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Modelling nutrient mass balance in a temperate meso-tidal estuary: Implications for management

Neto, João Magalhães; Flindt, Mogens René; Marques, João Carlos; Pardal, Miguel Ângelo
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
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Although mitigation programmes have been implemented in huge eutrophied estuarine systems, satisfactory results are not always immediately achieved. External loadings are reduced but the nutrient pools still existing in the sediments (due to decades of external supply) start to deplete only slowly, to reach the lower steady state level related to the new external loading. In the Mondego Estuary, this situation could be seen from the mass balance calculations including different nutrient fractions (dissolved, SPM and bound in vegetation). Different nutrient fractions quantified over the year showed the retention capacity and supplying capacity of these estuarine systems, and also the seasonal dynamics those fractions can present. External loading of nitrogen was largely dominated by DIN, but after its incorporation by benthic primary producers nitrogen export occurred essentially as SPM-N. Phosphorus loading was dominated by SPM-P, but during warmer periods P-efflux increased DIP concentration inside the system and was afterwards exported through the outer boundary. Although nutrients bound in vegetation were not significant to total mass balance, depending on the occurrence of occasional macroalgal blooms, the vegetation fraction can significantly increase its contribution to the overall balance.; http://www.sciencedirect.com/science/article/B6WDV-4PCH4GK-3/1/443da3c46a02fffbce05a7a866d2326d

Significant variations in the productivity of green macroalgae in a mesotidal estuary: Implications to the nutrient loading of the system and the adjacent coastal area

Martins, Irene; Lopes, R. J.; Lillebø, A. I.; Neto, J. M.; Pardal, M. A.; Ferreira, J. G.; Marques, J. C.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
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A spatially dynamic model for the productivity of spores and adults of green macroalgae (Enteromorpha sp.) was developed for a mesotidal estuary (Mondego estuary, Portugal). Many of the algal processes and parameters included in the model were experimentally obtained. Model predictions were compared to a real time series (1993-1997) of macroalgal biomass variation and the two sets show a good agreement (ANOVA, P < 0.001). Results suggest that algal growth is highly sensitive to small changes in depth and exhibits different patterns of variation in different seasons. On a yearly basis, global calculations for the south channel of the estuary (137 ha) suggest that during bloom years, macroalgal biomass may reach about 21,205 ton DW compared to 240 ton DW in regular years. On a seasonal basis, the difference may be even more significant. The consequences of such variations on the nitrogen and phosphorus loading of the system and the adjacent coastal area are discussed.; http://www.sciencedirect.com/science/article/B6V6N-4NC50YV-1/1/08858397fcd2b06c01df2d79411cbf08

Nutrient cycling and plant dynamics in estuaries: A brief review

Flindt, Mogens R.; Pardal, Miguel Ângelo; Lillebø, Ana Isabel; Martins, Irene; Marques, João Carlos
Fonte: Elsevier SAS Publicador: Elsevier SAS
Tipo: Artigo de Revista Científica
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Eutrophication of European estuaries due to massive nutrient loading from urban areas and diffuse runoff from extensively cultivated land areas is analysed. Consequences for the ecology of estuaries, namely changes in plant species composition, which also affects heterotrophic organisms, are approached based on examples showing that the result is often a fundamental structural change of the ecosystem, from a grazing and/or nutrient controlled stable systems to unstable detritus/mineralisation systems, where the turnover of oxygen and nutrients is much more dynamic and oscillations between aerobic and anaerobic states frequently occur. Several relevant aspects are examined, namely the influence of rooted macrophytes on nutrient dynamics, by comparing bare bottom sediments with eelgrass covered sediments, primary production and the development of organic detritus, and hydrodynamics and its relations to the spatial distribution of macrophytes in estuarine systems; http://dx.doi.org/10.1016/S1146-609X(99)00142-3

Management of a shallow temperate estuary to control eutrophication: The effect of hydrodynamics on the system’s nutrient loading

