Metals emitted from heavy-duty diesel vehicles equipped with advanced PM and NOX emission controls

Emission factors for elemental metals were determined from several heavy-duty diesel vehicles (HDDV) of 1998–2007 vintage, operating with advanced PM and/or NO_X emissions control retrofits on a heavy-duty chassis dynamometer, under steady state cruise, transient, and idle conditions. The emission control retrofits included diesel particulate filters (DPF): catalyzed and uncatalyzed, passive and active prototype vanadium- or zeolite-based selective catalytic reduction (SCR) systems, and a catalyzed DPF fitted on a hybrid diesel electric drive vehicle. The prototype SCR systems in combination with DPF retrofits are of particular interest because they represent the expected emissions controls for compliance with PM and NO_X regulations in 2010. PM samples from a full-exhaust dilution tunnel were collected on bulk filters, and on a Personal Cascade Impactor Sampler (PCIS) for total and water-soluble elemental analysis. All the DPFs significantly reduced emissions of total trace elements (>85% and >95% for cruise and for the Urban Dynamometer Driving Schedule (UDDS), respectively). However, we observed differences in the post-retrofit metals emissions due to driving cycle effects (i.e., exhaust temperature) and type of retrofit. In general, the metals emissions over cruise conditions (which leads to higher exhaust temperatures) were substantially different from the emissions over a transient cycle or while idling. For instance, during cruise, we observed higher levels of platinum (1.1 ± 0.6–4.2 ± 3.6 ng km^?1) for most of the retrofit-equipped vehicle tests compared to the baseline configuration (0.3 ± 0.1 ng km^?1). The vanadium-based DPF + SCR vehicle during cruise operation exhibited emissions of vanadium (562 ± 265 ng km^?1) and titanium (5841 ± 3050 ng km^?1), suggesting the possible release of actual SCR wash-coat (V₂O₅/TiO₂) from the catalyst under the higher temperatures characteristic of cruise operation. The vanadium emissions exhibited a bi-modal mass size distribution, with modes at <0.25 μm and 1.0–2.5 μm size ranges for the vanadium-based SCR system. For the DPF + SCR systems, a greater fraction of the metal emissions from the zeolite-based system is water-soluble compared to emissions from the vanadium-based system.     

Application of high OLR-fed aerobic granules for the treatment of low-strength wastewater：Performance, granule morphology and microbial community

Aerobic granules, pre-cultivated at the organic loading rate (OLR) of 3.0 kg COD/(m3 ·day), were used to treat low-strength wastewater in two sequencing batch reactors at low OLRs of 1.2 and 0.6 kg COD/(m3 ·day), respectively. Reactor performance, evolution of granule morphology, structure and microbial community at low OLRs under long-term operation (130 days) were investigated. Results showed that low OLRs did not cause significant damage to granule structure as a dominant granule morphology with size over 540 μm was maintained throughout the operation. Aerobic granules at sizes of about 750 μm were finally obtained at the low OLRs. The granule reactors operated at low OLRs demonstrated effective COD and ammonia removals (above 90%), smaller granule sizes and less biomass. The contents of extracellular polymeric substances in the granules were decreased while the ratios of exopolysaccharide/exoprotein were increased (above 1.0). The granules cultivated at the low OLRs showed a smoother surface and more compact structure than the seeded granules. A significant shift in microbial community was observed but the microbial diversity remained relatively stable. Confocal Laser Scanning Microscopy observation showed that the live cells were spread throughout the whole granule, while the dead cells were mainly concentrated in the outer layer of the granule, and the proteins, polysaccharides and lipids were mainly located in the central regime of the granule. In conclusion, granules cultivated at high OLRs show potential for treating low-strength organic wastewater steadily under long-term operation.     

An innovative wood-chip-framework substrate used as slow-release carbon source to treat high-strength nitrogen wastewater

Removal of nitrogen in wastewater before discharge into receiving water courses is an important consideration in treatment systems. However, nitrogen removal efficiency is usually limited due to the low carbon/nitrogen (C/N) ratio. A common solution is to add external carbon sources, but amount of liquid is difficult to determine. Therefore, a combined wood-chip-framework substrate (with wood, slag and gravel) as a slow-release carbon source was constructed in baffled subsurface-flow constructed wetlands to overcome the problem. Results show that the removal rate of ammonia nitrogen (NH₄⁺-N), total nitrogen (TN) and chemical oxygen demand (COD) could reach 37.5%–85%, 57.4%–86%, 32.4%–78%, respectively, indicating the combined substrate could diffuse sufficient oxygen for the nitrification process (slag and gravel zone) and provide carbon source for denitrification process (wood-chip zone). The nitrification and denitrification were determined according to the location of slag/gravel and wood-chip, respectively. Nitrogen removal was efficient at the steady phase before a shock loading using slag-wood-gravel combined substrate because of nitrification–denitrification process, while nitrogen removal was efficient under a shock loading with wood-slag-gravel combined substrate because of ANAMMOX process. This study provides a new idea for wetland treatment of high-strength nitrogen wastewater.     

