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

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 ΣPAHs 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 the sediments of the low stretch present a high toxicity risk, and urgent attenuation measurements are needed to improve the environmental state of the river and nearby wetland ecosystems.