The arctic is expected to be one of the regions most affected by ongoing climate change, with relative changes in air temperatures significantly higher than the global mean. Lakes are recognized for their potential role in the global climate system and as ecosystems of importance for local societies. As such, there is a scientific interest regarding how arctic lakes and their geochemistry will respond to climatic changes. Lakes around Kangerlussuaq (66.99 N, 51.07 W), south-west Greenland, are known for their unique geochemical composition, including oligosaline lakes, of which some are enriched in colourless dissolved organic carbon (DOC). The origin of this DOC and the importance of local catchment properties for the general water chemistry is currently being debated. This thesis aimed at: i) exploring the extent and effect of catchment morphology on lake-water chemistry in the Kangerlussuaq area; ii) determine the predominant origin of DOC, aquatic or terrestrial. I used a remote-sensing approach based on satellite imagery and digital elevation model (DEM) in deciding landscape influence on water chemistry (pH, alkalinity, conductivity, base cations, sulphate, nitrogen and absorbance). To trace the origin of the organic sources behind DOC lake water and sediments, I used a hydrogen isotope tracing method. The remote sensing approach revealed that morphological characteristics serving as proxies for lake water residence time and hydrologic connectivity (e.g. lake altitude difference and absence of outlets) explained up to 77% of the variations in lake water chemistry. The hydrogen isotopic signature of the DOC indicated a predominantly autochthonous origin, i.e. 59 to 78% was estimated to originate from algae. I conclude that lake water chemistry of the lakes in the study area is primarily controlled by the precipitation : evaporation balance, enhanced by static catchment characteristics regulating water age. Thus, the examined lake water chemical properties are likely to remain across future climatic scenarios, providing the current precipitation : evaporation balance prevails.

Impacts of long-term acid deposition on soil and water chemistry are of particular concern in the Great Smoky Mountains National Park (GRSM), receiving some of the highest acid deposition rates in the eastern United States and limited by inadequate acid buffering capacity. In the GRSM, the Noland Divide watershed (NDW) has been monitored since 1991 for water chemistries of precipitation, throughfall, soil, and stream. The impacts of long-term acidic deposition on stream water quality in the NDW were investigated through: 1) development of an ion input-output budget; 2) analysis of trends and seasonal patterns for major ions; 3) comparison of net export rates between baseflow and stormflow periods; and 4) characterization of soil chemistry and transport properties for various potential acid deposition scenarios. Between 1991 and 2006, throughfall deposition remained unchanged and consisted of 1,735 eq ha-1 yr-1 of SO42-, 863 eq ha-1 yr-1 of NO3-, and 284 eq ha-1 yr-1 of NH4+. Net retention of sulfate was estimated at 61% being controlled by soil adsorption, and inorganic nitrogen was retained at 32% presumably due to plant uptake. Nitrogen retention increased by 44.30 eq ha-1 yr-1 over the study period. Besides deposition, soil acidity was increased by nitrification and precipitation-driven desorption of previously accumulated sulfate. To neutralize soil acidity, Ca2+, Mg2+ and Na+ were depleted from NDW by 77, 46 and 66 eq ha-1 yr-1, respectively. Due to the continuous addition of acidity, base saturation in soil was reduced to 4% at present. Mobilization of aluminum and other metals (Mn and Zn) may be enhanced by these geochemical processes, potentially causing toxic conditions to fish and other biota in the GRSM streams. Impacts of acidic deposition on streams were confirmed by measured stream pH below 6 and acid neutralizing capacity below 0.01 meq L-1. During stormflows pH and ANC depressions occurred primarily due to increases in sulfate transport, leading to episodic acidification events. This study provides new information on hydrological and biogeochemical processes that regulate stream acidification events in the southern Appalachian region, supporting improved management strategies for GRSM streams.

La memòria consisteix en l'estudi de la complexació del Fe3+ i de l'AI3+ per fosfats i lligands orgànics carboxílics (PBTC) en un medi iònic 0.5 M en NaNO3 i una posterior aplicació dels resultats obtinguda a la caracterització química de l'aigua per ús industrial i agrícola. La tècnica analítica emprada per la obtenció de les dades experimentals es fonamenta en la determinació de l'acidesa mitjançant valoracions potenciomètriques. Aquestes dades, transformades en funcions del tipus Z són introduïdes en els programes de càlcul LEGATROP i HYPERQUAD amb l'objectiu de modelar el comportament químic de cada sistema estudiat.

