REVIEW OF LAKE RESTORATION PROCEDURES1

ABSTRACT Relevant information on the restoration of lakes is presented. The restoration procedures considered are applicable to the water, the bottom sediments, and aquatic plant improvement. A summary of thirteen (13) suggested methods of restoration are reviewed.     

ON PRECIPITATION SENSOR NETWORK DENSITIES FOR EVALUATING WINTERTIME OROGRAPHIC CLOUD SEEDING EXPERIMENTS1

Principal component analysis is used to investigate density requirements of wintertime orographic cloud seeding experiment precipitation sensor networks. Three passes in the vicinity of Climax, Colorado are studied. The eighteen or more evenly spaced precipitation sensors of each pass are almost completely described by three principal components. These three principal components appear to represent (i) mean precipitation, (ii) slope orientation to storm systems, and (iii) elevation. Evaluation of these principal components is implemented with two distribution-free tests, a proportionality test and the runs test. The results of this study suggest that the loss of experimental information caused by low density precipitation sensor networks may be of little consequence.     

IMPACT ASSESSMENT MODEL FOR CLEAR WATER FISHES EXPOSED TO EXCESSIVELY CLOUDY WATER1

ABSTRACT: A new type of empirical model described here enables real time assessment of impacts caused by excessive water cloudiness as a function of (a) reduced visual clarity (excessive cloudiness) and (b) duration of exposure to cloudy conditions, in fisheries or fish life stages adapted to life in clear water ecosystems. This model takes the familiar form used in earlier suspended sediment dose effect models where z is severity of ill effect (SEV), x is duration of exposure (h), y is black disk sighting range (y BD, m)—a measure of water clarity, a is the intercept, and b and c are slope coefficients. As calibrated in this study the model is Severity of ill effect is ranked on a 15‐step scale that ranges from 0 to 14, where zero represents nil effect and 14 represents 100 percent mortality. This model, based on peer consultation and limited meta analysis of peer reviewed reports, accomplishes the following: (a) identifies the threshold of the onset of ill effects among clear water fishes; (b) postulates the rate at which serious ill effects are likely to escalate as a function of reduced visual clarity and persistence; (c) provides a context (the “visual clarity” matrix, with its cell coordinates) to share and compare information about impacts as a function of visual clarity “climate” (d) demonstrates changes in predator prey interactions at exposures greater than and less than the threshold of direct ill effects; (e) calibrates trout reactive distance (cm) as function of water clarity in the form where y represents reactive distance (cm) and x represents visual clarity (black disk sighting range, cm), and where a and b are intercept and slope respectively, such that (f) identifies black disk sighting range, in meters, and its reciprocal, beam attenuation, as preferred monitoring variables; and (g) provides two additional optical quality variables (Secchi disk extinction distance and turbidity) which, suitably calibrated as they have been in this study, expand the range of monitoring options in situations in which the preferred technology—beam attenuation equipment or black disk sighting equipment—is unavailable or impractical to use. This new model demonstrates the efficacy of peer collaboration and defines new research horizons for its refinement.     

Nitrogen biogeochemistry in the Adirondack Mountains of New York: hardwood ecosystems and associated surface waters

Studies on the nitrogen (N) biogeochemistry in Adirondack northern hardwood ecosystems were summarized. Specific focus was placed on results at the Huntington Forest (HFS), Pancake-Hall Creek (PHC), Woods Lake (WL), Ampersand (AMO), Catlin Lake (CLO) and Hennessy Mountain (HM). Nitrogen deposition generally decreased from west to east in the Adirondacks, and there have been no marked temporal changes in N deposition from 1978 through 1998. Second-growth western sites (WL, PHC) had higher soil solution NO(3-) concentrations and fluxes than the HFS site in the central Adirondacks. Of the two old-growth sites (AMO and CLO), AMO had substantially higher NO(3-) concentrations due to the relative dominance of sugar maple that produced litter with high N mineralization and nitrification rates. The importance of vegetation in affecting N losses was also shown for N-fixing alders in wetlands. The Adirondack Manipulation and Modeling Project (AMMP) included separate experimental N additions of (NH4)2SO4 at WL, PHC and HFS and HNO3 at WL and HFS. Patterns of N loss varied with site and form of N addition and most of the N input was retained. For 16 lake/watersheds no consistent changes in NO(3-) concentrations were found from 1982 to 1997. Simulations suggested that marked NO(3-) loss will only be manifested over extended periods. Studies at the Arbutus Watershed provided information on the role of biogeochemical and hydrological factors in affecting the spatial and temporal patterns of NO(3-) concentrations. The heterogeneous topography in the Adirondacks has generated diverse landscape features and patterns of connectivity that are especially important in regulating the temporal and spatial patterns of NO(3-) concentrations in surface waters.     

