Cosmic dust in the earth's atmosphere

This review discusses the magnitude of the cosmic dust input into the earth's atmosphere, and the resulting impacts from around 100 km to the earth's surface. Zodiacal cloud observations and measurements made with a spaceborne dust detector indicate a daily mass input of interplanetary dust particles ranging from 100 to 300 tonnes, which is in agreement with the accumulation rates of cosmic-enriched elements (Ir, Pt, Os and super-paramagnetic Fe) in polar ice cores and deep-sea sediments. In contrast, measurements in the middle atmosphere - by radar, lidar, high-flying aircraft and satellite remote sensing - indicate that the input is between 5 and 50 tonnes per day. There are two reasons why this huge discrepancy matters. First, if the upper range of estimates is correct, then vertical transport in the middle atmosphere must be considerably faster than generally believed; whereas if the lower range is correct, then our understanding of dust evolution in the solar system, and transport from the middle atmosphere to the surface, will need substantial revision. Second, cosmic dust particles enter the atmosphere at high speeds and undergo significant ablation. The resulting metals injected into the atmosphere are involved in a diverse range of phenomena, including: the formation of layers of metal atoms and ions; the nucleation of noctilucent clouds, which are a sensitive marker of climate change; impacts on stratospheric aerosols and O(3) chemistry, which need to be considered against the background of a cooling stratosphere and geo-engineering plans to increase sulphate aerosol; and fertilization of the ocean with bio-available Fe, which has potential climate feedbacks.     

对硫磷分子印迹聚合物制备及其在水质检测中的应用

为了有效的分离富集水样中有机磷农药,以对硫磷为模板、三羟甲基丙烷三丙烯酸酯为交联剂,采用紫外聚合方法制备了对硫磷分子印迹聚合物(MIP)。利用紫外光谱、红外光谱研究了对硫磷与不同功能单体间作用力及印迹聚合物的结合位点。利用该MIP,建立MIP-固相萃取-气相色谱法测定水中痕量对硫磷,方法的检出限(3S/N)为0.48μg/L,加标回收率为86.2%～115.7%,相对标准偏差(n=6)为3.0%～6.6%。     

The determination of individual gaseous ionic alkyllead species in the atmosphere

Gaseous ionic alkyllead species (in the ng Pb m^?3 range) are collected from air by absorption in water. After extraction into n-hexane, they are propylated or butylated and quantified by gas chromatography/electrothermal atomic absorption spectrometry. Interference from inorganic lead compounds and aerosol-phase alkyllead compounds is entirely absent, whilst that from tetraalkyllead compounds is small and generally negligible. This method allows the unequivocal identification of gaseous ionic alkyllead species in the atmosphere.     

The determination and role of peroxyacetil nitrate in photochemical processes in atmosphere

Peroxyacetilnitrates (PAN) is the most characteristic photoxidant of a range of secondary pollutants formed by the photochemical reaction of hydrocarbons with nitrogen oxides in the atmosphere: it is phytotoxic and shows an increasing role in human health effects due to ambient air exposure, especially in presence of high ozone concentrations. Because of the similarity of the conditions required for their photochemical production PAN is observed in conjunction with elevated ozone concentrations. PAN has very low natural background concentrations so it is the very specific indicator of anthropogenic photochemical air pollution. In this paper we report PAN concentrations determined in Rome urban area during winter- and summer-period. PAN measurements were carried out by means of a gas-chromatograph equipped with an Electron Capture Detector (ECD) detector. For identifying the acute episodes of atmospheric photochemical pollutants the relationship between PAN and the variable Ox (=NO2+O3) which describes the oxidation process evolution is investigated. The role of Volatile Organic Compounds and PAN in the ozone formation is investigated as well the issue of taking in account the autovehicular emissions for checking the NOx fraction in fuel.     

Spectrophotometric determination of beryllium in air and dust

The requirements of beryllium monitoring are discussed. Emphasis is placed on developing an Analytical procedure which is rapid, simple to operate, of adequate sensitivity and of reasonable accuracy. For air analysis, beryllium bearing dust is collected on a membrane filter, the beryllium is obtained in solution and determined spectrophotometrically, using aurine tricarboxylic acid (aluminon) as reagent Interference due to other metals is avoided by the addition of suitable complexing agents. A sensitivity of 0 1 μg Be can be achieved     

A novel amperometric sensor and chromatographic detector for determination of parathion

A novel amperometric sensor and chromatographic detector for determination of parathion has been fabricated from a multi-wall carbon nano-tube (MWCNT)/Nafion film-modified glassy-carbon electrode (GCE). The electrochemical response to parathion at the MWCNT/Nafion film electrode was investigated by cyclic voltammetry and linear sweep voltammetry. The redox current of parathion at the MWCNT/Nafion film electrode was significantly higher than that at the bare GCE, the MWCNT-modified GCE, and the Nafion-modified GCE. The results indicated that the MWCNT/Nafion film had an efficient electrocatalytic effect on the electrochemical response to parathion. The peak current was proportional to the concentration of parathion in the range 5.0×10^–9–2.0×10^–5 mol L^–1. The detection limit was 1.0×10^–9 mol L^–1 (after 120 s accumulation). In high-performance liquid chromatography with electrochemical detection (HPLC–ED) a stable and sensitive current response was obtained for parathion at the MWCNT/Nafion film electrode. The linear range for parathion was over four orders of magnitude and the detection limit was 6.0×10^–9 mol L^–1. Application of the method for determination of parathion in rice was satisfactory.     