The aim of this study was to investigate whether the water chemistry in lake Lillsjön have changed significantly due to human impact of surrounding areas. Lake Lillsjön is located outside the central parts of Östersund. It is an important recrational area, and has great natural values, among other things it is habitat for several species of Chara stoneworts. Chara requires clear calcareous water, high pH, relatively low levels of nitrate-nitrogen and low phosphorus concentrations. Lake Lillsjöns is recepient for surface water from a nearby commercial and industrial area, as well as melt water from an adjecent snow dump. Compared to ten other Chara-lakes in the region, lake Lillsjön shows higher concentration of total phosphorus and higher water colour. The study concludes that the surface water from surrounding areas, as well as melting water from the snow dump, are the main sources of the higher concentration of total phosphorus in lake Lillsjön. While the colour of the incoming water only shows a weak difference compared to the water colour of the reference lakes, the source of the higher water colour cannot be established. The water of lake Lillsjön can not be consider a suitable habitat for Chara.

Ab initio molecular orbital theory has been successful in predicting the stabilities of many weak complexes; typical of these are the complexes formed between water and various small molecules. To account for the correlation effect, Moller-Plesset perturbation theory truncated at the second order level was employed. In order to account for the hydrogen bonding, the 6-3lG** basis set was used. The geometry optimisations of the complexes were carried out using the Gaussian-92 suite of programs installed on a Hewlett-Packard 720 computer operating under UNIX. The interaction energies of the complexes were subjected to further analysis by applying the Morokuma decomposition scheme. The electrostatic interaction component accounts for over 40% of the total stabilisation energy in all the typical hydrogen bonded complexes. Gas phase enthalpies were computed and compared with the experimental values of similar systems. For the systems studied here, the prediction is that all complexes are stable at 25° C. A second program, Vibra, was used for carrying out a normal coordinate analysis. A third computer program for the graphical representation of molecular and crystallographic models, Schakal-92, was employed to illustrate the predicted equilibrium geometries and the fundamental vibrational modes. The predicted geometries, interaction energies, charge redistributions, vibrational wave numbers, infrared intensities and force constants are listed and compared with those in the literature, where applicable. Correlations between the various predicted properties show some interesting chemistry. / Thesis (Ph.D.)-University of Natal, Durban, 1996.

The relationship between fen vegetation and water and soil chemistry gradients in an alkaline slope fen was studied during the growing season of 2005. Owned by Irving Materials Inc. (IMI), the fen is a two hectare property in north-central Henry County, Indiana. The objectives of the study were (1) to conduct a floral inventory of the site and determine the floristic quality index for the site; (2) to visually characterize and stratify the site into areas of similar vegetation or community types; (3) to characterize relationships, if any, existing between vegetation and chemical and hydrological gradients; and (4) to quantify spatial and temporal patterns of ground water alkalinity throughout the fen. The floral inventory revealed 287 species, representing 180 genera in 79 families. Of the documented flora, 246 are native, 41 are adventives, and 20 represent Henry County records. The Floristic Quality Index and the mean Coefficient of Conservatism suggest that the site is of nature preserve quality and contains noteworthy remnants of the region’s natural heritage. They also suggest that the adventives are having a minimal negative impact on the native flora. For quantitative vegetation analysis, fixed transects were monitored three times during the growing season (spring, summer, fall). Basic subsurface water chemistry and levels were monitored bi-weekly and 30 soil and 30 surface water samples (10 each to coordinate with the vegetation survey) were analyzed for over 35 physical parameters. In all cases, the parameters fell within the ranges of typical Midwestern fens, but most noticeably for calcium carbonate. Applying the Floristic Quality Assessment to the vegetation occurring along fixed transects, 26 species were identified with an importance value greater than one. Nonmetric, multidimensional scaling analysis of fen species dominance delineate spatial and temporal patterns in vegetation. Joint plot vectors indicate the strength and direction of correlations between soil and water chemistry variables. Nine physical parameters were useful to separate vegetation into groups. The relationship between the plants and these nine parameters is described and discussed. / Department of Biology

