Search

A novel method based on conversion of chlorinated volatile organic compounds (CVOCs) to chlorine using a new type of column packed with nanometer Ti[O.sub.2] coupled with chemiluminescence (CL) has been developed for determination of them in workplace air. CVOCs are converted to chlorine by nanometer Ti[O.sub.2] at 220[degrees]C. The [Cl.sub.2] that is produced is selectively enriched on the column and subsequently released from the column at 600[degrees]C. The [Cl.sub.2] that is released is determined using a postcolumn CL detector. The CL intensity was linear with C[Cl.sub.4] in the range of 0.1-380 ppm, and the detection limit was 40 ppb (S/N = 3). Higher sensitivity could be acquired by using a larger volume of enrichment. A similar procedure could be used for the determination of other CVOCs. CL intensities of C[H.sub.2][Cl.sub.2], CH[Cl.sub.3], and C[Cl.sub.4] at the same concentration increased in the order C[H.sub.2][Cl.sub.2] < CH[Cl.sub.3] < C[Cl.sub.4]. The method has been successfully applied to the determination of C[Cl.sub.4] in workplace air, where 0.15-150 ppm C[Cl.sub.4] would be detected. The possible mechanism for the long lifetime of the column packed with nanometer Ti[O.sub.2] was tested using Raman spectrometer, X-ray powder diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The results showed that the column packed with nanometer Ti[O.sub.2] could be operated in the reversible mode for determination of CVOCs under the present conditions. The method would be potentially applied to the analysis of other chlorinated compounds in environment, such as persistent organic pollutants.

In many water quality model applications to real networks, it has been observed that the chlorine concentrations at nodes on the secondary pipes with long residence times do not compare well with the model predictions. Therefore, it is important to better estimate the correct chlorine contents of outer nodes in order to determine the dosing time and the amount of chlorine during secondary chlorination. A model is developed for evaluating chlorine decay in drinking-water distribution networks. The model uses a simplified two-dimensional expression of a chlorine transport and decay equation within a single pipe that includes the bulk-flow reaction, radial diffusion, and pipe-wall reaction of chlorine. The computer program DYNAQ developed in this study, which tracks chlorine transport and decay using a time-driven approach, is also applied to the chlorine measurements taken from a portion of the South Central Connecticut Regional Water Authority's service area. A comparison of the results of the model with those of a previously developed model is also included in this paper. DOI: 10.1061/(ASCE)0733-9372(2002)128:1(31) CE Database keywords: Simulation; Chlorine; Potable water; Decay; Water distribution; Water supply.

A spray coated thin film of all-E-poly[(3-methoxy-2,5- thiophenediyl- l',2' -ethenediyl)(4' -methoxy -2', 5'- thiophenediyl- l',2' -ethenediyl)], a conducting polymer, was analyzed by grazing emission X-ray fluorescence spectrometry. Measuring the S/CI ratio in this sulfur-containing polymer with one terminal chlorine allowed us to determine the chain length and, hence, the molecular weight. The result was in acceptable agreement with that of a well-established method for the determination of the molecular weight of polymeric materials.

A number of computer packages have been developed for modeling chlorine decay in water distribution networks. However, there is uncertainty as to the kinetic model that they should use for the decay mechanism. This paper explores the performance of six different kinetic models for the decay of free chlorine in over 200 bulk water samples from a number of different sources. The paper also presents the results of surveying the longitudinal decay profile of free chlorine in two in situ pipe stretches. It concludes that, for network modeling purposes, it is generally reasonable to assume first-order kinetics for bulk and overall decay.

The hydrogen and chlorine abstraction reactions by silyl (H3Si*) and trichlorosilyl (Cl3Si*) radical from the three chloromethanes ClCH3, Cl2CH2 and Cl3CH were investigated theoretically. Findings from traditional ab initio techniques were compared with those derived from a density functional method using the hybrid B3LYP and the pure BLYP functional. Results at all computational levels showed that the chlorine abstraction is highly preferred with respect to the hydrogen abstraction as experimentally observed.

