A research report submitted to the Faculty of Science, in partial fulfilment of the requirements for the degree of Master of Science, University of the Witwatersrand. Johannesburg, 2016. / Mining and associated anthropogenic activities have improved the livelihoods and economy of many countries but negatively impacted the environment and caused detrimental effects on fresh and ground water systems through the generation of acid mine drainage (AMD). The study evaluated three macrophyte species of P. communis, S.corymbosus and T. capensis for uptake of Mg, P, S, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, and Pb in acid mine drainage polluted water. The concentration of elements was also determined in sediments and water so as to calculate the bioconcentration and translocation factors in various parts of the macrophtes. The homogenised plant samples were milled using a Fritsch Pulverisette 6 Mill into pulverized powder and element analysis was done using Spectroscout Geo+ XRF Analyzer Pro. Sediment samples were digested with microwave assisted extraction and analysed by inductively coupled plasma optical emission spectrometry (ICP-OES). Water samples were analysed directly using ICP-OES after filteration with ICP-OES. The concentration levels of these elements in water were compared in all the sites to determine which section of the site (inflow, midflow and outflow) have high amount of the selected elements. The results indicated that elements distribution varied in all the points where the water samples were collected. The concentration level of sediment was compared to the concentration levels of elements in the roots, rhizomes and leaves to determine the translocation and bio concentration factor (TC and BCF). Drinking water quality standards by international organisations were also used as a guideline to compare the concentration levels of elements found in water. Iron (Fe), Nickel (Ni), Manganese (Mn) and Copper (Cu) to determine whether their concentrations in the water were above or below the acceptable levels. the concentrations of Fe, Ni, Mn and Cu were found to be above the international water quality standards for drinking water and their average concentrations was 2230, 282, 5950 and 14080 μg/l respectively. The study found out that in autumn, Mg, S, P, and Mo were highly accumulated by leaves of T. capensis, S. Corymbosus leaves and rhizomes as well as the P. communis leaves and the highest concentrations were 6.61, 72900, 2.00 μg/g respectively. In autumn, Co was the only element highly accumulated by the roots of T. capensis with the highest concentration of 342.80 μg/g. On the other hand, Cr and Fe, was highly accumulated by S. corymbosus roots with the highest concentration of 279.20 and 10.03 μg/g in summer. In summer, Cr, Mn, Ni, Cu, Zn and Pb were highly accumulated by the roots of P. communis and the concentrations were 279.20, 39390, 204.10, 299.50, 813.80 and 47.5 μg/g respectively. The results show that although the plant species accumulated the elements in various concentrations, there was no plant species that accumulated all the selected elements in higher concentrations than the other plant species. They all accumulated a variety of elements in varying amounts and stored them in their different parts. Finally, in all the three plant species analysed, the leaves were the best accumulator of Mg, S, and Mo, whilst the roots were the best accumulators of Cr, Fe, Co, Ni, Cu, Zn and Pb. Since the translocation and bioconcentration factors showed that the macrophyte species accumulated higher concentrations of elements than water and sediments, they can be regarded as hyperaccumulators. Macrophytes species can uptake and accumulate in their different parts various elements and they have the potential to clean the heavy metal polluted sites due to their phytostabilisation and phytoextraction abilities. / LG2017

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Masters of Science, 2017 / The tailoring of zeolites surface properties using organic functionalising agents displaying higher binding affinity for metal ions is a widely explored approach for water treatment. In this study, amine functionalised zeolites and phosphate functionalised zeolites were separately synthesised from similar natural zeolite precursors using reflux methods. The surface composition and morphological elucidations were achieved by characterising the adsorbents using Fourier Transform Infra-red spectroscopy (FTIR), thermogravimetric analysis (TGA), Zeta potential, Point of zero charge (pHPZC), and the Brunauer, Emmett and Teller analysis (BET). In case study 5.1, the sorption mechanisms of the uranyl ion onto amine functionalised zeolites (AMZ), activated carbon (AC) and natural zeolite (NZ) were studied as function of various environmental batch parameters. There was effective adsorption when uranium existed as uranyl ions: UO22+ and UO2OH+. The data fitted numerous kinetic and isotherm models suggesting that the equilibrium mechanisms were characteristic of a combination of chemisorption and physisorption for these three adsorbents. The Dubinin-Radushkevich (DR) model did not fit the data and therefore the energy values derived from it were not used to predict the mechanisms involved. However, the thermodynamic evaluations of parameters ∆H, ΔG and ∆S° showed that equilibrium mechanisms were exothermically, randomly and spontaneously favoured for all adsorbents at temperatures ranging between 22 and 40oC. The adsorption capacity of 0.452 mg g-1 was