RIVER-QUALITY ASSESSMENTS1

ABSTRACT: In 1972, the U.S. Geological Survey began a pilot program of river-quality assessments. The objectives of the program are (1) to define the character, interrelationships, and apparent causes of existing river-quality problems, and (2) to devise and demonstrate the analytical approaches and the tools and methodologies needed for developing water-quality information that will provide a sound technical basis for planners and managers to use in assessing river-quality problems and evaluating management alternatives. The most noteworthy finding of a pilot assessment of the Willamette River basin, Oregon, was that across-the-board advanced waste treatment was not the answer to the problem of meeting stringent water-quality standards established for the river. The assessment also found that existing water-quality data generally are inadequate for defining the critical cause-effect relationships that control river-quality problems and that intensive, synoptic surveys keyed to local problems and conditions would be required in most river basins to develop an adequate information base for managing important river-quality problems. The study illustrated that rigid nationwide standards and regulations are likely to result in unneeded expenditures in some river basins and in undesirable quality in others.     

A mixture of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and non-ortho polychlorinated biphenyls (PCBs) changed the lipid content of pregnant Long Evans rats

Pregnant Long Evans rats received 1.0 μg/kg of dioxin toxic equivalents (TEQ) by oral gavage on the 15th gestational day (GD 15), using a dosing mixture that contained two polychlorinated dioxins, four polychlorinated furans and three non-ortho polychlorinated biphenyls (PCBs). Rats were sacrificed on GD 16, GD 21 and postnatal day 4 (PND 4). The lipid content of fetus, pup, placenta and maternal liver, serum and adipose tissue were determined. Treated GD 16 and GD 21 fetuses had identical lipid content to the control group, yet the lipid content of treated pups on PND 4 was 32% higher than that of the control group. On the other hand, the lipid content of placenta, liver, and serum from the treated dams was 44–50%, 24%, and 38% lower than that of the control group, respectively. Thus, a low-dose mixture of dioxin-like compounds can cause changes in lipid content. The lipid content of offspring was not affected until they were exposed via lactation.     

A comparative study of prenatal ultrasound findings and post-mortem examination in a tertiary referral centre

This retrospective study compares the findings of prenatal ultrasound, performed in a tertiary fetal medicine centre, with the results of post-mortem examination in pregnancies complicated by suspected fetal abnormality that results in fetal loss. The study was carried out over a year at a teaching hospital, Fetal Medicine Centre and Regional Centre for Perinatal Pathology. Results were directly compared and the level of agreement between the ultrasound and post-mortem findings described. These were classified as having complete agreement; major agreement or major disagreement. The group of cases with major agreement between findings was further divided into those with significant, or minor, additional findings at post-mortem examination. Over the 12-month period, 153 ultrasound cases were identified, of which 47 were also examined by autopsy and were thus suitable for comparison in this study (30.7%). Complete agreement between ultrasound and post-mortem findings was found in 22 cases (46.8%). In 24 cases (51.1%), major agreement between ultrasound and post-mortem findings was seen. Of these, 11 had minor additional findings at post-mortem examination and 13 were found to have significant additional findings at post-mortem (27.7%), adding to the eventual diagnosis. In 12.8% of cases, post-mortem examination provided a definitive diagnosis. Only in one case was there complete discordance in the findings of the ultrasound examination and the autopsy (2.1%). No major disagreement between ultrasound and post-mortem findings was seen in 98% of cases. This study confirms the accuracy of prenatal ultrasound diagnosis in specialist centres, whilst emphasising the continuing importance of post-mortem examination in cases of fetal malformation to refine and, in some cases, define the diagnosis. Copyright © 2004 John Wiley & Sons, Ltd.     

Hydrologic Modeling Uncertainty Resulting From Land Cover Misclassification1

Abstract: A stochastic, spatially explicit method for assessing the impact of land cover classification error on distributed hydrologic modeling is presented. One‐hundred land cover realizations were created by systematically altering the North American Landscape Characterization land cover data according to the dataset’s misclassification matrix. The matrix indicates the probability of errors of omission in land cover classes and is used to assess the uncertainty in hydrologic runoff simulation resulting from parameter estimation based on land cover. These land cover realizations were used in the GIS‐based Automated Geospatial Watershed Assessment tool in conjunction with topography and soils data to generate input to the physically‐based Kinematic Runoff and Erosion model. Uncertainties in modeled runoff volumes resulting from these land cover realizations were evaluated in the Upper San Pedro River basin for 40 watersheds ranging in size from 10 to 100 km² under two rainfall events of differing magnitudes and intensities. Simulation results show that model sensitivity to classification error varies directly with respect to watershed scale, inversely to rainfall magnitude and are mitigated or magnified by landscape variability depending on landscape composition.     

