Thesis (Ph. D.)--University OF MICHIGAN.

Thesis (Ph. D.)--University OF MICHIGAN. / CHAIRMAN: STEVEN P. LEVINE.

Pesticides are used primarily for agricultural purposes in the US and while these chemicals provide many benefits, the inherent toxicity of the compounds pose a substantial risk to the environment. These chemicals may enter water bodies in areas with a high proportion of agricultural land use through surface run off, ground water discharge, and erosion, and negatively impact non-target aquatic organisms. As a result, Louisianas estuaries may be vulnerable to a variety of compounds, including the herbicide atrazine. Atrazine is used extensively throughout the Midwest and has been known to enter the Mississippi River through surface runoff and ground water discharge. The River transports the compound downstream to the delta, where it is discharged into Louisianas coastal estuaries. Due to the high amount of sugarcane production in the southeastern part of the state, atrazine also has the potential to enter these systems indirectly through agricultural runoff, and adversely affect native aquatic organisms. Because it is a photosynthesis inhibitor, phytoplankton communities may be especially susceptible to atrazine exposure. The phytoplankton stress response in these systems may be critical because phytoplankton form the base of the food web and are essential to the production of the entire ecosystem. The purpose of this study was to determine the extent of atrazine contamination in Louisianas estuaries, and its effect on local phytoplankton stress response. Field samples were taken under low and high flow and nutrient conditions from Breton Sound and Barataria Estuary. The results showed that atrazine was consistently present in these systems at low levels. Local phytoplankton from Barataria Estuary were also grown in microcosm and exposed to an atrazine dilution series under low and high nutrient conditions to determine the phytoplankton stress response. The treatment groups that received 5 ppb and 50 ppb atrazine treatments under high nutrient conditions exhibited an extended lag phase and entered into the exponential growth phase several days after the control groups. Overall, communities in nutrient enriched treatment groups exhibited higher growth response, oxygen production, and were healthier than non-enriched groups, indicating that atrazine exposure may induce a stress response in phytoplankton communities under low nutrient conditions.

<p> Alfalfa Trap Cropping Increases Abundance Of Key Arachnids In An Organic Strawberry Agroecosystem Eighty three percent of the strawberries consumed in North America are grown in California, where the widespread use of insecticides has become hazardous to public health. The intensive use of pesticides for growing strawberries causes serious health risks to farm workers, in addition to contaminating the soil and groundwater. The cost to the environment and public health in the United States is estimated at $12 billion annually. Finding effective nontoxic management strategies for insect pests has become essential for long term sustainability. One strategy strawberry producers can use to promote sustainability is to increase the effectiveness of biological control techniques. Field experiments in other crops suggest that arachnid diversity and abundance may provide such a role in controlling insect pests and that agroecosystem diversification can enhance arachnid populations. This study therefore evaluated the composition, abundance, and pest control potential of arachnid communities in an organic strawberry field in California. The study found that by integrating alfalfa trap crops into organic strawberries, arachnid populations were substantially increased. Results reflected substantial increases in both male and female arachnid populations in and near alfalfa strip crops, with spider and harvestman arachnid families increasing most dramatically. Preliminary data suggest that an increase in alfalfa trap crops may lead to a reduction of the primary strawberry insect pest, <i>Lygus hesperus</i>, which is consumed by arachnids. These results provide useful new information for California farmers.</p>

