Aquatic hazard and biodegradability of light and middle atmospheric distillate petroleum streams

Light and middle atmospheric distillate petroleum substances are blended to produce fuels used in transportation and heating. These substances represent the majority by volume of crude oil refined products in the United States. The goal of this research was to develop biodegradability and aquatic toxicity data for four substances; heavy, straight-run naphtha (HSRN), hydro-desulfurized kerosene (HDK), hydro-cracked gas oil (HCGO), and catalytic-cracked gas oil (CCGO). Ready biodegradability tests demonstrated rapid and extensive microbial oxidation of these test substances, indicating a lack of persistence in the aquatic environment. Differences in biodegradation patterns reflected compositional differences in the constituent hydrocarbons. Results of aquatic toxicity tests on alga, cladocera, and fish demonstrated that toxicity was greatest for catalytic-cracked gas oil, which contained a high proportion of aromatic hydrocarbons. Aromatic hydrocarbons are more soluble, and hence more bioavailable, resulting in higher toxicity. When expressed on the basis of loading rates, acute toxicity values (LL/EL50) ranged between 0.3 and 5.5 mg L−1 for all three species, while chronic no-observed-effect loading rates (NOELR) ranged between 0.05 and 0.64 mg L−1. PETROTOX estimates for acute and chronic toxicity ranged from 0.18 to 2.3 mg L−1 and 0.06 to 0.14 mg L−1, respectively, which were generally more conservative than experimental data.