with existing data as well as data from large regional water-quality surveys to characterize and explain, to the extent possible, similarities and differences in the occurrence and distribution of pesticides and nutrients nationwide. This study of the relative magnitudes of point and nonpoint sources of phosphorus in streams draining four river basins is an example of these synthesis efforts. A major topic of discussion in congressional hearings on reauthorizing the Clean Water Act of 1972 is the magnitude and extent of nonpoint-source pollution and its effect on the Nation's streams and aquifers. The reason for this concern is the recognition that the Nation has made a considerable investment to control pollution from point sources and, although these investments are believed to have been successful, additional upgrading of wastewater-treatment levels may not be cost effective for achieving further improvements in water quality. Thus, water resources management agencies are increasing their focus on controlling nonpoint sources of contaminants to improve water quality. Phosphorus is of particular concern. At elevated levels in streams and rivers draining into lakes and estuaries, phosphorus causes nuisance growths of algae and aquatic plants. The four river basins studied-the Kentucky River basin in Kentucky; the upper Illinois River basin in Illinois, Indiana, and Wisconsin; the lower Kansas River basin in Kansas and Nebraska; and the Yakima River basin in Washington State-were part of the NAWQA pilot effort. In general, phosphorus loads (in pounds) and yields (in pounds per square mile) in the upper Illinois and Kentucky River basins were significantly larger than in the lower Kansas and Yakima River basins because of differences in average annual streamflow between the basins. The average annual streamflow from the Kentucky and upper Illinois River basins is more than 2.5 times larger than that from the lower Kansas and Yakima River basins. Phosphorus yields were largest for the upper Illinois River basin. The upper Illinois River basin has the largest percentage (75 percent) of land devoted to cultivated row crops, the largest phosphorus fertilizer application rates, and, because of the large population in the basin (about 7.6 million people), the For more information on the Bemidji study, contact: Telephone (703) 648-6872 Location of study site near Bemidji, Minn., showing the approximate location of the oil body, sampling sites, and cross section A-A' (see box) (from Baedecker and others, Applied Geochemistry, v. 8, p. 569-586, 1993). Natural Remediation of Oil Contamination in Ground Water Petrol etroleum hydrocarbons are significant ground-water contaminants in the United States. The combination of accidental spills during production, refining, and transportation of petroleum products and leaking underground storage tanks has created thousands of sites where petroleum hydrocarbons have contaminated ground water. Although the number of contaminated sites is large, the impact of these discharges is mitigated by natural biological degradation. Interdisciplinary research conducted under the USGS Toxic Substances Hydrology program at a field site contaminated by crude oil has demonstrated that petroleum hydrocarbons can be degraded by microorganisms that occur naturally in the environment. In 1979, a buried high-pressure pipeline near Bemidji, Minn., burst, spilling 10,500 barrels of crude oil. After cleanup of oil from the land surface, 2,500 barrels (105,000 gallons) of crude oil remained in the unsaturated zone and near the water table in the sand-and In 1979, a buried high-pressure oil pipeline burst, spilling approximately 10,500 barrels of crude oil at a remote site near Bemidji, Minn. gravel aquifer. Because the spill was located in a remote area where ground water is not used extensively, the remaining oil was left in place. All changes observed over time in the distribution of crude-oil components can be attributed to natural processes. At present, the oil is moving very slowly near the top of the water table as a separate fluid phase, and vapors from the oil are moving in the unsaturated zone. Although groundwater chemistry and biogeochemical processes have changed over time, the area of contaminated ground water has not expanded significantly from 1983 to 1992. USGS investigations at the Bemidji field site have provided strong evidence that petroleum hydrocarbons are degraded by natural processes and that these processes can limit the spread of contaminant plumes in ground water. The Bemidji study is significant because it is one of the very few field sites where natural degradation has been documented. A full understanding of the natural degradation processes at this site and at other contaminated sites will provide a stronger scientific basis for decisions about whether and when to employ costly physical and chemical cleanup procedures. Gail Mallard coordinates a USGS program that supports investigations of contaminants in water resources Mary Jo Baedecker is a chemist with the USGS and has conducted research on organic contaminants in ground water Isabelle Cozzarelli is a USGS hydrologist who conducts research on the fate and effects of petroleum products in ground water A generalized section through the contaminant plume shows five zones having different water chemistries. The screened intervals of wells in the aquifer are shown (modified from Baedecker and others, Applied Geochemistry, v. 8, p. 569-586, 1993). Zone II underlies the area where the land surface was sprayed with oil. In this zone, hydrocarbons are gradually being degraded and transported vertically through the unsaturated zone with recharge water. Ground water in this zone contains no volatile hydrocarbons but has high. concentrations of carbon dioxide, which indicate microbial degradation of hydrocarbons. A plume of contaminated ground water containing dissolved constituents from the crude oil, such as benzene and alkylbenzenes, and products from biochemical reactions, such as organic acids, has developed downgradient from the spill site. The part of the plume nearest the oil body (zone III) is lacking in oxygen (anaerobic) and is characterized by high concentrations of