Contaminants of Emerging Concern in Botswana’s Aquatic Systems

There is growing concern about the prevalence and impact of Contaminants of Emerging Concern (CECs) worldwide. The environmental monitoring of CECs has, however, been limited in low-and-middle-income countries such as Botswana mainly due to the lack of advanced analytical instrumentation locally to analyse environmental samples. Here, high resolution mass spectrometry is used to identify chemical pollutants in environmental water samples acquired from Botswana. For the first time in Botswana, suspect and non-target techniques are employed to identify a range of CECs including pharmaceuticals, pesticides, and illicit drugs, and confirm that wastewater treatment plants are a major pathway to environmental pollution by chemicals.
Additionally, the results of an extensive sampling campaign conducted across disperse locations around Botswana is presented, providing a first insight into the distribution and prevalence environmental water contamination in the country. Using improved methodology and workflows, 114 chemical pollutants are identified, of which only 8 had been previously reported. These results are used to identify trends in the nature of the chemical pollutants detected in this work in a geographical context and, to propose a list of priority chemicals for future investigations.
Finally, higher-energy collision dissociation experiments were performed to determine detailed collisional energy dependent fragmentation pathways of a representative set of cannabinoids. The results provide information on the relative susceptibility of different cannabinoids to breakdown upon collisional activation, and allow for the identification of the major fragment ions associated with individual cannabinoids. Through analysis of laboratory prepared and previously analysed Botswana wastewater samples, it was found that major cannabinoid fragments could be identified using adapted suspect screening methods.
The findings reported here provide the first comprehensive overview of chemical pollution in Botswana’s fragile aquatic systems. Furthermore, they provide evidence to be used to inform and direct policy to mitigate pollution, and provide a clear direction for future research efforts.