A.E. McIntyre

Organic contaminants in the aquatic environment I. Sources and occurrence

Abstract Literature pertaining to the sources and occurrence of organic compounds in raw, potable and waste waters is reviewed. The introduction of organic micropollutants into the hydrological cycle is considered in terms of both point and non-point source discharges and the individual industrial and domestic sources of particular classes of organic chemicals are assessed. The occurrence in waters and waste waters of a wide variety of organic contaminants has been evaluated with regard to their concentrations in particular aqueous samples and frequency of occurrence. Although specific sources are known to be responsible for the addition of certain organic compounds to water and waste water, the occurrence of particular compounds cannot always be related to a particular source. In addition, it is evident that the reported occurrence of many organic contaminants has been limited by the capabilities of presently available analytical techniques. With the number of organic chemicals in use increasing, the potential for continued contamination of water resources exists. The implications for water quality and the possible effects generated by the introduction of organic compounds into the hydrological cycle on water re-use operations are discussed.

Evaluation of a tenax GC sampling procedure for collection and analysis of vehicle-related aromatic and halogenated hydrocarbons in ambient air

Abstract A technique for the measurement of vehicle-related emissions of aromatic and halogenated hydrocarbons in ambient air has been evaluated in order to permit routine monitoring of these compounds. Aromatic and halogenated hydrocarbons present in air are concentrated on Tenax GC and subsequently thermally desorbed into either an electron-capture or flame ionization detector equipped gas chromatograph using packed columns. The study reported here was undertaken to assess the effects of the concentration of determinands, rate of sampling, humidity and temperature on the safe sampling volumes. It is concluded that the technique is sensitive, versatile and accurate and can provide useful data on changing ambient air concentrations of aromatic and halogenated hydrocarbons.

The behaviour of polychlorinated biphenyls and organochlorine insecticides in primary mechanical wastewater treatment

Abstract An analytical method developed for the determination of polychlorinated biphenyls and organochlorine insecticides in sewage sludges has been successfully applied to the analysis of these compounds in sewages. These methods have been used to study the behaviour of these compounds during the primary sedimentation stage of sewage treatment. By analysis of24-h composite samples taken over a five day period, a mass balance of these micropollutants through the primary sedimentation process has been estimated. Concentrations of polychlorinated biphenyls and organochlorine insecticides in the raw and settled sewage were in the nanogramme/litre range, whilst primary sludge concentrations were in the microgramme/litre range. The results of the investigations indicate substantial removal of the compounds in the sludge produced during sedimentation, their removal being comparable to the removal of suspended solids. The implications of these findings for the present mechanisms of sewage sludge disposal and the possible wider dispersal of these persistent organic chemicals in the environment are discussed.

Organic contaminants in the aquatic environment II. Behaviour and fate in the hydrological cycle

Abstract The literature concerning the behaviour and fate of organic compounds in natural aquatic systems and in water and waste-water-treatment processes is reviewed. The factors governing the transport of organic compounds in water bodies are considered and the physical, chemical and biological processes which may bring about their transformation are also reviewed. The behaviour and removal of individual classes of organic micropollutants in conventional unit waste-water-treatment processes are assessed, together with an evaluation of the effectiveness of both tertiary and advanced waste-water-treatment procedures in the exclusion of organic contaminants from waste waters. Consideration is also given to the behaviour of organics in sewage-sludge treatment. The role of water-treatment processes in the removal of organic pollutants from raw and recycled waters and the production of potentially harmful organics during chlorination or other disinfection procedures is evaluated. The fate of organic micropollutants in the hydrological cycle and the effects of the disposal of sewage sludges contaminated with organic substances of concern are discussed.

Monitoring and assessment of ambient atmospheric concentrations of aromatic and halogenated hydrocarbons at urban, rural and motorway locations

Abstract Reductions in the lead content of petrol in the United Kingdom and in other European countries are predicted to change the concentrations of aromatic and halogenated hydrocarbons (1,2-dibromoethane and 1,2-dichloroethane) in ambient air. In order to assess possible changes in ambient air concentrations, the results of a monitoring survey of these compounds at urban, rural and motorway locations are presented. Ambient air samples were preconcentrated on Tenax GC and were analysed utilising a thermal desorption-gas chromatographic method. Highest concentrations for benzene (8·81 pptm) and toluene (13·48 pptm) were recorded at the urban site and good correlations between vehicle numbers and aromatic hydrocarbon concentrations were determined at both the urban and motorway sites. Background concentrations were determined at the rural site and the importance of dispersion, vehicle numbers and operating mode at the urban and motorway sites was demonstrated. The toleuene/benzene ratio (w/w) provided useful information on source identification at the urban and rural sites and provided supporting evidence of dealkylation of higher aromatics to benzene in engines operating at high speed and load at the motorway site.

