Trace Chemistry Research Articles

Chemistry of organic traces in air VI: Distribution of chlorinated C 1  C 4 hydrocarbons in air over the northern and southern Atlantic Ocean

Air-samples were collected on board of the German research vessel F.S. “POLARSTERN” on its cruise from Capetown to Bremerhaven (ANTARKTIS III/4, March 1985) by adsorption on Tenax TA. Additional samples were collected on the Azores ( 6 82 ), on Madeira ( 3 84 , 8 84 ) and on the Bermuda Islands ( 7 85 ). They were analyzed by high-resolution gas chromatography with electron-capture detection (HRGC-ECD). Tetrachloromethane (CCl 4) is taken as a stable internal standard in tropospheric air for the characterization of anthropogenic organohalogen trace gases such as CHCl 3, CH 2ClCH 2Cl, CH 3CCl 3, CHCl=CCl 2, CCl 2=CCl 2 and minor constituents such as CH 2ClCCl 3, CHCl 2CHCl 2, CHCl 2CCl 3, CCl 3CCl 3 and CCl 2=CClCCl=CCl 2. Latitudinal distributions over the Atlantic Ocean and differences between distinct air masses with different origins are shown. With the concept of a normalized pattern analysis it is possible to characterize sources, transport and degradation processes on a global scale.

Chemistry of organic traces in air

Chemistry of organic traces in air

The trace chemistries of fire hypothesis: Review and update

Formation de polluants dans les gaz d'incineration de dechets urbains: concentration de composes trace organique chlores dans les gaz. Facteurs variables influant sur la formation des polluants: structure moleculaire du fuel, contenu en chlore, presence de precurseurs et contaminants, temperature de reaction dans la zone de combustion et post-combustion, duree de sejour des reactifs, rapport air fuel...

The Use of Trace Chemistry to Estimate Seeding Effects in the National Hail Research Experiment

Four convective storms which occurred during the National Hail Research Experiment (NHRE) in northeast Colorado have been studied and confirm the hypothesis formed from an earlier study, that AgI aerosols released from aircraft into storms with defined cellular structure, are confined both temporally and spatially in the surface precipitation. This implies that portions of the storms receive substantial quantities of AgI aerosol using this seeding technique, whereas nearby precipitating portions of the same storms do not. Using radar, precipitation network data, upper air soundings and trace chemistry, estimates have been made of possible trajectories for the seeding aerosol and of times available for it to affect the cloud micro-structure. Compared with theoretical estimates, seeding rates used on the days investigated were occasionally large enough to achieve substantial phase change (water to ice) in the intended ice embryo competitive growth process. However, the evidence indicates that such levels were not achieved with sufficient regularity over the protected area to produce a hail suppression effect which could have been observed with the statistical methodology used in the NHRE analysis. The relationship between the quantities of precipitation sampled and their silver contents were investigated for each storm. The characteristics of the storms and the seeding of them varied considerably. Nevertheless, the results appear to fall into three categories; those where the AgI concentration was relatively constant over a wide range of precipitation amounts; those where the precipitation amounts were small and independent of silver contents; and those where there is a positive correlation between silver concentration and precipitation amount. For those cases where the Ag content is low and relatively constant, the results are consistent with the dominant capture processes being proportional to drop volume. For the two cases where precipitation amounts are small and independent of silver content, the rain fell from low radar reflectivity regions, at times long after seeding had occurred. The large variations of silver content are attributed to the non-uniform distribution of aerosol throughout the broad light precipitation regions. For the two cases where there is a positive correlation between silver concentration and precipitation amount, it is proposed that ice nucleation has played a dominant role, generating new ice embryos which in turn have resulted in increased rainfall. In both cases a silver concentration increase of 50 × 10−11 g mL−1 is associated with a precipitation increase of about 1700 g m−2, or 1.7 mm depth of water per square meter.

Trace chemistries of fire: a source of chlorinated dioxins.

New, highly specific and sensitive analytical methodology has been applied to the determination of chlorinated dibenzo- p -dioxins in particulate matter. The results show that the dioxins are present in particles from many types of combustion sources and in dust and soil in the vicinity of combustion sources. The data indicate that chlorinated dioxins may occur in particulate matter from the combustion of most types of organic material, and suggest the hypothesis that chlorinated dioxins result from trace chemical reactions occurring in fire.

