Open Access. Powered by Scholars. Published by Universities.®

Life Sciences Commons

Open Access. Powered by Scholars. Published by Universities.®

Retrospective Theses and Dissertations

Environmental Sciences

Toxicology

Articles 1 - 13 of 13

Full-Text Articles in Life Sciences

Evaluation Of Prairie Grasses For Reducing The Environmental Impact Of Herbicide Contamination , Jason B. Belden Jan 2003

Evaluation Of Prairie Grasses For Reducing The Environmental Impact Of Herbicide Contamination , Jason B. Belden

Retrospective Theses and Dissertations

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 ...


Effects Of Environmental Estrogens On Reproductive Biology Of The Fathead Minnow , Robert Bruce Bringolf Jan 2002

Effects Of Environmental Estrogens On Reproductive Biology Of The Fathead Minnow , Robert Bruce Bringolf

Retrospective Theses and Dissertations

Since the early 1990s, environmental estrogens have been recognized as an important environmental threat. Wastewater of 10 aerated lagoon treatment facilities in Iowa was evaluated for estrogenic activity using a short-term caged fathead minnow exposure and a plasma vitellogenin (Vtg) assay. Plasma Vtg results indicated that wastewater entering the three-lagoon systems was estrogenic to male fish, but with serial passage through the lagoons, the estrogenic activity decreased to a level that was not sufficient to induce vitellogenesis. Wastewater retention time in the lagoons may have been a key treatment factor.;Feral fathead minnows captured at aerated lagoon wastewater treatment facilities ...


The Influence Of Vegetation, Microbial Inoculation, And Aging Of Pesticide Residues On The Degradation Of Atrazine And Metolachlor In Soils , Shaohan Zhao Jan 2001

The Influence Of Vegetation, Microbial Inoculation, And Aging Of Pesticide Residues On The Degradation Of Atrazine And Metolachlor In Soils , Shaohan Zhao

Retrospective Theses and Dissertations

The bacteria Agrobacterium radiobacter J14a and Pseudomonas sp. strain ADP and the enzyme atrazine chlorohydrolase all had a significant effect on the degradation of atrazine in Alpha soil, a soil with a low indigenous atrazine-mineralizing population. However, inoculation with J14a did not increase the atrazine degradation in Bravo soil, a soil with a high number of indigenous atrazine-mineralizing microorganisms. This suggests that the ability of J14a to enhance the degradation of atrazine is affected by the presence of indigenous atrazine-mineralizing microorganisms. Inoculation of Pseudomonas fluorescens UA5-40 did not enhance the transformation of metolachlor in either soil.;The ability of native ...


Toxicity Of Chlorpyrifos Adsorbed On Clay And Humic Acid To Larval Walleye , Todd Alan Phillips Jan 2000

Toxicity Of Chlorpyrifos Adsorbed On Clay And Humic Acid To Larval Walleye , Todd Alan Phillips

Retrospective Theses and Dissertations

Agricultural production poses one of the most serious threats to the continued ecological integrity of environmental systems and has been charged as the activity most responsible for loss of fish species in streams. Although all anthropogenic stressors affecting aquatic ecosystems have not been isolated, suspended solids, sediment, and pesticides are believed to be major factors. The objectives of this dissertation were to: (1) evaluate sources of variability in measuring cholinesterase activity, (2) determine the most sensitive life stage of walleye exposed to chlorpyrifos, (3) evaluate the bioavailability of chlorpyrifos adsorbed on humic acid (HA) and Panther Creek (PC) clay to ...


Factors Affecting Cholinesterase Activity In Aquatic Animals , Sheryl Linn Beauvais Jan 1997

Factors Affecting Cholinesterase Activity In Aquatic Animals , Sheryl Linn Beauvais

Retrospective Theses and Dissertations

Organophosphorus insecticides (OPs) are extensively used throughout the world to control crop pests. OPs are highly toxic to aquatic animals and can enter aquatic systems that drain agricultural watersheds, but assessment of an aquatic system's exposure to OPs is difficult as these compounds are non-persistent. Timing of sample collections and expense of analyses make direct monitoring of these insecticides problematic. A reliable and sensitive indicator of OP exposure and resulting toxic effects is needed to integrate across exposure events. A good candidate for the indicator is inhibition of cholinesterase (ChE) enzymes; OPs cause acute toxicity primarily through inhibition of ...