Effects of Metal Mining and Milling on Boundary Waters of Yellowstone National Park, USA

/ Aquatic resources in Soda Butte Creek within Yellowstone National Park, USA, continue to be threatened by heavy metals from historical mining and milling activities that occurred upstream of the park's boundary. This includes the residue of gold, silver, and copper ore mining and processing in the early 1900s near Cooke City, Montana, just downstream of the creek's headwaters. Toxicity tests, using surrogate test species, and analyses of metals in water, sediments, and macroinvertebrate tissue were conducted from 1993 to 1995. Chronic toxicity to test species was greater in the spring than the fall and metal concentrations were elevated in the spring with copper exceeding water quality criteria in 1995. Tests with amphipods using pore water and whole sediment from the creek and copper concentrations in the tissue of macroinvertebrates and fish also suggest that copper is the metal of concern in the watershed. In order to understand current conditions in Soda Butte Creek, heavy metals, especially copper, must be considered important factors in the aquatic and riparian ecosystems within and along the creek extending into Yellowstone National Park.KEY WORDS: Mining; Metals; Toxicity; Biomonitoring; Copper; Yellowstone National Park     

Influence of contrasting larval developmental types upon the population-genetic structure of cheilostome bryozoans

For many sedentary or sessile benthic marine invertebrates the planktonic duration of the larval stage is believed to be a key determinant of the magnitude of genetic differences between populations. An obvious dichotomy in dispersal potential exists within cheilostome bryozoans that develop from either (1) a cyphonautes larva that spends several weeks in the plankton or (2) a brooded coronate larva that settles soon after release from the adult colony. This study characterises the pattern of variation at allozyme loci among British populations of four species of bryozoan—two species with cyphonautes and two with coronate larvae. There is some variation in the estimates of genetic differentiation among similarly separated populations that may be a consequence of non-equilibrium genetic conditions arising from sporadic migration, possibly through dispersal by rafting on macroalgae by mature colonies. Despite this, however, both the level of genetic differentiation between populations and the pattern of migrant exchange correlate with the larval developmental mode. Bryozoan species that brood coronate larvae show higher levels of genetic heterogeneity between populations and significant isolation by distance genetic structure while, by contrast, distance has little or no effect upon the amount of genetic differentiation among populations of bryozoans with cyphonautes larvae. For cheilostome bryozoans, therefore, it appears that genetic differentiation between populations is directly associated with the type of larval development. These data are discussed also with respect to levels of gene diversity and the geological pattern of cheilostome bryozoan species diversity.     

Environmental performance indicators for enhancing environmental management

Traditionally, environmental issues and concerns have been viewed as a constraint to businesses. This has resulted in environmental managers relying heavily on a reactive, compliance-based approach to justify change. Businesses are now recognizing that efficient management in the environmental arena can benefit the entire company and open new opportunities for increased profits. Managers have acknowledged that environmental issues can be integrated into daily business trends and activities. Not only does sound environmental management decrease liability, but also in current markets a “green” image can attract investors and customers. This article shows how one tool that progressive companies are focusing attention on—environmental performance indicators—is being used to convey the current status of environmental issues and improve the management of these issues for the benefit of the company as well as the environment.     

Modeling tracer diffusion in fractured and unfractured, unsaturated, porous media

A proposed tracer diffusion test for the Exploratory Shaft Facility at Yucca Mountain, NV, is modeled. For the proposed test, a solution containing conservative tracers will be introduced into a borehole in the geologic medium of interest. The tracers will diffuse and advect from the saturated source region into the unsaturated matrix in the surrounding tuff. After some time, the borehole is to be overcored, and tracer concentrations in the fluid will be measured in the core as a function of distance from emplacement. The data will be used to evaluate diffusive behavior and to derive effective diffusion coefficients for the tracers in the specific tuff. Numerical simulations are used to study the effects of effective diffusion coefficient, porosity, saturation, and fracturing on tracer transport. Results are reported for numerical simulations of tests in the Topopah Spring Member and the Tuff of Calico Hills, which have significantly different porosities and saturations. The simulations make the following predictions: The spread of tracer during the test will be sensitive to the effective diffusion coefficient of the tracer. Tracer will diffuse farther in the Topopah Spring Member than in the Tuff of Calico Hills because of the former's lower porosity and saturation. Tracer transport by advection into the Topopah Spring Member will be greater than that into the Tuff of Calico Hills because of capillary effects. While advection will be a significant mechanism for tracer penetration into the Topopah Spring tuff, it will be less significant for tracer penetration into the Calico Hills tuff. The proximity of a single vertical fracture to the source region determines its effects on tracer transport, especially if the fracture diverts fluid flowing from the source region into the matrix.     

A statistical comparison of naphthenic acids characterized by gas chromatography-mass spectrometry

Naphthenic acids are complex mixtures of alkyl-substituted acyclic and cycloaliphatic carboxylic acids, with the general chemical formula C_nH_2n+zO₂, where n is the carbon number and Z specifies a homologous family. These acids have a variety of commercial uses, including being used as wood preservatives. They are found in conventional and heavy oils, and in the oil sands of northeastern Alberta, Canada. Naphthenic acids are major contributors to the toxicity of tailings waters that result from the oil sands extraction process. Eight naphthenic acids preparations (four from commercial sources and four from the oil sands operations) were derivatized and analyzed by gas chromatography–mass spectrometry. The composition of each mixture was summarized as a three-dimensional plot of the abundance of specific ions (corresponding to naphthenic acids) versus carbon number (ranging from 5 to 33) and Z family (ranging from 0 to −12). The data in these plots were divided into three groups according to carbon number (group 1 contained carbon numbers 5–14, group 2 contained carbon numbers 15–21, and group 3 contained carbon numbers 22–33). A t-test, using arcsine-transformed data, was applied to compare corresponding groups in samples from various sources. Results of the statistical analyses showed differences between various commercial naphthenic acids preparations, and between naphthenic acids from different oil sands ores and tailings ponds. This statistical approach can be applied to data collected by other mass spectrometry methods.