Search

At the University of Vermont, an interdisciplinary faculty team developed an introductory watershed science field course. This course honed field skills and catalyzed communication across water-related disciplines without requiring specific prerequisites. Five faculty (geology, engineering, geography, natural resources) taught the four-credit course, highlighting interactions between the hydrosphere, biosphere, and solid Earth. The course, based in the Winooski River watershed, followed the river from its headwaters downstream to its outlet in Lake Champlain focusing on data collection and analysis methods, while exploring threats to this freshwater ecosystem. This course was offered as a summer field course in 2007. Student learning was assessed using weekly summative assignments and final presentations incorporating field data and acquired knowledge. Attitude and knowledge surveys, administered before and after this first year, documented increased self-assessed learning, affinity for the field learning environment, and that the course provided training relevant to various disciplines. The fiscally unsustainable summer model, and course evaluations guided major revisions to the course. The second offering, in 2009, met weekly during spring term to provide students with context before a two-week field component. This field component was held immediately after classes ended to avoid the need to pay faculty summer salaries.

Microbial metabolism is the engine that drives global biogeochemical cycles, yet many key transformations are carried out by microbial consortia over short spatiotemporal scales that elude detection by traditional analytical approaches. We investigate syntrophic sulfur cycling in the 'pink berry' consortia of the Sippewissett Salt Marsh through an integrative study at the microbial scale. The pink berries are macroscopic, photosynthetic microbial aggregates composed primarily of two closely associated species: sulfide-oxidizing purple sulfur bacteria (PB-PSB1) and sulfate-reducing bacteria (PB-SRB1). Using metagenomic sequencing and (34) S-enriched sulfate stable isotope probing coupled with nanoSIMS, we demonstrate interspecies transfer of reduced sulfur metabolites from PB-SRB1 to PB-PSB1. The pink berries catalyse net sulfide oxidation and maintain internal sulfide concentrations of 0-500 μm. Sulfide within the berries, captured on silver wires and analysed using secondary ion mass spectrometer, increased in abundance towards the berry interior, while δ(34) S-sulfide decreased from 6‰ to -31‰ from the exterior to interior of the berry. These values correspond to sulfate-sulfide isotopic fractionations (15-53‰) consistent with either sulfate reduction or a mixture of reductive and oxidative metabolisms. Together this combined metagenomic and high-resolution isotopic analysis demonstrates active sulfur cycling at the microscale within well-structured macroscopic consortia consisting of sulfide-oxidizing anoxygenic phototrophs and sulfate-reducing bacteria.

Microbial metabolism is the engine that drives global biogeochemical cycles, yet many key transformations are carried out by microbial consortia over short spatiotemporal scales that elude detection by traditional analytical approaches. We investigate syntrophic sulfur cycling in the 'pink berry' consortia of the Sippewissett Salt Marsh through an integrative study at the microbial scale. The pink berries are macroscopic, photosynthetic microbial aggregates composed primarily of two closely associated species: sulfide-oxidizing purple sulfur bacteria (PB-PSB1) and sulfate-reducing bacteria (PB-SRB1). Using metagenomic sequencing and (34) S-enriched sulfate stable isotope probing coupled with nanoSIMS, we demonstrate interspecies transfer of reduced sulfur metabolites from PB-SRB1 to PB-PSB1. The pink berries catalyse net sulfide oxidation and maintain internal sulfide concentrations of 0-500 μm. Sulfide within the berries, captured on silver wires and analysed using secondary ion mass spectrometer, increased in abundance towards the berry interior, while δ(34) S-sulfide decreased from 6‰ to -31‰ from the exterior to interior of the berry. These values correspond to sulfate-sulfide isotopic fractionations (15-53‰) consistent with either sulfate reduction or a mixture of reductive and oxidative metabolisms. Together this combined metagenomic and high-resolution isotopic analysis demonstrates active sulfur cycling at the microscale within well-structured macroscopic consortia consisting of sulfide-oxidizing anoxygenic phototrophs and sulfate-reducing bacteria.

