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At least 145 records · Page 8Linked to original sources
USGS2015

Simulation of groundwater flow and chloride transport in the “1,200-foot” sand with scenarios to mitigate saltwater migration in the “2,000-foot” sand in the Baton Rouge area, Louisiana

Groundwater withdrawals have caused saltwater to encroach into freshwater-bearing aquifers beneath Baton Rouge, Louisiana. The 10 aquifers beneath the Baton Rouge area, which includes East and West Baton Rouge Parishes, Pointe Coupee Parish, and East and West Feliciana Parishes, provided about 184.3 million gallons per day (Mgal/d) for public supply and industrial use in 2012. Groundwater withdrawals from the “1,200-foot” sand in East Baton Rouge Parish have caused water-level drawdown as large as 177 feet (ft) north of the Baton Rouge Fault and limited saltwater encroachment from south of the fault. The recently developed groundwater model for simulating transport in the “2,000-foot” sand was rediscretized to also enable transport simulation within the “1,200-foot” sand and was updated with groundwater withdrawal data through 2012. The model was recalibrated to water-level observation data through 2012 with the parameter-estimation code PEST and calibrated to observed chloride concentrations at observation wells within the “1,200-foot” sand and “2,000-foot” sand. The model is designed to evaluate strategies to control saltwater migration, including changes in the distribution of groundwater withdrawals and installation of scavenger wells to intercept saltwater before it reaches existing production wells. Seven hypothetical scenarios predict the effects of different groundwater withdrawal options on groundwater levels and the transport of chloride within the “1,200-foot” sand and the “2,000-foot” sand during 2015–2112. The predicted water levels and concentrations for all scenarios are depicted in maps for the years 2047 and 2112. The first scenario is a base case for comparison to the six other scenarios and simulates continuation of 2012 reported groundwater withdrawals through 2112 (100 years). The second scenario that simulates increased withdrawals from industrial wells in the “1,200-foot” sand predicts that water levels will be 12–25 ft lower by 2047 and that there will be a negligible difference in chloride concentrations within the “1,200-foot” sand. The five other scenarios simulate the effects of various withdrawal schemes on water levels and chloride concentrations within the “2,000-foot” sand. Amongst these five other scenarios, three of the scenarios simulate only various withdrawal reductions, whereas the two others also incorporate withdrawals from a scavenger well that is designed to extract salty water from the base of the “2,000-foot” sand. Two alternative pumping rates (2.5 Mgal/d and 1.25 Mgal/d) are simulated in each of the scavenger-well scenarios. For the “2,000-foot” sand scenarios, comparison of the predicted effects of the scenarios is facilitated by graphs of predicted chloride concentrations through time at selected observation wells, plots of salt mass in the aquifer through time, and a summary of the predicted plume area and average concentration. In all scenarios, water levels essentially equilibrate by 2047, after 30 years of simulated constant withdrawal rates. Although predicted water-level recovery within the “2,000-foot” sand is greatest for the scenario with the greatest reduction in groundwater withdrawal from that aquifer, the scavenger-well scenarios are most effective in mitigating the future extent and concentration of the chloride plume. The simulated scavenger-well withdrawal rate has more influence on the plume area and concentration than do differences among the scenarios in industrial and public-supply withdrawal rates.

Louisiana, Mississippi↗
USGS1992

Diflubenzuron Hazards to Fish, Wildlife and Invertebrates: A Synoptic Review

Diflubenzuron (1(4chlorophenyl)3(2,6difluorobenzoyl)urea), also known as dimilin, is a potent broad spectrum insect growth regulator that interferes with chitin synthesis at time of molting and is effective in controlling immature stages of insects. Diflubenzuron was approved for domestic use in 1976 to control gypsy moth (Lymantria dispar), and in 1979 against the cotton boll weevil (Anthonomus grandis). By 1989 this compound was also registered for domestic use against mosquitos, forest Lepidoptera, mushroom flies, and leaf-eating insect pests of citrus, woody ornamentals, vegetables, and fruit. Diflubenzuron seldom persists for more than a few days in soil and water. When used properly in forest management, it is unlikely to be leached into ground water from the application site. Degradation in water and soil is most rapid when small particle formulations are applied; microorganisms are abundant; and at elevated pH, temperature, and organic loading. Chemical and biological processes initially yield 2,6difluorobenzoic acid and 4chlorophenylurea.

