Title : Ice core drilling at Vostok Type : Antarctic EAM NSF Org: OD / OPP Date : September 7, 1993 File : opp94007 OFFICE OF THE DIRECTOR 202/357-7766 MEMORANDUM Date: September 7, 1993 From: Acting Environmental Officer Subject: Initial Environmental Evaluation (Deep Ice Core Drilling at Vostok Station, Antarctica Environmental Impact Assessment and Finding) To: Office Director, Polar Programs Manager, Polar Operations Health and Safety Officer Head, Polar Science Section Manager, Science Projects Program Manager, Glaciology Environmentalist, ASA The Acting Environmental Officer requested that Dr. A. I. Danilov, Arctic and Antarctic Research Institute, Leningrad, and Dr. Jean Jouzel, Laboratoire de Glaciologie and Geophysics d'Environment, CNRS, Grenoble, and Dr. Eric Saltzman, Principal Investigator for the National Science Foundation's Deep Ice Core Drilling project at Vostok Station, prepare an Initial Environmental Evaluation (IEE) on the use of Freon (CFC-11) as a drilling fluid and its potential environmental effects. On September 7, 1993, the Acting Environmental Officer received the requested assessment. Finding The Acting Environmental Officer believes that the assessment clearly identifies and considers the potential environmental effect of using Freon in combination with kerosene as a drilling fluid and on-going environmental management actions needed to prevent or mitigate unnecessary impacts to that environment. Loss of Freon (338 liters/year) and kerosene is very small. Also, the Acting Environmental Officer believes that from the information contained in the assessment it is unlikely that the ice core drilling operation will have more than minor or transitory effects/significant impacts on the environment at Vostok Station. Furthermore, there are recognized benefits for continuing high quality science being obtained from this ice core, which is the deepest one in the world, from the proposed action. Jane Dionne cc: Chairperson, NSF Committee on Environmental Matters Dr. Eric Saltzman Dr. Jean Jouzel Dr. A.I. Danilov DEEP ICE CORE DRILLING AT VOSTOK STATION, ANTARCTICA: ENVIRONMENTAL ASSESSMENT Summary Statement The deep drilling project at Vostok station Antarctica involves the use of a mixture of kerosene and Freon (CFC-11) as a drilling fluid. The use of Freon is potentially environmentally hazardous because of its role in the destruction of the stratospheric ozone layer. In this document we discuss the procedures involved in the use of drilling fluid at Vostok during the coming field season and assess the potential environmental impact of its use. The issues addressed include: 1) procedures for transport and use, 2) estimate of losses during drilling, and 3) long term storage of drilling fluid in the hole. We also address the potential hazard to human health from kerosene and Freon emissions during the drilling operations. The conclusion of this study is that emissions released during the course of this project do not pose a significant threat to the environment or to human health. It is proposed that the mixture currently in use be continued as the drilling fluid densifier to complete the current drilling effort at Vostok and that alternative fluids be utilized for future drilling efforts. I. Background The joint Russian-US-French Vostok research project (S-161) involves deep ice core drilling at the Russian base of Vostok station in Antarctica (78°28'S, 106°50'E, 3488 meters above sea level; see Figure 1). The Russians have responsibility for the drilling operations and the maintenance of the station. The fluid used for the ongoing drilling operation at Vostok station is a mixture of kerosene and halogenated solvent (trichlorofluoromethane: CCl3F or CFC-11) at a concentration of 10 percent. The halogenated solvent is used to increase the kerosene density (860 kgm-3) up to a density close to the ice density (920 kgm-3). All previous holes at Vostok were drilled using this fluid and the hole which is currently underway (5G) was started with it. In order to complete the project, an additional 6 tons of halogenated solvent is needed and should be delivered to Vostok station (via Russian traverse) by spring 1994. The choice of CFC-11 as a densifier is based on the following requirements: high density, chemically stable, can be mixed with kerosene in all proportions, no reaction with water or ice, freezing point (-111°C) well below the minimum site temperature (e.g. - 89°C in winter), no interaction with the cable and drill component and low toxicity. Note also that it was also successfully used in the European Greenland Ice Core Project (GRIP) for drilling to 3028m of depth in 1992. The PICO (Polar Ice Coring Office) drill which recently completed the US Greenland Ice Sheet Project (GISP2) hole at Summit, Greenland was designed for use with n-butyl acetate as the drilling fluid with no additional densifier. This effort was successful, demonstrating that alternatives to CFC-11 are feasible. However, significant difficulties were encountered during that project due to the corrosive properties of n-butyl acetate under drilling conditions. These properties caused significant deterioration of cables and motors during the course of the project. Thus, changing drilling fluid from the kerosene/CFC-11 mixture to any alternative would require significant research and development in order