Mark James Krzmarzick

We present draft genomes of Citrobacter freundii strains isolated from a model wastewater treatment plant seeded with sludge from Stillwater, Oklahoma. Analysis suggests that the Stillwater strains are related to human isolates from China and the UK. All strains also possess antimicrobial resistance genes, highlighting the potential public health implications.

Commercially available Unmanned Surface Vehicles (USVs) in the market are expensive, and the software used for automating navigation and bathymetry mapping are typically proprietary. Large scale collection of water quantity and quality data requires dynamic in-situ sensing approaches with open-source software for user flexibility. This manuscript presents an open-source, economic, and efficient USV platform for in-situ depth sensing to perform hydrographic surveys in freshwater bodies with capabilities to explore inaccessible shallow regions by humans. The USV components cost less than $3,000. The application of the USV for a bathymetric survey was performed at Horse Creek Cove at Grand Lake O’ the Cherokees. These results find that an estimated 43,000 m3 of sediment accumulated in this cove over a time span of eleven years between a 2009 manual survey and our 2020 analysis with the USV. This USV platform provides an advantageous method for widescale adoption and use manual methods of mapping of bathymetry and potentially other water quality parameters.

Harmful algal blooms (HABs) diminish the utility of reservoirs for drinking water supply, irrigation, recreation, and ecosystem service provision. HABs decrease water quality and are a significant health concern in surface water bodies. Near real‐time monitoring of HABs in reservoirs and small water bodies is essential to understand the dynamics of turbidity and HAB formation. This study uses satellite imagery to remotely sense chlorophyll‐a concentrations (chl‐a), phycocyanin concentrations, and turbidity in two reservoirs, the Grand Lake O′ the Cherokees and Hudson Reservoir, OK, USA, to develop a tool for near real‐time monitoring of HABs. Landsat‐8 and Sentinel‐2 imagery from 2013 to 2017 and from 2015 to 2020 were used to train and test three different models that include multiple regression, support vector regression (SVR), and random forest regression (RFR). Performance was assessed by comparing the three models to estimate chl‐a, phycocyanin, and turbidity. The results showed that RFR achieved the best performance, with R² values of 0.75, 0.82, and 0.79 for chl‐a, turbidity, and phycocyanin, while multiple regression had R² values of 0.29, 0.51, and 0.46 and SVR had R² values of 0.58, 0.62, and 0.61 on the testing datasets, respectively. This paper examines the potential of the developed open‐source satellite remote sensing tool for monitoring reservoirs in Oklahoma to assess spatial and temporal variations in surface water quality.

Co-contamination of hydrocarbons with heavy metals in soils often complicates and hinders bioremediation. A comprehensive characterization of site-specific degraders at contaminated sites can help determine if in situ bioremediation processes are sufficient. This study aimed to identify differences in benzene and toluene degradation rates and the microbial communities enriched under aerobic conditions when different concentrations of Cd and Pb are introduced. Microcosms were used to study the degradation of 0.23 mM benzene or 0.19 mM toluene under various concentrations of Pb (up to 240 µM) and Cd (up to 440 µM). Soil collected from a stormwater retention basin receiving runoff from a large parking lot was utilized to seed the microcosms. The hydrocarbon degradation time and rates were measured. After further rounds of amendment and degradation of benzene and toluene, 16S rRNA gene amplicon sequencing and quantitative PCR were used to ascertain the microbial communities enriched under the various concentrations of the heavy metals. The initial degradation time for toluene and benzene was 7 to 9 days and 10 to 13 days, respectively. Degradation rates were similar for each hydrocarbon despite the concentration and presence of metal co-contaminant, however, the enriched microbial communities under each condition differed. Microcosms without metal co-contaminant contained a diversity of putative benzene and toluene degrading bacteria. Cd strongly reduced the richness of the microbial communities. With higher levels of heavy metals, genera such as Ralstonia, Cupriavidus, Azoarcus, and Rhodococcus became more dominant under various conditions. The study finds that highly efficient benzene- and toluene-degrading consortia can develop under variations of heavy metal co-contamination, but the consortia are dependent on the heavy metal type and concentrations.