Wetlands are integral to the global carbon cycle, serving as both a source and a sink for organic carbon. Their potential for carbon storage will likely change in the coming decades in response to higher temperatures and variable precipitation patterns. We characterized the dissolved organic carbon (DOC) and dissolved organic matter (DOM) composition from 12 different wetland sites across the USA spanning gradients in climate, landcover, sampling depth, and hydroperiod for comparison to DOM in other inland waters. Using absorption spectroscopy, parallel factor analysis modeling, and ultra‐high resolution mass spectroscopy, we identified differences in DOM sourcing and processing by geographic site. Wetland DOM composition was driven primarily by differences in landcover where forested sites contained greater aromatic and oxygenated DOM content compared to grassland/herbaceous sites which were more aliphatic and enriched in N and S molecular formulae. Furthermore, surface and porewater DOM was also influenced by properties such as soil type, organic matter content, and precipitation. Surface water DOM was relatively enriched in oxygenated higher molecular weight formulae representing HUPHigh O/C compounds than porewaters, whose DOM composition suggests abiotic sulfurization from dissolved inorganic sulfide. Finally, we identified a group of persistent molecular formulae (3,489) present across all sites and sampling depths (i.e., the signature of wetland DOM) that are likely important for riverine‐to‐coastal DOM transport. As anthropogenic disturbances continue to impact temperate wetlands, this study highlights drivers of DOM composition fundamental for understanding how wetland organic carbon will change, and thus its role in biogeochemical cycling. Plain Language Summary: Dissolved organic matter (DOM) is often the most reactive form of organic carbon in wetlands, but its molecular characteristics and distribution are not well defined across different wetland types. We characterized DOM and analyzed dissolved organic carbon (DOC) concentrations across 12 temperate USA wetlands during wet and dry seasons from both surface‐ and porewaters. Wetland DOM primarily originates from the landscapes with greater DOC concentrations than similar inland waters such as lakes and rivers. DOM composition differs mostly by geographic site, suggesting that forested wetlands contain more aromatic DOM compounds from vegetation and soil than grassland/herbaceous wetlands, which contain DOM that is more processed. DOM composition between surface and porewaters is influenced by local ecological properties such as soil content and precipitation, with porewater compositions heavily impacted by mineral interactions. Finally, we identified common molecular signatures across all wetlands that have also been found in the largest arctic rivers, highlighting the role of wetlands as potential organic carbon sources to rivers and coastal systems. As precipitation and temperature patterns continue to change across temperate regions, the balance between different carbon pools will likely respond, particularly between the distribution and composition of wetland surface and porewater organic matter. Key Points: Wetlands contain higher dissolved organic carbon (DOC) concentrations and greater aromatic dissolved organic matter (DOM) composition than other inland waters across the USAWetland DOM composition differs spatially between forested and grassland/herbaceous landcover as well as between surface and porewatersPersistent molecular formulae are observed across all wetlands that may be important for riverine‐to‐coastal DOM cycling [ABSTRACT FROM AUTHOR]

A novel and promising application of a geochemical tool adapted to medical science is the thermodynamic and kinetic modeling of the behavior of minerals in fluids similar to lung fluids (or simulated lung fluids, SLF). Reaction-path modeling for chrysotile, anorthite, K-feldspar, talc, muscovite, kaolinite, albite, and quartz under physiologic conditions in SLF gives dissolution times for these minerals as: chrysotile < anorthite < K-feldspar < talc < muscovite = kaolinite = albite = quartz. For the reaction of these minerals with SLF, hydroxylapatite (a mineral initially supersaturated in SLF) and several other secondary minerals were predicted to form (e.g., mesolite is predicted to precipitate during dissolution reactions of other [Al.sup.3+]-containing minerals). Batch experiments using SLF and a brucite/chrysotile mineral mixture confirm that hydroxylapatite forms during reactions in SLF, potentially a function of having a seed crystal in the brucite, chrysotile, or hydromagnesite (predicted to form from brucite dissolution) present. Moreover, SEM analysis of lung tissue also confirms the formation of calcium phosphates (e.g., hydroxylapatite). Reaction-path modeling of minerals under physiologic conditions provides insight into mineral behavior in the body; predicted mineralization pathways associated with pleural plaques and the predicted formation of [Al.sup.3+]-bearing minerals during reaction-path modeling deserve attention when considering pathologies in the body. Keywords: Medical mineralogy, mineral dissolution, Geochemist workbench, reaction-path modeling, lung mineralogy DOI: 10.2138/am.2010.3434

