Detection and characterization and risk of microplastic in groundwater in the Eastern Province of Saudi Arabia

Abstract

Microplastics have become an emerging contaminant found in groundwater. Microplastics is a concern in areas where aquifers are the main source of drinking water. This study assessed the presence, characteristics and potential risk of microplastics in shallow coastal aquifers of Al-Qatif, Eastern Province of Saudi Arabia. Groundwater was collected from ten shallow wells (SW1–SW10), prepared and processed through density separation, oxidative digestion, stereomicroscopy, and Raman spectroscopy to isolate, characterize and identify microplastics. Eight polymer types were found: polyethylene terephthalate (PET), polyethylene (PE), polyamide (PA), polystyrene (PS), polyvinyl chloride (PVC), polypropylene (PP), polycarbonate (PC) and an acrylonitrile–butadiene–styrene polyethylene blend (ABS–PE). Total Microplastics concentrations ranged from 5 to 16 particles L⁻¹, with a mean of 8.6 particles L⁻¹. PE and PC are the most abundant polymers (2.0 and 1.5 particles L⁻¹, respectively), followed by PET, PA and PP. PS, PVC and ABS–PE were present at lower average concentrations but still contributed to the overall polymer mixture. Most MPs occurred as fibers and fragments with sizes between 25 and 520 µm.
To evaluate potential ecological risk, Contamination Factor (CF), Polymer Hazard Index (H) and Pollution Risk Index (PRI) were evaluated. Polymer Hazard index values were found to range from 21.4 to 985.9, and PRI values vary between 25.7 and 1384.2. Four wells (SW6–SW9) falls into the high-risk category (PRI ≥ 200), mostly because of the presence of highly risk hazardous polymers such as ABS–PE and PVC. SW3 and SW10 had a moderate risk while the other wells were assigned low risk. SEM and FE-SEM analyses indicated that microplastics had rough and porous surfaces which meant there were some inorganic elements associated with the MPs. Therefore, it could be suggested that the MPs may serve as a means of transport for other contaminants. The findings represent the first mapping of the extent of MP contamination in the groundwater of Al-Qatif and point out the necessity of continuous monitoring as well as proper handling of plastic waste and wastewater in arid and semi-arid areas.

Keywords: Groundwater; Al-Qatif; Microplastic; Saudi Arabia; Shallow well.