Estimating the removal of atmospheric particulate pollution by the urban tree canopy in Beijing北大核心CSCD

Urban green space, particularly the tree canopy, plays an important role in potential mitigation against atmospheric particulate pollution and protecting human health. In this study, current and future air particulate matter [including total suspended particulate (TSP), particulate matter 10 (PM10), and particulate matter 2.5 (PM2.5)] removal by the urban tree canopy of Beijing was estimated. A modeling approach was used based on the distributed measurement evaluation and a modified version. The urban tree canopy of Beijing, including mostly Platycladus sp., Pinus sp., Quercus sp., Robinia pseudoacacia, and economic forests, currently removes about 8.33 million kg/a air particulates, in which TSP accounted for 4.51 million kg/a, PM10 accounted for 2.74 million kg/a, and PM2.5 accounted for 1.08 million kg/a. The study on the removal of air particulates by different aged tree canopies showed that in coniferous trees, the ability to capture air particulates changed in the order of mature and over-mature > near-mature forest > young forest; in broadleaf forest, the ability changed in the order of near-mature forest > mature and over-mature > young forest. For total particulate matter, the biggest contribution was coarse particulates (60.74%); the contribution rate of fine particulates was different owing to different tree species groups. The results suggested that the ability of different trees to capture particles and age of forests varied widely and that suitable trees should be chosen to enhance pollution mitigation for city greening. © 2018 Science Press. All rights reserved.     

Nitrogen removal from summer to winter in a field pilot-scale multistage constructed wetland-pond system

A pilot-scale multistage constructed wetland-pond（MCWP） system with a "pre-ecological oxidation pond, two-stage horizontal subsurface flow constructed wetland（HSCW） and surface flow constructed wetland（SFCW） as the core and postsubmerged plant pond" as the process was used to treat actual polluted river water in the field, and the variation in nitrogen removal from summer to winter was investigated. The results showed that the average total nitrogen（TN） removal efficiency in the MCWP was approxi...     

天水市空气微生物含量分析

用平皿沉降法测定了天水市空气微生物含量,结果证实其空气细菌、真菌及总菌的平均含量分别为5312.3、13．1和5325．4CFU／m3．空气真菌占总菌量的0．2％左右,空气微生物以细菌为主十分明显,所测风景区空气细菌含量与城区的平均水平间差异很大,说明天水市空气已受到较轻的中度污染,闹市区的一些测点空气污染已相当严重。     

局地区域大气污染物氯乙烯总量控制实例研究

污染物总量控制是实现地区可持续发展的有效措施。该文在对天津市某局地区域大气氯乙烯污染现状及污染源调查的基础上,提出了大气氯乙烯总量控制目标和总量负荷分配方案,并对该地区大气氯乙烯环境目标值的可达性进行了分析论证。      

Reduction of mercury emissions from anthropogenic sources including coal combustion

Mercury(Hg)ranks number three,after arsenic(As)and lead(Pb),on the Substance Priority List of the Agency for Toxic Substances and Disease Registry(ATSDR,2019).M...     

Influence of various emission scenarios on ozone in Europe

In this study, we investigated the effect of numerous regulations enforced since 1985 to improve air quality on ozone in Europe with the focus on Switzerland, using the Comprehensive Air Quality Model with Extensions (CAMx) for a specific summer period. Several emission scenarios for the year 2010 were also considered. The model results suggest that the emission reductions of ozone precursors should have been effective to reduce ozone production between 1985 and 2000 in northern Switzerland. However, observations do not indicate any significant change in surface ozone levels since early 1990s, except in the region of Zurich where there is a small negative trend. On the other hand, the model predictions match very well the spatial variability of the trends but the calculated trends are around 0.5 ppb year⁻¹ lower than those observed. This difference is similar to the background ozone increase as suggested by the long-term observations at the high Alpine station Jungfraujoch. These results support the hypothesis that the decrease in local ozone production due to emission reductions might have been partly or completely compensated by the simultaneous increase in the background ozone. In 2010, a strict application of the Gothenburg Protocol in Europe would lead to a decrease in peak ozone concentrations by about 5% in Switzerland under the meteorological conditions applied. Our calculations also indicated that emission controls only in Switzerland would not be very effective to improve the air quality in the future. The further development of the background ozone will in any case be very important for the tropospheric ozone levels.     

