An existing individual tree growth and yield model (PT AEDA2) was modified study the potential effects of air pollution stress on the growth and yield of loblolly pine plantations. These modifications were based on the assumption that pollution stress on older trees could result in reductions in diameter and height growth, decreases in photosynthesis, and increased losses of older foliage, as demonstrated in some seedling studies. One modification applied differential levels of reductions of diameter and height increments to various percentages of trees. Results indicated no sizeable losses on total volume per acre except at severe stress levels (-32 and -64 percent annual diameter and height increments on 50 and 67 percent of the trees). Another modification consisted of developing a measure of photosynthetic potential to drive diameter and height growth in the model. This new measure was an estimate of foliage weight which was weighted by a factor of photosynthetic efficiency and needle retention for each age class of needles. Reductions of these weighting factors were applied to simulate air pollution stress. Results of this modification show that if air pollution does cause a decrease in photosynthesis and needle retention rates, the impact on over-all stand productivity is minimal. These results are not intended to be quantitative estimates of the effect of air pollution on tree growth but to identify potential areas within an existing growth and yield model where biologically-oriented processes to simulate air pollution impact can be incorporated. / Master of Science

The radiorespirometric technique, a modification of the heterotrophic activity assay, was evaluated as a monitor of toxic perturbation. The basis for the technique consists of trapping ¹⁴CO₂ evolved from the catabolism of a ¹⁴C-labeled substrate, and analyzing the resultant activity in a scintillation counter. An index of change in heterotrophic activity, the percent suppression, was calculated from the ratio of a toxified sample to a control. The effect of pentachlorophenol (PCP) on the heterotrophic activity of a laboratory-maintained aquatic culture was evaluated. The radiorespirometric technique detected changes in the heterotrophic activity for shorter exposure times and for PCP concentrations an order of magnitude lower than previously reported in the literature. Only 0.75 mg/L PCP caused approximately a 54 percent suppression of heterotrophic activity after a 30 min exposure. Radiolabeled glucose and glutamic acid were evaluated, and the radiorespirometric method was more sensitive at detecting changes in heterotrophic activity when the substrate used was glutamic acid. Whereas the error associated with the evolution and trapping of ¹⁴CO₂ apart from that introduced by microbial activity was only 13 to 20 percent, the variability induced by variations in the composition of the stock culture was quite high. The variability and lack of replicability of the heterotrophic activity experiments was the result of the heterogenous distribution of microorganisms and the alterations in the composition of the stock culture with time. The fit of the data to the first-order model of saturation kinetics was evaluated. The data derived during the study did not fit the first-order model probably because the added substrate concentrations were at trace levels. A protocol for the radiorespirometric technique is recommended. / M.S.

published_or_final_version / Geography and Geology / Master / Master of Philosophy

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

Enteroviruses affect a broad segment of the population throughout the world and have been suspected to play a major role in waterborne disease for quite some time. The presence of these viruses in drinking water supplies constitutes a major health risk to the population because of their low infectious dose. The monitoring and study of these viruses in the environment have been limited by the current standard detection methodologies. Nucleic acid probe hybridization is a new and effective approach for the study and detection of these viruses in the environment. An important step in the detection of viruses in concentrated water samples by nucleic acid probes is the isolation of the viral genome from the water sample for hybridization. Previously, a series of time consuming organic extract ions was used to isolate viral RNA. This study reports the development of an alternative method for the isolation and preservation of viral RNA in environmental samples. Briefly, the sample is heated in the presence of an RNase inhibitor, and then applied to a hybridization membrane. This procedure has greatly reduced the time and difficulty of the assay while maintaining sensitivity and increasing consistency. This study reports the development and modification of a nonradioactive labeling system for the detection of viruses in water. Nonradioactive labels such as biotin offer several advantages over radioactive labels including unlimited shelf life, reduced cost and time of assay, and elimination of the radiation hazard. However, radioactive labels are generally the more sensitive method of detection. By combining direct and indirect labeling strategies, the sensitivity of this nonradioactive assay has been increased ten-fold. This assay can detect as little as 100 plaque forming units of poliovirus, only one order of magnitude less sensitive than radiolabeled probes. This assay is also ten-fold less sensitive than radiolabeled probes for the detection of enteroviruses in water samples. Nonradioactive probes offer a safe, inexpensive alternative to radiolabeled probes and tissue culture for the detection of viruses in the environment when ultrasensitivity is not required.