A study on the chlorine channel of the OClO fragmentation was conducted to show that three-photon laser-induced fluorescence and total vacuum ultraviolet fluorescence can be used for the 'soft' identification of the new Cl atoms. These techniques do not require secondary photolysis processes resulting from high-energy photons. This study also aimed to use the method to examine the mode-selective degradation of OClO into Cl atoms.

Two methods have been used to measure the chlorine leaving group kinetic isotope effect for the [S.sub.N]2 reduction of benzyl chloride to toluene by sodium borohydride in DMSO at 30.000 [degrees] C. The reaction was monitored by titrating the unreacted borohydride ion. One method involved determining the chlorine isotope effect using the classical IRMS method, which requires the conversion of the chloride ions into gaseous methyl chloride that is analyzed in an isotope ratio mass spectrometric analyses (Hill, J. W.; Fry, A. J. Am. Chem. Soc. 1962, 84, 2763. Taylor, J. W.; Grimsrud, E. P. Anal. Chem. 1969, 41, 805.). Two different measurements using this method yielded isotope effects of [k.sup.35]/[k.sup.37] = 1.007 19 [+ or -] 0.000 19 and 1.007 64 [+ or -] 0.000 19. The second method was a new technique where the ratio of the chlorine isotopes was obtained by fast atom bombardment mass spectrometry on the silver chloride recovered from the reaction, i.e., from the first step in the classical procedure. Therefore, the new method is much simpler and avoids the time-consuming preparation, purification, and recovery of the gaseous methyl chloride. Although the experimental error is larger ([k.sup.35]/[k.sup.37] = 1.008 03 [+ or -] 0.00 10 and 1.008 02 [+ or -] 0.000 65) when the new technique is used to analyze the silver chloride samples from the same set of experiments that were used to measure the isotope effect by the classical method, the chlorine isotope effect found by the two methods is identical within experimental error. This large chlorine kinetic isotope effect indicates there is considerable [C.sub.[Alpha]]-Cl bond rupture in the [S.sub.N]2 transition state.

The reaction rate parameter uncertainties in the chlorine partitioning and ozone in upper stratospheric models was investigated. A direct sensitivity analysis was used on local altitude boxes from the LLNL-2D model. Sensitivities were utilized to propagate rate constant errors through the model and to isolate those steps that are predominant in the uncertainties in the computed concentrations. The reaction OH + ClO -> HCl + O2(1Delta) was confirmed to the key source of uncertainty in chlorine partitioning in the 2-D atmospheric model.

Absolute rate coefficient measurements were performed for the Cl atom reaction with a series of esters at room temperature and in the pressure range 15-60 Torr by applying the laser photolysis-resonance fluorescence method. The reactivity of Cl with the investigated esters can be compared with the reactivity of OH radicals with the same esters. The Cl and OH reaction rate coefficients indicated similar trends with the number of carbon atoms and the branching in the esters as was shown for Cl and OH reactions with alkanes.

A study was conducted to analyze the tile reaction by monitoring the ethyl radical product using resonance-enhanced multiphoton ionization proceeding at 242 nm through highly dissociative Rydberg states. Core-extracted ion arrival profiles were determined with the photolysis laser polarization method. The measured C2H5 spatial anisotropy was then utilized to estimate the product center-of-mass velocity and change the speed distribution tot he differential cross area.

The a-Si:H(:Cl) films prepared at 300 degrees C was used in assembling a-Si:G(:Cl) thin film transistors (TFT) with [SiH2Cl2]/[SiH4]=0.04-0.12 to investigate the influence of the introduction of Cl in the operation of a-Si:H TFTs. The field effect mobility decreased and the threshold voltage increased with increasing [SiH2Cl2]/[SiH4]. On the contrary, the off-state leakage current significantly decreased with the introduction of Cl atoms into a-Si:H. The Cl in a-Si:H was observed to shift the Fermi levels in the direction of the valence band edge, thereby making the a-Si:H(:Cl) p type.

The effects of magnesium on the partitioning of fluorine and chlorine between biotite and melt were analyzed in a natural F-rich vitrophyric rhyolite from Spro Mountain, UT. Spectroscopic analysis of the Spor Mountain rhyolite indicated the presence of glass and biotite laths with fluorite, quartz and zircon. The presence of magnesium in the sample modulated halogen partitioning due to the reequilibration of degassed magma.

