A des concentrations supra-optimales, les métaux lourds essentiels (comme le Cu, Zn ou Ni) ou les métaux lourds non essentiels (comme le Cd, Pb ou Hg) peuvent être toxiques. La contamination des sols et de l’eau par des métaux lourds toxiques est un problème mondial qui peut nuire à l’environnement et à la santé humaine. En particulier, le cadmium est l’un des métaux lourds les plus toxiques pour les organismes. L’utilisation de plantes pour extraire ou dégrader les polluants (dans le cas de polluants organiques) constitue une stratégie intéressante, à bas coût et respectueuse de l’environnement pour remédier au problème des sites pollués. Pour une phytoextraction des métaux lourds, les plantes doivent avoir une croissance rapide, développer des biomasses importantes et accumuler des niveaux élevés de métaux lourds dans leurs parties récoltables. En d’autres termes, elles doivent être très tolérantes et accumulatrices. Une alternative consiste à utiliser des plantes tolérantes de façon à contenir la pollution (pour réduire la biodisponibilité et limiter la dispersion dans l’environnement). Des gènes d’une banque d’ADNc synthétisée à partir d’un hyperaccumulateur Cd/Zn Thlaspi caerulescens, dont l’expression augmente la tolérance au Cd dans les cellules, ont été identifiés. Dans cette thèse de Doctorat, notre but est d’une part de contribuer à la caractérisation fonctionnelle de ces gènes et d’autre part de créer de nouveaux outils en vue d’améliorer les techniques de phytoremédiation. Nous avons sélectionné deux séquences codant pour des protéines riches en cystéines, capables de lier certains métaux lourds et d’augmenter la tolérance au cadmium :une métallothionéine de type 3 (Tc-MT3) et une métallothionéine potentielle (MRP) provenant d’un organisme contaminant de la banque d’ADNc. Nous avons générer des lignées de tabac exprimant TcMT3 ou MRP, sous le contrôle d’un promoteur fort et constitutif, CaMV35S. Les plantes MT3 et MRP ont présenté un retard de croissance par rapport aux plantes contrôles, en croissance sur milieu non contaminé. Différents tests de croissance ont été réalisés en présence d’excès de Zn, Ni ou Cu et dans des milieux modifié avec du Cd. Nous avons remarqué qu’en présence de plusieurs métaux lourds en particulier le Cu et le Cd, les plantes Tc-MT3 et MRP étaient plus tolérantes que les plantes contrôles. La tolérance au Cd était la plus augmentée dans les plantes MRP. Les plantes Tc-MT3 ou MRP semblaient avoir un besoin en métaux lourds plus grand. L’accumulation des métaux lourds dans les parties aériennes n’était pas augmentée mais la minéralomasse des plantes Tc-MT3 et MRP l’était sur sol contaminé de la Région Bruxelloise. Une analyse biochimique a confirmé un changement dans le statu rédox de ces plantes. Une tendance à un statut plus oxydant a été observée dans les milieux non contaminés. Enfin, l’induction d’une métallochaperonne (CCH) du Cu indique une diminution de la biodisponibilité de cet élément, alors que la concentration totale n’est pas altérée. Il semble donc que pour la première fois, des métallothionéines puissent entrer en compétition avec une métallochaperonne végétale. Cette compétition pour les métaux pourrait être à l’origine de l’altération du statut rédox, du retard de croissance ainsi que de la meilleure tolérance aux métaux lourds. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

The contamination of heavy metals in the environment is a looming concern worldwide. Egeria densa (Planch) (Submerged aquatic plant) from two ponds: Site A with co-ordinates (32º 48’22.04”S; 26°48’58.79” E) and Site B with co-ordinates (32°48’33.25”S; 26°48’33.25”S) in Alice (Eastern Cape) was evaluated for its ability to absorb heavy metals, phytochemical constituents, antimicrobial activity and ultra-structure using standard analytic procedures. Cadmium (Cd), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), and zinc (Zn) were measured in water, sediments and plant. The concentrations of these metal elements were determined with use of Inductively Coupled Plasma- Optical Emission Spectrometry (ICP-OES). In sediments, the heavy metals (mg/kg) decreased in the order of their average concentration as follows: Fe (40.320) > Zn (1.259) > Pb (0.564) > Mn (0.186) > Cu (0.037) in Pond 1 whereas in Pond 2 Fe (61.527) > Cd (0.999) > Mn (0.648) > Pb (0.586) > Zn (0.156) > Cu (0.045). The highest concentration of Fe was detected in both sites and Cu being the least. The concentrations of the metals in the plants sample (from Pond 