assessment of coal and other solid fuel resources in 1993. The Armenian coal deposits evaluated in the preliminary study were found to be similar to Appalachian coals and Gulf Coast lignites in the United States that are used extensively for industry and for generating electricity.

On the basis of the preliminary assessment, the USGS began an expanded program of coal exploration and development in 1994. USGS scientists will train Armenian geologists to assess their country's coal resources, to develop efficient exploration strategies, and to provide the Armenian Government with a plan for increasing the nation's energy self-sufficiency. This cooperative effort will include exploration drilling and geophysical logging, establishment of laboratories for coal-quality analysis, creation of computer facilities for developing databases and estimating coal resources, geologic framework studies that will aid in devising coal-development strategies, and evaluation of data for best-use scenarios. The program will ultimately provide Armenia with the facilities and expertise necessary to explore for coal and independently determine the best means of developing its coal resources.

Ukraine.-There are three full petroleum basins and part of a fourth basin within Ukrainian territory and on the Black Sea and Azov Sea shelves. Onshore, these basins have been extensively explored to depths of 3 to 4 kilometers. Although the Ukraine will probably never achieve energy self-sufficiency, preliminary indications are that exploration at greater depths could significantly ease this country's dependence on imported oil and gas. In an effort to assist the Ukraine in modernizing its petroleum exploration capabilities, USGS scientists are currently conducting a cooperative program that will (1) establish a modern seismic processing facility and train Ukrainian geophysicists in seismic processing techniques, (2) assist Ukrainian scientists in developing a comprehensive database of petroleum information to guide exploration strategy, (3) perform geochemical analyses of petroleum source rocks from the DnieperDonets Basin, and (4) conduct a quantitative assessment of Ukrainian conventional and unconventional petroleum resources. This work is being conducted collaboratively with the Ukrainian National Geophysical Institute and the National Petroleum Exploration Company.

Preliminary work on this project began in 1994, when a Ukrainian geophysicist spent several months at the USGS Central Region

center in Denver, Colo., using the USGS interactive seismic data processing system to reprocess Ukrainian seismic data from the Dnieper-Donets Basin. The resolution of the resulting profiles is much higher than that of the profiles processed with older technology. This enhancement of processing capabilities will directly influence exploration for oil and natural gas by allowing Ukrainian geologists and geophysicists to identify potential structural and stratigraphic petroleum traps that could not be seen on the old profiles.

Once the seismic processing facility is established in the Ukraine, scientists will begin to reprocess and reevaluate comprehensive seismic data sets from the DnieperDonets and Carpathian Basins. These data will help Ukrainian geologists and geophysicists identify new petroleum exploration targets. This capability, together with other products of this effort, will provide the Ukraine with information needed to expand petroleum production and attract foreign investment in petroleum exploration, which will help support the Ukrainian economy.

Kyrgyzstan.-Located in southern Asia between China and Kazakhstan, Kyrgyzstan is relatively small in size; its economy is less than 1 percent of the former Soviet Union's economy. The country does, however, possess enough coal resources to provide for its own heating and power generation needs and still have coal left for export. All of the coal presently mined in Kyrgyzstan-about 2 million tons annually-is used for heating. Coal in some unmined deposits may be suitable for steel production. Rocks deposited in central and eastern Asia 150 to 200 million years ago contain major coal deposits and are mined extensively for electric power generation and domestic and industrial heating. Coals of the same age also occur in Kyrgyzstan, but most deposits are in rugged terrain that may limit access for exploration, mining, and transportation. Also, some of the coal is of low rank and therefore less suitable for mining.

In 1994, the USGS began a project on behalf of USAID to assist in an assessment of the nature, extent, and characteristics of Kyrgyzstan's coal resources. A team of USGS specialists will work with counterparts from Kyrgyz organizations responsible for coal exploration, recovery, and utilization. The team's research will be integrated with supplementary efforts by mining engineers and utilization specialists provided by USAID. The project will result in an assessment of the total coal resources as well as an evaluation

modern placers derived from these rocks. Mercury was used to extract gold from ore by the earliest European settlers, and the technique was adopted by local mine workers. The mercury amalgamation process unfortunately is still widely used in Venezuela because there is no effective, low-cost alternative (fig. 2). The process involves relatively simple, inexpensive methods (such as the use of hand-hewn wooden riffles and traps), so it is accessible to even the smallest mining operations. The mercury amalgamation technique is nearly identical to the techniques used by miners in California during the mid-1800's and in the early Alaska gold-rush period some 40 years later.

