Concentrations Of Trace Substances Research Articles

The mechanism of fluorescence quenching of naphthalimide A/C leak detector by copper (II)

BackgroundFluorescence quenching is an interesting phenomenon with the potential to be applied across various fields. The mechanism is commonly used across analytical applications for monitoring the concentration of trace substances. Naphthalimide and its family of compounds are commonly used as fluorescent detectors. This work investigated an analytical technique through which naphthalimide-based dyes could be quantified. A commercial A/C leak detector was used as the dye and Cu2+ ions as the quencher. Experiments were also conducted to investigate the effect of temperature on quenching. To study the mechanism of quenching further, density functional theory (DFT) was used.ResultsThe method detection limit obtained in this work is 1.7 × 10–6 mol/L. The results from the quenching experiments demonstrated a pattern which fit a modified Stern–Volmer (SV) model, with an R2 value of 0.9886. From the experiments on the effect of temperature, a dynamic quenching behavior was observed given the emission spectra demonstrated an inverse relationship with temperature.ConclusionsThe quenching of the commercial A/C dye by Cu2+ ions can be used to develop a rapid and sensitive detection method for metal ions such as Cu2+, and for future fabrication of chemosensors for Cu2+.

Distribution of trace substances in the coolant of a BWR fuel element

A transport model was developed and numerically solved for trace substances dissolved in the coolant flowing through a complete BWR fuel element. The integration of the trace substance transport equations is carried out on the same computational grid used by a two-phase three-field subchannel code, the output of which provides the necessary coolant mass flow data, including field exchange terms. The results consist of complete, field specific trace substance distributions within the domain of the simulation and with the same spatial resolution as used by the subchannel code. Downstream the onset of annular flow, it was observed that the trace substance concentrations in liquid films on heated rods are significantly higher than the concentrations in droplets and in films on unheated surfaces. A mechanistic model for disturbance waves was further introduced to assess the additional trace substance concentration increase in the time period of base film evaporation between two successive disturbance waves. The highest trace substance concentrations were found next to part-length rods in the corner of the considered fuel assembly just upstream of the two uppermost spacer grids, which approximately corresponds to the location of trace substance deposition observed during fuel inspections at a Swiss nuclear power plant.

An Investigation into the Effect of Emissions from Industrial Complexes on Air Quality in the Ulsan Metropolitan City Utilizing Trace Components in PM2.5

This study investigates the impact of industrial complexes on the air quality in the Ulsan Metropolitan City, Korea, by analyzing the concentration of trace substances. Importantly, this study performs segmentation and analysis of the components of particulate matter for tracking emission sources. Concentrations of particulate matter with aerodynamic diameters ≤10 and ≤2.5 µm (PM10 and PM2.5, respectively) and 19 substances comprising PM2.5 (such as ions, carbon, and nine elements) were measured hourly during the year 2017 in the southeastern intensive air quality monitoring station of the National Institute of Environmental Research, Korea. This study identified and investigated the time periods during which the vanadium content in PM2.5 was higher than the annual mean (1.026 ng/µg) through selection cases (SCs). The annual mean concentrations of PM2.5 and PM10 were 18.50 and 32.35 µg/m3, respectively, and were higher (i.e., 26.54 and 45.84 µg/m3, respectively) in SCs. Notably, the concentrations were high even when the main wind direction of SCs was southeasterly, which was mainly the case in summer. Furthermore, the emission sources contributing to PM2.5 were estimated using the correlations of organic carbon, elemental carbon, zinc, iron, manganese, and titanium concentrations in the SCs. This study demonstrated that a detailed tracking of the emission sources at a local scale is possible by analyzing the composition of the components of PM2.5.

Concentrations of trace substances in sewage sludge from 28 wastewater treatment works in the UK

Concentrations of trace substances in sewage sludge have been measured in a survey of 28 wastewater treatment works (WwTWs) in the UK carried out over a period of 12months. Approximately 250 samples were analysed for more than 40 trace contaminants, including trace metals, pharmaceuticals, polycyclic aromatic hydrocarbons (PAHs), ‘emerging’ and regulated organic pollutants. All substances investigated were found to be present in at least some of the sludges sampled. Concentrations were relatively homogenous across all the WwTWs, irrespective of the treatment process, influent and effluent concentrations, and the location of the sludge sampling point within each works. Analysis of the results against existing regulatory and proposed thresholds suggested that levels are mostly below the limits set in the Sewage Sludge Directive, and proposed new limits for sludge used in agriculture. Predicted soil concentrations after application of sewage sludge to land were below the predicted no effect concentrations (PNEC) for all determinands. Predicted concentrations of pharmaceuticals in soil were also below thresholds deemed to indicate negligible environmental risk.

