Effect of macro-and micro-plastics in soil on growth of juvenile lime tree (Citrus aurantium)

Abstract

Plastics in agricultural soils are of current concern to environmental scientist due to potential effects on soil-plant system and food security. In this study, the effect of macro-and micro-sized plastic types of low density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS) in soil on growth of juvenile lime tree were studied using a pot experiment under ambient field conditions. To determine the effect, seven exposure patterns (single: LDPE, PP, PS and mixture: LDPE+PP, LDPE+PS, PP+PS, LDPE+PP+PS) in soil was tested. The results showed that macro-and micro-plastic residues affected the plant during vegetative growth with LDPE single exposure had the strongest negative effects (inhibition of 0.26%). However, LDPE+PP+PS had some positive effects by improving growth higher than the control. Overall, microplastics showed more negative effects than macroplastics, but the lime tree showed strong tolerance (with tolerance index > 70 %) to the different treatments. Without doubt, more research is urgently needed in order to fully understand the effect and mechanism of macroplastics and microplastics in soil-plant system. When understood remediation methods could be formulated to minimize the effects of plastics which are now ubiquitous in the environment.