Inner-city children have high rates of asthma. Exposures to particles, including allergens, may cause or exacerbate asthma symptoms. As part of an epidemiologic study of inner-city children with ...asthma, continuous (10-min average) measurements of particle concentrations were made for 2-week periods in 294 homes drawn from seven cities. Measurements were made using an optical scattering device that is most sensitive to fine particles. The concentrations recorded by these devices were corrected to agree with colocated outdoor gravimetric PM2.5monitors. Indoor concentrations in the homes averaged 27.7 (standard deviation = 35.9) μ g/ m3, compared with concurrent outdoor concentrations of 13.6 (7.5) μ g/ m3. A multivariate model indicated that outdoor particles penetrated indoors with an efficiency of 0.48 and were therefore responsible for only 25% of the mean indoor concentration. The major indoor source was smoking, which elevated indoor concentrations by 37 μ g/ m3in the 101 homes with smokers. Other significant sources included frying, smoky cooking events, use of incense, and apartment housing, although the increases due to these events ranged only from 3 to 6 μ g/ m3. The 10-min averaging time allowed calculation of an average diurnal variation, showing large increases in the evening due to smoking and smaller increases at meal times due to cooking. Most of the observed variance in indoor concentrations was day to day, with roughly similar contributions to the variance from visit to visit and home to home within a city and only a small contribution made by variance among cities. The small variation among cities and the similarity across cities of the observed indoor air particle distributions suggest that sources of indoor concentrations do not vary considerably from one city to the next, and thus that simple models can predict indoor air concentrations in cities having only outdoor measurements.
Due to their high surface coverage, good adhesion to metal surfaces, and their excellent corrosion resistance, epoxy thermosets are widely used as protective coatings. However, anticorrosion ...protection of these coatings can be improved against water uptake and can be tuned by changing the chemical nature of the curing agents. In this work, a comparative study has been performed on the water uptake of an epoxy-amine based on bisphenol A diglycidyl ether (DGEBA) cured with an aliphatic amine and the same epoxy initiated with a phosphonium ionic liquid (IL). Thus, the epoxy networks were immersed in saline water solution in a controlled temperature environment. Gravimetric and electric impedance measurements were carried out for a maximum of 3 months. Results were analyzed in order to assess the water diffusion coefficients and water saturation limits. Two models, the Brasher-Kingsbury and a novel mixing rule, were applied on permittivity values. Results highlighted that epoxy-ionic liquid systems are less sensitive to water uptake than conventional epoxy-amine networks. Due to their higher hydrophobic properties the water diffusion coefficient of epoxy-ionic liquid systems are two times less compared to epoxy-amine samples and the water saturation limit is more than four times less. The analysis also shows that the novel mixing rule model proposed here is prone to better estimate the water uptake with accuracy from electrical impedance measurements.
Microwave-assisted organic synthesis involves simple work procedure and gives high yield of product. In view of this we have synthesized bis-phenol formaldehyde polymer containing piperazine by ...microwave technique and investigated its inhibition action on corrosion of mild steel in 1 M HCl using gravimetric, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) and potentiodynamic polarization techniques. The Tafel polarization study reveals that inhibitor acts as mixed-type inhibitor. EIS study indicates that it inhibits corrosion by adsorption mechanism. The adsorption of polymer on mild steel followed Langmuir adsorption isotherm. In optical microscopy examination inhibited mild steel surface was found to be smoother than uninhibited mild steel surface.
The paper reviews the gravimetric measurements carried out in Lithuania over the last twenty years. The first absolute ballistic gravimetric measurements were carried out at the three points by ...Jaakko Mäkinen (Finish Geodetic Institute) in 1994. The 5 μGal precision of the gravity acceleration was derived. These measurements allowed to adopt the IGSN71 gravity system in Lithuania instead of earlier used Potsdam gravity system. The national first order gravimetric network of Lithuania was developed during the period of 1998–2001. It consists of 51 points. The measurements were carried out by 3–6 LaCoste & Romberg gravimeters. In 2007–2009 the second order gravimetric network was developed. It consists of 635 points. The measurements were carried out by two pairs of the Scintrex CG-5 gravimeters. The gravity acceleration was measured with an accuracy better than 10 μGal.The gravimetric Bouguer anomaly map, based on gravimetric survey of the period 1954–1962, was evaluated against the gravimetric network data. The results of the evaluation show that the accuracy of the gravity acceleration value, derived from the gravimetric map, is about 0.7 mGal and that the average difference between the IGSN71 gravity system and Potsdam gravity system is about 13.93 mGal in Lithuania territory.
Fine particulate concentration data resulting from several monitoring campaigns performed in the city of Milan at urban sites with different exposure to the emission sources are presented. Low volume ...PM2.5 and PM1 samplers are utilised together with a low volume optical analyser, enabling the intercomparison between the measurements obtained by the gravimetrical and the optical method. The concentration levels observed at the different sites are compared in order to point out intra-site seasonal differences and inter-site differences for corresponding seasons of the year. These different concentration levels are analysed and explained considering the exposure to the primary emissions and accounting for the role of meteorology. PM10, PM2.5 and PM1 are described in terms of the distribution of 1-h concentration data and their relative mass fractions are determined. In order to assess the significance of secondary sources of fine particulate, a PM2.5 high volume sampler is utilised for the collection of dust-loaded filters to be analysed for chemical characterisation. The composition of PM2.5 emission from traffic is investigated by analysing 24-h samples from an urban tunnel site (TU): data on carbonaceous species, organic carbon (OC) and elemental carbon (EC), are obtained and the ratio between these species is evaluated for real traffic emissions. Secondary organic aerosol (SOA) contribution to PM2.5 mass in ambient air is assessed by means of the primary OC/EC ratio approach, based on chemical data of the filters from the TU. Organic and inorganic secondary production in the outdoor atmosphere is contributing for about 75% of PM2.5 mass in winter and 40% in summer: as a consequence, effective long-term actions, still controlling the emissions of primary pollutants too, are required for air quality standards attainment and the potentiality of short-term interventions, as traffic restriction, appears quite limited.