Irrigation water is required for increased crop yield and production to satisfy global food demand. However, irrigation also has negative impacts, including the production of greenhouse gas (GHG) emissions from groundwater pumping. To lessen this environmental problem, management methods that minimize agricultural GHG emissions from groundwater pumping should be identified. This work aims to compare measures that decrease agricultural groundwater withdrawal GHG emissions. A comparison among different energy supply and demand management choices for groundwater pumping was made to identify the most effective measure. Results indicated that the best agricultural groundwater pumping management practices are affected by the type of pump (e.g., electricity, natural gas) and source of pumping energy (e.g., coal, natural gas, oil, wind, solar). Due to their higher operational pump efficiency (OPE), electric pumps consume less energy than natural gas pumps to extract an equal volume of groundwater under similar conditions. Nevertheless, natural gas pumps produce less GHG emissions than electric pumps using the U.S. Central and Southern Pains electricity mix. Hence, groundwater pumping energy demand management through improving the OPE)of natural gas pumps will save more GHG emissions (7600 kg CO₂-eq year^− 1) than switching to electric pumps using the electricity mix applied to this study (2800 kg CO₂-eq year^− 1). Additionally, switching to cleaner energy sources (wind and solar) can save significantly higher amounts of carbon than just improving OPE. This analysis can guide policymakers and individuals to assist in meeting global GHG emission reduction goals and targets while satisfying increasing food demand.

Co-contamination of hydrocarbons with heavy metals in soils often complicates and hinders bioremediation. A comprehensive characterization of site-specific degraders at contaminated sites can help determine if in situ bioremediation processes are sufficient. This study aimed to identify differences in benzene and toluene degradation rates and the microbial communities enriched under aerobic conditions when different concentrations of Cd and Pb are introduced. Microcosms were used to study the degradation of 0.23 mM benzene or 0.19 mM toluene under various concentrations of Pb (up to 240 µM) and Cd (up to 440 µM). Soil collected from a stormwater retention basin receiving runoff from a large parking lot was utilized to seed the microcosms. The hydrocarbon degradation time and rates were measured. After further rounds of amendment and degradation of benzene and toluene, 16S rRNA gene amplicon sequencing and quantitative PCR were used to ascertain the microbial communities enriched under the various concentrations of the heavy metals. The initial degradation time for toluene and benzene was 7 to 9 days and 10 to 13 days, respectively. Degradation rates were similar for each hydrocarbon despite the concentration and presence of metal co-contaminant, however, the enriched microbial communities under each condition differed. Microcosms without metal co-contaminant contained a diversity of putative benzene and toluene degrading bacteria. Cd strongly reduced the richness of the microbial communities. With higher levels of heavy metals, genera such as Ralstonia, Cupriavidus, Azoarcus, and Rhodococcus became more dominant under various conditions. The study finds that highly efficient benzene- and toluene-degrading consortia can develop under variations of heavy metal co-contamination, but the consortia are dependent on the heavy metal type and concentrations.

Insensitive munitions compounds (IMCs) are emerging nitroaromatic contaminants developed by the military as safer-to-handle alternatives to conventional explosives. Biotransformation of nitroaromatics via microbial respiration has only been reported for a limited number of substrates. Important soil microorganisms can respire natural organic matter (NOM) by reducing its quinone moieties to hydroquinones. Thus, we investigated the NOM respiration combined with the abiotic reduction of nitroaromatics by the hydroquinones formed. First, we established nitroaromatic concentration ranges that were nontoxic to the quinone respiration. Then, an enrichment culture dominated by Geobacter anodireducens could indirectly reduce a broad array of nitroaromatics by first respiring NOM components or the NOM surrogate anthraquinone-2,6-disulfonate (AQDS). Without quinones, no nitroaromatic tested was reduced except for the IMC 3-nitro-1,2,4-triazol-5-one (NTO). Thus, the quinone respiration expanded the spectrum of nitroaromatics susceptible to transformation. The system functioned with very low quinone concentrations because NOM was recycled by the nitroaromatic reduction. A metatranscriptomic analysis demonstrated that the microorganisms obtained energy from quinone or NTO reduction since respiratory genes were upregulated when AQDS or NTO was the electron acceptor. The results indicated microbial NOM respiration sustained by the nitroaromatic-dependent cycling of quinones. This process can be applied as a nitroaromatic remediation strategy, provided that a quinone pool is available for microorganisms.