Contaminant Hazard Reviews↗
USGS2017

Leaching and sorption of neonicotinoid insecticides and fungicides from seed coatings

Seed coatings are a treatment used on a variety of crops to improve production and offer protection against pests and fungal outbreaks. The leaching of the active ingredients associated with the seed coatings and the sorption to soil was evaluated under laboratory conditions using commercially available corn and soybean seeds to study the fate and transport of these pesticides under controlled conditions. The active ingredients (AI) included one neonicotinoid insecticide (thiamethoxam) and five fungicides (azoxystrobin, fludioxonil, metalaxyl, sedaxane thiabendazole). An aqueous leaching experiment was conducted with treated corn and soybean seeds. Leaching potential was a function of solubility and seed type. The leaching of fludioxonil, was dependent on seed type with a shorter time to equilibrium on the corn compared to the soybean seeds. Sorption experiments with the treated seeds and a solution of the AIs were conducted using three different soil types. Sorption behavior was a function of soil organic matter as well as seed type. For most AIs, a negative relationship was observed between the aqueous concentration and the log K oc . Sorption to all soils tested was limited for the hydrophilic pesticides thiamethoxam and metalaxyl. However, partitioning for the more hydrophobic fungicides was dependent on both seed type and soil properties. The mobility of fludioxonil in the sorption experiment varied by seed type indicating that the adjuvants associated with the seed coating could potentially play a role in the environmental fate of fludioxonil. This is the first study to assess, under laboratory conditions, the fate of pesticides associated with seed coatings using commercially available treated seeds. This information can be used to understand how alterations in agricultural practices (e.g., increasing use of seed treatments) can impact the exposure (concentration and duration) and potential effects of these chemicals to aquatic and terrestrial organisms.

Journal of Environmental Science and Health - Part↗
USGS2020

Parsing the effects of demography, climate, and management on recurrent brucellosis outbreaks in elk

1. Zoonotic pathogens can harm human health and well-being directly or by impacting livestock. Pathogens that spillover from wildlife can also impair conservation efforts if humans perceive wildlife as pests. Brucellosis, caused by the bacterium Brucella abortus, circulates in elk and bison herds of the Greater Yellowstone Ecosystem and poses a risk to cattle and humans. Our goal was to understand the relative effects of climatic drivers, host demography, and management control programs on disease dynamics. 2. Using >20 years of serologic, demographic, and environmental data on brucellosis in elk, we built stochastic compartmental models to assess the influences of climate forcing, herd immunity, population turnover, and management interventions on pathogen transmission. Data were collected at feedgrounds visited in winter by free-ranging elk in Wyoming, USA. 3. Snowpack, hypothesized as a driver of elk aggregation and thus brucellosis transmission, was strongly correlated across feedgrounds. We expected this variable to drive synchronized disease dynamics across herds. Instead, we demonstrate asynchronous epizootics driven by variation in demographic rates. 4. We evaluated the effectiveness of test-and-slaughter of seropositive female elk at two feedgrounds. Test-and-slaughter temporarily reduced herd-level seroprevalence but likely reduced herd immunity while removing few infectious individuals, resulting in subsequent outbreaks once the intervention ceased. We simulated an alternative strategy of removing seronegative female elk and found it would increase herd immunity, yielding fewer infections. We evaluated a second experimental treatment wherein feeding density was reduced at one feedground, but we found no evidence for an effect despite a decade of implementation. 5. Synthesis and applications: Positive serostatus is often weakly correlated with infectiousness but is nevertheless used to make management decisions including lethal removal in wildlife disease systems. We show how this can have adverse consequences whereas efforts that maintain herd immunity can have longer-term protective effects. Climatic drivers may not result in synchronous disease dynamics across populations unless vital rates are also similar because demographic factors have a large influence on disease patterns.

Idaho, Montana, Wyoming↗
USGS2026

An evaluation of next-generation biological control methods for the invasive brown treesnake in the Mariana Islands

The brown treesnake (BTS) invasion in Guam continues to cause extensive ecological and economic damage, yet existing control tools cannot achieve islandwide suppression or eradication, highlighting the need for new strategies. This review evaluates the feasibility of classical and genetic biocontrol approaches for BTS and identifies priority knowledge gaps. Classical biocontrol, which relies on pathogens or parasites from a pest’s native range, has had limited success in vertebrates, though certain viruses may hold potential. For BTS, prior work has identified candidate agents, including hemogregarines and paramyxoviruses, but major uncertainties remain in transmission, specificity, long term efficacy, and ecological risk. Theoretical models suggest that moderately virulent pathogens may offer the strongest potential for sustained suppression, with Ophidian paramyxoviruses emerging as a leading prospect, though substantial empirical research is still required. Genetic biocontrol offers additional possibilities, including gene drives that could bias inheritance, reduce fertility, or skew sex ratios. Self sustaining homing and shredding drives could theoretically produce long term reductions, while “enhanced” self limiting systems may provide geographically restricted alternatives. Approaches involving genetically modified prey and toxic males that shorten female lifespan through mating may have future relevance but require major development and validation. Risks across genetic strategies include unintended spread, ecological side effects, technical constraints such as producing engineered snakes, potential resistance, and regulatory complexity. Because feasibility depends on societal acceptance, the review emphasizes the need for early engagement with Guam’s local and Indigenous communities, whose perspectives will shape future development and implementation. Key research priorities include improved modeling, native range genomic characterization of BTS, expanded pathogen surveys, advances in BTS genetic tools and captive rearing methods, and further exploration of both classical pathogen candidates and genetically engineered prey systems. Collectively, the review concludes that classical and genetic biocontrol hold promise for long term, cost effective BTS suppression, but substantial scientific, ethical, ecological, and social groundwork remains before deployment.

