Bruce N. Wilson

A method for delivery of precise doses of smoked cocaine-base to humans

Despite increasing smoked cocaine-base use, there have been relatively few parametric studies in this area. The major reason for the limited number of studies is the lack of a simple procedure for the administration of precise doses of smoked cocaine-base to human volunteers. This paper describes a new method that allows for the delivery of precise doses of smoked cocaine-base. A complete description of the method and the precision of the administration procedure are presented. Furthermore, a study is described which was undertaken to determine: 1) the reproducibility of peak blood cocaine levels when the same dose of cocaine was given on two separate occasions; and 2) the dose-related effects on smoking topography, biochemical, physiological and subjective measures. Subjects (N = 5) were administered three doses of cocaine-base (10, 20 and 40 mg). Four subjects were given repeated doses of cocaine-base. Subjects were blind to the dose and in most cases randomly assigned to different doses. The results showed: 1) a significant correlation of peak whole blood cocaine concentrations among similar doses within subjects (r = .99); 2) no significant effects of dose on smoking topography; and 3) significant dose effects for whole blood cocaine concentrations, heart rate and systolic blood pressure.

Hydrologic and Water Quality Models: Use, Calibration, and Validation

To provide a common background and platform for consensual development of calibration and validation guidelines, model developers and/or expert users of the commonly used hydrologic and water quality models globally were invited to write technical articles recommending calibration and validation procedures specific to their model. This article introduces a special collection of 22 research articles that present and discuss calibration and validation concepts in detail for 25 hydrologic and water quality models. The main objective of this introductory article is to introduce and summarize key aspects of the hydrologic and water quality models presented in this collection. The models range from field to watershed scales for simulating hydrology, sediment, nutrients, bacteria, and pesticides at temporal scales varying from hourly to annually. Individually, the articles provide model practitioners with detailed, model-specific guidance on model calibration, validation, and use. Collectively, the articles in this collection present a consistent framework of information that will facilitate development of a proposed set of ASABE model calibration and validation guidelines.

Minnesota's approach to lake nutrient criteria development

Abstract Ecoregion-based phosphorus “criteria” that reflect the diversity of lake condition, varying from deep pristine lakes in the north to shallow hypereutrophic lakes in the south, were developed by the Minnesota Pollution Control Agency (MPCA) in the late 1980s. Since then the criteria, including several refinements, have been widely used for local, state, and federal lake watershed management efforts in Minnesota. More recently, the criteria have been used to define thresholds for Clean Water Act Section 303(d) listing of nutrient-impaired lakes and are being advanced as lake standards to protect a wide diversity of beneficial uses. This paper summarizes the evolution of these criteria and describes data and research used in their development. A weight-of-evidence approach describes how this information was used to refine the criteria values.

PERFORMANCE OF EROSION CONTROL PRODUCTS ON A HIGHWAY EMBANKMENT

Unprotected soil at construction sites often results in large rates of erosion. Five different erosion control treatments were tested on the slopes of a highway sedimentation basin to determine their impact on vegetative growth, runoff, and erosion. The treatments were a bare (no treatment) condition, a disk–anchored straw mulch, a wood–fiber blanket, a straw/coconut blanket, and a bonded–fiber matrix product (hydraulically applied). A minimum of three replicates was used for each treatment. Straw mulch was selected as the standard treatment for statistical analyses. The site was planted with native prairie seeds, and the establishment of vegetation was monitored over the growing season. Above–ground biomasses for the bare and straw–mulch treatments were statistically greater than those of the bonded–fiber matrix treatment. Statistically significant differences in above–ground biomass for the other treatments were undetected at the 10% level. Weedy grasses and forbs were the dominant plant species. Runoff and erosion data were collected using a rotating–boom rainfall simulator for spring and fall sets of runs corresponding to little and good vegetative growth, respectively. Runoff depths were generally larger from straw–mulch and bare plots. There were no statistically significant differences in relative runoff depth between the blankets and the bonded–fiber matrix product. Under conditions with little vegetation, erosion from the straw–mulch plots was roughly one–tenth of that from the bare soil plots; erosion from the blanket and bonded–fiber matrix plots was roughly one–tenth of that from the straw–mulch plots. There were no statistically significant differences in relative sediment yield between the blankets and the bonded–fiber matrix. Erosion from bare and straw–mulch treatments was greatly reduced by vegetative growth that occurred between the spring and fall runs.

