Search results for "Chemical composition"
showing 10 items of 377 documents
Measurement report: PM<sub>2.5</sub>-bound nitrated aromatic compounds in Xi'an, Northwest China – seasonal variations an…
2021
Abstract. Nitrated aromatic compounds (NACs) are a group of key chromophores for brown carbon (light-absorbing organic carbon, i.e., BrC) aerosol, which affects radiative forcing. The chemical composition and sources of NACs and their contributions to BrC absorption, however, are still not well understood. In this study, PM 2.5 -bound NACs in Xi'an, Northwest China, were investigated for 112 daily PM 2.5 filter samples from 2015 to 2016. Both the total concentrations and contributions from individual species of NACs show distinct seasonal variations. The seasonally averaged concentrations of NACs are 2.1 (spring), 1.1 (summer), 12.9 (fall), and 56 ng m −3 (winter). Thereinto, 4-nitrophenol …
Shipborne measurements of Antarctic submicron organic aerosols: an NMR perspective linking multiple sources and bioregions
2020
Special issue Marine organic matter: from biological production in the ocean toorganic aerosol particles and marine clouds (ACP/OS inter-journalSI).-- 15 pages, 8 figures, 1 table, supplement https://doi.org/10.5194/acp-20-4193-2020
Geochemical implications for changing dust supply by the Indian Monsoon system to the Arabian Sea during the last glacial cycle
2004
Element concentrations of 43 elements as well as inorganic and organic carbon content of sediment core 70KL from the western Arabian Sea were measured with high (1 cm) sample resolution. Principal components of the sediment’s chemical composition were determined with the help of statistical principle component analysis. These components are representing the major environmental factors at the site. The most important processes controlling the observed variations are the changing lithogenic influx derived from the major wind systems of the region (i.e., the Arabian northwesterly winds, the northeast winter monsoon and the southwest summer monsoon), summer monsoon associated upwelling and biog…
Climatology of the average water-soluble volume fraction of atmospheric aerosol
2007
The average water-soluble volume fraction of atmospheric aerosol particles was inferred from measurements at three different locations across Central Europe. Together with a comprehensive literature review these data sets are classified into four aerosol types. The classified data are parameterized as a function of particle size using a logarithmic normal distribution function, which seems most appropriate to represent the hygroscopicity maximum in the accumulation size range. This parameterization can be used as a simplified input parameter for various model calculations. In addition, a summary on water-soluble volume fractions and hygroscopic growth factors is presented along with a short…
The dynamics of tropospheric aerosols
1966
After a brief review of the present knowledge of the Stratospheric sulfate layer, several possible mechanisms of formation are discussed in detail. A direct transport of low tropospheric particles into the stratosphere by convective clouds penetrating the tropopause is not very likely because these penetrations are not high enough and because of the chemical composition of the stratospheric particles. DOI: 10.1111/j.2153-3490.1966.tb00287.x
Size Matters More Than Chemistry for Cloud-Nucleating Ability of Aerosol Particles
2006
Size-resolved cloud condensation nuclei (CCN) spectra measured for various aerosol types at a non-urban site in Germany showed that CCN concentrations are mainly determined by the aerosol number size distribution. Distinct variations of CCN activation with particle chemical composition were observed but played a secondary role. When the temporal variation of chemical effects on CCN activation is neglected, variation in the size distribution alone explains 84 to 96% of the variation in CCN concentrations. Understanding that particles' ability to act as CCN is largely controlled by aerosol size rather than composition greatly facilitates the treatment of aerosol effects on cloud physics in re…
Regional variations in the chemical and helium–carbon isotope composition of geothermal fluids across Tunisia
2011
Abstract Tunisia has numerous thermo-mineral springs. Previous studies have shown that their chemical composition and occurrence are strongly influenced by the regional geology. However little work has been done so far to study the isotopic composition of volatiles associated with these geothermal manifestations. Here, we report on the results of an extensive survey of both natural hot springs and production wells across Tunisia, aimed at investigating the spatial distribution of thermal fluids' geochemical characteristics and He–C isotopic composition. The chemistry of the analyzed samples highlights the heterogeneity of the water mineralization processes in Tunisia, as a consequence of th…
Vanadium Carbide Dissolution during Austenitisation of a Model Microalloyed FeCV Steel
2005
High performance commercial micro alloyed steels contain elements such as vanadium, which leads to a fine dispersion of vanadium carbide precipitates. The precipitation state, in terms of volume fraction and size distribution, plays a significant role in final mechanical properties of the material. Different austenitisation heat treatments were performed on a model ternary alloy FeCV. Precipitation states were characterised combining different experimental techniques. TEM was used to identify the chemical composition of observed precipitates. ICP mass spectroscopy was performed to measure the volume fraction of precipitates. The size distribution was studied by SEM. Results are characterist…
Fatty Acids as Biomarkers of the Production Season of Caciocavallo Palermitano Cheese
2021
Simple Summary In the Mediterranean environment, climatic variability determines a discontinuity in the forage availability of pastures. Caciocavallo Palermitano is a cheese obtained from the milk of the Cinisara cattle breed, mainly raised on pasture. The present study investigated the fatty acid profile of cheeses produced in two typical farms in the four seasons of the year, with the aim of identifying specific fatty acids that can be used as biomarkers to discriminate the productions obtained in the different seasons, in order to economically enhance those seasonal productions that have better health characteristics. The results revealed the possibility of distinguishing spring producti…
Chemical composition of the essential oil of Phagnalon saxatile (L.) Cass. (Asteraceae) growing wild in Southern Italy
2005
Abstract The essential oil from aerial parts of Phagnalon saxatile (L.) Cass. (Asteraceae) was obtained by hydrodistillation. The oil content was 0.15% (v/w), on a dry weight basis. The oil composition was analyzed by GC and GC/MS. Altogether 66 compounds were identified accounting for 93.2% of the oil. Sesquiterpenes represent the 23.9% of the oil. In the oil were also present fatty acids (21.8%) and waxes (19.3%). The oil shows no antibacterial activity.