Organophosphate pesticides in South African eutrophic estuaries: Spatial distribution, seasonal variation, and ecological risk assessment

Chijioke Olisah; Gletwyn Rubidge; Lucienne R D Human; Janine B Adams

doi:10.1016/j.envpol.2022.119446

Organophosphate pesticides in South African eutrophic estuaries: Spatial distribution, seasonal variation, and ecological risk assessment

Environ Pollut. 2022 Aug 1:306:119446. doi: 10.1016/j.envpol.2022.119446. Epub 2022 May 9.

Authors

Chijioke Olisah¹, Gletwyn Rubidge², Lucienne R D Human³, Janine B Adams⁴

Affiliations

¹ DSI/NRF Research Chair, Shallow Water Ecosystems, Nelson Mandela University, PO Box 77000, Gqeberha, 6031, South Africa; Department of Botany, Institute of Coastal and Marine Research (CMR), Nelson Mandela University, PO Box 77000, Gqeberha, 6031, South Africa; Department of Chemistry, Nelson Mandela University, PO Box 77000, Gqeberha, 6031, South Africa. Electronic address: olisah.chijioke@gmail.com.
² Department of Chemistry, Nelson Mandela University, PO Box 77000, Gqeberha, 6031, South Africa.
³ Department of Botany, Institute of Coastal and Marine Research (CMR), Nelson Mandela University, PO Box 77000, Gqeberha, 6031, South Africa; South African Environmental Observation Network (SAEON) Elwandle Coastal Node, PO Box 77000, Gqeberha, 6031, South Africa.
⁴ DSI/NRF Research Chair, Shallow Water Ecosystems, Nelson Mandela University, PO Box 77000, Gqeberha, 6031, South Africa; Department of Botany, Institute of Coastal and Marine Research (CMR), Nelson Mandela University, PO Box 77000, Gqeberha, 6031, South Africa.

PMID: 35550133
DOI: 10.1016/j.envpol.2022.119446

Abstract

The seasonal variation, spatial distribution, and ecological risks of thirteen organophosphate pesticides (OPPs) were studied in the Sundays and Swartkops estuaries in South Africa. Ten pesticides were detected in surface water samples from both estuaries, while all OPPs were detected in sediments. The highest concentration of OPPs (18.8 μg pyrazophos L^-1) was detected in surface water samples from Swartkops Estuary, while 48.7 μg phosalone kg^-1 dw was the highest in sediments collected from Sundays Estuary. There was no clear seasonal pattern in OPPs occurrence in surface water from both systems. However, their occurrence in sediments was in the following order: winter > autumn > summer > spring, perhaps indicating major pesticide input in the winter seasons. Results from ecological risk assessment showed that pyraclofos and chlorpyrifos (CHL) in surface water from both systems are respectively likely to cause high acute and chronic toxicity to fish (risk quotient - RQ > 1). For sediments of both estuaries, the highest acute and chronic RQs for fish were calculated for isazophos and CHL respectively. The majority of the detected OPPs in sediments posed potential high risks to Daphnia magna from both systems. These results suggest that these aquatic organisms (fish, and Daphnia), if present in the studied estuaries, can develop certain forms of abnormalities due to OPP exposure. To this end, proper measures should be taken to reduce OPP input into the estuarine systems.

Keywords: Aquatic organisms; Ecotoxicology; Organic contaminants; Sundays Estuary; Swartkops Estuary.

MeSH terms

Animals
Chlorpyrifos*
Daphnia
Environmental Monitoring / methods
Estuaries
Fishes
Geologic Sediments
Insecticides*
Organophosphorus Compounds
Pesticides* / analysis
Risk Assessment
Rivers
Seasons
South Africa
Water
Water Pollutants, Chemical* / analysis

Substances

Insecticides
Organophosphorus Compounds
Pesticides
Water Pollutants, Chemical
Water
Chlorpyrifos