The reliable determination of mercury traces in sea water by subtractive differential pulse voltammetry at the twin gold electrode

In the marine environment, mercury has the greatest toxicological significance among the common metals. By combining several basic principles of advanced voltammetry, a reliable and accurate procedure with a determination limit of 1 ng l -1 has been developed. The complete method, which is necessary for application to sea water, consists of cathodic deposition under programmed polarization with intermittent short anodic pulses to strip the co-deposited copper usually present in sea water in substantially larger amounts than mercury, subsequent medium exchange to 0.1 M HClO 4–2.5 × 10 -3 M HCl, and differential pulse anodic stripping in the subtractive mode at a twin gold disc electrode system. Construction of the twin electrode (which has its two halves insulated from each other), characteristics of the stages of the voltammetric procedure and its performance are presented. The method is very flexible and can be adapted and simplified for application to other aqueous matrices and natural waters with mercury levels above 100 ng l -1. The data from a case study yielding a survey of the mercury content in the German North Sea coastal waters demonstrate the significance of this new analytical procedure for research and monitoring tasks in marine trace chemistry.

Moderne voltammetrische Verfahren in der Spurechemie toxischer Metalle in Trinkwasser, Regen‐ und Meerwasser

AbstractModern voltammetric methods in trace chemistry of toxic metals in drinking water, rainwater and seawater. In environmental research and protection, toxic metals (particularly Cd, Pb and Hg) are becoming increasingly significant owing their biological nondegradability and the chronic toxicity resulting from their accumulation in vital organs of man. Aquatic systems, such as the sea, inland waters, drinking water, rainwater etc., are important stages in the biogeochemical cycle. Although the dissolved levels are usually in the trace range of μg/1 to ng/1 they still remain significant, because their entry into the food chain and interactions with suspended particulates and sedimnts largely occur via the dissolved state. General comparative considerations suggest modern voltammetric methods, particularly differential pulse stripping voltammetry (DPSV), to be the most promising choice for the determination and characterization of dissolved toxic heavy metal traces. Voltammetry combines extreme sensitivity with high inherent reliability, good precision, scope for simultaneous determination of several metals and modest costs. Moreover, due to its substance specificity, voltammetry permits identification and physicochemical characterization of dissolved complexes and chelates. The striking and comprehensive scope of voltammetry in trace metal chemistry of aquatic ecosystems is illustrated by examples from drinking water control, investigations on rainwater, extended studies in European coastal waters and the oceans, and by fundamental work on the occurrence and behaviour of toxic trace metal species in the sea.

New potentialities in ultra trace analysis with differential pulse anodic stripping voltammetry

A comprehensive study on the various trace analytical aspects and particularly the voltammetric parameters to optimize the performance of differential pulse anodic stripping voltammetry (d.p.a.s.v.) in connection with the mercury film electrode (MFE) has been carried out. Particularly via the optimal timing of cathodic deposition time t d, pulse duration t p, clock time t c of subsequent pulses, the sampling intervals t author and t en before and within t p, and the delay time t ds adjusting the position of t en within t p, and by appropriate adjustment of the scan rate v determining the number of pulses in the potential range of a peak, significant further improvements in sensitivity and performance are attainable. A further importantpractical achievement is that the required analysis time can be thus minimized. A new version of the standard addition approach for the evaluation of the peaks based on adjustment of constant amounts of respective metal amalgams in the mercury film is presented. In this manner also overloading difficulties connected with limited solubility of metals in mercury, e.g. Cu, are circumvented. The further improved high potentialities of d.p.a.s.v. at the MFE are demonstrated by practical examples on the determination of traces of Cd, Pb and Cu for which a determination limit of 1 ng l −1 or 1 ppt with <20% relative standard deviation has been established. The method has been meanwhile successfully applied in extended field studies in environmental and marine trace chemistry investigating sea water, inland waters, tap water, marine organisms, human whole blood, and various types of food.

