Accelerated ash accumulation method for diesel particulate filter and its characterization: a review

ABSTRACT

It is well known that high-efficiency wall-flow particulate filter is the most commonly used technology that can effectively reduce both particulate matter (PM) and particulate number (PN) to comply with the latest emission legislations. Ash, defined as the noncombustible, non-evaporative residue derived mostly from lubricants, has critical impact on engine backpressure, particulate filter filtration efficiency and durability performance, therefore, the investigation of ash impact on particulate filter is of great importance. Due to cost-saving potential, several published methods from different laboratories for accelerated ash loading under carefully controlled conditions are described in this review, including some characterization methods that have been used for the evaluation of filter performance. In addition, the impact of ash deposit on back pressure and regeneration performance are also discussed in this review.     

基于RS/GIS的武汉市九峰城市森林保护区景观结构特征及规划对策

大型的城市森林绿地是城市生态框架的重要组成部分,其景观结构的优化有助于城市生态系统结构与功能稳定。九峰城市森林保护区是武汉近郊最大的森林绿地。应用快鸟遥感影像并结合实地调查,在RS和GIS的支持下对九峰城市森林保护区的景观结构进行了分析,并探讨了森林景观的规划对策。结果表明：九峰城市森林保护区景观分为林地、农耕地、苗圃地、水域、建设用地、墓地、荒地、草地和裸岩9个景观类型,263个斑块,其中林地最多,占总面积的36.56%,占斑块总数的8.75%,为景观基质,但对景观过程的控制作用不强。建设用地和农耕地斑块形状最为复杂,易造成人类活动干扰的扩散。林地成片分布,破碎化程度较低,连通性较高,有利于其资源保护。九峰城市森林保护区表现出整体结构简单,局部结构复杂的特征。针对这些景观结构特征,提出了大幅提高林地比例,压缩建设用地和其他人类活动明显的景观类型面积,构建聚集间有离析的空间优化格局,加强荒地和裸岩的植被恢复,设置“踏脚石”斑块和建立保护性廊道的景观优化对策,以期为九峰城市森林保护区的规划与管理提供依据。     

Effects of dissolved inorganic carbon and nutrient levels on carbon fixation and properties of Thermosynechococcus sp. in a continuous system

The concept of CO₂ chemo-absorption by sodium hydroxide in a wet scrubber followed by microalgae cultivation was used as a means to reduce the major greenhouse gas. A thermophilic and alkaline tolerable cyanobacterium named Thermosynechococcus CL-1 (TCL-1) was cultivated in continuous system, with a carbonate-bicarbonate buffer as carbon source. The effects of dissolved inorganic carbon (DIC_in) and nutrient levels in influent on cell mass productivity, DIC removal efficiency, and alkaline solution regeneration by TCL-1 were investigated. The results show the highest cell mass productivity reaches 1.7 g L⁻¹ d⁻¹ under the highest DIC and nutrients level. Conversely, the best regeneration of alkaline solution proceeds from pH 9.5 to 11.3 under the lowest level. In addition, the highest ΔDIC (DIC consumption) and DIC removal efficiency are 42 mM and 43% at 113.2 and 57 mM DIC_in, respectively.     

Qualitative impacts of Senna spectabilis on distribution of welfare: A household survey of dependent communities in Budongo Forest Reserve,Uganda

This paper presents the results of a household survey designed to qualitatively evaluate the impacts of the invasive alien species Senna spectabilis on the distribution of welfare across dependent communities in the Budongo Forest Reserve (BFR) in Uganda. The BFR is the largest forest reserve in Uganda, with globally significant conservation values. The study establishes that households in the BFR have high levels of knowledge as to its conservation values; they are aware of the invasiveness of S. spectabilis and its potential to compromise the conservation values of the BFR, and that S. spectabilis confers tangible benefits to dependent households, whose levels significantly vary with proximity to the reserve. The study concludes by evaluating strategies that are designed to manage the spread of S. spectabilis in the BFR and which consider its demonstrated socio‐economic impacts.     

Nitrogen leaching and acidification during 19 years of NH₄NO₃ additions to a coniferous-forested catchment at Gårdsjön, Sweden (NITREX)

The role of nitrogen (N) in acidification of soil and water has become relatively more important as the deposition of sulphur has decreased. Starting in 1991, we have conducted a whole-catchment experiment with N addition at Gårdsjön, Sweden, to investigate the risk of N saturation. We have added 41 kg N ha⁻¹ yr⁻¹ as NH₄NO₃ to the ambient 9 kg N ha⁻¹ yr⁻¹ in fortnightly doses by means of sprinkling system. The fraction of input N lost to runoff has increased from 0% to 10%. Increased concentrations of NO₃ in runoff partially offset the decreasing concentrations of SO₄ and slowed ecosystem recovery from acid deposition. From 1990-2002, about 5% of the total N input went to runoff, 44% to biomass, and the remaining 51% to soil. The soil N pool increased by 5%. N deposition enhanced carbon (C) sequestration at a mean C/N ratio of 42-59 g g⁻¹.     

甲苯气体的动态吸附净化及吸附剂再生实验研究

研究了活性炭纤维(ACF)对甲苯气体的动态吸附净化过程及热空气解吸脱附再生过程.采用3种经验方程对ACF的吸附等温线进行拟合,其中Langmuir方程拟合效果最好,拟合相关系数R2 =0.9960,说明在给定的浓度范围内,ACF对甲苯的吸附是以单分子层吸附为主.穿透曲线实验表明,ACF对甲苯吸附效果较好,Yoon-Ne...     

