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The speciation of trace metals plays a very important role in conditioning their biogeochemical cycles in the marine system. Their species are found to be strongly related to organic matters such as humic acids (HA) and fulvic acids (FA). This thesis aims to develop appropriate techniques to improve our understanding of the speciation of some trace metals, mainly in marine waters. Lead (Pb), cadmium (Cd) and chromium (Cr) which are widely used in industry were analytzed. The concentration of lead in uncontaminated seawater is between 10 and 100 pM, whilst in coastal waters it is higher at up to low nanomolar levels. Little is known about the chemical speciation of lead since it is difficult to be determined at picomolar levels. The work in this dissertation was to develop a suitable electrode and procedure to determine lead in seawater, with the objective that the electrode could be applied for in-situ measurement (without reagents) and for speciation. Several electrodes and materials were tested, including a solid bismuth rod and different microwire materials. Vibration was used to enhance mass transport, instead of solution stirring, to decrease detection limits and facilitate in-situ monitoring. The bismuth electrode was found to be suitable for monitoring lead in coastal waters: it is mercury-free and therefore environmentally friendly, but insufficiently sensitive for oceanic lead concentrations. Comparison of microwires of carbon, gold and silver showed that all of these bare electrodes give a signal for lead, but they suffer variable interference from cadmium, although this is minor if the cadmium concentration is lower than lead. A large improvement was obtained by coating the electrodes with mercury, which gave good peak resolution between cadmium and lead, and good sensitivity. The carbon and gold electrodes had good reproducibility and sensitivity when the mercury was renewed for each measurement. Once coated with mercury, the silver electrode formed amalgam with the silver which could not be completely removed. This electrode was thus not suitable to be used as a renewable mercury film electrode. However, as a permanently amalgamated silver electrode, it was found to have good sensitivity for lead, good separation from cadmium, and was stable for long time usage. This electrode, the silver amalgam microwire (SAM) electrode, was selected for further speciation study of Pb in oceanic waters. Optimum conditions for using the SAM electrode for trace lead detection in seawater involve the use of conditioning potentials. The limit of detection for lead was 4 pM lead in acidified seawater and 12 pM lead in seawater of pH 8. The higher limit of detection at pH 8 is due to the inorganic speciation at that pH. The SAM electrode was successfully used for pseudopolarography of lead to determine its organic complexation. This method was calibrated using model compounds and applied for the first time to estuarine, coastal and oceanic samples at natural concentrations of Pb. It was found that lead occurs mostly as a labile (reactive, organic) species, with a smaller fraction as a strongly organically bound species. The SAM electrode was also tested for chromium analysis using cathodic stripping voltammetry (CSV) in natural waters. Its detection limit is as good as the mercury drop electrode but reduces consumption of mercury.

The chemistry of aerosol particles is critical to the influence said particles have over human health, air quality and the distribution of nutrients across the world. Current models estimate that windborne dust represents the movement of thousands of teragrams of solid material of varying composition and solubility across continents and into the world’s oceans. Understanding the composition and surface reactivity of anthropogenic particles from industry, agriculture and vehicle emissions is vital to understanding their potential impact on the world, and the structure and behaviour of inhalable pharmaceuticals is a strong determinant of their efficacy. The following work examines a broad selection of natural and anthropogenic particulate samples with synchrotron-based techniques, including analysis of ship emissions collected directly from stacks for the first time. The effect of simulated atmospheric acid processing on the solubility of iron on coal fly ash is evaluated, and optical trapping is used in conjunction with analytical techniques to observe the influence of relative humidity on the properties of pharmaceutical aerosols and aqueous droplets containing fluorescent protein solutions.