The aim of this study was to identify the algal genera found in the different freshwater bodies on Marion Island, to relate the presence or absence of the genera to the chemistry of the water bodies and to group the genera according to their limno-chemical preferences. The Island's freshwater algal genera were also compared with genera found on other Southern Ocean islands. The major factors influencing the chemical composition of the freshwaters of the island are the surrounding ocean and the manuring of seals and seabirds. The Western and Southern lakelets and wallows had higher mean conductivity values than most of the other water bodies. Eastern Inland lakelets, crater lakes and glacial lakes had low ion and nutrient concentrations, since they are mainly situated inland, away from bird or seal colonies. The chemical composition of wallows was influenced by manuring of seals and seabirds. The freshwaters are acidic and lakelets tend to be more acidic than glacial lakes. The lentic waters were more acidic than the stream. In total, 106 genera, mainly belonging to Chlorophyta (60 genera; 56% of total) and Cyanophyta (29 genera; 27% of total), were found in the freshwaters on the island. Other algal divisions found were Chrysophyta (7 genera), Euglenophyta (4 genera), Pyrrophyta (2 genera) and Xanthophyta (4 genera). Mean number of genera per sample ranged from 8 (in wallows) to 16 (in Eastern Inland lakelets). Filamentous algae were present in all the samples. Abundant green algae were Cosmarium, Klebsormidium, Mougeotia and Oedogonium. The most common cyanobacteria were Lyngbya and Chroococcus. The filamentous yellow-green alga, Tribonema, was also common. There were distinct differences in the algal composition between the southern, western and northern lakelets and the lakelets on the eastern side of the island. Sixty percent of the algal genera were present in waters with low conductivity values. Trichodesmium, Sphaerocystis and Tolypothrix occurred in freshwater bodies with higher conductivity values. Variance analysis showed that 87 of the 106 genera were less likely to occur in nitrogen and phosphate containing waters. Chlamydomonas, Prasiola, Spirogyra Trachelomonas, Tribonema, Ulothrix and Xanthidium were among the genera commonly found in nitrogen and phosphate containing waters. Diversity (number of genera per sample) was negatively correlated with conductivity, PO4-P, NH4-N and NO3-N. Diversity declined significantly with increasing salinity and eutrophication. Genera likely to occur in acidic waters include Binuclearia, Chlamydomonas, Chroococcus, Cosmarium, Klebsormidium, Microspora, Oedogonium, Oocystis, Prasiola, Scenedesmus, Staurastrum, Stigeoclonium, Tetrastrum, Ulothrix, Lyngbya, Synura and Tribonema. Marion Island’s algal flora shows a high affinity with that of Îles Kerguelen and Crozet, both located in the same biogeographical province (South Indian Ocean Province) of the sub-Antarctic than Marion Island, and a lesser affinity with islands in other sub-Antarctic provinces. Algal genera were grouped according to their limno-chemistry preferences. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2012.

The aim of this study was to identify the algal genera found in the different freshwater bodies on Marion Island, to relate the presence or absence of the genera to the chemistry of the water bodies and to group the genera according to their limno-chemical preferences. The Island's freshwater algal genera were also compared with genera found on other Southern Ocean islands. The major factors influencing the chemical composition of the freshwaters of the island are the surrounding ocean and the manuring of seals and seabirds. The Western and Southern lakelets and wallows had higher mean conductivity values than most of the other water bodies. Eastern Inland lakelets, crater lakes and glacial lakes had low ion and nutrient concentrations, since they are mainly situated inland, away from bird or seal colonies. The chemical composition of wallows was influenced by manuring of seals and seabirds. The freshwaters are acidic and lakelets tend to be more acidic than glacial lakes. The lentic waters were more acidic than the stream. In total, 106 genera, mainly belonging to Chlorophyta (60 genera; 56% of total) and Cyanophyta (29 genera; 27% of total), were found in the freshwaters on the island. Other algal divisions found were Chrysophyta (7 genera), Euglenophyta (4 genera), Pyrrophyta (2 genera) and Xanthophyta (4 genera). Mean number of genera per sample ranged from 8 (in wallows) to 16 (in Eastern Inland lakelets). Filamentous algae were present in all the samples. Abundant green algae were Cosmarium, Klebsormidium, Mougeotia and Oedogonium. The most common cyanobacteria were Lyngbya and Chroococcus. The filamentous yellow-green alga, Tribonema, was also common. There were distinct differences in the algal composition between the southern, western and northern lakelets and the lakelets on the eastern side of the island. Sixty percent of the algal genera were present in waters with low conductivity values. Trichodesmium, Sphaerocystis and Tolypothrix occurred in freshwater bodies with higher conductivity values. Variance analysis showed that 87 of the 106 genera were less likely to occur in nitrogen and phosphate containing waters. Chlamydomonas, Prasiola, Spirogyra Trachelomonas, Tribonema, Ulothrix and Xanthidium were among the genera commonly found in nitrogen and phosphate containing waters. Diversity (number of genera per sample) was negatively correlated with conductivity, PO4-P, NH4-N and NO3-N. Diversity declined significantly with increasing salinity and eutrophication. Genera likely to occur in acidic waters include Binuclearia, Chlamydomonas, Chroococcus, Cosmarium, Klebsormidium, Microspora, Oedogonium, Oocystis, Prasiola, Scenedesmus, Staurastrum, Stigeoclonium, Tetrastrum, Ulothrix, Lyngbya, Synura and Tribonema. Marion Island’s algal flora shows a high affinity with that of Îles Kerguelen and Crozet, both located in the same biogeographical province (South Indian Ocean Province) of the sub-Antarctic than Marion Island, and a lesser affinity with islands in other sub-Antarctic provinces. Algal genera were grouped according to their limno-chemistry preferences. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2012.

