CAREER: Determining the mechanism and significance of microplastic pollution impacts on soil hydrology

University Of Memphis, Memphis TN

Investigators

Abstract

Microplastics, ranging from 0.001 to 5 mm in size, originate from various sources such as detergents, cosmetics, and the breakdown of larger items like films, fabrics, and vehicle tires. There is extensive evidence that microplastic pollution has been occurring in terrestrial environments for decades. However, agricultural farms are identified as the most microplastic-polluted areas, mainly due to the use of plastic mulching and the application of wastewater biosolids as fertilizer. This project aims to answer fundamental and critically important questions— Can microplastic pollution change the soil-water-plant interactions? If so, in what mechanism, and to what extent? Microplastics are generally not degradable and accumulate in topsoil systems, resulting in exponential pollution growth in the coming decades. Understanding microplastics’ impacts on soil-water-plant interactions will empower policymakers, scientists, and stakeholders to mitigate or prevent negative outcomes. By comprehending the mechanisms of impacts, scientists can develop effective mitigation strategies. The research objectives of this project have been formulated to advance understanding of the extent and mechanism of microplastics’ impact on soil-water retention characteristics and unsaturated hydraulic conductivity (Objective-1), soil pore structure and morphology using micro-computed tomography techniques (Objective-2), and soil desiccation crack development dynamics (Objective-3). This project will also assess the variance between impacts of new (non-degraded) and aged (degraded) microplastic on soil-water-plant interactions, indexing immediate and long-term impacts of microplastics (Objective-4). This project will generate generalizable outcomes through a comprehensive study of various influential factors, including three typical loamy-texture soils found in agricultural farms, two most commonly used plastic types (low and high-density polyethylene), five microplastic shapes (film, fiber, foam, fragment, and powder), four size ranges (50-150, 150-500, 500-2000, and 2000- 5000 µm), two organic matter contents (1% and 3%), two soil hydrophobicity conditions, and five environmentally relevant microplastic concentrations (< 1%), utilizing advanced statistical regressions and variance models, extended evaporation soil tests, and advanced micro-computed tomography techniques. The objectives will be pursued over five years with the support of two graduate and six undergraduate students. The project will integrate research with education and outreach by 1) implementing a professional development program for K-12 educators and creating a web-based environmental program, 2) introducing students to environmental science, technology, engineering, and mathematics (STEM) research and careers; 3) introducing soil-microplastic pollution to local and national public, scientists, and policymakers, and 4) bringing soil pollution topics to the graduate and undergraduate curriculum at the University of Memphis. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.