Chlorinated Hydrocarbon Solvents Research Articles

Determination of chlorinated hydrocarbons in water by fiber-optic evanescent wave spectroscopy and partial least-squares regression

An application of the multivariate calibration technique of partial least-squares (PLS) regression to near-infrared spectra of a fiber-optic sensor based on the evanescent wave principle is presented. The sensing element consists of a quartz glass fiber with a silicone cladding which enriches nonpolar water contaminants. Due to the interaction of the extracted molecules with the part of the light which is transmitted in the evanescent wave zone of the cladding, absorbance spectra of the contaminants can be collected. In view of a sensor application for in-situ environmental analysis, aqueous solutions of chlorinated hydrocarbon solvents (CHS), which often can be found as major water contaminants, have been measured. PLS regression was applied to three sets of CHS samples, representing typical features of NIR evanescent wave spectral data. These are, e.g., strong overlapping of the absorption bands of different CHS components, peak distortions due to temperature variations between reference and sample measurement and noisy data at analyte concentrations near to the limit of detection, respectively. For trichloroethene and 1,1-dichloroethene, where the calibration model was built for samples within a small concentration range of 1–9 mg l−1, satisfactory prediction results could be obtained with a relatively small root-mean-square error of 0.3 mg l−1 compared to analytical reference measurements. In contrast to this, for a three component system of dichloromethane, trichloromethane and trichloroethene with strongly overlapping absorption bands, where samples over a very broad concentration range from 3–4940 mg l−1 were included in the PLS model, the prediction accuracy decreased enormously and for some samples strong deviations between real and predicted data occurred. Nevertheless, applying multivariate calibration to this difficult system with similar spectral features and huge differences in the concentration of the species allowed an acceptable spectral distinction and at least a semi-quantitative determination of the CHS species.

One-drop flame atomic absorption spectrometry of metals using direct nebulization of chlorinated hydrocarbon extracts of metal chelates

The flame atomic absorption spectrometric behaviour of metals extracted into non-flammable chlorinated hydrocarbon solvents (dichloromethane, chloroform and carbon tetrachloride) as their neutral chelates or as ion-paired complexes was studied by a one-drop method with direct nebulization of small volumes of organic extracts and with deuterium background correction. Direct nebulization of organic extracts into a fuel-lean air-acetylene flame gave interesting background-corrected signal profiles, depending on the metals and not depending on extraction agents and solvents. The signal profiles were roughly correlated with the charring and atomizing temperatures of the metals in electrothermal atomic absorption spectrometry and with the dissociation energies of the metal monoxides. Direct nebulization into a dinitrogen oxide-acetylene flame gave a simple signal profile, not depending on the metals. Direct injection of 20–40 µl aliquots of organic extracts of Co, Cu, Fe, Mg, Mn and Ni chelates into an air–acetylene flame gave the maximum, constant and reproducible spike-like signals. Direct nebulization of about 50 µl of organic extracts of Ag, Cd, Pb and Zn chelates also gave very sensitive spike-like signals, compared with those obtained by nebulization of aqueous metal solutions. With the combined use of extraction concentration, this small injection volume of less than about 60 µl resulted in a very sensitive and reproducible flame atomic absorption spectrometric determination of trace amounts of Ag, Cd, Pb and Zn in solid samples without deuterium background correction.

Chlorinated hydrocarbon solvents: Substituting our way toward human carcinogenicity

A discussion of the history of substitutions in industrial solvent use is presented, and animal carcinogenicity studies with certain chlorinated hydrocarbon solvents are reviewed. The present knowledge on the association between occupational exposure to chlorinated hydrocarbon solvents and human carcinogenicity is summarized, including a critical review of 23 studies pertaining to human carcinogenicity. Several deficiencies are identified in these studies that make interpretation of the results uncertain, including poor characterization of exposures in qualitative and quantitative terms, the small numbers of deaths or cases, and short follow-up periods. Despite these weaknesses, we conclude that, when viewed collectively, the evidence strongly suggests that occupational exposures to chlorinated hydrocarbon solvents are associated with an excess human cancer risk. The literature supports an association between occupational exposures to chlorinated hydrocarbons and elevated risks of leukemia, lymphoma, and urinary tract cancer. Parental occupational exposures are consistently associated with an elevated childhood cancer risk in the offspring.

