation of Fe^2＋ and ∑H2S in surface sediments and pore waters provided favorable redox environments and necessary material sources for the blooms. The study results proved that physical and chemical characteristics in surface sediments are important factors in the formation of the black bloom, and could provide scientific guidance for emergency treatment and long-term pre-control of black blooms.     

酸沉降对非金属建筑材料腐蚀机理的探讨

将酸雨对非金属建筑材料的整个腐蚀过程分为腐蚀初期、中期和末期3个腐蚀阶段,进而提出腐蚀机理。对整个腐蚀过程探讨表明:酸雨对材料的腐蚀是酸雨中H+和SO2₄-共同侵蚀作用的结果;H+将溶解硬化水泥石中的Ca(OH)₂,SO2₄-将与硬化水泥石作用生成膨胀性的物质CaSO₄·2H₂O。因此,酸雨对非金属建筑材料的腐蚀,主要是H+引起溶解腐蚀和SO2₄-引起的膨胀腐蚀。      

Effects of O3/Cl2 disinfection on corrosion and opportunistic pathogens growth in drinking water distribution systems

The effects of O_3/Cl_2 disinfection on corrosion and the growth of opportunistic pathogens in drinking water distribution systems were studied using annular reactors(ARs).The corrosion process and most probable number(MPN) analysis indicated that the higher content of iron-oxidizing bacteria and iron-reducing bacteria in biofilms of the AR treated with O_3/Cl_2 induced higher Fe_3O_4 formation in corrosion scales.These corrosion scales became more stable than the ones that formed in the AR treated with Cl_2 alone.O_3/Cl_2 disinfection inhibited corrosion and iron release efficiently by changing the content of corrosion-related bacteria.Moreover,ozone disinfection inactivated or damaged the opportunistic pathogens due to its strong oxidizing properties.The damaged bacteria resulting from initial ozone treatment were inactivated by the subsequent chlorine disinfection.Compared with the AR treated with Cl_2 alone,the opportunistic pathogens M.avium and L.pneumophila were not detectable in effluents of the AR treated with O_3/Cl_2,and decreased to(4.60 ± 0.14) and(3.09 ± 0.12) log10(gene copies/g corrosion scales) in biofilms,respectively.The amoeba counts were also lower in the AR treated with O_3/Cl_2.Therefore,O_3/C_l2 disinfection can effectively control opportunistic pathogens in effluents and biofilms of an AR used as a model for a drinking water distribution system.     

Experimental Evaluation of Cutter Orientation When Ball Nose End Milling Inconel 718™

High-speed machining (HSM), specifically end milling and ball end cutting, is attracting interest in the aerospace industry for the machining of complex 3D aerofoil surfaces in titanium alloys and nickel-based superalloys. Following a brief introduction on HSM and related aerospace work, the paper reviews published data on the effect of cutter/workpiece orientation, also known as engagement or tilt angle, on tool performance. Such angles are defined as ±β_fN and ±β_f.Experimental work is detailed on the effect of cutter orientation on tool life, cutting forces, chip formation, specific force, and workpiece surface roughness when high-speed ball end milling Inconel 718™. Dry cutting was performed using 8 mm diameter PVD-coated solid carbide cutters with the workpiece mounted at an angle of 45° from the cutter axis.A horizontal downward (-β_fN) cutting orientation provided the best tool life with cut lengths ∼50% longer than for all other directions (+β_fN, +β_f, and –β_f). Evaluation of cutting forces and associated spectrum analysis of results indicated that cutters employed in a horizontal downward direction produced the least vibration. This contributed to improved workpiece surface roughness, with typical mean values of ∼0.4 μm Ra as opposed to ∼1.25 μm Ra when machining in the vertical downward (–β_f) direction.     