1) were found in order of Mn > Pb > Cu > Fe whereas cadmium and zinc were not detected, while the concentration in Pond 2 decreases in order of Zn > Mn > Pb > Cd > Fe > Cu. In the water samples, concentrations of heavy metals (mg/L) decreased in the order of their average concentrations as follows: Pb (35.36) > Fe (3.07) > Mn (0.238) > Cu (0.104), both cadmium and zinc were below the limit of detection in Pond 1, whereas in Pond 2 the concentrations decreased as follows: Pb (13.033) >Fe (1.69) > Cu (0.270) > Mn (0.248) > Cd (0.004) and Zinc was not detected. Phytochemical analyses of the plant extracts revealed the presence of phenols, flavonoids, proanthocyanidin, flavonols, saponins, alkaloid and tannins in all the extracts (water, acetone and n-hexane). Both acetone and water extracts, showed high concentration of proanthocyanidin, while tannin was the lowest in acetone extract. Antimicrobial evaluation using, Gram positive (Staphylococcus aureus, Bacillus pumilus, Bacillus cereus, Streptococcus pyogenes, Enterococcus faecalis) and Gram negative (Klebsiella pneumonia, Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris and Serratia marcescens) bacteria showed negative results for all the strain, except Streptococcus pyogenes which was inhibited at MIC of 0.1 mg/ml. Scanning electron microscopy (SEM) of ultra-structure of Egeria densa, showed that certain bacteria attached to the leaf, However more work has to be done on E. densa to verify the mechanism by which it accumulates heavy metals. The study shows that E. densa has a potential of accumulating heavy metals especial Manganese in plant.

MSc (Chemistry) / Department of Chemistry / Increasing health and environmental concern about the effects of most toxic heavy metals emitted from cement plants in developing countries, which are going through rapid development, has led to this study. Cement industry in South Africa has been the primary industry over the years contributing immensely to infrastructure development and economic growth. Cement has been used to build many large cities, industries, homes, bridges and shopping malls around the country and still continue to be used by constructors. At this point, there has been no other substitute for cement and it will continue to be produced for decades to come. Unfortunately, this industry is now known to be amongst the major environmental polluters. Less has been done to address the adverse effects that comes with the production of cement, especially in the developing countries where there is huge demand for cement. This study focusses on dust emanating from production processes especially cement manufacturing from rotary kiln stage during production of cement and cement bricks. The production of cement and cement bricks generate dust, which is distributed over large areas of the environment. In South Africa, there are a number of factories in operation without proper planning of pollution prevention and compliance to environmental legislature. Since the production of cement is associated with the release of dust containing heavy metals, the dust is atmospherically deposited on the land, water surfaces and residential areas. The soil, street pavements, wetlands and water surfaces have become the sinks of heavy metals. Heavy metals that are being deposited include arsenic, cadmium, chromium, manganese, cobalt, copper, barium, antimony, selenium, vanadium, nickel and lead. Such metals pose health threat to the animals, plants and human beings living around the cement factories. These metals can easily be leached out from the soil and washed to the water bodies causing water pollution. Old processing techniques have been found to be inefficient to prevent emission of dust to the atmosphere. Hence, the emission of the toxic heavy metals to the environment was uncontrollable. Since cement is used to produce cement bricks, the whole process is subjected to heavy metals being discharged with dust from the factory to the surrounding environment. Four papers (I, II, III and V) were written to assess the level of heavy metals. In paper I, water and plants samples (Bidens Pilosa, Phragimites Australis and Xanthium Strumarium) were collected in the Mvudi River nearby a cement factory. Sampling was done before, within and after the wetland. Samples were digested with nitric acid for analysis. The concentration of zinc, chromium and lead were determined in the samples using a graphite furnace atomic absorption spectromentry. Results showed that the concentrations