Emission factors for PCDD/PCDF and dl-PCB from open burning of biomass

The Stockholm Convention on Persistent Organic Pollutants includes in its aims the minimisation of unintentional releases of polychlorinated dibenzo-dioxins and dibenzofurans (PCDD/PCDF) and dioxin like PCB (dl-PCB) to the environment. Development and implementation of policies to achieve this aim require accurate national inventories of releases of PCDD/PCDF/dl-PCB. To support this objective, the Conference of Parties established a process to review and update the UNEP Standardized Toolkit for Identification and Quantification of Dioxin and Furan Releases. An assessment of all emission inventories was that for many countries open burning of biomass and waste was identified as the major source of PCDD/PCDF releases. However, the experimental data underpinning the release estimates used were limited in number and, consequently, confidence in the accuracy of the emissions predictions was low. There has been significant progress in measurement technology since the last edition of the Toolkit in 2005. In this paper we reassess published emission factors for release of PCDD/PCDF and dl-PCB to land and air.In total, four types of biomass and 111 emission factors were assessed. It was found that there are no systematic differences in emission factors apparent between biomass types or fire classes. The data set is best described by a lognormal distribution. The geometric mean emission factors (EFs) for releases of PCDD/PCDF to air for the four biomass classes used in the Toolkit (sugarcane, cereal crops, forest and savannah/grass) are 1.6 μg TEQ (t fuel)⁻¹, 0.49 μg TEQ (t fuel)⁻¹, 1.0 μg TEQ (t fuel)⁻¹ and 0.4 μg TEQ (t fuel)⁻¹, respectively. Corresponding EFs for release of PCDD/PCDF to land are 3.0 ng TEQ (kg ash)⁻¹, 1.1 ng TEQ (kg ash)⁻¹, 1.1 ng TEQ (kg ash)⁻¹ and 0.67 ng TEQ (kg ash)⁻¹. There are now also sufficient published data available to evaluate EFs for dl-PCB release to air for sugarcane, forest and grass/savannah; these are 0.03 μg TEQ (t fuel)⁻¹, 0.09 μg TEQ (t fuel)⁻¹ and 0.01 μg TEQ (t fuel)⁻¹, respectively. The average EF for dl-PCB release to land is 0.19 ng TEQ (kg ash)⁻¹. Application of these EFs to national emissions of PCDD/PCDF for global estimates from open burning will lower previous estimates of PCDD/PCDF releases to air and to land by 85% and 90%, respectively. For some countries, the ranking of their major sources will be changed and open burning of biomass will become less significant than previously concluded.     

Short- and long-term patterns of ¹³⁷Cs in fish and other aquatic organisms of small forest lakes in southern Finland since the Chernobyl accident

We summarize the patterns of ¹³⁷Cs activity concentrations and transfer into fish and other biota in four small forest lakes in southern Finland during a twenty-year period following the Chernobyl accident in April 1986. The results from summer 1986 showed fastest accumulation of ¹³⁷Cs into planktivorous fishes, i.e. along the shortest food chains. Since 1987, the highest annual mean values of ¹³⁷Cs have been recorded in fish occupying the highest trophic levels, for perch (Perca fluviatilis) 13,600 Bq/kg (ww) and for pike (Esox lucius) 20,700 Bq/kg (ww). At the same time, activity concentrations of ¹³⁷Cs in crustacean zooplankton and Asellus aquaticus have ranged between 1000 and 19,500 Bq/kg (dw). In 2006, 5-28% of the 1987 ¹³⁷Cs activity concentration levels were still present in perch and pike. Since 1989 their ¹³⁷Cs activity concentrations in oligohumic seepage lakes have remained significantly higher than in polyhumic drainage lakes due to the increased transfer of ¹³⁷Cs into fish in the seepage lakes with lower electrolyte concentrations, longer water retention times and lower sedimentation rate.     

电增强载铝活性炭纤维吸附除氟的效果与影响因素

以含氟地下水为研究对象,采用自制电促吸附除氟反应器,开展电增强载铝活性炭纤维吸附除氟的动态实验,研究了不同电压、极板间距、地下水碱度和流速对吸附除氟效果的影响。实验结果表明,在负载炭纤维毡的电极一端加正电,可以提高除氟效果。当电压为1.6 V时除氟效果较好,单位面积炭毡处理达标水量为56.7 L/m2;极板间距设置为4mm时电吸附反应器除氟效果最佳;通过调节pH改变地下水碱度,当地下水pH调节为5.5时,电吸附反应器除氟效果较未调节前提高50%;当采用3对电极板,流速为1.88 m/h时,达到最高表面处理负荷2 073.6 L/(m2.d);探究了反应器的反洗再生方式,并连续进行了吸附再生的动态实验;穿透的反应器以Al2(SO4)3溶液为再生液并采用反向加电1.6 V的方式,可以达到较好的再生效果,实现连续动态运行。     

粉煤灰的改性、成型及深度除磷应用

选择合适的改性剂对粉煤灰进行改性,通过有机高分子交联方法对改性粉煤灰进行成型处理,并采用静态吸附法评价改性粉煤灰的深度除磷效果。采用1 g氢氧化铝改性粉煤灰处理100 mL磷质量浓度为10.0 mg/L的模拟废水,磷去除率可达99.70％,处理后模拟废水中磷质量浓度低于0.50 mg/L, 达到GB8978-1996《污水综合排放标准》。成型处理可提高粉煤灰的沉降速率,改善灰水分离效果。经超声再生后的成型氢氧化铝改性粉煤灰的磷去除率仍可达67.9％。