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Acid mine drainage (AMD), a result of oxidation of minerals containing reduced forms of sulfur (pyrites, sulfides) upon exposure to water and oxygen, is an environmental problem associated with abandoned mined lands (AML). Numerous studies have documented the impacts of AMD upon aquatic communities within acidified stream reaches; these impacts include reduced taxonomic richness and abundance, and/or a shift from pollution sensitive to pollution tolerant species. This dissertation comprises a number of integrative assessments and experiments conducted to investigate the nature of AMD ecotoxicity in the upper Powell River watershed. Emphasis was placed upon bioassessment methodologies and AMD impacts beyond the zone of pH depression. Major findings and processes developed included: 1) an Ecotoxicological Rating (ETR) system was developed that integrates chemical, toxicological, and ecological data into a single value depicting the relative environmental integrity of a given station within a watershed; 2) water column chemistry rather than sediment toxicity was the major factor causing acute toxicity to aquatic biota in close proximity to AMD discharges; 3) solid ferric hydroxide can cause acute toxicity to standard test organisms in the absence of dissolved iron; 4) Asian clams (Corbicula fluminea) can be used to detect both acutely toxic AMD inputs and nutrient loading in low order streams, and clam responses of survival and growth reflect those of indigenous communities to the two contaminant types; 5) aluminum (Al) in transition from acidic to neutral pH waters can cause acute toxicity to aquatic invertebrates, and may be the cause of impaired benthic macroinvertebrate communities in neutral pH (>7.0) waters downstream of an acidic tributary; 6) in the larger river system (North Fork Powell and Powell mainstem), urban inputs appear to have a greater influence upon aquatic communities than metal loading from AMD impacted tributaries; 7) the use of individual level assessment endpoints, such as Asian clam growth in in situ toxicity tests, eliminates variables that may confound attribution of community level impacts to contaminants; and 8) the near elimination of predatory stoneflies (Plecoptera) downstream of the Stone/Straight Creek tributary to the North Fork Powell River was associated with water column Al concentrations. This research was funded by the Virginia Department of Mines, Minerals, and Energy, Division of Mined Land Reclamation, and by the Powell River Project. / Ph. D.

A wetland was constructed near Norton, VA by Westmoreland Coal Company to treat acid mine drainage (AMD) from an inactive coal refuse pile. The AMD had an average inflow pH of 7.0, and average inflow concentrations measuring 4 mg/L total Fe, 3 mg/L total Mn and 450 mg/L dissolved sulfate. An 18 month field study of water quality improvement and sulfate-reducing bacterial (SRB) populations revealed that the wetland was effectively treating the AMD. Iron and Mn both met compliance standards set by the EPA requiring an instream Fe concentration of 3 mg/L and an instream Mn concentration of 2 mg/L. SRB averaged 8.7 x 10⁴ through the 18 month study period as determined by the Most Probable Number (MPN) method. The concentration of sulfate was decreased by an average of 360 mg/L as the AMD passed through the wetland. In a separate laboratory study, the effect of carbon addition, pH and Fe concentration on microbial sulfate reduction and the subsequent precipitation of Fe and Mn was determined in mesocosms built to simulate a wetland. Mesocosms were constructed with plexiglass sheets and measured 6" x 6" x 24". Each mesocosm was filled with a 4-inch layer of limestone gravel beneath 17 inches of weathered pine bark mulch. A perforated PVC pipe was installed within the limestone layer to act as an underground drain. With mulch as the only source of available carbon, a 15% decrease in total sulfate concentration occurred in AMD containing initial concentrations of 1500, 750 and 375 mg/L sulfate. The population of SRB averaged 10⁵/ g dry mulch. The addition of 300 mg/L carbon as lactate resulted in an a 3 log₁₀ increase in SRB population. Following the addition of carbon as lactate, the concentration of sulfate decreased 95%. Total Fe decreased 90% from inflow concentrations prior to the addition of lactate, and decreased 96% following the addition of lactate to the AMD. The effect of varying the influent pH of AMD was studied using wetland mesocosms, and a pH of 3.5 adversely affected microbial sulfate reduction and water quality improvement. Populations of SRB decreased by 3 log₁₀ from an initial population of 10⁸ SRB/g dry mulch. Iron and Mn concentrations decreased 70 and 37% respectively. Hydrogen ion concentration increased to 7.0 and above when inflow pH was 4.5 and 6.0, but increased to an average of 6.4 when inflow pH was 3.5. The effect of different concentrations of Fe within AMD was investigated using wetland mesocosms, and total inflow Fe concentrations of 155 and 301 mg/L resulted in a greater percent decrease in sulfate concentrations than at a lessor Fe concentration averaging 85 mg/L. Total Mn decreased 12% at an inflow Fe concentration of 85 mg/L, and decreased 43% at an inflow Fe concentration of 301 mg/L. The results generated from both the analysis of the Pine Branch wetland and the laboratory mesocosm experiments demonstrate that subsurface flow constructed wetlands are a viable form for treatment of AMD. 2197820b-4775-4425-b667-55393f34b513,"This thesis deals with the deliberate insertion of nonlinear elements in second-order linear control systems for the purpose of improving their transient response. The main body consists of a method of obtaining a desired step response by placing a nonlinear computer in the forward loop. This computer fixes the system trajectory in the phase plane by determining the required output velocity for the error present at any time. An inner control loop adjusts the output velocity to agree with the computed signal in an extremely short time, thus giving a very close agreement between actual and desired responses. Several examples are presented to show the application of this method, and experimental verification is obtained with an analog computer. Areas of future study and practical limitations are discussed in the final sections of the thesis. / Master of Science

