Ce projet de thèse vise à étudier les processus géochimiques de l'aluminium dans les sols acides à sulfates. Les résultats obtenus avec le dispositif de dialyse de Donnan montrent que l'aluminium dans la solution du sol est presque exclusivement (> 98%) présent sous forme de complexes de charge négative, vraisemblablement des organo-complexes d'aluminium. Les concentrations d'aluminium isotopiquement échangeables (valeurs-E) et les concentrations obtenues par extractions chimiques révèlent qu'une solution de 1 M KCl sous-estime systématiquement les valeurs E. Une méthode d'extraction séquentielle a révélé qu'une quantité importante de minéraux primaires (initialement présents dans les sols) a déjà été dissoute, comme en témoignent les concentrations élevées d'aluminium présentes en tant que minéraux secondaires d'aluminium. Ces études permettent de mieux comprendre la géochimie de l'aluminium dans les sols CLASS et de pouvoir intégrer ces connaissances dans la gestion des sols. / The aim of this thesis was to further understanding on Al geochemistry in coastal lowland acid sulfate soils (CLASS). It was observed that Al was present almost solely (> 98%) as negatively charged complexes in CLASS pore-waters, presumably with natural organic matter. Isotopically exchangeable concentrations (E-values) of Al and extraction solutions used to estimate the exchangeable pool showed that 1 M KCl always underestimated isotopically exchangeable Al concentrations in these soils and that 0.2 M CuCl2 improved agreement between both methodologies but sometimes overestimated corresponding E values. A sequential extraction procedure showed that substantial amounts of Al have already been dissolved from primary aluminosilicates initially present in the soils and remain in the soils mostly as reactive secondary Al minerals. The outcomes of this thesis significantly further our understanding of Al geochemistry in CLASS environments and how this knowledge can be incorporated into land management practices.

Many brackish water aquaculture ventures in Australia and overseas have established ponds in coastal regions with acid sulfate soils (ASS). Acid sulphate soils are known to leach relatively high concentrations of metals, acid (metal and H+ ion) and sulfur, however very little is known about how these leached elements affect the water quality of aquaculture ponds. The main objective of this thesis was to describe the hydrochemical processes controlling the water chemistry in the water column and sediment pore water in the studied aquaculture ponds over time and space. Water samples providing the spatio-temporal data were collected from the ponds with the use of adapted sampling methods commonly used in the groundwater environment. A transect of five nested piesometers was installed in two prawn ponds at Pimpama, south east Queensland, Australia. Each piesometer nest contained a multilevel with eight outtakes, a mini ?? horizontal, and a slotted piesometer. Water samples were collected from each nested piesometer on a bi-monthly basis over the prawn-growing season. The unstable elements and water quality variables (pH, Eh, DO, EC, water temperature) were measured in the field. Stable elements were analysed in the laboratory using ICP-OES and ICP-MS. Soil samples were collected at the end of the season for elemental analysis. A number of key sediment/water interactions and processes such as precipitation/dissolution reactions, oxidation-reduction reactions, photosynthesis, adsorption and seawater buffering were identified as important controls on pond water conditions. This is the first study to provide detailed hydrochemcial analysis of the pond water over time and space and aided in identifying that even shallow water bodies can be chemically heterogeneous. Analysis of the water and sediment highlighted the selection of metals that can be associated with ASS and that are mobilised from pond sediments under certain chemical conditions. In Pond 7 Al, As, Ni and Zn concentrations were generally higher at the beginning of the grow-out season. Variability of the metal concentration was observed between the water column (0 ?? 1500 mm) and the pore-water (0 - -1000 mm). The highest concentration of Al (1044 ??g/L) and Zn (104 ??g/L) were sampled in the water column (approximately 400 mm from the surface of the pond). The highest concentration of As (130 ??g/L) and Ni (73 ??g/L) were sampled in the pore water sediment (associated with ASS). Elevated Mn and Fe2+ concentrations were also associated with the sediment pore water. The highest concentrations of Mn and Fe2+ were 4717 ??g/L and 5100 ??g/L respectively. In Pond 10, Ni concentrations (167 ??g/L) were the highest at the beginning of the grow-out season. However, As (97 ??g/L), Al (234 ??g/L) and Zn (308 ??g/L) were most concentrated during the middle of the cycle. The highest mean concentrations of these elements are As (63 ??g/L), Al (91 ??g/L) and Zn (69 ??g/L) which are each associated with the sediment-water interface. These metals are integral in degrading the pond water quality and lead to a loss of beneficial algal blooms, a reduction in pond water pH, poor growth rates and high mortality in shrimp. It is also possible that the dissolved ions and precipitated compounds that are leached from the ASS are discharged into the adjacent coastal estuary of Moreton Bay. With knowledge obtained from this PhD study, effective management and treatment systems can be developed and implemented to minimise the impact of these soils on the pond system and the water discharging into natural coastal ecosystem.

Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains vi, 36 p. : ill. (some col.), col. maps. Includes abstract. Includes bibliographical references (p. 31-36).

In the north of Sweden lots of the soil is naturally contaminated by acid sulfate. When soil gets in contact with oxygen an oxidation process begins which releases elements that may be harmful to the surroundings. When the Botniabanan was built, soil had to be transported from the railroad area to deposit sites. This study was made to investigate the suspicions a landowner had regarding if his estate had been contaminated sulphide soil soil during the building of the Botniabanan. To do that four pits were dug in the area where the soil had been deposited. Then the soil was analyzed to see the content of sulfate, iron, organic matters and water. When the results was compared to other studies it showed that the content of sulfate and organic matters was to low to classify the soil as an acid sulfate soil.

The reaction of sulfate with six podzolic horizons of the Southern Laurentians (Quebec) was investigated using batch reaction techniques. It was demonstrated that sulfate sorption increased with decreasing solution pH to a maximum sorption capacity at around pH 4.0; below this pH retention decreased. This drop in sorption capacity was related to the partial dissolution of Al surface coatings. Indeed, the amount of native sulfate and the maximum sorption during the experiment were positively correlated (R$ sp2$ = 0.982, 0.800) with the oxalate extractable Al content of these forested soils. In all six horizons, the increase in sulfate sorption as a function of equilibrium sulfate concentration was best described by the Gunary equation. Kinetic experiments showed the presence of two major stages in both sorption and desorption reactions with an initial quick change (first 6 h) in solution concentration being followed by a second step where the reactions between sulfate and the soil matrix were much slower. The time-dependence of these reactions emphasized the appropriateness of kinetic equation in describing field situations. Moreover, kinetics studies performed under highly acidic conditions demonstrated that the amount of sulfate sorbed decreased with time after an initial sorption step due to the partial dissolution of Al surface materials. Thermodynamic calculations further suggested the subsequent precipitation of jurbanite. It was then concluded that surface dissolution and mineral formation should be considered in the interpretation of results obtained from experiments aimed at determining the effect of pH on sulfate retention.