Hawai’i Cooperative Fishery Research Unit Technica↗
USGS1993

The common wolf snake, Lycodon aulicus capucinus, a recent colonist of Christmas Island in the Indian Ocean

The discovery of the common wolf snake, Lycodon aulicus capucinus , on Christmas I . in the Indian Ocean suggests that individuals of the species have colonised the island recently. On the basis of biological information for this widespread colubrid snake and for the brown tree snake, Boiga irregularis, a well-documented pest species on Guam, the establishment of the common wolf snake would pose a severe threat to the native fauna and ecology of Christmas I. Immediate research is needed to document the spread of the snake, to evaluate its effects on other fauna, and to control or eradicate the species before it becomes firmly established.

Christmas Island↗
USGS2010

Agronomic and environmental implications of enhanced s-triazine degradation

Novel catabolic pathways enabling rapid detoxification of s -triazine herbicides have been elucidated and detected at a growing number of locations. The genes responsible for s -triazine mineralization, i.e. atzABCDEF and trzNDF , occur in at least four bacterial phyla and are implicated in the development of enhanced degradation in agricultural soils from all continents except Antarctica. Enhanced degradation occurs in at least nine crops and six crop rotation systems that rely on s -triazine herbicides for weed control, and, with the exception of acidic soil conditions and s -triazine application frequency, adaptation of the microbial population is independent of soil physiochemical properties and cultural management practices. From an agronomic perspective, residual weed control could be reduced tenfold in s -triazine-adapted relative to non-adapted soils. From an environmental standpoint, the off-site loss of total s -triazine residues could be overestimated 13-fold in adapted soils if altered persistence estimates and metabolic pathways are not reflected in fate and transport models. Empirical models requiring soil pH and s -triazine use history as input parameters predict atrazine persistence more accurately than historical estimates, thereby allowing practitioners to adjust weed control strategies and model input values when warranted.

Pest Management Science↗
USGS2026

Toxicity of synergized permethrin residues in cattle dung to two temperate dung beetle species after application of common livestock pour-on treatment

Essential to pasture health, dung beetles (Coleoptera: Scarabaeidae) provide key ecosystem services across natural and managed rangeland habitats. Insecticide residues in livestock dung can negatively impact dung beetle populations, and synergized pyrethroid products are commonly used to combat resistant pest fly populations. Here, permethrin residues were measured by GC-MS/MS in fresh cattle feces on Days −2 (pretreatment), 4, 8, 16, and 30 after the label rate application of a formulated pour-on treatment (a.i. 5% permethrin, 5% piperonyl butoxide [PBO]). Mean (± SE) measured permethrin concentrations were the highest on Day 4 at 1400 ± 360 ng of permethrin/g of dung (dry weight) with a maximum concentration of 2200 ng/g. Approximately, 99% of applied permethrin was excreted by Day 16, with no detection by Day 30. Field-collected dung was used in a 48-hour toxicity test and with three treatment groups (control [Day −2], low risk [Day 16], and high risk [Day 4]). Two temperate dung beetle species were tested: Onthophagus pennsylvanicus Harold and Canthon chalcites Haldeman. Mean (± SE) mortality of O. pennsylvanicus was 28 ± 5% and 58 ± 13% for low and high risk treatments, respectively. Mean (± SE) mortality of C. chalcites was lower than O. pennsylvanicus with 10 ± 4% and 40 ± 10% for low and high risk treatments, respectively. PBO was detected on Days 4 and 8, and the permethrin:PBO ratio was 10:1 on Day 4, i.e., high risk treatment. Data presented highlight episodic risks of pour-on products and support threshold-based, integrated pest management approaches.

