The Specific Surface Area Values for Iowa Tills

Specific surface area is a property used by earth scientists to estimate the proportion of expandable clay minerals in soils. In this study, specific surface area method is shown to compare favorably with standard clay mineralogical techniques in determining gross differences in expandable clay mineral content in tills. The results of over 100 measurements on till samples from Iowa indicate undifferentiated pre-Illinoian tills from southern and southwestern Iowa have the highest specific surface area values of Iowa tills (ranging from nearly 100 to greater than 150 m2/g) and Wisconsinan Dows Formation tills have the lowest average specific surface area values (approximately 50 to 80 m2/g). Pre-Illinoian tills from eastern Iowa have significantly lower average specific surface area values than undifferentiated pre-Illinoian tills collected from southern and southwestern Iowa. Specific surface area determinations proved useful in distinguishing between pre-Illinoian till units at the formation level in eastern Iowa. The use of this property at the formation and sub-formation level in Wisconsinan tills is less diagnostic. Limited specific surface data exist for Illinoian tills, which appear to have clay mineral compositions intermediate between those of undifferentiated pre-Illinoian tills from southern and southwestern Iowa and Wisconsinan tills

Hydrogeology of the Devonian-Silurian Carbonate Aquifer, Northern Cedar Rapids, Iowa

The hydrogeology of the Devonian-Silurian carbonate aquifer was investigated at a hazardous waste site in northern Cedar Rapids, Iowa. Data collected at the project site included bedrock cores, specific capacity measurements in discrete packer intervals and monitoring wells, hydraulic-head measurements and groundwater samples collected from select Devonian and Silurian wells

The Pleistocene Glacial Record at Two Quarries in Decatur County, Iowa

The Pleistocene stratigraphy and sedimentology of two quarry exposures near Grand River and Decatur City in Decatur County, Iowa document a sequence of Pleistocene sediments overlying striated Pennsylvanian limestone which represent at least two pre-Illinoian glacial advances into the ancestral Grand River valley. Two pre-Illinoian diarnictons separated by a clast pavement were observed at the Decatur City quarry; a single diarnicton was present at the Grand River quarry. At both quarries, the diarnictons exhibit comparable lithologic properties and are genetically interpreted as basal tills. The pre-Illinoian tills are tentatively correlated with the Alburnett Formation in eastern Iowa, primarily on the basis of clay mineralogy data. Fluvial erosional and depositional processes succeeded till deposition at both quarry sites. The tills are overlain by a fining-upward fluvial sequence upon which a well developed Yarmouth-Sangamon paleosol is developed. Sangamon Soil developed upon a pebbly diarnicton overlies the fluvial sediments. The pebbly diarnicton probably originated as colluvium from pre-Illinoian tills at higher landscape positions during late Sangamonian pedimentation. Lastly, periglacial conditions during mid-to-late Wisconsinan time resulted in multiple episodes of loess deposition corresponding to, in ascending order, the Pisgah Formation, Farmdale Soil and Peoria Loess, all Wisconsinan stratigraphic units

A Tale of Three Watersheds: Nonpoint Source Pollution and Conservation Practices across Iowa

Resource /Energy Economics and Policy, Q25,

Potential for managing pool levels in a flood-control reservoir to increase nitrate-nitrogen load reductions

Few strategies are available to reduce nitrate-nitrogen (NO3-N) loads at larger landscape scales, but flood control reservoirs are known to reduce riverine loads. In this study, we evaluated the potential to increase nitrogen (N) loss at Lake Red Rock, a large reservoir located in central Iowa, by evaluating the inundation of sediments deposited at the reservoir inflow. Sediment samples were collected at 51 locations in the lower delta region and analyzed for particle size and nutrient content. Nitrogen loss rates in delta sediments were determined from laboratory assays, and satellite imagery was used to develop a rating curve to quantify land area inundated within the delta. The daily mass of NO3-N reduced with delta inundation was estimated by applying the mean N 24-h loss rate (0.66 g N m2 day−1) by the area of inundation (m2). Results indicated that raising pool elevations to inundate more of the delta would result in greater N losses, ranging from 2 to 377 Mg per year. Potential N loss of 102 Mg achieved by increasing pool stage by 0.5 m would be equivalent to installing nearly 650 edge-of-field practices in the watershed. Although more work is needed to integrate with an existing environmental pool management plan, study results indicate that reservoir management could achieve N reductions at a novel landscape scale.This article is published as Schilling, K. E., Streeter, M. T., Anderson, E., Merryman, J., Isenhart, T., Arenas-Amado, A., & Theiling, C. (2024). Potential for managing pool levels in a flood-control reservoir to increase nitrate-nitrogen load reductions. Journal of Environmental Quality, 1–11. https://doi.org/10.1002/jeq2.20539. © 2024 The Authors.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited

Changes in lateral floodplain connectivity accompanying stream channel evolution: Implications for sediment and nutrient budgets

Floodplain storage commonly represents one of the largest sediment fluxes within sediment budgets. In watersheds responding to large scale disturbance, floodplain-channel lateral connectivity may change over time with progression of channel evolution and associated changes in channel geometry. In this study we investigated the effects of channel geometry change on floodplain inundation frequency and flux of suspended sediment (SS) and total phosphorus (TP) to floodplain storage within the 52.2 km2 Walnut Creek watershed (Iowa, USA) through a combination of 25 in-field channel cross section transects, hydraulic modeling (HEC-RAS), and stream gauging station-derived water quality and quantity data. Cross sectional area of the 25 in-field channel cross sections increased by a mean of 17% over the 16 year study period (1998–2014), and field data indicate a general trend of degradation and widening to be present along Walnut Creek\u27s main stem. Estimated stream discharge required to generate lateral overbank flow increased 15%, and floodplain inundation volume decreased by 37% over study duration. Estimated annual fluxes of SS and TP to floodplain storage decreased by 61 and 62% over study duration, respectively. The estimated reductions in flux to floodplain storage have potential to increase watershed export of SS and TP by 9 and 18%, respectively. Increased contributions to SS and TP export may continue as channel evolution progresses and floodplain storage opportunities continue to decline. In addition to loss of storage, higher discharges confined to the channel may have greater stream power, resulting in further enhancement of SS and TP export through accelerated bed and bank erosion. These increased contributions to watershed loads may mask SS and TP reductions achieved through edge of field practices, thus making it critical that stage and progression of channel evolution be taken into consideration when addressing sediment and phosphorus loading at the watershed scale

Lineage Abundance Estimation for SARS-CoV-2 in Wastewater Using Transcriptome Quantification Techniques

Effectively monitoring the spread of SARS-CoV-2 mutants is essential to efforts to counter the ongoing pandemic. Predicting lineage abundance from wastewater, however, is technically challenging. We show that by sequencing SARS-CoV-2 RNA in wastewater and applying algorithms initially used for transcriptome quantification, we can estimate lineage abundance in wastewater samples. We find high variability in signal among individual samples, but the overall trends match those observed from sequencing clinical samples. Thus, while clinical sequencing remains a more sensitive technique for population surveillance, wastewater sequencing can be used to monitor trends in mutant prevalence in situations where clinical sequencing is unavailable