A green approach to copper biodetoxification and sustainable agriculture application by vermicomposting in pig manure

Abstract

A green approach of copper (Cu) contaminated pig manure composting by earthworm Eisenia fetida was optimized. This work aims to assess the relationship between the bio-fertility properties and bioaccumulation of Cu during vermicomposting with five different doses of Cu. The optimal concentration of copper largely promoted the enrichment of nitrogen, phosphorus, and potassium, but the biological activities of earthworms could be inhibited once the Cu concentration exceed the threshold. When the Cu doses at 300 mg kg−1, the nutrient recovery rate (Irecovery) of available nitrogen, phosphorus and potassium reached their highest value, concomitant with largest C/N ratio reduced at 46.01 %. Moreover, nutrients recovery mechanism of total phosphorus increased up to 0.11 % h−1 and higher bioaccumulations in faces and intestine were detected by 1.79 and 0.99, respectively, during vermicomposting. The maximal enzyme activity rates (kmax) indicate that the enzyme activities, such as ROS and SOD, are sensitive bioindicators, which can be used to estimate the stress response of earthworms and Cu biotoxicity. The maximum specific growth rate (μmax) of the actinomycetes (TAct) increased gradually from 0.02 to 0.04 with the increase of Cu doses, but total fungi (TF) showed different response to μmax, which decreased firstly and then increased. It was demonstrated that Cu influenced the gut microbial community to vary the bio-fertility properties and bioaccumulation of Cu in the pig manure. All the findings refer that the vermicomposting could be the sustainable agricultural practices.