Speakers
Description
Assessing the Effect of Illegal Mining on Selected Rivers in Obuasi Using Daphnia Magna and Lemna Minor
Yaw Mensah Quansah *,1, Lyndon Nii Adjiri Sackey1, Isaac Ayew Aidoo1
1Department of Environmental Science, Kwame Nkrumah University of Science and Technology
*Corresponding Author: Yaw Mensah Quansah, paulquansah98@gmail.com, +233 552330409
Presentation format preferred: Oral Presentation
Subtheme: Climate Resilience, Environmental Sustainability, and Food Systems
Abstract
Illegal mining activities pose threats to aquatic ecosystems through the release of toxic substances which affect the aquatic ecosystem. This is a growing concern because of the rise of illegal mining in curtaining parts of Ghana. Therefore, this research seeks to assess the effect of illegal mining on selected rivers at Obuasi in the Ashanti Region using Daphnia magna and Lemna minor. Obuasi was selected as the study area because it is an illegal mining hotspot. Three rivers were randomly selected from Obuasi; Kwabrafoso river (KB), Pompom River (PO) and Diewuo river (DE) to assess their level of toxicity to aquatic organisms. The heavy metals were analysed using the Agilent 4210 Microwave Plasma Atomic Emission Spectrometer (MP-AES) and the physicochemical properties by using the OHAUS Starter 3100 meter. Lemna minor and Daphnia magna were used as the test organisms following OECD 211 and OECD 202 protocols respectively. The pH of all river samples was alkaline (7.10 – 7.49) and within the World Health Organization (WHO) permissible limit. Kwabrafoso had the highest EC (1.53 mS/cm), TDS (748.22 mg/L), and salinity (0.76 psu), while Pompom had the lowest. Turbidity was high across all rivers, with Diewuo recording the highest (613.67 NTU) and Kwabrafoso the lowest (324.79 NTU), all exceeding the WHO standard (<100 NTU). Kwabrafoso showed the highest concentrations of Zn (0.46 mg/L), Pb (0.18 mg/L), and As (0.62 mg/L. Bioaccumulation showed Zn and As as the most bioavailable metals to daphnia. IC10 and EC50 were measured in the toxicity bioassays for Lemna minor and daphnia magna, respectively ranging from (4.90 mg/L – 11.48 mg/L) for IC10 and (15.15 mg/L - 31.9 mg/L) for EC50. All the river samples showed confirmed toxicity, indicating the impact of illegal mining to aquatic ecosystem. This highlights the need for monitoring and strong regulations to protect aquatic ecosystems.
Keywords: Illegal Mining, Ecological effects, Freshwater, Heavy metals, Bioaccumulation, Acute toxicity