of zinc, chromium and lead were above the permissible limits in different parts of the plants analysed and water. The pH of water samples were below the threshold recommended by Department of water affairs and forestry (DWAF) and World health organisation (WHO). In paper II, seven soils at different distance, seven soils below soil surface at seven different layers and a bulk were sampled nearest to the cement brick making factory. Bulk sample was separated into five particle sizes (2 - 3 mm, 1 - 2 mm, 0.5 - 1 mm, 0.5 mm). Five sediments samples were also collected before, within and after the wetland along Mvudi river. Modified three step BCR sequential extraction was applied to the 23 samples in order to obtain the metal distribution in the samples. Heavy metal concentrations of nickel and chromium were determined using graphite atomic absorption spectrometry. Results showed that the levels of nickel and chromium exceeded the permissible limits recommended by WHO. Elevated concentrations Ni and Cr in soil and sediments also showed that the cement brick making factory is the main source of pollution in the area. To assess the contribution of cement dust to heavy metal pollution from the cement plants to the surrounding environment, two studies were carried out in the vicinity of two cement plants one in Thabazimbi and the other in Pretoria. Two papers (III and IV) were written from the studies and were summarised as follows: In paper III, dust samples were collected along the road leading to and passing by the cement plant in Thabazimbi, South Africa. The samples were collected using a brush and pan into sampling bags. After sampling dust samples were sieved into three particle size fractions (PM125, PM75, and PM32). A bulk and five samples were collected beneath the soil at different depth for depth analysis nearest to the cement plant. Water samples were collected along the Crocodile River before and after the cement plant site. The samples were digested using aqua ragia and extracted using Modified BCR sequential extraction. The samples were analysed using inductive coupled plasma optical emission spectrometry (ICP-OES) for concentration of platinum group metals and x-ray fluorescence for elementary analysis (XRF). Analysis of samples included characterisation of the dust samples using x-ray diffraction (XRD). The vi concentrations were also compared to that of the control study (blank) area to find out if the metals were discharged from the cement factories of interest. In paper IV, street dust samples were collected randomly on the paved surfaces, on the streets and accessible residential and roadsides on locations close to the cement plant in Pretoria. Some samples were collected along the road leading to the gate of the factory and also on the road near the cement plant. The samples were collected into sampling bags using a brush and pan. After sampling dust samples were sieved into three particle size fractions (PM125, PM75 and PM32). A bulk and five samples were collected beneath the soil at different depth for depth analysis nearest to the cement plant. Water samples were collected along the Apies River before and after the cement plant. All samples were kept in a cooler box with ice bags to keep them in good condition. The samples were digested using aqua ragia and extracted using Modified BCR sequential extraction. Results were used to establish spatial distribution of the heavy metals around the urban streets. The samples were analysed using ICP-OES for concentration of heavy metals and XRF. Analysis of samples included characterisation of the dust samples using XRD. The concentrations were also compared to that of the control study (blank) area to find out if the metals were discharged from the cement factories of interest. In paper V, seven different vegetables (spinach/Spinacia oleracea, Chinese cabbage/Brassica rapa, onion/Allium cepa, beetroot/Beta vulgaris, sweet potatoes/Ipomoea batatas, tomatoes/ Lycopersicon esculentum and cabbage/Brassica pekinensis), fruits (bananas/Musa acuminate) and their soils taken after uprooting them were sampled in farming area close to Thohoyandou town and the cement factory. The concentrations of cadmium, nickel and manganese were measured using the graphite atomic absorption spectrometry (GFAAS). Cadmium, nickel and manganese levels were found above permissible limits proposed by Food agricultural organisation (FAO) and WHO in edible parts of vegetables, fruits and soils and hence, may pose a health risk to consumers. Similarly the results from XRF also showed high concentration of the heavy metals in soil analysed. The aim of this project is to determine the levels of toxic heavy metals carried with dust emanating from cement factories. This assessment is meant to identify and highlight the levels of heavy metals in areas that are close to cement factories. The study will develop a database of heavy metals in affected areas and the pollution impact to the affected environments. / NRF

