Investigation of titanium liquid/gas diffusion layers in proton exchange membrane electrolyzer cells

In a proton exchange membrane electrolyzer cell (PEMEC), liquid/gas diffusion layer (LGDL) is expected to transport electrons, heat, and reactants/products to and from the catalyst layer with minimum voltage, current, thermal, interfacial, and fluidic losses. In addition, carbon materials, which are typically used in PEM fuel cells (PEMFCs), are unsuitable in PEMECs due to the high ohmic potential and highly oxidative environment of the oxygen electrode. In this study, a set of titanium gas diffusion layers with different thicknesses and porosities are designed and examined coupled with the development of a robust titanium bipolar plate. It has been found that the performance of electrolyzer improves along with a decrease in thickness or porosity of the anode LGDL of titanium woven meshes. The ohmic resistance of anode LGDL and contact resistance between anode LGDL and the anode catalyst play dominant roles in electrolyzer performance, and better performance can be obtained by reducing ohmic resistance. Thin titanium LGDLs with straight-through pores and optimal pore morphologies are recommended for the future developments of low-cost LGDLs with minimum ohmic/transport losses.     

Is the bone tissue of ring-billed gulls breeding in a pollution hotspot in the St. Lawrence River,Canada, impacted by halogenated flame retardant exposure?

Bone metabolism is a tightly regulated process that controls bone remodeling and repair in addition to maintaining circulating calcium and phosphate levels. It has been shown that certain organohalogen contaminants may adversely impact bone tissue metabolism and structure in wildlife species. However, exceedingly few studies have addressed the bone-related effects of organohalogen exposure in birds. The objective of the present study was to investigate the associations between markers of bone metabolism and structural integrity, and concentrations of established and current-use halogenated flame retardants (FRs) in ring-billed gulls (Larus delawarensis) nesting in a known FR hotspot area in the St. Lawrence River (Montreal, Canada). Bone metabolism was assessed using plasma calcium and inorganic phosphate levels, and alkaline phophatase activity, while bone (tarsus; trabecular and cortical sections) structure quality was examined using the percentage of bone tissue comprised in the total bone volume (Bv/Tv) and bone mineral density (BMD). Bv/Tv and BMD of the tarsus tended (not significant) to be positively associated with circulating calcium levels in male ring-billed gulls. Moreover, concentrations of FRs in male bird liver (brominated diphenyl ether (BDE)-154, -183, -201, and -209) and plasma (BDE-209) were negatively correlated with trabecular and cortical BMD of the tarsus. These correlative associations may suggest light demineralization of bone tissue associated with FR exposure in male ring-billed gulls. Present findings provide some evidence that bone (tarsus) metabolism and mineral composition may be impacted in high FR-exposed (mainly to PBDEs) ring-billed gulls breeding in the highly urbanized Montreal region.     

Sound management of brominated flame retarded (BFR) plastics from electronic wastes: State of the art and options in Nigeria

Management of flame retarded plastics from waste electrical and electronic equipment (WEEE) has been posing a major challenge to waste management experts because of the potential environmental contamination issues especially the formation of polybrominated-dioxins and -furans (PBDD/F) during processing. In Nigeria, large quantities of electronic waste (e-waste) are currently being managed—a significant quantity of which is imported illegally as secondhand electronics. As much as 75% of these illegal imports are never reused but are rather discarded. These waste electronic devices are mostly older equipment that contains brominated flame retardants (BFRs) such as penta-brominated diphenyl ethers (PBDEs), and polybrominated biphenyls (PBBs) which are presently banned in Europe under the EU WEEE and RoHS Directives. Risk assessment studies found both to be persistent, bio-accumulative and toxic. The present management practices for waste plastics from WEEE in Nigeria, such as open burning and disposal at open dumps, creates potential for serious environmental pollution. This paper reviews the options in the environmentally sound management of waste plastics from electronic wastes. Options available include mechanical recycling, reprocessing into chemicals (chemical feedstock recycling) and energy recovery. The Creasolv^® and Centrevap^® processes, which are the outcome of the extensive research at achieving sound management of waste plastics from WEEE in Europe, are also reviewed. These are solvent-based methods of removing BFRs and they presently offer the best commercial and environmental option in the sound management of waste BFR-containing plastics. Because these developments have not been commercialized, WEEE and WEEE plastics are still being exported to developing countries. The industrial application of these processes and the development of eco-friendlier alternative flame retardants will help assure sound management of WEEE plastics.     

火焰原子吸收光谱法测定畜禽粪便中铜和锌

采用冻干法-全量酸消解-火焰原子吸收光谱法测定畜禽粪便中铜和锌,优化了试验条件.铜和锌分别在0 mg/L～3.00 mg/L和0 mg/L～1.00 mg/L范围内线性良好,检出限分别为6 mg/kg和2 mg/kg(按取0.5 g试样消解定容至50 mL计算),粪便试样测定的RSD分别为1.3%和3.7%,加标回收率分别为104%和107%.     

厦门市气候特征变化与酸雨形成研究

对地面风场的研究表明,厦门存在局地和海陆风环流,自1955年以来年平均风速、混合层厚度均呈现下降趋势,大气污染物的水平和垂直扩散能力也呈下降趋势。降水酸度随海拔高度的变化情况表明,海陆风环流有利于酸性污染物的积累,且锋面降水过程中的光化学污染加重了降水的酸化程度。     

改性沸石分离富集-火焰原子吸收光谱法测定长江水中镉

采用改性沸石分离富集-火焰原子吸收光谱法测定长江水中微量镉,优化了富集和洗脱条件,讨论了干扰离子的影响。方法在0μg~4.00μg范围内线性良好,检出限为0.214μg/L,长江水平行测定的RSD为1.8%,加标回收率为99.0%~104%。     

Satellite and Ground Based Monitoring of Aerosol Plumes

Plumes of atmospheric aerosol have been studied using a rangeof satellite and ground-based techniques. The Sea-viewing WideField-of-view Sensor (SeaWiFS) has been used to observe plumesof sulphate aerosol and Saharan dust around the coast of theUnited Kingdom. Aerosol Optical Thickness (AOT) was retrievedfrom SeaWiFS for two events; a plume of Saharan dusttransported over the United Kingdom from Western Africa and aperiod of elevated sulphate experienced over the Easternregion of the UK. Patterns of AOT are discussed and related tothe synoptic and mesoscale weather conditions. Furtherobservation of the sulphate aerosol event was undertaken usingthe Advanced Very High Resolution Radiometer instrument(AVHRR). Atmospheric back trajectories and weather conditionswere studied in order to identify the meteorologicalconditions which led to this event. Co-located ground-basedmeasurements of PM₁₀ and PM_2.5 were obtained for 4sites within the UK and PM_2.5/10 ratios were calculatedin order to identify any unusually high or low ratios(indicating the dominant size fraction within the plume)during either of these events. Calculated percentiles ofPM_2.5/10 ratios during the 2 events examined show thatthese events were notable within the record, but were in noway unique or unusual in the context of a 3 yr monitoringrecord. Visibility measurements for both episodes have beenexamined and show that visibility degradation occurred duringboth the sulphate aerosol and Saharan dust episodes.     

"燃烧假人"测试方法中燃烧系统设计研究

“燃烧假人”测试方法中火场环境生成是对服装整体阻燃性能进行定量评估的前提，而燃烧系统设计是实现具有可重复性、一致性、均匀性等特点火场环境的关键。本文对燃烧系统的需求进行了分析，对其构成及设计思路进行了研究，提出了一种解决方案。