Search

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.earscirev.2010.04.003 Byline: David J.A. Evans (a), Stephen A. Thomson (b) Keywords: glacial sediments; North Sea Lobe; glacial depositional environment; Holderness; British-Irish Ice Sheet Abstract: Borehole records and exposures at coastal cliffs and inland quarries around Holderness are used in a critical assessment of the glacial depositional environments that operated at the margin of the North Sea lobe of the British-Irish Ice Sheet at the Last Glacial Maximum. Four lithofacies associations (LFA) are recognized in the area: LFAs 1 and 4 are laminated to massive diamictons, traditionally called the Skipsea and Withernsea tills/members, and display deformation structures indicative of stress from the NE, attenuated rafts of soft bedrock lithologies, ice-bed separation (canal fill) features and pseudo-stratification, and clast macrofabric data predominantly indicate deformation only to low strains. They are interpreted as subaqueous deposits subsequently deformed by glacier ice to create end products that lie on the glacitectonite continuum. Localized increases in strain signature are equated with the development of shear zones between onshore thickening wedges of deformed, pre-existing lake sediment. LFA 2 comprises cross-bedded clinoforms, locally steepening into foresets, at the core of linear hummocks along the central spine of Holderness (LFA 2a) and rhythmically laminated silts and sands with dropstones (LFA 2b). These sediments are interpreted as coalescent glacilacustrine subaqueous outwash fans, fining distally to lake bottom rhythmites and varves. Ice-contact deposition is evident in compressional folding, faulting and hydrofracture filling due to ice overriding, and extensional faulting associated with localized ice melt-out. Depressions produced by folding or sagging provided the accommodation space for the later deposition of LFA 2 and 3 through syntectonic sedimentation. LFA 3 comprises flat-lying beds of well to poorly sorted cross-stratified sands and gravels, interpreted as proximal proglacial braided outwash deposits laid down largely in ribbon sandar defined by the topography of abandoned ice-contact glacilacustrine depo-centres. Well developed ice wedge pseudomorphs in LFA 3 record permafrost conditions during ice sheet marginal recession, indicating that North Sea lobe oscillations may have been non-climatic or surge related. A depositional model is proposed in which 'advance' and 'retreat' phase tills/glacitectonites and associated ice-contact lake sediments are the geological imprint of a single glaciation. The initial advance of the North Sea lobe is recorded by a westerly thinning advance till (LFA 1). Later LFA 1 and 4 retreat 'tills' are strictly glacitectonites, and are thicker depositional units because later ice readvances encroached upon and cannibalized more substantial sequences of deglacial lake sediment and subaqueous ice-contact fans (LFA 2). Similar regional till architectures will be manifest wherever the palaeogeography resulted in the onshore flow of ice and the concomitant production of glacitectonites from glacial lake sediments. Author Affiliation: (a) Department of Geography, Durham University, South Road, Durham, DH1 3LE, UK (b) Laing O'Rourke Scotland, 21 Woodhall, Eurocentral, Holytown, Motherwell ML1 4YT, UK Article History: Received 21 October 2009; Accepted 13 April 2010