Natural aquatic colloids (solids with dimensions between 1 nm and 1 micron) were studied in cave waters that feed secondary carbonates [speleothems]. Results show that during hydrologically quiescent periods, trace metal (Tr) binding (e.g. Cu, Ni, Co) is dominated by humic-like, natural organic matter (NOM), with the smallest NOM-Tr complexes (≤1 to ca. 4 nm diameter) being the least labile at high pH (>pH 10). Partitioning of NOM:Tr between solution and crystal occurs minimally for the strongest complexes, providing a measure of NOM adsorption. Rapid fluxes of coarse (>100 nm) soil organic matter (SOM) and Tr in dripwaters often follow peak infiltration events, the coarse fraction of NOM quenching fluorescence in finer fractions (<100 nm). Termed ‘high-flux’ (HF), this mode of NOM-metal transport contrasts with the humic-like or ‘low-flux’ (LF) mode both hydrologically and chemically, resulting in shifts in trace metal ratios (e.g. Cu:Ni) which are characteristic of changes in the competitive binding of metals for suitable sites in NOM, and diagnostic of qualitative shifts in NOM composition (i.e. relatively more aromatic/hydrophobic). This process becomes manifest in speleothems, resulting in high- and low-flux trace metal end-members and providing information on NOM aromaticity. Changes in HF:LF metal ratios in speleothems are linked to processes in soils which are ultimately mediated by climate (i.e. ambient temperature and infiltrating precipitation); they may provide information on infiltrating precipitation, on the occurrence of surface disturbances (e.g. deforestation) and NOM composition. HF:LF indices complement the existing array of speleothem climate proxies, but each specific system and setting must be understood to ensure their proper interpretation.

Landfill leachates contain a wide range of pollutants including potentially toxic metal(loids) e.g. arsenic. Current landfill risk assessment models predict the fate and transport of these pollutants in the environment, however they consider all species below 0.45 μm to be dissolved, thus the presence of these pollutants in colloidal form is not considered. In order to investigate the presence and distribution of metal(loids) within the nanocolloidal fraction (<100 nm), AF4 coupled with HR-ICP-MS was selected (alongside AFM and DLS) and optimised for use with landfill leachates. UV254 and Fluorescence spectroscopy were also used as detectors for AF4 to detect organic colloids. AF4-HR-ICP-MS analysis was carried out both offline (fraction collecting and subsequent HR-ICP-MS analysis) and online (interfacing the AF4 output directly with the HR-ICP-MS) with parameters optimised for lower MW particles. Online coupling provided a higher resolution analysis than the offline method. The concentration of elements within the AF4 system was found to be in flux and therefore baseline concentrations were established for each sample injection. Method repeatability and a recovery mass balance of each element were also established. The method was validated by fractionation of a MSW, an aged MSW and a MBT leachate. All three leachates were found to show the same nanocolloidal distribution with two distinct nanocolloid populations present: a low MW organic rich fraction; and a larger, less organic rich fraction consisting of a mixture of organic and inorganic particles. Metals predominated in the lower MW fraction associated with humic or fulvic-like particles. The similarities between the leachate metal distributions showed that treatment of leachate prior to landfill did not alter the colloidal characteristics. Preliminary results examining the effects of pH and ionic strength of metal distribution showed that pH had no effect; however the lowering of ionic strength appeared to cause aggregation of colloidal Fe particles, presumably due to the lower organic content, which appears to control the distribution of metals in this size fraction. This research highlights the importance for landfill risk assessments to be updated to include the presence of colloidal facilitated transport and the necessity for further particle transport studies to be conducted.

