Occurrence and risk assessment of organic micropollutants in freshwater systems within the Lake Victoria South Basin, Kenya

https://doi.org/10.1016/j.scitotenv.2020.136748Get rights and content

Highlights

  • First comprehensive identification of 78 OMPs in western Kenya

  • Pharmaceuticals, pesticides and biocides most frequently detected

  • First data on plasticizers in Kenyan surface water systems up to 6.5 μg L−1

  • High acute and chronic risk for toxicity in crustaceans

  • Diazinon, bendiocarb and carbendazim prioritized for regular monitoring

Abstract

The unintended release of chemicals to the environment has led to global concern on water quality prompting widespread research on the occurrence of these compounds in water. While increasing information on organic micropollutants (OMPs) in European water resources is available, there is still limited information on the occurrence of OMPs in African water systems. In this study, a multi-residue analysis covering 428 chemicals using liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS) was performed on water samples collected from 48 surface water sites within the Lake Victoria South Basin, Kenya. A total of 75 compounds including pharmaceuticals, personal care products (PPCPs), pesticides, and industrial chemicals were detected and an additional three compounds (nevirapine, lamivudine and adenosine) were identified through suspect screening. Four compounds including diphenhydramine, simazine, triethylphosphate and acetyl-sulfamethoxazole (A-SMX) were detected in >80% of the sites showing their ubiquitous nature in the study area. Individual compound concentrations were detected up to 24 μg L−1. Concentrations above 1 μg L−1 were also reported for triethylcitrate, N-ethyl-o-toluenesulfonamide, hexazinone, nevirapine, adenosine and carbendazim. While crustaceans were potentially the taxon at risk for acute toxicity (toxic unit (TU) up to 2) with diazinon driving this risk, lower but substantial acute risk (TU 0.5) was observed for algae. Chronic risks were observed in 11 sites for algae (TU > 0.02) and in 5 sites for fish (TU > 0.01). A total of 16 compounds were prioritized based on frequency and extent of the exceedance of thresholds for acute and chronic risks to algae, crustaceans and fish and another 7 compounds prioritized by applying lowest Predicted No-Effect Concentrations (PNEC). Based on these indicators, this study provides candidate priority compounds for monitoring, assessment and abatement in western Kenya.

Introduction

The widespread and intensive use of chemicals such as pesticides, pharmaceuticals and personal care products (PPCPs) has given rise to concern on their occurrence in and impact on aquatic ecosystems (Posthuma et al., 2019). There has been an increase in the use of pesticides and PPCPs due to the increasing population and diseases especially in developing countries (Bernhardt et al., 2017; Peng et al., 2018). In this context, Kenya being a developing country, faces great challenges to cater for food, clean water and health needs of its growing population. Agriculture is a main economic branch contributing >70% of Kenya's foreign trade which increases 10% on average annually (Moya et al., 2019). This has led to an increased demand for plant protection products. Between 2006 and 2010, the Ministry of Environment, Water and Natural resources reported approximately 36 thousand tons of pesticide importation into Kenya which increased to 54 thousand tons by 2013 (Loha et al., 2018). In addition, (re)emergence of diseases and epidemics (Berger et al., 2010) has led to increased use of pharmaceutical products in the country and to an increased release of these compounds into the environment. Many organic micropollutants (OMPs) are persistent in the environment including carbendazim, clothianidin, diuron and atrazine with several studies showing that exposure to these compounds results in acute and chronic effects to aquatic organisms (Ccanccapa et al., 2016; Liess and Von Der Ohe, 2005; Shahid et al., 2018; Velki et al., 2019).

Monitoring of emerging OMPs has been increasingly done in the western world; however, there is still a big lack of data for Africa (Aus der Beek et al., 2016; Fekadu et al., 2019; Madikizela et al., 2017). Most studies on water quality monitoring in Africa are based on environmental or drinking water guidelines which cover only few OMPs (Gwenzi and Chaukura, 2018). The lack of state-of-the-art analytical equipment to detect concentrations in the ng L−1 range is a major obstacle to monitoring of hazardous environmental contamination in many developing countries. Although the occurrence of some pesticides in environmental matrices in Kenya has been monitored since 1987 (Kahunyo et al., 1988), the compounds analyzed were generally low in number. Only very few studies have been performed in Kenyan water systems characterizing pharmaceutical pollution patterns in surface waters. These studies focused on a few pharmaceuticals (Bagnis et al., 2020; K'oreje et al., 2012, K’oreje et al., 2016, K'oreje et al., 2018; Kimosop et al., 2016; Ngumba et al., 2016) and only three studies (Bagnis et al., 2020; K'oreje et al., 2018; Ngumba et al., 2016) reported potential risks on aquatic organisms based on the measured environmental concentrations.

