No description available.

No description available.

No description available.

The importance of iron and manganese oxides in soil-water environments and their roles in controlling the availability and mobility of contaminants and nutrients are determined. Sorption is simulated using the synthetic iron and manganese oxides: goethite (a-FeOOH), birnessite (Na4Mn14O27.9H20a) nd magnetite (Fe304) which are analogous to natural soil components. Goethite is investigated in the three possible modes of occurrences in soil: colloidal, aggregate, and as coatings on inert materials. The adsorption of cadmium and cobalt onto goethite occurs in a narrow pH range between 6.5 and 7.5. Metal retention increased with both temperature and contact time. A tenfold decrease in ionic strength has no effect on the adsorption pH. Goethite pellets have a different pattern of adsorption due to reduction in surface area and granulation. The sorbing capacity of goethite coated sand is lower than that of the colloidal goethite but has a similar adsorption curve. The coated material is shown to have potential in industrial applications and notably in effluent treatment. Cobalt and cadmium uptake on to hydrated suspensions of birnessite occur in a pH range (3.0-8.0) with sigmoidal shapes for the percent of adsorption curves. Birnessite uptake capacity increases with increasing pH with a maximum at about 6.4 pH. The pH, contact time and the surface area of the oxide are the main factors that control the uptake. The adsorption of coloured species and organic colloids on magnetite was investigated in which magnetite is used both as an adsorbent and as magnetic material. Colour species and organic colloids adsorbed in acid pH and the adsorption decreases with increasing alkalinity. Dissolutions of the magnetite itself increases in low and high pH conditions. The results of investigations of sorption of contaminants and nutrients onto iron and manganese oxides have been applied to shed light upon the behaviour of contaminants and nutrients in soil in the light of soil resource management. The importance of a detailed understanding of contaminant and nutrient transport behaviour in soil-water systems to achieve effective environmental management is demonstrated. Although soil pollution is of major environmental concern, it is probably the least understood source of pollution in terms of both transport of contaminants and remediation. The studies carried out in this work have indicate the types of information required to permit the development of soil management and remediation protocols that will assist in technical management of issues related to soil resources. Detailed knowledge from experimental work must form the scientific basis for the development of contaminated soil assessment and management in an integrated approach.

A feasibility study was planned to determine the efficiency of immobilized algal cells growing in a packed bed for removing Cd from commercial effluents. To select appropriate material for an immobilized cell system, twenty-five strains of algae isolated from heavy-metal contaminated environments of known water chemistry were tested for their ability to accumulate Cd. Before accumulation experiments were initiated, ion exchange resin was employed to demonstrate that EDTA in the medium did not complex Cd to a significant degree. Svnechococcus D562 cells subcultured in Cd accumulated the most metal; little was bound to the cell wall. A continuous culture of steady- state Svnechococcus D562 cells tolerated a lower maximum concentration of metal (3.4 mg 1(^-1) Cd) than batch- cultured cells (5 mg 1(^-1) Cd), indicating that metabolic status influences the toxicity of Cd. When flasks of calcium-alginate beads were challenged with Cd, up to 60 % of the added metal was bound within 16 h; however, further incubation did not reduce the pollutant concentration. Two axenic strains which accumulated the metal to a high concentration were then immobilized and tested for their capacity to remove Cd from the circulating medium. A packed-bed reactor containing Mougeotia D536 cells proved more effective at metal removal than Svnechococcus D562, but both species grew to a lower cell density at the effluent end of the column. The medium was then aerated to overcome such growth-limiting conditions, but this treatment inhibited Cd accumulation. Column-immobilized cells reduced Cd levels more effectively than inoculated, alginate beads in stationary flasks or free cells. Energy dispersive X-ray microanalysis located Cd only in particular Svnechococcus D562 polyphosphate bodies (those with a high Ca to K ratio); peaks for Zn, Pb, Fe, Mn and Ba were also detected in algae isolated from the field. Scanning proton microanalysis provided information on the distribution of macro- and micro-elements throughout the two strains of cyanobacteria and two strains of algae selected from the Durham Culture Collection and demonstrated the presence of Cd in Klebsormidium rivulare D537.Detergent-sensitive spheroplasts of Svnechococcus D562 were produced by lysozyme and protease digestion, but were not viable for growth. To observe the extracellular mucilage of this strain by EM, lysozyme digestion proved imperative for effective ruthenium red staining to convert the material into an electron opaque material. From cultures of Svnechococcus D562 grown with or without Cd a 14 kD plasmid was isolated, which contained two Eco RI, two Bam HI and five Hind III restriction sites. A radiolabelled oligonucleotide probe based on part of the nucleotide sequence of a metallothionein from Svnechococcus FCC 6301 did not bind to a genomic and plasmid blot of Svnechococcus D562 DNA. The putative Cd-binding peptides ((yEC)(_n)G's) that were discovered only bound significant quantities of the metal when cells were exposed to 6.17 mg 1(^-1) Cd for 2 days at the end of their log-growth phase. Indigenous peptides failed to bind substantial amounts of the metal and the presence of Cd throughout growth did not influence the quantity of chelated Cd, except for Mougeotia D536. The pH of half displacement for (yEQjp's from this strain is comparable with that of other species. Reversed-phase HPLC of the peptides from Mougeotia D536 generated a thiol profile similar to that recorded for the Cd-binding peptides of Datura innoxia. The Cd-induced ultrastructural distortions that were recorded include potential Ca / P / Cd precipitates in Mougeotia D536, the loss of polyglucoside granules from Calothrix D184 together with a relaxation of its thylakoid packing and a lack of plastoglobuli in Cd-exposed Klebsormidium D537. The space between an immobilized cell and the matrix either represents shrinkage of the matrix during dehydration or mucilage which does not bind electron dense stains. Release of alkaline phosphatase into the medium by Svnechococcus D562, provided suitable material to study the inhibitory effects of Cd upon P hydrolysis. Ultrafiltration membranes proved effective as initial step towards enzyme purification and for the determination of activity under sub-optimal pH conditions. At pH 7.0, the activity of an enzyme concentrate was inhibited when 1 and 10 mg 1(^-1) Cd were added to the assay medium, but the presence of this metal in the growth medium did not reduce activity. One-dimensional SDS PAGE revealed only one protein difference between strains grown with or without Cd; a reduction in the staining intensity of a 17 kD band of Calothrix D184.