Development of a Method for the Analysis of Chlorophenoxy Herbicides in Waste Waters and Waste Water Sludges

Abstract A multi-residue method has been developed for the analysis of chlorophenoxy acids in sewage and primary sewage sludge. Several different derivatisation techniques were evaluated using standard herbicide compounds. Replicate blank and fortified samples were extracted, derivatised, cleaned up and analysed for herbicide residues. Reproducilibity and the degree of recovery for the entire method were determined. Both packed and capillary columns were investigated for gas chromatographic analysis with detection by electron capture and mass spectrometry. It is recommended that 2-chloroethylation derivatisation in conjunction with capillary column gas chromatography-mass spectrometry detection and quantitation is employed for the analysis of these materials. The analytical scheme developed was found to be applicable for six of the chlorophenoxy herbicides (CPH) under investigation. The degree and reproducibility of CPH recovery are acceptable at a concentration of 2.5μgg−1 (with respect to dry solids) in...

Analysis of Polynuclear Aromatic Hydrocarbons in Sewage Sludges

Abstract An analytical method has been developed for the determination of polynuclear aromatic hydrocarbons (PAH) in sewage sludges, involving solvent extraction with cyclohexane, clean-up of the extract using silica gel thin-layer chromatography (TLC) and final separation of the purified PAH by two-dimensional TLC. Semiquantitative evaluation of sample chromatograms was achieved by comparison with standard chromatographic plates under ultra-violet light. Results are presented for a comparison of extraction procedures, determination of extraction efficiency by two different methods and for the analysis of sewage sludges taken from twelve UK sewage treatment works. The merits and limitations of the analytical scheme are discussed.

Ambient air measurements of aromatic and halogenated hydrocarbons at urban, rural and motorway locations

Abstract Concern over the carcinogenic properties of certain volatile organics in air, particularly benzene, has recently been expressed. Reductions in the lead content of perol in the United Kingdom and other European countries are predicted to change the concentrations of aromatic and halogenated hydrocarbons (1,2-dichloroethane and 1,2-dibromoethane) in ambient air. In order to provide baseline air quality data, prior to progressive reductions in the lead content of petrol, this study reports the results of a monitoring survey of ambient air concentrations of aromatic and halogenated hydrocarbon concentrations at urban, rural and motorway locations. A thermal desorption/gas chromatographic method analysing Tenax GC sampling tubes was utilised. Highest concentrations for benzene (9.7 ppb) and toluene (15.5 ppb) were measured at the urban site. The average benzene concentration is comparable with a proposed ambient air quality standard in the Federal Republic of Germany. Multiple regression analysis of nonmethane hydrocarbon and carbon monoxide air quality data demonstrated the importance of meteorological variables in defining measured concentrations. The toluene/benzene ratio (w/w) provided useful information in determining the degree of vehicle-related air pollution and supported evidence obtained from dynamometer studies of dealkylation of higher aromatics to benzene in engines operating at high speed and load at the motorway site.

A survey of air pollution in the vicinity of Heathrow airpot (London)

Abstract An investigation of atmospheric quality in the vicinity of Heathrow airport (London) has been undertaken. Ambient concentrations of total hydrocarbons, methane, carbon monoxide, non-methane hydrocarbons and airbone particulate lead were monitored. Eight sites were visited in each of the years the survey was undertaken, approximately half of the sites were close to the airport perimenter and the remainder in the surrounding urban residential areas. This was achieved by the use of a mobile laboratory containing the necessary continuous monitors. Although the objective of the study was to assess the impact of the airport upon air quality, no distinction could be made between the relative contributions to air pollution of the airport sources and those arising from motor vehicle and industrial activity in the area.

Behaviour of persistent organochlorine micropollutants during primary sedimentation of waste water

The removal of polychlorinated biphenyls and the organochlorine insecticides gamma-HCH, aldrin, dieldrin and endrin during primary sedimentation of raw sewage has been studied using a pilot plant facility. A matrix of sixteen experiments was performed, where the pilot plant was operated at four different hydraulic loadings with four different influent suspended solids loadings. Significant removals of micropollutants into the primary sludge were observed, although no particular relationship with the removal of suspended solids was evident. It is concluded that a proportion of the organic microcontaminants present in raw sewage were associated with non-settleable solids and were also in the dissolved form. The significance of the behaviour of organochlorine micropollutants in waste water treatment processes and the hydrological cycle are discussed in the context of water re-use operations.