Midge (Insecta: Diptera: Nematocera) assemblages were examined in surface sediment samples from Lake Pieni-Kauro and the Saavanjoki River, eastern Finland, using their sedimentary remains. The aim was first to identify the forcing factors behind midge distribution within an aquatic ecosystem and second to develop new midge-based calibration models for the reconstruction of past environmental conditions, with a special focus on paleohydrology. The third objective was to apply the models to a midge stratigraphy. The effect of sampling-point selection in paleolimnological studies and its possible influence on chironomid-inferred temperature reconstructions was also assessed. The species assemblages in Lake Pieni-Kauro showed high levels of heterogeneity within the surface sediment samples, signifying that the assemblages predominantly incorporate locally dwelling fauna, instead of integrating remains from a larger area. Stream flow and water depth were the most important factors explaining the midge distributions in the lake. In addition, sampling distance from littoral vegetation (DLV), proximity of wetland, distance from shore, and organic content of the sediment were significantly correlated statistically with the midge assemblages. In the lacustrine samples, absolute midge abundance and taxon richness were highest at intermediate water depths. Because hydrological variables were the most important factors controlling the species' distributions, paleohydrological calibration models for water depth and stream flow were developed. Additionally, a transfer function for the sampling DLV was developed that can be used to track changes in the past location of littoral vegetation stands, which is often closely related to hydrological factors. The models' test use on the subfossil midge assemblages of the previously available downcore sediment sequence showed coherent and expected results, compared with previous studies and the modern observed environmental conditions of the lake. Based on the results of this study, these models can provide reliable estimates of past hydrological variability that is closely related to climatic changes and thus may provide a valuable tool for environmental management and global change assessments. This study also indicates that care should be taken in choosing the sampling point in chironomid-based calibration studies because the influence of depth may distort the temperature estimations. Key words: Ceratopogonidae; Chaoboridae; Chironomidae; eastern Finland; lake sediments; littoral vegetation; lotic index; sampling-point selection; Simuliidae; subfossil midges; transfer functions; water depth.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.earscirev.2009.07.005 Byline: Christian Beck Keywords: lake sediments; slumps; homogenites; turbidites; earthquakes; Alps; Quaternary Abstract: The late Quaternary sedimentary fills of several lakes of the north-western Alps are revealed to be possible paleo-seismological 'archives' in a moderately active seismo-tectonic region. The strongest historically reported events can be correlated with specific layers, whose textures result from different processes: i) mass failures of sub-aqueous slope deposits (especially delta foresets) evolving into hyperpycnal currents influenced by seiche effects and/or multiple reflections on lake basin slopes; ii) in situ liquefaction and flowage; and iii) micro-fracturing. Based on identification of the sedimentary signature of a well-documented historical earthquake, the paleoseismic interpretation can be extrapolated back to 16,000yrs BP with a reconstruction of a time series and textural identification of slope failure-related turbidites (the most frequent earthquake signature). The obtained time series are compatible with historical seismicity in terms of recurrence interval. Author Affiliation: Laboratoire de Geodynamique de ChaA[R]nes Alpines, U.M.R. C.N.R.S. 5025, Universite de Savoie, 73 376 le Bourget du Lac Cedex, France Article History: Received 11 September 2008; Accepted 23 July 2009

Abstract: Phosphorus (P) compounds in three different lake surface sediments were extracted by sequential P extraction and identified by [sup.31]P nuclear magnetic resonance ([sup.31]P NMR) spectroscopy. The extraction procedure primarily [...]

