Plastic pollution in coastal ecosystems is of utmost concern, especially in population-dense and metropolitan cities such as Lagos, Nigeria. The study aimed to map plastic debris hotspots analyse water quality indices, and target plastic-related pollutants in drainage channels that empty into the Lagos Lagoon, Nigeria. Drainage channels were purposively sampled across 4 districts/zones in Lagos characterised by proximity to anthropogenic inputs and population density. Utilizing Sentinel-2 satellite images, a plastic debris detection technique was developed using the Normalized Difference Water Index (NDWI) and Normalized Difference Built-up Index (NDBI). Water quality indices and target pollutants (temperature, dissolved oxygen, pH, VOCs, Pb, Cd) were analysed using in situ water quality test instruments and standards methods respectively. Fieldwork, drone images and a 2018 NASA plastic debris dataset were used to evaluate the performance of the developed technique. The results were promising as the technique successfully identified plastic debris. After that, plastic debris hotspot maps were created using GIS techniques. An automatic plastic debris detection method was also developed using drone images and machine learning techniques. The YOLOv8 model was utilized for plastic debris detection and classification. This study contributes to pollutant monitoring in coastal ecosystems for evidence-informed interventions through autonomous detection methods, machine learning and Geospatial techniques.

Authors:

Ngozi Oguguah, Nigerian Institute for Oceanography and Marine Research  (ngozimoguguah@yahoo.com)

Temitope Sogbanmu, Ecotoxicology and Conservation Unit, Department of Zoology, Faculty of Science, University of Lagos, Akoka, Lagos, Nigeria  (tsogbanmu@unilag.edu.ng)

Jane Chukwudebelu, Environmental Technology Division, Department of Chemical Fibre and Environmental Technology, Federal Institute of Industrial Research Oshodi Lagos, Nigeria.  (adadebelu@yahoo.com)

Adedoyin Lasisi, Environmental Impact Assessment Unit, Environmental Assessment Department, Office of Environmental Services, Lagos State Ministry of the Environment and Water Resources, Alausa-Ikeja, Lagos, Nigeria.  (ladedoyin@gmail.com)

Atijosan Abimbola, Advance Space Application Laboratory, Obafemi Awolowo University Campus, Ile-Ife.  (bimbo06wole@yahoo.com)

Jian Wan, College of Engineering and Physical Sciences, Aston University, Birmingham B4 7ET, UK  (j.wan3@aston.ac.uk)

Kizito Udeinya, University of Nigeria Nsukka, Enugu State, Nigeria  (kUdeinya@gmail.com)

Denzel Ugochukwu Oguguah, University of Nigeria, Nsukka, Enugu State, Nigeria  (Doguguah@gmail.com)

Daniel Oluwaleke Biaoku, Ekiti State University, Ado-Ekiti, Ekiti State, Nigeria  (biaokudaniel173@gmail.com)