Investigating the temporal trends in PAH, PCB and OCP concentrations in Hartbeespoort Dam, South Africa, using semipermeable membrane devices (SPMDs)

Abstract

The seasonal variability of persistent organic pollutants in Hartbeespoort Dam, South Africa, was investigated using semipermeable membrane devices (SPMDs) as passive samplers. Freely dissolved waterborne  polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were sampled to investigate  seasonal changes in their concentrations. Exposure of the passive  samplers was done for 14 days at the same sampling site in each of the four seasons of the year, in 2011. The SPMD-derived analyte amounts  enabled the calculation of time-weighted averages of free dissolved  waterborne levels of the contaminants. Concentrations ranged from 30.0 ng·l^-1 to 51.5 ng·l^-1 for PAHs, 38 pg l^-1 to 150 pg·l^-1 for PCBs, 9.2 to 10.4 ng·l^-1 for HCHs and 0.3 to 0.8 ng·l^-1 for DDTs, respectively. It was also  noted that the winter season generally exhibited higher contaminant  concentrations for most compounds studied, which likely reflects the  seasonality of their atmospheric deposition. An attempt was also made to identify possible sources of PAH contaminants in the dam by examining PAH ratios. These diagnostic ratios were inclined towards pyrogenic sources of pollution, except for the winter season where both pyrogenic and  petrogenic sources likely contribute to the contamination pattern.

Keywords: Hartbeespoort dam, persistent organic pollutants,  semipermeable membrane devices, water-dissolved concentrations, temporal trends.