Lillebø, A. I.; Neto, J. M.; Martins, I.; Verdelhos, T.; Leston, S.; Cardoso, P. G.; Ferreira, S. M.; Marques, J. C.; Pardal, M. A.
Fonte: Elsevier Ltd. Publicador: Elsevier Ltd.
Tipo: Artigo de Revista Científica
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The Mondego estuary, a shallow warm-temperate intertidal system located on the west coast of Portugal, has for some decades been under severe ecological stress, mainly caused by eutrophication. Water circulation in this system was, until 1998, mainly dependent on tides and on the freshwater input of a small tributary artificially controlled by a sluice. After 1998, the sluice opening was effectively minimised to reduce the nutrient loading, and the system hydrodynamics improved due to engineering work in the upstream areas. The objective of the present study was to evaluate the effect of the mitigation measures implemented in 1998. Changes to the hydrodynamics of the system were assessed using precipitation and salinity data in relation to the concentrations of dissolved inorganic nutrients, as well as the linkage between dissolved N:P ratios and the biological parameters (phytoplankton chlorophyll a concentrations, green macroalgal biomass and seagrass biomass). Two distinctive periods were compared, over a ten year period: from January 1993 to January 1997 and from January 1999 until January 2003. The effective reduction in the dissolved N:P atomic ratio from 37.7 to 13.2 after 1998 is a result of lowered ammonia, but not the oxidised forms of nitrogen (nitrate plus nitrite)...

Nutrient loading and consumers: Agents of change in open-coast macrophyte assemblages

Nielsen, Karina J.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
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Human activities are significantly altering nutrient regimes and the abundance of consumers in coastal ecosystems. A field experiment in an open-coast, upwelling ecosystem showed that small increases in nutrients increased the biomass and evenness of tide pool macrophytes where consumer abundance and nutrient loading rates were low. Consumers, when abundant, had negative effects on the diversity and biomass of macrophytes. Nutrient loading increases and consumers are less abundant and efficient as wave exposure increases along open coastlines. Experimentally reversing the natural state of nutrient supply and consumer pressure at a wave-protected site to match wave-exposed sites caused the structure of the macrophyte assemblage to converge on that found naturally in wave-exposed pools. The increases in evenness and abundance were driven by increases in structurally complex functional groups. In contrast, increased nutrient loading in semienclosed marine or estuarine ecosystems is typically associated with declines in macrophyte diversity because of increases in structurally simple and opportunistic functional groups. If nutrient concentration of upwelled waters changes with climatic warming or increasing frequency of El Niños...

Nutrient supply and mercury dynamics in marine ecosystems: A conceptual model

Driscoll, Charles T.; Chen, Celia Y.; Hammerschmidt, Chad R.; Mason, Robert P.; Gilmour, Cynthia C.; Sunderland, Elsie M.; Greenfield, Ben K.; Buckman, Kate L.; Lamborg, Carl H.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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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...

Nutrient limitation of phytoplankton in 21 subarctic lakes and ponds in Wapusk National Park, Manitoba

Symons, Celia
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
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We determined the limiting nutrient of phytoplankton in 21 lakes and ponds in Wapusk National Park, Manitoba using nutrient enrichment bioassays to asses the response of natural phytoplankton communities to nitrogen and phosphorus additions. The goal was to determine if these subarctic lakes and ponds were nutrient (N or P) limited, and improve the ability to predict future impacts of increased nutrient loading associated with climate change. We found that 38% of lakes were not limited by nitrogen or phosphorus, 26% were co-limited by N and P, 26% were P-limited and 13% were N-limited. The TN:TP ratios within the lake were compared to the Redfield ratio to test if predictions of the limiting nutrient were accurate; however, these predictions only agreed with 29% of the bioassay results, suggesting that TN:TP ratios do not provide an true measure of nutrient limitation within this region. The N-limited lakes had significantly different phytoplankton community composition; however, other potential predictors of nutrient status – environmental variables and cladoceran abundance - were not similar between lakes of the same nutrient status. Although the limiting nutrient was not predictable, the presence of N and P limitation within Wapusk National Park lakes and ponds suggests that there will be increased phytoplankton productivity in response to increased nutrient loading associated with climate change.; Discovery NSERC...

Review: Nutrient loading of developing seeds

Zhang, W.H.; Zhou, Y.; Dibley, K.; Tyerman, S.; Furbank, R.; Patrick, J.
Fonte: C S I R O Publishing Publicador: C S I R O Publishing
Tipo: Artigo de Revista Científica
Publicado em //2007 Português
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Interest in nutrient loading of seeds is fuelled by its central importance to plant reproductive success and human nutrition. Rates of nutrient loading, imported through the phloem, are regulated by transport and transfer processes located in sources (leaves, stems, reproductive structures), phloem pathway and seed sinks. During the early phases of seed development, most control is likely to be imposed by a low conductive pathway of differentiating phloem cells serving developing seeds. Following the onset of storage product accumulation by seeds, and, depending on nutrient species, dominance of path control gives way to regulation by processes located in sources (nitrogen, sulfur, minor minerals), phloem path (transition elements) or seed sinks (sugars and major mineral elements, such as potassium). Nutrients and accompanying water are imported into maternal seed tissues and unloaded from the conducting sieve elements into an extensive post-phloem symplasmic domain. Nutrients are released from this symplasmic domain into the seed apoplasm by poorly understood membrane transport mechanisms. As seed development progresses, increasing volumes of imported phloem water are recycled back to the parent plant by process(es) yet to be discovered. However...