Oklahoma↗
USGS2021

The contribution of land cover change to the decline of honey yields in the Northern Great Plains

Decreased availability of forage, as well as increased pesticide exposure, are important factors in the decline of honey bee health. Here, we isolate land cover transitions and their effect on honey production at 160 commercial apiaries in the Northern Great Plains. We found that land cover changes from 2008 to 2012 caused an annual decline in honey yields of 0.9% in the study area. Transitions from grassland to soybean (but not corn) were particularly detrimental to honey yields, potentially due to bee contact with pesticides within and around agricultural fields. When our results are applied to known apiary locations across all of North Dakota (U.S.A.), we estimate a 2.5% (1.6 million USD) decline in 2012 honey yields due to land cover changes occurring between 2008 and 2012. Even when controlling for changes in land cover, we found that on average colonies in the study area experienced a 14% annual decline in honey yields. We discuss possible explanations for these non-land-cover-related honey yield declines, including changing economic conditions (e.g. pollination services), changes in land management (e.g. pesticides), and increases in pests or diseases.

South Dakota↗
USGS2024

Parameter ESTimation with the Gauss–Levenberg–Marquardt algorithm: An intuitive guide

In this paper, we review the derivation of the Gauss–Levenberg–Marquardt (GLM) algorithm and its extension to ensemble parameter estimation. We explore the use of graphical methods to provide insights into how the algorithm works in practice and discuss the implications of both algorithm tuning parameters and objective function construction in performance. Some insights include understanding the control of both parameter trajectory and step size for GLM as a function of tuning parameters. Furthermore, for the iterative Ensemble Smoother (iES), we discuss the importance of noise on observations and show how iES can cope with non-unique outcomes based on objective function construction. These insights are valuable for modelers using PEST, PEST++, or similar parameter estimation tools.

Groundwater↗
USGS1954

Marsh and aquatic weed problems in wildlife habitat

To most people, the word weeds signifies pest plants of the farm, roadside, or other upland areas. However, weeds also occur on, under, or near water. Fifteen million dollars have been spent on a single aquatic nuisance in the South—the prolific water-hyacinth which clogs navigable streams and lakes with its growth. Hundreds of thousands of dollars have also been expended on control of the waterchestnut or water caltrop in the Potomac River. In addition, smaller-scale local campaigns are continuing against cattails, reeds, giant cutgrass, maidencane, alligatorweed, needlerush, lotus, rose-mallows, willows, alders, buttonbush, and similar weeds that interfere with land use for recreation, irrigation, or other purposes. Since control of marsh and aquatic plants in wildlife habitat is an unfamiliar activity to most weed workers, broad aspects of its what, why , and how will be explained briefly.

Weeds↗
USGS2025

Decision analysis of Integrated Pest Management: A case study on invasive sea lamprey in the Great Lakes Basin

Integrated Pest Management (IPM) provides a powerful framework for addressing threats to human well-being caused by nuisance species including invasives. We examined the hypothesis that adaptive management could erode barriers to IPM implementation by developing a decision-analytic adaptive management framework for invasive sea lamprey ( Petromyzon marinus ) IPM in the Laurentian Great Lakes of North America. The framework addressed objectives associated with coordinating multiple sea lamprey control actions at the regional scale and objectives associated with internal validity of control actions. We reduced the scope of possible management actions by orders of magnitude to the set of 6432 alternatives expected to be both socially acceptable and technically feasible. Using utility theory, we identified the management actions that optimized expected utility for all possible objective weighting schemes that considered tradeoffs between maximizing learning about control tactic efficacy and minimizing cost to the IPM program. Sensitivity analyses revealed that assumptions about the social acceptability of deploying electric weirs to control invasive sea lamprey influenced selection of the optimal control action, suggesting that resolving this source of uncertainty through iterative application of the framework may lead to improved sea lamprey control outcomes. Overall, we found that adaptive management enabled learning processes useful for overcoming barriers to IPM of invasive sea lamprey. It formalized learning about sea lamprey control tactic efficacy as an objective of the IPM institution, questioned previously held assumptions about what constitutes a viable control strategy, and enabled a management experiment with temporal and spatial replication.

Michigan, Ontario, Wisconsin↗
USGS2007

Short-term disruption of a leafy spurge (Euphorbia esula) biocontrol program following herbicide application

