Atmospheric Chemistry

Observations of the tropical atmosphere are fundamental to the understanding of global changes in air quality, atmospheric oxidation capacity and climate, yet the tropics are under-populated with long-term measurements. The first three years (October 2006–September 2009) of meteorological, trace gas and particulate data from the global WMO/Global Atmospheric Watch (GAW) Cape Verde Atmospheric Observatory Humberto Duarte Fonseca (CVAO; 16° 51′ N, 24° 52′ W) are presented, along with a characterisation of the origin and pathways of air masses arriving at the station using the NAME dispersion model and simulations of dust deposition using the COSMO-MUSCAT dust model. The observations show a strong influence from Saharan dust in winter with a maximum in super-micron aerosol and particulate iron and aluminium. The dust model results match the magnitude and daily variations of dust events, but in the region of the CVAO underestimate the measured aerosol optical thickness (AOT) because of contributions from other aerosol. The NAME model also captured the dust events, giving confidence in its ability to correctly identify air mass origins and pathways in this region. Dissolution experiments on collected dust samples showed a strong correlation between soluble Fe and Al and measured solubilities were lower at high atmospheric dust concentrations. Fine mode aerosol at the CVAO contains a significant fraction of non-sea salt components including dicarboxylic acids, methanesulfonic acid and aliphatic amines, all believed to be of oceanic origin. A marine influence is also apparent in the year-round presence of iodine and bromine monoxide (IO and BrO), with IO suggested to be confined mainly to the surface few hundred metres but BrO well mixed in the boundary layer. Enhanced CO2 and CH4 and depleted oxygen concentrations are markers for air-sea exchange over the nearby northwest African coastal upwelling area. Long-range transport results in generally higher levels of O3 and anthropogenic non-methane hydrocarbons (NMHC) in air originating from North America. Ozone/CO ratios were highest (up to 0.42) in relatively fresh European air masses. In air heavily influenced by Saharan dust the O3/CO ratio was as low as 0.13, possibly indicating O3 uptake to dust. Nitrogen oxides (NOx and NOy) show generally higher concentrations in winter when air mass origins are predominantly from Africa. High photochemical activity at the site is shown by maximum spring/summer concentrations of OH and HO2 of 9 × 106 molecule cm−3 and 6 × 108 molecule cm−3, respectively. After the primary photolysis source, the most important controls on the HOx budget in this region are IO and BrO chemistry, the abundance of HCHO, and uptake of HOx to aerosol.

Atmospheric transport models are used in studies of atmospheric chemistry as well as aerobiology. Atmospheric transport models in general needs accurate emissions inventories, which includes biogenic emissions such as Volatile Organic Compounds (VOCs) and pollen. Trees are important VOC and pollen sources and a needed requirement is specie distribution which takes into account important species such as Betula and Alnus. We present here a detailed tree species inventory covering Europe, parts of Africa and parts of Asia.

Modified Bowen ratio and aerodynamic profile techniques based on the constant flux approach were utilized to derive the deposition fluxes and deposition velocities (vd) of gaseous nitric acid from measurements made during two joint field experiments over low vegetation (grassland, LOVENOX, Halvergate, UK, September 1989) and over a wheat canopy (ecosystem wheat, Manndorf, Germany, July 1990). Both micrometeorological methods are discussed in more detail and in context with the flux-resistance analogy to provide a complete conceptual evaluation guide for HNO3 dry deposition analysis. Daytime dry deposition of nitric acid was found to be fast with an average vd of 2.2 ± 1.2 cm s-1 and a range of 0.6 to 5.0 cm s-1. The derived deposition velocities are in broad agreement with estimates of other authors. The data have also been used to check sublayer Stanton numbers which are of basic importance in determining the viscous sublayer resistance yet not well quantified.

Hydroxyacetone (CH 3 C(O)CH 2 OH) is observed as a stable end product from reactions of the (CH 3) 2 COO Criegee intermediate, acetone oxide, in a flow tube coupled with multi-plexed photoionization mass spectrometer detection. In the experiment, the isomers at m/z = 74 are distinguished by their different photoionization spectra and reaction times. Hydroxy-acetone is observed as a persistent signal at longer reaction times at a higher photoionization threshold of ca. 9.7 eV than Criegee intermediate and definitively identified by comparison with the known photoionization spectrum. Complementary electronic structure calculations reveal multiple possible reaction pathways for hydroxyacetone formation, including unimolecular isomer-ization via hydrogen atom transfer and −OH group migration as well as self-reaction of Criegee intermediates. Varying the concentration of Criegee intermediates suggests contributions from both unimolecular and self-reaction pathways to hydroxyacetone. The hydroxyacetone end product can provide an effective, stable marker for the production of transient Criegee intermediates in future studies of alkene ozonolysis.