The effect of sodium molybdate (Na
2
MoO
4
) on the corrosion of cold rolled steel (CRS) in peracetic acid (PAA) solution was investigated by gravimetric measurements, Tafel polarization curves, ...potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). All the data indicate that Na
2
MoO
4
acts as a very good inhibitor in PAA solution. The inhibition efficiency increases with increasing concentration of Na
2
MoO
4
and immersion time. The inhibition efficiencies, calculated from gravimetric measurements, Tafel polarization curves and electrochemical impedance spectroscopy, are in reasonably good agreement and are very similar in the three cases. Furthermore, polarization data show that Na
2
MoO
4
behaves as an anodic passive type inhibitor. Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) were used to characterize the corrosion surface. A probable mechanism is presented to explain the experimental results.
Activated carbon samples from coconut shells (Brazilian coconut species “Coco da Baía”) were prepared by chemical activation with phosphoric acid as the activating agent. Samples were characterized ...by nitrogen adsorption isotherms at 77 K. Some samples were randomly chosen in order to perform methane adsorption experiments under pressures between 1 and 60 bar at 303 K. A close relationship between surface area, micropore volume and methane adsorption capacity for carbons prepared from the same starting material was observed. The highest methane storage capacity in the tested samples was found to be 95 v/v at 303 K and 35 bar, which is comparable to results obtained for commercial samples indicated for this application. A moderate concentration of phosphoric acid (around 35%) seems to favor high surface areas, micropore volumes and, hence, gas storage capacity. The inclusion of an acid wash step before carbonization and the use of inert gas flow during carbonization also seem to enhance the development of porosity. This result suggests that activated carbons prepared from “Coco da Baía” by chemical activation with phosphoric acid have potential to be used as a storage media for natural gas.
Aerosol composition and properties variation under the advection of different air masses were investigated, as case studies, by contemporary measurements over the atmospheric column and at the ground ...in a semi-rural site in South Italy. The absence of local strong sources in this area allowed to characterize background aerosol and to compare particle mixing effects under various atmospheric circulation conditions. Aerosol optical depth (AOD) and Ǻngström parameters from radiometric measurements allowed the detection and identification of polluted, dust, and volcanic atmospheric conditions. AODs were the input for a suitable model to evaluate the columnar aerosol composition, according to six main tmospheric components (water-soluble, soot, sea salt accumulation, sea salt coarse, mineral dus,t and biological). Scanning electron microscope (SEM) analysis of particulate sampled with a 13-stage impactor at the ground showed not only fingerprints typical of the different air masses but also the effects of transport and aging on atmospheric particles, suggesting processes that changed their chemical and optical properties. Background columnar aerosol was characterized by 72 % of water-soluble and soot, in agreement with ground-based findings that highlighted 60 % of contribution from anthropogenic carbonate particles and soot. In general, a good agreement between ground-based and columnar results was observed. Under the advection of trans-boundary air masses, water-soluble and soot were always present in columnar aerosol, whereas, in variable percentages, sea salt and mineral particles characterized both dust and volcanic conditions. At the ground, sulfates characterized the amorphous matrix produced in finer stages by the evaporation of solutions of organic and inorganic aerosols. Sulfates were also one of the key players involved in heterogeneous chemical reactions, producing complex secondary aerosol, as such clay-sulfate internally mixed particle externally mixed with soot chains.
The article investigates four automatic gravimeters Scintrex CG-5. With reference to the measurements of the gravimetric calibration base set up in Lithuania, linear scale coefficients and the ...character of changes in the linear scale coefficients of gravimeters were estimated. The paper examines the vertical gradient of gravity acceleration in the eight-floor building, evaluates the range of changes into gravimeter drifts under laboratory conditions and describes daily gravimeter drift during gravimetric measurements.
Santrauka
Atlikti keturių Scintrex CG-5 gravimetrų tyrimai. Remiantis gravimetrinės bazės, įrengtos Lietuvos teritorijoje, matavimų duomenimis, nustatyta gravimetrų kalibravimo koeficientai ir jų kitimo pobūdis. Atlikti sunkio pagreičio vertikaliojo gradiento aštuonių aukštų pastate tyrimai. Laboratorinėmis sąlygomis nustatytas gravimetrų paros nulio slinkties kitimo diapazonas. Atlikti gravimetrų nulio slinkties matavimų metu tyrimai.
Резюме
Проведены исследования четырех гравиметров Scintrex CG-5. На основании измерений гравиметрической базы, находящейся на территории Литвы, получены коэффициенты калибровки гравиметров. Проведены исследования вертикального градиента ускорения силы тяжести в восьмиэтажном здании. Определен диапазон изменения лабораторного суточного смещения нуль-пункта гравиметров. Также оценено смещение нуль-пункта гравиметров во время измерений гравиметрической базы.
PDF