No relationship exists between the quantities of formed dibenzo-p-dioxins (PCDDs)/dibenzofurans (PCDFs) and chlorobenzenes (PCBzs) in the combustion process and chlorine concentration in the fuel, when the chlorine level is less than 1%. The formation rate increases, however, when the level of chlorine in the fuel exceeds 1%. These results were derived from a study of the formation of PCDDs, PCDFs and PCBzs in the combustion process where chlorine level and source were varied in an artificial waste.

Stable Cl isotope ratios, measured in marine pore waters associated with the Barbados and Nankai subduction zones, extend significantly (to [similar to] -8% per thousand) the range of [[Delta].sup.37] Cl values reported for natural waters. These relatively large negative values, together with geologic and chemical evidence from Barbados and Nankai and recent laboratory data showing that hydrous silicate minerals (i.e., those with structural OH sites) are enriched up to 7.5% per thousand in 37Cl relative to seawater, strongly suggest that the isotopic composition of Cl in pore waters from subduction zones reflects diagenetic and metamorphic dehydration and transformation reactions. These reactions involve clays and/or other hydrous silicate phases at depth in the fluid source regions. Chlorine therefore cannot be considered geochemically conservative in these systems. The uptake of Cl by hydrous phases provides a mechanism by which Cl can be cycled into the mantle through subduction zones. Thus, stable Cl isotopes should help in determining the extent to which Cl and companion excess volatiles like [H.sub.2]O and C[O.sub.2] cycle between the crust and mantle.

Examination of the xerographic properties of chlorine-doped amorphous selenium reveals that chlorine enhances dark decay rate, reduces acceptance voltage and residual voltage after corona charging and illumination, respectively. Depletion discharge was the main process in the reduction of dark decay voltage. An increase in chlorine level causes a reduction in release time of holes and an increase in hole capture time.

The determination of transient chlorine concentration profiles and chlorine insertion in biofilms consisting of Klebsiella pneumoniae and Pseudomonas aeruginosa during disinfection by using a microelectrode reveal that chlorine concentrations in biofilms are less than that in bulk liquid and that the diffusion of chlorine in the matrix of the biofilms controls chlorine insertion. The region of chlorine insertion exhibits an overlapping with the nonrespiring areas. The controlled insertion of chlorine into the biofilms may be responsible for the reduced effectiveness of chlorine against the biofilms.

2-hydroxy-3-chrolobiphenyl constitutes the axenic methanotrophic culture strain CSC1 yielded by mixed-culture aquifer samples. The sample oxidized to hydroxylated chlorobiphenyl intermediates by 2-chlorobiphyenyl indicates its constituent compounds. The axenic incubation culture extracts also exhibit hydroxylated chlorobiphenyl isomer.

9-azabicyclononanes 2 and 3 can be prepared by transannular N-heterocyclization of 1,5-cyclooctadiene which employs B-bromo- or N-iodosuccinimide and cyanamide. This method is unsuccessful when N-chlorosuccinimide was used. Dehydration of the carboxamide after nucleophilic displacement with chlorine affected the preparation of chloro-substituted derivative.

Heat and chlorine influence the survival of Hartmannella vermiformis and the successive intracellular development of Legionella pneumophila. For chlorine concentration between 2 ppm and 4 ppm, H. vermiformis trophozoites are slightly affected by chlorine. There is a decrease in the concentration of H. vermiformis at 50 degrees Celsius and chlorine concentration of 2 ppm. The two organisms do not survive at a concentration of 10.0 ppm and a temperature of 60 degrees Celsius.

Photoinduced current transient spectroscopy (PICTS) is used to determine the effects of growth methods on compensation defects in samples of CdTe:Cl. At temperatures between 100 and 140 Kelvin, three distinct traps lead to PICTS signal in every CdTe:Cl sample. A cross section and an activation energy, which is almost similar for the various samples, results from only one trap.