Enhanced Degradation Of Pesticide Wastes In Soil: Implications For Bioremediation Of Agrochemical Dealer Sites , Ellen Louise Kruger Jan 1996

Enhanced Degradation Of Pesticide Wastes In Soil: Implications For Bioremediation Of Agrochemical Dealer Sites , Ellen Louise Kruger

Retrospective Theses and Dissertations

The fate of atrazine and metolachlor, applied as a mixture, in soils taken from pesticide-contaminated sites (Alpha and Bravo) was determined in laboratory studies. Mineralization of metolachlor (less than 1%) in the Bravo sites was minimal after a 30-d. Degradation of metolachlor was greater in the Kochia scoparia rhizosphere soil. The amount of mineralization of atrazine at the Alpha site was as high as 62% of the applied 14C. A mass balance of the 14C applied revealed significant differences (p < 0.05) between the two soil types in soil bound residues, 14CO2, and the extractable organic fraction. The half-life for atrazine was significantly less in the rhizosphere soil (p < 0.05) with a half-life of 50 d compared to 193 d in the nonvegetated soils. A 14C-most-probable-number procedure was also carried out on soils from the pesticide-contaminated sites to determine specific atrazine and metolachlor degraders;To determine the influence of the presence of plants on the degradation of aged herbicide contaminants, vegetated and nonvegetated soil studies were conducted. The percent of applied 14C-atrazine remaining as atrazine in soil which was nonvegetated, or planted with Brassica napus or Kochia scoparia was 9.3, 6.5, and 4.2%, respectively. Combustion of plants revealed that 11% of the applied radioactivity was taken up in Kochia scoparia, while less than 1% was taken up in Brassica napus plants;A screening study was conducted to determine if soils obtained from several pesticide-contaminated sites had enhanced degradative capability to degrade four freshly applied herbicides. Atrazine mineralization was extensive in four of the soils. Minimal mineralization of pendimethalin, alachlor, and metolachlor was seen in this study. Atrazine, metolachlor, and trifluralin were applied in all possible combinations at a rate of 200 [mu]g/g each to soils exhibiting enhanced atrazine degradation in order to determine if higher concentrations and mixtures would inhibit degradation. Only the atrazine was radiolabeled. Rapid mineralization of atrazine occurred in all soil treatments, with 60% to 80% mineralization after 9 weeks;Deethylatrazine degradation was enhanced in soils which had received long-term exposure to atrazine compared with soils that had not received long-term atrazine exposure.


The Fate Of Methyl Bromide, Ethylene Glycol, And Propylene Glycol In Soil And Surface Water: Influence Of Soil Variables And Vegetation On Degradation And Offsite Movement , Patricia Jane Rice Jan 1996

The Fate Of Methyl Bromide, Ethylene Glycol, And Propylene Glycol In Soil And Surface Water: Influence Of Soil Variables And Vegetation On Degradation And Offsite Movement , Patricia Jane Rice

Retrospective Theses and Dissertations

Within the last few years methyl bromide (MeBr), ethylene glycol (EG), and propylene glycol (PG) have become environmental concerns due to their adverse impact on the environment. The purpose of our research was to study each compound within the framework of where and how they are environmental concerns by (1) investigating the influence of soil environmental variables on the degradation and mobility of MeBr in soil and (2) evaluating the use of vegetation to reduce soil infiltration and remediate soil and surface waters contaminated with aircraft deicing agents (EG, PG). Our research indicates MeBr rapidly volatilized from fumigated soil and ...


Evaluation Of Factors Affecting Avian Risk From Granular Pesticides , Tamara Rae Stafford Jan 1996

Evaluation Of Factors Affecting Avian Risk From Granular Pesticides , Tamara Rae Stafford

Retrospective Theses and Dissertations

The Environmental Protection Agency evaluates the risk of granular pesticides to birds using an LD50s/ft2-risk index. The index does not include avian response to granular characteristics, pesticide load per granule, or weather conditions, and it assumes that avian risk increases as granule availability increases. Fensulfothion was formulated on granular pesticide carriers to evaluate the effects of carrier type (silica, clay, and corncob), pesticide load per granule (1/2, 1/8, and 1/32 of the LD50), granule color (blue, white, and uncolored), and granule size (large and small) on captive house sparrows (Passer domesticus). In the initial experiments, silica ...


