Civil and Environmental Engineering Copyright (c) 2013 Syracuse University All rights reserved. http://surface.syr.edu/cie Recent documents in Civil and Environmental Engineering en-us Fri, 24 May 2013 11:30:37 PDT 3600 Long-Term Integrated Studies Show Complex and Surprising Effects of Climate Change in the Northern Hardwood Forest http://surface.syr.edu/cie/15 http://surface.syr.edu/cie/15 Fri, 08 Mar 2013 08:20:23 PST Evaluations of the local effects of global change are often confounded by the interactions of natural and anthropogenic factors that overshadow the effects of climate changes on ecosystems. Long-term watershed and natural elevation gradient studies at the Hubbard Brook Experimental Forest and in the surrounding region show surprising results demonstrating the effects of climate change on hydrologic variables (e.g., evapotranspiration, streamflow, soil moisture); the importance of changes in phenology on water, carbon, and nitrogen fluxes during critical seasonal transition periods; winter climate change effects on plant and animal community composition and ecosystem services; and the effects of anthropogenic disturbances and land-use history on plant community composition. These studies highlight the value of long-term integrated research for assessments of the subtle effects of changing climate on complex ecosystems.

]]> Peter M. Groffman et al. Mercury Concentrations in Tropical Resident and Migrant Songbirds on Hispaniola http://surface.syr.edu/cie/14 http://surface.syr.edu/cie/14 Fri, 08 Mar 2013 08:20:22 PST Despite growing concerns over mercury (Hg) exposure to humans and wildlife on a global scale, little is known about Hg bioaccumulation in the New World tropics. From 2005 to 2011, we monitored Hg concentrations in blood of nine avian species occupying a geographic range of tropical wet broadleaf sites on the island of Hispaniola, including eight passerines (two Nearctic- Neotropical migrant and six resident species) and one top order predatory accipiter. Invertivorous songbirds were further differentiated by foraging guild, with six species of groundforagers and two species of foliage-gleaners. Blood Hg concentrations were orders of magnitude higher in birds sampled in central and southern cloud forest sites (1000 – 1800 m elevation) than in northern and northeastern rainforest sites (50 – 500 m elevation), with migratory and resident species both showing 2 – 20 X greater blood Hg concentrations in cloud forests than in rainforests. Within cloud forest sites, ground-foraging species had higher Hg concentrations than foliage-gleaning species. Top order predatory sharp-shinned hawks (Accipiter striatus) had the highest blood Hg concentrations among all species, suggesting that Hg biomagnification is occurring in terrestrial forests of Hispaniola. Two migrant songbird species overwintering on the island had higher blood Hg concentrations than have been recorded on their North American breeding grounds. Future studies should seek to elucidate sources of variation in atmospheric Hg deposition on Hispaniola and to quantify the dynamics of Hg cycling in tropical forest ecosystems, which may differ in important ways from patterns documented in temperate forest ecosystems.

]]> Jason M. Townsend et al. Marine Mercury Fate: From Sources to Seafood Consumers http://surface.syr.edu/cie/13 http://surface.syr.edu/cie/13 Fri, 08 Mar 2013 08:20:21 PST Celia Y. Chen et al. Nutrient Supply and Mercury Dynamics in Marine Ecosystems: A Conceptual Model http://surface.syr.edu/cie/12 http://surface.syr.edu/cie/12 Fri, 08 Mar 2013 08:20:19 PST There is increasing interest and concern over the impacts of mercury (Hg) inputs to marine 32 ecosystems. One of the challenges in assessing these effects is that the cycling and trophic 33 transfer of Hg are strongly linked to other contaminants and disturbances. In addition to Hg, a 34 major problem facing coastal waters is the impacts of elevated nutrient, particularly nitrogen 35 (N), inputs. Increases in nutrient loading alter coastal ecosystems in ways that should change 36 the transport, transformations and fate of Hg, including increases in fixation of organic carbon 37 and deposition to sediments, decreases in the redox status of sediments and changes in fish 38 habitat. In this paper we present a conceptual model which suggests that increases in loading 39 of reactive N to marine ecosystems might alter Hg dynamics, decreasing bioavailabilty and 40 trophic transfer. This conceptual model is most applicable to coastal waters, but may also be 41 relevant to the pelagic ocean. We present information from case studies that both support and 42 challenge this conceptual model, including marine observations across a nutrient gradient; 43 results of a nutrient‐trophic transfer Hg model for pelagic and coastal ecosystems; observations 44 of Hg species, and nutrients from coastal sediments in the northeastern U.S.; and an analysis of 45 fish Hg concentrations in estuaries under different nutrient loadings. These case studies suggest 46 that changes in nutrient loading can impact Hg dynamics in coastal and open ocean ecosystems. 47 Unfortunately none of the case studies is comprehensive; each only addresses a portion of the 48 conceptual model and has limitations. Nevertheless, our conceptual model has important 49 management implications. Many estuaries near developed areas are impaired due to elevated 50 nutrient inputs. Widespread efforts are underway to control N loading and restore coastal 51 ecosystem function. An unintended consequence of nutrient control measures could be to 3 exacerbate 52 problems associated with Hg contamination. Additional focused research and 53 monitoring are needed to critically examine the link between nutrient supply and Hg 54 contamination of marine waters.

