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) (NH ₄NO ₃ and K ₂HPO ₄). The soil was contaminated with oily sludge (40,000 mgTPH/kgdw). The oxygen uptake was measured using two respirometers (HACH® 2173b and OXITOP® PF600) 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 mgO ₂kg _ps ^-1d ^-1 in HACH, while in OXITOP were 936.65 and 502.05 mgO2kgps -1d-1, respectively. These data indicate that amendment of nutrients stimulated microbial metabolism. ICF had lower respiration rates (188.18 and 139.87 mgO ₂kg _ps ^-1d ^-1 in HACH and OXITOP, respectively) as well as counts, this could be attributed to ammonia toxicity.