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Computer simulation models have been used to support decision-making at contaminated sediment sites for decades. Nonetheless, their reliability in remedial decision-making has been questioned, and there is a need for retrospective studies of the accuracy of model predictions, that is, post-audits. The Neal's Landfill site near Bloomington, Indiana, provides an example of the successful use of a mathematical simulation model in the selection of a remedy for a site that includes streams with polychlorinated biphenyl (PCB)-affected sediment, water, and fish. A chemical fate and transport and bioaccumulation computer simulation model was developed to compare the effectiveness of alternative remediation plans in reducing fish total PCB concentrations. A post-audit of the model, using several years of data collected after remediation, demonstrates that the model successfully predicted declines in surface water and fish tissue PCB concentrations over a decade, including those associated with longer term natural recovery processes as well as the response to remedial actions. The model predicted, and the post-audit bore out, that risk-based goals would be met using an alternative less extensive than others under consideration. An uncertainty analysis, based on bounding model calculations, provided important support for decision-making, as did the inclusion of a statistical Remedy Confirmation Clause in the Consent Decree for the site. This study demonstrates the utility of a computer simulation model to guide remedial decision-making at a contaminated sediment site. Integr Environ Assess Manag 2022;18:1233-1245. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental ToxicologyChemistry (SETAC).

The rapid loss of eastern hemlock (Tsuga canadensis) in the southern Appalachian Mountains due to hemlock woolly adelgid (Adelges tsugae, HWA) infestation has resulted in substantial changes to ecosystem structure and function. Several restoration strategies have been proposed, including silvicultural treatments that increase incident light in forest understories. We conducted a four-year manipulative field experiment on surviving mid-story hemlock trees to investigate the effects of release from light limitation on HWA infestation and physiological parameters, expecting that higher light levels would improve tree carbon balance. Mixed hardwood forest sites were either previously uninfested with HWA (UN), infested with HWA (I), or infested with HWA and had a history of predatory beetle releases for biological control (I+P). At each site, we identified ten eastern hemlock trees in the mid-story and cut ~15 m radius canopy gaps around half of them while leaving the canopy intact over the other half. We compared short- and long-term indices of carbon gain and stress: leaf net photosynthesis (Anet); leaf fluorescence (Fv/Fm); leaf total non-structural carbohydrate concentration ([TNC]); new shoot growth; HWA density; and basal area growth. We found that trees experienced greater leaf-level stress in gaps and when HWA was actively feeding. Despite being more stressed, trees in gaps fixed 2x more carbon than those in reference conditions. High Anet in the spring translated into high leaf [TNC] in the spring, coinciding with when HWA was actively feeding. Although infested and uninfested trees had similar leaf [TNC] maxima, infestation prevented trees from allocating this carbon to shoot and basal area growth; this was particularly true for reference trees. Greater shoot growth in gap trees translated to greater annual basal area growth—by the end of the study, trees in gaps were growing 9x more than trees in reference conditions, and this was generally regardless of infestation status. In terms of growth and carbon balance, eastern hemlock consistently benefited from the increased light and soil moisture found in gaps; there was inconsistent and rather weak evidence that predator beetles conferred an additional advantage. Our results indicate that silvicultural treatments may improve long-term health and survival of infested trees and that integration of such treatments with existing strategies is worthy of continued exploration.

Summary This study investigated the use of emergence traps to assess densities of Laricobius nigrinus Fender (Coleoptera: Derodontidae), a predator of hemlock woolly adelgid (Hemiptera: Adelgidae), in an area of release and establishment. Results indicate that traps effectively collect emerging adults and allow systematic population estimates of L. nigrinus. The incorporation of this method in future monitoring efforts could enable population estimates across the release range of L. nigrinus, thereby enhancing the evaluation of establishment and long-term persistence of this predator.

To reduce populations of hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae),500,000 Sasajiscymnus tsugae (Sasaji and McClure) (Coleoptera: Coccinellidae) have been released in the Great Smoky Mountains National Park since 2002. To determine factors affecting establishment and recovery of these predatory beetles, 65 single release sites were sampled using beat sheets from 2008 to 2012. Several abiotic and biotic factors were evaluated for their association with establishment and recovery of S. tsugae. Information on predatory beetle releases (location, year of release, number released, and season of release), topographic features (elevation, slope, Beers transformed aspect, and topographic relative moisture index), and temperature data (minimum and maximum temperatures 1 d after release and average minimum and maximum temperatures 7 d after release) were obtained from Great Smoky Mountains National Park personnel. These factors were evaluated using stepwise logistic regression and Pearson correlation. S. tsugae was recovered from 13 sites 2 to 10 yr after release, and the greatest number was recovered from 2002 release sites. Regression indicated establishment and recovery was negatively associated with year of release and positively associated with the average maximum temperature 7 d after release and elevation (generally, recovery increased as temperatures increased). Several significant correlations were found between presence and number of S. tsugae and year of release, season of release, and temperature variables. These results indicate that releases of S. tsugae should be made in warmer (≍10-25°C) temperatures and monitored for at least 5 yr after releases to enhance establishment and recovery efforts.

