Excessive delivery of fine sediment from agricultural river catchments to aquatic ecosystems can degrade chemical water quality and ecological habitats. Management of accelerated soil losses and the transmission of sediment-associated agricultural pollutants, such as phosphorus, is required to mitigate the drive towards sustainable intensification to increase global food security. Quantifying soil erosion and the pathways and fate of fine-grained sediment is presently under-researched worldwide, and particularly in Ireland. This thesis established a sediment monitoring network upon an existing catchment study programme (Agricultural Catchments Programme) in five instrumented catchments (~10 km2) across Ireland. The research used novel, high quality measurement and analysis techniques to quantify sediment export, determine controls on soil erosion and sediment transport, and identify sediment contributions from multiple sources in different agricultural systems over time to evaluate approaches to fine sediment management. Results showed suspended sediment measurement using a novel ex situ methodology was valid in two of the study catchments against in situ and direct depth-integrated cross-section methodologies. Suspended sediment yields in the five intensive agricultural catchments were relatively low compared to European catchments in the same climatic zone, attributed to regionally-specific land use patterns and land management practices expressed in terms of ‘landscape complexity’ (irregular, small field sizes partitioned by abundant hedgerows and high drainage ditch densities) resulting in low field-to-channel connectivity. Variations in suspended sediment yield between catchments were explained primarily by soil permeability and ground cover, whereby arable land use on poorly-drained soils were associated with the largest sediment yields. Storm-event sediment export and sediment fingerprinting data demonstrated that sediment connectivity fluctuations resulted from rainfall seasonality, which in turn regulated the contrasting spatial and temporal extent of surface hydrological pathways. Increased transport occurred when and where sediment sources were available as a result of hillslope land use (low groundcover) or channel characteristics. Field topsoils were most vulnerable when low groundcover coincided with surface hydrological pathways; frequently on poorly-drained soils and following extreme rainfall events on well-drained soils as storage decreased. Although well-drained soils currently demonstrate low water erosion risk, past sugar beet crops exposed freshly drilled soils during periods of greater rainfall risk and soil removal during crop harvesting. Sediment loss from grassland catchments dominated by poorly-drained soils and extensive land drainage (sub-surface and surface) primarily derived from channel banks due to the delivery of high velocity flows from up-catchment drained hillslopes. Catchment specific soil erosion and sediment loss mitigation measures are imperative to cost-effectively preserve or improve soil and freshwater ecosystem quality worldwide.

Phosphorus is an essential nutrient for aquatic life forms and plays a major role in the algae blooms that occur in lakes and reservoirs. It is considered a primary limiting nutrient of phytoplankton growth in streams, lakes, and reservoirs. Excess amounts of phosphorous may cause excess growth and biomass of algae. If phosphorus is available in excess, often from sewage and industrial discharges, the high levels in a lake or reservoir can lead to eutrophication. Utah Lake is a shallow, basin-bottom lake in a semi-arid climate with sediments that are thousands of feet thick. Starting 165 years ago, humans have been discharging wastewater into Utah Lake, which in our day has raised serious questions on how the state can mitigate the negative effects of the external nutrient loading. Even though Utah Lake receives a significant amount of anthropogenic phosphorous, there are high levels of phosphorous in geologic deposits in the area, providing a long-term natural source. This study intends to provide data on the current distribution of phosphorous in lake sediments, potential for that phosphorous to be released into the water column affecting phytoplankton growth, and how historic lake sediment phosphorous levels compare to the levels in current sediments. Sediments play an important role in the overall metabolism of shallow lakes. They supply the water column with phosphorus and must be considered as they serve as a sink and source. More than 50 branches of surface flow discharge into Utah Lake, 15 of which are major. Based on previous data, a positive retention of phosphorus from these branches occurs in the lake, of which the sediment plays a role. Phosphorus release from sediment occurs under very complicated processes under many different conditions. Some main influential factors include the iron and calcium content, redox potential, microbial processes, turbidity, sediment resuspension, temperature, and pH. In this study, I analyzed 85 sediment samples sampled across Utah Lake for total phosphorus. I created Geospatial maps to show the phosphorous distribution. The data showed an average phosphorus level of 666 ppm and varied in distribution throughout the lake, though the majority of the lake had levels in the 600 to 800 ppm range. There were a few samples, which had lower total phosphorus levels, in the 200 to 300 ppm range. Based on the map, I found that these lower values were in locations representing potential springs. I hypothesize that this underground water source leached some of the phosphorous from the sediments in these areas. I found that total phosphorus concentrations in current lake sediment are quite similar to phosphorus levels in historic lake sediments levels. I also performed laboratory experiments to characterize sediment-water interactions and estimate the amount of phosphorus that could be released from lake sediments to the water column.