M.Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / In the present study, the removal of Ca2+ and Mg2+ from cooling tower water using Amberlite IR120 and Amberjet 1200 was studied by the application of one factor at a time method (OFAT) and response surface modelling (RSM). The effect of operational parameters such as contact time (min), pH, dosage (mL), concentration (mg/L) and temperature (K) were investigated using central composite design. The regeneration of the Amberlite IR120 and Amberjet were also studied. The purpose of the study was to apply OFAT and RSM to investigate and optimize the ion exchange operating parameters. Furthermore, the second-order empirical model that was developed, using the analysis of variance (ANOVA), presented a sufficient correlation to the ion exchange experimental data. The optimal ion exchange operating conditions for Amberlite IR120 and Amberjet 1200 were found to be: contact time was 120 min, dosage of 150mL, initial pH level of 2, concentration of 400mg/L and temperature of 343K. Regeneration of Amberlite IR120 and Amberjet 1200 using 0.5 M NaCl stripping solution initially showed an increase in % Ca2+ and Mg2+ removal, then a decrease in subsequent cycles. The correlation coefficients (R2) of Langmuir, Freudlich and Tempkin isotherms were found to range from 0.92 to 1 and this suggest that experimental data best described the models. However correlation coefficients (R2) for Dubinin–Radushkevich (D-R) model were found to range between 0.5 to 0.8 and this means that experimental data does not fit the model. Thermodynamic functions such as entropy (Δ𝑆𝑜), enthalpy (Δ𝐻𝑜) and change of free energy (Δ𝐺𝑜) were obtained from the gradient and intercepts of straight line graphs. The positive values of ΔG° were found meaning that the adsorption is not spontaneous and positive values of ΔH° were found meaning the endothermic type of adsorption which indicate the chances of physical adsorption.The correlation coefficient (R2) values of pseudo-first-order, pseudo-second-order and intraparticle models were found to range from 0.89 to 1 on both metals as shown in table 4.4. This observation clearly indicates that pseudo-first-order, pseudo-second-order and intraparticle diffusion models best describe the experimental data in the removal Ca2+ and Mg2+ from cooling tower water.

Sewage sludge is the product from wastewater treatment that mostly is considered as a waste material. However, it contains several nutrients, especially phosphorus, potassium and nitrogen which are excellent fertilizers. The downside is the harmful content it also carries with pathogens, heavy metals and a variety of organic pollutants that in many cases have unknown effects on the ecosystem. A possible solution to this problem could be to pyrolyse the sewage sludge and by that decrease the levels of heavy metals and also render both pathogens and organic pollutants harmless. In this thesis project pyrolysis of dried sewage sludge has been evaluated at temperatures 650 750, 850 and 950 °C with addition of chlorine in the form of PVC and straw. An energy balance for pyrolysis and drying of dewatered sewage sludge has also been suggested. The results of the pyrolysis evaluation indicate that cadmium concentration can be reduced significantly with increasing temperature in the product char. But also other heavy metals like lead and zinc are affected at the higher temperatures evaluated. Mercury is completely removed from the char residue. The more latent volatile metals copper, chromium and nickel cannot be reduced to lower concentrations at these temperatures. They are instead enriched under these conditions. Chlorine addition to the sludge enhances the evaporation of all heavy metals but copper, nickel and chromium. The energy balance over the system indicates that the drying process requires more energy than is released from the sludge into the pyrolysis gases. The energy carried by the pyrolysis gases is however larger than what is required to drive the pyrolysis process.

