ANALYSIS OF FIRM WATER SUPPLY UNDER COMPLEX INSTITUTIONAL CONSTRAINTS1

River basin computer simulation studies often do not properly include the complex legal and institutional factors governing water allocation. These factors include formal water rights and informal borrowing agreements among the basin water users. An attempt has been made in this study to show that such factors can be included. We also show that an optimal, integrated approach to reservoir operations in a river basin can do much to alleviate the burden of new demands placed on available water resources. The procurement of a firm water supply for a proposed coal fired power plant is analyzed as a case study. An efficient river basin simulation model is used to determine the viability of a scheme for providing an annual firm water supply to the plant, with consideration of the existing water storage and demands within the basin. Given the hydrologic sequence considered, the model results show that the proposed strategy is viable in that the required firm water supply can be realized without causing harm to decreed water users in the basin. However, integrated diversion and reservoir operations are required to assure a desirable uniform rate of delivery of reusable effluent to the power plant.     

Zoobenthic variability associated with a flood and drought in the Hawkesbury estuary,New South Wales: Some consequences for environmental monitoring

Changes in the Hawkesbury zoobenthos associated with a major flood and drought are described and comparisons made in the patterns of change among estuarine reaches and among sites within reaches. The consequences for environmental monitoring and management are discussed. Replicate grab samples were taken from four sites in each of the lower, middle and upper reaches. Reductions in the mean number of species per grab (S) following the flood were significant only in the lower reaches and at one site in the middle reaches. Increases in S accompanied the drought in all reaches but intra-reach variation in temporal patterns occurred in both S and in the most abundant species found. Thus, major weather events are associated with temporal changes whose patterns differ on both small and large spatial scales. Consequently, the results from fixed-factor sampling designs, which are widely used, may be unrepresentative of other areas. Unfortunately, the alternative approach of stratified random sampling will probably be both prohibitively expensive and difficult to implement in the complex estuarine benthic habitat. Further, short-term studies will probably be grossly unrepresentative of natural temporal variation. Attempts to reduce expenses by using only one or two abundant species as characterising communities or as indicators of physicochemical conditions may be unreliable because of variation in both time and space in dominant species and the lack of pollution-response knowledge for local species.     

The effect of heavy metals on dinitrogen fixation by Rhizobium-white clover in a range of long-term sewage sludge amended and metal-contaminated soils

An investigation was conducted to determine whether effective strains of Rhizobium leguminosarum biovar. trifolii capable of symbiotic N2 fixation with white clover (Trifolium repens) were present in a range of metal-contaminated soils. A number of historically sewage-amended sites (including experimental, pasture grassland and arable sites) were selected and compared with highly contaminated samples from abandoned heavy metal mines. Many sites had metal concentrations above the limits established by the UK Government, based on those developed by the European Commission (EC) for sludge-amended soils. Acetylene reduction activity (ARA) was used to screen the samples for effective N2 fixation. When the host plant was indigenous to the sward, rhizobia were found in the nodules and in the soil rhizosphere at all the sites tested. They were shown to be capable of effective symbiosis and N2 fixation, even though metal concentrations greatly exceeded the soil metal limits in some cases. However, nodulation failed to occur in some cases where T. repens was not indigenous to metal-contaminated soils. This indicated either that an ineffective rhizobial population was present, or that effective cells were absent from the soil. The influence of individual metals on ARA could not be determined conclusively because of the confounding effects of soil physicochemical variability and the presence of different metals at high concentrations together in the soil. However, Cd concentrations appeared to be particularly important in determining the presence of effective ARA in soils with no indigenous clover. In contrast to previous studies, the results presented here suggest that heavy metals may have had a quantitative effect on the free-living population of rhizobia, rather than a genetic effect.     

A field study of the generation of nitrate in a hill cap cloud

A field experiment to investigate the formation of nitrate as an airstream passes through a hill cap cloud has been performed at the UMIST field station on Great Dun Fell. It has been shown that the aerosol nitrate concentration increased by about 0.5 microg m(-3) as the airstream passed through the cloud during the night. At sunrise the nitrate production disappeared. It is suggested that the most likely mechanism for this nitrate production was due to the solution of N2O5 and NO3 formed from the reaction of NO2 with O3. These higher oxides build up overnight in the absence of short wave radiation to photolyse them. Other possible mechanisms of nitrate production are also discussed.     

