Environmental chemistry of PCB-replacement compounds - VI - composition and metabolism of Wemcol ®, an isopropylbiphenyl formulation

Wemcol is a technical isopropylbiphenyl formulation that is used as a substitute for polychlorobiphenyl. According to the producer Wemcol is 4-isopropylbiphenyl, but we found our sample to consist of 60.3% 3-isopropylbiphenyl, 38.6% 4-isopropylbiphenyl and 3,5-, 3,3′-, 3,4′- and 4,4′-diisopropylbiphenyl in amounts of 0.3%, 0.4%, 0.2% and 0.1% respectively. The two major components of the mixture are metabolized in the rat by two routes : oxidation of the isopropyl group and hydroxylation of the aromatic nuclei. Rats fed the technical mixture retained 3- and 4-isopropylbiphenyl in a ratio 4.3 : 1 in their abdominal fat, whilst the ratio in the mixture is 1.6 : 1. One week after the simultaneous feeding of equal amounts of Wemcol, 4,4′-dichlorobiphenyl, 2,4′,5-trichlorobiphenyl and 2,2′,5,5′-tetrachlorobiphenyl, the isopropylbiphenyls, in contrast to the chlorobiphenyls, could no longer be detected in the abdominal fat of rats.     

SEWAGE DISCHARGES FROM SHIPS TRANSITING COASTAL SALT WATERS1

ABSTRACT: A number of aspects of the discharging of non-oily wastewaters by transiting ships are treated in this overview paper. In the introduction, options to discharging (the use of holding tank, on board treatment) and the impact of changing regulations are discussed. Assessment of the effects of sewage discharges on coastal waters required that data, at first not available, be generated. An account is given of the characterization of Navy shipboard wastewaters and of experiments involving sewage discharges at sea, measurements of water quality before, during and after an amphibious operation, and fore and aft of transitting Navy ships. A better understanding of sewage dilution after discharge led to the verification of a method for controlled discharging of sewage (and other wastewaters). This method permits limiting the coliform bacteria count in the ship's wake to values below acceptable limits. The final sections contain information on long range effects of ships’sewage discharges, obtained in studies by the U.S. Navy and others, as well as public health considerations.     

An Automated Wet Deposition System to Compare the Effects of Reduced and Oxidised N on Ombrotrophic Bog Species: Practical Considerations

Critical N loads for ombrotrophic bogs, which often contain rare and N-sensitive plants (especially those in lower plant groups: lichens, mosses and liverworts), are based on very few experimental data from measured, low background N deposition areas. Additionally the relative effects of reduced versus oxidised N are largely unknown. This paper describes an automated field exposure system (30 km S. of Edinburgh, Scotland) for treating ombrotrophic bog vegetation with fine droplets of oxidised N (NaNO₃) and reduced N (NH₄Cl). Whim Moss exists in an area of low ambient N deposition (ca. 8 kg N ha^–1 y^–1), the sources and quantification of which are described. The wet N treatment system is run continuously, and is controlled/activated by wind speed and rainfall to provide a unique simulation of real world treatment patterns (no rain=no treatment). Simulated precipitation is supplied at ionic concentrations below4mMin rainwater collected on site. Treatments provide a replicated dose response to 16, 32 and 64 kg N ha^–1 y^–1 adjusted for ambient deposition (8 kg N ha^–1 y^–1). The 16 and 64 kg N ha^–1 y^–1 are duplicated with a P+K supplement. Baseline soil chemistry and foliar nutrient status was established for all 44 plots for Calluna vulgaris, Sphagnum capillifolium, Hypnum jutlandicum and Cladonia portentosa.     

Residues of dioxins and PCBs in fat of growing pigs and broilers fed contaminated feed

To investigate the kinetics of PCBs and dioxins, 3 week old broilers and 3 month old pigs were fed with a 10-fold diluted feed from the Belgium crisis for one week, followed by a period on clean feed. In the case of broilers this resulted in levels for dioxins, non-ortho and mono-ortho PCBs in fat of 102, 84 and 216 ng TEQ/kg, summarized to 402 ng TEQ/kg. Total levels decreased to 217 and 109 ng TEQ/kg after 1 and 3 weeks on clean feed. Indicator PCB levels decreased from an initial 6.2 mg/kg fat to respectively 3.2 and 1.5 mg/kg. The ratio of indicator PCBs to dioxins TEQs was stable over this period. Levels in back fat of pigs at the end of the exposure period were 26, 15, 82 and 123 ng TEQ/kg for respectively dioxins, non-ortho PCBs, mono-ortho PCBs and the sum. Total TEQ levels decreased to respectively 95, 70, 40, 22 and 12 ng TEQ/kg after 1, 2, 4, 8 or 12 weeks on clean feed. After 12 weeks dioxin levels were around 1 ng TEQ/kg. Indicator PCB levels decreased from 3.48 mg/kg to 2.65, 2.01, 1.25, 0.76 and 0.45 mg/kg fat, again after 1, 2, 4, 8 or 12 weeks on clean feed. Levels of dioxins decreased more rapidly than those of indicator PCBs, also reflected by the ratio of indicator PCBs to dioxins, being 133,000 at the end of the exposure period and 357,000 after week 12. It is concluded that the use of indicator PCBs for dioxins, in the case of a combined exposure, is a safe alternative for screening and in the case of pigs results in an overestimation rather than underestimation of the dioxin levels.     

Review and assessment of models for predicting the migration of radionuclides from catchments

The present paper summarises the results of the review and assessment of models developed for predicting the migration of radionuclides from catchments to water bodies. The models were classified and evaluated according to their main methodological approaches. A retrospective analysis of the principles underpinning the model development in relation to experimental finding and results was carried out. It was demonstrated that most of the various conceptual approaches of different modellers can be integrated in a general, harmonised perspective supported by a variety of experimental evidences. Shortcomings and advantages of the models were discussed.