Integrated pest management (IPM) for invasive plant species is being advocated by researchers and implemented by land managers, but few studies have evaluated the success of IPM programs in natural areas. We assessed the relative effects of components of an IPM program for leafy spurge (Euphorbia esula), an invasive plant, at Theodore Roosevelt National Park, North Dakota. Effects of herbicides on leafy spurge abundance and on dynamics of flea beetles (Aphthona spp.) used to control leafy spurge were evaluated over three field seasons following herbicide application. We monitored leafy spurge-infested plots with established flea beetle populations that had received picloram plus 2,4-D in September 1997 or 1998, imazapic in September 1998, versus those with no chemical treatment. Mature stem counts did not differ significantly between treated and untreated plots in 2001, suggesting that leafy spurge stands had recovered from herbicide treatment. Flea beetles were less abundant on plots with a history of herbicide treatment. Structural equation models indicated that in 2000 negative correlations between relative abundances of the two flea beetle species were greater on plots that had received herbicide treatments than on those that had not, but by 2001 no differences were apparent between treated and untreated plots. These results suggest that the most effective component of IPM for leafy spurge at this site is biological control. All herbicide effects we observed were short-lived, but the increased negative correlation between flea beetle relative abundances during 2000 implies that herbicide application may have temporarily disrupted an effective biological control program at this site. ?? 2006 Elsevier Inc. All rights reserved.

Biological Control↗
USGS2020

Eradication of peste des petits ruminants and the wildlife-livestock interface

Growing evidence suggests that multiple wildlife species can be infected with peste des petits ruminants virus (PPRV), with important consequences for the potential maintenance of PPRV in communities of susceptible hosts, and the threat that PPRV may pose to the conservation of wildlife populations and resilience of ecosystems. Significant knowledge gaps in the epidemiology of PPRV across the ruminant community (wildlife and domestic), and the understanding of infection in wildlife and other atypical host species groups (e.g., camelidae, suidae, and bovinae) hinder our ability to apply necessary integrated disease control and management interventions at the wildlife-livestock interface. Similarly, knowledge gaps limit the inclusion of wildlife in the FAO/OIE Global Strategy for the Control and Eradication of PPR, and the framework of activities in the PPR Global Eradication Programme that lays the foundation for eradicating PPR through national and regional efforts. This article reports on the first international meeting on, “Controlling PPR at the livestock-wildlife interface,” held in Rome, Italy, March 27–29, 2019. A large group representing national and international institutions discussed recent advances in our understanding of PPRV in wildlife, identified knowledge gaps and research priorities, and formulated recommendations. The need for a better understanding of PPRV epidemiology at the wildlife-livestock interface to support the integration of wildlife into PPR eradication efforts was highlighted by meeting participants along with the reminder that PPR eradication and wildlife conservation need not be viewed as competing priorities, but instead constitute two requisites of healthy socio-ecological systems.

Frontiers in Veterinary Science↗
USGS2014

Hydrologic conditions in urban Miami-Dade County, Florida, and the effect of groundwater pumpage and increased sea level on canal leakage and regional groundwater flow