Freshwater systems are generally found to be sources of CO2 to the atmosphere and evasion of CO2 from fluvial systems is now recognised to be a significant component of the global carbon cycle. However detailed understanding of fluvial carbon dynamics and controls on the system is lacking and global coverage of published data is sparse, but thorough understanding across a broad range of locations is crucial if global carbon budgets are to be refined. This research addresses this lack of understanding by investigating the magnitude, controls and sources of CO2 efflux across five catchments with different catchment characteristics, global locations and climate-change sensitivities. In doing so new understanding is used to explore a novel method for large-scale upscaling of CO2 efflux, time series reconstruction of the source and magnitude of CO2 efflux and incorporation of an Arctic region into the global fluvial carbon budget. The magnitude of and controls on CO2 efflux are not well understood, although it has been suggested that increased flow velocity and turbulence can enhance CO2 efflux rates. This research uses direct and contemporaneous measurements of CO2 efflux (range: -3.53 to 107 μmol CO2 m−2 s−1), flow hydraulics (e.g. mean velocity range: 0.03 to 1.39 m s-1; shear Reynolds number range: 350 to 174000), and water chemistry (e.g. pCO2 range: 388 to 4660 ppm), at sites in three UK catchments to assess whether flow intensity (a term which is used to describe one or more measures of flow strength and turbulence) is a primary control on CO2 efflux. These field sites have been chosen as they have contrasting size and land use: Drumtee Water (DW), 5.7 km2 and rural, the River Kelvin (RK), 335 km2 and urban, and the River Etive (RE), remote and snow-melt influenced. At the more soil-dominated sites DW and RK, a strong positive logarithmic relationship exists between CO2 efflux and measures of flow intensity (e.g. shear Reynolds number, overall R2 = 0.69), but this relationship is strengthened by including pCO2 (overall R2 = 0.72). Flow intensity may have a key influence on CO2 influx, although data are limited. A method using visual classification of flow intensity shows promise for supporting large-scale upscaling of fluvial CO2 efflux, if classification of water surface state can be standardised. Movement of dissolved inorganic carbon (DIC) through the hydrological cycle is an important component of global carbon budgets, and how they may respond to changing climatic conditions. However uncertainty remains about the hydrological and biogeochemical controls on DIC transmission through a catchment. Using contemporaneous measurements of DIC concentration ([DIC]) and stable carbon isotope composition of the DIC pool (δ13CDIC), fluvial DIC at more soil dominated sites, DW and RK, is found to vary considerably in response to changes in catchment hydrology. At low flow groundwater dominates, and has similar composition in both systems ([DIC]: 1.5 mmol L-1 DW, 2.0 mmol L-1 RK; δ13CDIC: -9 ‰ DW and RK) indicating a common hydrogeological inheritance in DIC, that is comparable to that of other temperate and tropical locations. Differences in composition at high flow ([DIC]: 0.1 mmol L-1 DW, 1.0 mmol L-1 RK; δ13CDIC: -23 ‰ DW, -14 ‰ RK) reflect catchment land use, and a lower contribution of soil water to the DIC pool in the more urban catchment (RK). Measured diel cycles in DIC pool composition at DW indicate biological processes modify the pool, and time series reconstructions of pool composition and CO2 efflux at DW reveal seasonal- and flow-related patterns in this biological activity. Time series reconstructions also reveal that at DW terrestrial-aquatic-atmospheric carbon cycling is rapid during event flows, with large amounts of CO2, of soil-origin, effluxed to the atmosphere in relatively short periods of time. Conversely, at low flows, CO2 efflux is of smaller magnitude and primarily fuelled by groundwater, and terrestrial-aquatic-atmospheric carbon cycling is slower. The reconstructions allow for inter-year comparisons which are useful in assessing for behaviours in CO2 source and feedback that might be typical under climate change-induced changes in hydrology (e.g. wetter winters, drier summers, more frequent large flow events). Global ice melt and permafrost thaw are increasing due to climate change, effects of melting ice and thawing permafrost on the global carbon cycle, and carbon cycling dynamics of the melt/thaw waters are not well understood. Data from the River Etive has few similarities to that of DW and RK and indicates that snow- and ice- dominated systems may behave very differently to more soil-dominated systems in terms of magnitude and controls on efflux and sources and mixing of the DIC pool. This is confirmed by data collected from the melt/thaw waters of two cryospheric systems in Greenland: a Greenland Ice Sheet (GrIS) drainage river (Akuliarusiarsuup Kuua River, or AR) and the local permafrost-landscape surface-drainage systems (PLST). CO2 efflux appears independent of flow controls in both systems, and instead seems to be pCO2 limited (average pCO2: 115 ppm AR, 596 ppm PLST), with spatial variation in AR (efflux decreases downstream) and temporal variation in PLST (efflux decreases with melt season progression). The frequent occurrence of CO2 influx (measured in 64% and 14% of cases in AR and PLST respectively), which has rarely been reported from other rivers globally, reveals that Arctic fluvial systems can periodically act as net sinks of CO2 and this should be incorporated into global carbon budgets. The occurrence of CO2 influx, and dominance of air-water CO2 exchange in these low pCO2 systems, is reflected in the DIC pool composition which is 13C-enriched and