achieved at pH 3 by 500 mg AC dosage using 20 mL volume of 10 mg L-1 uranyl ion solution after equilibrating for 6 h within the temperature ranges of 22 to 30oC. Under the same conditions of sorbent dosage of 500 mg, uranyl solution volume of 20 mL and 10 mg L-1 U(VI) solution concentration, the maximum adsorption capacity of 0.506 mg g-1 for NZ and 0.480 mg g-1 for AMZ were both achieved at pH 4 after equilibration time of 21 h and 6 h with the optimum temperature range of 22 to 30oC, respectively. The model results predict that intraparticle diffusion thorough pores decreased in the order AC ˃ NZ ˃ AMZ while estimating that chemisorption occurred in a reverse order. On the basis of the modelled data, it was deduced that amine functionalisation of natural zeolites improves their chemisorption capability for uranyl ion and can therefore be used as a cost efficient adsorbent for small-scale remediation of contaminated aquatic systems. In another case study 5.2, the surface properties of successfully prepared aminomethyl phosphonic acid functionalised natural zeolite (APZ) were compared to those of commercial silica polyamine composites (SPC) for uranium uptake in batch aqueous solutions. The FTIR spectrum revealed that (3-aminotrimethyl) phosphonic acid functional groups were successfully grafted onto natural zeolite. The TGA analysis showed that the APZ had higher thermal stability and fewer active sites compared to SPC. The optimum adsorption capacity (qe) of 49 mg g-1 and 44 mg g-1 uranium was achieved using 25 mg SPC and 100 mg APZ, respectively at pH 4, 25oC after 1 and 6 h equilibrating time. The data best fitted the pseudo second-order kinetic model and Freundlich isotherm model. The thermodynamic studies showed that adsorption occurred chemically and exothermically for both APZ and SPC. The overall selectivity order for APZ was; Na ˃ Mn ≥ U ˃ Ca ˃ Fe and for SPC was; Fe ˃ Mn ≥ Ca ˃ U˃ Na. The findings showed that phosphate- and amine-functionalised zeolite bind strongly to uranium compared to the unmodified natural zeolite and other conventional adsorbents such as activated carbon. Their selectivity for this element was commendable. With further improvements in the synthetic protocols e.g. by using microwave-based methods, it should be possible to obtain functionalised zeolite that has superior properties to SPC. / XL2017

Mine-impacted water bodies are considered to be one of the most serious threats to the environment. These can be highly acidic and often contain elevated concentrations of sulfate and soluble metals. The microbial generation of H2S by reduction of more oxidized sulfur species, and consequent precipitation of metal sulfides, known as biosulfidogenesis, is a promising technology for remediating acid mine drainage (AMD). The objective of this work was to develop an integrated system for remediating a target AMD at an operating mine in northern Brazil using a single low pH anaerobic sulfidogenic bioreactor (aSRBR) and an aerobic manganese-oxidizing bioreactor. A synthetic version of the mine water, which contained 7.5 mM copper and lower concentrations (< 0.25 mM) of other transition metals (Zn, Ni, Co and Mn) was used in the experimental work. In the first stage, H2S generated in the aSRBR was delivered to an off-line vessel containing synthetic AMD, which removed > 99% copper (as CuS) while no co-precipitation of other metals was apparent. The partly-processed AMD was then dosed with glycerol and fed into the aSRBR where zinc, nickel and cobalt were precipitated. The effect of varying the pH and temperature of the bioreactor was examined, and > 99% of Ni, Zn and Co were precipitated in the aSRBR when it was maintained at pH 5.0 and 35ºC. The bacterial communities, which were included 4 species of acidophilic sulfate-reducing bacteria, varied in composition depending on how the bioreactor was operated, but were both robust and adaptable, and changes in temperature or pH had only short-term impact on its performance. Manganese was subsequently removed from the partly-remediated synthetic AMD using upflow bioreactors packed with Mn(IV)-coated pebbles from a freshwater stream which contained Mn(II)-oxidizers, such as the bacterium Leptothrix discosphora and a fungal isolate belonging to the order Pleosporales. This caused soluble Mn (II) to be oxidised to Mn (IV) and the precipitation of solid-phase Mn (IV) oxides. Under optimised conditions, over 99% manganese in the processed AMD was removed. Metal sulfides (ZnS, CoS and NiS) that had accumulated in the aSRBR over 2 years of operation were solubilised by oxidative (bio)leaching at low pH. With this, ~ 99% Zn, ~ 98% Ni and ~ 92% Co were re-solubilised, generating a concentrated lixiviant from which metals could be selectively recovered in further downstream processes. The use of methanol and ethanol either alone or in combination with glycerol were evaluated as alternative electron donors for biosulfidogenesis. Methanol was not consumed in the bioreactor, though sulfate reduction was not inhibited in the presence of up to 12 mM methanol. In contrast, ethanol was readily metabolised by the bacterial community and sulfate reduction rates were relatively high compared to glycerol. Two acidophilic algae were characterised and their potential to act as providers of electron donors for biosulfidogenesis was also evaluated. Although algal biomass was able to fuel sulfate reduction in pure cultures of aSRB and in the aSRBR, rates were much lower than when either glycerol or ethanol were used.