The extensive and highly managed surface-water system in southeastern Florida constructed during the 20th Century has allowed for the westward expansion of urban and agricultural activities in Miami-Dade County. In urban areas of the county, the surface-water system is used to (1) control urban flooding, (2) supply recharge to production well fields, and (3) control seawater intrusion. Previous studies in Miami-Dade County have determined that on a local scale, leakage from canals adjacent to well fields can supply a large percentage (46 to 78 percent) of the total groundwater pumpage from production well fields. Canals in the urban areas also receive seepage from the Biscayne aquifer that is derived from a combination of local rainfall and groundwater flow from Water Conservation Area 3 and Everglades National Park, which are west of urban areas of Miami-Dade County. To evaluate the effects of groundwater pumpage on canal leakage and regional groundwater flow, the U.S. Geological Survey (USGS) developed and calibrated a coupled surface-water/groundwater model of the urban areas of Miami-Dade County, Florida. The model was calibrated by using observation data collected from January 1997 through December 2004. The model calibration was verified using observation data collected from January 2005 through December 2010. A 1-year warmup period (January 1996 through December 1996) was added prior to the start of the calibration period to reduce the effects of inaccurate initial conditions on model calibration. The model is designed to simulate surface-water stage and discharge in the managed canal system and dynamic canal leakage to the Biscayne aquifer as well as seepage to the canal from the aquifer. The model was developed using USGS MODFLOW–NWT with the Surface-Water Routing (SWR1) Process to simulate surface-water stage, surface-water discharge, and surface-water/groundwater interaction and the Seawater Intrusion (SWI2) Package to simulate seawater intrusion, respectively. Automated parameter estimation software (PEST) and highly parameterized inversion techniques were used to calibrate the model to observed surface-water stage, surface-water discharge, net surface-water subbasin discharge, and groundwater level data from 1997 through 2004 by modifying hydraulic conductivity, specific storage coefficients, specific yield, evapotranspiration parameters, canal roughness coefficients (Manning’s n values), and canal leakance coefficients. Tikhonov regularization was used to produce parameter distributions that provide an acceptable fit between model outputs and observation data, while simultaneously minimizing deviations from preferred values based on field measurements and expert knowledge. Analytical and simulated water budgets for the period from 1996 through 2010 indicate that most of the water discharging through the salinity control structures is derived from within the urban parts of the study area and that, on average, the canals are draining the Biscayne aquifer. Simulated groundwater discharge from the urban areas to the coast is approximately 7 percent of the total surface-water inflow to Biscayne Bay and is consistent with previous estimates of fresh groundwater discharge to Biscayne Bay. Simulated groundwater budgets indicate that groundwater pumpage in some surface-water basins ranges from 13 to 27 percent of the sum of local sources of groundwater inflow. The largest percentage of groundwater pumpage to local sources of groundwater inflow occurs in the basins that have the highest pumping rates (C–2 and C–100 Basins). The ratio of groundwater pumpage to simulated local sources of groundwater inflow is less than values calculated in previous local-scale studies. The position of the freshwater-seawater interface at the base of the Biscayne aquifer did not change notably during the simulation period (1996–2010), consistent with the similar positions of the interface in 1984, 1995, and 2011 under similar hydrologic and groundwater pumping conditions. Landward movement of the freshwater-seawater interface above the base of the aquifer is more prone to occur during relatively dry years. The model was used to evaluate the effect of increased groundwater pumpage and (or) increased sea level on canal leakage, regional groundwater flow, and the position of the freshwater-seawater interface. Permitted groundwater pumping rates, which generally exceed historical groundwater pumping rates, were used for Miami-Dade County Water and Sewer Department groundwater pumping wells in the base-case future scenario. Base-case future and increased pumping scenario results suggest seawater intrusion may occur at the Miami-Springs well field if the Miami Springs, Hialeah, and Preston well fields are operated using current permitted groundwater pumping rates. Scenario simulations also show that, in general, the canal system limits the adverse effects of proposed groundwater pumpage increases on water-level changes and saltwater intrusion. Proposed increases (up to a 7 percent increase) in groundwater pumpage do not have a notable effect on movement of the freshwater-seawater interface. Increased groundwater pumpage increased lateral groundwater inflow into basins subject to additional groundwater pumpage; however, most (55 percent) of the additional groundwater extracted from pumping wells was supplied by changes in canal seepage and leakage in urban areas of the model. Increased sea level caused increased water-table elevations in urban areas and decreased hydraulic gradients across the system; the largest increases in water-table elevations occurred seaward of the salinity control structures. The extent of flood-prone areas and the percentage of time water-table elevations in flood-prone areas were less than 0.5 foot below land surface increased with increased sea level. Increased sea level also resulted in landward migration of the freshwater-seawater interface; the largest changes in the position of the interface occurred seaward of the salinity control structures except in parts of the model area that were inundated by increased sea level. Decreased water-table gradients reduced groundwater inflow, groundwater outflow, canal exchanges, surface-water inflow, and surface-water outflow through salinity control structures. Results for the scenario that evaluated the combination of increased groundwater pumpage and increased sea level did not differ substantially from the scenario that evaluated increased sea level alone. Groundwater inflow, groundwater outflow, and canal exchanges were reduced in urban areas of the study area as a result of decreased water-table gradients across the system, although reductions were less than those in the increased sea-level scenario. The decline in groundwater levels caused by increased groundwater pumpage was less under the increased sea-level scenario than under the increased groundwater-pumpage scenario. The largest reductions in surface-water outflow from the salinity control structures occurred with increased sea level and increased groundwater pumpage. The model was designed specifically to evaluate the effect of groundwater pumpage on canal leakage at the surface-water-basin scale and thus may not be appropriate for (1) predictions that are dependent on data not included in the calibration process (for example, subdaily simulation of high-intensity events and travel times) and (or) (2) hydrologic conditions that are substantially different from those during the calibration and verification periods. The reliability of the model is limited by the conceptual model of the surface-water and groundwater system, the spatial distribution of physical properties, the scale and discretization of the system, and specified boundary conditions. Some of the model limitations are manifested in model errors. Despite these limitations, however, the model represents the complexities of the interconnected surface-water and groundwater systems that affect how the systems respond to groundwater pumpage, sea-level rise, and other hydrologic stresses. The model also quantifies the relative effects of groundwater pumpage and sea-level rise on the surface-water and groundwater systems.