archives@tulane.edu / Over the past two centuries, coastal wetlands have become increasingly threatened by accelerated relative sea-level rise and anthropogenic modification. Engineered structures such as sea walls, levees, and drainage systems prevent natural processes of sediment distribution, reducing the resilience of coastal ecosystems. Land subsidence and shoreline erosion combine with global sea-level rise to make low-elevation coastal zones increasingly vulnerable to submergence. This dissertation examines processes of sediment accumulation, compaction, and relative sea-level rise in coastal wetlands and assesses strategies for restoration. I find that organic content strongly controls sediment compaction in wetland sediments. At least 80% of compaction happens quickly, largely within the first 100 years after deposition and in the top 1 m of the subsurface. This rapid shallow compaction is generally not recorded by traditional methods of measuring relative sea-level rise in low-elevation coastal zones (i.e., tide gauges and global navigation satellite systems). As a result, tide gauges generally underestimate rates of relative sea-level rise in low-elevation coastal zones and these areas may be at a greater risk of flooding than previously realized. However, despite accelerated rates of relative sea-level rise and rapid sediment compaction, coastal restoration efforts such as river diversions can be successful in building new land in some areas. I find that sediment deposition responds non-linearly to water discharge, reaching a maximum at moderate discharge. Wetlands are more likely to keep up with relative sea-level rise if hydrodynamic conditions are optimized to retain mineral sediment in targeted restoration areas. / 1 / Margaret Keogh

A palaeolimnological study was carried out on a high-resolution, 7.62 m-long core (RU188-07) from northern Lake Rotorua, North Island. The core consists predominantly of olive diatomaceous ooze, laminated in places, and contains five tephras including Tarawera (1886 A.D.), Kaharoa (c. 1314 A.D.), Taupo (c. 233 A.D.) and Whakatane (c. 5500 cal. years B.P.). The core terminated in Whakatane Tephra giving the sediment a maximum age of 5530 60 cal. years B.P. An age model for the sediment was developed using tephrochronology. Radiocarbon dates obtained on the sediment returned ages too old because of contamination by old CO2 or CH4, or both. Investigations carried out on the core included spectrophotometric, sedimentological and geochemical analyses, and diatom identifications, which provided a number of proxies from which inferences were made about lake history, catchment development, and palaeoclimate since c. 5500 cal. years B.P. The laminations, evident only in the upper, post-Kaharoa Tephra part of the record, comprise alternations of thin, dark, detrital deposits and pale, relatively fine-grained diatom assemblages. Sediment geochemistry indicates that the Rotorua catchment has undergone several changes since c. 5500 cal. years B.P., alternating between periods of variable and stable environmental conditions. Following the Whakatane and Waimihia eruptions and up to approximately 3000 cal. years B.P., the catchment surrounding Lake Rotorua was rather unstable. Fluctuations in many of the proxies during this period are likely to be associated with a variable climate with periods of storminess, coinciding with the establishment of ENSO conditions in New Zealand. A notable feature of the record is two phases of stability, the first following the Taupo eruption (from c. 1700 cal. years B.P. to c. 630 cal. years B.P.) and the second from c. 580 cal. years B.P. to c. 300 cal. years B.P. The latest, most significant event in the catchment history of Lake Rotorua was the settlement by Polynesians. M.S. McGlone implied from pollen profiles (from Holden's Bay) that initial settlement took place around the time of the Kaharoa eruption (c. 630 cal years B.P.; c. 1314 A.D.), but the sediment chemistry and erosion profiles obtained here, from the northern part of Lake Rotorua, indicate that although there may have been some early clearing in the northern catchment for tracks or buildings, large-scale clearing in the area probably did not occur until considerably later, c. 300 cal. years B.P. Also contained within the sediments are three layers of reworked tephric material that probably originate from the transfer of coarse grained tephra from shallow to deeper water during large storms at c. 1300 cal. years B.P, c. 520 cal. years B.P, and c. 220 cal. years B.P. Each event coincides with storm events inferred from records from Lake Tutira in eastern North Island. Because of Lake Rotorua's inland position, these inferred storm events probably represent only the largest cyclonic events (e.g. ex-tropical cyclones).