Diatom dissolution in surface sediment samples from two regional lake datasets in the Northern Great Plains (NGP: n = 64) and West Greenland (n = 40) is assessed using a morphological approach categorizing valves during routine diatom analysis. Two dissolution indices are derived to parameterize diatom dissolution, and, when compared between two analysts in a blind test, show good correspondence and are closely correlated to diatom fragmentation. We explore the relationships between hydrochemical and physical lake parameters (including meromixis) on dissolution within both lake regions using multivariate methods and modeled with logistic regression. Salinity is the sole significant predictor of dissolution in West Greenland but salinity, carbonate concentration ([CO.sup.2-.sub.3]]) and meromixis are significant predictors in the NGP. Limnological parameters explain 40-59% of variation in dissolution in both regions for both dissolution indices. The dissolution index methodology is applied to a short sediment sequence from Devils Lake (North Dakota), where diatom-inferred salinity inferences can be compared with a historical record of salinity fluctuations over the 20th century. Absolute errors in paleosalinity estimates are strongly correlated with diatom dissolution, with salinity overestimated in 8 out of 11 poorly preserved samples. Preservation does appear to constrain the reliability of the inferred paleosalinity at this site and may also affect the quality of diatom-based paleoenvironmental inferences elsewhere (including estimates of biogenic silica), where preserwttion state is often not explicitly considered.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.earscirev.2005.09.002 Byline: Michael H. Stephenson (a), Melanie J. Leng (b), Uisdean Michie (c), Christopher H. Vane (a) Keywords: palaeolimnology; isotopes; Orcadian; Devonian; palynology Abstract: There are few palaeolimnological studies of Palaeozoic lake deposits using methodologies developed for the study of Quaternary lakes. New research described here indicates the benefits of applying multidisciplinary high-resolution sampling and analysis on the Middle Devonian lake deposits of the Orcadian Basin in order to understand lake palaeoecology and response to water chemistry change and possible climate change. In a continuously sampled 4 m-thick lake cycle in two correlated boreholes in Caithness there are two distinct features. There is a broad trend in [delta].sup.13C of sedimentary organic matter from high values in the shallow water deposits to lower values in the deeper water deposits, attributed to changing contributions from terrestrial plant material ([delta].sup.13C.sub.org c. -28a[degrees]) and algal material ([delta].sup.13C.sub.org c. -33a[degrees]). This variation is consistent with palynological data and is best explained by proximal-distal variation as the lake filled. A smaller but well-correlated up-section decreasing [delta].sup.13C.sub.org trend occurs over approximately 1 m, starting at the cycle centre where the lake was at its deepest. Since the same feature is seen in two boreholes, we suggest that local effects of migrated bitumen, diagenesis or facies changes are unlikely to be the cause, and that changes in the carbon cycle of the lake are responsible. Explanations for this trend may relate to the source of carbon that algae utilised as the lake changed from a fresher to a more saline environment, and to changes in the carbon isotope composition of the lake water during periods of enhanced productivity. Author Affiliation: (a) British Geological Survey, Keyworth, Nottingham NG12 5GG, UK (b) NERC Isotope Geoscience Laboratory, British Geological Survey, Keyworth, Nottingham NG12 5GG, UK, and School of Geography, University of Nottingham, Nottingham NG7 2RD, UK (c) 21 Dunster Road, West Bridgford, NG2 6JF, UK Article History: Received 24 June 2005; Accepted 4 September 2005

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.earscirev.2005.10.001 Byline: Melanie J. Leng (a)(b), Philip A. Barker (c) Keywords: Diatom silica; Oxygen isotopes; [delta].sup.18O; Lakes; Palaeoenvironment; Palaeoclimate Abstract: Diatom silica (frustules) are a form of biogenic opal and contain oxygen isotopes that are being increasingly used in palaeoclimate studies. Frustules are comprised of an inner tetrahedrally bonded silica skeleton (Si-O-Si) with an outer, hydrous layer. The hydrous layer is freely exchangeable and must be removed prior to oxygen isotope measurement using oxidising reagents and/or high temperatures. Analysis of the oxygen isotope composition of diatom silica requires samples that are almost pure diatomite since extraction techniques will liberate oxygen from all the components in the sediment. There is a generally acceptable protocol involving chemistry, sieving and settling techniques and more recently laminar flow separation. Recent studies of lacustrine diatoms have shown that even a small proportion of contaminant can have a significant influence on the oxygen isotope value. All lake sediments require their own specific procedure and every sample must be scrutinised by microscopy to check for the level of contamination prior to analysis. Where sediment cannot be purified sufficiently, a semi-quantitative assessment of the diatom content can facilitate mass balance techniques. When robust preparation methods are used, diatom silica offers an important palaeoclimate proxy, providing an additional complementary, rather than an alternative, host of oxygen isotopes in carbonates. In lacustrine isotope studies it is often assumed, but rarely proven, that diatom silica form in isotope equilibrium and hence empirically derived palaeotemperature equations, usually made in vitro, can be used. Most studies lack the detailed investigation of contemporaneous materials from natural waters of the region under study to test these equations. Further investigations need to be conducted in order to understand the systematic relationship between temperature, water isotope composition and diatom isotope composition to enable quantitative interpretation of the sediment record. Experiments to test for vital effects and inter-specific differences have so far revealed little variation. It is useful to know when and where the diatom silica is formed in the modern environment, so details of diatom ecology are important in the interpretation of isotope data. Here we show that valuable palaeoclimate data can be gained from the oxygen isotope composition of diatom silica ([delta].sup.18O.sub.diatom), especially since diatoms are abundant in many lakes sensitive to climate variation where other hosts (e.g., carbonates) are absent. To date the most successful studies have been conducted in areas where the [delta].sup.18O.sub.diatom registers changes in the oxygen isotope composition of the lake water (rather than temperature) which is then related to other aspects of climate. In these studies, the range of values obtained is often greater than the error introduced by contaminating materials. Author Affiliation: (a) NERC Isotope Geosciences Laboratory, British Geological Survey, Nottingham, NG12 5GG, UK (b) School of Geography, University of Nottingham, Nottingham NG7 2RD, UK (c) Department of Geography, Lancaster University, Lancaster LA1 4YB, UK Article History: Received 5 May 2005; Accepted 16 August 2005