Field efficacy and baseline toxicities of pyriproxifen, acetamiprid, and diafenthiuron against Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) in Burkina Faso (West Africa)

Bioassays were conducted in 2001 and 2002 to estimate toxicities and dose-response relationships of 24 Bemisica tabaci Gennadius populations to pyriproxifen, acemitaprid, and diafenthiuron. LC50s ranging from 0.014 to 0.096 mgL(-1), 0.60 to 1.3 mgL(-1), and 3.5 to 6.7 mgL(-1) were observed respectively for pyriproxifen, acemitaprid, and diafenthiuron. These LC50s much lower than the field doses recommended for each compound. A fast increase in rates of mortality within a narrow range of lethal concentrations was observed for each compound. indicating that all three compounds were highly effective at killing whiteflies. In a separate experiment, pyriproxifen, acemitaprid, and diafenthiuron were tested in 2001 and 2002 to compare their effectiveness and assess their impact on parasitism in the field. In both years all three compounds significantly prevented B. tabaci populations from reaching economic injury levels in cotton and minimized adverse effects on parasitism. Our results provide for the first time baseline toxicological, field efficacy, and effect on parasitism data for pyriproxifen, acemitaprid, and diafenthiuron against B. tabaci in West Africa. These compounds should be included in a resistance management program of the cotton pest complex and their use should be restricted to prevent the building of resistance in B. tabaci populations.     

The Use of Natural Systems to Remediate Groundwater: Department of Energy Experience at the Savannah River Site

Natural remediation is moving toward the forefront as engineers clean groundwater at the Savannah River Site (SRS), a major Department of Energy (DOE) installation near Aiken, South Carolina. This article reviews two successful, innovative remediation methods currently being deployed: biosparging to treat chlorinated solvents and phytoremediation to address tritium in groundwater. The biosparging system reintroduces oxygen into the groundwater and injects nutrient compounds for in‐situ remediation. The system has greatly reduced the concentrations of trichloroethylene (TCE) and vinyl chloride in wells downgradient from a sanitary landfill (SLF). Phytoremediation is an emerging technology that promises effective and inexpensive cleanup of certain hazardous wastes. Using natural processes, plants can break down, trap and hold, or transpire contaminants. This article discusses the use of phytoremediation to reduce the discharge of tritium to an on‐site stream at SRS. © 2002 Wiley Periodicals Inc. *     

Historical analysis of monitored natural attenuation: A survey of 191 chlorinated solvent sites and 45 solvent plumes

A survey of experts in the application of natural attenuation was conducted to better understand how monitored natural attenuation (MNA) is being applied at chlorinated solvent sites. Thirty‐four remediation professionals provided general information for 191 sites where MNA was evaluated, and site‐specific data for 45 chlorinated solvent plumes being remediated by MNA. Respondents indicated that MNA was precluded as a remedy at only 23 percent of all sites where evaluated as a remedial option. Leading factors excluding MNA as a remedial approach were the presence of an expanding plume and an unreasonably long estimated remediation time frame. MNA is being used as the sole remedy at about 30 percent of the sites, and 33 percent are implementing MNA in conjunction with source zone remediation. The remaining sites are implementing MNA with plume remediation (13 percent), source containment (9 percent), or some other strategy (16 percent). © 2004 Wiley Periodicals, Inc.     

SAMPLING STRATEGIES FOR ESTIMATING ACUTE AND CHRONIC EXPOSURES OF PESTICIDES IN STREAMS1

ABSTRACT: The Food Quality Protection Act of 1996 requires that human exposure to pesticides through drinking water be considered when establishing pesticide tolerances in food. Several systematic and seasonally weighted systematic sampling strategies for estimating pesticide concentrations in surface water were evaluated through Monte Carlo simulation, using intensive datasets from four sites in northwestern Ohio. The number of samples for the strategies ranged from 4 to 120 per year. Sampling strategies with a minimal sampling frequency outside the growing season can be used for estimating time weighted mean and percentile concentrations of pesticides with little loss of accuracy and precision, compared to strategies with the same sampling frequency year round. Less frequent sampling strategies can be used at large sites. A sampling frequency of 10 times monthly during the pesticide runoff period at a 90 km² basin and four times monthly at a 16,400 km² basin provided estimates of the time weighted mean, 90^th, 95^th, and 99^th percentile concentrations that fell within 50 percent of the true value virtually all of the time. By taking into account basin size and the periodic nature of pesticide runoff, costs of obtaining estimates of time weighted mean and percentile pesticide concentrations can be minimized.     

Role of refugia in recovery from disturbances: Modern fragmented and disconnected river systems

Habitats or environmental factors that convey spatial and temporal resistance and/or resilience to biotic communities that have been impacted by biophysical disturbances may be called refugia. Most refugia in rivers are characterized by extensive coupling of the main channel with adjacent streamside forests, floodplain features, and groundwater. These habitats operate at different spatial scales, from localized particles, to channel units such as pools and riffles, to reaches and longer sections, and at the basin level. A spatial hierarchy of different physical components of a drainage network is proposed to provide a context for different refugia. Examples of refugia operating at different spatial scales, such as pools, large woody debris, floodplains, below dams, and catchment basins are discussed. We hope that the geomorphic context proposed for examining refugia habitats will assist in the conservation of pristine areas and attributes of river systems and also allow a better understanding of rehabilitation needs in rivers that have been extensively altered.