垂直绿化对街道峡谷内PM2.5的影响研究

近年来细颗粒物PM_(2.5)引起的空气质量污染问题引起了社会的广泛关注,垂直绿化有较好的细颗粒物沉降效果,有望成为改善空气质量的有效办法。用ENVI-met数值模拟的方法,对不同峡谷街道宽高比、不同垂直绿化布置方式,进行多工况的比较分析,总结垂直绿化对PM_(2.5)影响的一般规律。结果表明,垂直绿化对PM_(2.5)的影响有两种,移除颗粒物和影响颗粒物分布,分别对应垂直绿化滞尘量、PM_(2.5)浓度改变量;街道宽度保持不变时,垂直绿化作为建筑外表皮能有效降低PM_(2.5)浓度;垂直绿化滞尘量随高度的升高而降低。     

首个国家公祭日及其管控期间南京市空气质量状况分析

本文对首个国家公祭日(2014年12月13日)及其管控期间南京市的空气自动监测数据进行分析,得出在此期间南京市空气质量总体南京市空气质量比2013年同期大幅改善,污染物浓度特别是颗粒物浓度下降程度明显,并从管控措施和气象条件的改善两方面阐述了空气质量总体较好的原因。     

道路绿化隔离带消减颗粒物效应及配置参数研究

交通污染已成为城市空气颗粒物污染的主要来源之一,对居民的生活、工作、出行产生了严重影响,而绿化隔离带可作为优化非机动车道和人行道空气质量的一种有效且经济地措施。基于实验测定评价道路绿化隔离带对非机动车道空气颗粒物浓度的影响,并提出分层疏透度来表征样带垂直结构特征,分析绿化隔离带配置方式对街道空气颗粒物浓度的影响。研究结果显示,绿化隔离带可较好地改善街道空气质量,对TSP和PM_(10)的消减效果较PM_(2.5)好;颗粒物的消减效果与样带的植物配置结构有紧密联系,分析结果显示颗粒物消减效率均与0～2m高度区间内的疏透度呈显著负相关。在交通流量较大的城市干道上,应该减少或者避免使用冠大荫浓的高大乔木,多配置结构紧密和叶密度较大的灌木植物。本研究结果可为城市道路绿化参数化设计和优化提供理论支撑,为改善人居生活环境作出贡献。     

大气颗粒物的源解析模型研究

大气中颗粒物的浓度在评价大气的环境质量和追溯污染源方面是很重要的参数,空气质量模型模拟系统广泛应用于对各种大气污染物在不同尺度下的不同类型污染过程进行模拟,成为大气环境研究中不可缺少的组成部分。通过对扩散模型在颗粒污染物溯源方面的原理分析以及扩散模型的优缺点分析,同时从应用广泛的受体模型中的化学质量平衡模型(CMB)和正定矩阵因子分解模型(PMF)的实现原理和这两种受体模型的对比。最后分析了多尺度空气质量模型(CMAQ)中的第三代空气质量模式Models-3,可同时模拟多种空气污染及其相互转化过程是最优的技术方案。     

地铁入口空间布局对室内空气质量的影响研究

城市地铁地处繁华地区,结构封闭,周边环境污染源较多,室内易积累污染物。本研究重点关注地铁口空间布局对室外颗粒物进入的影响,在调研中选取地铁站入口方向、顶棚形态、入口高宽比3个形态指标作为影响因子,经过实测验证CFD模型的可行性后,选择RNG k-ε模型模拟不同风速下各地铁口形态的室内污染情况。结果表明：(1)侧向比正向入口颗粒拦截率高一倍;(2)入口高宽比小于1∶1时入口宽度越大,地铁站整体空气质量越好;(3)顶棚形态对室内颗粒物的消减排列为：斜顶>平顶>无顶;(4)地铁口空间形态对不同直径的颗粒拦截效果不同。形态设计可以改善站内颗粒物进入情况,通过空气对流、回流减少室外污染物的直接灌入。     

办公室内颗粒污染物动态特性测试研究

通过测试一个典型办公室内颗粒污染物的质量浓度和粒子数浓度,分别研究了开窗和不开窗两种条件下的烟燃烧、室内人员走路日常活动、以及室外污染源作用下室内颗粒污染物的动态特性,研究结果表明,当室外污染物浓度较小时,开窗既降低了室内颗粒物浓度的增幅,又降低了室内颗粒物浓度下降到较低水平的时间。人员走路这种情况下,部分颗粒物会由于二次悬浮作用而引起室内颗粒物增长,随后又由于重力作用而发生沉降。在室外污染严重的地区,由于渗透作用,室外污染物浓度对室内颗粒物浓度影响最为显著。     

