Study the effect of by-products from olive oil extraction on the earthworm activity

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Abbes Laghrour University- Khenchela
The current study aims to investigate the effects of olive mill wastewater (OMWW) and olive mill pomace (OMP) and their combination on the growth, reproduction, survival of the two earthworm species Aporrectodea trapezoides, and Eisenia fetida. Furthermore, their effects on the soil physicochemical characteristics such as (pH, Electrical conductivity (EC), Organic matter (OM), Organic carbon (OC), Total nitrogen (TN), Assimilable phosphorus (P), Phenolic compounds (PP), in addition, FTIR spectroscopy is used to determine the soil polyphenols. Moreover, the current study aims to determine the accumulation of heavy metals from OMWW and OMP in the soil and the bioaccumulation in the two different earthworm species using five increasing doses of OMWW and OMP ranging as follows: 12.5%, 25%, 50%, 75%, and 100% w/w. Findings revealed that olive mill wastes have significant effects on the earthworm endpoints (survival, growth, and reproduction), and showed growth enhancement at lower concentrations of OMP, while mortality of earthworms and reproduction inhibition are found at high doses of OMP and the combination, Eisenia fetida were found more sensitive to exposing to olive mill wastes than Aporrectodea trapezoides. As well as OMWW and OMP have also significant effects on soil physicochemical properties, decrease in soil pH, increase in soil EC, soil OM content, as well as soil OC content. FTIR analysis was showed raise in soil polyphenols content under treatment with OMWW and OMP, meanwhile, soil TN and soil P were not shown a significant change under the treatments applied especially under lower doses. Besides, OMWW and OMP were found contain significant amounts of heavy metals, as a consequence causing a remarkable accumulation of metals in the soil such as (Cadmium (Cd), Chromium (Cu), Copper (Cr), Zinc (Zn), and Iron (Fe), which cause crucial environmental hazards. In addition to the soil accumulation of metals, olive mill wastes were found to cause serious bioaccumulation of heavy metals in earthworm tissue. Results revealed that Aporrectodea trapezoides has the ability to accumulate heavy metals in their tissue more than Eisenia fetida.