]]> Charles T. Driscoll et al. Shift Towards P Limitation with N Deposition? http://surface.syr.edu/cie/11 http://surface.syr.edu/cie/11 Mon, 14 Jan 2013 11:43:11 PST Atmospheric nitrogen (N) deposition is altering biogeochemical cycling in forests and interconnected lakes of the northeastern US, and may shift nutrient limitation from N toward other essential elements, such as phosphorus (P). Whether this shift is occurring relative to N deposition gradients across the northeastern US has not been investigated. We used datasets for the northeastern US and the Adirondack sub-region to evaluate whether P limitation is increasing where N deposition is high at two geographic scales, based on N:P mass ratios. Using a model- selection approach, we determined that foliar N for dominant tree species and lake dissolved inorganic N (DIN) increased coincident with increasing N deposition, independent of relationships between foliar N or lake DIN and precipitation or temperature. Foliar P also increased with N deposition across the northeastern US for seven of eight deciduous species, but changed less across the Adirondacks. Foliar N:P therefore declined at the highest levels of N deposition for most deciduous species across the region (remaining nearly constant for most conifers and increasing only for black cherry and hemlock), but increased across all species in the Adirondacks. Ratios between DIN and total P (DIN:TP) in lakes were unrelated to N deposition regionally but increased across the Adirondacks. Thus, nutrient limitation patterns shifted from N toward P for dominant trees, and further toward P for predominantly P-limited lakes, at the sub-regional but not regional scale. For the northeastern US overall, accumulated N deposition may be insufficient to drive nutrient limitation from N toward P; alternatively, elements other than P (e.g., calcium, magnesium) may become limiting as N accumulates. The consistent Adirondack foliar and lake response could provide early indication of shifts toward P limitation within the northeastern US, and together with regional patterns, suggests that foliar chemistry could be a predictor of lake chemistry in the context of N deposition across the region.

]]> K. F. Crowley et al. Modeling potential hydrochemical responses to climate change and increasing CO2 at the Hubbard Brook Experimental Forest using a dynamic biogeochemical model (PnET-BGC) http://surface.syr.edu/cie/10 http://surface.syr.edu/cie/10 Wed, 07 Nov 2012 09:18:38 PST Dynamic hydrochemical models are useful tools for understanding and predicting the interactive effects of climate change, atmospheric CO2, and atmospheric deposition on the hydrology and water quality of forested watersheds. We used the biogeochemical model, PnET-BGC, to evaluate the effects of potential future changes in temperature, precipitation, solar radiation, and atmospheric CO2 on pools, concentrations, and fluxes of major elements at the Hubbard Brook Experimental Forest in New Hampshire, United States. Future climate projections used to run PnET-BGC were generated specifically for the Hubbard Brook Experimental Forest with a statistical technique that downscales climate output (e.g., air temperature, precipitation, solar radiation) from atmosphere-ocean general circulation models (AOGCMs) to a finer temporal and spatial resolution. These climate projections indicate that over the twenty-first century, average air temperature will increase at the site by 1.7 degrees C to 6.5 degrees C with simultaneous increases in annual average precipitation ranging from 4 to 32 cm above the long-term mean (1970–2000). PnET-BGC simulations under future climate change show a shift in hydrology characterized by later snowpack development, earlier spring discharge (snowmelt), greater evapotranspiration, and a slight increase in annual water yield (associated with CO2 effects on vegetation). Model results indicate that under elevated temperature, net soil nitrogen mineralization and nitrification markedly increase, resulting in acidification of soil and stream water, thereby altering the quality of water draining from forested watersheds. Invoking a CO2 fertilization effect on vegetation under climate change substantially mitigates watershed nitrogen loss, highlighting the need for a more thorough understanding of CO2 effects on forest vegetation.