Pollution of groundwater in the Coventry region (UK) by chlorinated hydrocarbon solvents

Groundwater quality in the Coventry aquifer system was surveyed using the 42 accessible boreholes. Pollution by chlorinated hydrocarbon solvents (CHSs) is widespread in the urban area, with trichloroethene being the major pollutant. CHS pollution is closely associated with industrial land use, except for trichloromethane which appears to be linked to leakage of chlorinated water from water mains and sewers. Modelling studies suggest that most of the urban groundwater is already polluted by dissolved CHSs, and that natural flushing of the aquifer will take hundreds of years. Inorganic pollution has also occurred in the urban area, and is linked mainly to leakage from sewers, in contrast to most CHS pollution. Little, if any, degradation of CHSs is taking place in the aquifer, and pollution continues; the poor quality of Coventry groundwater will, therefore, persist for the foreseeable future.

Postscript: summary of the Coventry Groundwater Investigation and implications for the future

The broader implications of the Coventry Groundwater Investigation are discussed in this postscript. The complex interbedded sandstone and mudstone sequence under Coventry is seriously polluted by chlorinated hydrocarbon solvents. Investigations in such terrain will require much greater expenditure than was available for this project if they are to describe the distribution and movement of pollutants in enough detail to evaluate, quantitatively, options for aquifer clean-up. It is not realistic to consider clean-up of Coventry's groundwater at the present time because of the lack of detailed knowledge. It is probable, at least for the present, that clean-up is not feasible, because of hydrogeological constraints arising from the extreme variability of permeability in the system and an absence of operational techniques for clean-up. Stronger, more pro-active protection of groundwater is needed. A major recommendation for future investigations is a procedure to avoid open boreholes, which can allow pollution to penetrate deeper into the aquifer, and may confuse the results of sampling.

Extended Poly(Phenylquinoxalines) Containing Earbonyl and Sulfide Connecting Groups

Novel poly(phenylquinoxalines) (PPQs) containing carbonyl and sulfide connecting groups between the aromatic rings were prepared by condensation of various aromatic bis(o-diamines) with novel extended bis(phenyl-1.2-diketones) in m-cresol. An objective of the work was to determine the effect of replacing oxygen by sulfur in extended PPQs. The polymers prepared were soluble in m-cresol, dimethylsulfoxide, N,Ndimethylacetamide, 1-methyl-2-pyrrolidinone and chlorinated hydrocarbon solvents, and had inherent viscosities as high as 1.23 dl g-1. The PPQs exhibited glass transition temperatures ranging from 217 to 245 C and polymer decomposition temperatures (10% weight loss) as measured by thermogravimetric analysis of 526-568 in air and 510-549 CC in helium. A tough transparent yellow fingernail creasable film with a tensile strength of 94.7 MPa, a tensile modulus of 2562 MPa and elongation at break of 6.4% at 25 "C was cast from a chloroform solution of the polymer prepared from 1,3-bis(phenylglyoxalyl-4phenylthio-4'-benzoyl)benzene and 3,3'-diaminobenzidine. Little difference in properties was observed in the PPQs prepared as compared to the PPQs containing carbonyl and ether connecting groups between the aromatic rings, in spite of the difference in the bonding characteristics of carbon to sulfur and to oxygen.

