基于随机森林的南京市PM2.5和O3对减排的响应

自2013年《大气污染防治行动计划》实施后,南京市大气污染有所改善,但仍面临着细颗粒物(PM_2.5)和臭氧(O₃)污染问题.为探究污染物浓度对其前体物减排的响应,获得有效的减排策略,常利用大气化学模式进行多组基于排放扰动的敏感性试验,而这需要消耗大量计算时间和计算资源.应用随机森林算法对2015年大气化学传输模式(GEOS-Chem)模拟结果进行机器学习,高效地预测了南京2019年PM_2.5浓度日均值和日最大8 h臭氧(MDA8 O₃)浓度对不同人为源排放控制情景的响应.随机森林结果表明2019年中国人为排放每减少10%,南京ρ(PM_2.5)季节平均值下降2～4μg·m^-3.当2019年中国人为源减排比例高于20%时,南京ρ(PM_2.5)年均值将低于国家二级限值(35μg·m^-3).若仅对中国地区O₃前体物氮氧化物(NO_x)和挥发性有机污染物(VOCs)同比例减排,反而...     

Measurement of air exchange rates in different indoor environments using continuous CO2 sensors

A new air exchange rate (AER) monitoring method using continuous CO₂ sensors was developed and validated through both laboratory experiments and field studies. Controlled laboratory simulation tests were conducted in a 1-m³ environmental chamber at different AERs (0.1-10.0 hr^-1). AERs were determined using the decay method based on box model assumptions. Field tests were conducted in classrooms, dormitories, meeting rooms and apartments during 2-5 weekdays using CO₂ sensors coupled with data loggers. Indoor temperature, relative humidity (RH), and CO₂ concentrations were continuously monitored while outdoor parameters combined with on-site climate conditions were recorded. Statistical results indicated that good laboratory performance was achieved: duplicate precision was within 10%, and the measured AERs were 90%-120% of the real AERs. Average AERs were 1.22, 1.37, 1.10, 1.91 and 0.73 hr^-1 in dormitories, air-conditioned classrooms, classrooms with an air circulation cooling system, reading rooms, and meeting rooms, respectively. In an elderly particulate matter exposure study, all the homes had AER values ranging from 0.29 to 3.46 hr??1 in fall, and 0.12 to 1.39 hr^-1 in winter with a median AER of 1.15.     

Air quality management in China: Issues, challenges, and options

This article analyzed the control progress and current status of air quality,identified the major air pollution issues and challenges in future,proposed the long-term air pollution control targets,and ...     

An air quality forecasting system in Beijing - Application to the study of dust storm events in China in May 2008

An air pollution forecast system, ARIA Regional, was implemented in 2007-2008 at the Beijing Municipality Environmental Monitoring Center, providing daily forecast of main pollutant concentrations. The chemistry-transport model CHIMERE was coupled with the dust emission model MB95 for restituting dust storm events in springtime so as to improve forecast results. Dust storm events were sporadic but could be extremely intense and then control air quality indexes close to the source areas but also far in the Beijing area. A dust episode having occurred at the end of May 2008 was analyzed in this article, and its impact of particulate matter on the Chinese air pollution index (API) was evaluated. Following our estimation, about 23 Tg of dust were emitted from source areas in Mongolia and in the Inner Mongolia of China, transporting towards southeast. This episode of dust storm influenced a large part of North China and East China, and also South Korea. The model result was then evaluated using satellite observations and in situ data. The simulated daily concentrations of total suspended particulate at 6:00 UTC had a similar spatial pattern with respect to OMI satellite aerosol index. Temporal evolution of dust plume was evaluated by comparing dust aerosol optical depth (AOD) calculated from the simulations with AOD derived from MODIS satellite products. Finally, the comparison of reported Chinese API in Beijing with API calculated from the simulation including dust emissions had showed the significant improvement of the model results taking into account mineral dust correctly.     