基于ENVI-met模拟的不同用地类型居住小区绿地布局对PM2.5的影响

居住区绿地作为城市绿地的主要组成肌理,对改善空气质量起着重要作用。首次将ENVI-met用于居住小区绿地布局与PM2.5的模拟,选取武汉市典型的一类、二类、三类小区,定量分析不同草地、乔木布局对PM2.5的影响。研究表明,集中型的草地布局、四周型的乔木布局能更有效降低小区PM2.5浓度;分散型的草地布局、集中型的乔木布局最不利于消减PM2.5;四周型的乔木布局对阻滞道路上PM2.5的扩散效果最佳。同种绿地布局形式下,二类小区的平均PM2.5浓度最低,三类小区最高,PM2.5空间分布在3类小区中也具有一定的差异。研究揭示了居住小区绿地布局对PM2.5的影响机制,为小区绿地的规划设计实践提供一定参考。     

电化学作用对蒙脱石软岩颗粒物沉降与体积膨胀性影响的试验研究

 研制一种电化学作用改变蒙脱石软岩颗粒物膨胀性的试验装置,在该装置上对蒸馏水、NaCl溶液和NaCl电解液浓度及电位梯度等对蒙脱石软岩颗粒物在其中的沉降与沉降稳定后的体积膨胀性的影响进行试验研究。试验结果表明：直流电场的作用可以改变蒙脱石软岩颗粒物在蒸馏水电解液中的沉降速度,但不能改变其沉降稳定后的体积膨胀性。随NaCl溶液浓度的增大,软岩颗粒物在其中的沉降速度加快,并且沉降稳定后的岩样体积膨胀率随溶液浓度的增大呈负指数规律衰减。当岩样颗粒物在NaCl溶液中沉降稳定后,加电位梯度为0.5 V/cm的电场,会使稳定后的岩样体积再次减小。在电场的持续作用下再次稳定后的岩样体积膨胀率仍随电解液浓度的增大呈负指数规律减小。电位梯度为0.5 V/cm的电场能为加速黏土矿物颗粒物的沉降和抑制其沉降稳定后的体积膨胀性的电动现象提供足够的电势差。在电位梯度为0.5 V/cm的电场作用后,再提高电位梯度,对改变岩样沉降稳定后的体积膨胀性没有明显影响。随着电解液浓度的增大,作用于岩样的电流强度增强,试验系统的温度升高。随着作用时间的延长,电解液浓度降低,电流强度呈负指数规律衰减,温度也随之降低。在直流电场作用过程中,电化学系统发生了电极和电解反应,蒙脱石软岩颗粒物的酸碱度发生了变化,在阳极区域的pH值降低,呈酸性;在阴极区域的pH值升高,呈碱性。     

园林绿地秋季温湿度与细颗粒物(PM_(2.5))浓度的关系研究——以北京玉渊潭公园为例

近年来,空气质量越来越成为社会所关注的主要环境问题之一,尤其是以PM_(2.5)为代表的空气颗粒物,对居民生活产生了巨大的影响。园林绿地是城市重要的组成部分,具有降低空气污染物等生态功能。以北京玉渊潭公园为研究地点,采用多点同步连续监测的方式,对公园内不同区域的温、湿度及细颗粒物(PM_(2.5))浓度进行监测。通过一个完整秋季的数据,分析园林绿地中温、湿度和PM_(2.5)浓度在秋季的变化情况,温、湿度和PM_(2.5)浓度之间的相关性,以及不同站点间温、湿度与PM_(2.5)浓度之间的关系。     

公园绿地和广场空气颗粒物浓度对比及影响因素研究

大气污染是中国城市环境面临的严峻问题之一,场地尺度的污染防治面临巨大压力。一些研究认为城市绿地对改善空气质量具有重要作用,然而也有部分研究提出了质疑,认为绿地植被加剧了空气污染。鉴于结论的不一致性,选择西安地区公园绿地丹枫园和紧邻的开敞广场作为研究对象,开展对比分析,采用更高的时间分辨率,对距道路不同水平距离的颗粒物浓度和气象因子进行为期一周的连续监测,分析其时空变化规律和影响因素。结果表明：（1）温度、气压、湿度和风速对PM2.5和PM10浓度均有显著影响,湿度和风速对颗粒物的影响存在阈值,湿度阈值为70%,风速阈值为1.8 m·s-1,颗粒物浓度随着湿度和风速的增大而升高,湿度和风速超过阈值时,颗粒物浓度逐渐降低,但广场风速超过阈值时,广场PM10浓度继续升高。（2）颗粒物浓度日变化呈“峰谷型”,6点至8点,19点至24点颗粒物浓度较高,样地内颗粒物浓度随水平距离增加而升高,绿地内颗粒物浓度低于广场。10点至18点颗粒物浓度较低,颗粒物浓度随距离增加而降低,绿地内颗粒物浓度高于广场。（3）对比硬质广场,绿地能有效削弱颗粒物浓度峰值和PM10浓度。结果表明绿地主要通过影响绿地风速和湿...     