Migration of chlorinated hydrocarbon solvents through Coventry sandstone rock columns

The migration in the Coventry sandstone aquifer system of aqueous solutions of various chlorinated hydrocarbon solvents (CHSs) (1,1,1-trichloroethane (TCA), trichloroethylene (TCE) and tetrachloroethylene (TeCE)) was studied by means of percolation experiments with undisturbed rock cores. The retardation factor ( R f) was very low (always less than 2 for TCA, less than 3 for TCE and less than 5 for TeCE). The R f varied slightly according to the nature of the solid sample but could not be related to the solid organic carbon content. The solvent adsorption was always almost completely reversible and little affected by the percolation flow rate (0.08–0.56 m day −1). The CHS breakthrough curves were typical of non-equilibrium processes (caused by sorption by the solids and possibly by diffusion between mobile and immobile water). The R f values obtained experimentally were much lower than those calculated from batch adsorption studies, showing that percolation experiments are necessary to evaluate the filtering properties of consolidated rocks. These results indicate that in the Coventry sandstone aquifer (relatively high vertical and, especially, lateral hydraulic conductivities), two-carbon CHS aqueous solutes should migrate readily with water with very little retardation.

Preparation of Di- and polynitrates by ring-opening nitration of epoxides by dinitrogen pentoxide (N 2O 5)

Eighteen epoxides of various kinds were reacted with N 2O 5 in chlorinated hydrocarbon solvents (principally CH 2Cl 2) to give vicinal nitrate ester products by a novel ring-opening nitration reaction. The procedure offers easier temperature control and simpler isolation procedures compared with conventional mixed acid nitrations; it also enables selective nitration reactions to be carried out on polyfunctional substrates. The scope and limitations of the reaction, as well as those of an alternative route utilising N 2O 4 with in situ oxidation of an intermediate nitrite-nitrate, are discussed.

Investigation of a solvent polluted industrial site on a deep sandstone-mudstone sequence in the UK. Part 2. Contaminant sources, distributions, transport and retardation

A single industrial site has been investigated in detail to gain information on sources and movement of chlorinated hydrocarbon solvent (CHS) pollutants in groundwater under the industrialized city of Conventry in the UK. A soil gas survey identified the most polluted area of the site where two types of investigation borehole were drilled; open boreholes lined with plain and slotted casing, and a single dedicated borehole incorporating gas samplers and gas-driven water samplers. Specially designed sampling techniques using pumps and packers were employed to determine vertical pollution profiles in the open boreholes. Core material was collected for sorption and diffusion experiments. An assessment of field investigation procedures suggests that soil gas sampling is a useful method for reconnaissance surveying of pollution by volatile organic compounds, but the results reflect only shallow pollution in the vertical profile. Open boreholes were found not to be satisfactory for accurate groundwater profile sampling and dedicated boreholes are recommended for such studies. Many uncertainties are involved in such a study of solvent pollution owing to the limited number of boreholes drilled and the complex spatial and temporal variations of pollutants. Despite the limitations of the investigation, several useful conclusions are drawn concerning sources and movement of solvent pollution. The main pollution source at the site is identified as the solvent storage tanks and pollution has resulted from poor use practices. Vertical pollution profiles indicate that the downward migration of 1,1,1-trichloroethane is following that of trichloroethene, reflecting their history of use on the site. The overall quality of groundwater abstracted in the system is set to deteriorate, as high pollution loads, presently at shallow levels in the system penetrate deeper, little attenuated by sorption or degradation. Diffusion of pollutants between mobile fissure and immobile pore waters will result in poor quality groundwater under this site for the foreseeable future. This trend is expected to be reflected throughout the urban area as a whole, with most groundwaters falling below drinking water standards for CHSs.

Hydrogeology of the Coventry region (UK): an urbanized, multilayer, dual porosity aquifer system

The Coventry Groundwater Investigation has researched the sources and movement of chlorinated hydrocarbon solvents in the groundwater system underlying the Coventry region. The hydrogeological scene is set in this paper as a basis for the other aspects of the investigation which are reported in the other papers in this volume. The deep, intercalcated sandstones and mudstones of the Permo-Carboniferous which underly the study area, behave as a multilayer aquifer, although individual aquifer units are not regionally extensive. The sandstone units are fractured and behave as dual porosity aquifers, with rapid tracer movement in fractures and diffusion into the low-permeability but porous matrix. The water balance of the groundwater system has changed from natural conditions because of man's influence. Although direct recharge has been reduced by the impermeable surfaces of roads and towns, substantial extra recharge arises in the urban areas from leaking water mains.