Human activities such as urban settlement, farming, forestry and recreation, have caused deterioration of water quality in many freshwater lakes worldwide. Apart from anthropogenic impacts, it is also recognized that climate has a direct influence on lake water temperature, nutrient loads, phytoplankton abundance and chemistry. However, little is known about the potential effects of future climate change on lake water quality. Understanding the dynamics, abundance and availability of nutrient pools in lake bottom sediments is fundamentally important for predicting how, and over what time-scales, lake ecosystems will respond to future scenarios such as climate change, in-lake restoration or altered external nutrient loading. Through a sediment field study on 14 different lakes, and applications of complex lake ecosystem models to three New Zealand lakes, this study examined the spatial and temporal dynamics of sediment nutrient concentrations, and made considerations of the effects of restoration measures and future climate change on lake water quality. To gain insight into processes influencing the dynamics of horizontal and vertical gradients of sediment nutrient concentrations, intact sediment cores were collected from twelve lakes within the Bay of Plenty province, North Island of New Zealand. In addition, intact sediment cores were collected from shallow Lake Te Waihora (Ellesmere) in the Canterbury province, South Island of New Zealand and shallow Lake Taihu in the Jaingsu province, China. The observed vertical concentration profiles of total phosphorus (TP) in the sediments revealed that the shape of these profiles can be similar across gradients of widely differing trophic status. Empirical and mechanistic steady state profile models were derived to describe the vertical distribution of total carbon (TC), total nitrogen (TN) and TP concentrations in the sediments. These models revealed that density-driven burial and biodiffusive mixing, which in the models also includes effects of redox-driven gradients, are strongly correlated with vertical gradients of sediment TC, TN and TP content, whereas lake trophic status was not. Despite enhancing knowledge of the processes influencing vertical gradients of sediment nutrient concentrations, little is known about the rates at which sediment nutrient concentrations may change as a response to changes in external loading or climate. Studies into the composition of bottom sediments have been undertaken intermittently over the past three decades for the 12 lakes in the Bay of Plenty. These studies, together with the data collected in this study, were used to quantify temporal changes in sediment chemistry across the lakes. Comparison of the data collected in this study with results from a survey in 1995 showed that surficial sediment (0-2 cm) TP concentrations have increased in three of the 12 lakes, at rates ranging from 27.5 to 114.4 mg P kg-1 dry wt yr-1. TN concentrations in surficial sediments have increased in nine of the 12 lakes at rates ranging from 51.8 to 869.2 mg N kg-1 dry wt yr-1. A correlation analysis revealed that temporal changes in sediment TP and TN concentrations were not significantly linearly related (pgt0.05) to catchment area or temporal changes of different water column indices considered to reflect lake trophic state, including annual mean water column concentrations of TP, TN or chlorophyll a (Chl a). While vertical profiles of sediment nutrient concentrations can be used to provide information about historical changes of trophic status in lakes, little is known about horizontal variability of sediment nutrient concentrations, including possibly relationships with horizontal variations in water column variables. In the large, shallow and eutrophic Lake Taihu, China, there are distinct horizontal water column concentration gradients of nutrients and Chl a. Concentrations are generally high in the north, where some of the major polluted tributaries enter the lake, and relatively low in the south, where macrophytes generally are abundant. To test whether these water column concentration gradients are similarly reflected in spatial heterogeneity of nutrient concentrations within the bottom sediments of Lake Taihu, I examined correlations between concentrations of TP and TN in surficial sediments (0-2 cm) and TP, TN and Chl a concentrations in water column samples determined for 32 sites in 2005. Linear correlation analysis revealed that surficial sediment TP concentrations across the 32 stations were related significantly, though weakly, to annual mean water column concentrations of TP and TN as well as Chl a. Correlations of surficial sediment TN with water column variables were, however, not significant (p gt 0.05). To better understand the effects of future climate change on lakes of different trophic status, I applied