approaches isotopic equilibrium with the atmosphere (~0 ‰), and indicates that soil and ground water contributes little to the DIC pool under frozen ground conditions. Radiocarbon analysis gives further insight into the source of carbon in these systems, revealing that the GrIS is releasing old DOC (~5200 to 6600 yrs BP) upon melting, which is considered to be highly biolabile and may prime bacterial activity and feedback to climate change, and meltwaters are returning old carbon (800 to 960 yrs BP) to the atmosphere via CO2 efflux. Thus it appears that climate change (via melting ice sheets) may be a driver of the age of atmospheric carbon composition. The effluxed CO2 being less old than the DOC indicates the source of CO2 efflux is a mixed pool of respired/UV-oxidised old DOC and modern atmospheric CO2 from drawdown. In contrast to GrIS meltwaters, and the permafrost of other global locations (e.g. the Siberian Yedoma deposits), the permafrost landscape of the Kangerlussuaq region of Greenland is cycling modern carbon and appears not to be degrading, as old carbon is not found in, or degassed from, the fluvial systems. In summary this research contributes to a greater understanding of fluvial carbon dynamics and the processes controlling the return of CO2 to the atmosphere via efflux, across an array of catchment types, sizes, land uses and global locations, and makes contributions of novel data to a number of areas of fluvial carbon cycling research where there are scarcities. Marked differences in the fluvial carbon cycling dynamics of cryospheric and snow-melt dominated systems compared to soil-dominated terrestrial systems are uncovered, novel upscaling attempts made using new findings of the research, and a number of exciting new research directions and opportunities that could enhance the findings of this work are identified. Overall, this research takes steps towards a greater understanding of fluvial carbon cycling dynamics on a global scale and improved projections of the likely response of fluvial systems to climate change, ultimately aiding the community to be more prepared for what our shifting climate will bring.

The full extent of a landscape’s resilience to the environmental impact of siting wind-based renewables on peats is currently unknown. This research explores if windfarm construction activities have caused disturbance by investigating; time series of fluvial carbon (C) and nutrient concentrations; constructing aquatic organic C fluxes, before, during and after the windfarm construction period. Additionally, C sequestration rates of peat and nearby lake sediments (Loch Brora) were calculated to provide a historical context to, i) calculated aquatic C fluxes and ii) sediment export from surrounding catchments, considering both a catchment hosting the windfarm construction and one that does not. Furthermore, the effectiveness of a peatland restoration technique, drain-blocking, was assessed as a means of undertaking a whole system approach to assessing the potential impact of the windfarm development, considering how these management strategies can help mitigate potential C losses associated with construction. The research field site was located on the Gordonbush Estate, near Brora, where construction started in July 2010 (the same time this research began) on Scottish and Sothern Energy Renewables (SSER) 35 turbine windfarm. Construction work finished in May 2012 and data collection continued until September 2014. Throughout this period, fieldwork was focussed on storm event sampling (collecting samples for dissolved organic carbon (DOC), particulate organic carbon (POC), total phosphorous (TP), soluble reactive phosphorous (SRP) and total oxidised nitrogen (TON)), collecting peat and lake sediment cores, samples of modern day sediment export and monitoring water table depth in an area where old drainage channels were blocked as part of a peatland restoration initiative. Three river catchments were studied, two affected by windfarm construction activities (GB10 and GB11) and one control site (GB12), DOC concentrations ranged from 1.1 mg l-1 to 48.3 mg l-1, POC from <0.1 mg l-1 to 21.3 mg l-1, TP from <0.5 µg l-1 to 264 µg l-1, SRP from <0.5 µg l-1 to 39 µg l-1 and TON from <1 µg l-1 to 141 µg l-1. These were all within ranges of macronutrient concentrations measured at other northern temperate peatland sites. Comparing macronutrient concentrations between catchments, generally GB10 > GB11 > GB12 for all determinants. Seasonal patterns in fluvial macronutrient concentrations were observed at Gordonbush: summer maxima and winter minima in DOC and TP concentrations and the opposite trend in TON concentrations. SRP data collected indicates a legacy of forest felling in the Bull Burn Plantation has contributed to increased concentration in the Allt Mhuilin river (GB10) compared to the two other catchments, Allt Smeorail (GB11) and Old Town Burn (GB12) where no forest felling occurred during the data collection period. Differences in DOC and TP concentration in Allt Mhuilin compared to other catchments could also be related to forest felling activities but catchment characteristics such as peat coverage may have also influenced results. For all relevant measures of water quality, macronutrient concentrations from Gordonbush shows studied streams consistently achieved “Good” or “High” status throughout the data collection period. Apart from the legacy of forest felling, a discernible impact of windfarm construction was not observed from macronutrient concentration time series. Calculating annual aquatic C fluxes from studied catchments offered a means of assessing potential impact. Various techniques of estimating fluxes were explored but splitting storm event DOC and POC