Evaluation of prairie grasses for reducing the environmental impact of herbicide contamination

The primary goal of this dissertation was to evaluate the use of prairie grasses for reducing the environmental impact of herbicides. Studies included: use of prairie grasses as a phytoremediation tool for contaminated soil; comparison of grass species for use in vegetative buffer strips; fate of 14C-pendimethalin in vegetated and unvegetated soil; and environmental hazards of pendimethalin contaminated soil.;Throughout this dissertation, evidence was presented that prairie grasses can increase the dissipation rate of herbicides. In one study, 78% less metolachlor and 39% less pendimethalin remaining in vegetated treatments as compared to unvegetated treatments. In a separate study, the presence of nearly all grasses tested, but specifically the prairie grasses, resulted in greater degradation of atrazine and metolachlor in rhizosphere soil as compared to unvegetated soil. Phytoremediation mechanisms likely involve plant uptake and increased soil degradation.;Prairie grasses were also shown to decrease movement of pesticides both through the soil column and into biota, thus serving as a phytostabilization agent. Nearly 20% of the metolachlor in unvegetated columns leached out of the bottom of the column after application of an artificial rain event , while only 5% leached out of vegetated columns. It was also shown that even though vegetated columns allowed infiltration of artificial surface runoff at a much faster rate, the total amount of herbicide moving through the column was held constant, and the amount leaching through after initial applications of herbicide was reduced. Additionally, the presence of vegetation decreased the bioavailability of pendimethalin as measured by earthworm uptake and toxicity to lettuce seedlings.;Pendimethalin residues are very persistent and are likely to be present at some level following bioremediation. Therefore, a hazard evaluation was performed to determine tolerable soil concentrations of pendimethalin that could remain without risk to the biota in the environment. Even low levels of pendimethalin, 10mg/kg or less, were shown to have toxic effects on plants and earthworms, and concentrations as low as 30 mg/kg were shown to have potentially toxic effects through trophic transfer. Thus remediation would need to continue until pendimethalin is reduced to field application levels (10 mg/kg) or less

Growth inhibition of UV filters on the freshwater microalga Scenedesmus acutus

As the use of personal care products with organic ultraviolet (UV) filters are increasing, so is the exposure risk of these compounds to aquatic ecosystems. This study focuses on the inhibition growth effect of four common UV filters on the freshwater microalgae, Scenedesmus acutus. Fluorescence of chlorophyll a was used as a measure of growth during a 96-h exposure period, and growth inhibition was utilized as the endpoint. All UV filters inhibited growth with increasing concentration, except for avobenzone and octisalate, which did not decrease reproduction at any treatment level up to water solubility. Lowest observed effect concentrations for atrazine, homosalate, and oxybenzone were 117 μg/L, 100 μg/L, and 1875 μg/L, respectively. Homosalate was the most toxic UV filter followed by oxybenzone with avobenzone and octisalate likely to be not toxic to S. acutus. These results indicate that toxicity to freshwater algae is not likely at environmentally relevant concentrations. However, further research should consider the impact of UV light on toxicity.Lew Wentz FoundationIntegrative Biolog

Water Entry of Spheres at Various Contact Angles

It is well known that the water entry of a sphere causes cavity formation above a critical impact velocity as a function of the solid-liquid contact angle (Duez et al. 2007). Using a rough sphere with a contact angle of 120◦, Aristoff & Bush (2009) showed that there are four different cavity shapes dependent on the Bond and Weber numbers (i.e., quasi-static, shallow, deep and surface). We experimentally alter the Bond number, Weber number and contact angle of smooth spheres and find two key additions to the literature: 1) Cavity shape also depends on the contact angle; 2) the absence of a splash crown at low Weber number results in cavity formation below the predicted critical velocity. In addition, we find an alternate scaling for the Bond and Weber numbers that predicts cavity shapes for various impacting bodies (e.g., spheres, multi-droplet streams and jets) on the same regime diagram, thus, merging the often separated studies of solid-liquid and liquid-liquid impact in the literature

Water Entry of a Simple Harmonic Oscillator

When a blunt body impacts an air-water interface, large hydrodynamic forces often arise, a phenomenon many of us have unfortunately experienced in a failed dive or "belly flop." Beyond assessing risk to biological divers, an understanding and methods for remediation of such slamming forces are critical to the design of numerous engineered naval and aerospace structures. Herein we systematically investigate the role of impactor elasticity on the resultant structural loads in perhaps the simplest possible scenario: the water entry of a simple harmonic oscillator. Contrary to conventional intuition, we find that "softening" the impactor does not always reduce the peak impact force, but may also increase the force as compared to a fully rigid counterpart. Through our combined experimental and theoretical investigation, we demonstrate that the transition from force reduction to force amplification is delineated by a critical "hydroelastic" factor that relates the hydrodynamic and elastic timescales of the problem

Persistence, Mobility, and Bioavailability of Pendimethalin and Trifluralin in Soil

Pendimethalin and trifluralin are current-use pesticides that have been previously reported as persistent, bioaccumulative, and toxic. In the studies presented here, dissipation of aged and fresh residues of pendimethalin and trifluralin were evaluated in soil, as well as the bioavailability of residues to earthworms and the movement of pendimethalin in a soil column. In a separate study, pond water receiving runoff from a golf course was measured for the presence of pendimethalin. Dissipation measurements of pendimethalin and trifluralin in soil indicated very slow dissipation with 40-60% of the compounds extractable at 1026 days after the first measurement. In a second study, dissipation of pendimethalin was more rapid, however more than 30% was present after 310 days of soil treatment. Biovailability, as measured by earthworm biological accumulation factors, was reduced over time. Mobility of pendimethalin was very limited. Almost no downward movement was measured in the column study, and no detectable levels were found in runoff from turf grass

Detoxification of Pesticide Residues in Soil Using Phytoremediation

During the past few years, we have conducted a series of experiments to investigate the potential of using plants as tools for the remediation of pesticide-contaminated soil. We have demonstrated that a blend of prairie grasses increases dissipation rates of several pesticides including metolachlor, trifluralin, and pendimethalin. However, in other studies, mulberry trees were not shown to influence pesticide dissipation. Additional studies have demonstrated that metolachlor movement in the soil column may be reduced by the presence of prairie grasses, bioavailability of dinitroanaline herbicides may be reduced during phytoremediation, and soil and leachate from remediated soil may have less toxicity than expected. Current studies within our laboratory are being conducted to determine the role of prairie grass blends in the phytoremediation procedure as compared to individual species and the role of plant uptake of pesticides in the phytoremediation process

Fluted Films

This paper is associated with a poster winner of a 2017 APS/DFD Milton van Dyke Award for work presented at the DFD Gallery of Fluid Motion. The original poster is available from the Gallery of Fluid Motion, https://doi.org/10.1103/APS.DFD.2017.GFM.P003