Ecological risk assessment of metal pollutants in two agriculturally impacted estuaries

Aldwin Ndhlovu; Lucienne R D Human; Janine B Adams; Gavin M Rishworth; Chijioke Olisah; Thomas G Bornman

doi:10.1016/j.marpolbul.2023.115572

Ecological risk assessment of metal pollutants in two agriculturally impacted estuaries

Mar Pollut Bull. 2023 Oct:195:115572. doi: 10.1016/j.marpolbul.2023.115572. Epub 2023 Sep 25.

Authors

Aldwin Ndhlovu¹, Lucienne R D Human², Janine B Adams³, Gavin M Rishworth⁴, Chijioke Olisah⁵, Thomas G Bornman²

Affiliations

¹ Department of Zoology, Nelson Mandela University, Gqeberha 6031, South Africa; DSI/NRF Research Chair in Shallow Water Ecosystem, Institute of Coastal and Marine Research, Nelson Mandela University, Gqeberha 6031, South Africa; South African Environmental Observation Network, Elwandle Node, Gqeberha 6031, South Africa; Scientific Services, South African National Parks, Sedgefield 6573, South Africa. Electronic address: aldwynstav@gmail.com.
² Department of Botany, Nelson Mandela University, Gqeberha 6031, South Africa; South African Environmental Observation Network, Elwandle Node, Gqeberha 6031, South Africa.
³ Department of Botany, Nelson Mandela University, Gqeberha 6031, South Africa; DSI/NRF Research Chair in Shallow Water Ecosystem, Institute of Coastal and Marine Research, Nelson Mandela University, Gqeberha 6031, South Africa.
⁴ Department of Zoology, Nelson Mandela University, Gqeberha 6031, South Africa; DSI/NRF Research Chair in Shallow Water Ecosystem, Institute of Coastal and Marine Research, Nelson Mandela University, Gqeberha 6031, South Africa.
⁵ Department of Botany, Nelson Mandela University, Gqeberha 6031, South Africa; DSI/NRF Research Chair in Shallow Water Ecosystem, Institute of Coastal and Marine Research, Nelson Mandela University, Gqeberha 6031, South Africa; South African Environmental Observation Network, Elwandle Node, Gqeberha 6031, South Africa; Research Centre for Toxic Compounds in the Environment (RECETOX), Faculty of Science, Masaryk University, Kamenice 5/753, 625 00 Brno, Czech Republic.

PMID: 37757718
DOI: 10.1016/j.marpolbul.2023.115572

Abstract

A focused diagnosis of ecosystem health in two South African estuaries (Kromme and Gamtoos) was conducted. Four pollution indices were used, i.e., geoaccumulation (Igeo), ecological risk (RI), contamination factor (CF) and pollution load index (PLI), to assess toxicity levels of metal contaminants in relation to background values. The Igeo results (11.1 %) can be classified as contaminated, with Cd, the only element with high values in both estuaries. Likely sources (herbicides, pesticides) of Cd are used in the agricultural dominated catchments. There was a high concentration of Mn (13.4 ± 2.51 and 12.3 ± 1.13 μg·g^-1) and Fe (1289 ± 243 and 1291 ± 130 μg·g^-1) at site 4 for Gamtoos and Kromme estuary respectively compared to the other metal elements. Although results indicate low metal contamination, with increasing global anthropogenic pressure, continuous monitoring should be prioritised to assist in managing estuarine systems that support a wide range of socio-economic and ecosystem services.

Keywords: Biomonitoring; Contamination; Gamtoos Estuary; Kromme Estuary; Pollution indices.