Characterization of high molecular weight compounds in urban atmospheric particles

International audienceThe chemical nature of a large fraction of ambient organic aerosol particles is not known. However, high molecular weight compounds (often named humic-like substances) have recently been detected by several authors and these compounds seem to account for a significant fraction of the total organic aerosol mass. Due to the unknown chemical structure of these compounds a quantification as well as a determination of their molecular weight is difficult. In this paper we investigate water soluble humic-like substances in ambient urban aerosol using size exclusion chromatography-UV spectroscopy and laser desorption/ionization mass spectrometry. A careful method evaluation shows that both methods complement each other and that both are needed to learn more about the molecular weight distribution and the concentration of humic-like substances. An upper molecular weight limit of humic-like substances of about 700 Da and a concentration of 0.2?1.8 µg/m3 air can be estimated corresponding to 8?33% of the total organic carbon for an urban background site

Measurement of ambient aerosol hydration state at Great Smoky Mountains National Park in the southeastern United States

We present results from two field deployments of a unique tandem differential mobility analyzer (TDMA) configuration with two primary capabilities: identifying alternative stable or meta-stable ambient aerosol hydration states associated with hysteresis in aerosol hydration behavior and determining the actual Ambient hydration State (AS-TDMA). This data set is the first to fully classify the ambient hydration state of aerosols despite recognition that hydration state significantly impacts the roles of aerosols in climate, visibility and heterogeneous chemistry. The AS-TDMA was installed at a site in eastern Tennessee on the border of Great Smoky Mountains National Park for projects during the summer of 2006 and winter of 2007–2008. During the summer, 12% of the aerosols sampled in continuous AS-TDMA measurements were found to posses two possible hydration states under ambient conditions. In every case, the more hydrated of the possible states was occupied. The remaining 88% did not posses multiple possible states. In continuous measurements during the winter, 49% of the aerosols sampled possessed two possible ambient hydration states; the remainder possessed only one. Of those aerosols with multiple possible ambient hydration states, 65% occupied the more hydrated state; 35% occupied the less hydrated state. This seasonal contrast is supported by differences in the fine particulate (PM<sub>2.5</sub>) composition and ambient RH as measured during the two study periods. In addition to seasonal summaries, this work includes case studies depicting the variation of hydration state with changing atmospheric conditions

Light absorption by polar and non-polar aerosol compounds from laboratory biomass combustion

Fresh and atmospherically aged biomass-burning (BB) aerosol mass is mostly comprised of strongly light-absorbing black carbon (BC) and of organic carbon (OC) with its light-absorbing fraction – brown carbon (BrC). There is a lack of data on the physical and chemical properties of atmospheric BB aerosols, leading to high uncertainties in estimates of the BB impact on air quality and climate, especially for BrC. The polarity of chemical compounds influences their fate in the atmosphere including wet/dry deposition and chemical and physical processing. So far, most of the attention has been given to the water-soluble (polar) fraction of BrC, while the non-polar BrC fraction has been largely ignored. In the present study, the light absorption properties of polar and non-polar fractions of fresh and aged BB emissions were examined to estimate the contribution of different-polarity organic compounds to the light absorption properties of BB aerosols. In our experiments, four globally and regionally important fuels were burned under flaming and smoldering conditions in the Desert Research Institute (DRI) combustion chamber. To mimic atmospheric oxidation processes (5–7 days), BB emissions were aged using an oxidation flow reactor (OFR). Fresh and OFR-aged BB aerosols were collected on filters and extracted with water and hexane to study absorption properties of polar and non-polar organic species. Results of spectrophotometric measurements (absorption weighted by the solar spectrum and normalized to mass of fuel consumed) over the 190 to 900nm wavelength range showed that the non-polar (hexane-soluble) fraction is 2–3 times more absorbing than the polar (water-soluble) fraction. However, for emissions from fuels that undergo flaming combustion, an increased absorbance was observed for the water extracts of oxidized/aged emissions while the absorption of the hexane extracts was lower for the aged emissions for the same type of fuels. Absorption Ångström exponent (AAE) values, computed based on absorbance values from spectrophotometer measurements, were changed with aging and the nature of this change was fuel dependent. The light absorption by humic-like substances (HULIS) was found to be higher in fuels characteristic of the southwestern USA. The absorption of the HULIS fraction was lower for OFR-aged BB emissions. Comparison of the light absorption properties of different-polarity extracts (water, hexane, HULIS) provides insight into the chemical nature of BB BrC and its transformation during oxidation processes

