Effects of petroleum contamination on bacterial diversities and enzymatic activities in paddy soils were investigated in the Shenfu irrigation area, the largest area irrigated by oil-containing wastewater for more than 50 yr in northeastern China. Bacterial diversities were determined by conventional colony morphology typing techniques and 16S rDNA polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE). Dehydrogenase, hydrogen peroxidase, polyphenol oxidase, urease, and substrate-induced respiration (SIR) were measured to evaluate the effects of petroleum-containing wastewater irrigation on soil biochemical characteristics. Results showed that paddy soil total petroleum hydrocarbon (TPH) concentration in the irrigation area varied from 277.11 to 5213.37 mg kg(-1) dry soil. Soil TPH concentration declined along the gradient of the irrigation channel from up- to downstream. At the current pollution level, the paddy soil TPH concentration was positively correlated with the colony forming units (CFU) of aerobic heterotrophic bacteria (AHB) (r = 0.928, p < 0.001) and the genetic diversity based on DGGE profiles (r = 0.655, p < 0.05). The bacterial diversities in the soils based on colony morphotypes of AHB also increased with TPH concentration (r = 0.598), but not significant statistically (p = 0.052). Analysis of soil enzyme activities indicated a significant positive correlation between soil TPH concentration and activities of dehydrogenases (r = 0.974, p < 0.001), hydrogen peroxidases (r = 0.957, p < 0.001), polyphenol oxidases (r = 0.886, p < 0.001), and SIR (r = 0.916, p < 0.001). On the contrary, the urease activity showed a negative correlation with paddy soil TPH concentration (r = -0.814, p = 0.002), and could be used as a sensitive indicator of petroleum contamination.

Monitoring the migration of pore pressure, deformation, and saturation plumes with effective tools is important for the storage and utilization of fluids in underground reservoirs, such as geological stores of carbon dioxide (CO2) and natural gas. Such tools would also verify the security of the fluid contained reservoir‐caprock system. Utilizing the swelling strain attributed to pressure buildup and the adsorption of supercritical CO2 on clay minerals, we tracked the fluid plume in a natural clay‐rich Tako sandstone at the laboratory core scale. The strain was measured by a high‐resolution distributed fiber optic strain sensing (DFOSS) tool. The strain changes induced by CO2 adsorptions on clay minerals were significantly greater than those caused by pore pressure alone. The distribution of the swelling strain signals effectively captured the dynamic breakthrough of the CO2 plume from the high‐ to low‐permeability regions in the Tako sandstone. Besides revealing the in situ deformation state, the measured strain changes can track the movement of the CO2 plume as it enters the clay‐rich critical regions in the reservoir‐caprock system. The present findings and potential future applications of DFOSS in the field are expected to enhance the monitoring and management of underground fluid reservoirs.

This is the first study to achieve anaerobic and heterologous production of rhamnolipid. Results demonstrated the potential feasibility of Rhl as a promising strain to enhance oil recovery through anaerobic production of rhamnolipid.