the one-dimensional lake ecosystem model, DYRESM-CAEDYM, to oligo-mesotrophic Lake Okareka, eutrophic Lake Rotoehu and highly eutrophic Lake Te Waihora. All three models were calibrated based on a three-year period (July 2002 - June 2005) and validated on a separate two-year period (July 2005 - June 2007). The model simulations generally showed good agreement with observed data for temperature, dissolved oxygen (DO), and total nutrient and Chl a concentrations. To represent a possible future climate of 2100, temperature predictions were derived from the regional climate model, DARLAM, based on the Intergovernmental Panel on Climate Change (IPCC) A2 scenario, which suggests that air temperatures by the year 2100 will increase by an average of 2.5 'C and 2.7 'C for the Bay of Plenty and the Canterbury province, respectively, relative to the base scenario (years 2002-2007). Model simulations of the future climate scenarios indicate that climatic changes generally will lead to a degradation of lake water quality in all three lakes, especially during summer months, and further suggest that the effects on annual mean surface concentrations of TP, TN and Chl a will be equivalent to an increase in external TN and TP loading by 25-50%. Simulations for Lake Rotoehu, where diatoms and cyanophytes were represented in the conceptual model, further suggest that cyanophytes will be more abundant in the future, increasing by gt15% in annual mean biomass. Although the effects of climate change may be delayed or slightly mediated by the chemical resilience of the sediment nutrient pools, the effects of climate change on lake water quality in the New Zealand lakes will be of a magnitude that should be considered as management strategies are planned and implemented, thus increasing the probability of successful preservation or improvement in water quality in future decades.

Urbanisation in coastal catchments has significantly increased not only the input of terrestrial sediment to the marine environment but also the input of contaminants. In Tamaki Estuary, Auckland, heavy metals have accumulated in the upper estuarine muddy sediments and metal contamination has been detected on downstream intertidal sandflats. Sub-lethal levels of heavy metal contamination may affect the growth and behaviour of benthic organisms, which in turn may influence key ecosystem processes and productivity. The aim of this study was to examine whether the burial rate of an ecologically important bivalve species (Austrovenus stutchburyi) differed between a contaminated and a lesser-contaminated site and whether burial rates were affected by density. A secondary aim was to determine whether the burial of Austrovenus affected sediment transport and consequently if this was affected by density. This study demonstrated no consistent difference in burial time between source populations (sites). This was explained by a lack of measured difference in the condition index and heavy metal tissue loading of Austrovenus used throughout this study. The present range of contamination measured in Tamaki Estuary, Auckland, did not have negative biological consequences on the key ecosystem engineer, Austrovenus stutchburyi. Contamination levels in Tamaki Estuary may not be high enough to cause major physiological or behaviour changes to infaunal organisms, such as Austrovenus. Sediment erodability was not significantly correlated with any measured environmental and biotic factors. Austrovenus density was the only predictor variable that could be used to explain any variation in sediment erodability. There was no significant density effects observed between the amounts of sediment eroded for densities gt; 150 ind. m-2. There was a significant difference between sediment void of Austrovenus (0 ind. m-2; smooth, flat undisturbed sediment surface) and sediment containing Austrovenus (gt;150ind. m-2; physical structure on/in the sediment surface, increase in bed roughness). These results indicate that there is little or no effect of Austrovenus on the critical erosion threshold, suggesting that in the absence or presence of Austrovenus the current required to erode 10 g m-2 of sediment would remain somewhere between 28.5 and 30.5 cm s-1. This study found that there was considerable variation in the burial rate of individuals and the greatest variation was recorded in the lowest density treatments (150 ind. m-2), which corresponded to the same density that had the greatest variation in sediment erodability. Further investigations are needed to gain a better understanding into the important roles (the importance of the various feedbacks and limitations and interrelationships) that Austrovenus play in the soft-sediment ecosystem, as losses of this species are likely to have large-scale impacts on the wider soft-sediment communities and ecosystem functioning.