SHEAR STRESS PARTITIONING FOR IDEALIZED VEGETATED SURFACES

Vegetation and other surface roughness materials partition the shear force of flowing water into a portion acting on the vegetation (vegetal shear) and the remainder acting on the intervening soil surface (particle shear). The fraction acting on the soil surface is directly involved in subsequent particle detachment. The purpose of this study was to directly measure the components of shear stress and to quantify the shear partition for various densities of idealized elements representative of non-submerged rigid vegetation in overland flow. Insight into the magnitude of particle shear and vegetal shear is necessary for understanding the role of vegetation in reducing particle shear and, consequently, reducing potential erosion. Circular cylinders and idealized elements with differences in the rate of change in upstream frontal area with flow depth were used to model vegetation. Detailed spatial and temporal particle shear measurements were made using a unique hydraulic flume and hot-film anemometry. Drag force was measured on individual elements within test arrays. This combination of measurements allowed for direct determination of the shear partition. The tests were conducted on three uniform element densities at discharges of 0.005 and 0.01 m3/s. Element width-to-spacing ratios ranged from 0.04 to 0.20. Over the range of densities studied, particle shear accounted for 13% to 89% of the total shear, indicating that complete surface coverage is not required to significantly reduce the shear stress acting on soil particles. Existing shear partitioning theory, in which the partition is a function of the ratio of element to surface drag coefficients and the roughness density, was found to represent the observed partition reasonably well (mean squared error = 0.036). The results from this study are important for selecting appropriate plant species and densities for erosion control systems.

Plant Growth Component of a Simple Rye Growth Model

Cover cropping practices are being researched to reduce artificial subsurface drainage nitrate-nitrogen (nitrate-N) losses from agricultural lands in the upper Mississippi watershed. A soil-plant-atmosphere simulation model, RyeGro, was developed to quantify the probabilities that a winter rye cover crop will reduce artificial subsurface drainage nitrate-N losses given climatic variability in the region. This article describes the plant growth submodel of RyeGro, Grosub, which estimates biomass production with a radiation use efficiency-based approach for converting intercepted photosynthetically active radiation to biomass. Estimates of nitrogen (N) uptake are based on an empirical plant N concentration curve. The model was calibrated with data from a three-year field study conducted on a Normania clay loam (fine-loamy, mixed, mesic Aquic Haplustoll) soil at Lamberton, Minnesota. The model was validated with data measured from a field trial in St. Paul, Minnesota. The cumulative rye aboveground biomass predictions for the calibration years differed by -0.45, 0.09, and 0.16 Mg ha-1 (-17%, 9%, and 32%), and the plant N uptake predictions differed by -10.5, 8.0, and 4.0 kg N ha-1 (-16%, 30%, and 21%) from the observed values. The predictions of biomass production and N uptake for the validation year varied by -1.4 Mg ha-1 and 16 kg N ha-1 (-27% and 24%) from the values observed in the field study, respectively. A local sensitivity analysis of eight input parameters indicated that model output is most sensitive to the maximum leaf area index and radiation use efficiency parameters. Grosub demonstrated the capability to predict seasonal aboveground biomass production of fall-planted rye in southwestern Minnesota within an accuracy of ±30% in years when production exceeds 1 Mg ha-1 by mid-May, and to predict seasonal rye N uptake within ±25% of observed values.

USE OF BIOLOGICAL INDICATORS IN TMDL ASSESSMENT AND IMPLEMENTATION

Most states in the U.S. have a general water quality standard intended to protect water from all potential pollutants not specifically named or identified in other standards. Biological indicators are used, in part, to assess the level of water quality with respect to this general standard. Under EPA’s Total Maximum Daily Load (TMDL) program, impaired waters based on a biological assessment require an additional step compared with non-biological TMDLs. In non-biological TMDLs, the “pollutant” is typically the parameter being monitored, with a direct link to the impairment. In biological TMDLs, cause and effect must first be established between one or more pollutants and the impacted biological community. This article presents examples of approaches taken in different states to monitor and assess the biological health of our streams based on varying combinations of algal, macroinvertebrate, and fish communities. While fish are the ultimate integrator of lower ecological organisms, their occurrence and abundance has been greatly manipulated by humankind. Periphytic algae are perhaps the fastest responding biological population and can be used for some pollutant-specific diagnoses, but most states lack the expertise required for detailed taxonomic classification. Macroinvertebrates, the most commonly monitored biological community, are abundant in most streams, but most metrics are not diagnostic of specific stressors. Within the TMDL framework, issues are discussed related to setting TMDL targets, linking biological impairments with pollutants, and defining biological target endpoints. Although surrogate measures are often used for setting TMDL target loads, biological recovery is measured against biological endpoints. The use of biological indicators for assessment and development of biological TMDLs can be improved through modeling procedures that better define cause-and-effect relationships, through a better understanding of the limits of restoration, and through a more unified national policy that focuses on restoration.