Context-dependency in the effects of nutrient loading and consumers on the availability of space in marine rocky environments

Bulleri, F.; Russell, B.; Connell, S.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em //2012 Português
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Background: Enhanced nutrient loading and depletion of consumer populations interact to alter the structure of aquatic plant communities. Nonetheless, variation between adjacent habitats in the relative strength of bottom-up (i.e. nutrients) versus top-down (i.e. grazing) forces as determinants of community structure across broad spatial scales remains unexplored. We experimentally assessed the importance of grazing pressure and nutrient availability on the development of macroalgal assemblages and the maintenance of unoccupied space in habitats differing in physical conditions (i.e. intertidal versus subtidal), across regions of contrasting productivity (oligotrophic coasts of South Australia versus the more productive coasts of Eastern Australia). Methodology/Principal findings: In Eastern Australia, grazers were effective in maintaining space free of macroalgae in both intertidal and subtidal habitats, irrespective of nutrient levels. Conversely, in South Australia, grazers could not prevent colonization of space by turf-forming macroalgae in subtidal habitats regardless of nutrients levels, yet in intertidal habitats removal of grazers reduced unoccupied space when nutrients were elevated. Conclusions/Significance: Assessing the effects of eutrophication in coastal waters requires balancing our understanding between local consumer pressure and background oceanographic conditions that affect productivity. This broader-based understanding may assist in reconciling disproportionately large local-scale variation...

Reaction of Large and Shallow Lakes Peipsi and Võrtsjärv to the Changes of Nutrient Loading

NÕGES Tiina; JÄRVET Arvo; KISAND Anu; LAUGASTE REET; LOIGU Enn; SKAKALSKI Boris; NOGES PEETER
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Articles in Journals Formato: Printed
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More than 20-year monitoring of Estonian rivers reveals that the loading of nitrogen to large shallow lakes Peipsi (3,555 km2, mean depth 7.1 m) and Võrtsjärv (270 km2, mean depth 2.8 m) decreased substantially in the 1990s. Phosphorus loading decreased to a much smaller extent than nitrogen loading. In L. Võrtsjärv both N and P concentrations followed the decreasing trends of loading, which show the high sensitivity of large shallow lakes to catchment processes. Our study showed a positive relationship between P content in sediments and the relative depth of the lake. Assumingly the resilience of a lake in responding to the reduction of nutrient loading decreases together with the decrease of its relative depth. In L. Peipsi the concentration of P has not decreased since the 1990s. Our data show indirectly that P loading from Russia to L. Peipsi may have increased. The N/P ratio has decreased in both lakes. Cyanobacterial blooms have been common in both lakes already at the beginning of the 20th century. The blooms disappeared during heavy nitrogen loading in the 1980s but started again in L. Peipsi in recent years together with the drop of the N/P ratio. In L. Võrtsjärv the N/P ratio is higher and the ecosystem is more stable although the share of N2-fixing cyanobacteria increased from the 1990s. Reappearing cyanobacterial blooms in L. Peipsi have caused fish-kills in recent years. In L. Peipsi summer/autumn fishkills during water-blooms are a straightforward consequence of reduced nitrogen level at remaining high phosphorus level while in L. Võrtsjärv the climatic factors affecting water level are more critical - at low water level winter fish-kills may occur. In L. Võrtsjärv nutrient loading has decreased and water quality has improved...

Anthropogenic influence on the degradation of an urban lake ? the Pampulha reservoir in Belo Horizonte, Minas Gerais, Brazil.