Investigation of a solvent polluted industrial site on a deep sandstone-mudstone sequence in the UK. Part 1. Site description and groundwater flow

The sources and subsurface movement of chlorinated hydrocarbon solvents have been investigated at an industrial site, as part of a wider study of groundwater pollution by these solvents in the area of Coventry (UK). This paper presents a description of the site and groundwater flow as a prelude to a second paper describing the distribution, transport and fate of pollutants. Both open boreholes and a single borehole incorporating a multilevel sampler were constructed, and pumping and tracer tests performed. The latter borehole was the most successful in defining hydraulic heads for individual aquifer units. The cyclic pumping of the production borehole was analysed using a computer model to gain hydraulic data for aquifer and aquitard units. The tracer test defined, qualitatively, the role played by matrix diffusion in solute transport within the dual porosity aquifer. It is concluded that horizontal groundwater flow is dominant along fissured, moderately permeable sandstone layers. The low permeabilities of mudstone layers maintain high vertical hydraulic gradients. Sorption of contaminants on to the aquifer matrix is likely to be low, owing to a low fraction of organic carbon. However, matrix diffusion will serve to attenuate peak concentrations of pollutants and stretch pollution pulses in time.

Preparation of di- and polynitrates by ring-opening nitration of oxetanes by dinitrogen pentoxide (N 2O 5)

Ten oxetanes bearing various substituents were reacted with N 2O 5 in chlorinated hydrocarbon solvents to yield 1,3-dinitrate esters ( I) by ring-opening nitration. The yields ranged from 73 to 88% for di-/trinitrates derived from oxetanes unsubstituted in the 2-position, to only 15 to 21% for oxetanes bearing such substituents. Although selective ring cleavage of oxetanes bearing non-hydroxylic substituents (epoxy (oxiranyl), spiro-oxetane and alkene) was not, in general, possible, selective nitration of hydroxyalkyloxetanes was achievable under the conditions employed to yield nitrato-methyloxetanes useful as precursors for energetic polyethers. A semi-quantitative reactivity comparison with representative epoxides indicated that the reactivity of oxetanes towards N 2O 5 was lower, as expected on account of their lower ring strain.

Urban Ground‐Water Pollution: A Case Study from Coventry, United Kingdom

AbstractA regional ground‐water quality survey from 28 wells in the Coventry area of the United Kingdom identified widespread ground‐water pollution. Chlorinated hydrocarbon solvents (CHSs) were detected at concentrations exceeding l microgram per liter (μg/I) in all industrial and public water supply wells within the urban area. Of the CHSs analyzed, trichloroethene was most ubiquitous and was also detected at the highest concentrations, reaching a maximum of 547 μg/I at the industrial “Site A” during this study. By comparison with CHS pollution, inorganic and trace element concentrations were elevated relative to assumed baseline levels only in some industrial wells. The limited extent of inorganic contamination may be due to (1) retention of pollutants within the unsaturated zone, (2) ground‐water mixing in wells, (3) ferric hydroxide precipitation resulting in heavy metal coprecipitation, and (4) sorption on sand grains coated with ferric hydroxide. For inorganic determinants, a pollution index was devised which ranked zinc and boron as primary indicators of inorganic contamination. Regionally, concentrations of CHS and inorganic determinants did not reveal any significant correlation with depth.