Rotaviruses are one of the most significant causes of diarrheal disease in the world. Their presence in groundwater and drinking water supplies constitutes a health risk to the population. The study of rotaviruses in the environment has been hampered by the lack of accessible and consistent detection methodologies. Gene probes and other molecular techniques are a novel approach for the detection of these viruses in water. The feasibility of these new techniques for the detection and study of rotaviruses in the environment has been assessed using the simian SA-11 and the culturable human Wa rotavirus strains as models. Two general approaches have been undertaken consisting of hybridization of probes with genomic RNA and hybridization with mRNA produced by the virion-incorporated transcriptase. Hybridization of gene probes with genomic dsRNA of rotaviruses in environmental concentrates resulted in the detection of 10 4 immunofoci of Wa rotavirus. In vitro transcription serves as an amplification method with sensitivity 100- to 1000-fold greater than when probing for genomic RNA. The sensitivity obtained in Wa-seeded distilled water and environmental concentrates after in vitro transcription is 2 and 20 immunofoci, respectively. Proteins in environmental concentrates decrease the efficiency of probe hybridization by 10-100 fold. Also, transcriptase-inhibiting factors found in environmental samples decrease the production of mRNA. Both proteins and transcriptase-inhibiting factors can be reduced significantly with Sephadex G-200 columns. Passage of environmental concentrate through Sephadex G-200 spun columns, followed by in vitro transcription, was used to detect rotaviruses in environmental samples. Rotaviruses were detected by this combination of techniques in eight of 20 sewage samples, one of 16 tap water samples, five of 32 ground water samples, and two of nine surface water samples. Only one of 17 samples which tested positive with Wa cDNA 4 was positive for non-specific probe binding. The probing of rotavirus mRNA, amplified by the virion-incorporated transcriptase, is a practical and feasible method for monitoring these viruses in the environment.

Thesis (MTech (Environmental Management))--Cape Peninsula University of Technology, 2015. / The integrity of natural air has been compromised due to the deposition of chemical, biological and particulate substances from natural and anthropogenic sources. Adverse health consequences arising from the exposure of plants, animals and human to elevated atmospheric concentrations have been reported severally. The ambient baseline levels of many air contaminants in urban and industrial layouts of many Africa cities, especially Zimbabwe have not been fully characterized. Information on levels of these contaminants and their real time variability is therefore scarce and scanty. In this study, the ambient air concentration levels of selected gaseous pollutants in the vicinity of a fertilizer production facility in Zimbabwe were investigated. Nine sampling stations were systematically and randomly identified for the measurement of selected air pollutants (SO2, NO2, and NH3) the fertilizer production factory to capture air quality data on all wind directions. The electrochemical Drager Sensors which rely on electrochemical measuring transducer for measuring concentration of gases under atmospheric conditions was used for the measurement of NH3, SO2, and NO2. The ambient air monitored was allowed to diffuse through a membrane into the sensor liquid electrolytes, containing a sensing electrode, a counter electrode, a reference electrode, and an electronic potentiostat-circuit which ensures constant electrical voltage between the sensing electrode and the reference electrode. The flow of electrons, generated by the reaction is proportional to the concentration of the measured gas. The observed concentrations of NH3, SO2, and NO2 measured within and around the study site were very variable. Levels of NH3 ranged between 0.36 - 7.36 ppm; corresponding values for SO2 and NO2 were 0.02 - 84.61 ppm and 0.61 - 34.78 ppm respectively. These concentrations were significantly higher (p < 0.05) than measured (NH3; 0.01 - 0.05 ppm: SO2; 0.03 - 0.18 ppm: NO2; 0.17 - 1.30 ppm) at the control sampling station about 5 km from the industry. Isokinetic and dissipation of the measured gases, governed by the processes of molecular diffusion and convection, confirmed a common pattern of distance dissipation. Thus, the cloud concentrations of NH3, SO2, and NO2 within the facility were higher than observed distances away from the fertilizer factory. / Zimbabwe Presidential Scholarship