Browsing by Author "Echols, Brandi Shontia"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- An Ecotoxicological Evaluation of the North Fork Holston River below Saltville, Virginia and Identification of Potential Stressors to Freshwater Mussels (Bivalvia:Unionidae)Echols, Brandi Shontia (Virginia Tech, 2007-04-13)Mercury contamination of the North Fork Holston River below Saltville, Virginia has nearly extirpated most mussel populations. Because natural recovery of these populations has not occurred, this research combined field and laboratory assessments to determine the extent of ecological impairment in the river. In situ 60-day Asian clam (Corbicula fluminea) growth studies in 2005 showed a positive correlation (p=0.03) between low clam growth and sediment mercury levels. Because of severe low flow conditions of the NFHR in late 2005 conductivity dissipation from a point source brine discharge downstream rarely reached background level (~345 µS/cm) and was observed as high as 690 µS/cm 640 m below the discharge site. In addition, conductivity doubled in the river section adjacent to the remediated Ponds 5 and 6 (rm 81.6 and 80.4). Such low flow conditions (mean flow < 50 ft3/sec) occur in the NFHR approximately every five years. This low flow situation also evidenced a thick white flocculent or floc observed to accumulate at the base of the two remediated ponds. Analysis of the flocculent determined it to be high in aluminum (1.9-38 mg/L) and iron (2.0-51.0 mg/L), well above US Environmental Protection Agency Water Quality Criteria limits (0.0087 and 1.0 mg/L, respectively); riverine sediments collected below the accumulated floc also had high levels of calcium (240,000-380,000 mg/kg) and mercury(0.62-1.7 mg/kg). Acute tests with juveniles of Villosa iris and <24-hr old Ceriodaphnia dubia were used to measure the toxicity of the brine discharge, which had a conductivity of ~ 14,000 µS/cm. Results of these tests indicated C. dubia to be more sensitive than V. iris; however, chronic toxicity test results were similar for V. iris and C. dubia. The Lowest Observed Adverse Effect Concentration (LOAEC) for mussel survivorship after 28 days was 10,000 µS/cm, while the LOAEC for growth was 5,000 µS/cm. LOAECs for the C. dubia 7-day chronic were 25 % (survivorship) and 12.5 % (reproduction), while mean conductivity at these two concentrations was 4,054 and 2,211 µS/cm, respectively. Toxicity tests conducted with Pond 6 dyke cut discharges resulted in similar lethal concentrations for C. dubia and V. iris. Forty-eight hour LC50s of these discharges ranged from 12.07-15.95 % for C. dubia, and 17.36-18.95 % for V. iris. Dyke cut discharges also exhibited exceedingly high alkaline pH (11.5-12.2), which caused 100 % mortality to C. dubia in 15 min. The Pond 5 and 6 dyke discharges are the likely source for the flocculent accumulation at the base of the two remediated pond areas. The combined effect of mercury, aluminum and iron, along with periodic fluxes of high conductivity and alkaline pH during low flow conditions may contribute to low mussel recruitment downstream of Saltville, VA.
- Use of an environmentally realistic laboratory test organism and field bioassessments to determine the potential impacts of active coal mining in the Dumps Creek subwatershed on the Clinch River, VirginiaEchols, Brandi Shontia (Virginia Tech, 2011-03-15)This research was divided into four objectives for assessing the impacts of coal mining on ecosystem health. The first objective was to provide an ecotoxicological assessment in the upper Clinch River using standard bioassessment techniques. Analysis of sediments and interstitial water (porewater) indicate higher concentrations of trace metals in samples from sites located above both a power plant (CRP) and Dumps Creek mining influences. The furthest sampling site located near Pounding Mill, Virginia (CR-PM) had higher concentrations of aluminum (2,250.9 mg/kg), copper (5.9 mg/kg) and iron (12,322.6 mg/kg) compared to samples collected directly below the Dumps Creek confluence (site CR-2). Similar results were obtained from bioaccumulation in-situ tests with the Asian clam (Corbicula fluminea) in 2009. Aluminum (7.81 mg/kg), Fe (48.25 mg/kg) and Zn (7.69 mg/kg) were accumulated in higher concentrations at CR-PM site than CR-2. However, the site located below the CRP effluent discharges (CR-3L) on the left bank had substantially higher concentrations of Al (14.19 mg/kg), Cu (6.78 mg/kg), Fe (88.78 mg/kg) and Zn (7.75 mg/kg) than both CR-PM and samples collected directly opposite of this site at CR-3R. To further understand the potential impact active mining on the Clinch River, a more comprehensive ecotoxicological evaluation was conducting in the Dumps Creek subwatershed. Field bioassessments determined that biological impairment occurred directly below a deep mine discharge (CBP 001), which was characterized by a distinct hydrogen sulfide odor. Total abundance and richness of benthic macroinvertebrates decreased to 3.5-20 and 1.25-2.3, respectively at DC-1 Dn. The discharge also caused the proliferation of a sulfur-oxidizing bacterium, Thiothrix nivea. During continuous discharge of the effluent, the bacteria was observed coating all surfaces at DC-1 Dn and may also contribute to an Fe-encrusted biofilm observed on in-situ clams at downstream site, DC-2 Dn. Toxicity tests with mining effluents indicate some potential toxicity of the 001 discharge, but this was variable between test organisms. Selecting the most appropriate test species for sediment and water column assays has been a primary goal for ecotoxicologists. Standard test organisms and established test guidelines exist, but US EPA recommended species may not be the most sensitive organisms to anthropogenic inputs. Therefore, Chapter Three and Four addressed the use of mayflies in routine laboratory testing. Preliminary results of toxicity tests with the mayfly, Isonychia sp. (Ephemeroptera) suggested that Isonychia were moderately sensitive to NaCl after 96-hr with an average LC50 value of 3.10 g NaCl/L. When exposed to a coal-mine processed effluent, Isonychia generated LC50 values that ranged from 13 to 39% effluent and were more sensitive to the effluent than Ceriodaphnia dubia. Based on results of the feasibility study in presented in Chapter Four, field collected organisms appear to be too unpredictable in test responses and therefore, such tests would be unreliable as stand-alone indicators of effluent toxicity.