Difficulties associated with the study of microbial communities, such as low proportions of cultivable species, have been addressed in recent years with the advent of a range of sequencing technologies and bioinformatic tools. This is enabling previously unexplored communities to be characterised and utilised in a range of biotechnology applications. In this thesis bioinformatic methods were applied to two datasets of biotechnological interest: microbial communities found living with the oil-producing alga Botryococcus braunii and microbial communities in acid mine drainage (AMD). B. braunii is of high interest to the biofuel industry due to its ability to produce high amounts of oils, in the form of hydrocarbons. However, a number of factors, including low growth rates, have prevented its cultivation on an industrial scale. Studies show B. braunii lives in a consortium with numerous bacteria which may influence its growth. This thesis reports both whole genome analysis and 16S rRNA gene sequence analysis to gain a greater understanding of the B. braunii bacterial consortium. Bacteria have been identified, some of which had not previously been documented as living with B. braunii, and evidence is presented for ways in which they may influence growth of the alga, including B-vitamin synthesis and secretion systems. AMD is a worldwide problem, polluting the environment and negatively impacting on human health. This by-product of the mining industry is a problem in the South West of England, where disused metalliferous mines are now a source of AMD. Bioremediation of AMD is an active area of research; sulphur-reducing bacteria and other bacteria which can remove toxic metals from AMD can be utilised for this purpose. Identifying bacteria and archaea that are able to thrive in AMD and which also have these bioremediation properties is therefore of great importance. Metagenomic sequencing has been carried out on the microbial community living in AMD sediment at the Wheal Maid tailings lagoon near Penryn in Cornwall. From these data have been identified a diverse range of bacteria and archaea present at both the sediment surface level and at depth, including microorganisms closely related to taxa reported from metalliferous mines on other continents. Evidence has been found of sulphur-reducing bacteria and of pathways for various other bioremediation-linked processes.

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xiii, 119 p. : ill. (some col.), col. maps. Includes abstract. Includes bibliographical references (p. 105-110).

<p>Natural and constructed clay liners are routinely used to contain waste and wastewater. The impact of acidic solutions on the geochemistry and mineralogy of clays has been widely investigated in relation to acid mine drainage systems at pH > 1.0. The impact of sulfuric acid leachate characterized by pH < 1.0, including potentially negative pH values on the geochemistry and mineralogy of clays is, however, not clear.</p> <p>To address this deficiency a series of batch and diffusion cell studies, investigating the geochemical and mineralogical impacts of H₂SO₄ solutions (pH 5.0 to -3.0), were conducted on three mineralogically distinct clays (Kc, Km, and BK). Batch testing was conducted at seven pH treatments (5.0, 3.0, 1.0, 0.0, -1.0, -2.0 and -3.0) using standardized sulfuric acid solutions for four exposure periods (14, 90, 180, and 365 d). Aqueous geochemical, XRD, and Si and Al XANES analyses showed: increased dissolution of aluminosilicates with decreasing pH and increasing exposure period; preferential dissolution of aluminosilicate Al-octahedral layers relative to Si-tetrahedral layers; formation of an amorphous silica-like phase that was confined to the surface layer of the altered clay samples at pH ⤠0.0 and t ⥠90 d; and precipitation of anhydrite and a Al-SO₄-rich phase (pH ⤠-1.0, t ⥠90 d).</p> <p>The diffusive transport of H₂SO₄ (pH =1.0, -1.0, and -3.0) through the Kc and Km clays for 216 d was examined using single reservoir, constant concentration, diffusion cells. The diffusive transport of H⁺ within the cells was modeled using 1-D transport models that assumed no absorption, linear absorption, and non-linear absorption of H⁺. The absorption isotherms were calculated from the pH 5.0, 3.0, and 1.0 batch experiment results, which were assumed representative of H⁺ absorption at pH < 1.0. However, model results indicated that the batch test results can not account for the observed H⁺ consumption in all cells and greatly underestimate the amount of H⁺ consumption in the pH -1.0 and -3.0. In the Kc and Km diffusion cells, above-background Ca, Al, Fe, and Si aqueous concentrations were associated with depth intervals characterized by decreased pH values. Respective peak concentrations of 325, 403, 176, 11.7, and 1.38 x 10³ μmol g^-1 (Kc) and 32.4, 426, 199, 7.2, and 1.22 x 10³ μmol g^-1 (Km) were measured in the pH -3.0 cells. XRD results showed that the elevated concentrations corresponded to the loss of carbonates and montmorillonite peaks and decreased peak intensities for illite and kaolinite in depth intervals with pH ⤠1.0, in the Kc and Km pH -1.0 and -3.0 cells.