An unusual arsenate mineral, mansfieldite (AlAsO4·2H2O), was identified as a pigment for the first time as the principal white colorant on two Himalayan thangka paintings at the Indianapolis Museum of Art at Newfields. The co-occurrence of this unusual mineral pigment provides support for the belief that the two artworks are members of a cycle of paintings originating from the same workshop, perhaps from Chamdo, Tibet. The complete palettes of both artworks are identical, including the use of mansfieldite, brochantite, malachite, azurite, vermilion, gold, orpiment, and a carbon-based black in a glue binder on a calcite and gypsum-primed cotton fabric. [ABSTRACT FROM AUTHOR]

The Richmond Mine at Iron Mountain, Shasta County, California, USA provides an excellent opportunity to study the chemical and biological controls on acid mine drainage (AMD) generation in situ, and to identify key factors controlling solution chemistry. Here we integrate four years of field-based geochemical data with 16S rRNA gene clone libraries and rRNA probe-based studies of microbial population structure, cultivation-based metabolic experiments, arsenopyrite surface colonization experiments, and results of intermediate sulfur species kinetics experiments to describe the Richmond Mine AMD system. Extremely acidic effluent (pH between 0.5 and 0.9) resulting from oxidation of approximately 1 × 105 to 2 × 105 moles pyrite/day contains up to 24 g/1 Fe, several g/1 Zn and hundreds of mg/l Cu. Geochemical conditions change markedly over time, and are reflected in changes in microbial populations. Molecular analyses of 232 small subunit ribosomal RNA (16S rRNA) gene sequences from six sites during a sampling time when lower temperature (0.8) conditions predominated show the dominance of Fe-oxidizing prokaryotes such as Ferroplasma and Leptospirillum in the primary drainage communities. Leptospirillum group III accounts for the majority of Leptospirillum sequences, which we attribute to anomalous physical and geochemical regimes at that time. A couple of sites peripheral to the main drainage, "Red Pool" and a pyrite "Slump," were even higher in pH (>1) and the community compositions reflected this change in geochemical conditions. Several novel lineages were identified within the archaeal Thermoplasmatales order associated with the pyrite slump, and the Red Pool (pH 1.4) contained the only population of Acidithiobacillus. Relatively small populations of Sulfobacillus spp. and Acidithiobacillus caldus may metabolize elemental sulfur as an intermediate species in the oxidation of pyritic sulfide to sulfate. Experiments show that elemental sulfur which forms on pyrite surfaces is resistant to most oxidants; its solublization by unattached cells may indicate involvement of a microbially derived electron shuttle. The detachment of thiosulfate (S2O32-) as a leaving group in pyrite oxidation should result in the formation and persistence of tetrathionate in low pH ferric iron-rich AMD solutions. However, tetrathionate is not observed. Although a S2O32--like species may form as a surface-bound intermediate, data suggest that Fe3+ oxidizes the majority of sulfur to sulfate on the surface of pyrite. This may explain why microorganisms that can utilize intermediate sulfur species are scarce compared to Fe-oxidizing taxa at the Richmond Mine site.

Determination of iron speciation in water is one of the major challenges in environmental analytical chemistry. Here, we present and discuss a method for sampling and analysis of dissolved Fe(II), Fe(III), and Fetotalconcentrations in natural thermal water covering a wide range of temperature, pH, chemical composition, and redox conditions. Various methods were tried in the collection, preservation, and storage of natural thermal water samples for the Fe(II) and Fe(III) determinations, yet the resultant Fe speciation determined was often found to be significantly affected by the methodology applied. Due to difficulties in preserving accurate Fe speciation in natural samples for later laboratory analysis, a field-deployed on-site method using ion-chromatography and spectrophotometry was developed and tested. The IC-Vis method takes advantage of ion chromatographic separation of Fe(II) and Fe(III), followed by post-column colour reaction and spectrophotometric detection, thus allowing analysis of Fe(II) and Fe(III) in a single 15-minute run. Additionally, Fetotalcan be determined after sample oxidation. The analytical detection limits are ~2 µg L−1(LOD) using 200–1000 µL injection volumes and depend on the blank and reagent quality. The power of this method relies on the capability to directly determine a wide range of absolute and relative concentrations of Fe(II) and Fe(III) in the field. The field-deployed IC-Vis method was applied for the determination of Fe(II) and Fe(III) concentrations in natural thermal water with discharge temperatures ranging from 12°C to 95°C, pH between 2.46 and 9.75, and Fetotalconcentrations ranging from a few μg L−cup to 8.3 mg L−1. [ABSTRACT FROM PUBLISHER]