Friese, Kurt; Schmidt, Gerald; Lena, Jorge Carvalho de; Nalini J?nior, Herm?nio ?rias; Zachmann, Dieter W.
Fonte: Universidade Federal de Ouro Preto Publicador: Universidade Federal de Ouro Preto
Tipo: Artigo publicado em periodico
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The artificial reservoir Lagoa da Pampulha in central Brazil has been increasingly affected by sediment deposition and pollution from urban and industrial sources. This study investigates water chemistry and heavy metal concentrations and their fractionation in the lake sediment using ICP-OES, ICP-MS, and XRD analyses. Fractionation analysis was done by sequential extraction under inert gas as well as after oxidation. The lake exhibits a permanent stratification with an oxygen-free hypolimnion below 2mdepth. Nutrient concentrations are enriched for phosphorous components (SRP,PO4). In the sediment it was not possible to detect oxygen. Carbon, sulfur, and most of the analyzed heavy metals are enriched in the top sediment layer with a pronounced down ward decrease, indicating the presence of an anthropogenic influence. Statistic alanalysis, including correlations and a Principal Component Analysis (PCA) of depth-related total concentration data, helps to distinguish presumably anthropogenic heavy metals from geogenic components. Some samples with high element concentrations in the sediment also show elevated concentrations in their pore water. Analyses of element distribution between sediment and pore water suggest a strong bonding of heavy metals to the anoxic sediment. The trend to wards elevated solubility in the pore water of oxidized samples is clear for most of the analyzed elements. Fractionation analysis reveals characteristic associations of selected elements to specific mineral bonding forms. In addition...

Nutrient Loading Increases Red Snapper Production in the Gulf of Mexico

Courtney, Joshua M.; Courtney, Amy C.; Courtney, Michael W.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 21/06/2013 Português
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A large, annually recurring region of hypoxia in the northern Gulf of Mexico has been attributed to water stratification and nutrient loading of nitrogen and phosphorus delivered by the Mississippi and Atchafalaya rivers. This nutrient loading increased nearly 300% since 1950, primarily due to increased use of agricultural fertilizers. Over this same time period, the red snapper (Lutjanus campechanus) population in the Gulf of Mexico has shifted strongly from being dominated by the eastern Gulf of Mexico to being dominated by the northern and western Gulf of Mexico, with the bulk of the current population in the same regions with significant nutrient loading from the Mississippi and Atchafalaya rivers and in or near areas with development of mid-summer hypoxic zones. The population decline of red snapper in the eastern Gulf is almost certainly attributable to overfishing, but the cause of the population increase in the northern and western Gulf is subject to broad debate, with the impact of artificial reefs (primarily oil platforms which have incr eased greatly since the 1960s) being the most contentious point. Nutrient loading has been shown to positively impact secondary production of fish in many marine systems. The present paper offers the hypothesis that increased nutrient loading has contributed significantly to increased red snapper population in the northern and western Gulf of Mexico. Nutrient loading may be working in synergy with the abundant oil platforms both increasing primary production and providing structure encouraging red snapper to feed throughout the water column.

Predictions Wrong Again on Dead Zone Area -- Gulf of Mexico Gaining Resistance to Nutrient Loading

Courtney, Michael W.; Courtney, Joshua M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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Mississippi River nutrient loads and water stratification on the Louisiana-Texas shelf contribute to an annually recurring, short-lived hypoxic bottom layer in areas of the northern Gulf of Mexico comprising less than 2% of the total Gulf of Mexico bottom area. This paper observes that the NOAA and LUMCON have now published errant predictions of possible record size areas of temporary bottom water hypoxia ("dead zones") three times since 2005, in 2008, 2011, and 2013 and that the LUMCON predictions of the area of hypoxic bottom water average 31% higher than the actual measured hypoxic areas from 2006 to 2014. These systematically high predictions depend on the assumption that the susceptibility of the Gulf of Mexico to forming hypoxic areas in response to nutrient loading has been relatively constant since 2001, though the susceptibility has been occasionally adjusted upward in different models. It has been previously suggested that tropical storms in a given year that occur on the Louisiana-Texas shelf between the peak nutrient loading in spring and formation of the hypoxic zone in summer can mitigate the size of the hypoxic zone that year through mixing of stratified well oxygenated lighter and warmer surface layers and oxygen depleted heavier and cooler bottom layers. This paper suggests several reasons why the Louisiana-Texas shelf may be systematically growing less susceptible to a given level of nutrient loading over time so that predictions based on the measured area of temporary bottom water hypoxia prior to 2006 tend to be too big in recent years.; Comment: 5 pages...

