<p> The processes that generated the distinctive landscape of the Iowa Erosion Surface (IES) of northeastern Iowa have been debated for over a century. A number of researchers have concluded that the IES experienced a periglacial environment and was underlain by continuous permafrost during the last glacial maximum. Ubiquitous throughout the IES is a stone zone that lies 60-100cm below the surface. Several explanations for the genesis of the stone zone have been proposed, including a lag concentrate, biomantle processes, and cryogenesis. We utilized a combination of coring and trenching, ground penetrating radar and resistivity to investigate the 3D distribution of the stone zone, overlying "pedisediment" and the underlying contact with dense till across a 100m2 area on a typical IES hillslope in east-central Iowa . Our preliminary results indicate that the stone zone occurs in the basal few decimeters of pedisediment that rests uncomformably and abruptly on eroded, dense till. Ice wedge casts extend from the stone zone into the underlying till. The depth of the stone zone below the modern surface increases downslope and the stone zone dissipates and eventually is replaced by relatively thick loamy sand beneath the footslope. These relationships argue against the stone zone being of biogenic origin. The occurrence of ice wedge casts associated with the stone zone and systematic changes in the thickness and texture of the pedisediment suggest to us that stone zone on the IES was formed by a combination of cryogenic and active zone erosive processes during the full glacial period.</p>

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 0861. Adviser: Robert J. M. Hudson. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-05, Section: B, page: 2678. Adviser: Emerson D. Nafziger. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (doctoral)--Göteborg Universitet, 2006. / Added t.p. with thesis statement inserted. Includes bibliographical references.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3245. Adviser: Michelle Wander. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Macropore flow is a gravity-driven phenomenon that exhibits high contamination risk for surface and shallow groundwater. In order to address the necessity of having reliable and tangible indicators of macropore flow incidence, this research is an extensive data exploration that uncovers potential regional macropore flow incidence indicators that are synthesized as hypotheses for future research. CART-based regression trees are used to uncover significant relationships among soil physical properties, management regimes, field saturated hydraulic conductivity, saturated soil air-entry tensions and earthworm biomass. All of the modeling is based on field-measured data. Prediction scenarios are established in order to develop potential regional indicators of field saturated hydraulic conductivity (Kfs), soil saturated air-entry tension (AEV), and earthworm biomass. The magnitude, range, and pattern of variability of soil water infiltrations are controlled primarily by the well-developed and stable soil structure at the field scale, rather than by texture, organic carbon or surface topography, as classical pedotransfer functions suggest. Tillage is influential for the estimation of all targeted variables. Conventional tillage is associated with rapid shallow infiltration rates and lower air entry tensions both in the cultivation layer and below. Absence of tillage is found to be beneficial for earthworm communities as sampled biomass is greater on no-till field sites. The strong correlations between Kfs and AEV demonstrate good prediction potential but because of their intrinsic spatial and temporal variability, their utility as regional macropore flow indicators is questionable.

Measurement of water is important in soil since this is the medium in which soil activity takes place. Pressure-saturation curves show the extent of liquid retention in the soil porous medium at different tensions during drainage and sorption (hysteresis). Measurement of soil moisture in the laboratory is time-consuming, labor-intensive and expensive. In this study, three methods for measuring pressure-saturation curves were employed, Hanging Water Column (HWC), Differential Pressure Transducer-Imbibition, and Differential Pressure Transducer-Natural. The standard HWC is compared to the other two methods which employ external manometer pressure and differential pressure transducers. Hysteresis pressure-saturation curves were determined for three liquids (water, 50% ethanol and 100% ethanol), in a homogeneous Vinton fine sand. Data was fit to the van Genuchten and Brooks Corey models and liquid capillary numbers are compared. Prediction of desorption pressure-saturation curves from water curves using relative surface tension ratios is discussed and prediction of sorption curves using relative A parameters for the drying and wetting curves. Scanning curves were scaled from the main drying and wetting curves. The capillary number-pore water velocity combination function could be another useful relationship for pressure-saturation curves. Overall, the differential pressure transducer methods were found superior to the HWC because time consumption was reduced by more than 50% yet the results obtained were of comparable accuracy. Pressure-saturation curves for other liquids may be predicted by scaling pressure and van Genuchten alpha parameter with relative surface tension ratios. Hence, hysteresis curves can be obtained faster and the main disadvantages of time-consumption, labor and cost are eliminated. In addition, handling of hazardous liquids in the laboratory is minimized which is important because understanding retention of hazardous chemicals in soil is a prerequisite to achieving remediation of residual contamination. Functional relationship between the residual nonwetting phase and the capillary number or viscosity to surface tension ratio is briefly discussed.