Benzalkonium chlorides (BACs) were successfully extracted from sediment samples using a new methodology based on accelerated solvent extraction (ASE) followed by an on-line cleanup step. The BACs were detected by liquid chromatography/ion trap mass spectrometry (LC/MS) or tandem mass spectrometry (MS/MS) using an electrospray interface operated in the positive ion mode. This methodology combines the high efficiency of extraction provided by a pressurized fluid and the high sensitivity offered by the ion trap MS/MS. The effects of solvent type and ASE operational variables, such as temperature and pressure, were evaluated. After optimization, a mixture of acetonitrile/water (6:4 or 7:3) was found to be most efficient for extracting BACs from the sediment samples. Extraction recoveries ranged from 95 to 105% for [C.sub.12] and [C.sub.14] homologues, respectively. Total method recoveries from fortified sediment samples, using a cleanup step followed by ASE, were 85% for [C.sub.12]BAC and 79% for [C.sub.14]-BAC. The methodology developed in this work provides detection limits in the subnanogram per gram range. Concentrations of BAC homologues ranged from 22 to 206 [mu]g/kg in sediment samples from different river sites downstream from wastewater treatment plants. The high affinity of BACs for soil suggests that BACs preferentially concentrate in sediment rather than in water.

Sediment cores from Spain's Salada Chiprana saline lake were analyzed using geochemical, sedimentological, pollen, charcoal and radiometric dating methods. Results indicate that the lake was formed from extensive and lengthy human interaction with the landscape, such as irrigation and agricultural uses.

A series of refinements was added to a previously completed three-dimensional eutrophication model of Chesapeake Bay. Refinements included increased grid resolution in the western tributaries and in shallow littoral areas, extension of the grid onto the continental shelf, extension of the validation period to 1985-1994, and addition of living resources. Computations of zooplankton, submerged aquatic vegetation, and benthos compared successfully with observations aggregated over annual time scales and at spatial scales on the order of 100 km(super 2).

A chemical mass balance (CMB) model, applied to polycyclic aromatic hydrocarbon (PAH) compounds, is used to apportion PAH sources in a group of seven sediment cores in the Milwaukee Basin of the central Lake Michigan area. PAH apportionment results indicate the dominance of coke oven emissions from 1925-1976, and of highway inputs from 1983-1992 for most of the seven cores. This is consistent with results of carbon particle analysis from the same basin. Milwaukee and Port Washington appear to be primary contributors of point source inputs of PAHs from coke ovens and highway dust. Wood burning is a minor source (

Research was conducted to address the relationships between physiology of sulfate-reducing bacteria (SRB) and their distribution and activity. The data show that populations of SRB preferentially occupy regions of oxygen and eukaryotes found in regions depleted in oxygen.