Epiphyte load on the seagrass Posidonia oceanica (L.) Delile does not indicate anthropogenic nutrient loading in Cabrera Archipelago National Park (Balearic Islands, Western Mediterranean); La biomasa de epífitos de la angiosperma marina Posidonia oceanica (L.) Delile no es indicadora de aportes antropogénicos de nutrientes en el Parque Nacional Archipiélago de Cabrera (Islas Baleares, Mediterráneo Occidental)

Terrados, Jorge; Medina-Pons, Francisco Javier
Fonte: Consejo Superior de Investigaciones Científicas (España) Publicador: Consejo Superior de Investigaciones Científicas (España)
Tipo: Pre-print Formato: 429356 bytes; application/pdf
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To be published in Scientia Marina: http://www.icm.csic.es/scimar/index.php/secId/6/IdArt/3731/.; [EN] The epiphyte load on the leaves of the seagrass Posidonia oceanica (L.) Delile was estimated at the end of summer in three sites and two depths (7 m and 17 m) of the Cabrera Archipelago National Park (Balearic Islands, Western Mediterranean) from 2004 to 2006 to evaluate if epiphyte load could be used as an indicator of anthropogenic nutrient loading in the shallow marine ecosystems of the park. Asymmetrical ANOVA was used to divide data variability into two components: the contrast between the site receiving direct anthropogenic inputs of nutrients and organic matter (Es Port) and the two control sites (Cala Santa María, Es Burri); and the variability between the control sites. The nitrogen concentration in P. oceanica leaves was higher in Es Port than in Cala Santa María and Es Burri but only at 7 m depth. There was no difference between the epiphyte load on P. oceanica shoots in Es Port and the sites without inputs at both 7 m and 17 m. However, the epiphyte load in Es Burri was higher than that in Cala Santa María at both depths. The results show that the epiphyte load on P. oceanica shoots was not a sensitive indicator of anthropogenic nutrient and organic matter loading in Cabrera Archipelago National Park.; [ES] La biomasa de epífitos y el contenido en cenizas de los mismos...

Measuring the Economic Value of Nutrient Assimilation in the Upper Neuse

Macias, Adrian
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Masters' Project
Publicado em 18/04/2012 Português
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Private land trusts and public agencies, such as NC Division of Parks and Recreation and NC Wildlife Resources Commission, have traditionally measured their work in “bucks and acres.” Both the public demand for targeted investments in conservation and emerging markets for nitrogen and phosphorus offsets are pushing conservation land managers to measure the ecosystem services for both new and existing projects. By quantifying these benefits, land managers hope to increase the perceived value of conservation land and the services they provide. The Upper Neuse River Basin, which supplies a majority of the potable water required by the Raleigh-Durham Triangle region, is the focal point of this report. In addition to the competing water consumption demands of the area, such as agriculture, industrial, and landscaping, the water supply is being stressed by nutrient loading. Excessive nutrient loading can disrupt the ecological balance in a watershed, reducing water quality, increasing algae blooms, degrading the aesthetic value of water bodies, and threatening fish and wildlife. Impaired waters are also more difficult to treat, increasing costs for water treatment plants downstream. It has been established that vegetated riparian buffers can help keep water supplies clean by filtering out surface and subsurface pollution. However...

Biogeomorphodynamics of Coastal Ecosystems under Conditions of Climate Change and Nutrient Enrichment

Margida, Michaela Gabrielle
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Tese de Doutorado
Publicado em //2013 Português
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At a given time, tidal landforms inhabit one of three alternate elevation-determined stable states: salt marsh, sub-tidal platform, or tidal flat. The balance between soil production and sea level rise controls transitions between states. Due to increasing anthropogenic inputs to the carbon and nitrogen cycles, CO2 and nutrient enrichment rates are rising. What effect will this have on the evolution of the tidal landform? The present thesis recognizes that (1) soil production depends on halophyte biomass, (2) nutrient enrichment promotes a shift in biomass production from below- to aboveground thus increasing potential for sediment trapping, and (3) elevated CO2 causes an increase in total biomass production. Through use of point- and one-dimensional models, the present thesis finds that under constant suspended sediment levels equal to 20 kg/m3, (1) nutrient enrichment decreases accretion and increases suspended sediment requirements necessary to maintain accessibility of the salt marsh state, (2) elevated CO2 increases accretion decreases suspended sediment requirements necessary to maintain accessibility of the salt marsh state, and (3) the increase in accretion affected by CO2 addition is greater in magnitude than the decrease affected by nutrient enrichment. Thus we can infer that in a future scenario including increasing CO2...

