No description available.

No description available.

No description available.

In this study, a new analytical method for the simultaneous determination of total N, P and S using hydrogen peroxide oxidation has been developed for the analysis of water and sediment samples. The products of the oxidation reaction (nitrate, phosphate and sulphate) were determined by ion chromatography. A method for the simultaneous chemical speciation of arsenic, selenium and chromium was developed using ion chromatography coupled with ICP-MS. Reversed phase chromatography and ICP-MS was used for the simultaneous determination of mercury and selenium species. For the speciation of vanadium a new method using HPLC with reversed phase and ICP-MS detection was developed. The species arsenite, arsenate, selenite, selenate, chromate, methylmercury, inorganic mercury, selenocystine, selenomethionine, vanadium (IV) and vanadium (V) in samples of water, sediment, fish muscle tissue and mussel, were determined using the developed methods. Simultaneous determination of nutrients and metal species were applied to the study of pollution in Lake Maracaibo, Venezuela. The distribution of As, Se, Pb, Hg, Sn and V in sediment was studied using a sequential extraction scheme and related to the physicochemical parameters and nutrient content. The major concentrations of arsenic and lead found inside the lake were associated with the fraction associated with the Fe/Mn hydroxides phase, however, mercury and selenium were distributed at the main zone of the lake in the organic-sulphide fraction. In the strait and the gulf, metals were distributed mainly in the residual phase with the exception of tin. Conditions which favour mercury methylation in the lake are discussed. In the centre of the lake, with anaerobic conditions, methylmercury was the predominant species for mercury. The results found for vanadium and arsenic speciation showed that the predominant species in all the samples of Lake Maracaibo was vanadium (IV) and arsenite, respectively. Results were compared with those from lakes with similar pollution problems.

No description available.

No description available.

Copper tolerance has been investigated in Nereis diversicolor and Corophium volutator from three different estuaries; the Humber, Alaw and Dulas, and intraspecific variation in the responses to copper of both these animals were examined. Sediment concentrations of copper from Dulas were the highest (224µg g⁻¹) compared to the Humber (70µg g⁻¹) and Alaw (6.2µg g⁻¹) estuaries. A high ability to tolerate copper based on 96 hour LC₅₀ values for dissolved copper (1.75 mg l⁻¹ in Corophium and 0.59mg l⁻¹ in Nereis) and high body copper concentrations (450µg g⁻¹ in Corophium and 698µg g⁻¹ in Nereis) were found in animals from the Dulas estuary. Moderate tolerance (1.34mg l⁻¹ in Corophium and 0.34mg l⁻¹ in Nereis) and moderate body copper concentrations (140µg g⁻¹ in Corophium and 100µg g-1 in Nereis) were found in species from the Humber, compared to animals from the Alaw which showed very low copper tolerance (0.8mg l⁻¹ in Corophium and 0.26mg l⁻¹ in Nereis) with very low body copper concentrations (52µg g⁻¹ in Corophium and 65µg g⁻¹ in Nereis). These copper concentrations and degree of tolerance in Corophium and Nereis from the three estuaries reflected the levels in the sediments. Tolerance could not be acquired after exposure of juvenile and adult Nereis to a range of sublethal copper concentrations over a 30 day period. Tolerance in adult worms from Dulas was not lost after exposure to 'clean' conditions for 30 days supporting the suggestion that it may be genetic. In the Humber estuary there was generally little spatial or temporal variability shown in a suite of metal concentrations in the sediments, Corophium and Nereis recorded at 3-monthly intervals over a 12 month period. Interspecific and intraspecific differences were found in the uptake and accumulation of copper. Copper tolerant Corophium accumulated significantly lower amounts of copper (relative to their control concentrations) compared to the less tolerant populations after exposure to external dissolved copper concentrations. The opposite was true for the tolerant population of Nereis accumulating the highest amount of copper relative to their control levels. The high levels of total body copper found in the tolerant populations of both Corophium and Nereis suggests that the metal is being sequestered in a non-toxic way, but an exclusion mechanism and/or an excretion mechanism may also be in operation. Localisation of this metal was investigated in the tolerant population of Nereis and the accumulated copper was found to be tissue specific. The ability to tolerate copper was probably due to increased deposition of copper in membrane-bound structures located in the cells of the nephridial tubules. Copper was not found in the nephridial area of the non tolerant worms from the Alaw estuary. Intraspecific variation was found to occur in the survival and body copper concentrations of Corophium and Nereis after exposure to different natural sediments in experimental situations. The physicochemical nature of each of the sediments affected the bioavailibity of copper which caused different responses in Corophium and Nereis. Patterns and similarities between the biological responses and physico-chemical parameters were examined and simple predictive models were constructed to explain the variation found in the responses of Corophium and Nereis. The LC₅₀ value was used as an index of tolerance and was found to be important in explaining variation in the survival and copper accumulation in Corophium and Nereis. These results were used to discuss the importance of intraspecific variation in Corophium and Nereis in the monitoring and management of metals in estuaries. This would produce sensitive and responsive management tools for individual estuaries rather than a blanket approach. This may be appropriate in some situations, particularly where certain metals are problematical as with the case of copper in the Humber estuary.