To reduce this knowledge gap, the present study focused on the assessment of surface waters including rivers, drainage channels and dams to obtain information on the extent of pesticides, PPCPs and industrial compound pollution within the Lake Victoria South Basin (LVSB) in Kenya. The aim of this study was to (1) determine the level of OMPs pollution in various surface water systems within LVSB (2), to perform suspect screening for a comprehensive characterization of multi-residue pollution, (3) to undertake risk assessment on aquatic organisms based on toxic units (TU) and (4) for the first time, to prioritize compounds for regulation and monitoring in Kenya.

Section snippets

Chemicals

LC-MS grade methanol, formic acid and ammonium formate were obtained from Honeywell, while LC-MS grade water was purchased from Thermo-Fisher. Analytical standards were obtained from various suppliers and at least of 97% purity. More information on the compounds analyzed is presented in supplementary information (Table SI-1).

Study area and sampling

The study was performed within the LVSB, Kenya (Fig. 1) covering Kericho, Kisumu, Kisii, Nyamira, Migori, Narok and Homabay counties. LVSB has an estimated area of 21,720 km

Results and discussion

The results from the analysis of general water quality parameters are given in the supplementary information (Table SI-9).

Conclusions

The present study has provided a comprehensive identification and risk assessment of emerging OMPs in freshwater systems in rural areas within the Lake Victoria South Basin for three representative organism groups including crustaceans, algae and fish. Particularly high concentrations (> 1 μg L −1) were detected for some pharmaceuticals and pesticides with A-SMX being reported at 24 μg L −1. Suspect screening supported the detection of two common antiretroviral drugs used in the first line of

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was supported by the Deutsche Forschungsgemeinschaft (DFG), Germany under project SENTINEL [grant number LI 1708/4-1, BR 2931/3-1, HO 3330/12-1]. We are grateful to Paul Ouma for the support during sampling and Hubert Schupke for LC-HRMS analysis. A free academic license of JChem for Office (Excel) was used for structure based property calculation and Marvin was used for drawing, displaying and characterizing chemical structures, Marvin/Jchem 17.21.0, 2019 ChemAxon (//www.chemaxon.com

References (53)

  • N.A. Munz et al.

    Pesticides drive risk of micropollutants in wastewater-impacted streams during low flow conditions

    Water Res.

    (2017)
  • S. Ncube et al.

    Environmental fate and ecotoxicological effects of antiretrovirals: a current global status and future perspectives

    Water Res.

    (2018)
  • E. Ngumba et al.

    Occurrence of selected antibiotics and antiretroviral drugs in Nairobi River Basin, Kenya

    Sci. Total Environ.

    (2016)
  • Y. Peng et al.

    Screening hundreds of emerging organic pollutants (EOPs) in surface water from the Yangtze River Delta (YRD): occurrence, distribution, ecological risk

    Environ. Pollut.

    (2018)
  • J.B. Sprague

    Measurement of pollutant toxicity to fish. II. Utilizing and applying bioassay results

    Water Res.

    (1970)
  • P.C. von der Ohe et al.

    A new risk assessment approach for the prioritization of 500 classical and emerging organic microcontaminants as potential river basin specific pollutants under the European Water Framework Directive

    Sci. Total Environ.

    (2011)
  • G.L. Wei et al.

    Organophosphorus flame retardants and plasticizers: sources, occurrence, toxicity and human exposure

    Environ. Pollut.

    (2015)
  • T. Aus der Beek et al.

    Pharmaceuticals in the environment - global occurrences and perspectives

    Environ. Toxicol. Chem.

    (2016)
  • T. Backhaus et al.

    Predictive environmental risk assessment of chemical mixtures: a conceptual framework

    Environ. Sci. Technol.

    (2012)
  • S. Bagnis et al.

    Characterization of the Nairobi River catchment impact zone and occurrence of pharmaceuticals: Implications for an impact zone inclusive environmental risk assessment

    Sci. Total Environ.

    (2020)
  • J.B. Belden et al.

    How well can we predict the toxicity of pesticide mixtures to aquatic life?

    Integr. Environ. Assess. Manag.

    (2007)
  • M. Berger et al.

    Strengthening Pharmaceutical Innovation in Africa

    (2010)
  • E.S. Bernhardt et al.

    Synthetic chemicals as agents of global change

    Front. Ecol. Environ.

    (2017)
  • S. Böcker et al.

    Towards de novo identification of metabolites by analyzing tandem mass spectra

    Bioinformatics

    (2008)
  • S. Böcker et al.

    SIRIUS: decomposing isotope patterns for metabolite identification

    Bioinformatics

    (2009)
  • J.L. Bouldin et al.

    Assessment of diazinon toxicity in sediment and water of constructed wetlands using deployed Corbicula fluminea and laboratory testing

    Arch. Environ. Contam. Toxicol.

    (2007)
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