<p> The need for an expedient and economical field method for identifying the upper boundary of the capillary fringe (CF) led to an investigation of the clay-rich surficial units of two sites in New Iberia, Louisiana. Tension-sensing instruments capable of indirectly measuring water content were installed to monitor changing subsurface conditions throughout the vadose zone in response to water table fluctuation and rainfall. Tension measurements of 10 kPa and 33 kPa, correlated with the agricultural concept of field capacity by previous studies, functioned as indicators of two possible upper capillary fringe surfaces. Interpreted tension boundaries were plotted at depth to outline temporal changes in capillary fringe thicknesses, which ranged from approximately 1&ndash;5 ft depending on rainfall rates. </p><p> A comparison of gravimetric water content profiles with interpreted tension boundaries suggested that CF thickness was heavily influenced by the presence and composition of surficial fill, root systems, and the depth of the shallow water table. Collected tension and water content measurements were plotted as water retention points onto a series of estimated soil water retention curves (SWRCs). The hysteretic nature of soil-water retention relationships of the clay-rich media, evidenced by several examples of near equivalent water contents corresponding to vastly different tension measurements, and vice versa, illustrated the potential errors in basing capillary fringe thickness solely on tension measurements. While tension measurements did prove useful in recording variable conditions in the vadose zone, further research into accounting for hysteresis is required before tension boundaries can be employed in capillary fringe surface identification.</p><p>

<p>Changes in the concentration of atmospheric carbon dioxide (pCO2) affect global climate. Accurate determination of paleo-pCO2 can therefore provide information on the response of climate to changing pCO2. Such pCO2 proxies have been developed from a variety of terrestrial (e.g., plant stomata, paleosol carbonate, and liverworts) and marine (e.g., alkenones and boron) substrates. However, these proxies show a wide range of values and uncertainty throughout the Cenozoic and especially for the early Paleogene (53-63 mya). Here, I demonstrate the use of the carbon isotope composition of n-alkanes extracted from C3 plant waxes as an accurate recorder of changes in atmospheric chemistry. My results show that the uncertainty and range of pCO2 estimates determined using this new proxy are similar to other proxies. Because n-alkanes are abundant, chemically resistant, and not subject to degradation, this proxy represents an excellent opportunity to reconstruct pCO2 across the last 400 Myr of Earth history. By examining across 4 different chain lengths (n-27, n-29, n- 31, and n-33), I find that only n-29 and n-31 show clear changes in carbon isotope discrimination in response to changes pCO2, whereas chain-lengths n-27 and n-31 did not show any significant response. Using chain lengths n-29 and n-31, I calculate early Paleogene pCO2 = 566 ? 190 and 469 ? 165 ppmv (median ? 1?), respectively. These results demonstrate that n-alkanes can serve as a potential pCO2 proxy across geologic timescales.

<p> This study examines the natural background concentrations of arsenic in the soils of southwest Oregon, using new samples in addition to data collected from previous theses (Khandoker, 1997 and Douglas, 1999). The original 213 samples were run by ICP-AES with a reporting limit of 20 ppm, and only three samples had detected values. The original samples were tested again (2013) at a lower reporting limit of 0.2 ppm by ICP-MS, as were 42 new samples (2013), to better ascertain the natural levels of arsenic in undisturbed soils. The aim is to add to the existing DEQ data set, which has been used to establish new regulatory levels based on natural levels in the environment that are both safer and more economically viable than the former risk-based remediation levels (DEQ, 2013). </p><p> The maximum and mean concentrations, respectively, for each province (with high formation map unit) are 85.4 and 21.99 ppm for South Willamette Valley (Tfee), 45.4 and 5.42 ppm for the Klamath Mountains (Jub), 11.9 and 2.76 ppm for the Cascade Range (Tbaa), 10.6 and 5.15 ppm for the Coast Range (Ty), 2.32 and 1.29 ppm for the Basin and Range (Qba) and 1.5 and 1.20 ppm for the High Lava Plains (Tmv). </p><p> In addition, the distribution and variance of arsenic in the A and B soil horizons is assessed in this study by comparing deviation at a single site, and also by comparing A and B horizons of 119 PSU sites. One of 18 new sites sampled for this study (distinguished with the HH prefix), site HH11, was randomly chosen to evaluate differences at a single location. Site HH11 is an Inceptisol soil above volcanic rock (KJdv map unit) located at 275 meters elevation in Douglas County within the Klamath province. Five samples were taken from the A and from the B horizons at site HH11. The means and standard deviations were 3.74 &plusmn; 0.44 for the A horizon and 4.53 &plusmn; 0.39 for the B horizon. The consistency and low deviation within each horizon indicate that a single sample within a horizon is a good representative of that horizon and supports the field methodology used in this study of taking only one sample in the A horizon and one sample in the B horizon. </p><p> Wilcoxon Rank-Sum test determined that A and B horizons for the 119 sites that had data for both the A and B horizons were not statistically different (p-value 0.76). Arsenic concentration is not associated with a particular horizon for these sites. However, differentiation between soil horizons increases with age (Birkeland, 1999), as does accumulation of the iron oxides and sulfide minerals on clay surfaces (McLaren et al., 2006) which concentrate in the B horizon. These associations warrant further study to see how they relate to arsenic level, soil development and age in Oregon soils. </p><p> Lastly, this study statistically examines six potentially important environmental predictors of naturally occurring arsenic in southwestern Oregon: site elevation, geomorphic province, mapped rock type and age, and sample soil order and color (redness). A Classification and Regression Tree Model (CART) determined soil order, elevation and rock type to be of significant importance in determining arsenic concentrations in the natural environment. According to the regression tree, arsenic concentrations are greater within Alfisol and Ultisol/Alfisol and Vertisol soil orders, at lower elevations below 1,207 meters, and within soils from sedimentary, mixed volcanic/sedimentary and unconsolidated rock types.</p>

<p> Magnetic susceptibility is a property that can be used to effectively determine the compositional changes of mineral materials in soil. The objective of this study is to detect the presence of magnetic particles related to the migration of fly ash from a nearby coal-burning power plant over parts of Pointe Coupee Parish, LA. This is based on the idea that the fly ash that is released into the atmosphere during the coal burning process contains heavy metals and magnetic particles in the form of ferrospheres, which can be used to trace back to the source. Maps of the top and sub soil were generated to differentiate the magnetic susceptibility values of the heavy metals potentially attributed to the migration and settling of fly ash onto the surface from any pre-existing or naturally occurring heavy metals in the sub soil. A 60 km² area in Pointe Coupee Parish was investigated in approximately 0.5 km² subsets.</p><p> At each site, a minimum of 20 magnetic susceptibility measurements were obtained using a field probe along with discrete surface and subsurface samples collected for subsequent laboratory analysis. Samples of fly ash obtained directly from the source were also analyzed to verify the field and laboratory analysis. Contour maps representing the spatial distribution of the fly ash along with histograms of magnetic susceptibility values, reflective light microscope, and chemical analysis indicate a correlation between the proximity to the power plant and the predominant wind direction. Acquisition curves of the isothermal remanent magnetization demonstrate the presence of predominantly low coercivity minerals (magnetite) with a small amount of a high-coercivity phase. The microstructure of the magnetic fractions of the fly ash along with select top and sub soil samples were observed using a reflective light microscope for identifying and confirming the presence of ferrospheres associated with fly ash.</p>