Adsorption and voltammetry of butyltin compounds

The adsorption of tributyltin onto materials commonly used for the construction of sampling and analytical equipment from aqueous solutions of varying ionic composition has been examined. The adsorption appears to be controlled by non-polar interactions between tributyltin and the surface involved. Since the speciation and hence polarity of tributyltin is affected by the ionic composition of the medium, the extent of adsorption is affected by the salinity and pH of a sample. The adsorption is rapid and, unless strategies are adopted to eliminate its effects, may render analytical results invalid. The electrochemistry of tributyltin, dibutyltin and monobutyltin, individually and in mixtures, has been investigated in aqueous media at mercury electrodes. The basic electrochemistry of each compound is summarised by the reaction BunSn (4-n)+ + (4-n)e- right left harpoons BunSn where n is the number of butyl groups attached to the tin atom. However, the electrochemistry of each compound is largely confined to the surface of the mercury electrode, and the simplicity of the above reaction is disrupted by polymerisation reactions and by butyl exchange processes occurring with the mercury electrode. When mixtures of butyltin compounds are present, the various processes that occur for each individual compound interfere with each other. A direct voltaminetric method for the determination of butyltin compounds in natural waters is therefore probably not possible.

Trace metal speciation in the Pieman River catchment, western Tasmania

The Pieman River catchment has seen continuous mining of economic deposits of gold, silver, lead, copper, zinc and tin since the 1870’s. Tributaries of this river which receive mining effluent, either directly or from acid mine drainage (AMID), have total metal concentrations considerably above background levels and are of regulatory concern. The lower Pieman River is however classified as a State Reserve in which recreational fishing and tourism are the major activities. It is therefore important that water entering the lower Pieman River from upstream hydroelectric impoundments is of high quality. Metals in natural waters exist in a variety of dissolved, colloidal and particulate forms. The bioavailability and hence toxicity of heavy metal pollutants is very dependant on their physico form. Knowledge of the speciation of a metal in natural aquatic environments is therefore necessary for understanding its geochemical behaviour and biological availability. Complexation of metal ions by natural ligands in aquatic systems is believed to play a significant role in controlling their chemical speciation. This study has investigated temporal and spatial variation in complexation of metal ions in the Pieman River. The influence of pH, temperature, organic matter, salinity, ionic strength and time has been investigated in a series of field studies and in laboratory-based experiments which simulated natural and anthropogenic disturbances. Labile metals were measured using two techniques in various freshwater and estuarine environments. Diffusive gradients in thin-films (DGT) allowed in situ measurement of solution speciation whilst differential pulse anodic stripping voltammetry (DPASV) was used to measure labile metal species in water samples collected from the catchment. Organic complexation was found to be a significant regulating mechanism for copper speciation and the copper-binding ligand concentration usually exceeded the total copper concentration in the river water. Complexation was highly dependent on pH and at the river-seawater interface was also regulated by salinity, probably as a result of competitive complexation by major ions in seawater (eg. Ca 2+ ions). Zinc complexation was also evident, however total zinc concentrations in the water column often far exceeded the potential binding capacity of available ligands. In addition to organic complexation, Zn speciation may also be associated with adsorption by flocculated or resuspended colloidal Mn and/or Fe oxyhydroxides. Metal ion complexation and hence speciation was found to be highly variable within the Pieman River catchment. This presents major difficulties for environmental managers, as it is therefore not possible to make catchment-wide assumptions about the bioavailability of these metals. These results emphasise the importance of site-specific sampling protocols and speciation testing, ideally incorporating continuous, in situ monitoring.

Recovery of estuaries following disturbance by pollutants

The recovery of a heavily polluted estuary was assessed by comparing the structure of its intertidal community with six other estuaries. Results indicated that some recovery had occurred, however improvements in the study methodology were required to further clarify the ecological status of the creek.

Ecology of feral cats (Felis catus) at a refuse dump in coastal southern Victoria, Australia

The ecology and behaviour of a colony of feral cats was studied at a refuse dump at Anglesea, Victoria. Research found that the cats lived at the dump all year round, congregating on the exposed refuse at night. Here they fed mainly on meat scraps, supplementing their diet with local wildlife. Aggression between individual cats was rare, allowing them to live as a colony, rather than as solitary individuals. Although female cats were fecund, breeding success was low, preventing a steady increase in the population. No justification for controlling these cats could be found at this time.

The combined effect of light intensity and temperature on the chlorophyll and carotenoid pigments of phytoplankton

Chlorophyll a and other photosynthetic pigments are used as indicators of phytoplankton biomass, composition and physiological state. Extraction and HPLC procedures were developed to analyse for chlorophyll and carotenoid pigments. The effect of the environment on pigment production must be quantified before the pigments can be used to accurately estimate biomass or quantitatively describe phytoplankton composition.

Aluminium smelter wastewater : groundwater fluoride fate

This study assessed the viability of utilising groundwater systems to manage Portland Aluminium's trade waste water stream. A mathematical groundwater model was created to assess laboratory and field results. Fluoride was modelled for spatio-temporal longevity in the system. All models indicate that fluoride will ultimately exit the site to the seaward boundary.

Degradation of VOCs using non-film titania in a hybrid process

This study reports the preparation and characterization of titanium dioxide (TiO2)-based non-film catalysts, reactor design and their utilization in a hybrid dynamic degradation of acetone and toluene. The behaviours of deactivation and regeneration of catalysts are explored as well. The regression equations of conversion rate in differing operating modes are concluded.

Hydrologic model for the Woady Yaloak River catchment

A hydrologic model was developed to predict the long-term impacts of land use change on the hydrology of the Woady Yaloak River catchment. The model can be used by catchment managers to formulate management decisions about land use changes expected to occur across the catchment in the future.

The effect of increased water prices on construction

The research aimed to investigate the effect an increase in water prices would have on construction. It was found that while there is a considerable amount of water embodied in construction the actual effect of a water tax on construction would be minimal unless implemented at the highest rate.

Stabilisation of brown coal fly ash using geopolymers

This research explores geopolymer technology as a means of stabilising fly ash from power stations. By controlling the synthesis process, geopolymeric materials incorporating fly ash were synthesised. Successful stabilisation of strontium and barium was achieved, though attributed to side reactions. The geopolymer did not contribute significantly to stabilisation of fly ash.