The long-term performance of zero-valent iron for reductive dechlorination of trichloroethylene (TCE) and perchloroethylene (PCE) was investigated. The effects of elapsed time, mass transfer limitations, influent halocarbon concentration, and water chemistry on reductive dechlorination rates were studied in a series of column reactors. Dechlorination rates were pseudo-first order in reactant concentration for submillimolar halocarbon concentrations. With increasing elapsed time, reaction rates deviated from pseudo-first order behavior due to reactive site saturation, and increased iron surface passivation towards the influent end of each column. Corrosion current measurements indicated that halocarbon reduction on fresh iron surfaces was cathodically controlled, whereas on aged iron surfaces, iron corrosion was anodically controlled. The decrease in TCE reaction rates over time can be attributed to anodic control of iron corrosion, and not to increasing reactant mass transfer limitations associated with diffusion through porous corrosion products. The disparity between amperometrically measured reaction rates and those measured in the column reactor indicated that halocarbon reduction may occur via direct electron transfer or may occur indirectly through reaction with atomic hydrogen absorbed on the iron surface. The kinetics, reaction mechanisms, and current efficiencies for electrochemical reduction of TCE and CT were investigated using flow-through, iron electrode reactors. Typical reduction half-lives for TCE and CT in the iron reactor were 9.4 and 3.7 minutes, respectively. Comparisons of amperometrically measured current efficiencies with those measured in the flow-through reactors, and the weak effect of electrode potential on TCE reaction rates, indicated that the primary pathway for TCE reduction by iron and palladized iron electrodes was indirect, and involves atomic hydrogen as the reducing agent. For CT, similar amperometric and analytically measured current efficiencies indicated that the primary mechanism for CT reduction is direct electron transfer. Chronoamperometry (CA) and chronopotentiometry (CP) analyses were used to determine the kinetics of CT and TCE reduction by a rotating disk electrode in solutions of constant halocarbon concentration. The transfer coefficient for CT was independent of temperature, while that for TCE was temperature dependent. This indicated that CT reduction was limited by the rate of electron transfer. The temperature dependent transfer coefficient for TCE indicated that its reduction was limited by chemical dependent factors. In accord with a rate limiting mechanism involving an electron transfer reaction, the apparent activation energy (Ea) for CT reduction was found to decrease with decreasing electrode potential. Conversely, the Ea for TCE reduction showed a slight increase with decreasing electrode potential, supporting the conclusion that its reaction rate was not limited by the rate of electron transfer.

Approximately 4.9 million barrels of crude oil along with natural gas were released into the Gulf of Mexico (GoM) from April to July 2010 (Deepwater Horizon, DWH, spill). Impacts of this magnitude seldom occur in the GoM (Ixtoc I was the last spill close to this magnitude occurring in 1979), and one cannot predict when they will happen. Major constituents of concern found in crude oil are Polycyclic Aromatic Hydrocarbons (PAHs), which often have low volatility that allows for prolonged existence in the environment. PAHs are compounds of concern according to the United States Environmental Protection Agency (USEPA), with one characteristic being that they have the potential to accumulate within adipose tissue. Several PAHs are listed as mutagenic and carcinogenic, making their presence in commercial fishery populations of major environmental concern. Gulf menhaden fishery was chosen for use as an indicator for impact of crude oil exposure in the years following the spill event. Total whole body PAH concentrations along with both benzo[a]pyrene, toxic and mutagenic equivalents (BaP-TEQ and BaP-MEQ respectively), were used to determine overall impact on the species. Proposed standard weight equations and length categories for Gulf menhaden were developed to assess morphological changes in the species. Lipid content was also used as a metric for determining overall health of the Gulf menhaden. Results are outlined in each chapter abstract.

The Deep Water Horizon oilrig explosion led to the release of 6.8 ± 1.7 x 108 kg or 4.9 million barrels of petroleum hydrocarbons into the Gulf of Mexico. The spill persisted from the end of April to mid July 2010 affecting a significant portion of the Gulf coast. The effects of this spill are being studied in labs across the country, and this thesis investigated high-energy water accommodated fractions (HEWAFs) as a potential tool for use in this effort. Water accommodated fractions (WAFs) are mediums containing only the fraction of petroleum that remains in aqueous phase after a mixing energy has been removed, and after a period sufficient for phase separation. HEWAF was the exposure medium of choice because this type of WAF is created by vigorous mixing of seawater with crude oil, similar to what occurs in the environment. The effects of plankton (a zooplankton and phytoplankton species) on the toxicity of HEWAFs were also investigated because the spill occurred at a time of year when plankton populations are especially high in the Gulf of Mexico. Dr. Sarah Webb looked at how the HEWAFs and inclusion of plankton affected the test species, Anchoa mitchilli. The inclusion of plankton was also meant to more closely resemble the natural environment, and give a more accurate indication of oil spill dynamics in the Gulf ecosystem. The trials conducted throughout this experiment demonstrated that concentrations of aromatics and alkanes increased steadily with increases in HEWAF loadings. At high HEWAF loadings (33.3% HEWAF and above), alkane and aromatic concentrations in samples containing plankton were elevated; however, this effect dropped off in lower HEWAF concentrations (15% HEWAF and below). HEWAF shows potential as a tool in exposures simulating GoM conditions, but much more work needs to be done before the results they yield are reliable. The species responsible for the planktonic effect seen in the high HEWAF loading studies was not determined in this study; however, the results do show that plankton might play a significant role in crude oil partitioning in the environment. This would make plankton important in exposures for determining real world oil toxicities.

