Gas-phase and aerosol chemistry interactions in South Europe and the Mediterranean region

The atmospheric chemical composition is affected by the interaction mechanisms among gases and particulate matter through a wide range of chemical reactions that can occur with the aid of particulate matter (e.g. particles act as reacting or absorbing surfaces) or be influenced by the presence of particulate matter in the atmosphere (photochemical reactions). Physical and chemical processes are also bonded in an interactive way that often leads to the influence of the radiation budget, cloud physics and the warming or cooling of the lower atmospheric levels. The Euro-Mediterranean region is a key-sensitive area due to the unique climatic and air quality characteristics associated with the regional climatic patterns, geomorphology (land and water contrast) and coexistence of pollutants from different origin. Focusing on this region, the gas-aerosol interactions are studied using state-of-the-art atmospheric and chemical transport modeling tools following the necessary development in the chemical transport model CAMx. Sensitivity and large-scale simulations have shown significant responses of the modeling system to the inclusion of natural species emissions, the direct shading effect of dust particles on photochemical processes and the formation of new types of aerosols through heterogeneous uptake of gases on dust particles. Including such interactions in the chemical transport model often led to the improvement of the model performance compared with available measurements in the region.     

Size distribution of polycyclic aromatic hydrocarbons in a roadway tunnel in Lisbon, Portugal

Atmospheric aerosols of four aerodynamic size ranges were collected using high volume cascade impactors in an extremely busy roadway tunnel in Lisbon (Portugal). Dust deposited on the tunnel walls and guardrails was also collected. Average particle mass concentrations in the tunnel atmosphere were more than 30 times higher than in the outside urban background air, revealing its origins almost exclusively from fresh vehicle emissions. Most of the aerosol mass was concentrated in submicrometer fractions (65%), and polycyclic aromatic hydrocarbons (PAH) were even more concentrated in the finer particles with an average of 84% of total PAH present in sizes smaller than 0.49 μm. The most abundant PAH were methylated phenanthrenes, fluoranthene and pyrene. About 46% of the total PAH mass was attributed to lower molecular weight compounds (two and three rings), suggesting a strong influence of diesel vehicle emissions on the production of local particulate PAH. The application of diagnostic ratios confirmed the relevance of this source of PAH in the tunnel ambient air. Deposited dust presented PAH profiles similar to the coarser aerosol size range, in agreement with the predominant origin of coarser aerosol particles from soil dust resuspension and vehicle wear products.     

Temporal changes of 7Be, 137Cs and 210Pb activity concentrations in surface air at Monaco and their correlation with meteorological parameters

Results of analysis of ⁷Be, ¹³⁷Cs and ²¹⁰Pb on aerosol filters carried out from 1998 to 2010 in Monaco show that a weak correlation between activity concentrations of these radionuclides in the atmosphere and meteorological parameters has been found for ⁷Be and temperature (r = 0.50), ²¹⁰Pb and temperature and humidity (r = 0.43 and 0.41, respectively), and ¹³⁷Cs and precipitation (r = 0.51). The minimum and maximum ⁷Be activity concentrations were observed during 2000 and 2009, corresponding with the maximum and minimum solar activity, respectively. The maximum ¹³⁷Cs activity concentration found in May-June 1998 was due to the accident at Algeciras in Spain. The deposition velocities of ⁷Be, ¹³⁷Cs and ²¹⁰Pb depended on the precipitation rate, and attained maximum values during dry seasons. The investigated radionuclides may be used as atmospheric tracers, especially in long-term periods.     

Simulation of aerosol direct radiative forcing with RAMS-CMAQ in East Asia

The air quality modeling system RAMS-CMAQ is developed to assess aerosol direct radiative forcing by linking simulated meteorological parameters and aerosol mass concentration with the aerosol optical properties/radiative transfer module in this study. The module is capable of accounting for important factors that affect aerosol optical properties and radiative effect, such as incident wave length, aerosol size distribution, water uptake, and internal mixture. Subsequently, the modeling system is applied to simulate the temporal and spatial variations in mass burden, optical properties, and direct radiative forcing of diverse aerosols, including sulfate, nitrate, ammonium, black carbon, organic carbon, dust, and sea salt over East Asia throughout 2005. Model performance is fully evaluated using various observational data, including satellite monitoring of MODIS and surface measurements of EANET (Acid Deposition Monitoring Network), AERONET (Aerosol Robotic Network), and CSHNET (Chinese Sun Hazemeter Network). The correlation coefficients of the comparisons of daily average mass concentrations of sulfate, PM2.5, and PM10 between simulations and EANET measurements are 0.70, 0.61, and 0.64, respectively. It is also determined that the modeled aerosol optical depth (AOD) is in congruence with the observed results from the AERONET, the CSHNET, and the MODIS. The model results suggest that the high AOD values ranging from 0.8 to 1.2 are mainly distributed over the Sichuan Basin as well as over central and southeastern China, in East Asia. The aerosol direct radiative forcing patterns generally followed the AOD patterns. The strongest forcing effect ranging from −12 to −8 W m⁻² was mainly distributed over the Sichuan Basin and the eastern China’s coastal regions in the all-sky case at TOA, and the forcing effect ranging from −8 to −4 W m⁻² could be found over entire eastern China, Korea, Japan, East China Sea, and the sea areas of Japan     

