Research on ammonia emissions characteristics from light-duty gasoline vehicles

In this study, ammonia emissions characteristics of typical light-duty gasoline vehicles were obtained through laboratory vehicle bench test and combined with New European Driving Cycle (NEDC) condition and Worldwide Harmonized Light Vehicles Test Cycle (WLTC) condition. The influence of ambient temperature on ammonia emissions is mainly concentrated in the cold start stage. The influence of ambient temperature on ammonia emission is shown that the ammonia emissions of light-duty gasoline vehicles under ambient temperature conditions (14 and 23°C) are lower than those under low ambient temperature conditions (?7°C) and high ambient temperature conditions (35 and 40°C). The influence of TWC on ammonia emission is shown that ammonia is a by-product of the catalytic reduction reaction of conventional gas pollutants in the exhaust gas in the TWC. Under NEDC operating conditions and WLTC operating conditions, ammonia emissions after the catalyst are 45 times and 72 times that before the catalyst, respectively. In terms of ammonia emissions control strategy research, Pd/Rh combination can reduce NH₃ formation more effectively than catalyst with a single Pd formula. Precise control of the engine's air-fuel ratio and combination with the optimized matched precious metal ratio TWC can effectively reduce ammonia emissions.     

延迟焦化装置非密闭除焦工序职业病危害程度分析

目的 了解延迟焦化装置非密闭除焦工序职业病危害程度.方法 选取某大型炼化企业延迟焦化装置一套,通过现场调查,确定非密闭式除焦工序存在的主要职业病危害因素及其接触岗位,对职业病危害因素进行检测,评判并分析各岗位化学有害因素职业接触水平,确定职业病危害程度.结果 除焦工岗位接触硫化氢、粉尘危害因素检测结果超标,装车工接触粉尘危害因素检测结果超标.除焦工硫化氢、粉尘接触水平均为Ⅳ级,装车工粉尘接触水平为Ⅳ级.结论 加强延迟焦化装置非密闭除焦工序个人使用的职业病防护用品的配备,新建延迟焦化装置应尽量选择密闭除焦技术,当前运行的存在非密闭除焦工序的延迟焦化装置应进行工艺技术改造.     

Characteristics of one-year observation of VOCs, NOx, and O3 at an urban site in Wuhan, China

A continuous online observation of ozone and its precursors(NOx, VOCs) was carried out in central urban Wuhan from September 2016 to August 2017. The concentration levels of ozone,NOx, VOCs and their variations in urban Wuhan were analyzed, as well as effects of VOCs on ozone photochemical generation and the main controlling factors for ozone production. During the observation period, the average concentrations of ozone and NOx in Wuhan was 22.63 and30.14 ppbv, respectively, and the average concentration of VOCs was 32.61 ppbv(42.3% alkanes,13.0% alkenes, 10.0% aromatics, 7.3% acetylene, 9.9% OVOCs, and 10.5% halohydrocarbons).Ozone concentration was higher in spring and summer as compared with autumn and winter,wheras VOCs and NOx concentratios were lower in spring and summer but higher in autumn and winter. Aromatics and alkenes, two of VOCs species, showed the highest contributions to ozone formation potential in Wuhan(35.7% alkenes, 35.4 aromatics, 17.5% alkanes, 8.6% OVOCs,1.6% halogenated hydrocarbons, and 1.4% acetylene). Among all VOCs species, those with the highest contribution were ethylene, m-xylene, toluene, propylene and o-xylene. The contribution of these five compounds to the total ozone formation potential concentration was 43.90%.Ozone-controlling factors in Wuhan changed within one day; during the early morning hours(6:00–9:00), VOCs/NOx was low, and ozone generation followed a VOCs-limited regime.However, during the peak time of ozone concentration(12:00–16:00), the ratio of VOCs/NOx was relatively high, suggesting that ozone generation followed a NOx-limited regime.     

Comparison of inorganic chemical compositions of atmospheric TSP, PM10 and PM2.5 in northern and southern Chinese coastal cities

To compare the inorganic chemical compositions of TSP(total suspended paniculate),PM_(10)(particulate matter with an aerodynamic diameter less than 10 μm) and PM_(2.5)(particulate matter with an aerodynamic diameter less than 2.5 μm) in southern and northern cities in China,atmospheric particles were synchronously collected in Dalian(the northern city)and Xiamen(the southern city) in spring and autumn of 2004.The mass concentrations,twenty-three elements and nine soluble ions were assessed.The results show that in Dalian,the mass concentrations of Mg,Al,Ca,Mn and Fe in spring were 4.0-10.1,2.6-8.0,4.1-12,1.2-3.6 and 2.9-7.9 times higher,respectively,than those in Xiamen.The dust storm influence is more obvious in Dalian in spring.However,in Xiamen,heavy metals accounted for 13.9%-17.9%of TSP,while heavy metals contributed to 5.5%-9.3%of TSP in Dalian.These concentrations suggest that heavy metal pollution in Xiamen was more serious.In addition,the concentrations of Na~+,Cl~-,Ca~(2+) and Mg~(2+) were higher in Dalian due to the influence of marine aerosol,construction activities and soil dust.The NO~(3-)/SO_4~(2-) ratios in Dalian(0.25-0.49) were lower than those in Xiamen(0.51-0.62),indicating that the contributions of vehicle emission to particles in Xiamen were higher.Coefficient of divergence values was higher than 0.40,implying that the inorganic chemical composition profiles for the particles of Dalian and Xiamen were quite different from each other.     