A wind-tunnel study on diffusion from urban major roads

We evaluate the performance of reduced-scale wind-tunnel experiments that simulate vehicle-induced pollutant diffusion in urban roadside area. From Japanese urban areas, we selected four sites that cover a wide range of road structures, building density, and roadside features. At each site, four field stations were installed to monitor concentration of air pollutants including nitrogen oxides (NOx). In the wind-tunnel experiments, ethane was emitted from along the major roads, and its concentration was compared with the background-subtracted field values. For annual average of NOx in the year 2006, we found that an appropriately normalized concentration agreed fairly well between wind-tunnel and field measurements. The wind-tunnel concentration distribution measured at a high spatial resolution revealed that roadside features such as tall buildings, noise barriers, and trees have considerable effect on the concentration on the downwind or upwind side of the roads. The high-resolution results are expected to serve as a useful database for evaluating numerical air pollution models.     

不同生境行道树香樟生长特性及其对冰雪灾害的响应研究

随着全球气候变化加剧,各地极端气候现象频发,如何有效应对极端气候对城市绿化的影响是当前城市建设需要深入思考的问题。以2018年1月末南昌持续4天的极端冰冻灾害天气为契机,通过对典型样地的遴选和样地调查,对行道树及其生境的相互适应关系,以及其对冰冻灾害的响应机制做出分析,结果表明:1)行道树与道路宽度、株行距、路侧建筑等空间环境有密切关系,树木的生长受到道路空间形态的限制,并反映出相应的形态适应性;2)由于竞争促进作用,香樟长势背阴环境优于阳面环境;3)背阴环境中的香樟遭受冰雪灾害的损害程度较阳面严重,树冠的优势方向折枝较严重。     

植物群落特征对夏季公园林荫空间微气候的影响研究

选取福州市西湖公园林荫空间为样地,借助ENVI-met软件,引入正交试验设计,探究植物群落特征对夏季林荫空间微气候的影响.结果 表明如下几方面.1)树木叶面积指数在所有时段均对林荫空间的降温通风能力起主导作用,降湿效应在早上时段主要受乔灌草比例影响,其余时段主要受树木叶面积指数影响.2)树木叶面积指数、灌木层占比与林荫...     

乔木覆盖率及形态特征对公园夏季微气候舒适性的调节作用——以郑州市绿荫公园为例

以郑州市绿荫公园为研究对象,采用正交试验法设计试验方案,借助ENVI-met进行多因素量变模拟,探究乔木覆盖率及形态特征对公园夏季微气候舒适性的调节作用。得出以下结论。1)乔木覆盖率与热湿环境关联度大,树干高与风环境关联度大。2)各因素对公园微气候影响有时段性差异。3个乔木形态特征参数中,冠幅贡献率始终最大,中午时段高达22.5%;树干高在早上时段贡献率相对较高;叶面积指数的贡献率时段差异最小,中午时段略高;乔木覆盖率的贡献率各时段均大于3个乔木形态特征参数之和。3)乔木覆盖率85%、树干高4m、叶面积指数3.9、冠幅7m的组合方式夏季热舒适度最佳。建议城市公园在保证乔木覆盖面积的基础上,结合空间功能的时段性需求,合理选择乔木树种,有效发挥乔木对公园微气候的积极作用。     

Impact of diesel policy banning on PM levels in urban areas

Increased use of diesel engine in on‐road vehicles presents a serious health concern, particularly in traffic‐congested urban areas. Diesel exhaust contains various gaseous and particulate pollutants, which, at high concentrations, pose adverse health effects. In this respect, various policy measures are being adopted worldwide to curtail emissions from diesel engines. This paper presents an assessment of diesel engine policy banning in the Greater Beirut Area. For this purpose, particulate matter levels in the air were measured after the ban and compared with concentrations reported prior to the ban. Health‐based socio‐economic benefits associated with improvement in air quality were then estimated using the long‐term decrease of particulate matter as an indicator.     

Understanding the physical processes of pollutant build-up and wash-off on roof surfaces

Pollutants originating with roof runoff can have a significant impact on urban stormwater quality. This signifies the importance of understanding pollutant processes on roof surfaces. Additionally, knowledge of pollutant processes on roof surfaces is important as roofs are used as the primary catchment surface for domestic rainwater harvesting. In recent years, rainwater harvesting has become one of the primary sustainable water management techniques to counteract the growing demand for potable water.This paper presents the outcomes of an in-depth research study into particulate matter build-up and wash-off for roof surfaces. In this research, particulate matter was considered as the indicator pollutant where the processes related to other pollutants can be predicted based on the understanding generated for particulate matter. The study outcomes confirm that the build-up process on roof surfaces is comparatively similar to road surfaces. However, particle loads collected from roofs were significantly less compared to road surfaces and much finer in texture. Wash-off from roofs also showed significant similarities to wash-off from roads. A relatively high concentration of particulate matter was noted during the initial part of storm events. Furthermore, the amount of particulate matter remaining on the roof surfaces was significantly high for less intense rain events.     