Optimizing Nutrient and Timber Management for the Town of Butner, NC

Cass, David; Levo, Brian; Lott, Elizabeth
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Masters' project
Publicado em 29/04/2011 Português
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The following report documents the findings of a client-focused group Master’s Project completed at the Nicholas School of the Environment at Duke University. The project’s purpose is to support the client’s goal to optimize nutrient and timber management in a 750-acre forested tract owned by the Town of Butner in Granville County, North Carolina. Excess nitrogen and phosphorus delivery to drinking water reservoirs has become a concern in the North Carolina piedmont as development pressure increases in surrounding watersheds. The Falls Lake Nutrient Strategy is among several new regulations aimed at reducing nitrogen and phosphorus delivery to an increasingly eutrophic public water supply. While the regulation pressures upstream communities to reduce their impact, mitigation strategies are diverse and can be costly to local governments. Even though a market-driven nutrient trading credit system is included in the Falls Lake Nutrient Strategy, there is currently no opportunity to earn credits through avoided deforestation or land conservation, commonly called “conservation credits”. The Town of Butner is interested in novel approaches to managing its nutrient loading and the possibility of earning conservation credits while managing its forestland for timber. There were four objectives to this project...

Summary Analysis Of The North American (US Portion) OCED Eutrophication Project: Nutrient Loading - Lake Response Relationships And Trophic State Indices

Rast, Walter; Lee, G. Fred
Fonte: Universidade de Delaware Publicador: Universidade de Delaware
Tipo: Relatório Formato: 22920982 bytes; application/pdf
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The US participation in the OECD Eutrophication Program of having 20 investigators prepare reports on the nutrient load-lake and impoundment response relationships for their respective water bodies. This report presents a critical review of these overall relationships with particular emphasis given to evaluation of the Vollenweider nutrient load-trophic state formulations. This review includes consideration of the nutrient load response relationships for 38 water bodies, or parts of water bodies, located throughout the US, with the preponderance located in the northern half of the US. It has been found that the Vollenweider nutrient load relationship involving water body mean depth, hydraulic residence time and phosphorus load correlates well with the trophic states assigned by the US OECD eutrophication study investigators. A good correlation has also been found between phosphorus loading, normalized as to hydraulic residence time and mean depth, and the average chlorophyll and water clarity (as measured by Secchi depth) for the US OECD water bodies. In general, phosphorus and nitrogen loads to US OECD water bodies were within a factor of + two of the loads predicted on the basis of average nutrient concentrations within the water bodies and on the land use patterns within the water body watersheds. Generalized nutrient export coefficients have been developed in this study...

Technical Analysis Of Response Of Chesapeake Bay Water Quality Model To Loading Scenarios

Thomann, Robert V.; Collier, James R.; Butt, Arthur; Casman, Elizabeth; Linker, Lewis C.
Fonte: Universidade de Delaware Publicador: Universidade de Delaware
Tipo: Relatório Formato: 8984676 bytes; application/pdf
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A modeling framework was constructed for the Chesapeake Bay system to provide a credible basis to assist the decision-making process and to further the understanding of Bay water quality processes and the sensitivity of such processes to external nutrient loading. The modeling structure consists of a Watershed Model to generate nutrient loads from the Bay sub-basins; a three-dimensional, time variable hydrodynamic model; and a three-dimensional, time variable model of water quality coupled to a model of sediment chemistry.

Water quality monitoring to assess the effect of non-point source nutrient and other pollutant loads on estuarine waters, southern New Castle County, Delaware tributaries of the Delaware Bay

Mundel, Anne
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
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Madsen, John; This study established water quality monitoring baseline values for the discharge of nutrient and non-pollutant loads from two drainage basins prior to suburban housing with golf course development. The drainage basins studied were the Beaver Branch and Hangman’s Run in southern New Castle County, Delaware. Beaver Branch drains directly into the upper portion of the Blackbird Creek, the principal waterway within one component of Delaware’s National Estuarine Research Reserve. Water quality monitoring included the collection of field measurements and samples for laboratory analyses at two-week intervals for the duration of this two-year project. In addition, a series (~2-3 per season) of storm-event, field, and biweekly laboratory measurements were collected at the sampling sites. Field measurements included specific conductivity, temperature, pH, depth, turbidity, salinity, and dissolved oxygen. Laboratory measurements of total dissolved and suspended solids, chlorophyll a, b, and c, pheophytin a, silicate, and dissolved and particulate constituents of ammonium-nitrogen, nitrate-nitrogen, total Kjeldahl nitrogen, orthophosphate, total phosphates, total dissolved phosphorus, and chemical oxygen demand. These data were collected to analyze the loading rates of nitrate species...