The interaction of microorganisms with sediments can enhance their survival by reducing exposure to various stressors and thus marine sediments may act as reservoirs for pathogenic microorganisms. In coastal waters there can be an increased risk of infection to humans due to the possible re-suspension of these microorganisms during recreational activities. This research attempts to more accurately identify environmental exposure in the first stage of a health risk assessment in recreational coastal waters. Techniques were developed to successfully separate microorganisms from sediment particles. Of the methods investigated, subjecting diluted sediment samples to a sonication bath for 10 minutes was found to be the most efficient separation technique over a range of sediment types. This method was therefore used in the subsequent studies to enumerate organisms from the surface sediment layer, as distinct from the water column. Faecal coliforms were enumerated by membrane filtration in both water and sediment from three Adelaide metropolitan recreational coastal sites, chosen to represent different physical sediment characteristics, over a 12-month period. All sites investigated met current National Health and Medical Research Council Guidelines for primary contact recreation. Faecal coliform concentrations were generally greater in sediment compared with overlying water for all samples. This was most evident in sediment consisting of greater silt/clay and organic carbon content (with up to 1000 times higher concentrations in the surface sediment layer compared with overlying water). For coastal recreational sites impacted by stormwater or river discharges, high faecal coliform concentrations were found to be associated with rainfall. A laboratory-based microcosm study utilising intact sediment cores was undertaken to determine the decay rates of faecal indicator organisms (E. coli, enterococci and somatic coliphage) and pathogens (Salmonella derby and S. typhimurium) in both overlying water and in various sediment types. For all organisms tested, temperature had an inverse relationship with survival. Greater decay was observed in the overlying water compared to the surface sediment layer. Small particle size and high organic carbon content was found to be more conducive to microbial survival. In general, decay rates of E. coli were significantly greater than enterococci and coliphage. Although no significant correlations were observed between decay rates of the pathogens and indicator organisms, decay of Salmonella spp. in overlying water more closely resembled that of E. coli than that of other indicators. Using decay rates measured in the microcosm study and available dose-response data, a quantitative microbial risk assessment (QMRA) utilising Monte Carlo simulation was undertaken to estimate the risk of infection to Salmonella spp. and rotavirus following exposure to recreational coastal water subject to a range of faecal contamination levels. For modelling purposes, the assumption was made that rotavirus decay was equivalent to coliphage decay. The probability of infection from rotavirus due to exposure to contaminated recreational coastal water was greater than that for Salmonella spp. under all scenarios. This increased probability of infection is linked to the high infectivity of rotavirus compared to Salmonella spp. Results of this research highlight the limited effectiveness of using prescribed faecal coliform concentrations in the water column alone to estimate the risk of exposure to pathogenic microorganisms during recreational activity at coastal areas. It demonstrated that coastal sediments act as a reservoir for both indicator and pathogenic organisms released into the coastal environment. This suggests an increased exposure risk if these organisms are resuspended back into the water column during recreational activity. A combined risk-based monitoring program would provide a more robust and reliable estimate of health risk associated with coastal recreational areas.

