METAL POLLUTION INDEX AND GIS MODELLING OF SOME TRACE METALS IN WATER, SEDIMENT AND Lutjanus dentatus FROM QUA IBOE RIVER ESTUARY, SOUTH-SOUTH, NIGERIA

One of the largest crude oil production facilities in the Niger Delta region of Nigeria is located in the lower reach of Qua Iboe river estuary. It has history of frequent oil spills and pipeline vandalization which results in severe effect on the aquatic ecosystem. This study was carried out to determine the geometric mean of the investigated metals in each location and mapping of trace metal pollution index levels based on sampled data and its classification into risk areas using geographic information system (GIS). The metal pollution index (MPI) of the investigated metals was calculated using model proposed by USEPA while the pollution maps showing the visual representation of the pollution status of different sampling sites was created using GIS modeling technique of Arc map 9.2. The range for the MPI values investigated in the dry season was as follows: water (0.180-0.372), sediment (0.55-2.98), Lutjanus dentatus (0.102-0.295) while the result for the wet season was: water (0.027-0.324), sediment (0.65-2.95), Lutjanus dentatus (0.036-0.273). The sampling sites close to the oil processing facilities recorded higher total metal content (MPI) values compared to the control sites. Risk assessment from the pollution map revealed very high risk zones around Douglas and Stubbs creeks. The findings can be linked to the presence of anthropogenic pollution sources in these locations. Therefore, proper clean-up of the lower reach of Qua Iboe River estuary to minimize the cumulative health risk from trace metal pollution in the environment is recommended.