The impact of ground-level fireworks (13 km long) display on the air quality during the traditional Yanshui Lantern Festival in Taiwan

In this study, the concentrations of CO, non-methane hydrocarbons, NO(X), SO(2), benzene, toluene, ethylbenzene, xylene (BTEX), PM₁₀, and PM₂.₅ were continuously monitored before and after the fireworks display during the traditional Lantern Festival from March 2-7, 2007 in Yanshui Town, Taiwan. Major roads in Yanshui Town were surrounded by fireworks 13 km in length, with the display lasting for 45 min. More than 200 small firecracker towers popped up randomly in town, resulting in exceedingly inhomogeneous air quality until the end of display at 03:00 the next day, March 5. During the fireworks display, the hourly concentration of PM₁₀ and PM₂.₅ at Yanshui Primary School reached about 429 and 250 μg m⁻³, respectively, which is 10 times the normal level, and 6 s values even went as high as 1,046 and 842 μg m⁻³, respectively. Similarly, BTEX concentration went up to about five to 10 times its normal value during the fireworks display. As indicated by the distribution of submicron particle sizes, the number of particles with a diameter less than 100 nm increased abruptly during the event period. Metal components with concentrations of more than 10 times higher than the normal value at Yanshui Primary School were Sr, K, Ba, Pb, Al, Mg, and Cu, in sequence. Among water-soluble ions, the content of K( + ), Mg²( + ), and Cl( - ) increased the most, all of which were related to the materials used in the fireworks. The results of this study indicate that fireworks can cause an abrupt increase in the concentration of trace substances in the air within a short period. Although the risks of these trace substances on public health remain to be further assessed, the study results can be utilized in the management of folk events.

Deposition of trace substances via cloud droplets in the Atlantic Rain Forest of the Serra Do Mar, São Paulo State, SE Brazil

The Atlantic Rain Forest of the Serra do Mar close to Cubatão, São Paulo State, SE Brazil, is severely affected by the emissions of a big industrial complex. Measurements of trace substance concentrations in air as well as in rain were carried out over a period of 6 years to investigate the interrelation of pollution and vegetation damage. Due to the local atmospheric circulation, orographic clouds occur very frequently at the top of the Serra do Mar, where vegetation damage also is very high. Therefore, additional information was required about trace substance deposition via cloud water. During three field experiments, various samples of cloud water and of the interstitial aerosol were taken by help of a sampling device especially modified for this purpose, and were analysed for the major anions and cations (hydrogen ions, ammonium, chloride, sodium, nitrate and sulphate). The trace substance concentrations found in cloud water were in the same range as for polluted sites in Europe. Over all samples, about 90–100% of the trace substances—both gaseous and particulate matter—found in the atmosphere before a cloud event were found in the cloud water. A resistance model using meteorological input data (wind speed, atmospheric liquid water content) was adapted to the characteristics of the Atlantic Rain Forest to estimate the cloud water deposition to vegetation. The results from cloud water analyses and from modelled cloud water deposition were combined to investigate the ion deposition to the vegetation. A rough estimate of the annual deposition showed, that the deposition via rain is in the order of one magnitude (factor 6–40) higher than that via cloud. The high amount of water deposition via precipitation overcompensates the higher trace substance concentrations in cloud water. Furthermore the trace substance deposition to vegetation via cloud water in the Atlantic Rain Forest is in the order of one magnitude lower than for typical German spruce forests due to the higher capture efficiency of the needles compared to that one of the leaves in the Serra do Mar.

Atmospheric Deposition of Chemical Contaminants to the Great Lakes

The contamination of air and water by persistent toxic substances is one of the most important environmental issues confronting the Great lakes region. The atmospheric transport and deposition of chemical contaminants is a dominant source for many of these chemicals, but accurate estimates of the fluxes have been elusive. Data for the concentrations of trace substances in the various environmental compartments are scant, and several of the important transfer processes are not fully understood. A major research initiative is needed to calculate the atmospheric fluxes of chemical contaminants with an acceptable degree of uncertainty.