Leather production results in large volumes of waste water containing high levels of sodium sulphide, which has to be treated before disposal. The use of ozone to facilitate this oxidation was considered by first studying ozone-sodium sulphide reaction. The sodium sulphide solutions were found to be adequate models for the tannery effluent. The reaction order was found to be second order overall (first order in both sulphide and ozone). The true reaction order was found to be 0.33 for sulphide in the initial stages of the reaction. The use of ozone in conjunction with either UV radiation or a manganese catalyst was found to have no benefit to the rate of sulphide oxidation. The reaction products were thiosulphate, sulphite and sulphate. A mathematical model based on a first order consecutive reaction scheme was developed. The liquid phase mass transfer coefficient for physical absotption of ozone into water was estimated to be k'La=4.76 x 10-3 S-I, while the overall transfer coefficient during the ozone-sulphide reaction was estimated to be Kt.a=().0719 S-I. This gave an enhancement factor of 15.1 which indicates that ozone decomposition reactions may be negligable. It was estimated that a full scale ozone system would require the application of 120 kg of ozone per hour for 12 hours to treat 200 Itt waste water. An economic comparison of this proposed system indicates that operating costs for ozone would be approximately 6 times greater per m3 waste water than the costs for the current aeration treatment

Following the surface application of different fertiliser treatments (cattle slurry, cattle manure, and inorganic fertiliser) to grassed hillslopes, the transport of nitrogen (N) and phosphorus (P) was monitored on controlled plots. The plots measured 30 m by 5 m, the lower 10 m acting as an untreated buffer zone, in order to examine the effect of following current codes of practice when applying fertilisers (MAFF and WOAD, 1991). Surface and sub-surface nutrient flow pathways were monitored, by sampling water from the saturated and unsaturated zones of the soil profile, and from surface runoff. Sub-surface flow was dominated by N03--N. However, concentrations of this N species were relatively low (3-6 mg 1-1), and differences between treatments and the control were not significant. Generally, this indicated immobilisation of N species and P fractions, outputs in plant uptake and possibly to atmosphere (denitrification). For surface runoff, concentrations of N and P from treated plots were significantly higher than those from the control. N was largely present as organic-N and NH4+-N for the slurry and manure (15 mg 1-1 and 5 mg 1-1 respectively), and as NH4+-N and N03--N for the inorganic fertiliser (20 mg 1-1 in both cases). P was largely present as P04--P (0.5 mg 1-1 for manure and slurry, 10 mg 1-1 for inorganic fertiliser), except for the manure treatment, where some 75 % of the total was organic-P. The 10 m buffer was effective in reducing the delivery of N and P in surface runoff, differences between the treatments and the control being rendered insignificant. This result was qualified in terms of the ratio of the buffer area to the treated area and the relatively low surface loads of N and P observed. N and P transport was then examined under less controlled conditions at the field to headwater catchment scale (4-18 ha). Sub-surface throughflow was associated with similar concentrations of N03--N (3-8 mg 1-1) and very low concentrations of P04--P (0.03-0.1 mg 1-1). These concentrations appeared to vary more in relation to seasonal changes in the level of discharge from the catchment than to changes in land-use, which implied that N and P in sub-surface throughflow was transport rather than supply limited. This was in broad agreement with observations made at the plot scale. At this larger scale, fluctuations in the concentrations of NH4+-N and P04--P occurred during rainfall events in response to what was probably the short-term occurrence of surface runoff from partial source areas of reduced infiltration capacity or variable source areas of saturation. These short-term fluctuations implied variations in topography and the distribution of surface derived N and P at the catchment scale. There was evidence of the occurrence of preferential flow during field experiments at both scales, which had important implications for the timing and magnitude of N and P transport. Finally, a functional and semi-distributed mathematical model was constructed to operate at the headwater catchment scale, and the effect of spatial variability in the interaction between land-use and topography on the transport of N and P was considered further.

This work was undertaken in order to determine the extent and nature of PAH pollution In a freshwater riverine environment. An extensive survey of sediment, water and aquatic organisms was carried out to investigate sources of PAH, physicochemical relationships occurring in the water and sediment, the extent of bioaccumulation and the potential for bioconcentration through the food chain. Laboratory studies were designed to investigate the likely mode and extent of uptake of PAH by Noemacheilus barbatulus (L.), Glossiphonia complanata (L.) and Lymnaea peregra (MUller), the ability of these species to metabolise PAH compounds and the extent of depuration. All sediment PAH profiles were similar and indicative of an anthropogenic pyrolytic origin. Urban/road runoff was considered to be a major influence on sediment PAH concentrations. point sources consisted of industrial waste sewage and runoff containing used engine oil. , All sites were affected by diffuse PAH pollution. At certain sites and at times of heavy rainfall this is overlain by a greater input of PAH to the sediment from point sources. Positive linear relationships have been demonstrated between total and individual PAH content and organiC matter content in sediments throughout a range of particle sizes. A similar PAH profile was found in each sediment size fraction, thus organisms selectively removing certain sized particles are not being exposed to differing ratios of PAH compounds. The river system seems to be in a state of nearequilibrium with regard to the partitioning of PAH between bedload sediment, suspended sediment, water and interstitial water. Adsorption and desorption processes occur in two phases, the first being almost instantaneous and the second being a slower approach to equilibrium. There is no- evidence of PAH's being bioconcentrated through the food chain. Uptake by tubificid worms occurs by the ingestion of contaminated sediment. Uptake by Cottus goblo (L.), N. barbatulus, L. peregru, G. complanata and Erpobdella octoculata (t.) occurs mainly through water and was shown to be rapid. N. barbatulus, L. peregra and G. complanat~ have the capacity to metabolise PAH compounds to harmful derivatives and it is likely that C. gobio and E. octoculata also have this capability. Depuration of BaP and metabolite compounds was relatively slow. Prolonged exposure to low levels of BaP in the environment may lead to a buildup of DaP and metabolite compounds in these organisms.