</p> <p>The combined results of these studies indicated that the long-term diffusion of H₂SO₄ through clays at pH < 1.0 will result in a large amount of primary phase dissolution; however, this will be accompanied by precipitation of soluble Ca and Al sulfate salts and amorphous silica, especially at pH ⤠0.0. Additionally, the presence of even a small amount of carbonate will serve to greatly buffer the diffusive transport of H₂SO₄ through clays, even at a source pH of -3.0.</p>

A rigorous laboratory and field study to measure and compare low sulfide waste rock and drainage characteristics at various scales has been designed and implemented. The field study was constructed at the Diavik diamond mine in the Northwest Territories, Canada. Three well-instrumented, 15 m high test piles and three sets of 2 m scale experiments were constructed from run of mine waste rock. Diavik waste rock is comprised of granite and metasedimentary biotite schist country rock. The biotite schist contains the sulfide minerals, principally pyrrhotite. Diavik segregates waste rock based on sulfur content. One test pile contains waste rock with 0.035 wt. % S, within the operational sulfur target of < 0.04 wt. % S for lower sulfur waste rock designation. The second pile contains waste rock with 0.053 wt. % S, lower than the operational sulfur target of > 0.08 wt. % S for the higher sulfur waste rock designation. The third pile contains a core of 0.082 wt. % S waste rock which is within the operational sulfur target of > 0.08 wt. % S for the higher sulfur waste rock. The third pile has been re-contoured and capped by a 1.5 m of till and 3 m of lower sulfide waste rock as per the current reclamation plan for the higher sulfide waste rock pile. The test piles were built using standard end-dumping and push-dumping methods. Instrumentation was installed at the base of each pile and on four angle of repose tip faces, as well as in the covers of the third pile. Instrumentation was selected to measure matrix flow, pore water and bulk pile geochemistry, gas-phase oxygen and carbon dioxide concentrations, temperature evolution, microbiological populations, permeability to air, and thermal conductivity, and to resolve mass and flow balances. Instruments were designed to permit measurements at multiple scales. During pile construction samples of the < 50 mm fraction of waste rock were collected. The samples were analysed for sulfur content and particle size distribution. Particle size distributions for the lower and higher sulfur waste rock are similar but the higher sulfur waste rock has a higher proportion of fines. Particle size distributions for both waste rock types suggest the piles have rock-like characteristics rather than soil-like characteristics. Sulfur concentrations vary with the scale of measurement: concentrations of smaller size fractions are higher than larger size fractions. Acid-base accounting using standard methods and site-specific mineralogical information suggest that the waste rock is acid generating. However, when acid-base accounting is compared to effluent pH and alkalinity, the data suggest these calculations may be conservative. Drainage effluent from the higher sulfide test pile was measured for field parameters (pH, Eh, alkalinity) and dissolved cations, anions and nutrients. The geochemical equilibration model MINTEQA2 was used to interpret potential geochemical controls on solution chemistry. The pH decreases to < 5, concomitant with the minimum alkalinity of < 1 mg L-1 (as total CaCO3), suggesting all available alkalinity is consumed by acid-neutralizing reactions. Sulfate concentrations reach 1995 mg L-1. Calculated saturation indices of Al (oxy)hydroxides and Al hydroxysulfate species, and pH suggest Al oxyhydroxide dissolution is buffering pH at times. Concentrations of Fe (< 0.37 mg L-1), Fe (II) and calculated saturation indices of Fe(III) (oxy)hydroxide species suggests that Fe is predominantly Fe(III) and Fe is being controlled by secondary mineral precipitation. The dissolved trace metals Mn (<19.2 mg L-1), Ni (<10.4 mg L-1), Co (<1.8 mg L-1), Zn (<0.9 mg L-1), Cd (<0.015 mg L-1) and Cu (<0.05 mg L-1) show increasing trends in the effluent water. No dissolved trace metals appear to have secondary mineral controls. Elevated SO4, Al, Fe dissolved metals Ni, Co, Zn, Cd and Cu, and depressed pH values suggest sulfide mineral oxidation is occurring in the test pile containing 0.053 wt. % S.

