Effects of building aspect ratio, diurnal heating scenario, and wind speed on reactive pollutant dispersion in urban street canyons

A photochemistry coupled computational fluid dynamics (CFD) based numerical model has been developed to model the reactive pollutant dispersion within urban street canyons, particularly integrating the interrelationship among diurnal heating scenario (solar radiation affections in nighttime, daytime, and sun-rise/set), wind speed, building aspect ratio (building-height-to-street-width), and dispersion of reactive gases, specifically nitric oxide (NO), nitrogen dioxide (NO₂) and ozone (O₃) such that a higher standard of air quality in metropolitan cities can be achieved. Validation has been done with both experimental and numerical results on flow and temperature fields in a street canyon with bottom heating, which justifies the accuracy of the current model. The model was applied to idealized street canyons of different aspect ratios from 0.5 to 8 with two different ambient wind speeds under different diurnal heating scenarios to estimate the influences of different aforementioned parameters on the chemical evolution of NO, NO₂ and O₃. Detailed analyses of vertical profiles of pollutant concentrations showed that different diurnal heating scenarios could substantially affect the reactive gases exchange between the street canyon and air aloft, followed by respective dispersion and reaction. Higher building aspect ratio and stronger ambient wind speed were revealed to be, in general, responsible for enhanced entrainment of O₃ concentrations into the street canyons along windward walls under all diurnal heating scenarios. Comparatively, particular attention can be paid on the windward wall heating and nighttime uniform surface heating scenarios.     

环境监测事业发展方向探讨

通过分析,认为今后我国环境监测事业的主要发展方向将是有机污染物水质监测、农村环境监测和生态环境监测,并探讨了主要监测内容。     

岩溶地区持久性有机物的研究现状

近年来,岩溶地区不同环境介质中持久性有机污染物(POPs)的研究已经成为国际上该领域的热点问题。本文对POPs在岩溶地区水环境、土壤、大气和生物中的残留状况、分布特征、影响因素、迁移机制和可能来源等方面的研究现状进行了综述,结果显示岩溶地区已普遍检测出POPs,部分地区环境介质中POPs的浓度有显著降低的趋势;同时讨论了目前国内外岩溶地区POPs研究中存在的问题,并提出该研究未来可能的发展趋势。     

风险污染物短期高剂量暴露下的生态风险评估方法

水污染事故的短期高剂量暴露造成的急性生态危害及水生生物安全问题成为人们研究的重点,但我国以往的水污染事故,多采用地表水环境质量标准和生活饮用水卫生标准来判断水体是否安全,缺乏对水生生物保护的安全效应阈值或风险值.国外在水生生物保护方面,虽然限定了一些风险污染物对水生生物的安全效应阈值或称为无效应阈值或风险值,但其无效应阈值的计算是基于长期暴露下的慢性毒性值,其生态风险值也是基于长期暴露下的风险,缺少对水污染事件短期高剂量暴露下化学品的阈值限定及风险评估.本研究结合常规生态风险评价的理念及美国EPA短期暴露情况下保护水生生物基准值的制定方法,探讨了水污染事件的短期高剂量暴露情况下风险污染物的生态风险评价及生态效应阈值的计算方法,并进行了实例应用,同时对建立我国水污染事故生态风险评估方法体系提出了建议.     

紫色土对硫丹的吸附与解吸特征

为揭示硫丹在紫色土中的残留过程、保护土壤生态环境,采用静态吸附和解吸实验,研究了紫色土对硫丹的吸附与解吸特征,考察了温度、吸附剂用量和吸附液初始p H等因素对吸附量的影响.结果表明紫色土对硫丹的吸附动力学过程可以用二级动力学方程很好地描述,获得α-,β-硫丹的初始吸附速率常数分别为0.157 mg·(g·min)-1和0.115 mg·(g·min)-1;吸附热力学过程可以用Langmuir等温吸附模型很好地描述,获得α-,β-硫丹的最大吸附量分别为0.257 mg·g-1和0.155mg·g-1,紫色土吸附硫丹是放热的物理化学过程,但以物理吸附为主.在本研究所设条件下,吸附液初始p H对吸附量的影响较大,温度和吸附剂用量的影响相对较小.解吸实验发现,紫色土吸附的α-,β-硫丹分别在6和4 h时达到最大解吸量(0.029mg·g-1和0.017 mg·g-1),分别占最大吸附量的10.5%和16.1%.     