<p>Storm water is defined as runoff from precipitation such as rain or snow. It is collected in sewage disposal systems and since it mainly originates from urban areas it can contain high levels of heavy metals, nutrients and oil etc. Polluted storm water is currently treated by different methods such as wet ponds, constructed wetlands and filter strips. This study investigates these methods, which in earlier studies have shown to give varying results regarding their treatment efficiency.</p><p>This thesis has been written on commission of SWECO VIAK and was aimed at studying those parameters that may affect the treatment efficiency of nutrients and heavy metals in storm water treatment facilities (STF:s). Through literature studies the dominating treatment processes in ponds and wetlands were examined. The flow pattern was then simulated in four different storm water ponds, of varying shape and size, by using a physically based computer model. The residence time distribution for each pond could then be calculated as well as the hydraulic efficiency, which is a measure on how well the inflowing water is spread throughout a pond. Finally a multiple regression analysis was performed. This analysis examined how the reduction of lead, copper, zinc and cadmium depends on the following factors: the specific pond area, the variance of the residence time distribution, the hydraulic efficiency and the concentration of incoming metals and suspended solids. The specific pond area is a factor which is defined as the pond area divided by the reduced run off area.</p><p>The results from the multiple regression analysis indicate that an increasing content of inflowing suspended solids leads to a better treatment efficiency regarding lead and copper. The specific area showed to have some effect on the treatment efficiency, but this effect was less than that of the content of inflowing suspended solids. The reduction of cadmium depended mainly on the specific area and the incoming concentration of cadmium. An increasing reduction of zinc could to some extent be explained by an increasing specific area.</p><p>The results from this analysis and earlier studies are emphasizing the fact that adsorption to particles and sediment is one of the main processes for a good separation of heavy metals from storm water. Longer measurements series from additional treatment facilities are needed to build a statistical model which, in the future, can be used to predict the treatment efficiency of storm water ponds.</p> / <p>Dagvatten är regn- och smältvatten som samlas upp i avloppssystem. Då detta vatten huvudsakligen härstammar från urban bebyggelse så kan det innehålla höga halter tungmetaller, närsalter och olja med mera. Idag behandlas förorenat dagvatten bland annat genom nyttjande av dammar, våtmarker och översilningsytor. Dessa behandlingsalternativ har dock visat sig ge varierande resultat med avseende på dess reningseffektivitet.</p><p>Detta arbete har utförts på uppdrag av konsultföretaget SWECO VIAK och syftade till att studera vilka parametrar som påverkar reningseffekten av närsalter och tungmetaller i dagvattendammar. Genom litteraturstudier undersöktes de dominerande reningsprocesserna i dammar och våtmarker. Därefter modellerades strömningen i 4 dammar med varierande form och storlek. Vid detta arbete erhölls en fördelning av uppehållstiden hos vattnet för respektive damm samt ett värde på den hydrauliska effektiviteten, vilken är ett mått på hur väl det inströmmande vattnet sprids ut i dammen. Slutligen utfördes en multipel regressionsanalys.