Numerical Simulations on the Effect of Sea–Land Breezes on Atmospheric Haze over the Pearl River Delta Region

The atmospheric haze over the Pearl River Delta (PRD) was investigated by using the Models-3 Community Multi-scale Air Quality modeling system with meteorological fields simulated by the Fifth-generation National Center for Atmospheric Research/Penn State University Mesoscale Model (MM5) from September 26th to September 30th, 2004. The model-simulated meteorological elements and particulate matter with aerodynamic diameter less than 10 μm (PM₁₀) were compared with observations at four air quality-monitoring stations. The results showed that MM5 successfully reproduced the diurnal variations of temperature, wind speed, and wind directions at these stations. The temporal variations of the simulated values were consistent with those of the observed (such as temperature, wind speed, and wind direction). The correlation coefficient was 0.91 for temperature and 0.56 for wind speed. The modeling results show that the spatial distributions of simulated PM₁₀ were closely related to the source emissions indicating three maxima of PM₁₀ over the PRD. The sea–land breezes diurnal cycle played a significant role in the redistribution and transport of PM₁₀. Nighttime land breeze could transport PM₁₀ to the coast and the sea, while daytime sea breeze (SB) could carry the accumulated PM₁₀ offshore back to the inland cities. PM₁₀ could also be transported vertically to a height of up to about 1000 m because of strong turbulence in the SB front. Process analyses indicated that the emission sources and the vertical diffusion were the major processes to influence the concentrations of particulate matter with aerodynamic diameter less than 2.5 μm (PM_2.5).     

The Seasonal Variation of the Concentrations of Ozone, Sulfur Dioxide, and Nitrogen Oxides in Two Nigerian Cities

A combination of multivariate statistical methods including factor analysis, principal component analysis, principal component regression, and multiple linear regression (MLR) were employed to evaluate the influence of seasons on the concentrations of ozone, sulfur (IV) oxide, and oxides of nitrogen in ambient air of Nigerian cities of Lagos and Ilorin. The former city is located in the coastal area, and it is highly congested with a high intensity of marine, vehicular, and industrial activities, and the latter city is a medium size town, located in the central guinea savannah zone of Nigeria. Samples were collected using a high-volume sampler from near the ground at various sites of diverse human and industrial activities, during wet and dry seasons from 2003 to 2006. The PCA reveals three distinct groupings during the day for all data, which is a reflection of different factors contributing to the atmospheric chemistry of these cities. The predicted ozone concentration values by MLR agree fairly well with the measured data. The dependence of ozone on meteorological parameters including relative humidity, air temperature, and sun exposure and the precursor pollutants depends on weather and the anthropogenic activities. The results for the two cities indicate that reduction in the level of NO₂ is accompanied by an increase in the level of ozone, suggesting the interconversion between the two via photochemical activity.     

灰霾期间气溶胶的污染特征

从颗粒物的时空分布和浓度水平方面综述了灰霾期间气溶胶的污染特征,介绍了灰霾期间气溶胶中金属元素、水溶性离子、有机碳和元素碳的浓度特征,以及颗粒物与能见度的相关性研究进展。指出:灰霾天气多发生在冬季,且气溶胶中PM2.5占的比重大;气溶胶污染与地理环境、气候条件、经济发展水平等有密切关系;水溶性离子多集中在PM2.5中;能见度的下降与气溶胶特别是细颗粒物有很大关系。提出目前灰霾研究中主要存在3大问题:一是对灰霾期间气溶胶中含有的有机物类别及其对不同季节发生灰霾的贡献率仍需进一步研究;二是灰霾期间气溶胶中有机物的形成机理尚不明确;三是不同源排放的气溶胶对灰霾形成的贡献率有待探讨。建议系统地开展大气细颗粒物有害成分的鉴定、源排放颗粒物的物理化学特性、扩散过程中各种物质间的反应和转化等方面的研究,为大气污染防治法规的制定提供依据。     

微波消解ICP-MS法同时测定大气颗粒物中多种痕量元素

采用微波消解电感耦合等离子体质谱法同时测定大气颗粒物中13种元素,选择硝酸体系消解20 min,硝酸加入体积为8 mL。Cu、Ni、Cr、Pb、Al、Mg、Mn、Ca在0μg/L～100μg/L,Ag、Ba、Co、Cd、Sn在0μg/L～5.00μg/L范围内线性良好,除Al、Mg、Ca检出限较高外,其他10种元素的检出限为0.07 ng/m3～1.82 ng/m3(按采样体积0.688 m3、定容体积50 mL计),滤膜样品平行测定3次的RSD≤1.2%,加标回收率在92%～108%之间。     

Austal 2000应用于国内“烟塔合一”类项目大气影响评价

简述了德国"烟塔合一"类大气污染扩散模式,以及相关模式Austal 2000的应用方法,修正了气象参数以适合本地化应用。以天津某电厂为实例,将Austal 2000模式"烟塔合一"和烟囱排烟方式的计算结果进行了对比分析。结果表明,在进行本地化修改后,Austal 2000模式适用于国内有关项目大气预测评价,但从环境影响角度考虑,"烟塔合一"相对于高烟囱排放方式没有明显优势,应用时需慎重。     