Potentialities and applications of advanced polarographic and voltammetric methods in environmental research and surveillance of toxic metals

The versatile and significant potentialities of advanced polarographic and voltammetric methods in environmental trace chemistry of toxic metals are outlined. A variety of examples from biological materials over food to problems in the marine and aquatic environment are discussed with respect to the requirements in sample pretreatment and voltammetric methology to attain satisfactory accuracy. Further examples emphasize the particular potentialities of the polarographic and voltammetric approach for speciation studies at the trace level on toxic metals dissolved in sea water and inland waters.

Trace chemistry of toxic metals in biomatrices

Trace chemistry of toxic metals in biomatrices

P-Wave Residual Differences and Inferences on an Upper Mantle Source for the Silent Canyon Volcanic Centre, Southern Great Basin, Nevada

Summary Teleseismic P-wave travel-time residuals from six large nuclear detonations in the caldera of the Silent Canyon volcanic centre of the Nevada Test Site have been reduced by corresponding P-wave residuals of a nearby reference event (Dumont) in an attempt to map the deep structure of this volcanic centre. Each set of residual difference data is plotted on a projection of the lower focal hemisphere of Dumont. After corrections were applied for known low velocity rocks in the Silent Canyon caldera, data clusters of at least -1.0 s were found to dominate observations in the distance range 60–90 degrees. These large negative delays indicate the existence of a major high velocity anomaly that is directly beneath the Silent Canyon volcanic centre. Teleseismic P-wave residuals of two additional nuclear explosions, outside both the Silent Canyon caldera and the region of the reference event, were also reduced by Dumont residuals. The resulting data are distinct from the Silent Canyon residual difference fields and serve as a control on the primary experiment. The observed differential residuals, independent data on trace and major element chemistry of Silent Canyon lavas, and direct observations of effective Q argue that the high velocity anomaly is in the upper mantle. A model that satisfies the observed residual differences and which is consistent with additional seismic data possesses an anomalous zone which begins beneath the Mohorovicic discontinuity, at a depth of 40–50 km, extends to a depth of 170–190 km, and has a volume of 350000–600000 km3. This zone is interpreted as representing upper mantle material that has been largely depleted of its partial melt component by various differentiation processes and by associated eruption of the partial melt material through the Silent Canyon volcanic centre.

Atmospheric trace chemistry in the American humid tropics

Numerous attempts have been made to define global mean concentrations of trace substances and to incorporate these into global models of net source and sink strengths of the various natural and anthropogenic atmospheric contaminants. DOI: 10.1111/j.2153-3490.1974.tb01973.x

Atmospheric trace chemistry in the American humid tropics

Numerous attempts have been made to define global mean concentrations of trace substances and to incorporate these into global models of net source and sink strengths of the various natural and anthropogenic atmospheric contaminants.DOI: 10.1111/j.2153-3490.1974.tb01973.x

Study of the Plutonium (IV) - Arsenazo I Complex and its Applicability to the Analytical Chemistry of Plutonium Traces in Solution

Summary Aspectrophotometrical investigation of the tetravalent plutonium-arsenazo Icomplex was undertaken with the purpose of studying its analytical usefulness for the routine determination of trace amounts of plutonium in solution. The stock plutonium solution having systematically evidenciated the presence of great relative trivalent plutonium concentrations, some interesting conclusions could be drawn simultaneously for its corresponding complex by indirect means. A number of classical spectrophotometrical methods were used throughout this investigation with varying success due to the complexity of the system dealt with. In some particular instances full oxidation of the lower plutonium valence state towards the tetravalent state brought about by the arsenazo under certain acidity conditions and great excess of the reactive could be detected. Finally, a method for the routine determination of plutonium traces in solution is outlined, though its applicability to practical cases remains to be experimentally checked.

Physiological Potency of Dilute Traces

THE attention of readers must have been arrested by the brief reports contributed to NATURE1 at various times by Mr. Hugh Ramage, an eminent spectroscopic chemist, on the concentration of certain metals in special tissues of plants and animals, up to amounts spectroscopically measurable. The explanation would be that the ultra-infinitesimal amounts of these metallic substances that are present in the food that passes through the organism must be arrested in the organs concerned until the accumulation becomes sensible. An opening seems here to arise into the chemistry of minute traces, which is the aspect of that science that promises most for mathematical development.