融冰期与非融冰期水库CO2逸出昼夜变化及CO2分压影响因素研究

以位于黄土高原北洛河流域的南沟水库为研究对象，采用Li-850静态箱法，于融冰期（3月）、非融冰期（5月）对水体CO₂分压（p（CO₂））和水-气界面CO₂逸出（F（CO₂））分别进行了5 d 40次昼夜监测，同时测定了各种水体理化指标，着重对比了水体p（CO₂）在两个时期间的差异和两时期内的昼夜变化特征，系统分析了水体p（CO₂）的影响因素.结果表明：融冰期p（CO₂）（（324.8±59.4）Pa）比非融冰期（（124.9±14.1）Pa）高出近3倍，差异性显著（p<0.05），但两个时期内昼夜p（CO₂）值并无显著性差异（p>0.05）；水体p（CO₂）与水温、pH、叶绿素（Chla）、溶解氧（DO）呈显著负相关，与溶解无机碳（DIC）、溶解有机碳（DOC）呈显著正相关，水体p（CO₂）受流域碳酸盐体系和水温影响最大，相关系数分别达0.92和-0.91，光合呼吸作用的影响其次；研究区小水库F（CO₂）范围为101~1589 g·m^-2·a^-1，是大气持续碳"源"，其平均排放量与个别温带、亚热带小型水库接近，但低于热带水库.     

Effects of disinfection efficiency on microbial communities and corrosion processes in drinking water distribution systems simulated with actual running conditions

The effects of disinfection efficiency on microbial communities and the corrosion of cast iron pipes in drinking water distribution systems (DWDSs) were studied. Two annular reactors (ARs) that simulated actual running conditions with UV/Cl₂ disinfection and chlorination alone were used. High chlorine consumption and corrosion rate were found in the AR with UV/Cl₂. According to functional genes and pyrosequencing tests, a high percentage of iron recycling bacteria was detected within the biofilm of the AR with Cl₂ at early running stage, whereas siderophore-producing bacteria were dominant in the biofilm of the AR with UV/Cl_2. At the early running stage, the sequential use of UV light and an initial high chlorine dosage suppressed the biomass and iron-recycling bacteria in both bulk water and biofilms, thereby forming less protective scales against further corrosion, which enhanced chlorine consumption. Non-metric multidimensional scaling analysis showed that the bacterial communities in the ARs shaped from within rather than being imported by influents. These results indicate that the initial high disinfection efficiency within the distribution system had not contributed to the accumulation of iron-recycling bacteria at the early running stages. This study offer certain implications for controlling corrosion and water quality in DWDSs.     

Coating of γ-Al2O3 on the stainless steel substrate by electrophoretic deposition method

γ-Al₂O₃ coatings were prepared on aluminum-free stainless steel (SUS304) by electrophoretic deposition method. Both X-ray diffraction and scanning electron microscopy were used to study the crystalline structure and morphological features of the coatings. Themo gravimetry-differential termal analysis (TG-DTA) is used to study the thermo-chimerical reaction behavior of coatings. Catalytic activity of coatings is determined by degrading of NO_x. The results indicated that the thickness of the coatings onto SUS304 could reach 5 μm without any exfoliation at optimized conditions. Catalytic properties of samples coated by electrophoretic deposition method were highly enhanced as compared with that of samples prepared by the dip coating method.     

三峡库区典型消落带CH4排放的变化特征及影响因素

为了探讨亚热带水库消落带CH_4的排放规律,选取三峡库区王家沟一典型消落带内5个高程(180、175、165、155及140 m)为研究对象,其中175、165和155 m位于消落带上,180 m高程为永不淹水的陆地,140 m高程为永久淹水对照区.采用静态暗箱、浮箱/气相色谱法对各高程生态系统CH_4的排放进行了为期两年的连续观测.结果表明,175 m和165 m高程在实验观测的第一年CH_4排放通量变化不明显,而155 m和140 m高程处表现为单峰型的夏季CH_4排放高峰;次年在三峡水库实现最高蓄水位175 m后,175 m高程在淹水期间CH_4排放呈现单峰态,之后表现为源汇交替的无规律排放,而165m、155 m以及140 m高程均大致呈现出冬季高CH_4排放的单峰态;在整个观测期间,180 m高程CH_4排放通量较为稳定,未出现明显峰值.另外,位于消落带上的175、165和155 m高程均表现为淹水期CH_4排放大于落干期.各高程处CH_4年累积排放量为140 m(99.58 kg·hm~(-2))155 m(82.98 kg·hm~(-2))165 m(65.38 kg·hm~(-2))180 m(6.32 kg·hm~(-2))175 m(4.27 kg·hm~(-2)),表明淹水时间越长的土壤,其环境更有利于CH_4的产生.相关性分析显示,陆地与消落带落干期的CH_4排放与土壤碳组分及pH无显著相关性,但CH_4排放通量随土壤含水率的增加而增大;水-气界面上,140 m高程CH_4排放通量与水深有显著线性负相关关系;表明土壤含水率是影响消落带落干期CH_4排放的关键因子之一,而水-气界面上CH_4的排放则受到淹水深度的调控.     