data based on time of year and whether samples were collected on the rising or falling limbs were concluded to give the best estimates. Calculated fluxes ranged from 3 – 38 g C m-2 yr-1 and DOC consistently accounted for ~90% of total aquatic C export. These values were within limits of other C flux based studies from peatlands but the time series constructed at Gordonbush suggested windfarm construction, between July 2010 and May 2012, may have contributed to an increase in aquatic C export from affected catchments during this time, relative to the control site. Long term C sequestration rates from within the Gordonbush estate were 20-25 g C m-2 yr-1, the same magnitude as aquatic organic C fluxes. However, peat C sequestration was shown to be variable over the last ~9000 years since Scottish peatlands became established, with rates ranging from 10-60 g C m-2 yr-1. Controls on this variation are likely climatic with delivery of moisture influenced by the North Atlantic Oscillation (NAO) a key factor. Calculated lake C sequestration also varied over time, 22-82 g C m-2 yr-1 but an inconclusive radiocarbon dating chronology meant historical comparison of C export dynamics between the, C ‘source’, peatland to the, C ‘sink’, lake was unfortunately not possible. Modern day sedimentary export data showed higher sediment yields from windfarm affected catchment than the control site. Physical characteristics varied considerably between the two catchments so although this observation could not definitively be attributed to a direct windfarm impact, it remains a possibility. Whilst studying and quantifying the impact of drain blocking, manual measurements of water table depth (WTD) ranged between -53 cm to +14 cm in dip-wells and -36 cm to +20 cm in automated logging pressure transducers. The response of WTD throughout both data sets indicates meteorological conditions were more influential as a factor controlling peat hydrology across the site compared to topography. Manual measurements from dip-wells shows the drainage channels investigated (~0.5-0.7 m deep and ~0.5 m wide) had the greatest influence on effect WTD 0-2 m from the main channel but no statistically significant difference was detected in mean WTDs measurements before or after blocking, in relation to distance from the drainage channels themselves or comparisons between drained and un-drained (control) areas. However, data from PTs indicate the net effect of multiple parallel drains can cause water table drawdown at a significant distance, ~ 25 m, from the drainage channel. This is an important finding as methodology used to calculate the C ‘payback time’ of windfarms utilises the lateral drainage extent of peat when turbines bases are excavated. Drain blocking had no obvious effect (either positive or negative) on WTDs however it is acknowledged positive effects can take up to five years, after blocking has taken place, to be observed. Maximum DOC concentrations increased the year after blocking however this result has been recorded at other sites and the exceptionally dry summer of 2013 could have contributed to the noticed increased by promoting more peat oxidation and subsequently DOC production. There was no statistically significant difference between [DOC] collected up and downstream of the drainage channel inputs for samples collected before and after blocking. This suggests drain-blocking has had little impact on the larger site [DOC] signature one year after drain-blocking. However, as discharge from drainage channels was not measured, a potential reduction in overall DOC export could not be fully assessed and this is a highlighted future research need. Combining averages of aquatic organic C fluxes and peat C sequestration rates calculated it is estimated net ecosystem exchange would have to be between -30 to -50 g C m-2 yr-1 for Gordonbush to be classed as a C ‘sink’. If the observed increases in sedimentary export could be attributed to windfarm construction, Loch Brora is unlikely to act as a strong C sink for any potential increased losses as it is estimated ~90% of POC exported is not sequestered on a long-term basis in the lake sediments. It has recently been recommended windfarms should not be developed on peatlands due to the marginal C savings achieved as our future energy mix changes (Smith et al., 2014). However, if similar projects are granted planning permission then findings from this research support the following recommendations: installation of buffer zones around areas of felled forestry to reduce nutrient export into surrounding streams; implementation of a water quality monitoring programme to assess impact of windfarm construction during construction and a period afterwards as it is still unclear from this research if there will be any lasting effects; installation of silt traps to reduce aquatic sediment export and disturbance; limit any high density excavation of drainage channels as the effects of water draw-down could be quite extensive; in addition, blocking all historical drainage channels and retaining as much moisture as possible within, and surrounding, areas of degraded peatland can increase long-term peat C sequestration rates and offset C losses experienced during construction. This research has been funded by SSER, Engineering and Physical Sciences Research Council (EPSRC) and Energy Technology Partnership (ETP). This research has been undertaken and supported at the University of Glasgow within the College of Science and Engineering, specifically aligned to the work of the Carbon Landscapes and Drainage (CLAD) research group headed by Prof. Susan Waldron in the School of Geographical and Earth Sciences. Finally, this research has also been supported in partnership with Stirling University.