From 2010 through 2013, adult emergence and seasonality of Laricobius nigrinus Fender, an introduced predatory species native to western North America, as well as hybridization with the native species Laricobius rubidus (LeConte), were evaluated using emergence traps and beat-sheet sampling in areas of previous release against hemlock woolly adelgid, Adelges tsugae Annand. The shortest emergence period of adult L. nigrinus was 7 wk beginning 22 October 2010, and the longest emergence was 15 wk beginning 17 October 2012. Native L. rubidus also were collected from emergence traps placed on the ground surface and beat-sheet samples all 3 yr, with emergence of L. rubidus initiating later than L. nigrinus each season. Seasonality of both Laricobius species was similar across a 44-mo study period. Adult L. nigrinus were present from October through April, and larvae of Laricobius spp. were collected from February to May. The average number of L. nigrinus from emergence traps was significantly greater than the average number of beetles collected from beat-sheet samples in 2010, while the converse was observed during 2012. Hybridization between L. nigrinus and L. rubidus was documented from 10.75% of specimens collected during 2010 and 2011, indicating periodic interbreeding between the introduced and native species. These findings suggest emergence trapping may be a useful method to assess establishment, population densities, and seasonality of Laricobius species in areas of release to enhance their use in management of A. tsuage.

The coexistence of two introduced predatory species, Laricobius nigrinus Fender and Sasajiscymnus tsugae (Sasaji and McClure), and a native predator, L. rubidus LeConte, on eastern hemlock was documented for the first time. Details of their coexistence and implications to management of hemlock woolly adelgid, Adelges tsugae Annand, are discussed.

Eastern hemlock in the Great Smoky Mountains National Park is currently threatened by the hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae). As part of a management plan against this invasive insect pest, about 350,000 adults of the predatory beetle Sasajiscymnus tsugae (Sasaji and McClure) (Coleoptera: Coccinellidae) were released at ca. 150 sites in the Park from 2002 to 2007. Of these adult release sites, 33 were sampled in 2008 and 2009 using beat-sheet sampling for 4 man-hours. Sasajiscymnus tsugae adults (n=78) and/or larvae (n=145) were recovered from seven sites (21.2% of the release sites sampled). Recovery of S. tsugae was significantly associated with older release sites, with the most beetles recovered from 2002 release sites. These results indicate that S. tsugae may require more time (i.e., 5–7 years) than anticipated for population densities to reach readily detectable levels in some areas.

Glaser, D., J.R. Rhea, D.R. Opdyke, K.T. Russell, C.K. Ziegler, W. Ku, L. Zheng and J.J. Mastriano. 2009. Model of zebra mussel growth and water quality impacts in the Seneca River, New York. Lake Reserv. Manage. 25:49–72. A dynamic water quality model was developed to support management decision-making for the Seneca River, New York. The model incorporated two-dimensional hydrodynamics to simulate stratification observed within the system, a carbon-based zebra mussel growth model to account for the impact of this invasive species on water quality within the system, and a mechanistic representation of sediment diagenesis to account for zebra mussel-induced changes in carbon cycling. The Seneca River is on New York State's 303(d) list of impaired water bodies for nonattainment of dissolved oxygen criteria and is being considered as the potential receiving water for diverted effluent from an 85 million gallon per day (MGD) wastewater treatment plant (WWTP) serving the City of Syracuse, New York. Th...

A mechanistic model of PCB fate, transport, and bioac cumulation in the Upper Hudson River was developed to provide a quantitative tool to assess the effectiveness of natural recovery and active remediation in reducing PCB levels in water, sediment, and biota. The fate and transport modeling, which is the subject of this paper, builds on previous approaches by using a mechanistic sediment-transport model that describes erosion and deposition with sufficient accuracy to remove the requirement to adjust sediment transport as part of the contaminant calibration process. An additional significant aspect of the model is the calibration and validation for both the short time scale of erosion events and the decade-long time scale associated with trends in sediment contamination.The model demonstrates differences between PCB fate in cohesive and noncohesive sediments that are important to efforts to reduce perceived human health and ecological risks. Burial due to the deposition of solids with lower PCB concentra...