Influence of coating method on catalyst activity of AgCl/Al2O3/SUS304 composite plate

The γ-Al₂0₃ and AgCl/Al₂0₃ catalyst powder were coated on a stainless steel substrate by dip coating and electrophoretic deposition method. And AgCl/Al₂0₃ catalyst was produced by three kinds of methods, and the difference between the NOx reduction catalysis of the coated sample was compared. XRD and SEM were used to study the crystalline structure and cross-section of the coatings. The coating of γ-Al₂0₃ with the thickness of 3-5 μm and AgCl/Al₂0₃ catalyst with the thickness of 5-9 μrn were made on the surface of SUS304 plate without exfoliation. The NOx conversion of the coated sample with catalyst was about 70% at the maximum.     

Effect of traffic restriction on atmospheric particle concentrations and their size distributions in urban Lanzhou, Northwestern China

During the 2012 Lanzhou International Marathon, the local government made a significant effort to improve traffic conditions and air quality by implementing traffic restriction measures. To evaluate the direct effect of these measures on urban air quality, especially particle concentrations and their size distributions, atmospheric particle size distributions(0.5–20 μm) obtained using an aerodynamic particle sizer(model 3321, TSI, USA) in June 2012 were analyzed. It was found that the particle number, surface area and volume concentrations for size range 0.5–10 μm were(15.0±2.1) cm-3,(11.8±2.6) μm2/cm3and(1.9±0.6) μm2/cm3, respectively, on the traffic-restricted day(Sunday), which is 63.2%, 53.0% and 47.2% lower than those on a normal Sunday. For number and surface area concentrations, the most affected size range was 0.5–0.7 and 0.5–0.8 μm, respectively, while for volume concentration, the most affected size ranges were 0.5–0.8, 1.7–2.0 and 5.0–5.4 μm. Number and volume concentrations of particles in size range 0.5–1.0 μm correlated well with the number of non-CNG(Compressed Natural Gas) powered vehicles, while their correlation with the number of CNG-powered vehicles was very low, suggesting that reasonable urban traffic controls along with vehicle technology improvements could play an important role in improving urban air quality.     

A chemical characterization of atmospheric aerosol in Sapporo

Monthly mean chemical composition of aerosol with diameter less than 8 μm was identified in Sapporo in 1982. The mass of aerosol was made up of nine components: elemental C, organics, SO₄²⁻, NO₃⁻, NH₄⁺, Cl⁻, Na⁺, soil particles and water. The concentrations of carbonaceous particles (elemental C and organics) was relatively high (12.7–16.0μ m⁻³) in autumn and winter (October–February) due to emission from domestic heating and comprised 36–41% of total aerosol mass. Higher concentration of soil particles was observed in spring (March–May) (9.7–13.1 μg m⁻³) and comprised 22–29% of total aerosol mass due to suspension by strong wind. On the other hand, the concentration of excess SO₄²⁻ (non-sea salt SO₄²⁻), which ranged from 2.6–5.2 μg m⁻³, did not change remarkably with season, and the fraction of excess sulfate increased to 21% in summer (July–August) probably due to photochemical transformation from SO₂. Nitrate concentration was far less than that of SO₄²⁻ throughout the year in Sapporo.     