The Persistence, Degradation, And Mobility Of Metolachlor In Soil And The Fate Of Metolachlor And Atrazine In Surface Water, Surface Water/Sediment, And Surface Water/Aquatic Plant Systems , Pamela Joan Rice Jan 1996

The Persistence, Degradation, And Mobility Of Metolachlor In Soil And The Fate Of Metolachlor And Atrazine In Surface Water, Surface Water/Sediment, And Surface Water/Aquatic Plant Systems , Pamela Joan Rice

Retrospective Theses and Dissertations

Metolachlor and atrazine are two of the most widely used herbicides in the Midwest. Detection of pesticides in drinking water resources has increased interest in the environmental fate of these compounds in soil, surface water, and groundwater. The persistence of a compound and its adsorption to soil are the two most important factors related to the off-site movement of pesticides from the soil to groundwater or surface water. The aim of my research was to (1) study the environmental fate of metolachlor in soil and evaluate its potential to become a groundwater contaminant and (2) investigate the persistence of metolachlor ...


Degradation Of Chlorpyrifos In Soil: Effect Of Concentration, Soil Moisture, And Temperature , James Henry Cink Jan 1995

Degradation Of Chlorpyrifos In Soil: Effect Of Concentration, Soil Moisture, And Temperature , James Henry Cink

Retrospective Theses and Dissertations

The dissipation of the organophosphorus insecticide chlorpyrifos was investigated in field and laboratory samples. Six field locations were selected within the United States, and included the states of Arizona, Florida, Hawaii, Iowa, Mississippi, and Texas. Five of the six locations were selected based on their suspected aggressive degradative capabilities towards this chemical;In the field study, chlorpyrifos was applied to surficial trenches prepared on the north and south side of each building and parallel to the foundation. In the soil samples from Florida, Hawaii, and Texas, concentrations decreased by more than 50% of the initial concentration within 3 mo of ...


Effects Of Cadmium On Juvenile Bluegill (Lepomis Macrochirus) Foraging Behavior And Growth , Michael D. Bryan Jan 1993

Effects Of Cadmium On Juvenile Bluegill (Lepomis Macrochirus) Foraging Behavior And Growth , Michael D. Bryan

Retrospective Theses and Dissertations

Standardized toxicity testing protocols for assessing chemical hazards to aquatic organisms inadequately consider behavioral effects of toxicants; yet, organisms behaving abnormally in the wild experience reduced growth, fitness, and higher mortality. This study determined the effects of cadmium (0, 30, 60, 120, and 240 [mu]g/L) on juvenile bluegill (Lepomis macrochirus) foraging behavior in three 28-d functional response experiments, and one 24-d multi-prey experiment. The study also examined how cadmium-altered behaviors contributed to reduced growth rates. Different sizes of Daphnia magna and D. pulex were used as prey in these experiments. The rate of change (i.e., trends over ...


Metallothionein And Bioaccumulation Of Cadmium In Juvenile Bluegills Exposed To Aqueous And Sediment-Associated Cadmium , William Gregory Cope Jan 1991

Metallothionein And Bioaccumulation Of Cadmium In Juvenile Bluegills Exposed To Aqueous And Sediment-Associated Cadmium , William Gregory Cope

Retrospective Theses and Dissertations

I evaluated metallothionein (MT), free (unbound) hepatic cadmium and whole body cadmium as indicators of cadmium exposure in juvenile bluegills Lepomis macrochirus in laboratory tests. Two types of cadmium exposure were tested; aqueous and sediment-associated. In the aqueous tests, fish were exposed to cadmium (0.0 to 32.3 [mu]g/L) in an intermittent-flow diluter. The experimental design for the aqueous exposure was completely randomized and included two replicates in each of eight treatments (seven cadmium exposures and one water control). In the sediment-associated cadmium test, fish were exposed to resuspended river sediment containing 1.3 to 21.4 ...


A Physiological Approach To The Sublethal Effects Of Cadmium In Lampsilis Ventricosa , Teresa J. Naimo Jan 1990

A Physiological Approach To The Sublethal Effects Of Cadmium In Lampsilis Ventricosa , Teresa J. Naimo

Retrospective Theses and Dissertations

Previous studies of contaminant effects on freshwater mussels have been restricted to tissue contaminant concentrations and distribution among tissues. Although no standardized toxicity tests are available, acute toxicity tests have been conducted on freshwater mussels. Chronic toxicity tests which mimic the continuous low-level contaminant exposure these organisms may receive in nature are needed. A physiological approach was taken in this study to examine the sublethal effects of cadmium (0, 30, 100 and 300 ug/l) on the metabolic activity of adult Lampsilis ventricosa. A 28-day toxicity test was conducted using a proportional diluter. Ten mussels were placed into each of ...