Hydrochemical quality and microplastic levels of the groundwaters of Tuticorin, southeast coast of India

Groundwater is essential for drinking as well as irrigation purposes. The occurrence of microplastics (MPs) in the biotic and abiotic environments is widely recorded, but little is known about MP occurrence in groundwater. This study assessed MP contamination and hydrochemical quality in a shallow and unconfined aquifer of Tuticorin, India. Water samples were collected from bore wells and open wells for MP assessment and hydrochemical analysis. All the physicochemical parameters are within defined limits, and the significant variations observed could be due to rock–water interaction and the mixing of seawater and freshwater. MPs are found in groundwater samples with an average abundance of 29.73±3.27 items per liter (range 9–39 items per liter), whereas the mean MP abundance is found to be higher in bore wells (32.9±4 items per liter) than in open wells (23.9±3.56 items per liter). The dominant type of MPs observed are fibers and the colors are red, black and white with a predominant size <3 mm. Results of a hazard assessment (polymer hazard index, PHI) on the MPs place the samples under the hazard level IV category due to the presence of high-hazard-score polymers such as polyamide, polystyrene and polyurethane. No significant correlation is noted between the groundwater quality and the quantity of MPs. The presence of MPs in the groundwater could be due to infiltration from surface sources of plastic pollution and could also result from the mixing of seawater and freshwater. Further study is necessary to identify the sources of MP contamination and to assess the capacity of MPs to infiltrate the aquifer.