The sedimentary record of spheroidal carbonaceous fly-ash particles in shallow Danish lakes

Spheroidal carbonaceous particles (SCP) from combustion of oil and coal have been quantified in cores from top sediments of Danish shallow lakes. Chronologies were provided by ²¹⁰Pb-dating supplemented by measurements of other radionuclides (¹³⁷Cs, ¹³⁴Cs, ²⁴¹Am). All cores show indications of sediment mixing but most still retain a characteristic SCP record. Deposition rates of SCP were low until the 1920s, increased strongly after World War II, reached maximum levels around 1970 and decreased thereafter. These results were used to infer a new chronology for a sediment core from a shallow lake, from which a ²¹⁰Pb chronology had previously been published.SCP inventories are positively correlated with ²¹⁰Pb inventories and dry matter accumulated since 1900, suggesting that absolute SCP accumulation rates may be more influenced by sedimentary processes than by atmospheric fluxes. The concentrations of SCP in surface sediments of the six lakes do, however, correlate with regional SO₂ emissions.     

A method for the extraction of carbonaceous particles from lake sediment

The methods found in the literature for the extraction of carbonaceous particles from lake sediment are discussed. The technique used by Griffin & Goldberg (1975) on Lake Michigan sediments was improved by modifying the procedure to halve the extraction time and reduce the risk of fragmentation. This method was then applied to a sediment core taken from Loch Tinker in Western Scotland, which had previously been analysed using the Renberg & Wik method. Although the basic trends for both methods are the same, the new method is found to be more sensitive to low particle numbers and more accurate, due to a more efficient extraction and a higher magnification for microscope counting.     

Interpretation of210Pb profiles and verification of the CRS dating model in PIRLA project lake sediment cores

This paper reports results and analysis of²¹⁰Pb-activity measurements in 51 lake-sediment cores from 32 lakes in the four PIRLA (Paleoecological Investigations of Recent Lake Acidification) project regions (Adirondack Mountains [New York], Northern New England, Northern Florida, and the Northern Great Lakes States). General application of the Constant Rate of Supply (Constant Flux) model for²¹⁰Pb dating is valid for lakes in the PIRLA study, although application of the model is equivocal in a few lakes.²¹⁰Pb inventories and profiles are replicable among closely spaced cores within a lake. Specific²¹⁰Pb activity in surface sediments is negatively correlated with bulk sediment accumulation rate in seepage lakes, but not in drainage lakes. Drainage lakes with lower pH have lower unsupported²¹⁰Pb inventories in sediments, but the relationship does not occur in seepage lakes.²¹⁰Pb profiles in only seven of the cores, all from either the Adirondacks or the northern Great Lakes states, exhibit exponential decay curves. Deviations from an exponential profile include a flattening of the profile in the top few cm or excursions of one or a few measurements away from an exponential curve.²¹⁰Pb dates typically agree with other chronostratigraphic markers, most of which are subject to greater uncertainty. Several hypotheses, including sediment mixing, hydrologic regime, sediment focusing, and acidification, are proposed to explain variation of²¹⁰Pb distribution among lakes and regions. Hydrologic factors exert control on unsupported²¹⁰Pb inventories in PIRLA lakes, and there is a strong focusing effect in drainage lakes but a weak focusing effect in seepage lakes.This is the third of a series of papers to be published by this journal following the 20^th anniversary of the first application of²¹⁰Pb dating of lake sediments. Dr P. G. Appleby is guest editing this series.     

Spatial uniformity of sediment accumulation in varved lake sediments in northern Sweden

As part of an investigation aimed at assessing the potential of northern Swedish varved lake sediments for fine-resolution reconstruction of past climatic conditions, the following questions were addressed; how representative is a single core, does the appearance of varves change as the sediment ages, and how can varve thickness and within-varve structures be digitized? Analyses of replicate cores from Kassjön, using sample sequences of seasonal, annual and centennial time resolution, show that spatial variability of sediment accumulation in the varved sediment is very low. Comparisons of intensity curves from image analysis of freeze cores of recent sediments from Lake Nylandssjön, sampled in 1980 and 1985, indicate that the varves acquire their appearance at the sediment-water interface during sedimentation and that the varve structures are preserved during diagenetic processes. Measurement of varve thicknesses with a tree-ring microscope and with image analysis gave similar results. However, with image analysis, within-varve structures such as colour variations and thicknesses of seasonal layers, can also be recorded, increasing the possibilities for palaeolimnological and palaeoclimatic inferences.     

