Biogeochemical analyses of soils in Clear Creek, Iowa

Proceedings of the Seventh International Conference on Hydroscience and Engineering, Philadelphia, PA, September 2006. http://hdl.handle.net/1860/732This paper reports the results of soil biogeochemical analyses (e.g., organic matter, % of clay, % of sand, CEC, pH, etc.) performed to characterize the biogeochemical properties of soils in the Upper South Amana area, a sub-catchment of the Clear Creek Watershed. Most of these properties are in turn used as inputs to the WEPP (Water Erosion Prediction Project) upland erosion model to predict sediment erosion rates. WEPP is a process-based, event-based, distributed parameter, water flow driven erosion prediction model. Climatic data and Digital Elevation Models (DEM) are also incorporated in the model along with the biogeochemical properties of the soils. The WEPP model is first calibrated and then a sensitivity analysis is performed to identify the governing parameters of upland erosion in the Upper South Amana Area. Such comparison will further strengthen the argument regarding event-based simulations vs. continuous based simulations. The results of this study will be used for supplementary investigation of physical mechanisms of upland erosion processes

A particle tracking technique for bedload motion

Proceedings of the Seventh International Conference on Hydroscience and Engineering, Philadelphia, PA, September 2006. http://hdl.handle.net/1860/732Nowadays, the advances made in scientific visualization techniques have enhanced our capabilities of tracking sediment and measuring sediment rates. The focus of this study is to provide a new experimental approach to determine the displacement speed of particles rolling atop a well packed layer of spheres and provide a formula that describes the average displacement speed of particles as a function of the particles geometry and weight, settling velocity, and the frictional characteristics of flow. For this purpose, this study presents the measurements of the displacement speeds of three different sized spherical particles under varying flow conditions and bed roughness. The particles, ranging in size from 5/8 of an inch to one inch in diameter, primarily experienced motion due to rolling. The displacement speed information is required for the prediction of sediment fluxes, which can be used to model local sediment entrainment in natural gravel streams. For this purpose, a laboratory flume was used to perform 30 experimental runs. The tests were repeated 15 times, or until repeatability was established. Velocity profiles, shear stress, discharge, and bulk velocity were acquired for each run. An ADV and Swoffer were used to obtain the velocity profiles. Sediment motion was monitored using a plan view from a digital camera mounted above the flume. Individual frames depicting a particle’s motion were produced using Asymetrix DVP and Adobe Photoshop 4.0. Data translation software combined the individual frames to calculate the displacement speed of sediment motion. The results are compared with values predicted by bed load formulas developed by Sekine and Lee. Values observed in this experiment are greater than the values predicted by Sekine and less than the values predicted by Lee

The impact of spatially associated factors upon the variability of biogeochemical tracers for soil erosion fingerprinting

Proceedings of the Seventh International Conference on Hydroscience and Engineering, Philadelphia, PA, September 2006. http://hdl.handle.net/1860/732Fingerprinting is a field based measurement technique that unmixes eroded-soils to their sources in order to budget erosion within a watershed. This study focuses upon evaluating tracer variability across a watershed for biogeochemical tracers including nitrogen and carbon stable isotopes (15N, 13C) and the carbon to nitrogen atomic ratio (C/N). We collected 355 surface soils and analyzed them using isotope ratio mass spectrometry to statistically evaluate the significance of four spatially associated factors including: plot-location to account for tracer variability between field plots in a single land-use; slope-location to contrast floodplain versus upland tracers; profile-depth to evaluate sampling depth upon tracer variability; and soil-pit to account for tracer variability from sample replications at the same site. The Upper Palouse Watershed was chosen as the field study site due to well established agriculture and forest land-uses and consistent soil morphology within the land uses. Results of our statistical analysis showed that in the agriculture soil, plot-location, slope location, profile-depth, and soil-pit all significantly impacted the 15N and 13C signatures. In the forest soil, soil-pit dominated data variability with profile-depth and plot-location as significant to a lesser extent. C/N was less sensitive to the spatially associated factors as compared to the stable isotopes. This new knowledge of tracer variability is expected to be used in future fingerprinting studies

Methodological considerations for the development of a predictive relation for cluster microforms in mountain rivers

Proceedings of the Seventh International Conference on Hydroscience and Engineering, Philadelphia, PA, September 2006. http://hdl.handle.net/1860/732Methodological considerations for the development of a predictive relation for the occurrence of cluster microtopography are presented. Clusters are a type of small-scale bedform that occur in gravel bed rivers and have an effect on the overall flow resistance, the local velocity and stress fields, and sediment transport. A desirable tool would therefore be a relation that predicts the presence of cluster microforms in rivers. Possible processes and the associated variables that cluster microtopography might be functional related to are discussed, and logistic regression analysis is presented as a good method for statistically assessing the links between predictor variables and the occurrence of clusters

Effects of a fully submerged boulder within a boulder array on the mean and turbulent flow fields: Implications to bedload transport

The objective of this coupled experimental and numerical study is to provide insight into the mean and turbulent flow fields within an array of fully submerged, isolated, immobile boulders. Our study showed that the velocity defect law performed well for describing the mean flow around the boulder within the array. A prerequisite, however, was to accurately estimate the spatial variability of u* around the boulder, which was achieved via the boundary characteristics method. The u* exhibited considerable spatial variability within the array and form roughness was shown to be up to 2 times larger than the skin roughness in the boulder near-wake region. Because the boulders bear a significant amount of the flow shear, the available bed shear stress for entrainment of the mobile sediment, τ ols , near the boulders was roughly 50% lower than the ambient τ ols . The τ ols variability induced by the boulders could lead to a threefold overestimation of the sediment transport rate

Case report R831X mutation of the androgen receptor gene in an adolescent with Complete Androgen Insensitivity Syndrome and bilateral testicular hamartomata

ABSTRACT An 18-year old, phenotypically female individual was examined for primary amenorrhea. Three months before her referral, the patient underwent surgery and a pelvic mass was removed. The physical examination revealed normal female external genitalia, normal breast development, sparse pubic hair and absence of axillary hair. The gynecological examination revealed a short blind vagina pouch and absence of cervix and uterus. Serum testosterone and dihydrotestosterone levels were very high. Karyotype was that of a normal male (46,XY). The transabdominal ultrasound, computed tomography (CT) and Magnetic resonance imaging (MRI) showed absence of uterus and fallopian tubes and revealed testis-like gonads located at the internal opening of the inguinal canal bilaterally. Bilateral gonadectomy was subsequently performed. The pathology report was that of hamartomatous testes and associated paratesticular leiomyoma. The clinical, laboratory, imaging, genetic and histological findings confirmed the diagnosis of complete androgen insensitivity syndrome. DNA analysis revealed a R831X mutation in exon 7 of the androgen receptor gene. A Sertoli-cell dynamic test showed elevated basal serum inhibin-B and anti-Müllerian hormone levels without further rise following FSH stimulation. The patient was started on hormone replacement therapy with conjugated estrogens. Complete androgen insensitivity syndrome must be considered in any case of primary amenorrhea. Gonadectomy must be planned to eliminate the risk of gonadal malignancy