Thesis (M.S.)--University of Nevada, Reno, 2005. / "December, 2005." Includes bibliographical references (leaves 103-112). Online version available on the World Wide Web.

<p>Brominated flame retardants (BFRs) has for many years been used in products to reduce their</p><p>flammability, mainly in electronic products, textiles and construction materials.</p><p>In 2003, Sweden imported 300 tons of brominated flame retardants.</p><p>Leakage of these compounds has polluted natural environments. Fishes has shown increased</p><p>contents of these substances, especially fat fish, since brominated flame retardants tends to</p><p>accumulate in fatty tissues.</p><p>They are also regarded as persistent and that gives them the ability to travel long distances.</p><p>What also is really scary is that increased levels of brominated flame retardants have been</p><p>detected in human breast milk.</p><p>The knowledge of the brominated flame retardants is limited and not so much research has been</p><p>done in this field. There are many reasons though, to keep the research going. Partly their</p><p>structural resemblance to well-known toxics as PCB, but also their ability to accumulate in</p><p>biological systems and enrich in food chains.</p><p>In which way they affect humans we really don’t know yet. Experiments on mice have been done</p><p>and behavioural disturbances were observed as well as a decrease in learning capacity.</p><p>The BRFs chosen for this study are hexabromocyclododecan (HBCD) and a polybrominated</p><p>diphenyl ether (PBDE) called pentabromodiphenylether (BDE 99).</p><p>About 25 % of the flame retardants produced in the world every year, consists of the brominated</p><p>ones. If we look at the PBDEs it’s mainly tetrabromodiphenylether (BDE 47),</p><p>pentabromodiphenylether (BDE 99), octabromodiphenylether (BDE 205) and</p><p>decabromodiphenylether (BDE 209) that are common flame retardants.</p><p>As from July 1st 2006, PBDE was forbidden in electric and electronic products (15).</p><p>January 1st 2007, a Swedish prohibition concerning the use of BDE-209 was established. BDE-</p><p>209 is not allowed on the Swedish market if the content of substance exceed 0,1 percent of weight</p><p>(23).</p><p>BDE-99 is classified as environmentally dangerous and a healthrisk. It´s not only toxic for</p><p>waterliving organisms but also for humans if exposed during a long time (19).</p><p>We shall develop a well functioning, reproducible and economic method to analyse HBCD and</p><p>PBDE in sediment. It includes extraction, cleanup and sample analyses with a ECD (electron</p><p>capture detector) equipped capillary gas chromatograph.</p><p>Several analyses of adequate diluted standards has been analysed in a GC-ECD to find suitable</p><p>temperature gradients. Then we produced spiked sediment samples with known amounts of</p><p>standards. To homogenize the spiked samples we used a mixer. As a first step in the extraction we</p><p>used acetone as a solvent. Then we used cyclohexane and NaCl (2%) to separate the nonpolar and</p><p>polar substances from each other. Cleanup with concentrated sulphuric acid was done and for</p><p>some samples we also used Florisil. To concentrate the extract it was evaporated with N2(g).The</p><p>extract was then analysed in a GC-ECD and then the results was compared with the standards.</p><p>The result of this project showed that our method of extraction is useful. We managed to extract</p><p>50 % HBCD, 30 % BDE-99 and 60 % BDE-99 (dried sediment).</p>

Thesis (D. Sc.)--Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1983. / "Funding was provided by the American Gas Association Project no. PR-153-126, the National Science Fundation under grant OCE-8014930, and NOAA-Sea Grant NA-79AA-D-00101 ; NA 79AA-D-00102." Includes bibliographical references (p. 201-205).