Principal component analysis of trace substance concentrations in rainwater samples

A total of 197 bulk precipitation samples from different rural and suburban stations in Bavaria, F.R.G., were analysed for the following trace substance concentrations: PAH (fluoranthen, benzo-ghiperylene, benzo-a-pyrene), chlorinated hydrocarbons (α- and γ-BHC, HCB, PCB) and trace metals (Zn, Cd, Pb, Cu, Fe). Data analysis was carried out with multivariate principal component analysis separately for suburban and rural sites, and for summer and winter events. The resulting principal component loadings matrices are characterized by typical patterns indicating differences of the emission of the single pollutants in their temporal and spatial distribution. PAH and Pb are concentrations parameters for the interpretation of the data structure of suburban sites. While Pb concentrations are elevated in the rainwater samples of these stations during all seasons, PAH indicate space-heating by showing elevated levels during winter. Rural sites are characterized by a lower interrelation between the various parameters and chlorinated BHC pesticides as further pollution variables. These substances are highly enriched in rainwater samples from spring and summer events.

Comparison of regional and temporal trace substance distribution in bulk precipitation and atmospheric dust

Mean concentration values of PAH (1.12-benzoperylene, 3.4-benzopyrene, fluoranthene), trace metals (Zn, Pb, Cu, Fe) and γ-BHC in bulk precipitation and atmospheric particulate matter from 20 sampling stations in Bavaria (G.F.R.) were used for a multivariate regional classification of air pollution sites. For this purpose a cluster analysis with Ward's algorithm was chosen. The results of the cluster analysis show a number of pollution classes with distinct trace substance patterns. A further characterisation of these pollution classes could be reached by analysis of temporal trace substance concentrations in the atmosphere.

Caged Fish for Estimating Concentrations of Trace Substances in Natural Waters

This paper attempts to establish a theoretical background for using caged fish as estimators of concentrations of biologically accumulable trace substances in natural waters. The major motive for using this monitoring technique is that, for most trace substances only a certain, and usually unknown, fraction of the total concentration can be expected to be biologically available and that, therefore, conventional analytical methods may yield values that are biologically irrelevant. It is shown that, in general, if (i) the metabolic rate of the experimental fish is constant, (ii) the turnover factor of the trace substance in the fish is numerically known and either constant or numerically small, and (iii) the efficiency of oxygen withdrawal is constant and numerically known, caged fish can be used to estimate the mass concentration (relative to oxygen) of accumulable trace substances in the ambient water. As illustration, the concentration of methyl mercury that is biologically available in a lake is estimated, yielding figures of the order of 1 ng l-−1. The precision problem is discussed with regard to optimal experimental design and selection of experimental fish.

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

Potential trophic biomasses and trace-substance concentrations in unstructured marine food webs

It is proposed that unstructured food webs may more closely resemble real marine food webs than does the conventional, structured model. An unstructured food-web model leads to a set of very simple expressions for the potential partition of matter in the food web in steady state, including the potential fluxes of material and biomasses of trophic types and the concentration of trace substances in the members and materials of such a food web. The approach may explain some anomalies of relative predator-prey biomasses and of trace-element distribution, and may be of further use for analyzing and predicting (a) the tropho-dynamic parameters of marine systems, (b) the trophic positions, and the steadystate fluxes and biomasses of marine organisms, (c) the distribution of trace materials in marine biota; and for relating findings among these areas. Other matters, such as limitations of food conversion, indicated by concentration factors of trace substances, the possibilities of non-causal association of anomalously high levels of trace substances (including pollutants) with diseased or otherwise abnormal marine creatures, and an inverse relationship of early concentrations of newly introduced trace substances and their eventual concentrations in various organisms, are also developed in this approach.

Eddy transfer processes in the stratosphere during major and “minor” breakdowns of the polar night vortex

An analysis of the large-scale eddy processes which may be responsible for the northward and downward transport of trace substances in the stratosphere is performed for cases of a major and a “minor” breakdown of the polar night vortex. By using vertical velocities obtained from the thermodynamic equation, eddy covariances between the vertical velocity and the northward component of the wind were computed on a daily basis for middle and higher latitudes. The results indicate that this quantity reverses very rapidly from positive to large negative values just after the major breakdown of the polar vortex, thus providing an efficient mechanism for northward and downward trace substance transport at this time of the year. This result is also corroborated through large-scale trajectory calculations. A similar analysis is performed for a fall period in which the intensifying polar vortex circulation deforms into a regime dominated by large-scale cyclones and anticyclones (“minor” breakdown), but then reforms into an intense midwinter polar vortex. This situation also appears to be favorable for northward and downward transport, but the processes are considerably weaker than for the major breakdown case. This result may indicate why the largest buildup of trace substance concentrations in the high-latitude lower stratosphere occurs during late winter and early spring.