Distribution of persistent and PSEUDO-persistent organic pollutants in rivers draining urbanised catchments in South Africa

Abstract

This research aimed to characterise the occurrence and distribution of persistent and pseudo persistent organic pollutants in water and sediment samples from rivers in urbanised catchments in South Africa, particularly the Witwatersrand catchment area in the Gauteng Province, the Hartbeespoort Dam catchment in Gauteng and North West Provinces as well as the uMngeni River in KwaZulu-Natal Province. The objective was to highlight suitable analytical techniques for analysis of persistent and pseudo-persistent organic pollutants in the South African context where the cost of analysis is high and the procurement of high end analytical instrumentation is beyond the reach of the majority of analytical laboratories. Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) are some of the most complex, toxic and ubiquitous organic pollutants in industrialised regions and have been classified by the Stockholm Convention as persistent organic pollutants that need to be monitored in the environment in order to reduce or eliminate their release. A Dioxin-Responsive Luciferin (DR-Luc) reporter gene assay was utilised to screen for dioxin-like toxicity in sediments from the Witwatersrand catchment, with all sediment samples from the Jukskei, Klip and Vaal River testing positive for dioxin-like activity. Total DR-Luc dioxin-like activity ranged from 16 to 37 pg World Health Organisation Toxic Equivalents per gram (WHO-TEQ g-1) dry weight (dw) for the Jukskei River catchment and 1.5 to 22 pg WHO-TEQ g-1 dw for the Klip and Vaal Rivers. A comprehensive two-dimensional gas chromatography- micro-electron capture detection (GCxGC-µECD) method was developed to analyse seven PCDDs and ten PCDFs with dioxin-like toxicity in sediment samples. The highest concentration of 2,3,7,8-TCDD in the Jukskei River was found at the Midrand site (2.5 pg g-1 dw) and highest concentration of 2,3,7,8-TCDD in the Klip and Vaal Rivers (5.7 pg g-1 dw) was recorded at the Alberton site in Klip River. The results indicate that South Africa is at the moment at a general low risk of dioxin-like compound pollution. Thirty one selected indicator PCB congeners, 19 alkyl polyaromatic hydrocarbons (PAHs) and 18 parent PAHs (including 16 priority PAHs) were analysed in sediment samples from the Jukskei, Klip and Vaal Rivers using gas chromatography- mass spectrometry (GC-MS) to determine their distribution and potential sources. Aroclor 1254 and 1260 were identified as possible sources of the PCBs detected as PCB signature patterns in order of abundance were 138> 180> 206> 153> 187> 149 and 138> 153> 180> 149> 187> 110> 170 for the Jukskei and Klip River sediments, respectively. A combination of pyrogenic and petrogenic PAH sources was detected in the Witwatersrand catchment with fluoranthene, pyrene and phenanthrene being the most abundant PAH’s in both the Jukskei and Klip River sediments. Seasonal variation of triazine herbicides (as well as atrazine and terbuthylazine metabolites and degradation products), some of which are present at pseudo persistent concentrations in the Hartbeespoort Dam catchment surface water and groundwater was investigated using GC-MS and liquid chromatography-tandem mass spectrometry (LC-MS/MS). In the Hartbeespoort Dam, ∑triazine herbicide concentrations were in the order atrazine> simazine> terbuthylazine> propazine> ametryne> prometryn. Atrazine could be detected in groundwater at concentrations >130 ng L-1 in all seasons except spring. Triazine compound bioaccumulation in catfish (Clarias gariepinus) and carp (Cyprinus carpio) muscle analysed was negligible whilst Hartbeespoort Dam groundwater ∑triazine herbicide concentrations ranged between 527 and 367 ng L-1 and ∑triazine herbicide concentrations in the Hartbeespoort Dam surface water samples were >2000 ng L-1 in all seasons except spring. In light findings of endocrine and immune disrupting atrazine effects, the atrazine concentrations detected in the Hartbeespoort Dam groundwater and surfacewater may be a cause of concern. The effects of a 90 day sub-chronic atrazine exposure (0.01, 200 and 500 µg L-1 atrazine in water) on exposed African clawed frogs (Xenopus laevis) was investigated to determine impact of environmentally relevant atrazine concentrations on adult male frog gonadal development as well as survival and growth of tadpoles. Tadpole mortality rates of 0, 0, 3.3 and 70% for the control, 0.01, 200 and 500 µg L-1, respectively were recorded for 90-day atrazine exposure. Histochemical analysis with differential staining revealed gonadal atrophy, disruption of germ cell lines, significantly reduced seminiferous tubule diameter, seminiferous tubule structure damage and formation of extensive connective tissue around seminiferous tubules of adult frogs exposed to 200 µg L-1 and 500 µg L-1 atrazine concentrations. Ultrastructural analysis of the cellular organelles using transmission electron microscopy (TEM) revealed significant amounts of damaged mitochondria in testosterone producing Leydig cells as well as Sertoli cells of adult frogs. Morphometry showed reduced testicular volume and mass in all atrazine exposed adult frogs and an LC50 value of 343.7 µg L-1 was determined to cause significant mortality in tadpoles. Contaminants of emerging concern in the Hartbeespoort Dam surface water as well as in the uMngeni River estuary surface water and sediment after an episodic hospital waste contamination event were determined using LC-MS/MS. In the Jukskei River, the main source of 11 emerging pollutants (EPs), some of which are present at pseudo persistent concentrations was identified as raw sewage overflow from communities situated adjacent to Jukskei River, with the highest ∑11 EP concentration of 593 ng L-1 being recorded at the Midrand point and the lowest ∑11 EP concentration of 164 ng L-1 at the N14 site. Hartbeespoort Dam catfish (Clarias gariepinus) and carp (Cyprinus carpio) did not bioaccumulate EPs in muscle. Efavirenz, nevirapine, carbamazepine, methocarbamol, bromacil and venlafaxine were detected in the highest concentrations in the Hartbeespoort Dam and uMngeni River estuary and therefore require operational monitoring in urban waters.