Transport and fate of nitrate and pesticides: hydrogeology and riparian zone processes

There is continuing concern over potential impacts of widespread application of nutrients and pesticides on ground- and surface-water quality. Transport and fate of nitrate and pesticides were investigated in a shallow aquifer and adjacent stream, Cow Castle Creek, in Orangeburg County, South Carolina. Pesticide and pesticide degradate concentrations were detected in ground water with greatest frequency and largest concentrations directly beneath and downgradient from the corn (Zea mays L.) field where they were applied. In almost all samples in which they were detected, concentrations of pesticide degradates greatly exceeded those of parent compounds, and were still present in ground waters that were recharged during the previous 18 yr. The absence of both parent and degradate compounds in samples collected from deeper in the aquifer suggests that this persistence is limited or that the ground water had recharged before use of the pesticide. Concentrations of NO(-)(3) in ground water decreased with increasing depth and age, but denitrification was not a dominant controlling factor. Hydrologic and chemical data indicated that ground water discharges to the creek and chemical exchange takes place within the upper 0.7 m of the streambed. Ground water had its greatest influence on surface-water chemistry during low-flow periods, causing a decrease in concentrations of Cl(-), NO(-)(3), pesticides, and pesticide degradates. Conversely, shallow subsurface drainage dominates stream chemistry during high-flow periods, increasing stream concentrations of Cl(-), NO(-)(3), pesticides, and pesticide degradates. These results point out the importance of understanding the hydrogeologic setting when investigating transport and fate of contaminants in ground water and surface water.     

Protection of biota on nonpark public lands: Examples from the US Department of Energy Oak Ridge Reservation

Security buffers of Department of Defense (DoD) and Department of Energy (DOE) reservations provide long-term habitat protection for many rare and endangered species. The importance of these government-owned reservations as nationally valuable resources has been relatively unrecognized. During the last 50 years, the DOE Oak Ridge Reservation (ORR) has been a relatively protected island in a region of rapidly expanding urbanization and land clearing. Consisting of the Oak Ridge National Environmental Research Park and associated lands surrounding DOE facilities at Oak Ridge Tennessee, the unique nature of the ORR in the surrounding landscape is clearly visible from the air and has been documented using remote sensing data. Although forests dominate much of other regions of eastern Tennessee, this 15,000-ha tract of mostly natural forest habitat is unique in the southern Ridge and Valley physiographic province, which is otherwise widely developed for pasture, marginal cropland, woodlot, and urban uses. Twenty state-listed and federal-candidate plant species are known to be present on the ORR. This richness of species, which are provided protection by state and federal laws, exceeds that of the Great Smoky Mountains National Park on a species area basis and is an index of the value of the ORR both regionally and nationally in conserving biodiversity. With the end of the Cold War, changing DoD and DOE missions combined with increasing development pressure contribute to uncertainty in the future management of security reservations.     

Aquatic biodiversity and the electric utility industry

/ Results from a 1995 survey of utility company biologists indicate that aquatic biodiversity is an emerging and poorly understood issue. As a result, there is some confusion about what aquatic biodiversity actually is, and how we can best conserve it. Only one fourth (24%) of the respondents said their company has a stated environmental policy that addresses biodiversity. Many respondents indicate that over the years they have not specifically managed for biodiversity, but have been doing that through their efforts to assure balanced indigenous populations. While regulations are still the major driver for biological work, an increasing number of companies are involved in voluntary partnerships in managing water resources. Of these voluntary partnerships, 70% have biodiversity as a goal. Biodiversity is becoming an increasingly common subject of study, and a vast majority (75%) of the respondents suggested it should be a goal for utility resource management. Conservation of aquatic biodiversity is a complex task, and to date most aquatic efforts have been directed toward fish and macroinvertebrates. Ecological research and technological development performed by the utility industry have resulted in a number of successful biopreservation and biorestoration success stories. A common theme to preserving or enhancing aquatic biodiversity is preserving aquatic habitat. Increasingly, ecosystem management is touted as the most likely approach to achieve success in preserving aquatic biodiversity. Several utilities are conducting progressive work in implementing ecosystem management. This paper presents the potential interactions between power plants and biodiversity, an overview of aquatic biodiversity preservation efforts within the electric utility industry, more detail on the results of the survey, and recent initiatives in ecosystem management.KEY WORDS: Biodiversity; Ecosystem management; Watershed management; Utilities; Aquatic; Adaptive management     