Dimethylsulphoniopropionate (DMSP) is a dimethylated sulphur compound that appears to be produced by most marine algae and is a major component of the marine sulphur cycle. The majority of research to date has focused on the production of DMSP and its major breakdown product, the climatically important gas dimethylsulphide (DMS) (collectively DMS/P), by phytoplankton in the open ocean. A number of functions for intracellular DMSP (DMSPi) in phytoplankton have been identified and the cycling of DMS/P appears to be critical for ecosystem function. However, mechanisms for the production and release of DMS/P in the coastal ocean are poorly understood, despite the region’s economic and ecological importance. Coralline algal habitats (e.g. maerl beds, coral reefs, seagrass meadows, kelp forests) are distributed throughout the coastal oceans worldwide. Their three-dimensional structure supports high biodiversity and provides numerous services, generating considerable economic wealth. DMSPi in coralline algae is known to be high, thus coralline algal habitats may be critical components of the coastal sulphur cycle. This research aimed to improve our understanding of the production of DMS/P by coralline algal habitats by investigating (1) natural spatiotemporal variation and (2) the influence of environmental pressures. This was achieved through a number of laboratory and field-based studies, utilising modern and well-established techniques. The first objective of this research was to better understand the photosynthesis of red coralline algae (Chapter 3), as the algal precursor to DMSPi is methionine, a product of photosynthesis. The photosynthetic characteristics of coralline algae exhibited acclimation to changing light conditions (e.g. over a diurnal cycle or between natural and static lighting conditions). Further, for the species tested, coralline algae are often subjected to light-saturating natural conditions, therefore requiring efficient photo-protective mechanisms, which may include DMSPi regulation. On a global scale, DMSPi in coralline algae may decline with latitude, reinforcing the role of DMSPi as an antioxidant (Chapter 4). At smaller spatial scales, DMS/P production, release and recycling mechanisms were apparent in a number of habitat types (Chapter 4). A strong seasonal trend in DMS/P was also observed at a Scottish maerl bed, driven by water temperature and cloud cover (Chapter 5). Annually averaged DMS and DMSP concentrations were 230% and 700% respectively higher than the open ocean, highlighting the potential importance of the coastal ocean in the marine sulphur cycle (Chapter 5). The influence of environmental pressures (decreased salinity, variable pH and grazing) on DMS/P production by coralline algal habitats was examined (Chapters 6 – 8). In agreement with the phytoplankton literature, a chronic, but not acute, reduction in salinity led to a significant decline in coralline algal DMSPi concentrations and a sinking of the surface epithelial cells but no apparent impact on photosynthesis (Chapter 6). In the naturally variable tropical reef environment, calcifying algae continually regulated DMSPi concentrations in response to the diurnal cycling of carbonate saturation state (Chapter 7), suggesting that DMSPi may be enhanced under low pH regimes to compensate for enhanced oxidant production. Under low pH conditions, cracks were observed between the surface epithelial cells of coralline algae, potentially allowing DMSPi to leak from the cells (Chapter 7). In the field, grazing by urchins appeared to facilitate the release of DMS/P from kelp in coralline algal habitats (Chapter 8). In the laboratory, DMSPi in coralline algae increased in response to chemical cues from grazers rather than direct grazing activity, as had been previously proposed. Prior to this research, little information was available on DMS/P concentrations in coralline algal habitats. The marine sulphur cycle may impact climate regulation and ecosystem function on a global scale. This research provides a comprehensive source of information on the importance of coralline algal habitats in the marine sulphur cycle by examining natural variability and potential changes in response to environmental perturbations. This work will form a baseline for continued research in this field, investigating, for example, the impact of multiple stressors on DMS/P production, release and recycling in coastal marine habitats.