Horseradish peroxidase microcapsules based on layer-by-layer polyelectrolyte deposition

Polyelectrolyte multilayer microcapsules have been prepared for encapsulating horseradish peroxidase (HRP). The CaCO₃ microparticles containing HRP molecules were prepared and subsequently enwrapped with layer-by-layer (LbL) deposited multilayer films. The LbL films were constructed via an alternate electrostatic adsorption of poly(allylamine) and poly(styrene sulfonate). The CaCO₃ templates were then dissolved in an ethylenediaminetetraacetic acid solution, leaving HRP in the microcapsules. Optical microscope and fluorescence microscope observations indicated that the microcapsules are homogeneous spheres with an average diameter about 7 μm. The encapsulated HRP showed catalytic activity in the oxidation of pyrogallol, suggesting the microcapsules provide a suitable environment for enzymatic reaction. A leakage of HRP from the microcapsules was negligibly small. Therefore, the HRP-containing microcapsules is promising for detection and treatment of phenolic compounds.     

Characterization of refuse landfill leachates of three di erent stages in landfill stabilization process

Landfill leachates with di erent ages (mature leachate, 11 years; semi-mature leachate, 5 years; fresh leachate, under operation) were collected from Laogang Refuse Landfill, Shanghai to characterize the colloid size distribution and variations of leachate. These leachates were separated using micro-filtration and ultra-filtration into specific size fractions, i.e., suspended particles (SP) (> 1.2 m), coarse colloids (CC) (1.2–0.45 m), fine colloids (FC) (0.45 m, 5 kDa/1 kDa molecular weight (MW)), and dissolved organic matters (DM, < 5 kDa/1 kDa MW). The specific colloids in each size fraction were quantified and characterized through chemical oxygen demands (COD), total solid (TS), pH, NH4 +-N, total organic carbon (TOC) and fixed solid (FS). It was found that COD, NH4 +-N and TS in leachate decreased significantly over ages, while pH increased. The dissolved fractions (< 5 kDa/1 kDa) dominated (over 50%) in three leachates in terms of COD, and the organic matter content in dissolved fraction of leachates decreased and the inorganic matter increased as the disposal time extended, with the TOC/COD ratio 30%–7%. Dissolved fractions decreased from 82% to 40% in terms of TOC as the disposal time extended, suggested that the organic matter remained in leachate would form into middle molecular weight substances during the degradation process.     

Effects of nitrogen and phosphorus concentrations on the bioaccumulation of polybrominated diphenyl ethers by Prorocentrum donghaiense

The growth, cellular total lipids, bioaccumulation amount, and bioaccumulation factors (BAFs) of 2,4,4 ′ -tribromodiphenyl ether (BDE28), 2,2 ′ ,4,4 ′ -tetrabromodiphenyl ether (BDE47), and 2,2 ′ ,4,4 ′ ,5-pentabromodiphenyl ether (BDE99) in a semi-continuous culture of Prorocentrum donghaiense were studied in relation to nitrate (0, 128, and 512 μmol/L) and phosphate (0, 8, and 32 μmol/L) concentrations. The BDE28, BDE47, and BDE99 content per cell under 0 μmol N/L were 3.77 × 10 6 , 3.95 × 10 6 , and 4.32 × 10 6 ng/cell, respectively, which were significantly higher than those under 128 and 512 μmol N/L. A nearly 5-fold increase in polybrominated diphenyl ether (PBDE) content per algal cell was found between 0 and 8 μmol P/L and between 8 and 32 μmol P/L. With increasing N and P concentrations, the PBDE content per volume of algal culture and the accumulation percentage of available PBDEs declined slightly. The BAFs for the PBDEs based on lipids showed that the logBAF lip under 0 μmol N/L was higher than those under 128 and 512 μmol N/L. The logBAF lip under 0 μmol P/L was higher than that under 8 μmol P/L but lower than that under 32 μmol P/L. Correlation analysis indicated a significant negative correlation between nutrient concentration and cellular total lipids, as well as the PBDE content per cell. The results indicate that different N and P concentrations change the total lipids content of P. donghaiense, thereby resulting in varying PBDE accumulation.     