We have examined quantum yields for chlorine production from solar photolysis of acidic chloride solutions containing the hexachloroiridate (IV) complex, IrCl2-6. Previous investigators found good quantum yields in the middle UV (Phi(Cl2) = 0.128 at 254 nm), but the yield was found to decrease in the near UV, falling to zero at wavelengths above 488 nm. Under solar photolysis, we find nearly zero yields in closed or static systems. However, when the chlorine produced is swept out with an inert gas, Phi(Cl2) under solar photolysis is approximately 0.0018, for a solution containing 0.001 M IrCl2-6 in 6 M HCl solution. Improvements in the quantum yield result from increasing the IrCl2-6 concentration from 0.001 M to 0.1 M or higher and from increasing the Cl- concentration from 1 M to 5 M; solutions were acidic in all cases. Using a solution of 0.025 M IrCl2-6, 0.5 M HCl, and 5 M NaCl, Phi(Cl2) = 0.0070 was found. Further improvement in the yield is achieved if the hexachloroiridate (III) produced is simultaneously oxidized back to hexachloroiridate (IV) while photolysis is in progress. Under the best conditions of simultaneous photolysis and electrolysis, a chlorine quantum yield of 0.080 is found for solar light between UV cutoff (ca. 320 nm) and the maximum actinic wavelength of the IrCl2-6/Cl- system, at 488 nm.

Experiments were conducted to analyze the uptake of chlorine, without chloride ion, by chicken frankfurters immersed in labeled solutions of water containing 1.1 to 11.3 mM hypochlorite, with and without the processing casing wrapped on the outside. Chlorine uptake was positively related to hypochlorite concentration of immersion solution and immersion time.

Halide-sensitive fluorescent dye 6-methoxy-N-(3-sulfopropyl)quinolinium (SPQ) was employed to study the secretion of epithelial cells in colonies of Lieberkuhn and the alteration made in chlorine permeability by these secretions. Increases in SPQ fluorescence produce a corresponding reduction in intracellular chlorine concentrations. This proves that several cells were unresponsive to these secretions. Those that were responsive also revealed increased chlorine permeability in the course of stimulated ion secretion.

Mo K-alpha X-radiation is used to refine the R indices of approximately 2% of the crystal structure of three calcil c2/m amphiboles with different chlorine contents. Two distinct sites, O3 and O3', are separated by approximately 0.5 angstroms and are split by the monovalent anion site. A strong preference for Fe2+-Cl short-range order is seen in the variations in bond lengths, as a function of cation and anion site populations. A concomitant expansion of the tetrahedral chain occurs partly by chain straightening but mostly by the increased substitution of (4)Al for Si. This is required by the expansion of the octahedral sheet caused by the incorporation of chlorine. Increasing Fe2+, K and /4~Al are required by the increasing chlorine content in the amphiboles.

The utilizatiion of chlorine as a tracer of subsurface-water dynamics is discussed. This involves the measurement of chlorine-36 in a suite of water samples from the eastern Snake River Plain aquifer and in the vicinity of the Idaho National Engineering Laboratory. Evidence supporting the theory of the occurence of chlorine releases at all nuclear fuel reprocessing facilities is advanced.

The combined usage of a chemical vapor generator and an on-line microwave-induced plasma-Surfatron atomic emission spectroscopy system allowed the rapid and direct analysis of halogens in aqueous solutions. The continuous formation of halogens which included chlorine, bromine and iodine from aqueous solutions required the utilization of a lead dioxide oxidizing column attached to an argon plasma source through a gas-liquid separator. The technique gave highly sensitive halogen determinations even in synthetic mixtures of halides.