to anticipate the effect on the existing drill and may require extensive modification. Efforts to investigate alternatives densifiers such as HCFC's are underway, but there are no results at this time. II. Operations involving CFC-11 at Vostok A) Transport of CFC-11 and storage at Vostok Station The halogenated solvent is manufactured in Russia and shipped in armored, shock-resistant drums. The drums have a volume of 1000 liters and weigh 1 ton when empty. They are designed specially for transportation and storage of this chemical compound. They are filled with 650 liters (i.e. 1 ton of CFC-11). The drums are resistant to high pressure (generally tested at 19 bars) and for storage in a hot ambient temperature (e.g. in a sunny place). There are two manual valves (which are well protected) in one side of the drum. These valves are used to fill and empty the drum. The drums are transported via Russian ship to Mirny, Antarctica and via tractor traverse to the site. No losses of CFC-11 are expected during transport. Once the drums arrive at Vostok, they are secured in a storage facility just below the snow surface. Two or three times a week, aliquots of CFC-11 are mixed with kerosene and added to the drill hole to maintain the fluid level. Procedures for making up the mixture are designed to minimize CFC-11 loss. We estimate that over the course of a year approximately 50 liters of CFC-11 are lost during fluid preparation. B) Use at Vostok station During drilling about 300 liters of drill fluid need to be prepared and introduced on a weekly basis. After the mixture of CFC-11 and kerosene is poured into the hole, the hole is capped with a layer of pure kerosene to minimize CFC-11 loss from the hole by evaporation. During each drill run approximately 30 liters of drill fluid is removed from the hole on the cable, drill, and ice core. Most of this fluid is recovered and recycled. Assuming that 600 runs are carried out during a year (including drilling and geophysical monitoring) and a recycling efficiency of 80% we estimate a loss of 288 liters CFC-11 per year. Therefore, we estimate the total loss to be 288+50=338 liters per year or 0.540 tons per year (assuming a density of 1.6 g/ml.) C) Long Term Storage of CFC-11 in the Vostok hole Long term storage of fluid in the hole is not expected to lead to significant emissions of CFC-11. The hole is capped by several meters of pure kerosene and can be physically sealed to prevent losses. As long as the casing of the hole remains intact, CFC loss should be negligible. Even in the event that the casing leaks, only the fluid in the firn would be subject to loss (5% of the hole). Scientifically, the hole will continue to be of great interest for several years (perhaps decades) for geophysical investigations. After this time it would be possible to remove the fluid from the hole and retrograde it if desired. This operation is technically possible by using a tank and a pump attached at the end of the geophysical cable. The CFC-11 may be separated from the kerosene by distillation, stored in special drums and retrograded. However, it should be noted that such an operation would require extensive logistics (2-3 field seasons) and may entail significant emissions. Therefore at this time it appears preferable that the fluid be left in the hole until such time as the scientific usefulness of the hole has ended. It should also be noted that there are several other holes at Vostok station which are currently filled with similar fluid. III. Potential impact on stratospheric ozone Global CFC production is currently about 1 million of tons per year and the annual release to the atmosphere is estimated to be about 0.2 million tons (Brasseur and Solomon, 1984, p. 415). Our estimate for annual emissions at Vostok is approximately 0.5 tons per year, or 0.00025% of the global emissions. The potential effect of these emissions is likely to be insignificant, provided they become well mixed in the atmosphere. It appears unlikely that these emissions will be involved in the spring Antarctic ozone hole phenomenon, because this would require vertical transport into the stratosphere. Prevailing circulation patterns at Vostok suggest that transport will be downslope as part of the katabatic circulation and that emissions from the site will become well mixed into the Southern hemisphere background. IV. Human Toxicity A) CFC-11 The human exposure to CFC-11 vapor occurs primarily during extraction of the drill from the hole. About 1.6 kilo of CFC-11 might evaporate in the 300 cubic meter of the drill shelter and may give a concentration up to 5,000 ppm. Drillers are exposed only during working hours, as the living quarters are separate. In addition the shelter has a tower acting as a chimney which evacuates warm air, which should reduce the ambient concentration in the shelter. The available information on CFC-11 toxicology is: 1) acute toxicity studies: very low by both the inhalation and the oral route. The 4 hour inhalation LD50 in rats is 26,000 ppm. The oral LD50 is greater than 5g/kg body weight. At high concentration levels it sensitizes the heart to adrenaline. The threshold level is 5,000 ppm to 10,000 ppm. It is not irritating to the skin and only very slightly irritating to the eyes. 2) genotoxicity studies: results show no mutagenic hazard. 