Decoding post-orogenic sediment recycling and dispersal using detrital zircon core and rim ages

Detrital zircon (DZ) geochronology has become a popular tool in provenance studies during the past two decades. However, similar zircon crystallization ages from different source regions greatly hamper the interpretation of sediment dispersal and recycling processes. The Alleghenian–Ouachita–Marathon (AOM) foreland and vicinity in North America is a region where some dominant DZ age groups could come from both the southern Appalachians in the eastern United States and the Gondwanan terranes in Mexico. In this study, we present 1045 new DZ U–Pb ages and 81 DZ core–rim age pairs in lower Permian sandstone in the Permian Basin and Miocene sandstone in the eastern Gulf of Mexico (GOM). These new data were integrated with published DZ single U–Pb age and core–rim ages from syn- to post-orogenic strata in the Permian Basin, Marathon foldbelt, southern Appalachian foreland basin and eastern GOM to interpret the sediment-dispersal models in the AOM foreland and eastern GOM. Our models show that during the Leonardian Stage, sediments derived from the Appalachians were first delivered to the US midcontinent and then recycled to the Permian Basin; during the Miocene, sediment from the Appalachians fluxed to the eastern GOM, with no longshore mixing from the western GOM. These models based on the integration of single U–Pb and core–rim ages are consistent with published results that used other methods, including zircon single U–Pb age, zircon Hf isotopic data, zircon (U–Th)/He age, sedimentology and stratigraphy. Our results demonstrate that although some limitations exist, zircon core–rim age is a powerful tool, adding an extra constraint on the interpretation of sediment-dispersal systems. This tool is particularly applicable to the post-orogenic stage, during which the sediment pathways are more complicated because of the dominant input from distal sources. Insights gained in this study imply that this novel strategy of using core and rim ages could be integrated with other methods to better understand sediment dispersal.     

1950-2008年黄河入海水沙变化(英文)

Based on hydrological data observed at Lijin gauging station from 1950 to 2008, the temporal changes of water discharge and sediment load of the Yellow River into the sea were analyzed by the wavelet analysis, and their impacts on the estuary were investigated in different periods based on the measured coastline and bathymetry data. The results show that: (1) there were three significant periodicities, i.e. annual (0.5-1.0-year), internnual (3.0-6.5-year) and decadal (10.1-14.2-year), in the variations of w...     

Assessment of drought over the past two millennia using near-shore sediment cores from a Canadian boreal lake

Lack of long-term studies on drought in the boreal region of northwest Ontario limits our ability to assess the vulnerability of this region to climate change. We investigated changes in diatoms, scaled chrysophytes, and sedimentary pigments in two near-shore cores from Gall Lake to infer limnological and water-level changes over the last two millennia. The two coring locations, at modern water depths of 7.5 and 11.5 m, were selected to contrast inferences for past lake level based on distance from the modern water-depth boundary between predominantly benthic and planktonic diatom assemblages in surface sediments (6.0 m). Diatom-inferred depth inferences were more variable in the core from 7.5-m water depth, consistent with the hypothesis that the greatest changes occurred at water depths closest to the benthic:planktonic boundary. Both sites revealed a pronounced drought from ~AD 950 to 1300, synchronous with the medieval climate anomaly (MCA). This finding suggests a northeast expansion of the arid MCA into northwest Ontario, extending the known spatial extent of this megadrought. Scaled chrysophytes and sedimentary pigments suggest a recent increase in thermal stratification. Our findings indicate this region is more susceptible to changes in moisture than was previously suspected based on the instrumental record for the past century.     

