In this 10 year study, Brazilian gasoline (100 L, containing 24% ethanol by volume) was released to a sandy aquifer to evaluate the natural attenuation of benzene, toluene, ethylbenzene, and total xylenes (BTEX) in the presence of ethanol. Groundwater concentrations of BTEX, ethanol, and degradation products (e.g., acetate and methane) were measured over the entire plume using an array of monitoring well clusters, to quantify changes in plume mass and region of influence. Ethanol biodegradation coincided with the development of methanogenic conditions while acetate (a common anaerobic metabolite) accumulated. The benzene plume expanded beyond the 30 m long monitored area and began to recede after 2.7 years, when ethanol had disappeared. Theoretical calculations suggest that the transient accumulation of acetate (up to 166 mg L(-1)) may have hindered the thermodynamic feasibility of benzene degradation under methanogenic conditions. Yet, benzene removal proceeded relatively fast compared to literature values (and faster than the alkylbenzenes present at this site) after acetate concentrations had decreased below inhibitory levels. Thus, site investigations of ethanol blend releases should consider monitoring acetate concentrations. Overall, this study shows that inhibitory effects of ethanol and acetate are relatively short-lived, and demonstrates that monitored natural attenuation can be a viable option to deal with ethanol blend releases.

The potential groundwater impacts of biodiesel releases have received limited attention despite the increasing probability of such events. In this work, microcosms were prepared with unacclimated sediment and groundwater from the Ressacada Experimental Site (Florianopolis, Santa Catarina, Brazil) and spiked with 54.8 mg/L of pure soybean or castor oil biodiesel (B100). Oxygen was purged from the microcosms to mimic commonly anoxic and hypoxic conditions at fuel‐impacted sites; low background concentrations of nitrate (1.2 to 2.5 mg/L) and sulfate (2.2 to 3.0 mg/L) were present. Biodegradation was assessed by the removal of fatty acid methyl esters and hydrocarbon components relative to sterile controls. Approximately 80% of soybean biodiesel was biotransformed in 41 d, compared to only 40% of castor oil biodiesel removed in 90 d. The higher persistence of castor biodiesel was attributed to its higher viscosity and lower bioavailability. Additional microcosms were prepared similarly to assess the impact of biodiesel on hydrocarbon degradation. These microcosms were spiked with benzene (2.9 mg/L) and toluene (0.8 mg/L) with or without soybean biodiesel (54.8 mg/L). The biodiesel had an inhibitory effect, increasing the time required to remove toluene from 25 to 34 d. Similarly, 45% of benzene was removed in the presence of biodiesel within 34 d, compared to 90% in the absence of biodiesel. Overall, we postulate that the relatively high viscosity of biodiesel is conducive to limited migration potential and a smaller but longer lasting inhibitory region of influence, compared to that exerted by more soluble, more mobile, and readily degradable biofuels such as ethanol. However, controlled release studies are needed to test this hypothesis and characterize the complex dynamics of such releases.

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Part of the production of the Refinery Getúlio Vargas (Paraná State, South Brazil), is transported through OLAPA Pipeline to a Marine Terminal in Paranaguá. In February/2001 occurred a displacement of a great amount of land which caused abrupt rupture of the pipeline in km 57, and 57.000 liters of diesel oil was spilled. Despite all efforts of PETROBRAS contingency team, the oil spilled reached 3 rivers (Meio River, Sagrado River and Nhun-diaquara River) and ending at the sea in Antonina Bay. Right after the incident, a monitoring program was established to evaluate short term effects. One year after the incident, long term effects were also evaluated, especially concerning benthic community and ecotoxicology on the rivers affected by the spill, and plant and birds community in region on its influence. The results point short term effects on water chemistry, but those lasted no more than one week. Short and long term effects on birds and benthic community were not detected.