Specific method for the determination of ozone in the atmosphere

A simple, sensitive and specific method for the determination of ozone in the atmosphere is described. Reactions of ozone with several 1-alkenes were studied at room temperature (25°). Eugenol(4-allyl-2-methoxyphenol), when reacted with ozone, was found to produce relatively large amounts of formaldehyde compared to other 1-alkenes tested. The method described was compared with alkaline iodide method for the determination of various concentrations of ozone in the range 0.05–2.0 p.p.m. Hydrogen peroxide, peracetic acid, sulfur dioxide and various reducing agents commonly present in the air, do not interfere. Formaldehyde when present in the air, must be determined simultaneously and the concentration of formaldehyde subtracted from that of the ozone. Any formaldehyde monitoring equipment can be easily adapted for the determination of ozone.     

The determination of rhenium in flue dust by neutron activation analysis

Rhenium was determined by radiochemical neutron activation analysis in flue dust samples of complex chemical composition. Two separation techniques were used; distillation from perchloric-hydrochloric acid solution and hydroxide scavenging followed by extraction with tetraphenylarsonium chloride in chloroform. ¹⁸⁶Re and ¹⁸⁸Re were measured with a Ge(Li) low-energy photon detector. Chemical yields were determined by reactivation. For a neutron flux of 5·10¹¹ n cm^-2 s^-1, an irradiation time of 6 h and samples of ca. l g, down to 50 p.p.b. of rhenium could be determined.     

The determination of nickel in air dust by neutron activation analysis

The determination of nickel in atmospheric aerosols, collected on filter paper, is performed by thermal neutron activation analysis using the⁶⁵Ni (T=2.56 h) isotope. Liquid-liquid extraction and anion-exchange are applied in the chemical separation. The absolute sensitivity of the method is ≌0.02 μg Ni. The relative sensitivity is 0.005 μg Ni/m³ if an air sample of about 1000 m³ is used.     

Electrospun zirconia-embedded carbon nanofibre for high-sensitive determination of methyl parathion

Carbon nanofibers embedded with ultrafine zirconia nanoparticles (ZrO₂-CNFs) are fabricated via a new methodology. Polyvinylpyrrolidone (PVP) and polymethylmethacrylate (PMMA) binary polymers containing zirconium n-butoxide are first dissolved in dimethylformamide, and the resulting solution is electrospun and heat-treated. The tetragonal zirconia nanoparticles formed, with a size of 5 ± 2 nm in diameter, are uniformly distributed in the carbon nanofibres. Using Nafion as an additive, ZrO₂-CNFs are drop-cast onto the glassy carbon electrode (ZrO₂-CNF/GCE) and the modified electrode is then applied to detect methyl parathion (MP) using differential pulse voltammetry. Two linear relationships are found at the concentration ranges of 1 × 10^− 9–2 × 10^− 8 g/L and 2 × 10^− 8–2 × 10^− 7 g/L, with a detection limit of 3.4 × 10^− 10 g/L (S/N > 3). The electrospun-based ZrO₂-CNF is a very promising coating material for electrochemical sensing of organophosphorus compounds.     

Potentiometric determination of chloride and bromide in airborne dust

Summary A simple, rapid and reproducible potentiometric titration method for determination of both bromide and chloride in airborne dust is described. The use of a precise microburette and a differentiating recorder allows good resolution of the two species determined. The method can be easily applied for routine environmental control analysis.

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Zusammenfassung Die Anwendung eines einfachen, schnellen und reproduzierbaren potentiometrischen Verfahrens zur Bestimmung von Bromiden und Chloriden in Stauben wurde beschrieben. Der Einsatz einer Motorkolbenbürette für die relativpotentiometrische Titration und die Verwendung eines Differentiators erlauben eine exakte Bestimmung des Titrationsendpunktes und ermöglichen so das gute Auflösungsvermögen des Verfahrens. Die Methode wurde routinemäßig in der Umweltanalytik eingesetzt.

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On leave from Faculty of Chemistry, University of Sofia, Sofia, Bulgaria.     

Atomic-absorption spectrophotometric determination of volatile organolead compounds in the atmosphere

Summary The determination of the total concentration of tetraalkyllead compounds in the air is based on the cryogenic condensation in a cooled trap at –130° C, thermal desorption at 60° C into impingers containing nitric acid and hydrogen peroxide and a determination with graphite furnace atomic-absorption. The method is highly specific and suffers no interferences from lead in the particulate phase. The detection limit is 42 ng Pb/m³ for air samples of ca. 3601.This work was carried out within the framework of the National Research and Development Program on Environment of the Interministrial Commission for Science Policy, Belgium.     

Multicommutation cold vapour atomic fluorescence determination of Hg in water

A multicommutation-based method has been developed for the on-line direct atomic fluorescence spectrometric (AFS) determination of Hg in waters without any previous sample treatment. The performance of the proposed procedure has been compared with that of a conventional AFS system based on continuous mode measurements. In short, the use of multicommutation, together with a reduction of the size of the liquid-gas phase separator, provides an increase of the laboratory productivity by improving the sample throughput by a factor of 3.6 and strongly reduces the sample consumed by a factor of 6 and reagent consumed by a factor of 8.4. The waste generation is reduced by a factor of 2.4 and the Ar consumed by a factor of 6, thus the developed method is an environmentally and economically sustainable alternative to the methodology based on continuous measurements, without any reduction of the analytical sensitivity and with an enhancement of the repeatability of measurements. Only the limit of detection was poorer for the methodology developed (1.3 ng l⁻¹) than that found by the classical continuous mode (0.3 ng l⁻¹). The aforementioned methodologies were applied to the determination of Hg in water samples having obtained comparable values by both procedures and with those found by an external laboratory.