We have used [sup.36.CL] to date climatically sensitive saline-lake sediments from hydrologically closed basins in southeastern California, primarily sediments from Searles and Panamint basins. During wet periods of the past 2.0 m.y., lakes that formed in the closed basins fluctuated in size in direct respinse to the balance between runoff and evaporation. We have compiled a chronology for the KM-3 core from Searles Lake, based on ages determined by [sup.36.CL] for the evaporites, together with those determined by [sup.14.C] and U-Th series for younger sediments, and by magnetostratigraphy for older sediments. This chronology, along with other criteria, such as correlations between Searles and Panamint basins, the chloride budget, and sedimentology, is used to reconstruct the history of lake fluctuations in the paleo-Owens River system. We infer that Searles Lake desiccated at most twice since 600 ka: during the interval around 290 ka, and from 10 ka to the present. The lake history curve shows that the Holocene Epoch is anomalously arid. Major overflows from Searles to Panamint occurred during the intervals between 1.3 Ma and 1.0 Ma, 750 ka and 600 ka, 500 ka and 400 ka, and 150 ka and 120 ka. Comparing the lake-fluctuation chronology to the [[delta]sup.18.O] record of marine foraminifera, we infer that the strongest similarity is in the periodicities of the cycles-40 to 50 kyr before the Matuyama/Brunhes magnetic reversal (730 ka) and 100 kyr thereafter. We find, however, that at Searles Lake this fluctuation in the lake chronology is modulated by longer-term cycles of aridity and humidity. Thus, although the mid-latitude Quaternary climate record reflects the mid- to high-latitude ice-volume fluctuations that dominate the marin [sup.18.O] record, it also contains evidence for climatic forcing of a different type.

The sensitivity to free chlorine of feline calicivirus (FCV), a norovirus surrogate with respect to the chlorine demand is studied. The analysis reveals that the sensitivity of FCV to free chlorine increases with a reduction in the host cell debris.

The geometry and vibrational frequencies of the GdX3 (X = F and Cl) molecules are analyzed at the ab initio level with extended basis sets, employing relativistic effective core potential, and evaluating electronic correlation by means of second-order perturbative (MP2) and coupled cluster (CCSD and CCSD(T)) methods. Anharmonicities, temperature and inert-gas matrix effects are explicitly included in the study.

A systematic study of Cl doping in ZnTe homoepitaxial layer grown by MOVPE (Metalorganic Vapor Phase Epitaxy) using n-butylchloride is investigated. The effects of Cl doping on the photoluminescence (PL) properties are discussed.

A model that directly determines the required source concentration(s) to meet specified chlorine residuals at selected nodes is developed for unsteady flows. The model considers even, over-, and underdetermined cases in which the number of available equations is equal to, greater than, or less than the number of unknowns, respectively. The model computes the unsteady-state flows and chlorine concentrations in the system first. Then it utilizes the inverse method to determine the required source concentration(s) so that specified residuals at selected nodes match the calculated ones. To verify the model, chlorine concentrations computed by the forward method are input to the inverse model to determine the source concentration(s) in two hypothetical networks. Results show that the model computed accurately the source concentrations for the even and the overdetermined cases, but the results were less than satisfactory for the underdetermined case.

Investigations of the metabolite (pm)-(1beta,6alpha,9beta, 10alpha)-9-chloro-10-hydroxy-8-(methoxycarbonyl)-4- methylene-2, 5-dioxabicyclo-(4.4.0)dec-7-en-3-one (1), accomplished the total synthesis of racemic 1 by the lactonization of diester 3, which was obtained from dimethyl chorismate. 1 is a chlorine-containing metabolite that was isolated from various fungi.

The estimated quantum yield for the solid-state reaction of chlorine with methyl cyclopropane is affected by the use of an external magnetic field during photolysis. In the adiabatic link, relaxation between spin-orbit states of heavy atom radicals takes place exclusively because of other disturbances such as rotation of the radicals. Reasons for the large magnetic effect with reaction of Cl atom pairs are suggested.

Chlorine is used in swimming pools to maintain algae growth to a minimum and to prevent the growth of bacteria. However, chlorine has been found to wear down swimsuit fabrics [...]

A study investigated the branching ratio of the reaction of OH with ClO conducted at pressures between 100 and 200 Torr and at a range of temperatures extending to those found in the lower stratosphere using a novel, laboratory-developed technique. It also conducted statistical rate theory calculations on the OH + lO reaction system. Experimental and theoretical calculations were compared. Experimental methods, findings and conclusions are discussed.

Fourier transform infrared-smog chamber methods were employed to assess the rate constants for the gas-phase reaction of Cl and F atoms with CH3C(O)C(O)CH3 and F atoms with CH3C(O)F. Two pathways for the reaction of Cl and F atoms with CH3C(O)C(O)CH3 were observed. Pulse radiolysis in combination with ultraviolet absorption spectroscopy was employed to investigate the kinetics of the reaction of F atoms with CH3C(O)C(O)CH3.