Many brackish water aquaculture ventures in Australia and overseas have established ponds in coastal regions with acid sulfate soils (ASS). Acid sulphate soils are known to leach relatively high concentrations of metals, acid (metal and H+ ion) and sulfur, however very little is known about how these leached elements affect the water quality of aquaculture ponds. The main objective of this thesis was to describe the hydrochemical processes controlling the water chemistry in the water column and sediment pore water in the studied aquaculture ponds over time and space. Water samples providing the spatio-temporal data were collected from the ponds with the use of adapted sampling methods commonly used in the groundwater environment. A transect of five nested piesometers was installed in two prawn ponds at Pimpama, south east Queensland, Australia. Each piesometer nest contained a multilevel with eight outtakes, a mini ?? horizontal, and a slotted piesometer. Water samples were collected from each nested piesometer on a bi-monthly basis over the prawn-growing season. The unstable elements and water quality variables (pH, Eh, DO, EC, water temperature) were measured in the field. Stable elements were analysed in the laboratory using ICP-OES and ICP-MS. Soil samples were collected at the end of the season for elemental analysis. A number of key sediment/water interactions and processes such as precipitation/dissolution reactions, oxidation-reduction reactions, photosynthesis, adsorption and seawater buffering were identified as important controls on pond water conditions. This is the first study to provide detailed hydrochemcial analysis of the pond water over time and space and aided in identifying that even shallow water bodies can be chemically heterogeneous. Analysis of the water and sediment highlighted the selection of metals that can be associated with ASS and that are mobilised from pond sediments under certain chemical conditions. In Pond 7 Al, As, Ni and Zn concentrations were generally higher at the beginning of the grow-out season. Variability of the metal concentration was observed between the water column (0 ?? 1500 mm) and the pore-water (0 - -1000 mm). The highest concentration of Al (1044 ??g/L) and Zn (104 ??g/L) were sampled in the water column (approximately 400 mm from the surface of the pond). The highest concentration of As (130 ??g/L) and Ni (73 ??g/L) were sampled in the pore water sediment (associated with ASS). Elevated Mn and Fe2+ concentrations were also associated with the sediment pore water. The highest concentrations of Mn and Fe2+ were 4717 ??g/L and 5100 ??g/L respectively. In Pond 10, Ni concentrations (167 ??g/L) were the highest at the beginning of the grow-out season. However, As (97 ??g/L), Al (234 ??g/L) and Zn (308 ??g/L) were most concentrated during the middle of the cycle. The highest mean concentrations of these elements are As (63 ??g/L), Al (91 ??g/L) and Zn (69 ??g/L) which are each associated with the sediment-water interface. These metals are integral in degrading the pond water quality and lead to a loss of beneficial algal blooms, a reduction in pond water pH, poor growth rates and high mortality in shrimp. It is also possible that the dissolved ions and precipitated compounds that are leached from the ASS are discharged into the adjacent coastal estuary of Moreton Bay. With knowledge obtained from this PhD study, effective management and treatment systems can be developed and implemented to minimise the impact of these soils on the pond system and the water discharging into natural coastal ecosystem.

Marine sulfide – bearing sediments that oxidize when in contact with oxygen and leach outelements in high concentrations to small watercourses have been a problem for many years allover the world especially around the Bothnian Bay. The purpose of this study was to furtherinvestigate the sulfur mineralogy present in acid sulfate soils in the area of Luleå, Sweden. Asecondary aim was to see if elements leach out and accumulate in an acid sulfate soil closer tothe recipient. Samples were taken in two profiles (one oxidized and one waterlogged) fromfour sites (sites A-D) and were analyzed for whole rock geochemistry. Two sites were furtherinvestigated for mineralogy in polished samples with an optical microscope, Ramanspectroscopy and SEM-EDS. Each profile consisted of three layers: oxidation zone, transitionzone and reduced zone. The oxidation zone above the groundwater table was light grey withbrown iron hydroxide staining. Parts that lied under the water table were dark grey-black within general strong odor (“rotten eggs”) due to its sulfur content. It was usually straightforwardto distinguish and separate the layers from each other directly in the field, however in somecases pH was needed for confirmation.A general feature of investigated polished samples is the presence of abundant framboidalpyrites that are common in reduced marine sediments. The transition zone was formed in suboxicconditions and this feature is reflected by the mineralogy. Many morphologies of theframboidal pyrite were observed in this layer and signs of both dissolution and formationoccur. In the sample from site C one could observe elemental sulfur in form of large (up to 50μm) euhedral crystals. In the samples with pH<4, no sulfides occur as they have been replacedby jarosite (site B). Site C lacks these sulfur-bearing hydroxides which is thought to be due toa sulfur concentration of <0.2 %. Sulfur shows extensive leaching at most sites but at site B andD1, it accumulates in the transition zone. Elements like cobalt (Co), nickel (Ni) and zinc (Zn)are leached out or are accumulated further down in the profile. Elements that could have beentransported and have accumulated in the waterlogged profiles are Co, Ni, Zn and chromium(Cr) and in some profiles also copper (Cu) and vanadium (V). / Coastal watercourses in Bottenviken: Method development and ecological restoration- A cross-border Swedish-Finnish cooperation project