Arrested municipal solid waste incinerator fly ash as a source of heavy metals to the UK environment

Arrested fly ash samples from most currently operating municipal solid waste (MSW) incinerators in the UK have been analysed for a range of elements. Some of the more important heavy metals ranged in concentration as follows: Cd, 21-4646 (median = 271) mg kg(-1); Cu, 296-1307 (642) mg kg(-1); Cr, 44-1328 (574) mg kg(-1); Ni, 45-2204 (74) mg kg(-1); Pb, 447-9704 (4337) mg kg(-1); and Zn, 2285-13,500 (9232) mg kg(-1). These concentrations represent considerable enrichments relative to median UK soil concentrations. Enrichment ratios (defined as median fly ash: median UK soil) were as follows: Mn 1.6; Co 2.6; Ni 3.3; Ba 11; Sr 11; Cr 15; Cu 35; Pb 108; Zn 113; Cd 387. It is estimated that MSW incinerator ash contributes c. 15 t Cd and 241 t Pb to UK landfill sites per annum. These figures compare with previous studies by Hutton & Symon (Hutton, M. & Symon, C. (1986). The quantities of cadmium, lead, mercury and arsenic entering the UK environment from human activities. Sci. Total Environ., 57, 129-50.) which estimated that annual inputs to UK landfills from coal fly ash are c. 60 t Cd and 1270 t Pb. However, it is argued that metals associated with MSW ashes are potentially of greater environmental significance than in coal ashes, because they are much more available and present at much higher concentrations.     

Die Aleuronzellen des keimenden Getreides

Während der Vorbereitungen zu diesem Artikel war R. L. J. als Preisträger der Alexander-von-Humboldt-Stiftung in Göttingen tätig. Unsere Forschung auf diesem Gebiet wurde durch großzügige Hilfe der Deutschen Forschungsgemeinschaft und der National Science Foundation (USA) ermöglicht. Außerdem sind wir B. Raufeisen für die Herstellung der Zeichnungen sehr zu Dank verpflichtet.     

Towards an alternative criterion for the shipping safety of activated carbons

A new criterion for shipping safety of activated carbons is developed which requires microcalorimetric measurements for its implementation. It is examined by making microcalorimetric measurements on a variety of commercial activated carbons. Results are compared with those for the same carbons according to the critical ignition temperature approach.     

The persistence of polynuclear aromatic hydrocarbons (PAHs) in sewage sludge amended agricultural soils

In 1968, five metal enriched sewage sludges containing different concentrations of polynuclear aromatic hydrocarbons (PAHs) were applied to different plots on field soils at two experimental sites, Luddington and Lee Valley, in the UK. This resulted in substantial increases in the total PAH soil concentrations in all plots. Since application, losses have occurred, with the high molecular weight PAHs being more persistent. Calculated half-lives range from under 2 years for naphthalene to over 9 years for benzo[ghi]perylene and coronene. The losses of PAH compounds in these field experiments can be related, in part, to their physico-chemical properties, notably the octanol: water partition coefficient.     

Life-cycle assessment of 11 kV electrical overhead lines and underground cables

The life-cycle impacts of five different 11 kV electrical power cables (three overhead lines and two underground cables) were analysed. These were compared by their embodied impacts in production and total lifetime operational impacts. The life-cycle results revealed there to be three key issues, the impacts of climate change, fossil fuel depletion, and particulate matter formation (PMF). The former two were of particular significance. The embodied impacts, which are those associated with the materials, were generally determined to be insignificant. The exception was for underground cables at low operating loads. Under these conditions PMF was more significant as a result of the high embodied impacts of the cables. Further analysis revealed that these impacts could be mitigated with an end of life material recovery program. At present the underground cables are not recovered, but if they were the recycling benefits would give rise to a notable improvement in PMF. For the other impact categories operational conductor losses were the dominant cause of impacts. In summary it was concluded that to minimise the life-cycle impacts of 11 kV cables the system with the lowest conductor resistance should be selected.