The water quality of Onondaga Lake, NY has been compromised by a 100-year history of municipal and industrial pollution. A state-of-the-science water quality model was developed for the system to facilitate contemporary water quality management which includes: 1) development of total phosphorus and ammonia TMDLs and 2) assessing the feasibility of diverting a large point source discharge out of the Lake and into an adjacent river system. The OLWQM consists of a number of submodels representing the major hydrodynamic, water column nutrient cycling, and sediment processes controlling water quality in the lake. The water column submodel describes nitrification, organic matter decomposition, algal photosynthesis, respiration, and nutrient uptake, and zooplankton and zebra mussel grazing and respiration. The sediment flux submodel simulates the conversion of particulate organic material settling from the water column to dissolved nutrients and the concurrent consumption of oxidized compounds from the overlying water column. The model was calibrated over the period from 1994 to 2003 and successfully simulated the major water quality dynamics observed within the system. Additionally, the model simulated the gross patterns in chlorophyll-a in the epilimnion as well as phosphorus retention within the lake sediments. Finally, the model was able to simulate compliance-based measures of important water quality standards and guidance values developed for the lake. The next step of model development includes linkage of the Lake model with a model of the adjacent river system and validation of the linked models.

The U.S. Department of Energy (DOE) is defining decontamination and decommissidning (D&D) obligations at its sites (1). Current D&D activities are generally labor in-te sive, use chemical reagents that are difficult to treat, and may expose workers to radioactive and hazardous chemicals (1). Therefore, new technologies are desired that minimize waste, allow much of the decommissioned materials to be reused rather than disposed of as waste, and produce wastes that will meet disposal criteria (1).

The proton binding characteristics of humic acids extracted from the sediments of Cranberry Pond, an acidic water body located in the Adirondack Mountain region of New York State, were explored by the application of a multiligand distribution model. The model characterizes a class of proton binding sites by mean logK values and the standard deviations of logK values about the mean. Mean logK values and their relative abundances were determined directly from experimental titration data. The model accurately predicts the binding of protons by the humic acids for pH values in the range 3.5 to 10.0.

A mathematical model (ALaRM) for predicting the reacidification profile of calcium carbonate treated lakes has been calibrated and confirmed using data from two Lake Acidification Mitigation Project (LAMP) lakes. This manuscript focused on the use of ALaRM to evaluate the relative impact of bottom sediment processes on the reacidification rate of the LAMP lakes. Prior to liming the lakes exhibited annual average sediment-to-water ANC fluxes of 194 and 240 meq/m2-yr for Woods Lake and Cranberry Pond, respectively. Following liming there was a period of net water-to-sediment ANC flux due to a reversal of the gradients of ANC-determining chemical species, indicating a buffering effect of bottom sediments on water column acid-base chemistry. A sensitivity analysis indicated that calcite treatment of sediments as well as the water column could mitigate the sediment reacidification-accelerating effect.

Preparations for neutralization of two acidic lakes in the southwest Adirondacks included determination of base neutralization capacity for sediments as well as the water column. For sediments this involved assessing vertical and horizontal gradients in sediment properties related to sediment-bound acidity. The analyses showed significant variance vertically (depth within the sediment profile) and horizontally (due mainly to depth of overlying water) in both lakes. Base requirements, equivalent to the acidity present 3in 2 cm of sediments ranged between 0.011 and 0.022 kg CaCO3 m−3 for the two lakes. Preliminary observations indicate pH3 values and Ca content increased in the surficial sediments of both lakes after treatment.

A modeling approach guided whole-lake neutralization treatments of two acidic Adirondack lakes and aided examination of treatment efficiency as measured by initial water column dissolution and calcite delivery to sediments, prediction of posttreatment water chemistry, and assessment of the fate of calcite deposited on sediments. The lake model incorporated both dissolution and sedimentation of calcite in a vertically segmented lake assumed to behave as a closed system. Observed short-term calcite dissolution exceeded predictions (75 versus 45%) because (1) dispersion and thermocline presence slowed calcite particle settling; and, (2) CO2influx altered the chemical environment of the particles. Prior to calcite treatment, the two lakes had sediments with similar base neutralizing capacities (BNC). Quantitatively, minor sediment neutralization resulted from the treatment; however, sediment pH gradients changed from positive to negative downward, and Caτin surficial sediments increased as sediment BNC decreased. During the subsequent 16 mo of reacidification, sediment chemical characteristics partially returned to pretreatment conditions by contributing alkalinity to the overlying water.