The co-application of earthworms (Dendrobaena veneta) and compost to increase hydrocarbon losses from diesel contaminated soils

The feasibility of using composted civic waste for the remediation of a soil contaminated with petroleum hydrocarbons (extractable petroleum hydrocarbons (EPH) 10 +/- 1.8 g kg(-1) and total 16 USEPA PAH 1.62 +/- 0.5 g kg(-1)) was assessed. The effects of compost to soil ratio, in combination with and without earthworm presence (Dendrobaena veneta), upon the loss of contaminants were determined for EPH (GC-FID) and PAH (GC-MS), respectively. Increasing the ratio of compost substrate to hydrocarbon impacted soil (1:0.5, 1:1, 1:2 and 1:4 (soil: compost wt/wt)) in the absence of earthworms resulted in significantly (p < 0.05) greater losses of both EPH and Sigma PAH after an 84 d incubation period, when compared to the soil only control. Where earthworms were present without compost, EPH losses were significantly (p < 0.05) enhanced in the soil only treatment (33.4 +/- 53% residual) compared to the soil only control (54.4 +/- 5.3% residual). However, PAH loss in the soil only treatment (with-earthworm presence) were only slightly enhanced (65.3 +/- 9.3% residual), with respect to the soil only control (69.2 +/- 6.4% residual). Synergistic benefits of both earthworm and compost presence were most significant for PAHs (p < 0.05), and less so for EPH. C-14-respirometer studies, to establish catabolic competence in terms of microbial mineralisation of key hydrocarbons, complemented the hydrocarbon analysis. (C) 2008 Elsevier Ltd. All rights reserved.