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Mutations in human mitochondrial DNA (mtDNA) can cause mitochondrial disease and have been associated with neurodegenerative disorders, cancer, diabetes and aging. Yet our progress toward delineating the precise contributions of mtDNA mutations to these conditions is impeded by the limited availability of faithful transmitochondrial animal models. Here, we report a method for the isolation of mutations in mouse mtDNA and its implementation for the generation of a collection of over 150 cell lines suitable for the production of transmitochondrial mice. This method is based on the limited mutagenesis of mtDNA by proofreading-deficient DNA-polymerase γ followed by segregation of the resulting highly heteroplasmic mtDNA population by means of intracellular cloning. Among generated cell lines, we identify nine which carry mutations affecting the same amino acid or nucleotide positions as in human disease, including a mutation in the ND4 gene responsible for 70% of Leber Hereditary Optic Neuropathies (LHON). Similar to their human counterparts, cybrids carrying the homoplasmic mouse LHON mutation demonstrated reduced respiration, reduced ATP content and elevated production of mitochondrial reactive oxygen species (ROS). The generated resource of mouse mtDNA mutants will be useful both in modeling human mitochondrial disease and in understanding the mechanisms of ROS production mediated by mutations in mtDNA.

Sediment remains one of the most commonly occurring pollutants affecting the U.S.’s water bodies, as identified by the United States Environmental Protection Agency (USEPA) ( 1). Construction activities largely accelerate soil erosion and subsequent sediment deposition. The National Pollutant Discharge Elimination System Construction General Permit requires construction operators to implement erosion and sediment control (E&SC) plans to minimize downstream implications from sediment-laden discharge. However, E&SC practices are often designed from “rules of thumb” and lack scientific, performance-based evidence in their design and implementation. The Auburn University Stormwater Research Facility (AU-SRF), previously the Auburn University Erosion and Sediment Control Testing Facility (AU-ESCTF), is an outdoor research center dedicated to evaluating E&SC practices and products commonly used on highway construction projects. Large-scale test apparatuses and methods at AU-SRF are designed to mimic construction site conditions, including rainfall, flow rates, topography, and soil characteristics, to evaluate existing and novel E&SC practices. Since its inception in 2008, AU-SRF has provided small-, medium-, and large-scale testing evaluations for numerous Departments of Transportation and product manufacturers. Findings from controlled testing have continued to inform the selection, design, implementation, and maintenance of E&SC practices used on construction sites and protect downstream waters and infrastructure. In the first decade, AU-SRF has directed 13 research projects and produced more than 30 peer-reviewed publications and 100 professional presentations. As AU-SRF grows into its second decade and efforts reach outside of the southeastern region, the mission to advance knowledge through E&SC research and development, product evaluation, and training remains constant. This review synthesizes the research produced from large-scale testing at AU-SRF to date and presents ongoing projects.

Construction-related ground-disturbing activities leave exposed land susceptible to soil loss and increase the risk of polluting adjacent waterbodies with sediment-laden discharge. State and federal regulations require stormwater pollution prevention plans to be implemented during construction to mitigate the impact of stormwater runoff. Areas prone to soil loss can be identified early in site planning using soil loss modeling. Identification of these critical areas could influence the design and placement of erosion and sediment control practices. The Revised Universal Soil Loss Equation (RUSLE) can be applied to estimate the soil loss on construction sites in tonnes per Ha per year (tons/acre/year) by considering factors of rainfall erosivity, soil erodibility, length of slope, erosion control, and sediment control. This study integrates geographic information system (GIS) with RUSLE to create soil loss models for residential, commercial, and highway construction scenarios in the contiguous U.S.A. These three construction types were modeled in various locations throughout the country to assess erosive risk. Soil loss outputs were categorized into five risk tiers ranging from very low to very high. Southeastern states had the highest estimated soil loss during residential, commercial, and highway construction, reaching rates of 1,464, 706, and 1,302 tonnes per Ha per year (653, 315, and 581 tons/acre/year), respectively. This study provides a customizable model for any site-specific slope-length factor outside of the three construction scenarios modeled. Integration of GIS provides a unique opportunity to apply RUSLE across a larger landscape. The presented macro-scale data can be used for the design of erosion and sediment control practices.

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Flocculants provide an innovative solution for managing construction stormwater runoff with their efficiency in reducing turbidity in the effluent. With proper application and dosage, these chemicals improve the performance of sediment control practices in capturing fine-sized soil particles. Flocculants function by providing electromagnetic charges to attract soil particles into large molecular bridges of flocs. Following this process, suspended particle removal can be achieved through gravitational forces. Despite the benefits of using flocculants, their implementation may create a potential risk of polluting downstream waterbodies and harming aquatic life in case of a high residual concentration in discharge. Determining residual concentrations is challenging for practitioners because of a lack of field applicable testing methods that work across a variety of flocculant types. This study developed a field applicable methodology for detecting residual flocculant concentrations by using settling velocity as an identifier of flocculant concentration. In total, 14 products comprised of polyacrylamide, sodium montmorillonite, chitosan, agricultural gypsum, and alum-based products were evaluated. Known flocculant concentrations ranging from 0% to 30% of the manufacturer’s recommended dosage, were mixed with a fine soil passing through No. 200 sieve and allowed to settle in a graduated cylinder to record the settling velocity. Regression analysis was conducted on the experimental data to develop concentration versus settling velocity relationships which indicated that more than 90% of known concentration values are dependent on the settling velocity. The study provides a framework for practitioners to identify residual flocculant concentrations in field conditions by relating settling velocity with chemical concentrations.

Stormwater regulations require erosion and sediment control practices to be implemented during construction to prevent discharging polluted water offsite and mitigate downstream effects. Sediment basins are a common sediment control practice used to detain suspended sediment from stormwater runoff by providing residence time and storage to promote gravitational settling. Sediment basin design, and thus pollutant removal efficiency, vary regionally due to local design standards and preferences. Traditional sediment basins require a dedicated excavation pond with various mechanisms for dewatering. This manuscript presents the results of a case study where two sediment basin systems were created within a conveyance channel by constructing an earthen berm across the channel to detain sediment-laden stormwater. A dewatering riser pipe was routed through the earthen berm to provide primary dewatering. The in-channel sediment basin was constructed with a 3% slope and a 10 ft. bottom width. The first system consisted of one basin created by a single earthen berm damming sediment-laden runoff, whereas the second system included two earthen berms, creating two in-channel sediment basins in series. The two systems were independently field monitored during Highway U.S. 30 construction in Tama County, Iowa. Prior to this field campaign, there was no documented performance data on the in-channel sediment basin design. Field monitoring was conducted by deploying a rain gauge and automated water samplers positioned at the inflow and discharge points of a (a) single basin and (b) two basins in series within a roadside channel. Instrumentation was completed on in situ basins constructed per Iowa Department of Transportation standards before the start of site earthwork. During the monitoring period, no maintenance or dredging was recorded. The retrieved water samples were taken from the monitored basins and analyzed for turbidity. Inflow turbidities often reached magnitudes up to the 103 NTU. Water quality samples from the basin indicated negligible turbidity reduction after residence. During monitoring, there were several occurrences where discharge turbidity was higher than inflow turbidity, indicating that the basin was serving as a sediment source. This manuscript describes the in-channel sediment basin design, field-monitoring site and sampling regimen, and discusses potential design technique and component improvements to achieve enhanced performance.