Phytoremediation is a plant-based remediation process for treating contaminated soils. The overall aim of this thesis was to determine whether phytoremediation could be applied to co-contaminated soils. Copper (Cu) and pyrene, and Chromium (Cr) and Benzo[a]pyrene (B[a]P) were used as contaminants. The first study involved the joint effect of Cu and pyrene or Cr and B[a]P on the early seedling growth of Lolium perenne. Results suggest that co-contamination showed several types of interactions for seedling growth with different combinations of the pollutants. The second study involved the role Brassica juncea and Zea mays during the remediation of Cu and/or pyrene, and Cr and/or B[a]P co-contaminated soils respectively. Brassica juncea and Z. mays showed contrasting results for metal and polycyclic aromatic hydrocarbon (PAH) remediation. The third study compared freshly spiked soils and aged soils. Ageing affected the plant biomass, metal phytoextraction and PAH dissipation in different ways when compared to fresh soils. Finally, the efficiency of ethylenediaminetetraacetic acid-EDTA and/or citric acid as chelators in co-contaminated soils was studied. The combined application of EDTA and citric acid was more effective in co-contaminated soils. The overall findings from the four studies suggest that phytoremediation could be applied to co-contaminated soils.

There is a requirement to assess the safety of chemicals to both 'man' and the environment. Traditionally this was determined through the use of animal testing. However, there is an increased need to develop alternatives to animal testing for the determination of toxicity due to ethical and legislative reasons. One approach to replacing the use of animals is the application of computational methods. These include Quantitative Structure-Activity Relationships ((Q)SARs), which are the formalisation of the relationship of the effects (e.g. toxicity) for a series of chemicals and their physico-chemical and structural properties. Most QSARs for toxicity require knowledge of a chemicals hydrophobicity. Traditionally hydrophobicity has been characterised by the logarithm of the octanol/water partition coefficient (log P). Current experimental and predictive methods are limited in terms of applicability for compounds with extreme log P values, compounds ionised under the conditions of analysis and surface active agents. An alternative technique to assess hydrophobicity is Immobilised Artificial Membrane High Performance Liquid Chromatography (IAM-HPLC). The IAM stationary phase was developed initially to mimic biological membranes more realistically than octanol/water partitioning. This study has collated published literature values for the IAM retention index (kIAM), including details of the experimental procedure, into a database. The database includes 1910 values for 647 compounds. The effect of variability of experimental procedure on reported values was investigated. Key experimental parameters were identified that ensure comparable log kIAM values. An IAM-HPLC method was optimised; the HPLC method covers a range of hydrophobicities (log P of -1.35 to 6.03) and includes both unionised and ionised compounds under the conditions of analysis. Additionally the method has been demonstrated to be robust across system of analysis, column and stationary phase batch. The assessment of robustness increases confidence in the log kIAM (pH 7.4) values for 66 aliphatic and aromatic compounds determined as part of this work. Methods to predict log klAM (pH 7.4) were investigated. Both a fragment and correction factor method, based on theoretical structural features, and a 'classical' descriptor based QSAR approach, was applied to both the experimental log kIAM (pH 7.4) values determined in this work and comparable values collated from the literature. QSARs have been developed using log klAM as a descriptor to predict the ability of a chemical to cross the skin barrier and to predict various acute aquatic toxicity endpoints, using published skin absorption and ecotoxicity data respectively.