Magnetic susceptibility in sediment records of Lake Ådran,eastern Sweden: correlation among cores and interpretation

Magnetic susceptibility was used to test the representativity of the lithostratigraphy of a master sediment sequence from Lake Ådran, eastern Sweden. Five further sediment cores from the same lake were correlated and compared with the master sequence using magnetic susceptibility records. Mineral magnetic correlations are generally based on matching prominent susceptibility features but may be significantly improved by using slot sequence analyses. The result of these analyses show that the sediment in the Lake Ådran master sequence can be considered representative for the basin. The variations in the magnetic susceptibility in relation to pollen and diatom analyses also seem to reflect water level changes and shore displacement in the Baltic between 9900 ¹⁴C years B.P. and the isolation at 5900 ¹⁴C years B.P. The first emergence of scattered non-vegetated islands is characterised by high susceptibility values. Along with a continuous water lowering and the development of the vegetation during the Ancylus fresh water stage, susceptibility values gradually decrease. A rapid phase of the Ancylus regression between 9200 and 9000 ¹⁴C years B.P. is seen as an increase in magnetic susceptibility. During the following Baltic brackish water stage, the Litorina stage, susceptibility values are at their lowest, followed by higher values at the isolation from the Baltic with a maximum around 5000 ¹⁴C years B.P.Shore displacement between 9900 and 5900 ¹⁴C years B.P. is discussed based on the magnetic susceptibility measurements and their relationship to the pollen and diatom analyses.     

Field calibration and performance of sediment traps in a eutrophic holomictic lake

In wind-stressed and unstratified Lough Neagh low aspect ratio sediment traps, which allow for internal resuspension, collected sediment at a rate close to the natural sediment accumulation rate inferred from dated sediment cores. High aspect ratio traps grossly overestimated the natural rate of sediment accumulation as did, but to a lesser extent, burial rate measurements on an artificial stratigraphic marker. The former type of trap deployed over long exposure periods is therefore recommended as providing the best estimate of net downward particle flux in lakes such as Lough Neagh. However, it is emphasized that all sediment trap types, when operated in shallow turbulent lakes, will to a greater or lesser extent be contaminated by secondary or redeposited material and so will not provide a direct measure of primary sedimentation. Use of tube traps in lakes such as Lough Neagh should not, however, be discounted since they can provide a record of the quality of sedimenting material through time.     

Reconstructing lake and drainage basin history using terrestrial sediment layers: analysis of cores from a post-glacial lake in New England, USA

Four sediment cores and twenty-five ¹⁴C ages from Ritterbush Pond in northern Vermont provide a detailed and continuous temporal record of Holocene lake and watershed dynamics. Using visual logs, carbon content, magnetic susceptibility, stable isotope signatures, and X-radiography, all measured at 1-cm scale, we identify and date discrete layers of terrestrially-derived sediment in the organic-rich, lacustrine gyttja. These inorganic layers range in thickness from <1 mm to >10 cm and range in grain size and sorting from homogeneous silt to graded sand. AMS radiocarbon ages both from macrofossils within the thickest layers, and gyttja bracketing these layers, provide the basis for correlation among the cores, the dating of 52 basin-wide sedimentation events, and the development of a detailed sedimentation chronology for the Holocene.Physical, chemical, and isotopic analyses suggest the inorganic layers are terrestrially derived and result from hydrologic events large enough to erode and transport sediment from the watershed into the pond. The temporal and spatial distribution of the inorganic layers suggests changing basin-wide sedimentation and thus erosion dynamics since deglaciation over 12,000 years ago. Specifically, for intervals lasting 400 to 1000 years, during the early (>8600 cal yBP), middle (6400 to 6800 cal yBP) and late Holocene (1800 to 2600 cal yBP), the Ritterbush Pond watershed eroded more rapidly than at other times and terrestrially derived material poured into the pond. Analysis of Ritterbush Pond sediments demonstrates the potential for North American lakes to preserve a record of drainage basin dynamics.     