Subaqueous disposal is a technique that can, under suitable circumstances delay or mitigate the release of material containing high levels of dissolved compounds, for example, acid rock drainage, into the surrounding environment. The technique places the material in question under a relatively inert cap of lighter fluid in a deep basin, such as that left after mining. In many situations, because of low diffusion rates, the material may be considered as being isolated from the environment. However, there are a number of naturally occurring physical mechanisms that can quite efficiently bring this material to the surface, and hence, to the surrounding environment. We describe a modeling application to a deep and steep-sided chemically stratified lake using an extended version of the lake and reservoir water quality model, DYRESM, incorporating algorithms for detailed ice cover, heat fluxes, and also internal wave-driven boundary mixing. Sheltering and shading of the meteorological forcing is taken into account in the model. Both the field data and the model confirm the capping effects of the freshwater cap (S < 0.7 g/L) overlying the relatively salty water (S > 0.85 g/L) in the pit. Examination of the mechanistically determined vertical eddy diffusivities suggest that at depths below the surface mixed layer, double diffusion dominates over vertical mixing due to bottom-generated turbulence stemming from basin-scale internal waves. The ability of the model to simulate for periods longer than about 6 months is not addressed in this study.

Environmental geochemical studies were carried out at Nacharam Lake in Hyderabad, India, to ascertain the extent of pollution from heavy metals and radiogenic elements such as uranium and thorium in the lake sediments. Sixteen rock samples taken from the area surrounding Nacharam Lake were studied so that pollutants in the lake could be delineated as natural or anthropogenic. Concentrations of several pollutants were observed to he much greater than the world average: Lead was at 260 parts per million (ppm), barium at 2,200 ppm, nickel at 200 ppm, copper at 400 ppm, and zinc at 500 ppm. The surrounding geology consists predominantly of granites, from which high concentrations of heavy metals cannot derive. This finding indicates that these metals have anthropogenic sources. Samples of lake sediments, soil, and water were collected in 1995, 1996, and 1997 from the same area. The samples were taken during May, when the lake water recedes, and were analyzed for major and minor oxides with an X-ray fluorescence spectrometer. Trace elements were analyzed with an inductively coupled plasma mass spectrometer. The soil samples were collected from a variety of depths of up to 100 centimeters so that pollutants in the soil also could be delineated as anthropogenic or geochemical. Abnormally high concentrations of uranium (25 ppm) and thorium (60 ppm) were found in some of the lake sediment samples. Rock samples collected from Nacharam lake showed 9.2 ppm of uranium and 68 ppm of thorium, indicating that high uranium and thorium concentrations derived from the surrounding rocks., Editor's note: Though the majority of information presented in the Journal is based on situations within the United States, environmental health and protection know no boundaries. The Journal will periodically [...]

Most of the sediment components that accumulated in Elk Lake, northwestern Minnesota, during the Holocene are autochthonous or biogenic, delivered to the sediment-water interface on a seasonal schedule, preserved in distinct annual laminae (varves). The main allochthonous component is detrital clastic material, as measured by bulk-sediment concentrations of aluminum, sodium, potassium, titanium, and quartz, that enters the lake mostly as eolian dust. The eolian clastic influx to Elk Lake was considerably greater during the mid-Holocene (8-4 ka) than it has been for the past 4000 yr, when periods of increased eolian activity correspond to the time of the Little Ice Age and the dust bowl. Geochemical records of eolian activity exhibit distinct cyclicities with dominant periodicities of 400 and 84 yr.

A replicated survey design of four remote but adjacent lakes in Black Forest, Germany, was used to trace historical trends in polychlorinated dibenzo-p-dioxins and dibenzofurans. PCDD/F were not recent contaminants, as evidenced by sizable amounts of the compounds in the sediments of one lake before the production of chlorophenols in the 1920s. Fossil fuels burned since industrialization are postulated to be a chief source of the contaminants. PCDD/F levels in sediments increased in the 1930s in one site and in the 1960s at three others. Waste incineration, combustion of fossil fuels and metal processing were identified as sources of the contaminants.