Florida↗
USGS2013

Chapter A: Summary and findings

The Agency for Toxic Substances and Disease Registry (ATSDR) is conducting epidemiological studies to evaluate the potential for health effects from exposures to volatile organic compounds (VOCs) in finished water supplied to family housing units at U.S. Marine Corps Base Camp Lejeune, North Carolina (USMCB Camp Lejeune). The core period of interest for the epidemiological studies is 1968– 1985. VOCs of major interest to the epidemiological studies include tetrachloroethylene (PCE), trichloroethylene (TCE), trans -1,2-dichloroethylene (1,2-tDCE), vinyl chloride (VC), and benzene. Eight water-distribution systems have supplied or currently (2013) are supplying finished water to family housing and other facilities at USMCB Camp Lejeune. The three distribution systems of interest to this study—Tarawa Terrace, Hadnot Point, and Holcomb Boulevard—have historically supplied finished water to the majority of family housing units at the Base. Historical exposure data needed for the epidemiological studies are limited or unavailable. To obtain estimates of historical exposure, water-modeling methods are used to quantify concentrations of particular contaminants in finished water and to compute the level and duration of human expo- sure to contaminated finished water. During 2007–2009, ATSDR published historical reconstruction results for contaminants delivered in finished water to Tarawa Terrace family housing areas and vicinity. Corresponding results for Hadnot Point and Holcomb Boulevard family housing areas and vicinity are presented here as a series of reports supporting ATSDR’s health studies at USMCB Camp Lejeune. These reports and associated supplements provide comprehensive descriptions of information, data analyses and interpretations, and modeling results used to reconstruct historical contaminant concentration levels in finished water delivered within the service areas of the Hadnot Point and Holcomb Boulevard water treatment plants (WTPs) and vicinities. This report, Chapter A: Summary and Findings, summarizes analyses and results of reconstructed VOC concentrations in groundwater, in water-supply wells, and in finished water delivered by the Hadnot Point WTP (HPWTP) and Holcomb Boulevard WTP (HBWTP) to family housing areas and vicinities. Methods and approaches to complete the historical reconstruction process for the Hadnot Point–Holcomb Boulevard study area included (1) information discovery and data mining, (2) three-dimensional, steady-state (predevelopment) and transient groundwater-flow modeling using MODFLOW-2005 and objective parameter estimation using PEST-12, (3) deter- mining historical water-supply well scheduling and operations using TechWellOp, (4) three-dimensional contaminant fate and transport modeling for VOCs dissolved in groundwater using MT3DMS-5.3, (5) estimating the volume of light nonaqueous phase liquid (LNAPL) released to the subsurface at the Hadnot Point Industrial Area using TechNAPLVol, (6) analysis of LNAPL and dissolved phase fate and transport using TechFlowMP, (7) reconstruction of water-supply well concentrations at the Hadnot Point landfill using the linear control theory model (LCM) TechControl, (8) computation of flow-weighted average concentrations of VOCs assigned to finished water delivered by the HPWTP using a materials mass balance (simple mixing) model, (9) extended period simulation of hydraulics and water quality of the Holcomb Boulevard water-distribution system using EPANET 2, (10) sensitivity analysis of hydraulic, fate and transport, and numerical-model parameter values, (11) uncertainty analysis by coupling Kalman filtering with Monte Carlo simulation within the LCM methodology, and (12) probabilistic analysis of intermittent connections (1972–1985) of the Hadnot Point and Holcomb Boulevard water-distribution systems using the TechMarkov-Chain model. The end result of the historical reconstruction process was the estimation of monthly mean concentrations of selected VOCs in finished water distributed to housing areas served by the HPWTP and HBWTP. Historical reconstruction results summarized herein provide considerable evidence that concentrations of several contaminants of interest in finished water delivered by the HPWTP substantially exceeded current maximum contaminant levels (MCLs) during all or much of the epidemiological study period of 1968–1985. Reconstructed concentrations of TCE exceeded the current MCL of 5 micrograms per liter (μg/L) prior to and during the entire epidemiological study period and reached a maximum reconstructed concentration of 783 μg/L during November 1983. The most likely date that TCE first exceeded its current MCL is during August 1953; however, this exceedance could have been as early as November 1948. Corresponding finished-water concentrations of PCE exceeded the current MCL of 5 μg/L during most of the period 1975–1985 and also reached a maximum concentration of 39 μg/L during November 1983. Similar results for 1,2-tDCE and VC were also noted during the period 1975–1985. The maximum reconstructed concentrations of 1,2-tDCE and VC were 435 and 67 μg/L, respectively, and also occurred during November 1983. The respective current MCLs for these contaminants are 100 and 2.0 μg/L. Substantial volumes of liquid hydrocarbon fuels were lost due to leakage to the subsurface within the Hadnot Point Industrial Area. This area contained as many as 10 active water-supply wells. Despite the large volumes lost, finished- water concentrations of benzene only slightly exceeded the current MCL of 5 μg/L during the period 1980–1985. The maximum reconstructed concentration of 12 μg/L of benzene occurred during April 1984. Within the HBWTP service area, only TCE routinely exceeded its current MCL during intermittent periods (1972–1985). The TCE resulted from transfers of finished water from the Hadnot Point water-distribution system to the Holcomb Boulevard water-distribution system. The maximum reconstructed TCE concentration of 51 μg/L occurred during June 1978 at the Berkeley Manor housing area. During the 8-day period of January 28 through February 4, 1985, the HBWTP was out of service, and the HPWTP continuously supplied finished water to the Holcomb Boulevard housing area. During this period, the maximum reconstructed TCE concentration at the HPWTP was 324 μg/L, which resulted in a maximum reconstructed monthly mean concentration of 66 μg/L within the Paradise Point housing area.

