The impact of fluoride on the environment from airborne emissions from an industrial complex

• Main Author: Khathi, Nonkululeko Fionah
• Published: 2010
• Subjects: Air pollution; Fluorides
• Online Access: http://hdl.handle.net/10210/3257

M.Sc. === This study is an investigation of environmental impacts caused by airborne fluorides around an industrial uranium and chemical facility in South Africa, the Necsa Pelindaba site. The literature study in Chapter 2 illustrates that industrial atmospheric fluoride emissions can have negative environmental impacts, including accumulation in surface soil horizons, necrosis in leaves, and fluorosis in plants and animals. Fluorides from this site are from two sources – stacks and evaporation pans. Samples to measure fluoride concentration in air, soil and vegetation and deposition rate were taken and analysed from February to August 2007. Standard analytical methods were used for the analysis of fluorides in all samples. Evaluation of historical environmental monitoring at Pelindaba showed that stack emissions were high in the year 2002 followed by a dramatic decrease in 2003 and 2004. In 2005, there was a sharp increase in emissions, with further slight increases until August 2007. For all media and sample types taken (air concentration, deposition, soil and vegetation), samples from nearby the evaporation pans had the highest fluoride concentrations. Results from sampling sites close to the stacks were lower, but still well above off-campus background sites, and above values from Pelindaba sites distant from the stacks. Fluoride concentrations in animal bones from previous studies done at the site showed enhanced fluoride concentrations compared to control samples. The project hypothesis was that fluoride emissions from Necsa Pelindaba site do not have a negative impact on the environment. This hypothesis is proven correct to the extent that no off-site adverse impacts or concentrations were observed. Limited on-campus impacts were observed localised around the evaporation pans and to a lesser extent around the stacks. Airborne fluoride concentration values around the pans only were above the South African guideline values. Deposition values were highest around the pans. The only visible leaf damage attributable to fluoride was on a Karee tree ~50 m from the edge of the pan. Soil fluoride concentrations from the current study were within the range of natural fluoride concentrations in soil. Despite evidence of local deposition, there was no evidence of fluoride accumulation in surface or subsurface soils. No impacts were observed elsewhere around the site or off-site. Based on the results of this work, fluoride emissions from the stacks do not pose a threat to the environment, provided that efficiency of the gas scrubbing equipment is maintained at current levels. Emissions from the pans pose a minor localised problem that nevertheless requires investigation and mitigation.