江门市燃生物质成型颗粒锅炉的排污现状与对策研究

生物质成型颗粒是《江门市能源发展"十三五"规划》中着力发展的能源之一.根据江门市燃生物质成型颗粒锅炉当前的使用状况和排污情况,分析总结了造成颗粒物和氮氧化物超标的原因主要为锅炉内部结构、燃烧操作以及燃生物质成型颗粒质量等.在此基础上,探讨改善江门市燃生物质成型颗粒锅炉污染的对策,提出了科学定位生物质成型颗粒,促进行业健康发展,加快各相关企业升级改造,藉此也为其他地区的燃生物质成型颗粒锅炉提供参考.     

生态保护学的建设与发展

通过简要回顾生态保护工作的发展历程,将生态保护学划分为自然保护学和生态保护学两个阶段。从研究对象及性质、内容与分支、学科基础、学科体系,论述了《环境保护学》的建设和发展,并指明了生态保护学的地位、作用及发展趋势。     

Fractionation and ecological risk of metals in urban river sediments in Zhongshan City, Pearl River Delta

Surface sediments collected from nine urban rivers located in Zhongshan City, Pearl River Delta, were analyzed for total concentration of metals with digestion and chemical fractionation adopting the modified European Community Bureau of Reference (BCR) sequential extraction procedure. The results showed that concentration and fractionation of metals varied significantly among the rivers. The total concentration of eight metals in most rivers did not exceed the China Environmental Quality Standard for Soil, Grade III. The potential ecological risk of metals to rivers were related to the land use patterns, in the order of manufacturing areas > residential areas > agriculture areas. The concentration of Pb in the reducible fraction was relatively high (60.0-84.3%). The dominant proportions of Cd, Zn and Cu were primary in the non-residual fraction (67.0%, 71.8% and 81.4% on average respectively), while the percentages of the residual fractions of Cr and Ni varied over a wide range (43-85% and 24-71% respectively). The approaches of the H?kanson ecological risk index and Secondary Phase Enrichment Factor were applied for ecological risk assessment and metal enrichment calculation. The results indicated Hg and Cd had posed high potential ecological risk to urban rivers in this region. Meanwhile, there was widespread pollution and high enrichment of Cu in river sediments in this region. Multiple regression analysis showed that five water quality parameters (pH, DO, COD(Mn), NH(4)(+)-N, TP) had little influence on the distribution of metal fractionation. This result revealed that the ecological risk of metals was not eliminated along with the improvement in water quality. Correlation studies showed that among the metals, Group A (Cd, As, Pb, Zn Hg, r = 0.730-0.924) and Group B (Cr, Cu, Ni, r = 0.815-0.948) were obtained, and the metal contaminations were from industrial activities rather than residential.     

Gravity currents in two-layer stratified media

An analytical, experimental and numerical study of boundary gravity currents propagating through a two-layer stratified ambient of finite vertical extent is presented. Gravity currents are supposed to originate from a lock-release apparatus; the (heavy) gravity current fluid is assumed to span the entire channel depth, H, at the initial instant. Our theoretical discussion considers slumping, supercritical gravity currents, i.e. those that generate an interfacial disturbance whose speed of propagation matches the front speed, and follows from the classical analysis of Benjamin (J Fluid Mech 31:209?C248, 1968). In contrast to previous investigations, we argue that the interfacial disturbance must be parameterized so that its amplitude can be straightforwardly determined from the ambient layer depths. Our parameterization is based on sensible physical arguments; its accuracy is confirmed by comparison against experimental and numerical data. More generally, measured front speeds show positive agreement with analogue model predictions, which remain strictly single-valued. From experimental and numerical observations of supercritical gravity currents, it is noted that this front speed is essentially independent of the interfacial thickness, ??, even in the limiting case where ?? = H so that the environment is comprised of a uniformly stratified ambient with no readily discernible upper or lower ambient layer. Conversely, when the gravity current is subcritical, there is a mild increase of front speed with ??. Our experiments also consider the horizontal distance, X, at which the front begins to decelerate. The variation of X with the interface thickness and the depths and densities of the ambient layers is discussed. For subcritical gravity currents, X may be as small as three lock lengths whereas with supercritical gravity currents, the gravity current may travel long distances at constant speed, particularly as the lower layer depth diminishes.     

Allozyme polymorphisms in horseshoe crabs, Carcinoscorpius rotundicauda, collected from polluted and unpolluted intertidal areas in Peninsular Malaysia

It has been widely reported that allozyme frequency variation is a potential indicator of heavy metal-induced impacts in aquatic populations. In the present study, wild populations of horseshoe crab (Carcinoscorpius rotundicauda) were collected from contaminated and uncontaminated sites of Peninsular Malaysia. By adopting horizontal starch gel electrophoresis, seven enzyme systems were used to study allozyme polymorphisms. Nine polymorphic loci were observed in C. rotundicauda. The relationships of allozyme variations with the concentrations of Cd, Cu, Ni, and Zn in sediments and in muscle tissues of horseshoe crabs were determined. Based on genetic distance, the lower mean value of Nei??s D (0.017) indicated that both of the contaminated populations of Kg. Pasir Puteh and Kuala Juru were very closely related when compared to the relatively uncontaminated Pantai Lido population. Higher heterozygosities were shown by the contaminated populations when compared to the uncontaminated population. Different allelic frequencies could be observed for the aldolase (ALD; E.C. 2.7.5.1) locus between the contaminated and uncontaminated populations of C. rotundicauda. The dendrogram of genetic relationships of the three populations of C. rotundicauda showed the same clustering pattern as the dendrograms are based on heavy metals in the sediments and in the horseshoe crabs?? abdominal muscles. From the F statistics, the present study showed that the three populations of horseshoe crabs were considered to have undergone moderate genetic differentiation with a mean F _ST value of 0.092 .The current results suggest that allozyme polymorphism in horseshoe crabs is a potential biomonitoring tool for metal contamination, although further validation is required.