Effects of carbon tetrachloride and chloroform on bile acid transport in isolated rat hepatocytes: Relationship to elevated serum bile acids

The hepatotoxic effects of chlorinated hydrocarbon solvents have been well recognized for many years. More recently serum bile acids (SBA) have been considered as a sensitive indicator for the determination of liver dysfunction. However, changes in SBA could result from interference with hepatic transport processes. In this study, the effects of carbon tetrachloride (CCl 4) and chloroform (CHCl 3) on uptake and efflux of bile acids were examined in isolated rat liver cells to determine whether this may play a role in elevated SBA after CCl 4 or CHCl 3 treatment. Cholic acid (CA) and taurocholic acid (TC) were selected as representative bile acids known to enter hepatocytes by active transport. At none of the doses of CCl 4 and CHCl 3 investigated was there a significant change in cytoplasmic enzymes or intracellular K + release. CCl 4 and CHCl 3 were both found to cause a dose-related inhibition of uptake of CA and TC. Furthermore, CCl 4 and CHCl 3 were shown to increase the Michaelis constant ( K m ) but leave maximum velocity ( V max ) unchanged thus indicating competitive inhibition. The lowest doses of CCl 4 and CHCl 3 at which inhibition of initial uptake rate (V 0) occurred for CA or TC were found to be 0.5 μl/flask (0.07 m m) or 1.0 μl/flask (0.17 m m) in cell suspensions, respectively. The inhibition of uptake could be reversed 30 min after cessation of exposure to CCl 4. No chemical-induced interference of efflux for CA or TC was found in preloaded cells. These findings indicate that interference in bile acid uptake may be involved, at least in part, in the increases in SBA in dosed animals, or workers exposed to CCl 4, CHCl 3 and perhaps other chlorinated solvents.

Nitroxyl free radical enhancement of the forbidden O2(3Σ−g) ← O2(1Δg) radiative transition in chlorinated hydrocarbon solvents

Abstract Utilizing transient near-IR luminescence spectroscopy, we have shown that free radicals like TEMPO (2,2,6,6- tetramethylpiperidine-N-oxyl) increase the rate of the forbidden radiative transition of singlet oxygen in chlorinated hydrocarbon solvents. The quantum yield for emission has been shown to depend on the nature of the substituent group in the 4′ position. Concomitant with this effect is a slight high energy shift in the steady state singlet oxygen phosphorescence spectrum. Additional experiments with TEMP (2,2,6,6-tetramethylpiperidine) have shown that the nitroxyl group is necessary for this effect. Using the kinetic equations associated with a collision complex model, we have investigated a curve crossing (isophotic) point observed in the 1270 nm luminescence decays at various TEMPO concentrations. This information indicates that we are observing a contact complex characterized by a weak interaction energy and a short lifetime. We have also determined the conditions under which the isophotic point can be observed.

Hexamethyltetralin Preparations Effect of Methyltrioctylammonium Chloride on Solvent/Olefin Interdependency

Abstract The use of quaternary ammonium salts as co-catalysts in the AlCl3 catalyzed cyclialkylation of p-cymene, 2-chloro-2methylpropane, and 3,3-dimethylbutene-1 is reported. The addition of co-catalyst, in solvents which normally give low yields of 1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene with 3,3-dimethylbutene-1, improves product yields, comparable with the best published 3,3-dimethylbutene-1 methodology. Addition of co-catalyst permits the use of more environmentally acceptable solvent systems than those in existing syntheses of the desired tetralin. The yield improvement is rationalized on the basis of improved reaction homogeneity, facile cleavage of Al2Cl6 by Cl− ion, and increased effective solvent polarity, promoted by addition of the quaternary ammonium salt co-catalysts. Addition of quat co-catalysts to 3,3-dimethylbutene-1 based cyclialkylation systems did not increase rate, catalyst homogeneity or yield relative to a control (dichloromethane solvent). This suggests that the chlorinated hydrocarbon solvents normally used in this technology provide functions similar to that of quats in 2,3-dimethylbutene-1 based technology. These functions include the abilities to enhance AlCl3 solubility, increase the polarity of the reaction medium, and provide facile scission of Al2Cl6 to a more active catalytic species. In reactions where 2,3-dimethylbutene-1 is substituted for 3,3-dimethylbutene-1, addition of co-catalyst improves reaction rate, catalyst homogeneity, and yield reproducibility in non-polar solvents when compared to the best published, 2,3-dimethylbutene-1 methodology.

