# Polycyclic aromatic hydrocarbons in sediments of Hooghly River Mouth and Sundarbans Wetland, West Bengal, India

## TL;DR

This study found high levels of harmful PAHs in sediments from the Hooghly River and Sundarbans Wetland in India, with the river showing much higher contamination and a need for urgent action.

## Contribution

The study provides new data on PAH contamination levels and sources in understudied Indian river and wetland sediments.

## Key findings

- PAH levels in the Hooghly River were significantly higher than in the Sundarbans Wetland, with a hotspot reaching 13,785 ng/g.
- Pyrogenic sources were identified as the main contributors to PAH contamination in the region.
- The heavy PAH pool (4-6 rings) was six times more concentrated than the light pool (2-3 rings).

## Abstract

The study compared the pollution level of 16 priority polycyclic aromatic hydrocarbons (PAHs) in the superficial sediments of the low stretch of the Hooghly River, LSHR, with that of the Sundarbans wetland, SW. Mean total PAHs levels were concerning, with mean individual loads exceeding legal limits and literature references, indicating a worsening scenario compared to past surveys. The mean of ∑PAHs in LSHR was significantly higher than in the SW, 2,106 ng/g vs. 1179 ng/g, with a hot spot of 13,785 ng/g. Thus, it is especially in the river location that contaminants accumulate with five compounds concentrating at higher rates compared to the natural area, 103% (PHE), 86% (FLT), 122% (PYR), 156% (CHR), and 1500% (DhA). An evident dominance of the heavy pool (4 to 6 rings) was also observed with a sixfold higher load with respect to the light pool (2 to 3 rings), 1,413 vs. 266 ng/g. PAHs source screening by diagnostic ratios revealed the dominance of pyrogenic sources. Most of sediments of the low stretch present high toxicity risk, and urgent attenuation measurements are needed to improve the environmental state of the river and nearby wetland ecosystems.