不同水期鄱阳湖主要污染物河流入湖通量研究

通过同步监测2010年-2013年入湖监测断面水质和水量,分别计算了丰水期、平水期和枯水期以及全年入湖污染物通量.结果表明,2010年-2013年,入湖10个断面水质达标率在80％～100％之间,化学需氧量均是进入鄱阳湖的主要污染物.各污染物主要通过赣江主支、赣江中支、赣江南支、赣江北支、信江西支和饶河6条河流进入鄱阳湖;氨氮浓度年均值与水量相关性均呈负相关,而化学需氧量、总磷和总氮浓度年均值与水量无明显相关性.     

生产过程中抗生素与抗药基因的排放特征、环境行为及控制

世界卫生组织在2000年的报告中将抗生素抗性列为本世纪人类在健康领域面临的最大挑战之一,有关抗药基因传播机制与控制技术的研究已经成为国际环境科学领域的一个前沿问题.本文以生产量大、使用历史长的几种发酵类和化学合成类生素为对象,以典型城市污水厂为对照系统,全面评估抗生素生产及废水处理过程中抗生素与抗药基因的排放特征;把传统的筛选培养方法与高通量测序技术及生物信息学手段有机结合,深入研究抗生素胁迫下整合子对抗性基因的重组作用及质粒介导的结合转移作用,以揭示抗药基因在抗生素压力驱动下主要的水平转移机制;构建多通道生物膜流动暴露系统进行抗生素最小选择浓度评价;研究针对抗生素生产全过程的抗生素及抗药基因控制多级屏障技术,为抗药基因的污染控制与管理提供全面系统的科学基础.     

铁岭市线源车流量调查及污染物排放量的估算

通过对辽宁省铁岭市主要交通干线车流量的调查，估算出不同干线污染物的排放量，借以掌握线源污染物排放量，为环境管理提供依据。     

Improving the prediction of air pollution peak episodes generated by urban transport networks

This paper illustrates the early results of ongoing research developing novel methods to analyse and simulate the relationship between trasport-related air pollutant concentrations and easily accessible explanatory variables. The final scope is to integrate the new models in traditional traffic management support systems for a sustainable mobility of road vehicles in urban areas.This first stage concerns the relationship between the hourly mean concentration of nitrogen dioxide (NO₂) and explanatory factors reflecting the NO₂ mean level one hour back, along with traffic and weather conditions. Particular attention is given to the prediction of pollution peaks, defined as exceedances of normative concentration limits. Two model frameworks are explored: the Artificial Neural Network approach and the ARIMAX model. Furthermore, the benefit of a synergic use of both models for air quality forecasting is investigated.The analysis of findings points out that the prediction of extreme concentrations is best performed by integrating the two models into an ensemble. The neural network is outperformed by the ARIMAX model in foreseeing peaks, but gives a more realistic representation of the concentration's dependency upon wind characteristics. So, the Neural Network can be exploited to highlight the involved functional forms and improve the ARIMAX model specification. In the end, the study shows that the ability to forecast exceedances of legal pollution limits can be enhanced by requiring traffic management actions when the predicted concentration exceeds a lower threshold than the normative one.     

火葬场场所PM2.5和VOCs排放特征及控制对策分析

火葬场遗体火化和祭品焚烧过程中会产生有害大气污染物,导致场所内PM_(2.5)和VOCs排放浓度较高,进而影响周边大气环境质量和人体健康.为探究火葬场场所PM_(2.5)和VOCs浓度水平及其化学组分特征,对国内11家火葬场场所的PM_(2.5)进行样品采集和监测,分析其浓度水平及组分,并对火化车间VOCs进行采样和分析,从而识别了火葬场场所PM_(2.5)和VOCs及其化学组分的排放特征,在此基础上提出相应的控制对策.结果表明:由于焚烧设备密闭性较差及污染控制程度低且废气低空排放,导致火葬场场所PM_(2.5)浓度较高,火化车间PM_(2.5)的平均排放浓度可达670μg·m~(-3),厂界PM_(2.5)的平均排放浓度为305μg·m~(-3),远高于环境空气浓度水平;火葬场场所PM_(2.5)化学组分中有机物占比较高,火化车间VOCs的主要化学组分为烯烃、烷烃、苯及苯系物.为降低火葬场场所的污染浓度,应加强焚烧设备的运行和维护,减少无组织排放,遗体火化机和祭品焚烧炉应安装高效的烟气净化装置,提升污染物的去除效率,保护周边环境和人体健康.