This project investigated the traditional treatment of chromium by oxidation-reduction reaction using Fe (II) and Mn (II). It was found that FE (II) was a potential remediation to stabilise chromium and reduce Cr (VI) to Cr (III), but Mn (II) oxidised Cr (III) to Cr (VI) mobilising it to the leachate. The characteristic of chromium leaching from soil was studied and showed there was fast release followed by a slow release. After a dry period the initial leachate had a high chromium concentration, this points out that the leaching of chromium is a long-term process. Those aspects of fast and slow release and the high chromium concentration at the initial pulse have been a concern for designing a system of fixed bed, low cost material such as (charcoal, coir, peat and wood bark) for adsorbing chromium from the leachate. The adsorption – desorption properties were studied, as both are of equal concern, and the Langmuir equation was applied for the various sorbent materials. Charcoal had a high percentage of Cr (VI) adsorbed, but on the other hand also had a high percentage of Cr (VI) desorbed. When applied to the column leach charcoal could not adsorb Cr (VI) properly. Wood bark had the lowest percentage of chromium released to the solution; therefore it was selected for further studies. The wood bark was studied with different contact times by both batch and flow through systems. The results showed that more chromium was adsorbed with longer contact time. The system using 2500g of wood bard completely retained chromium from a solution of about 100 litres of 30 mg Cr/l with a flow rate of 60 ml/h. The experimental results can be applied to larger scale systems; however, the system needs further development.

Study of a former industrial land, which was contaminated with chromium, was the major research topic of this study. A survey study of the land was made to evaluate the pH, electrical conductivity ;and percentage of organic matter of soils, available nutrients, total nutrients, available and total chromium and total other heavy metals in the soils. The survey also includes the total nutrients, total chromium and some other heavy metals in the plants and root mat. Soils throughout the site had high total chromium concentrations, high pHs and low plant available nitrogen and low vegetation yields. However, chromium was not detected in the plants. The effects of fertilizer additions were evaluated in two pot experiment studies of these soils using ryegrass as a test crop. The first pot experiment was carried out to look at the response of the soil samples to different combinations of N, P and K fertilizers to determine which fertilizer is limiting the plant growth. The response was measured by dry matter production. Nitrogen was shown to be the limiting factor for growth of the grass in these soils. Alleviating the limiting factor resulted in a yield increase. Since the trend of this increase can not be fully applied to all types of soils and spoils due to differences in nature of the material a second pot experiment was carried out to look at the response of the vegetation to addition of the different rates of nitrogen fertilizer. The results showed that the application of 100 /50 /50 of N/P/K kg/ha fertilizer could obtain the maximum yield for the site except for a soil sample from the base of the east side (sample 4) which did not respond to more than 50 of N kg/ha. Since the changes in the yields from these experiments were not affected by soil extractable chromium in the two experiments the possibility of the direct effect of chromium on plant growth was discounted. The occurrence of the nitrogen turnover and possible toxicity effects of chromium on these processes was assessed during a number of incubation studies. First of all the nitrogen supply power of the soils was evaluated using an incubation test for the nitrogen mineralization rate of the soils from this site. This experiment was done under aerobic conditions. An attempt was also made to look at possible volatization of ammonia due to the pH of these soils.

The effectiveness of using amendments in metal stabilization was determined, and their potential for remediation of contaminated soil was evaluated. A combined approach of evaluating soil and plant metal availability as well as microbial respiration was used as an indication of effectiveness of metal immobilization. This was done by sorption studies, incubation experiments in contaminated media, and greenhouse pot experiments. Batch sorption studies were conducted to evaluate the ability of bone meal, composts, peat, coir and wood bark to sorb Pb, Cu and Zn. Single sorption carried out over a metal concentration range of 0.1 mmol 1-1 using 0.001M and 0.1M Ca(NO3)2 as background electrolytes showed very high sorption of Pb, Cu and Zn by the amendments, but high background salt led to a reduction in the amount of metal sorbed by all amendments. Of the amendments tested, coir, compost and wood bark were most effective. Sorption was evaluated by applying the Langmuir equation, and maximum sorption values were calculated for all amendments. Theoretical maximum sorption of Pb was 87 mg g-1 (0.42 mmol g-1) by coir and green waste compost; Cu was 30 mg g-1 (0.47 mmol g-1) by green waste and general compost, while maximum Zn sorption was 14 mg g-1 (0.21 mmol g-1) in composts, closely followed by 13 mg g-1 (0.19 mmol g-1) in coir. Sorption mixed metal solutions of Pb, Cu and Zn was evaluated in a background salt of 0.001M Ca(NO3)2 only, either at equimolar concentrations of 0.1 mmol 1-1, equimolar concentrations of 1 mmol 1-1, or combinations of metals at either concentration. Metal sorption was reduced in the presence of other metals when compared with sorption in single metal solution. Pb sorption in equimolar solution of 0.1 mmol 1-1 was approximately 50% of that in single solution, Cu was 35%, while Zn was 40% if wood bark was not considered (wood bark sorption of Zn in low equimolar metal was not different from that in single Zn solution). The effect of metals on microbial respiration was evaluated in metal spiked amendments over a ten week period using metal solutions of Pb, Cu and Zn as contaminants. Pb, Cu and Zn toxicity led to an inhibition in CO2 evolved in all amendments, as addition of any amount of Pb, Cu or Zn led to a decrease I amount of CO2 evolved when compared with the non-contaminated amendments. The effect of increasing metal toxicity on CO2 evolution was reflected best in coir, where inhibition increased with an increase I metal concentration. In other contaminated amendments however, the inhibition was highly pronounced once there was metal contamination regardless of the metal concentration.