Two important festival events were selected to assess their impacts on atmospheric chemistry by understanding settling velocity and emission time of aerosols. Using high volume sampler, aerosols were collected in a sequential manner to understand settling velocity and emission time of aerosols on a particular day. Composition and total suspended particulate load of the aerosols collected during the festivals were used as markers for strengthening the assessment. Terminal settling velocity of the aerosols were calculated using morphological and elemental compositional data, obtained from scanning electron microcopy (SEM) and energy dispersive X-ray (EDX) study. Aerosol load, black carbon, aromatic carbon and terminal velocity calculations were correlated to obtain conclusion that aerosols collected on the festival day might have been emitted prior to the festival. Settling time of aerosols collected on 17th and 19th October’09 during Diwali were found to be 36.5 (1.5 days) and 12.8 h, respectively. Carbon concentration estimated using EDX was found to be almost double in the sample collected after 2 days of the festival event. This strengthens our inference of time calculation where carbon with high concentration of load must have settled approximately after two days of the event. Settling time of aerosols collected on Holi morning and afternoon was found to be 1.7 and 24.8 h, respectively. Further, because of the small distance of 5.4 km between the meteorological station and sampling site, observed TSP values were compared with theoretical load values, calculated by using visibility values taken from the meteorological data. And it was found that both experimental and calculated values are close to each other about 50% of the times, which proves the assumption that experimental and meteorological data are comparable.► Concept of setting velocity was used to assess impact of festival events on the atmosphere chemistry. ► SEM-EDX analysis was used to determine terminal setting velocity. ► Correlation between BC, AOC and aerosol load was used to determine the settling time of the aerosols. ► Role of morphology of aerosols in altering the atmospheric chemistry was also highlighted in the study.

Open biomass burning in Peninsula Malaysia, Sumatra, and parts of the Indochinese region is a major source of transboundary haze pollution in the Southeast Asia. To study the influence of haze on rainwater chemistry, a short-term investigation was carried out during the occurrence of a severe haze episode from March to April 2014. Rainwater samples were collected after a prolonged drought and analyzed for heavy metals and major ion concentrations using inductively coupled plasma mass spectroscopy (ICP-MS) and ion chromatography (IC), respectively. The chemical composition and morphology of the solid particulates suspended in rainwater were examined using a scanning electron microscope coupled with energy-dispersive X-ray spec-troscopy (SEM-EDS). The dataset was further interpreted using enrichment factors (EF), statistical analysis, and a back trajectory (BT) model to find the possible sources of the particulates and pollutants. The results show a drop in rainwater pH from near neutral (pH 6.54) to acidic (<pH 4.00) during the haze to non-haze transitional period, suggesting that the deposition rate of sulfate and nitrate in the atmosphere via the precipitation process was relatively lower compared to the mineral components. Zinc, nitrate, and calcium, which were the predominant elements in the first rainwater samples. Besides, the results of the SEM-EDS indicated that the zinc was possibly originated from anthropogenic activities which are consistent with the results obtained from EF. The BT model showed that pollutants transported from the mainland of Indo-China and the marine region in the South China Sea

The pK 1* and pK 2* of H2SO3 have been determined in NaCl solutions as a function of ionic strength (0.1 to 6 m) and temperature (5 and 25 °C). The extrapolated values in water were found to be in good agreement with literature data. The experimental results have been used to determine the Pitzer interaction parameters for SO2, HSO 3-and SO 3-in NaCl solutions. The resultant parameters for NaHSO3 and Na2SO3 were found to be in reasonable agreement with the values for NaHSO4 and Na2SO4. It, thus, seems reasonable to assume that the interactions of Mg2+ and Ca2+ with HSO 3-and SO 3-can be estimated from the values with HSO 4-and SO 4-until experimental values are available. Measurements of pK 1* and pK 2* in artificial seawater were found to be in good agreement with the calculated values using the derived Pitzer parameters. It is, thus, possible to make reasonable estimates of the activity coefficients of HSO 3-and SO 3-ions and pK 1* and pK 2* for the ionization of H2SO3 in marine aerosols.

This article presents a mini review on various applications of zeolites as a promising low cost microporous material in countless fields. Zeolites are hydrated aluminosilicates with full cross-linked open framework structures made up of corner sharing SiO4 and AlO4 tetrahedra and they belong to the family of microporous solids known as molecular sieves. However, currently, zeolite structure does not necessarily have to be composed of SiO4 and AlO4 tetrahedra, as numerous elements from the periodic table can now be an integral part of zeolite structural framework. Zeolites are formed in nature via volcanic action but can as well be synthesized or manufactured. The use of natural zeolites particularly for environmental applications in various fields has gained long standing interest in the science community because of their significant properties and global occurrence. Therefore, this mini review focus on the occurrence of zeolites and its various application in industries and medical field which will help future researchers to gain insight on next line of putative research avenues in application of zeolites.

