Health risk indices and zooplankton‑based assessment of a tropical rainforest river contaminated with iron, lead, cadmium, and chromium
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natureresearch
Abstract
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Oil exploration’s devastation on health and the environment may far outweigh its economic benefits.
An oil spill occurred at Egbokodo River in Delta State, Nigeria, thereby polluting the land and
water bodies. The study was therefore aimed at evaluating the impacts of iron, lead, cadmium, and
chromium on the zooplankton community structure of Egbokodo River and the potential health
risks. Zooplankton and surface water samples were collected to investigate the concentrations of
trace metals and zooplankton abundance. The associated carcinogenic and non-carcinogenic effects
of the metals in the water were analyzed. Trace metal concentrations in the surface water were
determined using atomic absorption spectroscopy (Philips model PU 9100) and zooplankton samples
were collected using a hydrobios plankton net (mesh size 25 μm). Total petroleum hydrocarbons
(TPH) and oil and grease (OG) were determined using Agilent 7890B gas chromatography coupled to
flame ionization detector (GC-FID) and volumetric analysis respectively. The trend of the abundance
of zooplanktons cross the river was 18 individuals (Station A) < 100 individuals (Station B) < 155
individuals (Station C). Cyclopoida proved to be the most resilient to the impacts of the oil spill. On
a taxa basis, the order of abundance among Calanoida, Cyclopoida, Cladoceran, and Harpacticoida
was Station C > Station B > Station A, except in Amphipoda where Station B > Station C > Station
A was observed. Iron and lead posed significant carcinogenic risks that are liable to be inflicted by
the ingestion of the water. The cumulative non-carcinogenic health risk in the male was the only
significant (> 1) among the age groups. Total petroleum hydrocarbons (TPH), oil and grease (OG),
iron, and lead had notable impacts on the general abundance of zooplankton in the aquatic habitat.
The dominance of the Cyclopoida in the river buttressed the impact of the oil spill which warrants
a prompt remediation measure. The pollution had notable ecological impacts on the zooplankton
community structure of the aquatic habitat. The adults in the nearby human populations are liable
to elicit carcinogenic health challenges associated with lead and iron ingestion. The males are at
risk of non-carcinogenic illnesses which are associated with the combined toxicity effects of all the
metals. The study suggests that the pollution in Egbokodo River was validated by the dominance of
the Cyclopoida in the aquatic habitat. The study confers bioindicator reputation on the Cyclopoida for
future biomonitoring studies.
Keywords
QC Physics, QH301 Biology