|
Abstract:
|
Concentrations and distributions of trace metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) in surficial sediments of the Cochin
backwaters were studied during both monsoon and pre-monsoon periods. Spatial variations were in accordance with textural
charaterstics and organic matter content. A principal component analysis distinguished three zones with different metal accumulation
capacity: (i) highest levels in north estuary, (ii) moderate levels in central zone, and (iii) lowest levels in southern part.
Trace metal enrichments are mainly due to anthropogenic contribution of industrial, domestic, and agricultural effluents, whose
effect is enhanced by settling of metals due to organic flocculation and inorganic precipitation associated with salinity changes.
Enrichments factors using Fe as a normalizer showed that metal contamination was the product of anthropogenic activities. An
assessment of degree of pollution-categorized sediments as moderately polluted with Cu and Pb, moderately-to-heavily polluted
with Zn, and heavily-to-extremely polluted with Cd. Concentrations at many sites largely exceed NOAA ERL (e.g., Cu, Cr, and Pb)
or ERM (e.g., Cd, Ni, and Zn). This means that adverse effects for benthic organisms are possible or even highly probable. |