Urban waste dominates microplastic pollution in Ethiopian irrigated farmlands: Evidence from FTIR spectroscopy, random forest classification, and farmer surveys

Abstract Microplastic (MP) pollution in agricultural systems is a growing global problem, yet it has been understudied in sub-Saharan Africa. Here, we present the first detailed study of microplastic pollution in irrigated agricultural lands near Hawassa City, Ethiopia, using both environmental sample characterization and smallholder farmer survey data for the policy recommendations. We sampled soil (n = 20) and irrigation water (n = 20), and used Fourier Transform Infrared spectroscopy with a Random Forest machine learning classifier to quantify microplastics and trace the origins of contamination. Widespread contamination was observed with average values of 414 ± 137 particles per kg in soil and 30 ± 17 particles per L in irrigation water, dominated by polyethylene (56.1%) and polypropylene (32.4%) polymer profile. Importantly, the ML classifier attributed 81.7% of the total microplastics to municipal waste rather than industrial activities (18.3%). This strongly suggests that inadequate urban solid waste management, not industrial point sources, is the primary driving contamination sources of agricultural areas. Concurrently, a parallel smallholder survey (n = 20) indicated very poor understanding of microplastics (85% had no awareness) and no mitigation practices were taken in 95% of cases. However, one farm that uses protected cultivation structure (hoop house) with filtered borehole irrigation source showed a significant reduction in contamination, indicating the potential for low-cost and low-tech methods. The vast majority of microplastics originates from urban waste sources and therefore urgently requires a policy intervention focused on improving municipal waste collection to prevent plastic leakage into irrigation channels, enforcing existing bans on single-use plastics, and launching targeted farmer education programs to bridge the identified awareness gap.