Evaluation of the Organic Pollution Status of some Rivers in Edo State using Palmer’s Pollution Index

Abstract

Freshwater bodies are susceptible to organic contamination, which is mostly caused by human activities, and these activities can change the composition of the algal community in the receiving water bodies. Physico-chemical evaluation techniques can be quite costly and evaluate water bodies based on a variety of parameters. Biological assessments are sensitive to variations in water quality and provide less expensive options than conventional techniques. Palmer's algal pollution index was used in this study to evaluate the organic pollution condition of ten rivers in Edo State. In October 2020, samples of phytoplankton were taken for study from 10 distinct rivers in Edo State. The samples were examined microscopically and identified using relevant taxonomic texts. Out of the 20 algal genera identified by Palmer, sixteen (16) pollution-tolerant algae genera were implicated in this study. These were distributed between the divisions Bacillariophyta (Gomophonema, Melosira, Navicula, Nitzchia, and Synedra), Chlorophyta (Ankistrodesmus, Closterium, Pandorina, Scenedesmus, and Stigeoclonium), Cyanophyta (Microcycstis, Oscillatoria, and Phormidium) and Euglenophyta (Euglena, Lepocinclis, and Phacus). The phytoplankton data were used to calculate Palmer's algal pollution index, and the results revealed that 60% of the sampled rivers were in the confirmed high organic pollution range, 10% were in the probable high organic pollution range, and 30% were in the moderate pollution range. Using QGIS's Inverse Distance Weightage (IDW) Interpolation function, the organic pollution plot for the research area was created based on the findings of Palmer's Algal Pollution Index. Overall, this study showed that the rivers have a high level of organic enrichment and suggested routine river monitoring in order to develop suitable management plans for the preservation of these rivers.