Assessment of the Physicochemical and Microbiological Evolution of Agricultural and Forest Soils after Underground Oil Piping.

Soil physical, chemical and microbiological properties in agricultural and forest areas were determined to assess their dynamics and evolution induced by environmental restoration processes due to the burial of an oil pipeline. Soil samples were collected from both forest and agricultural areas in a Southern Italy farm, and analyzed for specific parameters and biological indicators, such as total biomass-C, organic-C, respirometric tests, and microbial community composition. Soils were sampled ante-opera, to be used as control, and at the end of first and second years from oil pipeline burying. The soils of both areas showed a considerable evolution of all physicochemical features compared with ante-opera status; a situation of great transformation, still very far from the normal stability condition, was observed. The microbial community composition, assessed by denaturing gradient gel electrophoresis (DGGE), proved the presence of particular species, usually current in contaminated/strongly disturbed soils, involved in the bioremediation/biodegradation natural processes to restore optimal conditions. Forest area samples showed an even soil texture in all sites, compared to the relevant variation observed in the first and second years of post-opera, and an increase of pH and cumulative respiration, elevated values of germination indexes and a strong enrichment of edaphic fauna. The agricultural area proved an interesting diversification of the specific parameters for each sampling site, with significant changes of textural fractions, high values of pH and a remarkable bio-stimulation of germination. Moreover, an elevated intra-specific and functional biodiversity was detected, underlining the soil capacity to tolerate and withstand the disturbances with the presence and the adaptation of bacterial species able to perform certain functions in altered conditions. Concluding, after two years from pipeline burying both the forest and agricultural areas were being under slow evolution. Physical, chemical and microbiological parameters were far from the steady state.