UNT Libraries - 5 Matching Results

Search Results

Ecotoxicological Investigations in Effluent-Dominated Stream Mesocosms

Description: The University of North Texas Stream Research Facility (UNTSRF) was designed to examine contaminant impacts on effluent-dominated stream ecosystems. Stream mesocosms, fed municipal effluent from the City of Denton, TX, Pecan Creek Water Reclamation Plant (PCWRP), were treated with 0, 15 or 140 µg/L cadmium for a 10-day study in August 2000. Laboratory toxicity test and stream macroinvertebrate responses indicated that cadmium bioavailability was reduced by constituents of effluent-dominated streams. The Biotic Ligand Model (BLM) for Cd was used to predict a 48 hour Cd EC50 for Ceriodaphnia dubia of 280 µg/L in these effluent-dominated streams. This value is higher that an EC50 of 38.3 µg/L Cd and a 7-day reproduction effect level of 3.3 µg/L Cd generated for C. dubia in reconstituted laboratory hard water. These results support use of a cadmium BLM for establishing site-specific acute water quality criteria in effluent-dominated streams. Although not affected by 15 µg/L treatments, organisms accumulated Cd in 15 µg/L treated streams. Hence, over longer exposure periods, Cd accumulation may increase and a no effect level may be lower than the observed 10-day no effect level of 15 µg/L. A toxicity identification evaluation procedure was utilized with in vitro and in vivo bioassays to identify estrogenic compounds in PCWRP effluent, previously identified to seasonally induce vitellogenin (VTG) in male fathead minnows. Steroids, nonylphenol ethoxylate metabolites, and other unidentified compounds were identified as causative effluent estrogens. These findings suggest that in vivo VTG bioassays should be used to confirm in vitro Yeast Estrogen Screening assay activity when effluents are fractionated or screened for estrogenicity. A subsequent 90-day cadmium study was initiated to assess long-term effluent and cadmium effects on fish endocrine function. Juvenile fathead minnows were placed in UNTSRF pool sections of replicate streams treated with 0, 5, 20 or 80 µg/L Cd. Male ...
Date: December 2002
Creator: Brooks, Bryan W.

Managing Cattail (Typha latifolia) Growth in Wetland Systems

Description: Nutrient availability, water depth, competition, and soil management effects on cattail (Typha latifolia) growth in wetland systems were examined. Soluble reactive phosphorous (SRP), nitrate-nitrogen (NO3-N), and ammonia-nitrogen (NH3-N) removals were tested at a constructed wetland receiving municipal wastewater effluent. Over all, no significant differences in nutrients occurred between diverse planted and cattail areas. T. latifolia seeds, under the canopy of Eleochoris macrostachya, had low seed germination. Established stands of emergent vegetation can prevent cattail colonization and spread. Germination of T. latifolia at various water depths was tested, and depth impacts on cattail seedling growth and survival were ascertained using various moist soil management techniques in three ponds. Water levels at 0cm and >40cm can adversely impact cattail establishment.
Date: August 2002
Creator: Sharp, Jessica Little

Phosphorus Retention and Fractionation in Masonry Sand and Light Weight Expanded Shale Used as Substrate in a Subsurface Flow Wetland

Description: Constructed wetlands are considered an inefficient technology for long-term phosphorus (P) removal. The P retention effectiveness of subsurface wetlands can be improved by using appropriate substrates. The objectives of this study were to: (i) use sorption isotherms to estimate the P sorption capacity of the two materials, masonry sand and light weight expanded shale; (ii) describe dissolved P removal in small (2.7 m3) subsurface flow wetlands; (iii) quantify the forms of P retained by the substrates in the pilot cells; and (iv) use resulting data to assess the technical and economic feasibility of the most promising system to remove P. The P sorption capacity of masonry sand and expanded shale, as determined with Langmuir isotherms, was 60 mg/kg and 971 mg/kg respectively. In the pilot cells receiving secondarily treated wastewater, cells containing expanded shale retained a greater proportion of the incoming P (50.8 percent) than cells containing masonry sand (14.5 percent). After a year of operation, samples were analyzed for total P (TP) and total inorganic P (TIP). Subsamples were fractionated into labile-P, Fe+Al-bound P, humic-P, Ca+Mg-bound P, and residual-P. Means and standard deviations of TP retained by the expanded shale and masonry sand were 349 + 169 and 11.9 + 18.6 mg/kg respectively. The largest forms of P retained by the expanded shale pilot cells were Fe+Al- bound P (108 mg/kg), followed by labile-P (46.7 mg/kg) and humic-P (39.8). Increases in the P forms of masonry sand were greatest in labile-P (7.5 mg/kg). The cost of an expanded shale wetland is within the range of costs conventional technologies for P removal. Accurate cost comparisons are dependent upon expansion capacity of the system under consideration. Materials with a high P sorption capacity also have potential for enhancing P removal in other constructed wetland applications such as stormwater wetlands and wetlands ...
Access: This item is restricted to UNT Community Members. Login required if off-campus.
Date: August 2002
Creator: Forbes, Margaret G.

A Physiological Age-Grading System for Female Hydrellia pakistanae Deonier (Diptera: Ephydridae)

Description: Conflicting opinions about the effectiveness of H. pakistanae as a biological control agent for hydrilla prompt researchers to find a method for assessing the fly's success. Developing a physiological age-grading system for the fly using ovarian morphology to detect changes in reproductive activity is useful for evaluating reproductive status of the fly in field populations. Changes in the appearance of follicular relics in ovaries with oviposition provide a reliable method to estimate fecundity. Characteristics of follicular relics were used to develop a system with eight physiological age classes, three nulliparous and five parous. Changes that occur in the fat body were used to assist in classification of nulliparous females or those with low egg counts.
Access: This item is restricted to UNT Community Members. Login required if off-campus.
Date: December 2002
Creator: Lenz, Jennifer Marie

The Use of Genetic Polymorphisms and Discriminant Analysis in Evaluating Genetic Polymorphisms as a Predictor of Population

Description: Discriminant analysis is a procedure for identifying the relationships between qualitative criterion variables and quantitative predictor variables. Data bases of genetic polymorphisms are currently available that group such polymorphisms by ethnic origin or nationality. Such information could be useful to entities that base financial determinations upon predictions of disease or to medical researchers who wish to target prevention and treatment to population groups. While the use of genetic information to make such determinations is unlawful in states and confidentiality and privacy concerns abound, methods for human “redlining” may occur. Thus, it is necessary to investigate the efficacy of the relationship of certain genetic information to ethnicity to determine if a statistical analysis can provide information concerning such relationship. The use of the statistical technique of discriminant analysis provides a tool for examining such relationship.
Date: May 2002
Creator: Howell, Bruce F.