Assessing the Efficacy of Dredged Sediments from Zarzis Harbor, Tunisia: Implication to Agriculture

In order to maintain the navigation, a continuous stream of polluted sediments is dredged in Tunisia every 10 years. Due to the increased amounts of marine dredged sediments, their environmental and wider reuse is urgently needed. The main aim of this study was to evaluate the possibility of recycling sediments collected from Zarzis harbor in the southeast of Tunisia in agricultural amended soil. Sediment before (SS) and after desalination (DS), pristine and amended soil were explored for their physicochemical properties. Further, in order to investigate which rate would be able to improve plant growth and to preserve invertebrates’ habitat function, amended soil with 5, 10 15, 20, and 25% w/w of DS was tested in microcosm bioassays. Germination and growth of Avena sativa and avoidance behavior of Eisenia andrei earthworms were tested in the presence of the different matrices. Compared to control soil, calcium content increased with the DS-soil mixture. The C/N ratio was found to be in the range 10–15 which is supposed to be the best with regard to nutrient release and utilization. The seed germination was mostly affected at 25% DS-amended soil. The DS application rate at 15% tended to have positive effect on fresh and dry matter production of the monocotyledons. Overall, results of plant and animal tests showed that the amendment with the marine DS in an agricultural soil had no substantial ecotoxicological impacts. Indeed, plant growth with medium percentages was improved correlatively to the good conservation of worms’ habitat.