Available at: https://digitalcommons.calpoly.edu/theses/2916
Date of Award
10-2024
Degree Name
MS in Environmental Sciences and Management
College
College of Agriculture, Food, and Environmental Sciences
Advisor
Seeta Sistla
Advisor Department
Earth and Soil Sciences
Advisor College
College of Agriculture, Food, and Environmental Sciences
Abstract
Terrestrial microplastics are increasing in abundance and are an emerging contaminant of concern, particularly in agriculture ecosystems where plastic use and subsequent soil contamination are prevalent. Plastic film mulches make up a significant portion of the plasticulture industry and are directly linked to soil microplastic pollution where negative effects to soil biotic and abiotic functions have been observed. In response to this issue, biodegradable film mulches have been promoted as a sustainable alternative to conventional polyethylene-based mulches. These biodegradable mulches, composed of various bioplastics, are designed to be tilled back into the soil where they are expected to decompose. However, the degradation of biodegradable film mulches has proven to be inconsistent and unpredictable, potentially leading to the persistence of micro-bioplastic (MBP) particles in the soil that may cause adverse effects like those of microplastics from conventional mulches. To evaluate the efficacy of this novel technology as a viable alternative to conventional plastic mulches, this 2-month incubation study examined the effects of MBPs derived from polybutylene adipate terephthalate (PBAT)-based biodegradable mulch on a suite of soil health indicators. Using laboratory-prepared soils, the study assessed how clay mineralogy and organic matter content influence soil-MBP interactions under controlled conditions. Our results suggest there is a significant effect of MBPs on soil moisture and nutrient cycling with a potential negative priming effect, particularly in soils where organic matter is limited. Additionally, clay mineralogy significantly mediated soil-MBP interactions. While MBP presence altered C pools, a qualitative analysis suggests the MBP particles remained largely undegraded by the end of the incubation period. These findings suggest that MBPs have the potential to influence soil properties and functions, underscoring the need for further research to fully understand their environmental implications in field conditions.