Synthesis of aromatic polyphosphonate: low temperature solution polycondensation of 4,4′-sulphonyldiphenol with phenoxy dichlorophosphate

This paper describes the synthesis of an aromatic polyphosphonate from the reaction of phenoxy dichlorophosphate (PDCP) with 4,4′-sulphonyldiphenol (SDP) in a chlorinated hydrocarbon solvent under low temperature conditions. The glass transition temperature ( T g) and melt temperature ( T m) of PDCP/SDP polymer are 69°C and 133°C, respectively. The lower T g value of PDCP/SDP compared to that of phenyl phosphonic dichloride/SDP may be attributed to the flexible ether linkage. This polymer started to lose weight at around 300°C under air or nitrogen atmosphere. The PDCP/SDP polymer has good flame retardancy, as indicated by high limiting oxygen index of 47.0.

Preparation of polyimides utilizing the Diels–Alder reaction, II: Bis[N-(butadienyl-2-methyl)] amino arylenes with bismaleimides

Four new bisdienes were prepared from 2-bromomethyl-1,3-butadiene and N,N-diethyl benzidine; bis[4-(N-ethyl) aminophenyl]-p-diisopropylbenzene, 1,4-diamino-2,3,5,6-tetramethylbenzene and α,α′ bis(4-amino-3,5-dimethyl phenyl)-p-diisopropyl benzene. Polyimides were synthesized by the Diels–Alder reaction of these bisdienes and bis(4-maleimidylphenyl)methane and bis(3-maleimidylphenyl) sulfone. The polymers were soluble in m-cresol, dimethyl sulfoxide and chlorinated hydrocarbon solvents. Moderate thermal stability was observed by thermogravimetric analysis in air and nitrogen.

A review of the attenuation of trichloroethylene in soils and aquifers

Abstract The transport, transformation, sorption and volatilization of trichloroethylene (TCE) as a non-aqueous phase liquid (NAPL) and as a dissolved aqueous constituent, under both laboratory and field conditions, are reviewed. NAPL-TCE is expected to migrate quite rapidly in soils and other water-unsaturated conditions, leaving droplets of organic liquid in the pore spaces. At the water table level, TCE may stop its downward movement and diffuse laterally, together with a slow migration downwards. From there on NAPL-TCE will slowly dissolve in groundwater. However, some specific hydraulic characteristics may induce rapid transport downwards away from the water table. TCE may appear in soils and aquifers as a result of its wide industrial use and also, possibly, as a degradation by-product of other chlorinated hydrocarbon solvents. TCE can undergo abiotic and (mostly) biotic, aerobic and (mostly) anaerobic transformations leading to less chlorinated ethenes. A half-life of 300 days was observed under field conditions. Batch and column experiments show that TCE is weakly sorbed on soil and aquifer solids with linear partition coefficients. Retardation factors in the range of l to 9 are reported from laboratory and field investigations. The adsorption is almost fully reversible. Gaseous TCE is more adsorbed than aqueous TCE, the extent of uptake being greatly influenced by the moisture content of the solid. Soil gas surveys appear as a promising technique for the study of soil and groundwater contamination by TCE. NAPL-TCE contamination should be quite effectively removed by steam injection. Because of its low adsorption and weak degradation under aerobic conditions, the diffuse contamination of aquifers by dissolved TCE can be extensive. In the case of localized and more severe pollution, approaches for the restoration of aquifers based on pumping followed by treatment at the surface may be effective but they usually are not economical. In situ treatment by stimulating the biotrans-formation is considered as a favourable alternative.

Polymerization of phenylacetylene by hafnocene dichloride/R xAlCl 3− x catalytic systems

The polymerization of phenylacetylene was investigated using the homogeneous catalysts Cp 2HfCl 2/R x AlCl 3− x . The reaction was performed in hydrocarbon and chlorinated hydrocarbon solvents at 0–60°. In all cases, the polymers were coloured, soluble, polyconjugated and paramagnetic; they were characterized by i.r., 1H-NMR, u.v.-visible and ESR spectroscopy.