Determination of Polycyclic Aromatic Hydrocarbons (PAHS) resulting from wood storage and wood treatment facilities for electricity transmission in Swaziland

摘要

A study was conducted in two sites: one at an electricity storage facility belonging tothe Swaziland Electricity Board (SEB) and the other at a facility that belongs to itstreated pole supplier, the Thonkwane wood creosote treatment plant. The drainagesystem of these sites leads to surface waters in rivers. This is a cause of concernsince creosote contains polycyclic aromatic hydrocarbons (PAHs), which are listedas priority pollutants by the US Environmental Protection Agency. They have toxic,mutagenic and carcinogenic effects and as a result they pose a threat to human lifeand the environment. No previous studies have been done on PAHs in Swaziland.The main objective of this study was to determine the impact of the SEB storagefacility and the creosote treatment plant by investigating the extent of PAHs insurrounding environments (soil, sediments and surface waters).Preliminary studies were undertaken on the storage facility and the creosotetreatment plant. No PAHs were detected from the pole storage facility; therefore thecreosote wood treatment facility was selected as the ideal site at which to conductthe research. Soil samples were collected from depths 15 cm and 60 cm at pointsaround the creosote plant, including effluent discharge points. The samples wereextracted by solid-phase micro extraction (SPME) and analysed by GC/MS. TheGC/MS, incorporating a solid phase micro extraction step, provided detection limitsranging from 0.12 μg/g to 20.08 μg/g. The pollution patterns in the study site wereassessed using cluster analysis and principal component analysis.Most of the 16 US EPA-listed priority pollutants were detected from the creosotewood treatment facility. PAHs such as anthracene, fluorene, naphthalene andfluoranthene were dominant in all the sampling sites. The compounds occurred invery high concentrations (0.64, 0.46, 0.27 and 0.26 mg/kg respectively). Thesecompounds are found in pure creosote as determined in the sample taken from theThonkwane creosote tank site. The highest concentration of PAHs was observed inthe soil samples taken next to the road site.The concentrations of the identified PAHs were above the acceptable minimal levelallowed in soil by the US EPA and Swaziland Environment Authority (SEA). Thelevels of the PAHs are also above the recommended US EPA limit in soil, which is0.1 mg/kg. The results indicated that significant soil pollution was taking place insome of the sampling sites.The top layer (0, 15 cm) contained many PAHs at high levels whilst the 60 cm layerhad a lower number of PAHs which were also in low concentrations. This providedan indication that there is no downward movement of PAHs from the surface layer tounderground layers. The potential exists for contamination of surface waters whenthere is runoff from the project area. This is a cause of concern, since both thecreosote treatment plant and areas outside the facility are contaminated. Therefore,the site has to be cleaned up, preferably by using a phytoremediation technique.