No description available.

The distribution of trace metals (Fe, Mn, Cu, Cd and Pb) has been determined in dissolved and particulate phases, along with relevant hydrographic parameters, from the nearshore coastal zone of the western North Sea (between 52ON and 56ON) during four Land Ocean Interaction Study (LOIS) surveys covering the seasonal cycle (autumn 1994 to summer 1995) The behaviour of the redox-sensitive metals, Fep and Mnp in the western North Sea were strongly correlated (r>0 44 for all seasons, P<0 05) in all surveys and exhibited maximum concentrations in winter (16 mg g -1 and 700 ug g-1 respectively) which progressively decreased throughout the year Distinct seasonal variations were also observed for particulate Cu, Cd and Pb For example, enhanced concentrations of Cup (36 ± 39 ug g-1) and Cdp (0.36 ± 0.42 ug g -1) in the Humber coastal zone during summer were attributed to preferential particulate organic/biogenic-metal interactions. In contrast enhanced, though diffuse, atmospheric inputs of Pb from continental winds were considered to have contributed to the elevated Pbp concentrations (82 ± 27 ug g -1) observed offshore during winter Results from radiotracer incubation experiments suggest that biological activity makes a significant contribution to the removal of dissolved Mn and Cd to the particulate phase. However, a phase lag of two to three months between maximum primary productivity and maximum particulate metal adsorption (KD=2 X 104 & 5 x 102 for Mn and Cd respectively) indicates a decoupling from the spring plankton bloom In general metal distributions in the Humber coastal zone were significantly influenced by freshwater discharge, tidal regime at the mouth of the estuary and prevailing wind conditions Total trace metal fluxes across the mouth of the Humber Estuary were highest during spring (311, 8 96 & 1045 kg day-1, for Cu, Cd and Pb respectively) and lowest during summer (25 7, 1 .12 & 33 4 kg day-1, for Cu, Cd and Pb respectively) They were dominated by variations in freshwater outflow and the tidal range during sampling On an annual basis comparison to estuarine inputs (rivers, industry and sewage sources) suggested retention of Cu (25%) and Cd (56%) Estimates of partitioning (KD) were derived from the dissolved and particulate data for Cu, Cd and Pb over the seasonal cycle Copper was dominated by the particulate phase (73-80%) in all seasons but summer, whilst Cd showed particulate phase dominance (54-70%) in autumn and winter only The Pb distributions were dominated by the particulate phase (94-99%) independent of season Trace metal settling velocities implied that the Humber Plume was acting as a sink for Cu, Cd and Pb in winter and spring However settling velocities calculated for Cd and Pb (flood tide) in summer were similar to background suspended particulate matter (SPM) suggesting long range transport with the residual circulation. Modelling of Pb isotopic ratios in the Humber Plume suggested that on average 32-39% of the extracted Pbp originated from anthropogenic sources The data from this study has given unique information concerning the concurrent seasonal distributions of particulate trace metals in the western North Sea and have yielded new insights into mechanisms affecting trace metal cycling and transport, essential in the development and refinement of coupled hydrodynamic-geochemical models.