hydrocarbons, bicarbonate, reduced iron, manganese, and methane. Bacteria that do not require oxygen are able to degrade some crude oil components in this area. Further downgradient (zone IV), the ground water contains low concentrations of oxygen, and a different group of bacteria is primarily responsible for hydrocarbon degradation. Here, hydrocarbon concentrations are lower than they are in the anaerobic zone of the plume because aerobic degradation proceeds more rapidly and more completely. In the area farthest from the oil spill (zone V), concentrations of some organic and inorganic constituents are above background levels (the levels in zone I), but the concentrations of hydrocarbons are below the EPA maximum levels of contaminants allowable for drinking water. Ground water is moving rapidly enough for crude-oil components to have reached this area. The rate of solubilization of hydrocarbons from the oil body, however, is about the same as the rate at which hydrocarbons are degraded by microbial processes. Environmental Contamination at Department of Defense Sites A ctivities at more than 100 military installations in 38 States and 2 foreign countries highlighted FY 1993 efforts of the Department of Defense Environmental Contamination (DODEC) hydrology program. Facilities involved include those of the Air Force, Army, Navy, Marine Corps, Air National Guard, Army National Guard, and Defense Logistics Agency. Major concerns are the presence and transport of chlorinated hydrocarbons (trichloroethene, dichloroethene, vinyl chloride), constituents of fuels (benzene, toluene, xylenes), and trace metals (lead) in soil and water. Current research studies address natural bioremediation and augmented bioremediation of fuel hydrocarbon compounds in the shallow water-table aquifer. Ongoing projects provide opportunities to increase knowledge in the definition of the hydrogeologic framework within many terranes; movement of ground water and contaminants in different terranes; ground-water-flow modeling in different terranes; occurrence of heavy metals in ground water; isotope geochemistry; surface and borehole geophysics; soil gas and its relation to ground-water contamination; and slug tests and other tests in aquifers to determine aquifer properties in different terranes. The development of relational data bases and use of geographic information system (GIS) technology, as well as the analyses of water quality and the quality control of analytical data and field data, are also benefits derived from the DODEC hydrology program. For more information on DODEC, contact: Telephone (703) 648-5010 For more information on the Nuclear Examples of projects active during FY 1993 include: • Research on the effectiveness of both natural and augmented bioremediation on the degradation of organic compounds in the subsurface. Results of this research being conducted for the Air Force are expected to be important to the development of cost-effective methods of mitigating organic compounds in the subsurface, a principal problem at U.S. military bases throughout the world. • Study of contamination of soil and ground water by trichloroethylene at an Environmental Protection Agency (EPA) National Priority List facility at F.E. Warren Air Force Base in Wyoming. Hydrologic assessment of surface- and ground-water systems, ground-water-flow modeling, and research in paleohydrology at an EPA National Priority List facility at the Rocky Mountain Arsenal in Colorado. ⚫ Migration of petroleum hydrocarbons in the shallow freshwater aquifer of the atoll Diego Garcia in the Indian Ocean. • Assessment of ground-water contamination migrating from landfills and technical support of the Department of Defense (DOD) Installation Restoration Program at Hill Air Force Base in Utah. • Soil and ground-water contamination studies in support of EPA Resource Conservation and Recovery Act (RCRA) facility assessments and investigations and stormwater-runoff monitoring at Fort Bragg in North Carolina. • Soil and ground-water contamination studies in support of EPA RCRA facility investigations at MacDill Air Force Base in Florida. • Regional ground-water hydrogeology and ground-water-flow modeling at Wright-Patterson Air Force Base in Ohio. • Hydrogeologic framework of the shallow water-table aquifer and soil-gas surveys to identify sources of ground-water contamination at the Naval Surface Warfare Center in Dahlgren, Va. John D. Powell has been involved in USGS environmental contamination studies for the past 13 years Nuclear Waste and Water Resources N uclear waste arises from the generation of nuclear power, from the production of nuclear weapons, and from medical, industrial, and other miscellaneous sources. Broad agreement exists that these wastes must be sequestered from the environment, by deep geologic disposal in the case of high-level waste and by shallow disposal or near-surface engineered structures in the case of lowlevel waste. For all options, the hydrology of the site is a key factor in assessing the performance of the total waste-disposal system. Key elements of the Nuclear Waste Hydrology program include: ⚫ Refining methods and techniques for the hydrologic characterization of envi ronments. Finding new instrumentation and techniques for the characterization and monitoring of disposal sites. • Defining hydrogeologic and geochemical processes that occur when nuclear waste, rocks, and ground water interact. • Improving understanding of groundwater flow and contaminant transport in fractured rocks. Recent accomplishments of the Nuclear Waste Hydrology program are as follows: . Using innovative well-logging techniques, the USGS conducted a comprehensive evaluation of the hydrology in the vicinity of waste-disposal sites at the Idaho National Engineering Laboratory. Studies of soil-water movement at a newly excavated experimental trench in the very dry Amargosa Valley in Nevada indicate that there is little if any downward movement below 9 meters (about 27 feet) in depth. A study at a low-level radioactive disposal site in New York State confirmed the role of plants in the uptake of carbon-14 released at such disposal sites. Newell J. Trask is the Chief of the Branch of Nuclear Waste Hydrology |