These small but numerous mining operations in Venezuela recover only a fraction of either the total gold or the added mercury. For example, tailings that were sampled downstream from a sluice-box operation in the Rio Caroni Basin showed that effective gold recovery is commonly less than half. In addition, the mass of mercury lost to the environment is estimated to be about 1.0 to 1.5 times the mass of gold recovered. Of this mercury, about 40 percent is associated with the tailings. The rest is lost to the atmosphere when the amalgam is roasted during the gold recovery process. Although the amalgam is squeezed by hand to remove excess mercury, much still remains in the tailings. The tailings themselves are released into rivers during mining, excavations, and natural weathering.

The widespread use of mercury in the informal exploitation of surficial deposits was prohibited by presidential decree in Venezuela in July 1991. However, centuries of use combined with the recent upsurge in gold mining activity have left an estimated 40 tons of mercury behind in the forests and rivers.

To assess both the extent and the severity of the mercury contamination problem in the Guayana Shield, it is necessary to understand the biogeochemical cycling of mercury in this complex tropical ecosystem. Unfortunately, little is known about either the transport and release of mercury or the processes that control its form, sorption, and deposition. Because the high temperatures and humidity in the tropics accelerate many chemical and biological reaction rates, mercury moves rapidly through terrestrial ecosystems and accumulates readily in aquatic ecosystems.

Cooperative studies of these issues by the U.S. Geological Survey (USGS), the U.S. Forest Service (USFS), and the Venezuelan Government go back several years. Specifically, the Corporacion Venezolana de

Guayana (CVG), under the bilateral Venezuelan Cooperative Project with the USGS, requested technical assistance in remediating some of the environmental damage caused by mining. In 1991, the USGS and the USFS presented a short course on environmental considerations and reclamation in mineral development for Tecnica Minera (TECMIN), the branch of CVG that deals with mining issues in eastern Venezuela. In 1992-93, the USGS completed the geology and mineral resource assessment of the Venezuelan Guayana Shield (published in 1994 as USGS Bulletin 2062). During that period, various geologists at the USGS Center for InterAmerican Mineral Resource Investigations in Tucson, Ariz., laid the groundwork for a joint study of the distribution of mercury in the environment.

and areas needing further research. The USGS and USFS then summarized the recommendations of the workshop and proposed areas of future collaboration with Venezuela.

Larry P. Gough conducts regional environmental geochemical studies with the USGS and is an expert in the biogeochemical cycling of metals. Floyd Gray

is the former USGS resident scientist in Venezuela and is in charge of the CVG-TECMIN/USGS bilateral project.

Contaminant Migration in Fractured Swedish Rock

ince 1989, scientists from the U.S.

Geological Survey (USGS) and the Swedish Ministry of the Environment and Natural Resources have worked together to advance the state of the art in evaluating specific sites for a nuclear-waste repository in Sweden. As part of their efforts to ensure public safety, the Swedish agency responsible for building the nuclear-waste repository has, for the past 20 years, made unprecedented measurements to characterize the underground environment in which the waste will be isolated. The goal is to ensure that the repository function will not be compromised by water flow through rock fractures or any other process.

Sweden's plan is to isolate the waste from contact with people for more than 100,000 years in manmade horizontal tunnels, 500 meters below ground, in solid granitic rock. Dangerous nuclear fuel rods would be sealed in containers covered with a thick shell of copper and buried in impermeable bentonite-clay-lined holes in the bottom of each tunnel. When disposal is complete, the tunnels would be refilled and the land surface restored. If research can prove the safety of this theory, then actual construction of disposal facilities could begin within 10 years.

At the depth of the planned repository, subsurface rock is saturated with water; although the rock is virtually a solid granite, it is highly fractured. The potential safety hazard caused by such fractures is that water can flow through them and, as a result, around and through the repository, corroding the

canisters, dissolving the toxic radionuclides contained within, and carrying them to the surface where people may be exposed to the radiation. This type of rock also is found extensively in the United States.

Recent work on this project includes hydrogeologic characterization of the bedrock at a site in southeastern Sweden. The illustration shows all of the structures (fractures) found in the bedrock to date in the cooperative project. The image is based on an integrated interpretation of Swedish data on geology, geophysics, and geochemistry by scientists from the USGS and Sweden. Because water flows through most of these structures, the area is more permeable than expected in such bedrock and less than ideal for subsurface waste isolation.

In the United States, toxic waste contaminates many bedrock areas; as it does in Sweden, the waste migrates with water that flows through fractures. The paths of contaminant migration through such fractures are extremely complicated. Most often, it is not economically feasible to further an understanding of how the contaminant is spreading and what procedures are required for site restoration. Through cooperative projects with agencies in Sweden, the USGS is sharing data collected at sites in Sweden and conducting analyses in cooperation with international teams to clarify how water and contaminants

A view of structures found underground at the site of an underground laboratory in fractured granitic rock. The block shown is 2 kilometers wide in each direction and 1 kilometer deep. The relief shown at the Earth's surface is Aspo Island, located on the coast of southeastern Sweden.