3) sub-acute/sub chronic toxicity studies: inhalation showed no significant signs of toxicity at an exposure level of 10,000 ppm. 4) chronic toxicity: CFC-11 was evaluated in lifetime inhalation experiments where rats and mice were exposed at level of 5,000 ppm for 2 years. No significant signs of toxicity and no evidence of carcinogenicity were seen. Therefore the use of CFC-11 for drill operation presents limited health risks when used in normal conditions. B) Kerosene The bulk of the drilling fluid used at Vostok station is kerosene supplied by the Russian Antarctic Expedition. Kerosene is lost during the drilling process as the cable and drill is raised or removed from the hole. During this operation, about 20 liters per 1000 m of cable is removed from the hole by the cable and the drill. The kerosene is collected in a flask under the winch and pumped out of the shelter. Some kerosene evaporates or is spilled during this process. One difficulty in assessing the potential toxicity of kerosene is that it is not a chemically well-defined substance. The chemical composition of kerosene may change from one factory to another and we have no information on the chemical composition of the kerosene used at Vostok station. Here we make the assumption that the kerosene toxicity tests performed by Carpenter et al. (1976) on deodorized kerosene are applicable to that used at Vostok station. Some of the properties of kerosene are: 1) distillation: less than 90 percent at 210°C, 65 percent or more at 250°C , 80 percent or more at 285°C. 2) chemical composition: the main chemical components are C9 to C16 hydrocarbons, with paraffins (roughly 50%), napthenes (40%), aromatics (15-20% in normal kerosene, and less than 5 percent in deodorized kerosene). Deodorized kerosene also has a sulfur content less than 0.01%. Carpenter et al.'s (1976) toxicity studies can be summarized as follows: a) Animal inhalation studies: Air substantially saturated at 25°C with vapor of deodorized kerosene contains about 0.1 mg/liter (14 ppm). This concentration did not cause any adverse effects in rats following an 8 hour inhalation period. To produce maximum signs of discomfort, rats had to be subjected to an aerosol (<0.1 microns) of a mean concentration of 7.7 mg/liter for 6 hours per day. Cats also showed no signs of toxic effects after a single 6 hour exposure to 6.4 mg/liter of aerosol. A longer term exposure study on rats and dogs (6 hr/day for 13 weeks) was carried out using 150-500°F boiling point hydrocarbon mixtures, using air concentrations of 0.1 mg/liter (14 ppm). This study revealed no ill effect attributable to this concentration based upon the parameters studied. b) Human inhalation limits: Human volunteers reported no upper respiratory tract irritation in the standard 15 minute trial at substantially saturated vapor at 25°C. On this basis Carpenter et al. suggested the hygienic standard for deodorized kerosene in the vapor state is 0.1 mg/liter (14 ppm, i.e. saturation at 25°C) and that 0.09 ppm is acceptable for daily inhalation. The concentrations in the Vostok drilling shelter should be considerably lower than the recommended limit because the temperature is well below 25°C (5-10°C) and ventilation should reduce the concentration below saturated levels. It appears that the conditions under which kerosene is handled at Vostok are within current standards of industrial hygiene and do not represent a substantial risk to human health. V. Alternatives and Conclusions The alternatives at this point in time consist of the following: 1. No action - terminate Vostok ice core drilling. 2. Temporarily stop drilling - delay further drilling at Vostok until such time as alternative to CFC-11 exist. This would most likely effectively terminate the scientific project as Vostok, as it would require several years and an unknown commitment of funds from the Russians to redesign their equipment. 3. Complete the current hole using the existing technology and investigate alternative drilling fluids and/or densifiers for future projects at Vostok. It is our conclusion that the use of CFC-11 at Vostok will negligibly impact the environment and the individuals involved in the drilling operation. The scientific gains to be achieved by completion of the existing hole at Vostok outweigh the incremental environmental risk of additional drilling at Vostok. Efforts to find a substitute densifier should be continued and supported for future activities. VI. References Brasseur G. and Solomon S., Aeronomy of the middle atmosphere: chemistry and physics of the stratosphere and mesosphere, Reidel, 1984, 430pp. Carpenter, C.P., D.L. Geary, Jr., R.C. Myers, D.J. Nachreiner, L.J. Sullivan, and J.M. King, Petroleum hydrocarbon toxicity studies XI. Animal and human response to vapors of deodorized kerosene, Toxicology and Applied Pharmacology, 36, 443-456, 1976. ______________________________________________________ August 1, 1993 _______________________________ V. V. Lukin Arctic and Antarctic Research Institute St. Petersburg, Russia _______________________________ Jean Jouzel Laboratoire de Glaciologie et Geophysique de l'Environment, CNRS Grenoble, France ________________________________ Eric Saltzman Rosenstiel School of Marine and Atmospheric Science University of Miami Miami, Florida, USA Figure 1. Map showing the continent of Antarctica and the location of the Vostok Station.