THE RESTON (VIRGINIA) LAKE-USE SURVEY: PUBLIC PERCEPTIONS AND MANAGEMENT IMPLICATIONS1

ABSTRACT: A public attitude survey was developed by a citizen committee and mailed to all residences (14,747) in the planned, suburban community of Reston, Virginia, which is responsible for maintaining four small, recreational impoundments. Over 18 percent of survey forms were returned, and characteristics of the survey sample suggest that the suite of respondents was representative of the Reston community as a whole. Of those respondents indicating a preferred lake use, 48 percent chose walking or looking as most important; boating as second at 27 percent; and fishing was third, favored by only 8 percent. Citizens feel strongly (94 percent) that the lakes are valuable community assets. Appearance was the characteristic most valued by 62 percent of respondents, and 58 percent considered degradation of water quality either the first or second most important ecological issue affecting local lakes. These findings provide a decisive public mandate for lake management activities related to visual quality. In response to this survey, the Reston Association, a homeowners' organization responsible for the lakes, increased public access of visual enjoyment, intensified litter control, expanded activities in public education on lake management and ecology, and continued a long-term program of water quality monitoring.     

RESOURCE DEMANDS FOR ENERGY DEVELOPMENT IN THE YELLOWSTONE RIVER BASIN1

ABSTRACT: This paper reports on the development of a mathematical model for forecasting energy development in the Yellowstone study area for the years 1985 and 2000, and determining the associated economic demands for water, land, labor, capital, and mineral resources. The study was prepared for use by the Missouri River Basin Commission in conducting a comprehensive, “Level B” planning study of the water and related land resources in the Yellowstone River Basin. The study results indicate that the amount of coal development in the Yellowstone study area will depend primarily upon state and federal energy policies and regulations. Policies related to slurry pipeline transportation of coal will be particularly important in determining the level and pattern of future energy development in the area. Coal production under the “most probable” scenario is expected to increase from about 40 million tons in 1976 to 163 million tons per year by 1985, and 513 million tons in the year 2000. Consumptive water use for energy development in the study area could be as much as 556,000 acre-feet per year by the year 2000 (under the high scenario). A parametric analysis was conducted on the 1985 most probably scenario to determine the influence on the study results of variations in the delivered price of water. Water requirements were reduced by nearly one-fourth as water costs increased from zero to over $750 per acre-foot.     

WILD RIVERS - METHODS FOR EVALUATION1

ABSTRACT: Two analytical methods are presented and demonstrated for evaluating the monetary and nonmonetary benefits of wild rivers. In the traditional benefit-cost context special techniques are required to show that any wild river is worthy of preservation. The methods presented allow for the possibility of low development levels in river basins to be optimal, although advanced development can also be shown to be most efficient in some circumstances. That is, the methods are not directed to the wild condition only but to the entire spectrum of development possibilities. The applications of the methods to two adjacent subbasins in the State of Washington each showed that the currently undeveloped basin should be left in its wild condition, while the partially developed basin next door should be developed even more fully.     

DISPERSION MODEL FOR A STREAM WITH SEVERAL WASTE INPUTS AND WATER INTAKES1

An analytical solution is developed to predict the BOD and DO profiles in a stream having several outfalls of waste and intakes of water. The model also incorporates continuous addition and removal of BOD and DO along the stream. A steady state one dimensional dispersion model is used to describe the transport of BOD and DO in a stream. Changes in stream properties along the length are considered by dividing the stream into several segments and changing the parameters of the BOD and DO equations as needed in each segment. By applying continuity equations at the boundaries of these segments and equilibrium conditions at either ends of the infinitely long stream, the arbitrary constants in the solutions to the differential equations for BOD and DO can be determined. Some applications of the results in studying water pollution problems are illustrated.     

