Spatial and seasonal trends of trace metals in the surficial sediments from off Kochi - Geochemistry and environmental implications.

Fifty four sediment samples representing pre and post-monsoon seasons were collected along a transect from off Kochi, lying between the latitudes 9°57'59.5″-9°54'30.4″ and longitudes 76°11'7.04″-75°38'50.3″ of the South eastern Arabian Sea. The present study investigates the levels of trace metals (Zn, Cd, Pb, Cu, Fe, Ni, Mn, Co and Cr), total organic carbon (TOC), total inorganic carbon (TIC), elemental composition and grain size to assess the extent of environmental pollution and to discuss the distribution of these trace metals in the surficial sediments. Sediment pollution assessment was done using the Contamination factor (C.F), Geoaccumulation Index (Igeo), Enrichment Factor (EF), and Pollution Load Index (PLI). The majority of trace metals analysed in this study exhibited the highest concentrations at stations 1, 2 and 3 where the land-based anthropogenic input was found to be maximum.

Phthalic acid esters - A grave ecological hazard in Cochin estuary, India.

Distribution and ecological risks of Phthalic acid esters (PAEs) are poorly studied in estuarine environments in India. An attempt is made to chart the sources and assess the ecological risk of six PAE congeners (∑6PAEs), present in dissolved and particulate forms in a tropical ecosystem (Cochin Estuary, India). Terrestrial input, as attested by a clear seasonality with substantial enrichment during monsoon (2-28 µg/L and 31-1203 µg/g; dissolved and particulate PAEs respectively) and post-monsoon (1-7 µg/L and 7-321 µg/g; dissolved and particulate PAEs respectively), was identified as the primary source. DnBP (di-n-butyl phthalate) and DEHP (diethylhexyl phthalate) were found to be the dominant species except for dissolved PAEs at pre-monsoon season. Statistical analysis identified two major clusters, in the ∑6PAEs, composed of medium to high molecular weight PAEs (derived from plastic products) and low molecular weight PAEs (derived from cosmetic products). Calculated Risk Quotient (RQ) indicated values indicated moderate to high ecological risk for DnBP and DEHP congeners is a grim pointer to their detrimental effects on human health through consumption of contaminated organisms. Although substantial enrichment of suspended matter gets flushed out of the estuary during monsoon, there is a net PAE accumulation in the estuary during post-monsoon following an increased sedimentary restitution. Data of PAEs generated herein raises a challenge for immediate enactment of statutory legislation to curb and regulate hazardous contamination of estuaries by phthalic acid esters.

Distribution and contamination status of phthalic acid esters in the sediments of a tropical monsoonal estuary, Cochin - India.

Phthalic acid esters (PAEs) are a group of endocrine-disrupting chemicals listed as priority pollutants by United States Environmental Protection Agency (USEPA, 2009). This study provides baseline information on seasonal distribution and contamination status of six phthalic acid esters (∑6PAEs) in sediments of a tropical estuary (Cochin-India). In general, the sediments accumulated more PAEs during the post monsoon (mean 2325 ngg-1; between 1402 and 3121 ngg-1) and monsoon (mean 1372 ngg-1; between 331 and 4015 ngg-1) periods indicating land run off as the major transport pathway. Moderate run off and comparatively high residence time lead to effective sorption and settling of PAEs in the surface sediments during post monsoon season. Despite a high discharge of PAEs in to the water column, their deposition on to the sediments occurs at a lower rate during monsoon than that post monsoon season. PAEs were (mean 810 ngg-1; between 44 and 1722 ngg-1) lowest in pre monsoon season. The pre monsoon season is characterized by a minimal runoff consequent to the trapping of these organic pollutants in the river catchment area. The mid and high molecular PAEs (DEHP-Di ethylhexyl phthalate, BBP-Benzyl butyl phthalate and DnBP-Di-n-butyl phthalate) were the dominant congeners relative to the low molecular weight congeners (DMP-Dimethyl phthalate and DEP-Diethyl phthalate). DEHP and BBP levels exceeded permissible risk levels indicating a serious ecological hazard to the estuarine ecosystem.

Dynamics of polycyclic aromatic hydrocarbons (PAHs) in surface sediments of Cochin estuary, India.

Polycyclic aromatic hydrocarbons (PAHs) showed significant seasonal dynamics in surface sediments of a tropical ecosystem (Cochin estuary, south west coast of India). Concentrations ranged from 304 to 5874ngg-1 in pre-monsoon, 493 to 14,149ngg-1 in monsoon, and 194 to 10,691ngg-1 in post-monsoon. The estuary was moderately contaminated with low molecular weight PAH fractions, which increased rapidly during the monsoon season indicating land/river runoff as the major transport pathway. The dominance of 2-3 ring fractions in the PAH indicated petrogenic and low temperature combustion processes as major sources, while the very low levels of 5-6 ring components indicated low contribution from pyrolytic sources. Low molecular weight fractions were higher in concentration than the Effective Range-Median (ERM) levels, whereas high molecular weight PAHs were lower than the Effective Range-Low values (ERL). Calculated carcinogenic toxicity equivalents (TEQ) values ranged from 1 to 971ngg-1 in the surface sediments.