First insight into microplastic groundwater pollution in Latin America: the case of a coastal aquifer in Northwest Mexico

Abstract Microplastics have been studied on biota and other environmental domains, such as soils. Despite the importance of groundwater as a resource for millions of people worldwide as drinking water and personal hygiene, domestic, agricultural, mining, and industrial purposes, there are very few studies concerning MPs in this domain around the world. We present the first study in Latin America addressing this topic. Six capped boreholes were analyzed in terms of abundance, concentration, and chemical characterization, at three different depths, from a coastal aquifer in Northwest Mexico. This aquifer is highly permeable and affected by anthropogenic activities. A total of 221 MPs were found in the eighteen samples. In terms of concentration, the interval ranged from 4 to 29 particles/L, with an average of 12.3 particles/L. Four synthetic polymers were identified: isotactic polypropylene (iPP), hydroxyethylcellulose (HEC), carboxylated polyvinyl chloride (PVC), and low-density polyethylene (LDPE); with iPP being the most abundant (64.3%) in each borehole. Agriculture activities and septic outflows are considered the potential regional sources of these contaminants into the aquifer. Three possible transport pathways to the aquifer are suggested: (1) marine intrusion, (2) marsh intrusion, and (3) infiltration through the soil. More research about the occurrence, concentration, and distribution of the different kinds of MPs in groundwater is needed to have a better understanding of the behavior and health risks to organisms, including human beings.