The distribution and concentration of polychlorinated biphenyls (PCB) in Arctic and midlatitude Canadian terrestrial sites were analyzed by utilizing sediment core samples from nine lakes Canadian and Artic lakes. Samples from the Amituk and Ste Therese Lakes of Canada exhibited high sedimentation rates. The total concentrations of PCB was detected in sediments samples from the high Arctic lakes compared to sediment samples from the sub-Arctic lakes.

Natural sediment particles and macroporous polymer spheres exhibit similar proton binding, which is dependent on a combination of diffusivity, Donnan equilibrium and surface sites. This was gleaned from the examination of proton binding titrations of two sediments from Hamilton Harbour at Lake Ontario, Canada, using a model based on simple diffusion. Findings show that one-third to one-half of the binding capacity resembles diffusion into a Donnan domain, while the rest takes place on ampholyte sites such as iron oxide or silicate surfaces.

The sources of lead (Pb) pollution in Loch Lomond, Scotland, were determined by measuring lead concentration in the lake sediments to provide stable lead isotope data from the 1920s to the present. There were significant declines in lead concentration and lead isotope ratio from 1929 to 1991. In contrast to this observation, there was significant deposition of lead from the urban and industrial areas from the 1920s to the 1950s. It is suggested that the introduction of unleaded petrol in 1920 contributed in reducing Pb sources in the atmosphere. The early deposition of Pb is attributed to Pb produced in past human activities.

The transport of polycyclic aromatic hydrocarbons (PAHs) from the emissions from urban areas around Chicago, IL< and Gary, IN, to Lake Michigan was investigated by measuring the concentration of PAHs in the lake sediments. High concentrations of PAHs from the same location were found, particularly phenanthrene, benzo[b+k]fluoranthane, benzo[a]-pyrene and perylene. The accumulation of these compounds in lake sediments was attributed to historical coal use in IllINNis and extensive steel production in IllINNis and Gary, IN, as a result of in-lake integration processes.

Deposition of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in a small rural lake were investigated by measuring the concentrations of PCBs and PAHs in lake sediments. High concentrations of PAHs were detected in sediments collected from the same location, suggesting the absence of recycling in the sediments. In contrast, there were significantly high depositional fluxes for phenanthrene and PCBs, suggesting recycling between the sediments and waters. The deposition of PAHS was influenced by the seasons, with high fluxes in the winter.

Analyses of lead (Pb) concentrations and Pb isotope ratios in sediments of Lake Zug, Switzerland, using inductively coupled plasma mass spectrometry revealed significant decreases in Pb concentrations and Pb isotope ratios in the sediment. Comparison with the Pb concentrations and Pb isotope ratios in sediments of Lake Baldegg revealed slightly higher Pb concentrations in Lake Zug. Both lakes had similar Pb isotope ratios. The reductions in Pb concentrations and Pb isotope ratios in sediments of Lake Zug were attributed to decreased Pb emissions from gasoline.

Nutrient dynamics in lake systems are influenced by the loading of sediment-associated phosphorus (P) from both internal and external sources. Despite efforts to control lake productivity through reductions in external P loading, water quality problems persist in some lakes due to high internal loading of P from bottom sediment. The present study examines the spatial distribution of chemically defined P forms (N[H.sub.4]Cl-RP, BD-RP, NaOH-RP, HCI-RP, and NaO[H.sub.(85)]-RP) in bottom sediments of two noncalcareous Canadian Shield Lakes. Sediment P data are related to some of the physical and chemical variables that control internal P loading in lakes. The BD-RP and NaOH-RP forms are related to water depth and nonresidual iron and aluminum content of sediment. Approximately 80% of the total extractable P in the Muldrew Lakes sediment was bioavailable P (N[H.sub.4]Co-RP + BD - RP + NaOH - RP), which is about twice that reported in the literature for calcareous lakes. In order to model P cycling in the Muldrew Lakes, further research is required to determine the internal supply of P from the lakes' sediments and potential anthropogenic inputs alp from private sewage disposal systems.