Black Creek is a small watershed located in Wise County, Virginia, west of the town of Norton. At the time of this survey, the watershed encompassed approximately 929 hectares of mine and forest lands with a small recreational area. Black Creek proper is a third-order stream approximately 6.7 km in length from its headwaters to its confluence with the Powell River in Kent Junction. Black Creek and several of the tributaries within the watershed were previously identified as areas impacted by acid mine drainage. The watershed was used in a study to identify sources of acid mine drainage and the best methods for its evaluation. The acid mine drainage sources were first identified using visual inspection and field chemistry. Additional stream segments were then included in the assessment process using metal (aluminum, copper, iron, magnesium, manganese, and zinc) analyses of both overlying water column and sediments. Using an upstream reach of Black Creek as a reference, short-term toxicity testing was employed, as well as a long-term purge study. The pH at sampling locations ranged from 2.75 to 7.87 SU, and conductivity ranged from 196 μmhos/cm to 2040 μmhos/cm. All metals were elevated when compared to the reference. Water column samples collected from locations with low pH were acutely toxic to Daphnia magna and Pimephales promelas. Mortality was high in the elutriant test at locations where pH was low, conductivity was elevated, metals were high, or a combination of these. In the initial sediment tests, all sampling locations were significantly different than the reference for survival of Chironomus tentans and reproduction of D. magna. One location was significantly different than the reference for survival of D. magna. In the sediment tests completed after two months, survival of C. tentans was only different from the control in three locations but was significantly different for growth at all locations. Reproduction by D. magna was again significantly less than the reference at all locations. At eight months, only two locations were significant for survival of C. tentans and after 15 months, no significant differences occurred between any stations. The study indicates that stream segments that are severely impaired by acid mine drainage are easy to identify using visual inspection and field water chemistry. Those that are moderately impaired require more investigation and may not be responsive to short-term toxicity tests. Benthic macroinvertebrates, leaf packs, and periphyton were evaluated in the field. Benthic macroinvertebrate communities and leaf-pack breakdown were evaluated at nine locations, while periphyton was evaluated at the mouth of Black Creek, as well as five sites in the Powell River receiving system. While leaf-pack information and benthic macroinvertebrate samples yielded similar information, benthic sampling was much simpler and less time consuming. Additionally, benthic macroinvertebrate sampling, particularly over several sampling events, was more sensitive at the most severely impacted AMD stations. The stations were broken down into five different categories in order to better determine which evaluation techniques were most sensitive and cost-effective. The five categories were Non-Impaired, Slightly Impaired, Moderately Impaired, Severely Impaired, and Severely pH impaired. Once the locations were categorized, each method used to evaluate toxicity was examined to determine which methods best identified acid mine drainage impairment in the Black Creek watershed. The methods utilized include the following: basic water chemistry; metals analysis of sediments and water column; acute toxicity testing using both D. magna and P. promelas; short-term elutriant and sediment tests; chronic sediment test using C. tentans and D. magna; a purge study; benthic macroinvertebrate sampling; leaf-pack and algal-tile studies. After evaluating these methods, it was determined that using basic water chemistry and benthic macroinvertebrate sampling were the best methods for evaluating acid mine drainage impairment in this watershed. The reference station was identified as Non-Impaired. Two stations located in the lower portions of Black Creek (L11 and L1) were also Non-Impaired or only Slightly Impaired with the benthic macroinvertebrate results indicating little impairment. Stations U2, U6, U7, and BBM were also found to be Slightly Impaired. The station on the margin of the wetland, U5, was Moderately Impaired. Two previously identified areas of impairment, U9 and U10, (Cherry et al. 1995) were identified as Severely pH Impaired and Severely Impaired, respectively. / Master of Science

Thesis (M.Sc.)--University of the Witwatersrand, Faculty of Science, School of Animal, Plant and Environmental Sciences, 2017. / Acidification of freshwater systems by Acid Mine Drainage (AMD) is a persistent risk to aquatic ecosystems in South Africa, particularly in Gauteng and Mpumalanga. From several studies that have been conducted, it is clear that AMD has profound effects on aquatic life and functionality of the ecosystem. One of the ecosystem processes affected by AMD is the decomposition process. It has been established that AMD-affected streams inhibit the decompositon process. [Abbreviated Abstract. Open document to view full version] / LG2018

Thesis (MSc., Geology) -- Queen's University, 2008. / Includes bibliographical references.

Please read the abstract in the section, 00front, of this document / Dissertation (MSc (Microbiology))--University of Pretoria, 2008. / Microbiology and Plant Pathology / unrestricted