不同放牧强度对高寒草甸生态系统呼吸的早期影响

放牧是高寒草甸一种重要的利用方式,对土壤理化性质和植被会产生重要影响,研究放牧对高寒草甸生态系统呼吸的影响对估算碳交换和制定合理放牧政策具有重要意义.利用静态箱-气象色谱法,于2012年8月到2013年7月在青藏高原东缘高寒草甸对轻度、中度和重度3种放牧强度下的生态系统呼吸进行每月至少一次的连续观测,以估算高寒草甸生态系统呼吸,并探讨放牧强度对生态系统呼吸的作用.结果显示:轻度、中度和重度放牧条件下,年均生态系统呼吸(以C计)分别为226.33±62.30、213.63±53.22和215.15±53.19 mg m~(-2) h~(-1),三者之间无显著差异(P0.05);在生长季生态系统呼吸分别为367.97±47.86、324.62±44.95和348.37±43.10 mg m~(-2) h~(-1),在非生长季生态系统呼吸分别为105.81±22.13、96.55±14.69和110.61±16.89 mg m~(-2) h~(-1),在不同放牧强度下生态系统呼吸均表现出明显的季节特征,但在相同季节不同放牧强度间生态系统呼吸差异不显著;月累积降水量与生态系统呼吸呈显著正相关关系;该区域放牧地生态系统平均年累积呼吸为472.63 g m~(-2) h~(-1).本研究表明,在试验初期不同放牧强度对生态系统呼吸无显著作用.     

Evaluating the hydrodynamics of a round jet in a vegetated crossflow through large eddy simulation

Environmental Fluid Mechanics - Vegetation plays an important role on the turbulence structures of the effluent spreading in an open channel, which are insufficiently studied. This paper employs a...     

灰霾天气与大气颗粒物的相关性研究综述

随着城市化进程的迅速发展,城市大气污染加剧,灰霾天气也随之增多。综述了灰霾天气期间大气颗粒物在时空分布和污染水平2方面的污染特征,分析了大气颗粒物与能见度相关性,介绍了国内外对灰霾天气期间大气污染物的组成及源解析方面的研究进展,并提出了今后灰霾天气的研究方向。     

A study of emissions from a Euro 4 light duty diesel vehicle with the European particulate measurement programme

The California Air Resources Board, CARB, has participated in a program to quantify particulate matter (PM) emissions with a European methodology, which is known as the Particulate Measurement Programme (PMP). The essence of the PMP methodology is that the diesel PM from a Euro 4 vehicle equipped with a Diesel Particulate Filter (DPF) consists primarily of solid particles with a size range greater than 23 nm. The PMP testing and the enhanced testing performed by CARB have enabled an increased understanding of both the progress that has been made in PM reduction, and the future remaining challenges for new and improved DPF-equipped diesel vehicles. A comparison of measured regulated emissions and solid particle number emissions with the results obtained by the PMP participating international laboratories was a success, and CARB’s measurements and standard deviations compared well with the other laboratories. Enhanced measurements of the influence of vehicle conditioning prior to testing on PM mass and solid particle number results were performed, and some significant influences were discovered. For example, the influence of vehicle preconditioning on particle number results was significant for both the European and USA test driving cycles. However, the trends for the cycles were opposite with one cycle showing an increase and the other cycle showing a decrease in particle number emissions. If solid particle size distribution and total particle numbers are to be used as proposed in PMP, then a greater understanding of the quality and errors associated with measurement technologies is advisable.In general, particle counting instruments gave results with similar trends, but cycle-to-cycle testing variation was observed. Continuous measurements of particle number concentrations during test cycles have given detailed insight into PM generation. At the present time there is significant variation in the capabilities of the particle counting instruments in terms of particle size and concentration.Current measurements show the existence of a large number of volatile and semi-volatile particles of yet-to-be-resolved chemical composition in diesel exhaust, especially during DPF regeneration, and these particles are not included in the PMP methodology because they are smaller than 20 nm. It will be very challenging to improve our understanding of this class of diesel particulate matter.     

我国环境监测能力建设的现状及建议

对我国环境监测能力建设的现状进行了分析。指出我国环境监测能力建设取得了明显进展 ,但地区差异很大 ,整体水平不高 ,存在的主要问题是投入不足、体制不顺。提出应加强环境监测管理 ,加大投入 ,建设水质、空气、重点污染源自动监测系统 ,建立国家级开放式环境分析实验室和全国生态与环境监测网络 ,完善数据卫星传输系统 ,全面提高环境监测能力。     

水质监测中存在的若干技术问题

在全国持证上岗、计量认证、实验室现场考核和《亚洲地区实验室精度管理手册》编制过程及监测质量调查的基础上,发现我国部分环境监测站在水质监测的实际操作、试样前处理、监测分析方法选择及数据分析等方面尚存在一些技术问题。在分析这些问题的同时,提出了解决办法和完善我国质量保证指标体系的建议。     

Uptake and distribution of rare earth elements in rice seeds cultured in fertilizer solution of rare earth elements

The uptake behavior of rare earth elements (REEs) under pot conditions using deionized water and a REE fertilizer solution as the culture media as well as the distribution of REEs in rice proteins were studied. The uptake of REEs in rice seeds increased dramatically after a lag period of approximately three days. Roots can accumulate a much higher content of REEs than germs and the resting seeds. The REE content in each water-soluble (albumin) and salt-soluble (globulin) component of the rice seeds accounted for 5-8% and 4-6% of the total REEs, respectively. However, there are less than 1.5% of the total REEs were found in the alcohol-soluble (prolamin) and acetic acid-soluble (glutelin) components. The high performance liquid chromatography (HPLC) in the gel permeation and the reserved-phase were used to monitor changes in the molecular weight distribution changes of the soluble proteins of rice seeds during germination after having been cultured in the same solution for seven days. No changes occurred in the prolamin, while a slight change occurred in the albumin, globulin and glutelin. Fractionation of the albumin of rice seeds cultured in a REE fertilizer solution on the Sephadex G-100 column indicated that REEs, especially Ce, La, Pr and Nd, were associated mainly with biological compounds of a molecular weight between 10,000 and 12,000.