Respiratory diseases in young cattle

The following review considers modern scientific data on respiratory diseases in young cattle. The problem of respiratory diseases in calves does not lose its relevance, since these pathologies rank second in frequency after diseases of the digestive system. In order to compile the data, the works of domestic and foreign researchers and collectives available in the collections of scientific conferences, seminars, symposiums, as well as in peer-reviewed periodicals, materials of dissertations and abstracts were reviewed. The group of pathologies under consideration is sufficiently diverse and can be caused by high animal density in the premises, overheating, hypothermia, unbalanced feeding, micronutrient deficiency, decreased body resistance, unfavorable epidemic situation and many other factors. However, out of the major calf diseases, particular mention should be made of pneumonia, which is most often caused by viruses. In this case agents can induce bacterial infection which aggravates and complicates the course of viral diseases. Microorganisms, such as Salmonella, Pasteurella and others, contribute to secondary infection and cause mixed forms of pneumonia. Bronchopneumonia is another disease covered in the article. It is a respiratory pathology characterized by inflammation of both the bronchi and lungs. As a rule, such disease types are most common in industrial animal husbandry, they are widespread and cause significant economic damage to the dairy and beef cattle breeding industries. The article pays great attention to these pathologies, justifies the importance of comprehensive preventive measures and timely diagnosis for livestock industries. To reduce the incidence of respiratory diseases in young cattle, it is necessary to strictly follow technological and hygienic standards for animal keeping and feeding. The use of combined medicines and preparations containing microelements increases treatment effectiveness

Changes of fatty acid aerosol hygroscopicity induced by ozonolysis under humid conditions

Unsaturated fatty acids are important constituents of the organic fraction of atmospheric aerosols originating from biogenic or combustion sources. Oxidative processing of these may change their interaction with water and thus affect their effect on climate. The ozonolysis of oleic and arachidonic acid aerosol particles was studied under humid conditions in a flow reactor at ozone exposures close to atmospheric levels, at concentrations between 0.5 and 2 ppm. While oleic acid is a widely used proxy for such studies, arachidonic acid represents polyunsaturated fatty acids, which may decompose into hygroscopic products. The hygroscopic (diameter) growth factor at 93% relative humidity (RH) of the oxidized arachidonic particles increased up to 1.09 with increasing RH during the ozonolysis. In contrast, the growth factor of oleic acid was very low (1.03 at 93% RH) and was almost invariant to the ozonolysis conditions, so that oleic acid is not a good model to observe oxidation induced changes of hygroscopicity under atmospheric conditions. We show for arachidonic acid particles that the hygroscopic changes induced by humidity during ozonolysis are accompanied by about a doubling of the ratio of carboxylic acid protons to aliphatic protons. We suggest that, under humid conditions, the reaction of water with the Criegee intermediates might open a pathway for the formation of smaller acids that lead to more significant changes in hygroscopicity. Thus the effect of water to provide a competing pathway during ozonolysis observed in this study should be motivation to include water, which is ubiquitously present in and around atmospheric particles, in future studies related to aerosol particle aging

FOLATE DEFICIENCY IN OBSTETRICS AND THE PROBLEM OF ITS CORRECTION

The article considers the reasons and the role of the folate deficiency in development of the complicated pregnancy and congenital malformations. The biological functions of folate in an organism are described, as well as the role of folate in an exchange of methionine and a hyperhomocysteinemia as one of the reasons of malformations and complications of pregnancy. The role of a genetic mutation of MTHFR as the hyperhomocysteinemia reasons at patients with deficiency of folate and the treatment of the state of the deficiency of folate are discussed

Sechenov First Moscow State Medical University (Sechenov University)

This article is devoted to the most common bone tissue tumor among children — Ewing's sarcoma. The epidemiological data, most frequent afflicted zones of bones, clinical signs, diagnostics and treatment methods are analysed. The main focus is on the molecular genetic mechanisms of carcinogenesis initiation

Etiopathogenetic risk factors for stroke in pregnant women

Stroke is a severe thrombotic condition that can occur in women of reproductive age during their pregnancy. Physiological changes that occur during gestation, childbirth and the postpartum period predispose a woman to the development of thrombotic complications. However, the true causes of cerebrovascular accidents are not fully understood. More than 50 % of strokes occur in the absence of obvious risk factors. The article reviews etiological and pathogenetic mechanisms of cerebral blood flow disorders and factors contributing to this condition in pregnant women