酸性条件下黄铁矿氧化机制的研究

以黄铁矿粉末制备成的碳糊电极为工作电极,利用循环伏安曲线和极化曲线等电化学手段,对酸性条件下黄铁矿的氧化过程和机制进行了研究.结果表明,黄铁矿的氧化主要包括以下两个过程:首先,黄铁矿(FeS2)矿物晶格中的Fe2+溶出而被氧化为Fe3+,此过程会伴随有如硫单质、缺铁硫化物(Fe1-xS2)和多硫化物(FeSn)等氧化中间产物的生成,覆盖在黄铁矿的表面而形成一层钝化膜,阻碍了其氧化溶解过程;接着,黄铁矿表面的钝化膜被进一步氧化为可溶性的SO24-.在酸性条件下,黄铁矿氧化反应的最终产物为Fe3+和SO24-.另外,在所研究的酸度范围内,随着H2SO4溶液浓度的增大,体系的开路电位和腐蚀电位均正移,氧化和还原的峰电流值升高,腐蚀电流增大,说明增加体系的酸度会促进黄铁矿的氧化过程.     

Anoxic gas recirculation system for fouling control in anoxic membrane reactor

Anoxic gas recirculation system was applied to control the membrane fouling in pilot-scale 4-stage anoxic membrane bioreactor(MBR). In the anaerobic-anoxic-anoxic-aerobic flow scheme,hydrophilic polytetrafluoroethylene(PTFE) membrane(0.2 μm, 7.2 m2/module) was submerged in the second anoxic zone. During 8 months operation, the average flux of the membrane was 21.3L/(m2·hr). Chemical cleaning of the membrane was conducted only once with sodium hydroxide and sodium hypochlorite. Dissolved oxygen(DO) concentration in the second anoxic zone was maintained with an average of 0.19 ± 0.05 mg/L. Gas chromatography analysis showed that the headspace gas in the second anoxic reactor was mainly consisted of N2(93.0% ± 2.5%), O2(3.8% ± 0.6%), and CO2(3.0% ± 0.5%), where the saturation DO concentration in liquid phase was 1.57 mg/L. Atmospheric O2 content(20.5% ± 0.8%) was significantly reduced in the anoxic gas. The average pH in the reactor was 7.2 ± 0.4. As a result, the recirculation of the anoxic gas was successfully applied to control the membrane fouling in the anoxic MBR.     

An improved procedure for analysis of PM10 filters by X-ray powder diffraction

Speciation results from earlier methods of quantitative analysis of TSP, dichotomous, and PM₁₀ filters for compounds by XRD were often marginal to unacceptable because of very light loadings and the interfering effects of substrate fibres in cases of ultrasonic extraction and concentration. A method for analysis of very lightly loaded PM₁₀ filters has been developed, using ultrasonic particle stripping, X-ray transmission of unloaded blank filters, substrate diffraction X-ray analysis, and mass absorption balance, along with the usual X-ray diffraction scanning. Analysis of a set of filters having less than 105 μg m cm⁻² sample load is used to illustrate the improved procedure.     

Air pollutant concentrations in Varanasi,India

This study reports the diurnal patterns in the concentrations of ozone (O₃), nitrogen dioxide (NO₂), sulphur dioxide (SO₂) and total suspended particulate matter (TSP) in the urban atmosphere of Varanasi city in India during 1989. The city was divided into five zones and three monitoring stations were selected in each zone.Ambient concentrations of NO₂ and SO₂ were maximum during winter but ozone and TSP concentrations were highest during summer. The measured maximum concentrations (2-h average) were 150 and 231 μg m⁻³ (0.078 and 0.086 ppm) for NO₂ and SO₂, respectively, for the winter season. Ozone and TSP concentrations reached a maximum of 160 (0.08 ppm) and 733 μg m⁻³, respectively, in the summer. NO₂ and SO₂ concentrations peaked in the morning and evening. Peak concentrations of O₃ occurred in the afternoon, generally between noon and 4 p.m. Maximum concentrations of O₃, NO₂, SO₂ and TSP were measured in zones I and II, and minimum in zone V.