]]> Afshin Pourmokhtaria et al. Nutrient Supply and Mercury Dynamics in Marine Ecosystems: A Conceptual Model http://surface.syr.edu/cie/9 http://surface.syr.edu/cie/9 Thu, 04 Oct 2012 12:35:13 PDT There is increasing interest and concern over the impacts of mercury (Hg) inputs to marine ecosystems. One of the challenges in assessing these effects is that the cycling and trophic transfer of Hg are strongly linked to other contaminants and disturbances. In addition to Hg, a major problem facing coastal waters is the impacts of elevated nutrient, particularly nitrogen (N), inputs. Increases in nutrient loading alter coastal ecosystems in ways that should change the transport, transformations and fate of Hg, including increases in fixation of organic carbon and deposition to sediments, decreases in the redox status of sediments and changes in fish habitat. In this paper we present a conceptual model which suggests that increases in loading of reactive N to marine ecosystems might alter Hg dynamics, decreasing bioavailabilty and trophic transfer. This conceptual model is most applicable to coastal waters, but may also be relevant to the pelagic ocean. We present information from case studies that both support and challenge this conceptual model, including marine observations across a nutrient gradient; results of a nutrient‐trophic transfer Hg model for pelagic and coastal ecosystems; observations of Hg species, and nutrients from coastal sediments in the northeastern U.S.; and an analysis of fish Hg concentrations in estuaries under different nutrient loadings. These case studies suggest that changes in nutrient loading can impact Hg dynamics in coastal and open ocean ecosystems. Unfortunately none of the case studies is comprehensive; each only addresses a portion of the conceptual model and has limitations. Nevertheless, our conceptual model has important management implications. Many estuaries near developed areas are impaired due to elevated nutrient inputs. Widespread efforts are underway to control N loading and restore coastal ecosystem function. An unintended consequence of nutrient control measures could be to exacerbate problems associated with Hg contamination. Additional focused research and monitoring are needed to critically examine the link between nutrient supply and Hg contamination of marine waters.

]]> Charles T. Driscoll et al. Effects of Nitrogen Deposition and Empirical Nitrogen Critical Loads for Ecoregions of the United States http://surface.syr.edu/cie/8 http://surface.syr.edu/cie/8 Tue, 02 Oct 2012 08:50:18 PDT Human activity in the last century has led to a significant increase in nitrogen (N) emissions and atmospheric deposition. This N deposition has reached a level that has caused or is likely to cause alterations to the structure and function of many ecosystems across the United States. One approach for quantifying the deposition of pollution that would be harmful to ecosystems is the determination of critical loads. A critical load is defined as the input of a pollutant below which no detrimental ecological effects occur over the long-term according to present knowledge.

The objectives of this project were to synthesize current research relating atmospheric N deposition to effects on terrestrial and freshwater ecosystems in the United States, and to estimate associated empirical N critical loads. The receptors considered included freshwater diatoms, mycorrhizal fungi, lichens, bryophytes, herbaceous plants, shrubs, and trees. Ecosystem impacts included: (1) biogeochemical responses and (2) individual species, population, and community responses. Biogeochemical responses included increased N mineralization and nitrification (and N availability for plant and microbial uptake), increased gaseous N losses (ammonia volatilization, nitric and nitrous oxide from nitrification and denitrification), and increased N leaching. Individual species, population, and community responses included increased tissue N, physiological and nutrient imbalances, increased growth, altered root:shoot ratios, increased susceptibility to secondary stresses, altered fire regime, shifts in competitive interactions and community composition, changes in species richness and other measures of biodiversity, and increases in invasive species.

