A comparative study on the influence of different organic amendments on trace element mobility and microbial functionality of a polluted mine soil

- Evaluation of organic amendments to remediate a trace element-polluted mine soil.
- Trace element mobility was reduced in the order: MSWC > OPSW > peat > leonardite.
- Microbial functionality was enhanced in the order: peat ≥ MSWC > OPSW > leonardite.
- Trace element immobilization levels about 75% were achieved at a MSWC dose of 5%.
- Mine soil microbial respiration and dehydrogenase activity were greatly enhanced at a MSWC dose of 5%.

A mine soil heavily polluted with zinc and cadmium was employed to evaluate the capacity of organic amendments of different origin to simultaneously reduce soil trace element mobility and enhance soil microbial functionality. With this aim, four organic products, namely olive processing solid waste (OPSW), municipal solid waste compost (MSWC), leonardite and peat, were applied individually at different doses (0, 1, 2 and 5%) to mine soil under controlled laboratory conditions. Extraction studies and analysis of soil microbiological parameters (basal soil respiration and dehydrogenase, β-glucosidase, urease, arylsulfatase and acid and alkaline phosphatase activities) were performed to assess the effect of such amendments on soil restoration. Their ability to decrease mine soil mobile trace element contents followed the sequence MSWC > OPSW > peat > leonardite, with the former achieving reduction levels of 78 and 73% for Zn and Cd, respectively, when applied at a dose of 5%. This amendment also showed a good performance to restore soil microbial functionality. Thus, basal soil respiration and dehydrogenase, urease and alkaline phosphatase activities experienced increases of 187, 79, 42 and 26%, respectively, when mine soil was treated with 5% MSWC. Among tested organic products, MSWC proved to be the best amendment to perform both the chemical and the microbial soil remediation.