A review on the effectiveness of street sweeping, washing and dust suppressants as urban PM control methods

Given the absence of a definitive threshold for atmospheric particulate matter (PM)-induced adverse health effects and the evidence of road traffic as a main contributor to PM-urban levels, there is a general agreement in reducing PM-associated health risks by firstly focusing on vehicle traffic sector. Beside the reduction of primary exhaust emissions, recent potential measures are challenging to reduce emissions of particulate matter from abrasion and resuspension processes given the high potential health burden of heavy metals and metalloids sourced by vehicle-wear particles (brakes, tires, rotor, discs and catalysts) and of coarse particles (PM_2.5-10).Some mitigating measures can be adopted in order to reduce road dust emissions from paved roads by removing or binding those particles already deposited and easy to be resuspended by traffic-generated turbulence. Sweeping, water flushing and use of chemical suppressants are usually more commonly employed to try to diminish emissions, but evaluating the effectiveness of preventive measures on improving air quality is a difficult task, consequently there is a general dearth of information about their effectiveness in reducing ambient PM concentrations. In particular, the scientific bibliography seems to be particularly scarce, whilst most of the information comes from local authorities committees. Consequently the existing reports are often aimed only to the municipalities and in the native language, with an objective difficulty for the international scientific community to access to them.For this review we have gathered contributions from some of major experts in this field, with the purpose of taking advantage of their background and personal awareness about any kind of related reports even not in English. Furthermore, the results we have gathered are often dissimilar, probably due to the different local conditions (weather, road pavement conditions etc.), therefore another objective of the review is to make a balance of actual knowledge and create a useful reference for future research studies and air quality management.     

Airborne particulate matter and gaseous air pollutants in residential structures in Lodi province, Italy

The province of Lodi is located in northern Italy on the Po River plain, where high background levels of air pollutants are prevalent. Lodi province is characterized by intensive agriculture, notably animal husbandry. This paper assesses indoor levels of selected airborne pollutants in 60 homes in the province, with special attention to size-fractionated particulate matter (PM). Indoor PM?.? concentrations are frequently higher than current guidelines. PM?? and nitrogen dioxide also exceed the respective guideline recommendations in some cases, noting that 24-h nitrogen dioxide levels were compared with an annual limit value. All other studied pollutant levels are below current international guidelines. Among indoor PM size fractions, PM?.? is predominant in terms of mass concentrations corresponding to 57% of PM?? in summer and 71% in winter. A strong seasonal trend is observed for all studied pollutants, with higher levels in winter corresponding to changes in ambient concentrations. The seasonal variation in PM?? is largely due to PM?.? increase from summer to winter. Summer indoor PM levels are mainly from indoor-generated particles, while particles of outdoor origin represent the main contribution to winter indoor PM levels. On average, indoor concentrations of coarse PM are mostly constituted by indoor-generated particles. PRACTICAL IMPLICATIONS: This study presents a comparison between measured indoor concentrations in the study area and indoor air quality guideline criteria. Accordingly, particulate matter (PM) and NO? are identified as key pollutants that may pose health concerns. It is also found that indoor PM in residential units is mainly constituted by particles with aerodynamic diameters <0.5 μm, especially in winter. Risk mitigation strategies should be focused on the reduction in indoor levels of NO? and ultrafine and fine particles, both infiltrated from outdoors and generated by indoor sources.     

Numerical analysis for evaluating the “Exposure Reduction Effectiveness” of room air cleaners

An “Exposure Reduction Effectiveness” index is proposed to quantify the performance of room air cleaners based on their capability of reducing occupants' exposure to pollutants of interest. The index has advantages over existing index such as CADR. It is applicable to both room average and local breathing zones, and can be used to compare air cleaning with the other two IAQ strategies: ventilation and source reduction. A computational fluid dynamics model is developed and used to assess the effectiveness of a room air cleaner for VOCs and particles of different sizes. The simulation results show: (1) species transport model and drift-flux Eulerian model can be used to predict concentration distributions of gaseous pollutants and particulate matters when there's an air cleaner operating and CFD simulation is an efficient tool to analyze personal ventilation; (2) the Exposure Reduction Effectiveness (ERE) index is effective for describing the removal effectiveness of room air cleaners in local zones as well as the room average.