The relationships between lake water total phosphorus, total organic carbon and pH and the near-infrared reflectance (NIR) spectra of lake sediments were evaluated to determine if NIR spectroscopy can be used as an effective technique for environmental monitoring. The results showed a large variance in the results obtained by the models. It was suggested that models should be further improved to reflect accurately lake water chemistry.

H nuclear magnetic resonance and mass spectrometries were used to characterize the structures of a hexachlorobornane and a heptachlorobornane from the sediment of two lakes in Alberta, Canada. They were both treated by toxaphene as a pesticide in the early 1960s. Slices from lake sediments dating to the early 1960s showed the highest toxaphene concentrations. The chromatographic pattern in these slices resemble that of the toxaphene standard. More recent slices showed a significant reduction in the number of chlorinated bornane peaks.

Well-dated lacustrine deposits in northern White Rock Canyon, New Mexico, record damming of the Rio Grande by at least four separate failures of a slump complex between about 17.5 and 12.4 ka (14C), linking mass movements to a period of rapid climate change in the western United States. Failure of metastable slumps probably resulted from removal of lateral support during down-cutting and erosion by the Rio Grande and from a decrease in resisting forces due to increased pore pressures. Our chronology suggests that the lake that formed between 17.5 and 15.0 ka may record effects of both glacial melt and pluvial activity (mainly enhanced rainfall); the youngest lake ([approximately]12.4 ka) may record pluvial runoff; and the intermediate lakes (13.7 to 13.1 ka) may record pluvial and minor melt-water activity. We have not found lacustrine deposits younger than about 12.4 ka. The record of geomorphic response along the Rio Grande suggests that late Pleistocene climatic changes may have triggered similar mass movements elsewhere in the Southwest.

Sediment cores from the Upper Mystic Lake, along with historical documents of industrial activity, were analyzed to trace the history of waterborne export of toxic metals from the Aberjona Watershed, north of Boston, MA. High metals concentrations are in two zones in the sediments of the lake. The zone with a depth of between 50 and 70 cm. is linked to the early 1900s when industrial activity was at its peak and chemical and leather industries directly discharged metals to the waters. Concentrations decreased as industry floundered after the mid-1930s. The remobilization of wastes from the watershed decades earlier resulted in metals transport to the lake in the 1960s.

A study has been conducted to assess the accumulation and diagenesis of selected hydrophobic organic compounds (HOC) in five Lake Ontario sediments cores taken in 1990-1991 through lead dating. The lead profiles showed significant variability among cores, suggesting that particles are mixed and distributed evenly in sediments in the lake basins. They also indicated intraspecific variation in each basin.

Rainbow trout samples and cored sediments collected from prairie lakes treated with toxaphene as pesticide in the early 1960s showed high concentrations of hepta-, octa- and nonachlorobornanes. Negative ion mass spectrometry of the sediments showed hexa- and heptachlorobornanes at levels higher than normal. These suggests that the toxaphene mixture may have been dechlorinated and redistributed by porewater diffusion. Likewise, the chromatographic patterns of the fish showed the same dechlorinated material found in the sediments. These results indicate that toxaphenes used during the 1960s still persist in the lakes.

The timing of changes in the stage and salinity of Double Lakes of Lynn County, Texas, was estimated using dissolved-chloride profiles across an underlying shale layer. Lake conditions over the past 30 to 50 ka can be inferred from the chloride profiles by using the advective velocity of the pore water through the shale and an appropriate coefficient of molecular diffusion. The profiles suggest that net-evaporative conditions existed over the southern High Plains for the past 50 ka; a period of increasing salinity in the lake began at [approximately] 20 ka and reached current levels at [approximately] 5 ka. In addition, deflationary conditions were present for at least 4 ka, and likely began or were accelerated during the most recent altithermal period at [approximately] 5 ka. This type of lake-brine record may also exist in many other saline lake environments throughout the Great Plains of North America.