</p><p>Vid denna analys undersöktes hur reningen av bly, koppar, zink och kadmium beror av den specifika dammarean, variansen hos vattnets uppehållstidsfördelning, den hydrauliska effektiviteten samt inkommande metall- och TSS-koncentration (suspenderat material). Den specifika dammarean är en faktor vilken defineras som kvoten mellan dammens area och dess reducerade avrinningsområde.</p><p>Resultaten från den multipla regressionen tyder på att en ökad inkommande halt av suspenderat material till dammen har störst betydelse för en förbättrad avskiljning av bly och koppar. Även den specifika arean och metallkoncentrationen i inflödet visade sig ha en viss, men något mindre, betydelse. Reduktionen av kadmium berodde däremot till störst del av den specifika arean och inkommande kadmiumkoncentration. En ökad reduktion av zink förklarades till viss del av en ökad specifik area. Resultatet att halten av suspenderat material i hög grad avgör reningen samt tidigare studier understryker det faktum att adsorption till partiklar och sediment verkar vara en av de viktigaste processerna för en god avskiljning av tungmetaller. Längre mätserier från fler dagvattendammar krävs dock för att i framtiden ta fram en statistisk modell vilken skulle kunna användas till att prediktera reningseffekten.</p>

This master thesis was performed in order to investigate arsenic stabilization in step-wise amended soil. Object of the work - soil which taken from the former wood impregnation industrial site in Forsmo, Sweden. It is contaminated with chromate-zinc-arsenate (CZA). Method of the work - three different amendments were used: zerovalent iron (Fe), fly-ash (FA) and peat (P). The test was performed in three weeks. During the first week, four mixtures (with each single additive and with all together) and blank soil was observed. During the second and third weeks test was performed step-wise adding amendments to soil+Fe mixture. Moisture was kept constant all the time. After each week extractions were made and later investigated by doing electrical conductivity, redox potential and pH tests. For elemental composition ICP-OES analysis was performed. The results of the work - the best result to stabilize arsenic were achieved by adding single iron. Stabilisation using iron, fly-ashes and peat elevated As leaching compared to non-amended soil. Step-wise amendment did not have a significant difference from single amelioration neither to arsenic, nor to other heavy metals investigated. / Darbo tikslas - įvertinti pakopinės stabilizacijos poveikį arseno bei kitų sunkiųjų metalų (SM) judrumui užterštame dirvožemyje. Darbo objektas - chromuotu cinko arsenatu užterštas dirvožemis, paimtas iš buvusios medienos apdirbimo aikštelės Forsmo vietovėje, Švedijoje. Darbo metodika - tyrimui buvo naudoti trejopi priedai: geležis (0), lakieji pelenai ir durpės. Tyrimas atliktas per tris savaites. Pirmosios savaitės metu buvo stebimi keturi dirvožemio ir jo priedų mišiniai bei kontrolinis dirvožemio mėginys. Vėliau dirvožemio ir geležies mišinys buvo pakopiniu būdu papildomas lakiaisiais pelenaisi ir durpėmis. Iš visų mišinių padarytos ištraukos ir jose matuojamas elektrinis laidumas, oksidacijos-redukcijos potencialas, pH; atlikta elementinė analizė. Darbo rezultatai - efektyviausiai arseną stabilizuoja geležis. Stabilizacija, naudojant lakiuosius pelenus ir durpes, padidino arseno išsiplovimą iš dirvožemio, lyginant su kontroliniu dirvožemio mėginiu. Pakopinė stabilizacija nebuvo efektyvesnė už vienkartinę stabilizaciją nei arseno, nei kitų tirtų sunkiųjų metalų atžvilgiu.