North Carolina↗
USGS2024

Comparative toxicity of emulsifiable concentrate and suspension concentrate formulations of 2′,5-dichloro-4′-nitrosalicylanilide ethanolamine salt

The 2-aminoethanol salt of niclosamide (2′,5-dichloro-4′-nitrosalicylanilide) is a pesticide known as Bayluscide that is used in conjunction with TFM (4-nitro-3-[trifluoromethyl]phenol), also known as 3-trifluoromethyl-4-nitrophenol) to treat tributaries to the Great Lakes infested with invasive parasitic Petromyzon marinus (sea lamprey). Adding 0.5 to 2 percent Bayluscide with TFM can substantially reduce the amount of TFM required to achieve effective control. Currently, an emulsifiable concentrate (EC) formulation of Bayluscide is used in combination with TFM during some stream treatments completed by the Great Lakes Fishery Commission’s binational sea lamprey control program. The Bayluscide EC formulation is highly effective; however, it degrades application tubing, adheres to application equipment, and raises concerns for worker safety because of the solvent in the formulation, N-methyl-2-pyrrolidone. We collaborated with a pesticide formulation company to develop a Bayluscide 20-percent suspension concentrate (SC) formulation as a potential replacement for the Bayluscide 20-percent EC formulation. The 20-percent SC formulation was specifically developed using inert ingredients approved for use by the U.S. Environmental Protection Agency and the Health Canada Pest Management Regulatory Agency. Although approved for use, the inclusion of a small quantity of an antimicrobial in the formulation warranted evaluating the toxicological profile to sea lamprey and select nontarget fish species. We evaluated and compared the toxicity of the 20-percent SC formulation to the 20-percent EC formulation using continuous-flow diluter systems and larval sea lamprey and select cold-, cool-, and warm-water fish as test animals. Our results demonstrate comparable toxicological profiles between the two formulations with the 20-percent SC formulation being slightly less toxic to the nontarget species evaluated.

Open-File Report↗
USGS2019

Nonlinearities in transmission dynamics and efficient management of vector-borne pathogens

Integrated Pest Management (IPM) is an approach to minimizing economic and environmental harm caused by pests, and Integrated Vector Management (IVM) uses similar methods to minimize pathogen transmission by vectors. The risk of acquiring a vector-borne infection is often quantified using the density of infected vectors. The relationship between vector numbers and risk of human infection is more or less linear when both vector numbers and pathogen prevalence in vectors are low, but the relationship is nonlinear when vector density and/or infection prevalence are high. Therefore, the density of infected vectors often does not accurately predict risk of human exposure to pathogens, and traditional estimates of % Control often overestimate the level of protection from infection resulting from management programs. We suggest a modified estimator, % Protection, which more accurately quantifies protection against human infection resulting from a management intervention. Cost-effectiveness of a management program is critical to protection of both public health and the environment, because the more efficiently available resources and funding are used, the fewer people get sick, and well-targeted efficient management programs minimize the need for poorly-targeted, expensive environmental interventions (e.g., broadscale pesticide applications) that tend to damage nontarget organisms and natural systems. Design of an efficient, cost-effective IVM program requires knowledge of the cost-effectiveness functions (the effectiveness of control methods at lowering vector bites and/or infection prevalence with different levels of application) of the various control methods to be applied. Alternative programs can be designed that optimize % Protection by integrating different control methods at different levels of investment, and environmental effects of these alternatives can be compared, allowing environmental considerations to be included explicitly in the decision process. IPM, IVM, and Adaptive Management share the characteristic that management decisions must be made with incomplete knowledge of the functioning of natural systems or the efficacies of interventions. IVM surveillance programs that assess the effects of individual control methods and of combinations of control methods on the numbers of vector bites and on infection prevalence in vectors, can increase knowledge of pathogen transmission dynamics and provide information to improve program effectiveness in subsequent applications.

Ecological Applications↗