This research focuses on atmospheric and fluvial dispersal of Pb and Zn from an abandoned mine at Tyndrum, Scotland, which potentially acts as a significant source of contamination to the surrounding area. Concentrations of Pb and Zn in tree bark samples and peat profiles were measured to assess aerial deposition and fallout around the main mine site. Dispersal of contaminants through fluvial transport was assessed by analysis of river water and sediment on site and in the main river system draining the area, extending 25 km downstream from the mine area. Attempts were also made to determine whether the contamination is due to contemporary dispersal of material from the abandoned mine waste dumps, or originates from past deposition. Pb and Zn concentrations in tree bark from Scots pine (Pinus sylvestris) were high, but decreased with increasing distance up to approximately 100 m from the main dumpsite. Concentrations reduced markedly beyond this distance, possibly owing to the density of the forest stand. It is suggested that tree bark samples provide a useful medium for monitoring and quantifying contemporary aerial dispersal. Distributions of Pb and Zn within peat soil profiles provide information of past atmospheric deposition. Subsurface peaks of Pb and Zn can be linked to the period when mining was active during the 19th and early 20th centuries using the 210Pb dating method. The dispersal of Pb and Zn within the fluvial system was assessed by measuring concentrations of the contaminants in the solution, suspended particle and bed sediment phases. It was found that Pb and Zn are mainly transported in suspension in the 1.2-53 m suspended sediment fraction and are consequently deposited throughout the dispersion pathway in riverbed, lake and riverbank sediments. The contaminant Pb in an overbank core was confirmed as originating from the Tyndrum mine on the basis of its 206Pb/207Pb isotope ratio characteristics. This confirms a previous hypothesis that waste from the mine is an important contributor to Pb contamination over the entire length of the river system as far as Loch Tay. Thus overall, the investigation concludes that although the atmospheric dispersal of the contaminants is mostly contained within the vicinity of the Tyndrum main mine, the fluvial system remains a significant pathway for dispersal of Pb and Zn from the Tyndrum waste and that the presence of these metals within the river may persist for many years to come.