This research examines the efficient control of SO₂ from ships, a topic that has been discussed at the International Maritime Organization (IMO). The focus is on the economic evaluation of this problem, involving the concept of efficient abatement costs of controlling environmental externalities. The task is to derive an economic framework for quanlifying the costs and benefits of emissions control and then to evaluate environmental regulations on the basis of resource and environmental economic efficiency. For this purpose, this study includes a theoretical consideration of optimal emission in the case of multiple emitting agents as an appropriate framework for discussion of the SO₂ problem from ships, the derivation of an abatement cost function of SO₂ emissions, and a cost-benefit analysis for the optimal regulation of SO₂ by employing an appropriate economic model containing an abatement cost function and an environmental damage function. Theoretical consideration and cost-benefit analysis indicate that more efficient solutions can be achieved than the currently proposed IMO mandates. This will depend on the extent to which (1) variation in damage among affected areas is evidenced, (2) variation in abatement cost functions among emitting agents is effected, and (3) the range of potentially effective countermeasures is employed according to agent's choice. Based on the theory, a simple cost-benefit assessment is derived under the assumptions and conditions implied by the IMO to define their varied regulatory mandates and concerns. The method is to derive abatement cost engineering and environmental damage functions from pseudo-data for a representative case (Rotterdam). The derived formulation shows that the short-run optimal level of sulfur content regulation is 3.0% for bunker oil and 2.0% for land-based heavy oil in Rotterdam. Major conclusions of this research are that the regulation of SO₂ from ships should be considered on a region or area specific basis, and that the regulation should extend not only to ships but also to all relevant SO₂ emitting agents causing environmental damage, including land-based facilities.

Solid waste is a global issue. As developing countries strive to improve their economic situations and standings in the world community, they face extreme underfunding in vital areas of local infrastructure, especially solid waste management. As populations continue to grow, solid waste and its management will become a very serious issue. This dissertation addressed the problems of insufficient available data and inadequate funding in an urban center in a small developing country with respect to future solid waste management. The aim was to develop a quick, simple and cost-effective check-list that could be used by decision-makers in developing countries of similar characteristics, in dealing with current and future planning for improved solid waste management. Residential municipal solid waste (RMSW) was analysed from three main locations, which where Georgetown, Guyana and Tucson and Sells, Arizona in the United States. Due to the lack of data available in Guyana, several other locations were used for lesser comparisons. These were Miami, Florida, and the Kaibab-Paiute Indian Reservation and Patagonia, Arizona. The waste streams of each were compared, as were the physical, social and economic situations of the main three locations. Past and current solid waste management practises were also compared. Results indicated that RMSW in all places contained little hazardous component. The waste in Georgetown comprised mostly of organic food waste, as has been found in other developing nations. Based on reports of foreign consultants, many solutions and improvements suggested for solid waste management in Georgetown have not been feasible and technologies brought from developed countries have been too high-tech. Solutions in developing countries need to be low-tech and those who try to solve problems must take into consideration local limiting factors and work within their constraints. Since data are seldom available, it is important to communicate with those who work in solid waste management as they are an invaluable source of information.

This research investigated the mechanisms controlling chromate and arsenate removal by zerovalent iron media. The removal kinetics of aqueous Cr(VI) and As(V) were studied in batch experiments for initial concentrations ranging from 100 to 10,000 μg/L. Removal kinetics were also studied in columns packed with zerovalent iron filings over this same concentration range. Electrochemical analyses were used to investigate the electron transfer reactions occurring on the iron surface, and to determine the effect of chromate and arsenate on the iron corrosion behavior. The removal mechanism for chromate involved reduction to Cr(III) and the formation of hydroxide precipitates. Increasing chromate concentrations resulted in decreasing removal rates due to iron surface passivation. Even at low concentrations, chromate acts as a corrosion inhibitor and decreases iron corrosion rates. The condition of the iron surface prior to exposure to chromate determined the chromium removal kinetics. Air-formed oxides significantly inhibited chromate removal, whereas oxides formed in anaerobic, chromate-free water resulted in higher removal rates. Although direct reduction of chromate at cathodic sites on the iron surface was observed at early elapsed times, chromate removal eventually became limited by the rate at which Fe²⁺ could be generated at anodic sites. The removal mechanism for arsenate did not involve reduction and was due to the formation of inner-sphere, bidentate complexes with iron corrosion products. At low arsenate concentrations the rate of arsenate removal was limited by diffusion to adsorption sites. At high concentrations the rate of arsenate removal was limited by the rate of adsorption site generation resulting from iron corrosion. Adsorbed arsenate blocked electroactive sites on the iron surface and decreased iron corrosion rates. Arsenate is expected to remain as the principal adsorbed species in iron filter media because electrochemical reduction of As(V) to As(III) is not favorable under the conditions relevant to freely corroding iron.