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Spatial and temporal variations in pore water compositions are characterized for a deep regolith profile developed on a marine terrace chronosequence near Santa Cruz California. Variations are resolved in terms of the dominance of either a lithogenic process, i.e. chemical weathering, or a biogenic process, i.e. plant nutrient cycling. The concept of elemental fractionation is introduced describing the extent that specific elements are mobilized and cycled as a result of these processes.
Quantitative X-Ray Diffraction (qXRD) analysis of the <2 mm sediment fraction from surface (sea floor) samples, and marine sediment cores that span the last 10–12 cal ka BP, are used to describe spatial and temporal variations in non-clay mineral compositions for an area between Kangerlussuaq Trough and Scoresby Sund (∼67°–70°N), East Greenland. Bedrock consists primarily of an early Tertiary alkaline complex with high weight% of pyroxene and plagioclase. Farther inland and to the north, the bedrock is dominantly felsic with a high fraction of quartz and potassium feldspars. Principal Component (PC) analysis of the non-clay sediment compositions indicates the importance of quartz and pyroxene as compositional end...
Categories: Publication; Types: Citation
Hillslopes have been intensively studied by both geomorphologists and soil scientists. Whereas geomorphologists have focused on the physical soil production and transport on hillslopes, soil scientists have been concerned with the topographic variation of soil geochemical properties. We combined these differing approaches and quantified soil chemical weathering rates along a grass covered hillslope in Coastal California. The hillslope is comprised of both erosional and depositional sections. In the upper eroding section, soil production is balanced by physical erosion and chemical weathering. The hillslope then transitions to a depositional slope where soil accumulates due to a historical reduction of channel incision...
Circulating drilling fluid is often regarded as a contamination source in investigations of subsurface microbiology. However, it also provides an opportunity to sample geological fluids at depth and to study contained microbial communities. During our study of deep subsurface microbiology of the Chinese Continental Scientific Deep drilling project, we collected 6 drilling fluid samples from a borehole from 2290 to 3350 m below the land surface. Microbial communities in these samples were characterized with cultivation-dependent and -independent techniques. Characterization of 16S rRNA genes indicated that the bacterial clone sequences related to Firmicutes became progressively dominant with increasing depth. Most...
Categories: Publication; Types: Citation
A new method has been developed for quantifying smectite abundance by sorbing polyvinylpyrrolidone (PVP) on smectite particles dispersed in aqueous solution. The sorption density of PVP-55K on a wide range of smectites, illites and kaolinites is ~0.99 mg/m2, which corresponds to ~0.72 g of PVP-55K per gram of montmorillonite. Polyvinylpyrrolidone sorption on smectites is independent of layer charge and solution pH. PVP sorption on SiO2, Fe2 O3 and ZnO normalized to the BET surface area is similar to the sorption densities on smectites. -Al2O3, amorphous Al(OH)3 and gibbsite have no PVP sorption over a wide range of pH, and sorption of PVP by organics is minimal. The insensitivity of PVP sorption densities to mineral...
Categories: Publication; Types: Citation
Chemical weathering both shapes surface environments through formation of the soil mantle and affects global geochemical cycles such as the carbon cycle. The global and local impacts of weathering processes and of the chemical weathering history of a landscape flavor the questions at the active research front in the field of chemical weathering. Questions of scale, both temporal and spatial, continually emerge. Weathering processes act on mineral surfaces, yet often weathering is studied at soil column or watershed scales. Weathering rates may be determined in laboratory experiments conducted over short time periods, or from analysis of a soil profile formed over geologic time. Out of these disparate approaches...
Categories: Publication; Types: Citation
Millions of pounds of mercury (Hg) were deposited in the river and stream channels of the Sierra Nevada from placer and hard-rock mining operations in the late 1800s and early 1900s. The resulting contaminated sediments are relatively harmless when buried and isolated from the overlying aquatic environment. The entrained Hg in the sediment constitutes a potential risk to human and ecosystem health should it be reintroduced to the actively cycling portion of the aquatic system, where it can become methylated and subsequently bioaccumulated in the food web. Each year, sediment is mobilized within these fluvial systems during high stormflows, transporting hundreds of tons of Hg-laden sediment downstream. The State...
Categories: Publication; Types: Citation
Minnesota forested soils have evolved without the presence of earthworms since the last glacial retreat. When exotic earthworms arrive, enhanced soil bioturbation often results in dramatic morphological and chemical changes in soils with negative implications for the forests’ sustainability. However, the impacts of earthworm invasion on geochemical processes in soils are not well understood. This study attempts to quantify the role of earthworm invasion in mineral chemical weathering and nutrient dynamics along an earthworm invasion chronosequence in a sugar maple forest in Northern Minnesota. Depth and rates of soil mixing can be tracked with atmospherically derived short lived radioisotopes 210Pb and 137Cs. Their...