Acid sulfate (AS) soils are characterized by a large pool of sulfates which may provide significant amounts of acidity and heavy metals – commonly nickel (Ni), Cobolt (Co), Zinc (Zn) and Arsenic (As) - to surrounding surface waters. The occurrence of AS soils is widespread, covering 17 million ha globally, and they are known for threatening freshwaters in Australia, North America as well as in many tropical regions. Mobilization of mercury (Hg) from AS soils is however poorly studied and could potentially be an environmental problem of concern due to its toxicity and capacity of bioaccumulating in food webs. In this study I investigated whether Hg is mobilized from AS soils by conducting chemical analyses on sediment samples from a 1,6 m deep lake core and a transect of surficial sediment samples in an adjacent sea bay. Here, I used zircon (Zr) and zinc (Zn) as proxies for silicate sources and sulfide soil sources, respectively. I found that Zn and Hg concentrations normalized to the organic matter content (LOI) showed a significant correlation in the lake core; hence, Hg in the sediment co-varied with my sulfide proxy and showed no correlation to my silicate proxy, and I then conclude that a considerable fraction of mercury in the studied sediment has a likely origin from AS soils.

The leakages of metals from acid sulfate soils and their potential toxicity to benthic invertebrates were studied in the sediment profiles of Lillkvasjön and Lövselefjärden - a lake and an estuary known to be affected by acid sulfate soils - in Västerbotten, northern Sweden. The concentrations of 25 different elements were analyzed throughout both sediment profiles through X-Ray Fluorescence (XRF) Spectrometer analysis. Organic matter was measured through loss-on-ignition (LOI). By performing correlation analysis and normalizations to LOI on all sediment variables, Cu, Fe, Ni, Pb, S and Zn were found to be leached from acid sulfate soils to both sites, while Mg and Mn were related to leakages from acid sulfate soils in Lövselefjärden. The concentrations of Cu (195 mg kg-1), Ni (55 mg kg-1), Pb (90 mg kg-1) and Zn (398 mg kg-1) in the surface sediment of Lövselefjärden were classified as potentially toxic to benthic invertebrates. In Lillkvasjön, Cu (210 mg kg-1) and Ni (87 mg kg-1) were classified to have an increased risk of negative impacts on benthic invertebrates, while the concentrations of Pb (121 mg kg-1) and Zn (329 mg kg-1) were likely to low to have any negative effects. These results strengthen previous finds of impacts from acid sulfate soils in the two catchment areas and elucidate the importance of further studies on the impact of acid sulfate soils on benthic invertebrates.

The study employed multi-variate methods to generate vulnerability maps for acid sulfate soils (AS) in the Norrbotten county of Sweden. In this study, the relationships between the reclassified datasets and each biogeochemical element was carefully evaluated with ANOVA Kruskal Wallis and PLS analysis. The sta-tistical results of ANOVA Kruskall-Wallis provided us a useful knowledge of the relationships of the preliminary vulnerability ranks in the classified datasets ver-sus the amount of each biogeochemical element. Then, the statistical knowledge and expert knowledge were used to generate the final vulnerability ranks of AS soils in the classified datasets which were the input independent variables in PLS analyses. The results of Kruskal-Wallis one way ANOVA and PLS analyses showed a strong correlation of the higher levels total Cu2+, Ni2+ and S to the higher vulnerability ranks in the classified datasets. Hence, total Cu2+, Ni2+ and S were chosen as the dependent variables for further PLS analyses. In particular, the Variable Importance in the Projection (VIP) value of each classified dataset was standardized to generate its weight. Vulnerability map of AS soil was a result of a lineal combination of the standardized values in the classified dataset and its weight. Seven weight sets were formed from either uni-variate or multi-variate PLS analyses. Accuracy tests were done by testing the classification of measured pH values of 74 soil profiles with different vulnerability maps and evaluating the areas that were not the AS soil within the groups of medium to high AS soil probability in the land-cover and soil-type datasets. In comparison to the other weight sets, the weight set of multi-variate PLS analysis of the matrix of total Ni2+& S or total Cu2+& S had the robust predictive performance. Sensitivity anal-ysis was done in the weight set of total Ni2+& S, and the results of sensitivity analyses showed that the availability of ditches, and the change in the terrain sur-faces, the altitude level, and the slope had a high influence to the vulnerability map of AS soils. The study showed that using multivariate analysis was a very good approach methodology for predicting the probability of acid sulfate soil.