Polycyclic aromatic hydrocarbons in groundwater of oil-rich regions of upper Brahmaputra Valley, India: linkages of colloidal transport

• Published in: Arabian journal of geosciences 2023, Vol.16 (1), Article 66
• Main Authors: Deka, Jinu, Sarma, Kali Prasad, Gupta, Nitu, Ahmed, Md. Sahbaz, Mazumder, M. A. Jafar, Hoque, Raza R.
• Format: Article
• Language: English
• Subjects: Aquifers; Aromatic compounds; Aromatic hydrocarbons; Benzo(a)pyrene; Colloiding; Contamination; Drinking water; Earth and Environmental Science; Earth science; Earth Sciences; Environmental protection; Groundwater; Groundwater pollution; HPLC; Ions; Liquid chromatography; Naphthalene; Oil and gas fields; Oil fields; Original Paper; Pollutants; Pollution dispersion; Pollution transport; Polycyclic aromatic hydrocarbons; Transport; Valleys; Water sampling
• ISSN: 1866-7511; 1866-7538
• DOI: 10.1007/s12517-022-11158-3

In this work, contamination of groundwater by PAHs has been studied around oil fields of upper Brahmaputra Valley of India to understand the sources and colloidal transport of PAHs from the surface to the aquifers. The US Environmental Protection Agency’s (USEPA) priority 16 PAHs were chosen for the study. An HPLC system performed the quantitative analyses of the PAHs in the groundwater samples. The concentration of Σ 16 PAHs was quite convincing, ranging from 5.006 to 48.725 ng mL −1 in the whole study. The maximum individual PAHs concentration recorded for Naphthalene were 20.535 ng mL −1 and 17.884 ng mL −1 in the year 2011 and 2012, respectively. The benzo(a)pyrene (B(a)P) concentration ranged from BDL to 0.954 ng mL −1 during the study period, exceeding the World Health Organization’s B(a)P guideline for drinking water. The PAH composition profile was dominated by 3-ring > 2-ring > 4-ring. Diagnostic ratios were employed to appreciate the origin of PAHs in groundwater, and it was observed that pyrogenic sources dominated the contribution of the PAHs, which provided the clue that transport of PAHs occurred from the surface to the aquifer. There must have been long-range transport of pollutants from distant places, which was examined by the HYbrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) airmass backward trajectories. The major ions in groundwater samples were also assessed, which showed a similar seasonal trends like the PAHs. Several of the ions also showed significant correlations with ΣPAHs, meaning colloidal processes mediated the transport of PAHs from the surface to the aquifers.