Seasonal comparison of the effect of landfill leachate from Mediouna (Casablanca, Morocco) on germination and -amylase activity in Lens culinaris and Medicago sativa

The aim of this study is to evaluate the seasonal changes in leachate compositions, and their impact on germination tests and alpha-amylase activity. Throughout the four seasons of the year 2022, leachate samples were collected in autumn, winter, spring, and summer directly from the collection conduit of the untreated leachate pond at Mediouna landfill (Casablanca, Morocco). The parameters analyzed in the leachate samples included pH, electrical conductivity (EC), chemical oxygen demand (COD), 5-day biochemical oxygen demand (BOD5), nitrate (NO3-), ammonium (NH4+), and orthophosphate (PO43-). The present study involved the execution of germination tests on municipal solid waste leachate. Lens culinaris and Medicago sativa seeds were exposed to leachate at different dilutions of 1%, 3%, 5%, 7%, and 10%, with tap water as control, for about 72 h in the dark at room temperature. Severe toxicity was observed for the 7% and 10% concentrations, observing that L. culinaris and M. sativa showed a mean value of germination index inferior to 50%. These results can be explained by the presence of inhibitor elements in the leachate such as heavy metals (Pb and Hg) and sodium. Lead (Pb) and mercury (Hg) have mean concentrations of 0.2276 ppm and 0.0159 ppm, respectively, while sodium (Na) exhibits an average concentration of 359.942 ppm. In addition, for the biochemical parameters, we noted a decrease in alpha-amylase activity proportionally to the germination index. In conclusion, this work highlights the significant metabolic disturbances induced by leachate, harming the germination of L. culinaris and M. sativa seeds. The present results highlight the potential deleterious effects of leachate pollution on agricultural activities and the ecosystem. However, it may also be possible to take advantage of the leachate's richness in organic matter and nutrient salts to fertilize agricultural land. Our next investigations will aim to verify whether the use of leachate as fertilizer will cause damage to crops and soil.