The ability of the sequential filtration method to separate a sediment suspension into the desired size fractions was evaluated. The results showed that the method yields inaccurate fractionation of primary inorganic sediment since filters retain sediment particles both less than and greater than the desired sediment size. The sequential nature of the method further magnifies the error for successively smaller size fractions.

A suite of sediment core samples was recovered from two lakes, Crowfoot and Bow lakes, that are adjacent to the Crowfoot moraine type locality, to identify and radiocarbon date sediments related to the Crowfoot advance. The Crowfoot moraine system, widely recognized throughout northwestern North America, represents a glacial advance that is post-Wisconsin and pre-Mazama tephra in age. An interval of inorganic sediments bracketed by accelerator mass spectrometry radiocarbon ages of ca. 11,330 and 10,100 14C yr B.P. is associated with the Crowfoot moraine. The Crowfoot advance is therefore approximately synchronous with the European Younger Dryas cold event (ca. 11,000-10,000 14C yr B.P.). Furthermore, the termination of the Crowfoot advance also appears to have been abrupt. These findings illustrate that the climatic change responsible for the European Younger Dryas event extended beyond the northern Atlantic basin and western Europe. Equilibrium-line altitude (ELA) depressions associated with the Crowfoot advance are similar to those determined for the Little Ice Age advance, whereas Younger Dryas ELA depressions in Europe significantly exceed Little Ice Age ELA depressions.

Seismic-reflection data and historical accounts suggest that a large submarine slump in the Dead Sea was produced by the most recent large earthquake along the Dead Sea-Jordan transform plate boundary, the M(sub L) 6.25 Jericho earthquake of July 11, 1927. The correlation supports the use of seismically triggered slump, landslide, and other sediment failures in lakes to infer the timing of paleoearthquakes. Furthermore, the location of the submarine slump adds to evidence that the 1927 earthquake was caused by rupture on a fault segment beneath the north basin of the Dead Sea. This fault rupture implies that the strain accumulation on the Jordan fault north of the Dead Sea is higher than previously recognized. Older seismically triggered slumps buried beneath the 1927 slump show that a record of ancient Jericho earthquakes can also be found in the sedimentary record. The estimated number and age range of these slumps suggest a long average earthquake recurrence time.

The reaction kinetics and products of disperse dyes in anoxic sediments were investigated, with particular emphasis on anthraquinone dyes and their reaction products. Nonionic disperse dyes are of great environmental interest because they are the most heavily used dyes in the textile industry. The results showed different half-lives and products for 1-substituted anthraquinones, monosubstituted 1-amino and methylamino compounds, 1,4-diaminoanthraquinone and 1,4-diamino-2-methoxyanthraquinone.

Density separation and a number of chemical extraction techniques to extract pyrite and associated trace metals from sediments having high organic matter content were investigated. Sedimentary pyrite as well as acid volatile sulfides (AVS) have gained attention as important sinks for trace metals of toxicological or geochemical interest. The success of two methods for determining trace metal concentrations associated with pyrite in high organic carbon sediments and measurements of trace metals associated with AVS are discussed. The importance of pyrite fractions and AVS as pools of trace metals in three Canadian Shield lake sediments are estimated.

Tissue culture assay high-performance liquid chromatography and gas chromatography-mass spectrometry were employed to prove the presence of tetrodotoxin (TTX) in sediment derived from Lake Suwa, Japan. A total of 17 TTX synthesizing bacteria from five genera were isolated from Lake Suwa and Pond Inokasira. TTX and TTX-synthesizing bacteria are also present in freshwater locations.