Integrated Ecological Pollution Impact of Selected Heavy Metals in Microplastics in Sediments, Rivers State, Nigeria

Abstract

This study evaluated the concentrations of heavy metals (Ni, Cr, Fe, Hg, Cd, Cu, Pb, and Mn) adsorbed to microplastics in sediments (MCPS) along Woji, Okujagu, and Elelenwo creeks in Port Harcourt, Nigeria, during the wet and dry seasons. Monthly sediment samples were collected from December 2020 to May 2021 during low tide events. The concentrations of metals in the microplastics in sediment (MCPS) were analysed using GBC Avanta PM A6600 Flame Atomic Absorption Spectrophotometer (FAAS) and compared to sediment quality guidelines (TEL and PEL) to assess the potential ecological risks and contamination levels. In the dry season, Woji creek showed the highest concentrations of Ni, Cr, Fe, and Cu in MCPS, while Hg levels were more significant in Woji, with a toxicity response factor (T_r) of 30. Conversely, Elelenwo exhibited the lowest metal concentrations for most of the metals. The calculated geoaccumulation index (I_geo) and contamination factor (CF) revealed that Woji and Okujagu creeks were moderately contaminated with Fe and Cu, while Hg concentrations indicated a high ecological risk. The potential ecological risk index (PERI) showed significant contributions from Hg and Cu, particularly at Woji and Okujagu. During the wet season, Ni, Cr, Fe, and Cu concentrations decreased, with the lowest concentrations observed in Elelenwo. However, the PERI showed no significant risks from Hg, Cu, or Mn, as these metals were present in lower quantities. These findings underscore the need for continued monitoring of metal contamination, and highlight the potential ecological and health risks posed by heavy metal-laden microplastics in estuarine environments.