The range of critical loads for nutrient N reported for U.S. ecoregions, inland surface waters, and

freshwater wetlands is 1-39 kg N ha-1 y-1, spanning the range of N deposition observed over most

of the country. The empirical critical loads for N tend to increase in the following sequence for different life forms: diatoms, lichens and bryophytes, mycorrhizal fungi, herbaceous plants and shrubs, trees.

The critical load approach is an ecosystem assessment tool with great potential to simplify complex scientific information and communicate effectively with the policy community and the public. This synthesis represents the first comprehensive assessment of empirical critical loads of N for major ecoregions across the United States.

]]> Linda H. Pardo et al. Science and society: The Role of Long-term Studies in Environmental Stewardship http://surface.syr.edu/cie/7 http://surface.syr.edu/cie/7 Tue, 03 Jul 2012 08:08:15 PDT Long-term research should play a crucial role in addressing grand challenges in environmental stewardship. We examine the efforts of five Long Term Ecological Research Network sites to enhance policy, management, and conservation decisions for forest ecosystems. In these case studies, we explore the approaches used to inform policy on atmospheric deposition, public land management, land conservation, and urban forestry, including decisionmaker engagement and integration of local knowledge, application of models to analyze the potential consequences of policy and management decisions, and adaptive management to generate new knowledge and incorporate it into decisionmaking. Efforts to enhance the role of long-term research in informing major environmental challenges would benefit from the development of metrics to evaluate impact; stronger partnerships among research sites, professional societies, decisionmakers, and journalists; and greater investment in efforts to develop, test, and expand practice-based experiments at the interface of science and society.

]]> Charles T. Driscoll et al. Spatial and Temporal Patterns of Mercury Accumulation in Lacustrine Sediments across the Laurentian Great Lakes Region http://surface.syr.edu/cie/6 http://surface.syr.edu/cie/6 Tue, 01 May 2012 10:27:32 PDT Data from 104 sediment cores from the Great Lakes and “inland lakes” in the region were compiled to assess historical and recent changes in mercury (Hg) deposition. The lower Great Lakes showed sharp increases in Hg loading c. 1850-1950 from point-source water dischargers, with marked decreases during the past half century associated with effluent controls and decreases in the industrial use of Hg. In contrast, Lake Superior and inland lakes exhibited a pattern of Hg loading consistent with an atmospheric source - gradual increases followed by recent (post-1980) decreases. Variation in sedimentary Hg flux among inland lakes was primarily attributed to the ratio of watershed area: lake area, and secondarily to a lake’s proximity to emission sources. A consistent region-wide decrease (~20%) of sediment Hg flux suggests that controls on local and regional atmospheric Hg emissions have been effective in decreasing the supply of Hg to Lake Superior and inland lakes.

]]> Paul E. Drevnick et al. Mercury Contamination in Forest and Freshwater Ecosystems in the Northeastern United States http://surface.syr.edu/cie/5 http://surface.syr.edu/cie/5 Tue, 27 Mar 2012 10:40:04 PDT Eastern North America receives elevated atmospheric mercury deposition from a combination of local, regional, and global sources. Anthropogenic emissions originate largely from electric utilities, incinerators, and industrial processes. The mercury species in these emissions have variable atmospheric residence times, which influence their atmospheric transport and deposition patterns. Forested regions with a prevalence of wetlands and of unproductive surface waters promote high concentrations of mercury in freshwater biota and thus are particularly sensitive to mercury deposition. Through fish consumption, humans and wildlife are exposed to methylmercury, which markedly bioaccumulates up the freshwater food chain. Average mercury concentrations in yellow perch fillets exceed the Environmental Protection Agency’s human health criterion across the region, and mercury concentrations are high enough in piscivorous wildlife to cause adverse behavioral, physiological, and reproductive effects. Initiatives are under way to decrease mercury emissions from electric utilities in the United States by roughly 70%.