Categories: Publication; Types: Citation
The spatial and temporal changes in hydrology and pore water elemental and 87Sr/86Sr compositions are used to determine contemporary weathering rates in a 65- to 226-kyr-old soil chronosequence formed from granitic sediments deposited on marine terraces along coastal California. Soil moisture, tension and saturation exhibit large seasonal variations in shallow soils in response to a Mediterranean climate. These climate effects are dampened in underlying argillic horizons that progressively developed in older soils, and reached steady-state conditions in unsaturated horizons extending to depths in excess of 15 m. Hydraulic fluxes (qh), based on Cl mass balances, vary from 0.06 to 0.22 m yr−1, resulting in fluid residence...
Categories: Publication; Types: Citation
Chemical analyses and crystal structure refinements were performed on lithian siderophyllite-3T crystals from granitic pegmatites of the anorogenic Pikes Peak batholith (Colorado) to characterize the crystal chemistry and relations with trioctahedral lithium-bearing micas showing different stacking sequences. Chemical data show that the studied samples fall on the siderophyllite polylithionite join, closer to the siderophyllite end-member. Single-crystal X-ray refinements were carried out on three samples (two of which were taken from core and rim of the same crystal) in space-group P3112 (the agreement factor, Robs, varies between 0.034 and 0.036).Mean bond distances and mean electron counts of M1, M2 and M3 octahedral...
HandLens is a computer program, written in Excel macro language, that calculates the chemistry of minerals in mineral mixtures (for example, in rocks, soils and sediments) for related samples from inputs of quantitative mineralogy and chemistry. For best results, the related samples should contain minerals having the same chemical compositions; that is, the samples should differ only in the proportions of minerals present. This manual describes how to use the program, discusses the theory behind its operation, and presents test results of the program‘s accuracy. Required input for HandLens includes quantitative mineralogical data, obtained, for example, by RockJock analysis of X-ray diffraction (XRD) patterns, and...
Categories: Publication; Types: Citation
We report on soil development as a function of bedrock type and the presence of loess in two high latitude ecosystems (boreal forest and tundra) and from two regions in Alaska?the Yukon-Tanana Upland (YTU, east-central Alaska) and the Seward Peninsula (SP, far-west coastal Alaska). This approach to the study of ‘cold soils‘ is fundamental to the quantification of regional geochemical landscape patterns. Of the five state factors in this study, bedrock and biota (ecosystem; vegetation zone) vary whereas climate (within each area) and topography are controlled. The influence of time is assumed to be controlled, as these soils are thousands of years old (late Quaternary to Holocene). The primary minerals in soils from...
Categories: Publication; Types: Citation
Crystal growth experiments were conducted using potassium alum and calcite crystals in aqueous solution under both non-stirred and stirred conditions to elucidate the mechanism for size-dependent (proportionate) and size-independent (constant) crystal growth. Growth by these two laws can be distinguished from each other because the relative size difference among crystals is maintained during proportionate growth, leading to a constant crystal size variance (??2) for a crystal size distribution (CSD) as the mean size increases. The absolute size difference among crystals is maintained during constant growth, resulting in a decrease in size variance. Results of these experiments show that for centimeter-sized alum...
Categories: Publication; Types: Citation
Shewanella putrefaciens CN32 reduces Fe(III) within two illites which have different properties: the Fithian bulk fraction and the <0.2 m fraction of Muloorina. The Fithian illite contained 4.6% (w/w) total Fe, 81% of which was Fe(III). It was dominated by illite with some jarosite (32% of the total Fe(III)) and goethite (11% of the total Fe(III)). The Muloorina illite was pure and contained 9.2% Fe, 93% of which was Fe(III). Illite suspensions were buffered at pH 7 and were inoculated with CN32 cells with lactate as the electron donor. Select treatments included anthraquinone-2,6-disulfonate (AQDS) as an electron shuttle. Bioproduction of Fe(II) was determined by ferrozine analysis. The unreduced and bioreduced...
Categories: Publication; Types: Citation
Quantitative mineralogy correlates with major-, minor- and trace-element chemistry for 387 samples of A-horizon and deeper soils collected from east–west and north–south transects across the USA and Canada, where the deeper soils were collected beneath the A-horizon samples. Concentrations of the major elements correlate with specific mineral phases. Minor- and trace-element concentrations correlate with the same phases as the major elements with which they share similar geochemical behavior. Concentrations of quartz and feldspar correlate with precipitation trends east of the Rocky Mountains, and are independent of the underlying rock type and age, indicating that the weathering of soils in this region may have...
Categories: Publication; Types: Citation
In order to gain more information about the fate of Cryptosporidium parvum oocysts in tropical volcanic soils, the transport and attachment behaviors of oocysts and oocyst-sized polystyrene microspheres were studied in the presence of two soils. These soils were chosen because of their differing chemical and physical properties, i.e., an organic-rich (43–46% by mass) volcanic ash-derived soil from the island of Hawaii, and a red, iron (22–29% by mass), aluminum (29–45% by mass), and clay-rich (68–76% by mass) volcanic soil from the island of Oahu. A third agricultural soil, an organic- (13% by mass) and quartz-rich (40% by mass) soil from Illinois, was included for reference. In 10-cm long flow-through columns,...