A time-dependent model of nutrient distribution in continental shelf waters

A time dependent, vertical plane mathematical model of nitrate distribution in Onslow Bay, North Carolina, is developed using similarity theory and conventional numerical techniques. Inputs of nitrate into Onslow Bay are the result of Gulf Stream intrusions (Atkinson et al., 1980) and this forcing is included as a boundary condition for this system. Advective and diffusive processes provide the mechanisms for transport of nitrate in Onslow Bay. The time dependence of the resulting nitrate fields is determined by the rate of phytoplankton removal of nitrate.Nondimensional numbers, arising from model formulation, indicate the relative importance of various processes included in the model. Two nondimensional numbers, H and P, and the nondimensional ratio, P/H, indicate interactions of physical processes. Importance of the biological terms is determined by a third nondimensional number, A. Model results are compared to nitrate data collected in Onslow Bay, North Carolina during an intrusion.     

Phosphorus characteristics of dairy feces affected by diets

Phosphorus (P) surplus on dairy farms, especially confined operations, contributes to P buildup in soils with increased potential for P loss to waters. One approach to reduce P surplus and improve water quality is to optimize P feeding and improve P balance on farms. Here we report how varying P concentrations in lactating cow diets affects the amount as well as the chemical forms and fraction distribution of P in fecal excretion, and the environmental implications of this effect. Analysis of fecal samples collected from three independent feeding trials indicates that increasing dietary P levels through the use of P minerals not only led to a higher concentration of acid digest total phosphorus (TP) in feces, but more importantly increased the amount and proportion of P that is water soluble and thus most susceptible to loss in the environment. For instance, with diets containing 3.4, 5.1, or 6.7 g P kg(-1) feed dry matter (DM), the water-soluble fraction of fecal P was 2.91, 7.13, and 10.46 g kg(-1) fecal DM, respectively, accounting for 56, 77, and 83% of acid digest TP. The other fecal P fractions (those soluble in dilute alkaline and acid extractants) remained small and were unaffected by dietary P concentration. Excess P in the P supplemented diets was excreted in feces as water-soluble forms. A simple measure of inorganic phosphorus (Pi) in a single water extract is highly responsive to changes in diet P concentrations and hence can be indicative of dietary P status. A fecal P indicator concept is proposed and discussed.     

CONTROLLING PHOSPHORUS IN RUNOFF FROM LONG TERM DAIRY WASTE APPLICATION FIELDS1

ABSTRACT: Phosphorus (P) in runoff from long term animal waste application fields can contribute to accelerated eutrophication of surface waters. Manure when applied at nitrogen (N) agronomic rates generally increases soil P concentrations, which can increase runoff of soluble P. Along the North Bosque River in central Texas, dairy waste application fields are identified as the most controllable nonpoint source of soluble P in a total maximum daily load. To evaluate P reduction practices for fields high in soil extractable P, edge‐of‐field runoff was measured from paired plots of Coastal bermudagrass (Cynodon dactylon) and sorghum (Sorghum bicolor)/ winter wheat (Triticum spp.). Plots (about 0.4 ha) received manure at P agronomic rates following Texas permit guidelines and commercial N during the pretreatment period. During the post‐treatment period, control plots continued to receive manure at P agronomic rates and commercial N. Treatment plots received only commercial N during the post‐treatment period. Use of only commercial N on soils with high extractable P levels significantly decreased P loadings in edge‐of‐field runoff by at least 40 percent, but runoff concentrations sometimes increased. No notable changes in extractable soil P concentrations were observed after five years of monitoring due to drought conditions limiting forage uptake and removal.