The aim of the study was to map the extent of Fe, Cu, Pb, As, Zn and S contamination in the area surrounding the Nasa silver mine. The mine operated between 1635 and 1810 with some prospecting performed in 1889, and has become infamous for the gruesome ways that the indigenous people were treated during the early years of operation. This study tested three hypotheses through a geochemical survey: 1) sulfide oxidation is still active in the abandoned mine, 2) the soil downslope of the mine is contaminated by mine drainage, and 3) the stream downslope of the mine is affected in the same way. All three hypotheses were valid, as the results showed that still, &gt;200 years after mining operations ceased, signs of the historical mining are clearly visible in the surrounding environment. Acidic conditions were discovered in surface waters close to the waste rock piles, which indicates active sulfide oxidation. In addition, elevated levels of Fe, Cu, Pb, As, Zn and S were found in both soil and stream sediment downslope of the mines, as compared to reference localities upstream the mine (p &lt;0.05). These results suggest that previous assessments of the mine being no threat to the environment may not be entirely correct. This study illustrates how mining waste can continue to affect the local, sub-arctic environment long after mining operations have ceased.

A rigorous laboratory and field study to measure and compare low sulfide waste rock and drainage characteristics at various scales has been designed and implemented. The field study was constructed at the Diavik diamond mine in the Northwest Territories, Canada. Three well-instrumented, 15 m high test piles and three sets of 2 m scale experiments were constructed from run of mine waste rock. Diavik waste rock is comprised of granite and metasedimentary biotite schist country rock. The biotite schist contains the sulfide minerals, principally pyrrhotite. Diavik segregates waste rock based on sulfur content. One test pile contains waste rock with 0.035 wt. % S, within the operational sulfur target of < 0.04 wt. % S for lower sulfur waste rock designation. The second pile contains waste rock with 0.053 wt. % S, lower than the operational sulfur target of > 0.08 wt. % S for the higher sulfur waste rock designation. The third pile contains a core of 0.082 wt. % S waste rock which is within the operational sulfur target of > 0.08 wt. % S for the higher sulfur waste rock. The third pile has been re-contoured and capped by a 1.5 m of till and 3 m of lower sulfide waste rock as per the current reclamation plan for the higher sulfide waste rock pile. The test piles were built using standard end-dumping and push-dumping methods. Instrumentation was installed at the base of each pile and on four angle of repose tip faces, as well as in the covers of the third pile. Instrumentation was selected to measure matrix flow, pore water and bulk pile geochemistry, gas-phase oxygen and carbon dioxide concentrations, temperature evolution, microbiological populations, permeability to air, and thermal conductivity, and to resolve mass and flow balances. Instruments were designed to permit measurements at multiple scales. During pile construction samples of the < 50 mm fraction of waste rock were collected. The samples were analysed for sulfur content and particle size distribution. Particle size distributions for the lower and higher sulfur waste rock are similar but the higher sulfur waste rock has a higher proportion of fines. Particle size distributions for both waste rock types suggest the piles have rock-like characteristics rather than soil-like characteristics. Sulfur concentrations vary with the scale of measurement: concentrations of smaller size fractions are higher than larger size fractions. Acid-base accounting using standard methods and site-specific mineralogical information suggest that the waste rock is acid generating. However, when acid-base accounting is compared to effluent pH and alkalinity, the data suggest these calculations may be conservative. Drainage effluent from the higher sulfide test pile was measured for field parameters (pH, Eh, alkalinity) and dissolved cations, anions and nutrients. The geochemical equilibration model MINTEQA2 was used to interpret potential geochemical controls on solution chemistry. The pH decreases to < 5, concomitant with the minimum alkalinity of < 1 mg L-1 (as total CaCO3), suggesting all available alkalinity is consumed by acid-neutralizing reactions. Sulfate concentrations reach 1995 mg L-1. Calculated saturation indices of Al (oxy)hydroxides and Al hydroxysulfate species, and pH suggest Al oxyhydroxide dissolution is buffering pH at times. Concentrations of Fe (< 0.37 mg L-1), Fe (II) and calculated saturation indices of Fe(III) (oxy)hydroxide species suggests that Fe is predominantly Fe(III) and Fe is being controlled by secondary mineral precipitation. The dissolved trace metals Mn (<19.2 mg L-1), Ni (<10.4 mg L-1), Co (<1.8 mg L-1), Zn (<0.9 mg L-1), Cd (<0.015 mg L-1) and Cu (<0.05 mg L-1) show increasing trends in the effluent water. No dissolved trace metals appear to have secondary mineral controls. Elevated SO4, Al, Fe dissolved metals Ni, Co, Zn, Cd and Cu, and depressed pH values suggest sulfide mineral oxidation is occurring in the test pile containing 0.053 wt. % S.

