Determinants of environmental changes in human-modified ecosystems: Effects of plastics on moisture gradients, nutrients, and clay properties
Jean Claude Ndayishimiye,
Jacqueline Nyirajana,
Pascaline Nyirabuhoro,
Patrick Irakoze Nacumuyiki,
Akinwale Oladotun Coker,
Folake Olubunmi Akintayo,
Yuri Mazei,
Damir Saldaev,
François Nkinahamira,
Théogène Habumugisha,
Theophile Murwanashyaka,
Valens Hishamunda
Affiliations
Jean Claude Ndayishimiye
Faculty of Biology, Shenzhen MSU-BIT University, Shenzhen, 518172, China; The Center for Earth and Natural Resource Sciences, Kigali, P.O. Box 4285, Rwanda; Corresponding author. Faculty of Biology, Shenzhen MSU-BIT University, Shenzhen, 518172, China.
Jacqueline Nyirajana
Department of Civil Engineering, Faculty of Engineering and Technology, Institute of Applied Sciences (INES Ruhengeri), Ruhengeri, P.O. Box 155, Rwanda; Department of Civil Engineering, University of Ibadan, Ibadan, Nigeria; Corresponding author. Department of Civil Engineering, Faculty of Engineering and Technology, Institute of Applied Sciences (INES Ruhengeri ), Ruhengeri, P.O. Box 155, Rwanda.
Pascaline Nyirabuhoro
Faculty of Biology, Shenzhen MSU-BIT University, Shenzhen, 518172, China; The Center for Earth and Natural Resource Sciences, Kigali, P.O. Box 4285, Rwanda
Patrick Irakoze Nacumuyiki
The Center for Earth and Natural Resource Sciences, Kigali, P.O. Box 4285, Rwanda
Akinwale Oladotun Coker
Department of Civil Engineering, University of Ibadan, Ibadan, Nigeria
Folake Olubunmi Akintayo
Department of Civil Engineering, University of Ibadan, Ibadan, Nigeria
Yuri Mazei
Faculty of Biology, Shenzhen MSU-BIT University, Shenzhen, 518172, China; Lomonosov Moscow State University, Leninskie Gory 1, Moscow, 119991, Russia; A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Leninskiy Ave. 33, Moscow, 117071, Russia
Damir Saldaev
Faculty of Biology, Shenzhen MSU-BIT University, Shenzhen, 518172, China; Lomonosov Moscow State University, Leninskie Gory 1, Moscow, 119991, Russia
François Nkinahamira
School of Civil Engineering, Guangzhou University, Guangzhou, 510006, China
Théogène Habumugisha
Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China
Theophile Murwanashyaka
Faculty of Education, Kibogora Polytechnic, Rusizi, P.O.Box 31, Rwanda
Valens Hishamunda
Department of Geosciences, Princeton University, Princeton, NJ, USA
Plastic pollution poses a significant threat to ecosystem health worldwide. This study examines the determinants of environmental changes in human-modified ecosystems through a quantitative-qualitative system dynamics modeling approach: field experiments conducted on a 310 m2 unsaturated clay-rich bed and a 2.5 m2 clay-rich shore of a plastic-impacted pond in Shenzhen, China, and a 1.17 ha plastic-impacted clay pit in Musanze, Rwanda; laboratory experiments involving Modified Proctor (MP) and California Bearing Ratio (CBR) tests on natural clay reinforced with polyethylene terephthalate (PET) microplastics, with diameters ranging from 0.25 to 5 mm and at concentrations of 1.25 %, 2.5 %, 3.75 %, 5 %, and 10 % by weight of clay; and plastic dynamic flows analyzed by modeling the life cycle of PET. Field experiments showed that mulch type and thickness were critical factors influencing crack distribution in a plastic-impacted pond bed. Specifically, cracks were dominant in areas with pronounced desiccation and lacking filamentous green algae and PET-dominated plastic waste. Along the 2.5 m moisture gradient in a plastic-impacted pond bed, temperature and moisture significantly influenced nutrients, particularly in pronounced desiccation zones. Laboratory experiments showed that microplastics altered the structural properties of natural clay, decreasing moisture content while increasing dry density and load-bearing capacity. The plastic life cycle underscored the roles of industrial and consumer practices, environmental conditions, and waste management and recycling inefficiencies in driving environmental changes in human-modified ecosystems. The findings underscore the need for effective plastic waste management and recycling to mitigate the ecological impacts of plastic pollution in ecosystems.
