Distribution, Enrichment and Ecological Risk Assessment of Six Elements in Bed Sediments of a Tropical River, Chottanagpur Plateau: A Spatial and Temporal Appraisal ()
ABSTRACT
Distribution
and enrichment of six elements (iron, zinc, copper, lead, cadmium and
manganese) in surface bed sediments, collected from seventeen selected
locations during pre-monsoon and postmonsoon periods, of the tropical
Chottanagpur plateau river Subarnarekha along with the ecological risks
involved were investigated. Owing to the rich occurrence of mineral resources,
the Subarnarekha river basin has a large scale presence of industrial and
mining units especially in the Indian State of Jharkhand. An assessment, which
involved examining distribution pattern of elements, comparative studies with
sediment quality guidelines (SQGs) and geochemical background values and a
sequential and integrated index analyses approach (containing contamination
factor (CF), pollution load index (PLI), contamination degree (CD), enrichment
factor (EF), geo-accumulation index (Igeo) and potential ecological risk index
(PERI)), was followed to estimate enrichment and risks of elements in the bed
sediments. Sediments collected from areas having abundance of population,
industrial conglomerates and mining units recorded elevated element concentrations,
which exceeded SQGs, and significantly higher values of CF, CD, PLI, EF, Igeo
and PERI. Cadmium demonstrated surprising regularity in its enrichment;
contributed most to the ecological risks; and high toxicity risks due to
cadmium exceeded 64% of the sites. Moreover, chronic exposures of other
elements would also lead to similar ecological risks. In addition to revealing
potential ecological risks due to cadmium and other elements our investigation
markedly highlighted anthropogenic control over sediment quality deterioration
and some immediate sediment quality management strategies are needed to
remediate and control river bed contamination.