Up to 59 small tundra lakes were sampled in the uplands east of the Mackenzie Delta, NWT, Canada, in order to assess the impact of permafrost thaw on pelagic nutrient concentrations and biota. Permafrost thaw did not affect the concentrations of nitrogen, phosphorus or organic carbon in the water column of the study lakes. Instead, nitrogen and organic carbon concentrations were positively related to relative catchment size, and phosphorus concentrations were negatively related to maximum lake depth. Lakes affected by permafrost thaw did have lower water colour. In lakes not affected by thaw, where plankton production could have been light limited due to high water colour, the TP-chlorophyll a relationship was weaker than in lakes affected by thaw, where light limitation was probably weaker. A model selection analysis for chlorophyll a concentration indicated water colour as the best predictor variable in unaffected lakes, but nitrogen and phosphorus as the best predictors in thaw-affected lakes. This result, in particular, suggested a significant shift in the processes governing productivity in thaw-affected lakes. In a smaller subset of lakes, chlorophyll a concentrations were lower in lakes affected by actively degrading permafrost than in lakes affected by stabilized thaw scars or in unaffected lakes. In contrast, zooplankton abundance was lowest in lakes with stabilized thaw scars. Bacterioplankton abundance was not different across the gradient of permafrost thaw. The differences in phytoplankton and zooplankton abundance between active and stable thaw scar lakes did not display a gradient of response that mirrored the degree of permafrost thaw activity. Because sampling did not include higher trophic levels, including macroinvertebrates and fish, it was difficult to determine how these biomass patterns arose. However, detectable differences existed in the morphometry of the lakes that might have affected habitat conditions for several species. Deep, near-shore lake-bottom pits occurred in lakes affected by permafrost thaw, while unaffected lakes were generally deepest at their centre. The pits increased the effective depth of the thaw-affected lakes, and allowed for thermal stratification where it might not have otherwise occurred. Future research should explore the habitat-related impacts of permafrost thaw on adjacent and higher trophic levels in order to better understand the fundamental shifts in trophic structures that appear in lakes affected by permafrost thaw.

The control exerted by underlying geological formations, topography and time in governing physico-chemical variability of shallow waterbodies is documented for Schefferville. Nouveau-Quebec and Igloolik Island, N.W.T. / The highly resistant siliceous bedrock of the Labrador Trough in the Schefferville area produced very dilute surface waters with more or less equivalent concentrations of major cations. Dolomitic limestone and dolostone on Igloolik Island resulted in highly mineralized surface waters dominated by Ca$ sp{2+}$, Mg$ sp{2+}$ and HCO$ sb3 sp-$, with contributions by Na$ sp+$ and Cl$ sp-$ increasing with coastal proximity. / Sediments from the Schefferville area possessed low concentrations of Ca and Mg indicative of noncarbonate bearing substrate, contrasting to the calcareous nature of the sediments from Igloolik Island. Sediment concentrations of Al, Fe and Mn from the Schefferville area were elevated compared to sediment concentrations on Igloolik Island. The disparity in trace metal concentrations in sediments between the two study areas is attributed to the enrichment of these elements in the Labrador Trough, as well as the general trace metal dilution encountered in limestone and dolostone. / Principal Component Analysis with Varimax Rotation for surface waters of Igloolik Island revealed four factors accounting for 98% of the total variance confirming controls exerted by sea-salt spray and lithological substrate in moderating surface water chemistry. Differential rates of weathering at certain sites on Igloolik Island are suggested by dissimilar factor loading scores.