Atmospheric chemistry is an important discipline for understanding air pollution and its impacts. This mini-review gives a brief history of air pollution and presents an overview of some of the basic photochemistry involved in the production of ozone and other oxidants in the atmosphere. Urban air quality issues are reviewed with a specific focus on ozone and other oxidants, primary and secondary aerosols, alternative fuels, and the potential for chlorine releases to amplify oxidant chemistry in industrial areas. Regional air pollution issues such as acid rain, long-range transport of aerosols and visibility loss, and the connections of aerosols to ozone and peroxyacetyl nitrate chemistry are examined. Finally, the potential impacts of air pollutants on the global-scale radiative balances of gases and aerosols are discussed briefly.

La contaminación del aire es una amenaza aguda, acumulativa y
crónica para la salud humana y el ambiente. La exposición a la
contaminación del aire puede generar o agravar afecciones
respiratorias, cardiacas y otras, Los problemas de salud causados por
la contaminación del aire pueden verse influidos por factores tales
como magnitud, alcance y duración de la exposición, edad,
susceptibilidad de cada persona, entre otros.
La ciudad de Lima representa uno de los problemas ambientales más
relevantes en cuanto a contaminación del aire, las emisiones
procedentes del Parque Automotor constituyen la principal fuente de
contaminación con un aporte del 90% a la degradación del aire.
Es por ello que el objetivo y fin principal es implementar un Plan de
Monitoreo de la Calidad del Aire, que permitirá la evaluación periódica
a través de un procedimiento que permita verificar la eficacia y
eficiencia de la realización del monitoreo, con la finalidad de
implementar medidas correctivas hacia la mejora de la calidad del aire
a través de la sostenibilidad del recurso aire y del medio ambiente.

Atmosfer merupakan bagian yang tak terpisahkan dari planet bumi. Setiap lapisan di atmosfer mengandung peranan yang sangat vital untuk keberlangsungan kehidupan makhluk hidup yang ada di bumi. Manusia sebagai salah satu makhluk hidup yang berada di bumi seharusnya menjaga keberadaan atmosfer, misalnya dengan mencegah kerusakan lapisan ozon. Lapisan ozon adalah salah satu komponen penting dalam lapisan atmosfer bumi.

The present situation reveals the dependence on fossil fuels, which is seriously accountable for two major impediments: (i) global warming due to increasing atmospheric carbon dioxide (CO2) and (ii) the alarming consumption of energy assets. The reduction of green CO2 in terms of producing solar fuels would be an expedient accomplishment to resolve both problems, simultaneously. The review classifies different categories of photocatalysts applied in foregoing photocatalytic CO2 conversion processes with detailed information concerning operating conditions, preparation techniques and physical properties of catalysts, radiation sources, and selectivity. The categories are concentrated on metal oxides, sulfides, phosphides, and p-type and nonmetal oxide semiconductors. In addition, their modification by doping co-metals, noble metals, transition metals and non-metals for visible light response is emphasized. Besides, for harnessing solar fuel, the recent prospect and advancement of novel sensitized catalysts by dye elements, phthalocyanines and quantum dots (QDs) are also highlighted in this review. This technology needs more efficient solar active catalysts to increase production rates as well as selectivity. The recent scenario indicates that massive prospects and opportunities still exist in this area for further investigation on catalyst selection. This journal is © the Partner Organisations 2014.

http://pubs.rsc.org/en/Content/ArticleLanding/2014/RA/c4ra01769b

CBrF3 (Halon-1301) is a man-made ozone depleting substance that is a major source of bromine in the Earth's stratosphere. Halon-1301 is predominantly removed from the atmosphere by UV photolysis in the stratosphere at wavelengths between 200 and 225 nm. The existing level of uncertainty in the Halon-1301 UV absorption spectrum temperature-dependence directly impacts the ability to model stratospheric ozone chemistry and climate change. In this work, the UV absorption spectrum of Halon-1301 between 195 and 235 nm was measured over the temperature range 210–320 K. An empirical parameterization of the spectrum and its temperature dependence is presented. The present results are critically compared with results from previous studies and the current recommendation for use in atmospheric models. A global annually averaged lifetime for Halon-1301 of 74.6 (73.7–75.5) years was calculated using a 2-D atmospheric model and the present results. The range of lifetimes given in parenthesis represents the possible values due solely to the 2s uncertainty in the Halon-1301 UV spectrum obtained in this work. In addition, the CBrF3 ozone depletion potential was calculated using the 2-D model to be 18.6 (AE0.1) using the UV spectrum and 2s uncertainty from this work.