25th International Meeting on Organic Geochemistry IMOG 2011

P-394
Polycyclic aromatic hydrocarbons in the Pichavaram Mangrove-
Estuarine sediments, South-eastern, India
Rajesh Ranjan 1,2 , Joyanto Routh 3,4 , AL Ramanathan 1 , J Val Klump 5
1 School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India, 2 Centre for
Environmental Sciences, Central University of Bihar, Patna, India, 3 Department of Earth Sciences, IISER-
Kolkata, Mohanpur, Mohanpur, West Bengal, India, 4 Department of Natural Sciences and Technology, MTM,
Örebro University, 70182 Örebro,, Örebro, Sweden, 5 Great Lakes WATER Institute, University of Wisconsin-
Milwaukee, Milwaukee, United States of America (corresponding author:joyanto.routh@iiserkol.ac.in)
Polycyclic aromatic hydrocarbons (PAHs) have
received much attention due to their carcinogenic and
mutagenic potential and ubiquitous presence [1].
They enter the aquatic environment via industrial
discharge, petroleum spills, combustion of fossil fuels,
and non-point source inputs such as agricultural and
urban runoff and atmospheric deposition [2]. Because
of their poor solubility and hydrophobic nature, PAHs
entering the environment preferentially adsorb to
particulates and accumulate in sediments.
The primary objectives of this study are to
investigate the 1) different sources of PAHs and its
concentration in the Pichavaram mangrove-estuarine
sediments and, 2) historical variations in PAH
deposition related to human activities. 16 PAHs listed
as ―priority pollutants‖ by the USEPA were
investigated in five 210 Pb dated sediment cores. The
study area was divided into three zones – the Vellar
estuary, mangrove forests and Coleroon estuary on
the basis of vegetation, land-use pattern, and
anthropogenic influence. Organic matter (OM) was
extracted using an accelerated solvent extractor and
the extracts were analyzed on a GCMS.
TOC concentration in sediments ranged from
0.06 to 1.97 % of dry weight. The mean ΣPAH
concentrations in mangrove and estuarine sediments
were 0.18 (±0.09) and 0.14 (±0.09) μg/g, respectively.
The PAH distribution trends indicate higher PAH
concentrations in mangrove than estuarine
sediments, and is influenced by the TOC content and
grain-size. However the PAH concentrations in
Pichavaram are below those of other mangrove
sediments [3]. Diagnostic PAH ratios and congener
pairs (Fluor(Fluor/Pyr) vs. Anth/(Anth+Phen) and
Fluor(Fluor/Pyr) vs. BaA/(BaA+Chry) show that most
PAHs are derived from a mixture of petrogenic
(automobile exhaust, oil spills from fishing boats)
sources with limited inputs from pyrogenic processes
involving combustion of wood and lignite/coal.
The ΣPAH deposition flux shows that deposition of
high molecular weight (HMW) PAHs has increased in
mangrove surface sediments, and is associated with
increase in anthropogenic activity. The ΣPAH flux
roughly follows the low molecular weight (ΣLMW)
PAH trend in estuarine sediments, whereas in
mangrove sediments the ΣPAH flux roughly follows
the high molecular weight (ΣHMW) PAH trend (Fig.
1). The relatively high flux for ΣHMW PAHs in
mangrove sediments could be explained by two
reasons. First, OM in mangrove sediments is mainly
derived from higher terrestrial matter (mainly in situ
mangrove vegetation) or riverine material. During
sediment transport due to solubilization and
volatilization the LMW PAHs degrade easily [4].
Secondly, biodegradation depletes preferentially the
LMW PAHs over HMW PAHs [5]. In the organic-rich
mangrove sediments there is more burrowing and
turning over of sediments and microbial activity than
estuarine sediments, and perhaps therefore, the LMW
PAHs in these sediments are degraded preferably.
Fig.1. Down core variations of PAHs flux (μg/cm 2 /yr)
References
[1] Flowers, L. et al. (2002) Polycyclic Aromatic Comp. 22,
811–821.
[2] Macdonald, R.W. et al. (2005) Sci. Tot. Environ. 342, 5–
86.
[3] Domínguez, C et al. (2010) Arch. Environ. Contam.
Toxicol. 59, 49-61.
[4] Christensen, E.R., Arora, S. (2007) Water Research, 41,
168-176.
[5] Brito, E.M.S. et al. (2005) Química Nova 28, 941–946.
523