PhD. (Energy Studies) / A review of health effects of emissions from solid fuel combustion shows clear links between morbidity and mortality, and residential combustion smoke exposure. On the interior plateau of the South African Highveld, use of coal fuel in informal domestic braziers – imbaulas – constitutes a major source of local ambient and household air pollution. This thesis aimed to develop an improved understanding of the complex processes of packed-bed combustion in small domestic devices studying smoke emissions from informal domestic stoves. A robust dilution sampling system for testing emissions from residential coal-burning appliances was developed and used in the emission studies. Systematic experiments were carried out to evaluate thermal performance and emissions of coal braziers, varying fire ignition method, ventilation rate, fuel moisture and fuel quality. Three field-collected and three laboratory constructed braziers were tested, with a range of ventilation hole-densities. The variables measured are particle mass (PM2.5 and PM10), gases (CO, CO2, NOx), and particle composition and morphology. Emission factors, referenced to zero excess oxygen are reported. Two fire-ignition methods are evaluated namely: the conventional bottom-lit updraft (BLUD) method, and the top-lit updraft (TLUD)–the so-called Basa njengo Magogo method. PM2.5 and PM10 emissions reduced by 80% on average when using the TLUD in contrast to the business-as-usual BLUD method. High smoke emissions from the BLUD method during pyrolysis are found to be associated with an oxygen deficit, allowing products of incomplete combustion to be emitted. Influences of ventilation rates on the stove emissions are reported – products of incomplete combustion (PM2.5 and CO) are higher for low ventilation rates. For a given device, PM2.5 and PM10 emission factors reduce by ~50% from low to high ventilation rates (an advantage offset by firepower too high for convenient cooking).

A site-specific artificial stream system receiving selected levels of fly ash, heavy metals, or sulfates was compared to a natural stream (Adair Run) influenced by effluent from the fly ash settling basin at Glen Lyn, Virginia. Aufwuchs communities colonizing glass microscope slides were monitored for dry weights, ash-free dry weights, chlorophylls, ATP, and 14-carbon and 35-sulfate assimilation rates. Productivity appeared to be enhanced in Adair Run due to increased concentrations of sulfates (150 mg/l), and temperature (delta T=4. 5 C) in the ash basin effluent. A recovery response was observed following termination of basin operation. Artificial streams receiving selected concentrations of fly ash at low TSS (8.0-25 mg/l) exhibited no inhibition for all parameters except chlorophyll a and ATP. Higher levels (80-100 mg/l) depressed all aufwuchs parameters except AFDW within six days. Six heavy metals (Cd, Cr, Cu, Ni, Pb, Zn), when collectively pumped into artificial streams at concentrations modeling the ash basin effluent effectively lowered productivity parameters. This was followed by a slow recovery response. Aufwuchs demonstrated an ability to bioconcentrate heavy metals from ambient water. Streams dosed with sulfates demonstrated a stimulation response at concentrations modeling the Adair Run system. Current U.S. EPA effluent guidelines for fly ash (30 mg/l maximum weekly average; 100 mg/l maximum) are evaluated concerning the degree of protection afforded primary producers of aquatic receiving systems. / Master of Science