Enhanced oil recovery: Environmental issues and state regulatory programs

During 1977–1978, Oak Ridge National Laboratory (ORNL) prepared environmental impact assessments for nine U.S. Department of Energy-sponsored enhanced oil recovery (EOR) field demonstration projects located in six states and reviewed the oil regulations for all oil-producing states. These evaluations revealed some potentially important environmental impacts associated with EOR including (1) pollution of land and surface waters from spills or leaks of oil and brine or other chemicals, (2) loss of biota, (3) excessive erosion and sedimentation (mostly in hilly terrain) and subsequent deterioration of surface-water quality, (4) contamination of groundwater, and (5) excessive air emissions from thermal operations. Potential groundwater impacts include (1) production of toxic and carcinogenic substances from synergistic interactions among chemicals used primarily in the micellar-polymer flooding technique, (2) formation of acid waters with small amounts of oil and metal residues and oxides from in situ combustion, and (3) corrosion of well casings and potential leaks of hydrogen sulfide primarily from injection of miscible carbon dioxide. For use of EOR techniques to expand in an environmentally acceptable manner, environmental planning (including monitoring, protection measures, and reclamation strategies) must be an integral part of the initial project development. Acceptable monitoring, prevention, mitigation, and reclamation procedures are available for most of the identified environmental problems, but the best techniques may not be known by operators or required by law. Most states have stringent controls for plugging abandoned wells and disposal of waste material, but these may not be enforced because of limited staff and funds. However, other environmental considerations, e.g., reclamation plans, water quality and other monitoring programs, and abandonment plans, are often lacking. The need for additional environmental planning and monitoring requirements specific to the oil-production industry is emphasized. States are encouraged to continue strengthening and upgrading their oil-regulatory programs to safeguard the environment. More studies are needed on (1) toxicity and carcinogenicity of chemicals used in injection processes, (2) evaluation of groundwater monitoring methods, and (3) reclamation procedures for soils contaminated by oil and brine.     

Evidence for the presence of a widespread PCDD source in coastal sediments and soils from Queensland, Australia

Recent studies have demonstrated the occurrence of elevated levels of higher chlorinated PCDDs in the coastal environment of Queensland, Australia. This study presents new data for OCDD contamination and full PCDD/F profile analysis in the environment of Queensland. Marine sediments, irrigation drain sediments and topsoil were collected from sites that were expected to be influenced by specific land-use types. High OCDD concentrations were associated mainly with sediments collected near the mouth of rivers which drain into large catchments in the tropical and subtropical regions. Further, analysis of sediments from irrigation drains could be clearly differentiated on the basis of OCDD contamination, with high concentrations in samples from sugarcane drains collected from coastal regions, and low concentrations in drain sediments from drier inland cotton growing areas. PCDD/F congener-specific analysis demonstrated almost identical congener profiles in all samples collected along the coastline. This indicates the source to be widespread. Profiles were dominated by higher chlorinated PCDDs, in particular OCDD whereas 2,3,7,8-substituted PCDFs were below the limit of quantification in the majority of samples. The full PCDD/F profile analysis of samples strongly resemble those reported for lake sediments from Mississippi and kaolinite samples from Germany. Strong similarities to these samples with respect to congener profiles and isomer patterns may indicate the presence of a similar source and/or formation process that is yet unidentified.     

Inter-annual and spatial variability in hillslope runoff and mercury flux during spring snowmelt

Spring snowmelt is an important period of mercury (Hg) export from watersheds. Limited research has investigated the potential effects of climate variability on hydrologic and Hg fluxes during spring snowmelt. The purpose of this research was to assess the potential impacts of inter-annual climate variability on Hg mobility in forested uplands, as well as spatial variability in hillslope hydrology and Hg fluxes. We compared hydrological flows, Hg and solute mobility from three adjacent hillslopes in the S7 watershed of the Marcell Experimental Forest, Minnesota during two very different spring snowmelt periods: one following a winter (2009-2010) with severely diminished snow accumulation (snow water equivalent (SWE) = 48 mm) with an early melt, and a second (2010-2011) with significantly greater winter snow accumulation (SWE = 98 mm) with average to late melt timing. Observed inter-annual differences in total Hg (THg) and dissolved organic carbon (DOC) yields were predominantly flow-driven, as the proportion by which solute yields increased was the same as the increase in runoff. Accounting for inter-annual differences in flow, there was no significant difference in THg and DOC export between the two snowmelt periods. The spring 2010 snowmelt highlighted the important contribution of melting soil frost in the timing of a considerable portion of THg exported from the hillslope, accounting for nearly 30% of the THg mobilized. Differences in slope morphology and soil depths to the confining till layer were important in controlling the large observed spatial variability in hydrological flowpaths, transmissivity feedback responses, and Hg flux trends across the adjacent hillslopes.