Evaluation of Biostimulation (Nutrients) in hydrocarbons contaminated soils by respirometry

The biostimulation process was evaluated in a hydrocarbon contaminated soil by respirometry after amendment with inorganic compound fertilizer (ICF) (N: P: K 28:12:7) and simple inorganic salts (SIS) (NH4NO3 and K2HPO4). The soil was contaminated with oily sludge (40.000 MgTPH/Kgdw). The oxygen uptake was measured using two respirometers (HACH 2173b and OXITOP PF 600) during thirteen days (n=3). Two treatments (ICF and SIS) and three controls (abiotic, reference substance and without nutrients) were evaluated during the study. Physicochemical (pH, nutrients, and TPH) and microbiological analysis (heterotrophic and hydrocarbon-utilizing microorganisms) were obtained at the beginning and at the end of each assay. Higher respiration rates were recorded in sis and without nutrient control. Results were 802.28 and 850.72-1d-1, MgO2kgps-1din HACH, while in OXITOP were 936.65 and 502.05 MgO2 Kgps respectively. These data indicate that amendment of nutrients stimulated microbial metabolism. ICF had lower respiration rates (188.18 and 139.87 MgO2 kgps-1d-1in HACH and OXITOP, respectively) as well as counts; this could be attributed to ammonia toxicity.