]]> Charles T. Driscoll et al. A Synthesis of Rates and Controls on Elemental Mercury Evasion in the Great Lakes Basin http://surface.syr.edu/cie/4 http://surface.syr.edu/cie/4 Tue, 27 Mar 2012 10:39:58 PDT Rates of surface-air elemental mercury (Hgo) fluxes in the literature were synthesized for the Great Lakes Basin (GLB). For the majority of surfaces, fluxes were net positive (evasion). Digital land-cover data were combined with representative evasion rates and used to estimate annual Hgo evasion for the GLB (7.7 Mg/yr). This value is less than our estimate of total Hg deposition to the area (15.9 Mg/yr), suggesting the GLB is a net sink for atmospheric Hg. The greatest contributors to annual evasion for the basin are agricultural (~55%) and forest (~25%) land cover types, and the open water of the Great Lakes (~15%). Areal evasion rates were similar across most land cover types (range: 7.0 to 21.0 μg/m2-yr), with higher rates associated with urban (12.6 μg/m2-yr) and agricultural (21.0 μg/m2-yr) lands. Uncertainty in these estimates could be partially remedied through a unified methodological approach to estimating Hgo fluxes.

]]> Joseph S. Denkenberger et al. Empirical Critical Loads of Atmospheric Nitrogen Deposition for Nutrient Enrichment and Acidification of Sensitive US Lakes http://surface.syr.edu/cie/3 http://surface.syr.edu/cie/3 Sat, 03 Mar 2012 09:22:32 PST Jill S. Baron et al. Integrating Science and Policy: A Case Study of the Hubbard Brook Research Foundation Science Links Program http://surface.syr.edu/cie/2 http://surface.syr.edu/cie/2 Sat, 03 Mar 2012 08:58:31 PST Scientists, related professionals, and the public have for decades called for greater interaction among scientists, policymakers, and the media to address contemporary environmental challenges. Practical examples of effective “real-world” programs designed to catalyze interactions and provide relevant science are few. Existing successful models can be used, however, to develop and expand the work of integrating, synthesizing, and communicating ecosystem science for environmental policy and natural-resource management. We provide an overview of the structure and strategies used in the Hubbard Brook Research Foundation Science Links program, now in its thirteenth year as a successful boundary-spanning organization. We detail project activities and results and share lessons and challenges for the further advancement of Science Links and other efforts to bridge the science–policy divide. Furthermore, we suggest greater emphasis in boundary-spanning programs as a part of publicly funded research initiatives and as legitimate scholarly endeavors that support the scaled coproduction of knowledge and that harness scientific research to support informed policy and environmental management.

]]> Charles T. Driscoll et al. Accidental Releases of Hazardous Materials and Relevance to Terrorist Threats at Industrial Facilities http://surface.syr.edu/cie/1 http://surface.syr.edu/cie/1 Fri, 02 Dec 2011 11:33:56 PST Hazardous material releases, some with serious consequences, are a common occurrence in the U.S. Of late, the hazards posed by releases caused by terrorist attacks or natural disasters have been of particular concern. Although terrorism directed at hazardous material handling industries within the U.S. has not yet resulted in a significant incident, there is much recent experience with serious accidental releases resulting from natural disasters. Case studies are developed from a number of recent natural disasters and severe weather events that resulted in large releases of hazardous materials. These case studies are used to illustrate parallels between the risks posed by hazardous material releases resulting from terrorism and natural disasters; examples include the presence of a dominant mechanism for physical damage, difficult-to-control and unforeseen scenarios of releases, limited specific regulation of the risks, and a complex and difficult response environment. Hence, lessons learned from previous experience with releases during natural disasters can be used to increase the resilience of industrial facilities and to improve the planning for hazardous material response in the face of terror threats. Routes to improve hazardous material industry preparedness for terror attack and natural disasters include physical hardening of facilities and equipment, utilization of passive safety devices, greater consideration of facility layout and siting, application of inherently safer design principles, and additional legislation at local, state or federal levels.

]]> Laura J. Steinberg et al.