Magistrantūros studijų baigiamajame darbe pateikiami aliejinių moliūgų sausųjų medžiagų, sunkiųjų metalų: kadmio, švino, chromo, vario, cinko ir nikelio duomenys, gauti juos auginant augalinių ir komunalinių atliekų kompostuose. Darbo objektas – aliejiniai moliūgai (Cucurbita pepo L. var. Styriaca) ‘Olivia’, auginti augalinių ir komunalinių atliekų kompostuose. Darbo metodai. Standartiniais metodais tirta sausųjų medžiagų kiekis aliejinio moliūgo minkštime, žievėje ir sėklose. Sunkiųjų metalų kiekis nustatytas induktyvinės plazmos masės spektrometrijos metodu (LST EN 15621:2012). Analizės atliktos LAMMC Agrocheminių tyrimų laboratorijoje. Darbo rezultatai. Naudoti kompostai, turėjo įtakos sunkiųjų metalų kaupimuisi skirtingose aliejinių moliūgų dalyse. Žievėje ir minkštime daugiausia sausųjų medžiagų sukaupė moliūgai, auginti kontroliniame variante, o sėklose – augalinių ir komunalinių atliekų kompostuose. Švino ir kadmio kiekis ES rekomenduojamos DLK daržovėse neviršijo. Kitų sunkiųjų metalų (Cu, Cr, Ni ir Zn) koncentracijos daržovėse nėra reglamentuotos. Gauti rezultatai parodė, kad jų kiekis, skirtingose moliūgų vaisių dalyse, buvo panašūs. / The master work presents the results of oil pumpkin fruit dry matter, heavu metals: cadmium, lead, chromium, copper, zinc and nickel data derived from the cultivation of plant and municipal waste compost. Object of the work: the oil pumpkin (Cucurbita pepo L. var. Styriaca) cultivar 'Olivia'. Method of the work ̶ standard methods were applied to investigate the dry matter content in the flesh, peel and seeds of oil pumpkin. The amount of heavy metals was determined by using inductive plasma mass spectrometry (BS EN 15621:2012). The analyses were carried out in the Agrochemical Laboratory of the Lithuanian Research Centre for Agriculture and Forestry. The results of work. The usage of compost in different parts of oil pumpkin had impact on the heavy metal accumulation. The pumpkins of the control variant accumulated the highest amount of peel and flesh solids whereas the pumpkins grown in the municipal waste compost seeds contained the highest amount of seed solids. Lead and cadmium in the EU did not exceed the recommended maximum allowable concentration for vegetable. The concentration of other heavy metals (Cu, Cr, Ni and Zn) in vegetables is not regulated. The results showed that the quantity in different parts of the pumpkin fruit was similar.

Following the decline of the UK metal mining industry by the 1920s, over 3,000 abandoned metal mines exist in England and Wales. Contaminated drainage from this historical industry causes approximately 20% of all water quality failures in England and Wales. In this thesis, a holistic geographical approach, incorporating aspects of hydrology, hydrogeochemistry and freshwater ecology, is employed to investigate the hydrological, sedimentological and ecological impacts of the abandoned Dylife lead/zinc mine on the Afon Twymyn (central Wales). Examination of river sediment quality highlights the need for measurements of the quality of this component of the river ecosystem and, in particular, measurement of bioavailable as opposed to total metals. The majority of heavy metals in bed sediments of the Afon Twymyn exist in highly mobile geochemical phases, potentially posing serious threats to ecological integrity. Significant metal flushing occurred during flood events at Dylife mine and a distinct seasonal pattern was observed with greater levels of flushing occurring during flood events in the summer months. It is suggested that investigations of contaminant/ecosystem relations and potential remediation strategies should include high-resolution temporal sampling of river water chemistry under conditions of flood flow. Paradoxically, a range of biological indices failed to identify significant negative impacts of metal mine contaminants on macroinvertebrate communities, suggesting there is little contamination of the river ecosystem. However, Canonical Correspondence Analysis did identify significant differences in community structure between polluted and unpolluted river stretches, suggesting that standard unimetric biological indices might only be successful in identifying impacts at the most severely polluted mine sites. It is suggested that the ecological approach of the European Union Water Framework Directive to the assessment of river ecosystem status may not yield an accurate representation of contamination in rivers such as the Afon Twymyn where contamination by mining is moderate, circum-neutral and the mining operation is long abandoned.

Ascaris suum were exposed to a number of stressors, including heavy metals and both high (40°C) and low (18°C) temperatures. The 70kD and 90kD heat shock proteins (HSPs) in the different A. suum tissues were analyzed by Western blot and quantitated by Macintosh Image Program.