Studies on atmospheric degradation of diazinon in the EUPHORE simulation chamber

The gas phase atmospheric degradation of diazinon has been investigated at the large outdoor European Photoreactor (EUPHORE) in Valencia, Spain. The rate constant for reaction of diazinon with OH radicals was measured using a conventional relative rate method with di-n-buthylether as reference compound being k = (3.5 ± 1.2) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ at 302 ± 10 K and atmospheric pressure. The available evidence indicates that tropospheric degradation of diazinon is mainly controlled by reaction with OH radicals, and that the tropospheric lifetime with respect to the OH reaction is estimated to be around 4 h whereas its lifetime with respect to the photolysis is higher than 1 d under our conditions. Significant aerosol formation was observed following the reaction of diazinon with OH radicals, and the main carbon-containing products detected in the particle phase were hydroxydiazinon, hydroxydiazoxon and 2-isopropyl-6-methyl-pyrimidinyl-4-ol.     

Aerosols near by a coal fired thermal power plant: Chemical composition and toxic evaluation

Industrial processes discharge fine particulates containing organic as well as inorganic compounds into the atmosphere which are known to induce damage to cell and DNA, both in vitro and in vivo. Source and area specific studies with respect to the chemical composition, size and shape of the particles, and toxicity evaluations are very much limited. This study aims to investigate the trace elements associated with the aerosol particles distributed near to a coal burning thermal power plant and to evaluate their toxicity through Comet assay. PM₁₀ (particles determined by mass passing an inlet with a 50% cut-off efficiency having a 10-μm aerodynamic diameter) samples were collected using respirable dust samplers. Twelve elements (Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb, Se, Hg, and As) were analyzed using ICP-AES. Comet assay was done with the extracts of aerosols in phosphate buffered saline (PBS). Results show that Fe and Zn were found to be the predominant elements along with traces of other analyzed elements. Spherical shaped ultrafine particles of <1 μm aerodynamic diameter were detected through scanning electron microscope. PM₁₀ particles near to the coal burning power plant produced comets indicating their potential to induce DNA damage. DNA damage property is found to be depending upon the chemical characteristics of the components associated with the particles besides the physical properties such as size and shape.     

Atmospheric heavy metal deposition accumulated in rural forest soils of southern Scandinavia

Thirty-three years of measurements of atmospheric heavy metal (HM) deposition (bulk precipitation) in Denmark combined with European emission inventories form the basis for calculating a 50-year accumulated atmospheric input to a remote forest plantation on the island of Laesoe. Soil samples taken in two depths, 0-10cm and 10-20cm, at eight forest sites at the island were used to determine the increase in HM content in the eolian deposited top soils of the plantation. Concentrations of lead (Pb), cadmium (Cd), copper (Cu), zinc (Zn), vanadium (V), nickel (Ni) and arsenic (As) were determined in atmospheric deposition and in soils. The accumulated atmospheric deposition is of the same magnitude as the increase of these metals in the top soil.     

粤北韶关市冬季大气颗粒物中多环芳烃的粒径分布特征

2012年12月4日—11日,使用微孔均匀撞击式采样器(MOUDI)连续7 d采集广东省韶关市3个环境空气监测点气溶胶样品,采用GC/MS测定包括美国国家环保局(USEPA)优控多环芳烃(Σ16PAHs)在内的17种PAHs的浓度水平,并分析Σ16PAHs的粒径分布特征和来源。结果表明:韶关市冬季气溶胶颗粒中Σ16PAHs的质量浓度为17.29 ng/m3~23.97 ng/m3;Σ16PAHs集中在1.0μm~3.2μm的积聚态和粗颗粒中,呈单峰分布特征;比值参数分析显示,韶关市大气颗粒物中PAHs主要来自燃煤和汽车尾气的排放。     

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。     

The effect of air mass origin on the ambient concentrations of Be and Pb in Islamabad, Pakistan

Concentration of radionuclides ²¹⁰Pb and ⁷Be, having half lives of 22.3 years and 53.29 days, respectively, in the surface air samples of Islamabad (33.38° N, 73.10° E and Altitude ∼536 m asl.) are measured. The non-destructive technique of gamma-spectrometry, with a high purity germanium HPGe detector, was employed for the analysis of all samples. The annual average concentrations of ²¹⁰Pb and ⁷Be in the surface air samples were determined as 0.284 ± 0.15 and 3.171 ± 1.14 mBq m⁻³, respectively. Our results have shown a seasonal variation of the concentration of ⁷Be in air samples with high values for the spring season. High concentrations for ²¹⁰Pb are obtained when air masses originate from plain areas of Pothohar region, located in the South-West, West and North West of Islamabad. Our values of concentrations show a nice agreement with the relevant reported results.