Seasonal dynamics of microplastic contamination in deep groundwater sources of urban drinking water supply in an arid region: Distribution, characterization, and risk index assessment

Abstract

This study offers an insightful investigation of microplastics (MPs) distribution and characterization in urban groundwater supply of Kerman arid region, Iran and provides new insights into the complex interaction of MPs properties, their seasonal dynamics, and the effect of local factors. MPs were detected in all samples during three seasons. The highest abundance of MPs was observed in spring (18.14 to 54.41 particles/L) followed by winter (18.14 to 39.29 particles/L) and autumn (9.07 to 30.23 particles/L). A spatial co-occurrence was observed between Shallower water levels and human activities such as cattle ranches, agriculture, mines, factories, and waste disposal as key factors in further contamination of qanats and aquifers 3 and 4. Fibers, black color, and small-sized 50 to 100 mu m were the most abundant morphotype. Polypropylene and polyethylene were the most prevalent polymer types among seven types of identified polymers with the mean abundance percentages of 48.78 and 23.1, respectively. The integrated polymer-based risk index assessment showed that the dominant pollution levels in autumn, winter, and spring were ranked at low, considerable, and considerable classes, respectively. Moreover, the relationship between MPs abundance and physicochemical properties of groundwater such as hardness, pH, EC, turbidity, and fecal coliforms was investigated to understand the transport and accumulation of MPs in groundwater systems. These findings extend beyond the urgent need for environmental monitoring in arid regions with groundwater supplies and provide an important basis and template for developing effective strategies to reduce MPs contamination in similar ecosystems globally.