2010年广州亚运会期间灰霾天气分析

使用广州地区气象资料,重点研究了 2010 年广州亚运会期间的灰霾天气特征. 结果发现,2010 年 11 月广州出现灰霾天气 5 d,较近年平均水平明显偏少,但 2008—2010 年的污染气象条件分析表明,2010 年的扩散条件较 2008 和 2009 年均较差,说明 2010 年广州亚运会前期的各项减排措施取得了明显成效. 作为对照,自 20 世纪 80 年代初开始,广州地区的能见度急剧恶化并导致灰霾天数增加,每年 10 月至次年 4 月的旱季灰霾天数较多,改革开放以来,每年 11 月份的灰霾天气大幅增加,并于 1994 和1999 年分别出现了最多的17 d. 2000 年以后,11 月份灰霾天气最多为 12 d,出现在 2005 年; 最少为 3 d,分别出现在 2002 和 2003 年. 广州市空气质量逐年恶化的趋势不容乐观,珠江三角洲复合型新型空气污染日趋严重的态势非常严峻; 且区域性特征明显,治理难度加大; 广州周边的佛山、清远、东莞、江门的灰霾天气都比广州多,对广州治理灰霾天气形成了压力. 因而 2010 年 11 月灰霾天气的明显减少,更说明区域联动、机动车单双号限行、重点工业污染源调控、严控垃圾秸秆焚烧等减排措施效果明显.     

燃煤电厂排放细颗粒物的水溶性无机离子特征综述

当前我国面临严重的大气细颗粒物(PM2.5)污染,燃煤电厂是大气中PM2.5的重要来源之一.为了实现国家"十一五"和"十二五"规划对二氧化硫(SO2)和氮氧化物(NOx)的总量减排目标,燃煤电厂大规模安装烟气脱硫和脱硝设施,这虽然减少了气态污染物转化生成的二次PM2.5,但另一方面也会对烟气中PM2.5的物理化学特征产生影响,有可能增加一次PM2.5的排放.本文综述了燃煤电厂排放PM2.5及其水溶性离子的粒径分布特征,重点介绍了脱硫和脱硝这两种烟气处理设施对燃煤电厂排放PM2.5的影响原理及相关研究结果,特别是对细颗粒物中水溶性离子(如SO2-4、Ca2+和NH+4)的影响.在目前我国PM2.5污染十分严重和燃煤电厂大量安装脱硫和脱硝装置的背景下,定量研究脱硫和脱硝对PM2.5排放特征的影响具有十分重要的意义.     

利用SPAMS研究石家庄市冬季连续灰霾天气的污染特征及成因

2014年11月18~26日石家庄市发生了连续的灰霾天气.利用位于石家庄市大气自动监测站(20 m)的单颗粒气溶胶质谱仪(SPAMS)分析了细颗粒物的化学组成,根据石家庄市大气污染物排放源谱库对主要成分进行了来源解析,并结合颗粒物质量浓度和气象条件研究了该地区冬季灰霾天气成因.结果表明,石家庄市大气细颗粒物来源分为7类,各源示踪离子:燃煤源为Al,工业源为OC、Fe、Pb,机动车尾气源为EC,扬尘源为Al、Ca、Si,生物质燃烧源为K和左旋葡聚糖,纯二次无机源为SO-4、NO-2和NO-3,餐饮源为HOC.灰霾期间大气中主要含有OC、HOC、EC、HEC、ECOC、富钾颗粒、矿物质和重金属等8类颗粒,其中OC和ECOC颗粒最多,分别占到总数的50%和20%以上,OC颗粒主要来自燃煤和工业工艺,ECOC颗粒主要来自燃煤和机动车尾气排放.灰霾发生时含有NH+4、SO-4、NO-2和NO-3等二次离子的颗粒物占比升高,其中含NH+4颗粒增幅最大;EC、OC与NO-3、SO-4、NH+4在灰霾天气下的混合程度均比干净天气高,其中与NH+4的混合程度加剧最为明显.冬季采暖期煤炭的大量燃烧、医化行业工艺过程及机动车尾气等污染源排放的一次气态污染物(SO2、NOx、NH3、VOCs)和一次颗粒物在静稳天气中难以扩散而迅速累积,气态污染物发生二次转化形成硝酸铵、硫酸铵,而颗粒物之间通过碰撞形成二次颗粒物并发生不同程度的混合,从而导致大气能见度下降,以上是石家庄市冬季灰霾形成的主要原因.     