Comparisons of two serious air pollution episodes in winter and summer in Beijing

Characteristics of two serious air pollution episodes(9–15 January, as the winter case; and30 June to 1 July, as the summer case), which occurred in Beijing in 2013 were investigated and compared using multi-method observations and numerical simulations. During these two air pollution episodes, PM_(2.5) concentrations varied significantly within Beijing, with PM_(2.5) concentrations in southern parts of Beijing being significantly higher than in northern areas. Typically, heavy air pollution episodes begin in the southern parts and disperse towards the northern parts of Beijing. Clearly, synoptic patterns and the stability of atmospheric circulation patterns were the main factors controlling air pollution in Beijing.During the winter case, a warm center above 900 h Pa occurred over Beijing. Meanwhile, in the summer case, although there was only a weak inversion, the convective inhibition energy was strong(over 200 J/k G). This clearly influenced the duration of the air pollution event. Except for the local accumulation and secondary atmospheric reactions in both cases, regional straw burnings contributed a lot to the PM_(2.5) concentrations in summer case.Using the CAMxmodel, we established that regional transport contributed almost 59% to the PM_(2.5) averaged concentration in Beijing in the winter case, but only 31% in the summer case. Thus, the winter case was a typical regional air pollution episode, while the summer case resulted from local accumulation straw burnings transportation and strong secondary atmospheric reactions. Given that air pollution is a regional problem in China, consistent and simultaneous implementation of regional prevention and control strategies is necessary to improve regional air quality.     

石家庄大气降尘中矿物微观结构分析

以石家庄城市为例,针对大气降尘中矿物微观结构的研究,基于扫描电子显微镜(SEM)及其图像处理技术,快速获取颗粒形态、粒度大小等微观结构信息。结果表明,从检测的样品形貌特征图像中,可以高效识别降尘中的微颗粒及其形态,获取黏土矿物微观结构和矿物颗粒成分信息,认为大气降尘样品中污染物可能源自交通、建筑、工业燃煤等。背散射图像和能谱分析系统的结合为污染物源解析提供了有利条件。     

Protocol Development for Assessing Arsenic Background Concentrations in Florida Urban Soils

Knowledge of arsenic background concentrations in urban soils is important for making remediation decisions. The soil cleanup target level (SCTL) for arsenic in Florida lies within the range of arsenic background concentrations. The residential SCTL is also near the practical quantification limits using analytical procedures. Currently no standard protocols are available for determining arsenic background concentrations in urban soils, apart from site-specific cases. Therefore, a pilot study was conducted to develop and employ appropriate protocols to determine arsenic distribution in urban soils. This involved: site selection (e.g. size and sampling frame), sample collection (e.g. sampling technique), and statistical considerations (e.g. design). Factors such as ease of sample collection and maintaining anonymity of private properties were also considered as they influence the successful implementation of the study. Forty surface soil samples each were collected from five categories in three land use classes (residential-yard and right-of-way, commercial and public land-parks and public building), digested using EPA method 3051a and analysed using graphite furnace atomic absorption spectrometry. Experiences from the pilot study (e.g. complications during sample selection, digestion, data censoring etc.) were used in the development of the final protocol to be used in determining the distribution of arsenic in urban areas.     

The Black Carbon Story: Early History and New Perspectives

A number of recent studies have suggested that black carbon (BC), the light-absorbing fraction of soot, is next to CO₂ one of the strongest contributors to the global climate change. BC heats the air, darkens the snow and ice surfaces and could contribute to the melting of Arctic ice, snowpacks, and glaciers. Although soot is the oldest known pollutant its importance in climate modification has only been recently recognized. In this article, we trace the historical developments over about three decades that changed the view of the role of BC in the environment, from a pollutant of marginal importance to one of the main climate change agents. We also discuss some of the reasons for the initial lack of interest in BC and the subsequent rigorous research activity on the role of aerosols in climate change.     

Background levels of Persistent Organic Pollutants in humans from Taiwan: Perfluorooctane sulfonate and perfluorooctanoic acid

Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) have recently received attention due to their widespread contamination of the environment. PFOS and PFOA are stable in the environment and resistant to metabolism, hydrolysis, photolysis and biodegradation. PFOS and PFOA have been found in human blood and tissue samples from both occupationally exposed workers and the general worldwide population. This study aimed to determine the background levels of PFOS and PFOA in the Taiwanese population, investigate related factors, and compare exposure in Taiwan to that in other countries. The concentration of PFOS in the 59 serum samples collected from the general population in Taiwan ranged from 3.45 to 25.65 ng mL⁻¹ (median: 8.52), and the concentration of PFOA ranged from 1.55 to 7.69 ng mL⁻¹ (median: 3.22). There was a significant positive correlation (r = 0.51; p < 0.0001) between PFOS and PFOA concentrations. Males had higher concentrations of PFOA and PFOS than females. PFOS levels in serum increased with age. This study is the first investigation to reveal the PFOS and PFOA levels of serum samples in the general population of Taiwan. The levels of PFOS and PFOA in Taiwanese serum samples were comparable with those from other countries (PFOS: 5.0–35 ng mL⁻¹, PFOA: 1.5–10 ng mL⁻¹).