This research examined the impact which onshore windfarms sited on peat-based soils have on streamwater carbon (C), phosphorus (P) and nitrogen (N) dynamics. Significant disturbance to peatland arises through the excavation of borrow pits, construction of access tracks, insertion of turbine bases and associated deforestation during windfarm development – potentially increasing the transfer of C, P and N from terrestrial stores to the stream network. To identify which impacts occur, streamwater samples from nine catchments draining the Whitelee windfarm, Scotland, Europe’s largest onshore windfarm, were collected approximately bi-monthly from October 2007 to September 2010 during and after windfarm construction, building on pre-disturbance data from Waldron et al. (2009). The samples were analysed for dissolved organic carbon (DOC), particulate organic carbon (POC), total organic carbon (TOC), soluble reactive phosphorus (SRP), total phosphorus (TP) and nitrate (NO3-). Time series were constructed and annual streamwater exports were calculated so that inter-catchment and annual differences could be detected. DOC concentrations ranged from 2.9 mg L-1 to 57.1 mg L-1 and DOC exports ranged from 9.0 g m-2 yr-1 to 42.3 g m-2 yr-1. POC concentrations ranged from 0.09 mg L-1 to 23.4 mg L-1 with POC exports ranging from 0.80 g m-2 yr-1 to 3.93 g m-2 yr-1. DOC exhibited seasonality with maximum concentrations and exports towards the end of each summer. Harmonic regression analysis of the TOC data indicated a slight increase during the maximum phase of the seasonal cycle, coincident with windfarm-related disturbance observed in one catchment only. Regardless of windfarm development, streamwater DOC exports for four peatland-dominated catchments were observed to exceed typical values of C sequestration rate for Scottish peatlands over the four year time series. SRP concentrations ranged from 1 ug L-1 to 289 ug L-1 and exports from 12 mg m-2 yr-1 to 104 mg m-2 yr-1 with TP concentrations and exports ranging from 2 ug L-1 to 328 ug L-1 and exports from 25 mg m-2 yr-1 to 206 mg m-2 yr-1 respectively. In two catchments where windfarm-related clear-felling and extensive brash mulching were carried out, as much as a tenfold increase was observed from June 2007 in P concentration, coincident with the timings of windfarm-related forestry operations. The water quality status of these two catchments declined from “good” to “moderate” in terms of the Water Framework Directive (2000) UK Technical Advisory Group Environmental Standards for SRP in Rivers, and had still not shown a full recovery after a further two years. NO3- concentrations ranged from 0.001 mg L-1 to 2.44 mg L-1 and exports from 0.07 g m-2 yr-1 to 1.64 g m-2 yr-1. Harmonic regression analysis indicated a potential impact on streamwater NO3- concentration through a change in the seasonal pattern observed in three catchments during 2007-2008, coinciding with windfarm-related disturbance. To determine the most likely controls of C, P and N, a geographic information system (GIS) analysis was employed to describe the physiography of each catchment and to quantify the extent of windfarm-related disturbance. Multiple linear regression analysis was performed using median concentration and export for a low-disturbance phase from June 2006 to August 2007, and a maximum-disturbance phase from September 2007 until May 2009, with the catchment characteristics from the GIS analysis to identify potential impacts of windfarm-related disturbance. The percentage of the catchment which was HOST class 15 and 29, both peat-based soil types, was observed to influence streamwater C, with the proportion of the catchment which was pasture observed to influence streamwater N. Windfarm-related disturbances were also found to control streamwater dynamics. The extent of deforestation was observed to greatly increase streamwater P concentration and that there was a smaller increase in C, with consequent impacts on SRP and POC export. The source of this additional C and P resulted most likely from forestry operations, namely, clear-felling large areas of catchment and extensive brash mulching associated with the windfarm habitat restoration, with new organic material available for decomposition and the potential for erosion of the newly-exposed soil surface. Residual fertiliser used to establish the conifer trees, the reduced vegetation uptake of soil P and P release from the roots of the felled trees are three further sources of P in streamwater. The distance to the nearest disturbance was also found to influence streamwater dynamics. This research has shown that windfarm-related infrastructure can also influence streamwater chemistry, although exerting a less obvious impact: increasing access track length was correlated with decreasing POC and P concentration causing subsequent decreases in export. This is likely to be caused by the effective use of settlement ponds, flocculation blocks and ditch blocking in order to reduce the amount of particulate matter reaching the stream network and potentially through the adsorption of P by the access track construction material. Windfarm-related disturbance did not influence N dynamics; NO3- concentration was strongly correlated with HOST class 24 and the proportion of the catchment which was pasture, and NO3- exports were influenced by the flow length per catchment area, the percentage of coniferous forest cover and the extent of pasture. Two recommendations for best practice at future windfarm developments on peatland are made: firstly, monitor C, P and N in streamwater in all catchments before, during and after windfarm construction on C rich soils as part of EIA process in order to ensure that water quality is maintained in rivers, to determine whether discharges from windfarm developments should require to be licensed and to improve the accuracy of C payback time estimates; and secondly, minimise brash-mulching to reduce the impact on streamwater P. Furthermore, some suggestions for future research were proposed, including: plot studies to determine the best practice mitigation measures for P release in peatland catchments, longitudinal catchment studies, investigation of the relationship between access track construction material and streamwater dynamics, installation of continuous monitoring equipment along with a sampling regime which targets high flow events, examination of the changing stiochiometry, quantification of inorganic C and gaseous forms of C, and measuring catchment C sequestration rates.

