Polycyclic aromatic hydrocarbons in surface sediments of a highly dynamic estuarine-coastal ocean continuum on the southwest coast of India: Seasonal distribution, source apportionment, and toxicological implications
Date
2025Author
Furtado, C.M.
Gireeshkumar, T.R.
Ramzi, A.
Sanyo, P.S.
Arya, K.S.
Emil John, C.R.
Muraleedharan, K.R.
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The contamination status and ecological implications of polycyclic aromatic hydrocarbons (PAHs) from the river and estuarine systems are widely reported. However, information on their seasonal dynamics, contamination status and environmental/human health implications in the coastal ocean is scanty. Surface sediments were collected from the Kochi Time Series (KoTS) transect (southeastern Arabian Sea) during August, October, and December 2020 and February 2021, covering monsoon, post-monsoon, and pre-monsoon seasons, and analysed for 16 PAHs congeners to investigate the seasonal distribution, sources, ecological risks, and human health implications. The concentrations followed the order: October (200.14 721.56 ng/g) > December (259.51 690.92 ng/g) > August (276.21 323.91 ng/g) > February (112.07 252.16 ng/g). The monsoon and post-monsoon discharge from the Cochin estuary significantly influenced the deposition of PAHs in the coastal sediments. The low molecular weight (LMW) PAHs, which are more susceptible to evaporation and degradation, dominated during the monsoon season, whereas relatively stable high molecular weight (HMW) PAHs were abundant during the pre-monsoon period. The high-water column temperature, solar radiation, and microbial activity during the pre-monsoon season may enhance the rate of PAH degradation, and LMW PAHs have a faster degradation rate, leading to a high abundance of HMW PAHs. The isomeric ratios and multivariate statistical analysis revealed the predominance of pyrogenic PAHs in the coastal sediments, with notable contributions from petrogenic sources. Ecological risk assessment based on the Sediment Quality Guidelines (SQGs) and Risk Quotient (RQ) values indicated chances of occasional negative impact on the benthic fauna. Furthermore, the human health risk assessment revealed a moderate carcinogenic risk, which demands immediate source reduction and adoption of remedial measures. The anthropogenic contaminants in the estuarine systems reach the coastal sediments during monsoon flooding, hampering the quantity and quality of coastal ecosystem services
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