兰州市大气颗粒物多环芳烃的恒能量同步荧光光谱特征研究

通过传统单波长激发/发射荧光光谱法与恒能量同步荧光光谱法进行对比,对大气颗粒物中多环芳烃(PAHs)进行了定性定量分析,采用恒能量同步荧光光谱法在不同能量差下建立了15种典型PAHs成分的恒能量同步荧光法的标准谱库.在各PAHs在最佳能量差下进行定量分析,结果表明,除苊荧光信号响应较差外,其余PAHs的LOD和LOQ分别为0.0580～3.18、0.232～12.7 ng·mL~(-1).15种PAHs的空白和一定浓度下的加标回收率范围在82.8%～120.0%,相对标准偏差范围在0.51%～5.87%之间,以恒能量同步荧光光谱进行了兰州地区大气颗粒物中15种PAHs分布特征分析.     

四川省典型工业行业PM2.5成分谱分析

利用荷电低压颗粒物撞击器(ELPI+)对四川省水泥行业、玻璃行业、陶瓷行业、砖瓦行业、燃煤锅炉、生物质锅炉、电厂、钢铁行业等典型行业开展排放特征测试,通过组分分析,获取各行业PM_(2.5)成分特征谱.结果表明:①水泥、玻璃、陶瓷、砖瓦等建材行业均以Si、Ca、Mg等元素为主要排放组分,双碱法脱硫SO_4~(2-)排放占比高于其他脱硫工艺;②电厂PM_(2.5)中SO_4~(2-)、Ca~(2+)、NH_4~+、Mg和Si为特征组分;燃煤锅炉中OC、Al、Si和Ca等为特征组分;③OC和EC是生物质锅炉PM_(2.5)主要排放组分,成型生物质燃料锅炉中K排放占比也较高,非成型生物质燃料锅炉中Cl~-排放占比为所有行业中最高;④钢铁行业中Ca含量最高,为18. 11%,其次为SO_4~(2-)、Na~+和Fe.     

青藏高原中汞的分布特征及影响因素——以典型海洋性冰川小流域为例

本研究以青藏高原典型海洋性冰川的雪冰-径流水为研究对象,分析讨论了雪冰-径流水中汞浓度变化趋势及控制因素.结果表明,贡嘎山冰川中雪、冰样品的THg浓度略高于全球背景值,而明永冰川以及米堆冰川的雪、冰、水样品均处于全球背景水平.3个冰川所有雪样、冰样、水样的THg浓度平均值分别为（4.78±5.99）ng/L、（1.72 ±1.15）ng/L、（1.31±0.91）ng/L.不同的环境介质中THg浓度变化总体表现为：雪 > 冰 > 水,其主要受颗粒汞沉淀作用及气态单质Hg挥发作用的控制.贡嘎山的径流水中THg浓度表现为六月最高（7.48±2.22）ng/L,十一月最低（1.39 ±0.27）ng/L.所有雪冰-径流水体系中HgP与THg存在极显著的正相关关系,雪中HgP/THg最高,其次为冰,最低为径流水.贡嘎山径流水中的HgP/THg及月均THg输出变化趋势受径流量和降雨量的影响.主成分分析表明了本研究区域雪冰中THg浓度主要受大气颗粒物沉降及季风传输的影响.此外,相比于其他2个冰川,贡嘎山冰川由于更加靠近人类活动密集区域,更易受到人类活动的影响.