Studies of living benthonic foraminiferal assemblages carried out by marine biologists are comparatively rare. This study of the changes in foraminiferal assemblages from three subtidal sites near Plymouth, U.K., has been carried out with the intention of determining the importance of various abiotic and biotic variables to the foraminiferal communities studied using statistical correlation. Temperature and salinity at depth and particle size characteristics together with organic content, bacterial abundance and type, and other meiofauna present were assessed monthly with samples taken for foraminiferal content, and for seasonal diatom analysis. Deformed specimens were very rare in the examined samples of natural assemblages. Three different systems were used in an attempt to culture Elphidium crispiim (Linne) for ecotoxicological studies, which failed. Ecotoxicological studies were carried out upon Roialieila elaticam Pawlowski &amp; Lee and adult Ammonia batavits (Hofker). The types of deformation produced by laboratory-maintained Foraminiferida were found not to be specific to the stressor used and, therefore, the use of this group of Protozoa as indicators of specific pollution is not possible. The methods which Elphidium crispiim utilises to remain epifaunal were investigated and found to be primarily controlled by phototaxis, together with geotaxis.

Acquiring high quality in situ analytical data with good temporal resolution is required for developing models of phosphorus transport and biogeochemical behaviour. Chapter One describes the behaviour of phosphorus in the aquatic environment, its sources, its role in the eutrophication process and legislation to control its release into aquatic systems. It also summarises analytical techniques for the determination of phosphorus in natural waters. An examination of the hypothesis that the export coefficient modelling approach can be used to predict phosphorus loading in the River Frome catchment, Dorset on an armual and seasonal (monthly) basis is presented in Chapter Two. The model predicted an annual (1998) phosphorus load of 25,605 kg yr'\ compared with an observed (measured) value of 23,400 kg yr'V Monthly loads agreed well with monthly observed values except during months of variable discharge. Chapter Three describes a study on the comparison of sample storage protocols for the determination of total oxidised nitrogen (TON) and filterable reactive phosphorus (FRP) in the River Frome and Tamar Estuary. The results showed that optimum storage conditions were highly matrix dependent, with significant differences in measured FRP concentration over time between the River Frome and Tamar Estuary (due to different calcium concentrations) and between samples of different salinities (due to different bacterial populations). Chapter Four describes the development and deployment of a portable flow injection (FI) monitor for phosphorus determination in the River Frome. The automated monitor, incorporating solenoid micropumps and switching valves, a miniature CCD spectrometer, a graphical programming environment and a tangential flow filtration unit, achieved a detection limit of 0.67 pM and was able to monitor at high temporal resolution (every 30 min). Chapter Five examines historical water quality indicators and data fi-om recent shortterm, high temporal monitoring campaigns using the FI monitor in order to identify the key factors affecting phosphorus concentrations in the River Frome. Results showed the importance of catchment geology (chalk-based) and hydrological conditions in relation to other physico-chemical parameters in controlling phosphorus behaviour.

Members of the meiobenthos have been used extensively to determine the effects of anthropogenic perturbation in marine systems (Coull &amp; Chandler, 1992). Despite this, the meiofauna has been virtually excluded from freshwater pollution monitoring. This thesis aimed to address this research caveat, by evaluating the potential of stream meiofauna for monitoring metal-contamination. Meiofaunal communities were sampled from streams in SW England representing a gradient in metal contamination. Environmental variables in these streams were also measured to identify the important forcing agents structuring the stream benthos. Multivariate techniques demonstrated Cu, either alone or in combination with other environmental variables was of most importance in correlations with the composition of meiofaunal communities. Comparison with the macrofaunal data demonstrated that both components of the benthos responded in a similar way to metal contamination, although the meiofauna also highlighted other differences in water chemistry. The combination of meiofauna, macrofauna and temporary meiofauna in a combined metazoan community analysis gave the best discrimination of sites. Detection of metal-contamination was retained in meiofaunal data aggregated to the family level. The abundances of the harpacticoid copepod Bryocamptus zschokkei were consistently important in contributing to between-site differences in community structure. The harpacticoid, therefore was selected as an ecologically-relevant freshwater toxicity test for Cu. Laboratory experiments demonstrated that Cu had toxic effects on the survival and reproduction of Bryocamptus zschokkei. Although acute toxicity tests gave more rapid results, these effects on survival occurred at a higher Cu concentration than those in the chronic tests. Sub-lethal concentrations of Cu led to a reduction in the numbers of offspring per brood Animals with pre-exposure to chronic concentrations of Cu exhibited greater tolerance to this metal. In conclusion, more information may be gained by including the meiofauna, alongside the macrofauna, when monitoring the impact of contaminants on freshwater systems. To reduce the effort of processing samples it appears family level data could be used to detect metal-contamination. The novel use of B. zschokkei in laboratory tests, where it showed lethal and sub-lethal responses to Cu, demonstrated that this species may have much potential as an ecologically-relevant freshwater bioassay organism for this metal. The advantages of using meiofaunal species such as B. zschokkei as toxicity test organisms are discussed.