Distribution and risk assessment of trace metals in Leptodius exarata, surface water and sediments from Douglas Creek, Qua Iboe estuary
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Five trace metals in Leptodius exarata, epipellic sediments and surface water from an
intertidal ecosystem in Niger Delta (Nigeria) were investigated to evaluate their spatial
distribution, degree of contamination, ecological and health risks. Results show Cd
(cadmium), Cr (chromium), Ni (nickel), Pb (lead) and Zn (zinc) concentrations in sediment
ranged between 0.550 – 1.142, 9.57 – 15.95, 9.15 – 13.96, 2.00 – 8.90 and 91.5 – 121.6
mg/kg dw, respectively; while L. exarata tissue metal content vary from 0.162 – 0.931, 3.81
– 8.62, 4.45 – 17.15, 1.90 – 7.35, and 125.55 – 269.75 mg/kg, dw, respectively. The
bioconcentration factor ranking for trace metals followed the sequence Zn>Ni>Pb >Cr>Cd.
High biota to sediment accumulation factor (BSAF) in L. exarata reveals a sentinel metal
bioindicator. Sediments from most sites were uncontaminated to moderately contaminated
(geoaccumulation, Igeo > 0) with Cd and Zn associated with anthropogenic intrusions. Low
mean-ERM (effect range-median) and mean-PEL (probable effect level) quotients of
sediments are observed, indicating low–medium degree of contamination with 30% and 21%
probability of being toxic. The multi-metal potential ecological risk index (RI) for the
intertidal ecosystem indicates low–moderate risk. Health risks associated with crabs (L.
exarata) consumption are significant in children than adults.
Keywords
Q Science (General), QD Chemistry