<p>Natural and constructed clay liners are routinely used to contain waste and wastewater. The impact of acidic solutions on the geochemistry and mineralogy of clays has been widely investigated in relation to acid mine drainage systems at pH > 1.0. The impact of sulfuric acid leachate characterized by pH < 1.0, including potentially negative pH values on the geochemistry and mineralogy of clays is, however, not clear.</p> <p>To address this deficiency a series of batch and diffusion cell studies, investigating the geochemical and mineralogical impacts of H₂SO₄ solutions (pH 5.0 to -3.0), were conducted on three mineralogically distinct clays (Kc, Km, and BK). Batch testing was conducted at seven pH treatments (5.0, 3.0, 1.0, 0.0, -1.0, -2.0 and -3.0) using standardized sulfuric acid solutions for four exposure periods (14, 90, 180, and 365 d). Aqueous geochemical, XRD, and Si and Al XANES analyses showed: increased dissolution of aluminosilicates with decreasing pH and increasing exposure period; preferential dissolution of aluminosilicate Al-octahedral layers relative to Si-tetrahedral layers; formation of an amorphous silica-like phase that was confined to the surface layer of the altered clay samples at pH ⤠0.0 and t ⥠90 d; and precipitation of anhydrite and a Al-SO₄-rich phase (pH ⤠-1.0, t ⥠90 d).</p> <p>The diffusive transport of H₂SO₄ (pH =1.0, -1.0, and -3.0) through the Kc and Km clays for 216 d was examined using single reservoir, constant concentration, diffusion cells. The diffusive transport of H⁺ within the cells was modeled using 1-D transport models that assumed no absorption, linear absorption, and non-linear absorption of H⁺. The absorption isotherms were calculated from the pH 5.0, 3.0, and 1.0 batch experiment results, which were assumed representative of H⁺ absorption at pH < 1.0. However, model results indicated that the batch test results can not account for the observed H⁺ consumption in all cells and greatly underestimate the amount of H⁺ consumption in the pH -1.0 and -3.0. In the Kc and Km diffusion cells, above-background Ca, Al, Fe, and Si aqueous concentrations were associated with depth intervals characterized by decreased pH values. Respective peak concentrations of 325, 403, 176, 11.7, and 1.38 x 10³ μmol g^-1 (Kc) and 32.4, 426, 199, 7.2, and 1.22 x 10³ μmol g^-1 (Km) were measured in the pH -3.0 cells. XRD results showed that the elevated concentrations corresponded to the loss of carbonates and montmorillonite peaks and decreased peak intensities for illite and kaolinite in depth intervals with pH ⤠1.0, in the Kc and Km pH -1.0 and -3.0 cells.</p> <p>The combined results of these studies indicated that the long-term diffusion of H₂SO₄ through clays at pH < 1.0 will result in a large amount of primary phase dissolution; however, this will be accompanied by precipitation of soluble Ca and Al sulfate salts and amorphous silica, especially at pH ⤠0.0. Additionally, the presence of even a small amount of carbonate will serve to greatly buffer the diffusive transport of H₂SO₄ through clays, even at a source pH of -3.0.</p>