INSTRUMENTATION TO MEASURE DRAG ON IDEALIZED VEGETAL ELEMENTS IN OVERLAND FLOW

Information on shear stress acting on soil particles is necessary to quantify potential soil erosion. Movement of water across a rough surface generates a resistive force, part of which acts on the large–scale roughness elements while the remainder acts on the intervening soil surface. An important large–scale roughness element is vegetation, which acts to reduce shear stresses on the soil and thereby reduces potential erosion. Insight into the drag force acting on individual vegetative elements is necessary for understanding this dynamic. An instrumentation system was developed to measure the drag force on individual elements representative of vegetation. Vegetative elements were modeled in a hydraulic flume using rigid circular cylinders and idealized shapes to account for differences in the rate of change in upstream frontal area with flow depth. Data were gathered for a horizontal flume and for a 1% flume slope. Flow rates ranged from 0.004 to 0.028 m3s–1 with average flow depths ranging from 1.9 to 9.8 cm and average flow velocities ranging from 0.41 to 1.02 m s–1. Sixteen element shapes were considered, resulting in a total of 80 test scenarios. The test conditions resulted in both partial and complete submergence of the elements. Results are presented as actual drag force and dimensionless drag coefficient. The relationship between drag force divided by velocity squared and upstream projected area is well represented by a straight line for cylinders and all other elements. Drag coefficient is a function of element shape and is represented by an average value over the range of flow depths investigated. The overall error in the estimated drag coefficient is 7.3%.

Drag force parameters of rigid and flexible vegetal elements

This paper compares parameters that characterize vegetation flexibility effects on flow resistance and drag. Drag forces have been measured in a flume for simple cylindrical obstructions of the same shape and size but with different flexibility under several flow conditions. This data set is used to fit drag parameters and to relate their value to flexibility through the Cauchy Number. A formulation is presented where the drag coefficient is evaluated as a function of a new calibration velocity parameter which is related to the elastic modulus of the obstruction. While the use of a Vogel exponent and reference velocity provides a similar response, the reference velocity when used is somewhat nebulous and appears to have a critical impact on the parameter and the drag force calculated. The proposed formulation for drag reduction is more consistently estimated for the range of flexibilities in this study.

Two-zone model for stream and river ecosystems

A mechanistic two-zone model is developed to represent the food web dynamics of stream and river ecosystems by considering the benthic and nonbenthic (or water-column) zones as two separate, but interacting biotopes. Flow processes, solar radiation, and temperature are the dynamic external environmental drivers. State variables are defined to represent the hierarchical levels of detritus, limiting nutrient, vegetation, and invertebrates. The fish trophic level is included as a constant input parameter. Model parameters, constants, and boundary conditions are defined based on watershed as well as channel hydrology, stream geomorphology, and biological activities. Recent advances in ecological science and engineering are used in representing important biogeochemical processes. In particular, the turbulent diffusion, as well as sloughing or detachment, processes are defined based on these recent advancements. The two-zone model was evaluated for a gravel bed prealpine Swiss stream named River Necker with data for the study period of January 1992 through December 1994. The model was able to capture the general trends and magnitudes of the food web state variables. A comprehensive relative sensitivity analysis with five moment-based measures found that approximately 5% of the model parameters were important in predicting benthic vegetation. Results of sensitivity analysis guided the model calibration. Simulated benthic vegetation with the calibrated model, which was obtained by adjusting only four parameters, corresponded with observed data. Hydrology-dependent sloughing and detachment were dominant in determining the response of benthic vegetation and invertebrates. The proposed two-zone food web model is a potentially useful research tool for stream and river ecosystems.