Assessment of Toxicity Potential of Sedimentary PAHS from Refome Lake, South-East Nigeria over the Last Century

摘要

In this study, toxic equivalent factors and sediment quality guidelines were employed for the assessment of toxicity potential of PAHs in 2 sediment cores collected from the center (RC) and shoreline (RS) of Reforme lake, SE Nigeria over the last ~1 century. Boundary cross plots of isomeric ratios such as Ant/Ant + Phe (>0.1) vs. Fl/Fl + Pyr (>0.4) and BaA/BaA + Chry (>0.35) vs. Icdp/Icdp + Bper (>0.2) indicated biomass combustion/domestic coal utilization as the main sources of PAHs input. The result revealed toxicity unit indices (TU1, 1.22 - 1.57) for the two cores were above the thresholds of no effect. The highest TU1 value found in the near-bottom layer (RS5, 20 - 25 cm) of the RS corresponding to geological time-frame ~1930-1947 coincided with the period of inhabitation by the European settlers along the lake’s catchments when coal or coal products utilization for domestic and recreational purposes was at its peak. On the other hand, TU2 values were <1 at all depth intervals, revealing unlikely PAH effects to resident organisms. Total toxicity equivalency factors (TEqFs) for the surface sediment of RS and RC were 9.29 ng/g TEqFs and 9.16 ng/g TEqFs, respectively, and indicated that more attention should be paid to BaPyr accumulation in the lake’s sediment.