Voluntary information programs and environmental regulation: Evidence from ‘Spare the Air’

This paper assesses whether individuals change their transportation choices in response to ‘Spare the Air’ (STA) advisories, a public voluntary information program in the San Francisco Bay Area that elicits reductions in ozone-producing activities. Since STAs are issued when ozone levels are predicted to exceed a particular threshold, we use a regression discontinuity design to identify the effect of STAs. We also use traffic conditions in Southern California, an area without STAs, to estimate difference-in-differences models. The results suggest that STAs reduce traffic volume and slightly increase the use of public transit, supporting a potential role for voluntary information programs that directly target individuals as a means for improving local air quality.     

Turbulent air–water flows in hydraulic structures: dynamic similarity and scale effects

In hydraulic structures, free-surface aeration is commonly observed: i.e., the white waters. The air bubble entrainment may be localised (hydraulic jumps, plunging jets) or continuous along an interface (water jets, chutes). Despite recent advances, there are some basic concerns about the extrapolation of laboratory results to large size prototype structures. Herein the basic air bubble entrainment processes are reviewed and the relevant dynamic similarities are discussed. Traditionally, physical studies are conducted using a Froude similitude which implies drastically smaller laboratory Reynolds numbers than in the corresponding prototype flows. Basic dimensional analyses are developed for both singular and interfacial aeration processes. The results are discussed in the light of systematic investigations and they show that the notion of scale effects is closely linked with the selection of relevant characteristic air–water flow properties. Recent studies of local air–water flow properties highlight that turbulence levels, entrained bubble sizes and interfacial areas are improperly scaled based upon a Froude similitude even in large-size models operating with the so defined Reynolds numbers ρ _w × q _w/μ _w up to 5 E+5. In laboratory models, the dimensionless turbulence levels, air–water interfacial areas and mass transfer rates are drastically underestimated.     

Levels and congener distributions of PCDDs,PCDFs and dioxin-like PCBs in environmental and human samples: a review

The term “dioxins” is often used in a confusing way. In toxicological considerations—and also in the present report—the term is used to designate the PCDDs, the PCDFs and the coplanar (“dioxin-like”) PCBs, since these classes of compounds show the same type of toxicity. Because of the large number of congeners, relevant individual congeners are assigned with a toxic equivalency factor (TEF) that relate their toxicity to that of tetrachlorodibenzo-p-dioxin (TCDD) (2,3,7,8-TCDD) and are to be evaluated as dioxins. Each concentration of an individual congener in a mixture is multiplied with its TEF, and the resulting TCDD equivalents are added up and expressed as WHO-endorsed toxic equivalents (WHO-TEQ). Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are mainly the by-products of industrial processes (such as metallurgical processing, bleaching of paper pulp, and the manufacturing of some herbicides and pesticides) but they can also result from natural processes like volcanic eruptions and forest fires. Waste incineration, particularly if combustion is incomplete, is among the largest contributors to the release of PCDDs and PCDFs into the environment. Due to their persistence, PCDDs, PCDFs and PCBs are part of the so-called persistent organic pollutants group of compounds that also include some chlorinated pesticides. Since they have a high lipophilicity and resist transformation, they bio-accumulate in animal and human adipose tissues. Consumption of food is considered as the major source of non-occupational human exposure to PCDD/Fs with foodstuffs from animal origin accounting for more than 90% of the human body burden. With meat, dairy, and fish products being the main contributors. The aim of the present review was to summarize experimental data regarding dioxin emissions from contaminated and uncontaminated biological and environmental samples, from the available literature. The information will be presented chronologically with respect to distribution in human milk, serum; food, water, air, soils and sediments.     

反射式加热炉的清洁化工艺改造

介绍了一种新研制开发的加热炉型 ,并以生产运行的实践数据论证了其技术的先进性和效益的显著性 ,展望了其可作为清洁生产工艺设备进行推广的广阔应用前景。