Lakes play an important role in biosphere carbon dynamics. Though proportionally they constitute a small surface feature on the planet, in many cases lakes are subject to significant subsidies of organic material from their catchments. This input of allochthonous organic material, in addition to autochthonous organic material, has shown that lakes, particularly in temperate and boreal zones, can be heterotrophic systems and as such are net producers of CO2. Thus, understanding the magnitude of fluxes of carbon through these limnetic systems is important if their contribution to ecosystem / global carbon dynamics is to be elucidated. In this research two separate field campaigns were undertaken with the goal of understanding if, and exactly how significant secondary (bacterial) production utilising allochthonous carbon is to overall pelagic production in Loch Lomond, Scotland. Stable isotopic composition of dissolved inorganic carbon (DIC), dissolved oxygen (DO), dissolved organic carbon (DOC) and total dissolved nitrogen (TDN), along with their respective concentrations, were measured in a temporal and spatial survey. Range in [DIC] and δ13CDIC was consistent with that predicted by the shifting balance between autotrophic and heterotrophic pathways. [DIC] peaked in the summer / autumn (0.27 ± 0.09 and 0.17 ± 0.05 mM, south and north basins respectively), reflecting a period when bacterial processing of allochthonous material is high, and thus so is CO2 production. This effect was more pronounced in the mesotrophic south basin of the lake, compared to the oligotrophic north. Surface waters in the south, middle and north basins were generally saturated in CO2 beyond atmospheric equilibrium and thus sources of CO2 to the atmosphere. δ13CDIC and δ18ODO exhibited seasonal and spatial variability, probably also a result of changing metabolic balance and inflow characteristics. Spring / summer peaks in δ13CDIC (-5.1‰ epilimnion maximum) are indicative of photosynthetic incorporation, and vice versa in the autumn / winter (-13‰ hypolimnion minimum) points towards respiratory dominance. δ18ODO is enriched during respiratory utilisation and peaks in the autumn / winter months. Depletion in δ13CDIC coupled to concurrent enrichment in δ18ODO observed with increasing depth (particularly during lake stratification) is assumed to again be a result of a shift in metabolic process dominance from autotrophic to heterotrophic (Myrbo and Shapley 2006). Spatial variability was consistent with the varying trophic states between basins, e.g., most enriched δ13CDIC was recorded in the more productive south basin compared to the middle or north. Dissolved organic carbon concentration also changed with position in the lake. Highest concentrations in the south basin were linked to a shallow gradient catchment, draining base rich soils and agricultural land, compared to the steep sloped, base-poor catchment in the north. The greater quantities of dissolved organic carbon in the south suggested that if bacterial processing of allochthonous material was significant it would likely be most prevalent in the south. During the spatial survey consistent and significant heterogeneity in DIC, DO and DOC was recorded. Although the same degree of variability may not be associated with other, more mophometrically / hydrologically simple lakes, this work has shown consideration of this possibility is advisable. The second field campaign used direct measurements of algal and bacterial productivity, using labelled stable isotope incorporation methods, to elucidate the balance between autotrophic and heterotrophic processes. Primary production (PP) followed a predictable seasonal pattern, peaking in the spring and remaining relatively high until autumn. During this period primary production generally exceeded bacterial production (BP) per litre. During the winter this pattern was reversed. Using integrated estimates of both PP and BP this work showed that BP exceeded PP in the pelagic zone for the majority of the year, and over much of the lake’s extent. Even in the epilimnion BP was regularly the more significant process through the water column, and thus it is concluded Loch Lomond is a heterotrophic system and a likely source of CO2 to the atmosphere. The PP: BP ratio ranged from 0.6 – 0.8 in the north basin, and 0.4 to 0.6 in the south. On average for the whole lake, bacterial production exceeded primary production by between 2,700 and 4,400 kg C day-1. In total it was estimated that PP processes approximately 970 tonnes of carbon per year and BP between 2,300 and 2,800 tonnes of carbon per year. The proportion of total pelagic production fuelled by bacterial utilisation of allochthonous carbon changed throughout the year. During peaks of PP in the spring and summer much of the bacterial carbon demand was met by autochthonous supply. During the autumn / winter allochthonous carbon utilisation dominated pelagic production and regularly contributed over 90% of total pelagic production. Combining estimated quantities of allochthonous carbon utilised in the north and south basins per m2 (the middle basin taken as an intermediate between the two) and combining it with GIS data on lake volume, the total quantity of terrestrially derived carbon processed in Loch Lomond was estimated at approximately 3,300 ± 2,100 kg Callo day-1. Both spatial and temporal surveys of natural abundance stable isotope ratios, along with concurrent measurements of algal and bacterial production, have provided substantial evidence for the importance of allochthonous carbon in Loch Lomond. Even minimum estimates imply a system dominated by bacterial production, fuelled by a proportionally high quantity of terrestrial material, thus producing excess CO2, and potentially fluxing CO2 to the atmosphere.