The occurrence and disinfectant effectiveness for pathogens which are known or thought to be important in waterborne disease was evaluated. In the first study, the occurrence of human pathogenic microsporidia, Giardia cysts and Cryptosporidium oocysts in surface waters used for the irrigation of vegetable crops was determined. Twenty-eight percent of the irrigation water samples tested positive for microsporidia, 60% positive for Giardia cysts and 36% positive for Cryptosporidium oocysts. Concentrations of Giardia cysts and Cryptosporidium oocysts detected in water samples collected in Central America compared to the United States were 559 cysts and 227 oocysts, and 25 cysts and < 19 oocysts per 100 L, respectively. The presence of human pathogenic parasites in irrigation waters used for production of crops traditionally consumed raw suggests that there may be a risk of infection to consumers who come in contact with or consume these products. In the other investigations, the effectiveness of UV light and free chlorine on the inactivation of feline calicivirus (FCV) and enteric adenovirus type 40 (AD40) was assessed and compared to model viruses, poliovirus type 1 (PV-1) and coliphage MS-2. FCV was used as a model for members of the "Norwalk like virus" (NLV) group. The UV doses required to achieve 99% inactivation of AD40, coliphage MS-2 and FCV in buffered demand free (BDF) water were 108.6, 58.5 and 16.8 mWs/cm², respectively. For chlorine reactions, higher Ct values for high pH and low temperature conditions was observed for FCV and AD40. Both viruses were more resistant to chlorine than the well-studied PV-1. FCV and AD40 were inactivated rapidly by ∼0.5 mg/L free chlorine by ≥4.00- and ≥2.54-logs at pH 6 and 5°C whereas, PV-1 was not inactivated by 4.04-logs until 10 min contact time. Experiments conducted with aggregated FCV and PV-1 and experiments conducted in treated groundwater had slower inactivation kinetics than dispersed viral suspensions in BDF water. The high disinfectant decay rate of some experiments was most likely due to the decrease in chlorine concentration throughout the experiment. However, low disinfectant decay rates of the AD40 experiments suggest that aggregation or clumping of the viruses may have occurred. The results of these studies provide information on the effectiveness of two common water treatment disinfectants in waters with different physical and chemical qualities. The results of this study may provide a basis for the establishment of guidelines for proficient application in drinking water treatment.

Laser light scattering (LLS) is an alternate method for determining soil particle size. Since the majority of information on particle size analysis has traditionally been derived from sedimentation methods, it is important to be able to draw a relationship between these two methods. Twenty four soil samples from a set of 214 samples analyzed by LLS were selected and also analyzed using sedimentation techniques. Particle size percentages were obtained in five different size ranges and then these two techniques were compared. Linear regression equations were developed that convert numbers obtained from the LLS method to a pipette analysis equivalent. This data was then utilized to eliminate the variation of soil moisture due to soil texture to obtain a moisture content independent of soil moisture. This "adjusted moisture" was displayed on a geographic information system to locate areas in the soil profile where soil moisture is relatively high. The high "adjusted moisture" contents occurred predominately below 2.44 meters (8 ft.) depths suggesting that the pre-irrigation applied to this soil reached this depth.

<p> Soil health assessment uses a combination of potential indicators affecting soil processes to comprehensively monitor soil change, caused by cropping systems and soil management. The objectives of the study were to assess the effects of selected cropping systems, soil management and landscape slope positions on the soil health characteristics of the Sanborn Field long-term experimental study in Columbia, Missouri, United States. Soil samples were collected on each of four dates over two years (8^th May 2014, 4^th September 2014, 1^st April 2016, and 18^th August 2016) from selected plots to address each objective, and these time samples were used as replications. Soil physical, chemical, and biological characteristics were analyzed in the laboratory for these samples to assess soil health using the Cornell Comprehensive Assessment of Soil Health (CASH) method. To assess soil health in this study, soil health scoring was determined used R-studio version 1.1.149 to relate the interaction of cropping systems, soil management, and slope positions. Most soil resources on Sanborn Field are a poorly-drained claypan soil classified as a Mexico silt loam (fine, smectitic, mesic Vertic Epiaqualf). In addition, soil samples collected from Tucker Prairie was used as a proxy for the original state of Sanborn Field soils. The first study was conducted to evaluate the effects of long-term cropping systems on soil health properties. The results from the characterization indicated that continuous timothy (<i>Phleum pretense</i> L.) and warm season grass treatments were classified with very high soil health scores, and the lowest score was found for continuous corn (<i>Zea mays</i> L.). In addition, results showed strong positive linear associations between soil organic carbon, total nitrogen, potentially mineralizable nitrogen, active carbon, microbial biomass, and water stable aggregates; while a strong negative linear correlation existed between each of these properties and bulk density. The second study was conducted to evaluate the effects of long-term annual applications of no fertilizer, full fertilizer, and manure on soil health measurements of selected cropping systems. Different cropping systems, including continuous corn, continuous wheat (<i>Triticum aestivum</i> L.), corn-wheat-red clover (<i>Trifolium pretense</i> L.) rotation, and corn-soybean (<i>Glycine max</i> L.)-wheat rotation treatments were used in this study. Results showed that annual dairy cow (<i>Bos Taurus </i>) manure applications had the greatest effect on all soil health indicators and had the largest overall soil health score compared to full fertility and no fertilizer treatments. Moreover, continuous wheat with manure application presented the best combination of effects on soil properties with the largest score for most soil health indicators and an overall health score of 82 out of 100 classified as very high which is the best. The last study evaluated the effects of landscape slope positions on soil health properties of the long-term experiment. Results showed that the summit position had the highest overall soil health score while the lowest score was found on the shoulder position. However, there were no significant differences along the transect slope for water-stable aggregates and bulk density. There were significant differences along the transect for the biological properties such as soil organic carbon, active carbon, potentially mineralizable nitrogen, and microbial biomass. Results of this study illustrate the effect of selected variables on soil health and provide the recent addition of using biological characteristics to account for soil health properties. It is important to remember that this study of the long-term Sanborn Field experiment is just for a small-sized plot area. Future studies of soil management effects on soil health need to account for their own field conditions and their own unique environment.</p><p>