Historical trends of mercury and spheroidal carbonaceous particle deposition in sub-alpine lakes in the Great Basin,United States

The geochemistry of lake sediments was used to identify anthropogenic factors influencing aquatic ecosystems of sub-alpine lakes in the western United States during the past century. Sediment cores were recovered from six high-elevation lakes in the central Great Basin of the United States. The proxies utilized to examine the degree of recent anthropogenic environmental change include spheroidal carbonaceous particle (SCP), mercury (Hg), and sediment organic content estimated using loss-on-ignition. Chronologies for the sediment cores, developed using ²¹⁰Pb, indicate the cores span the twentieth century. Mercury flux varied between lakes but all exhibited increasing fluxes during the mid-twentieth century. The mean ratio of modern (post-A.D. 1985) to preindustrial (pre-A.D. 1880) Hg flux was 5.2, which is comparable to the results from previous studies conducted in western North America. Peak SCP flux for all lakes occurred between approximately A.D. 1940 and A.D. 1970, after which time the SCP flux was greatly reduced. The reduction in SCP input is likely due to better controls on combustion sources. Measured Hg concentrations and calculated sedimentation rates suggest atmospheric Hg flux increased in the early 1900s, from A.D. 1920 to A.D. 1990, and at present. Atmospheric deposition is the primary source of the anthropogenic inputs of Hg and SCPs to these high elevation lakes. The input of SCPs, which is largely driven by regional sources, has declined with the implementation of national pollution control regulations. Mercury deposition in the Great Basin has most likely been influenced more by regional inputs.     

Redox remobilization and the heavy metal record in lake sediments: a modelling approach

The issue of whether heavy metal concentration profiles in lake sediments are vulnerable to redox mediated post-burial alteration stubbornly refuses to go away. Such behaviour is well-known in iron and manganese, due to great contrasts in the solubility of the reduced and oxidized chemical forms. A numbers of trace elements that also exhibit more than one oxidation state in lake sediments have also been shown to undergo diffusive migration in response to redox gradients (e.g., As, Co, Cr, V). What remains unclear is whether elements like Cd, Cu, Pb and Zn, that have only one stable oxidation state in sediments, are also subject to alteration. This paper reviews existing evidence and presents a model, based on current knowledge, to constrain the likely effects. It is concluded that some migration is likely, but that this is only significant at extremely low sediment mass accumulation rates. The formulation of the model highlights the need for further information about the physical form of iron and manganese oxyhydroxides in lake sediments.     

Sediment variability and transport in the littoral area of the abandoned Yellow River Delta,northern Jiangsu

The delta evolution and erosion process of the abandoned Yellow River Delta (AYRD) have been extensively studied. However, the variation of sediment at a large littoral scale along the north coast of Jiangsu is less understood. In this study, the data of surface sediment samples obtained in the littoral area of the Yellow River Delta in 2006 and 2012 is used to study the sediment variability and sediment transport trends by using the geostatistics analysis tool and the grain size trend analysis model. In order to ensure the applicability of the model, the geostatistics method is used to determine the characteristic distance (Dc) with the average range value (Ao) of grain size parameter. Filtering method (removing data that not at a sampling station) is used to improve accuracy of data selection. The results show that sedimentary spatial correlation in Lianyun Port area and southern part of the abandoned Yellow River Delta (AS) is better than that in the northern part of the abandoned Yellow River Delta (AN). Sediment in the area is found to be anisotropy at the northeast-southeast direction. The grain size trend analysis reveals that the sediment trend is towards bayhead and southerly in the Haizhou Bay, southeasterly along the shoreline in the south Lianyun Port, northwesterly in AN and easterly-southeasterly in AS respectively. The investigation of possible relationships between Dc, Ao, sediment transport and delta evolution shows a close link between Dc and Ao of one sediment combination. It is also found that sediment transport trends could reasonably represent the delta evolution to a certain degree.     

A sediment record of trace metal loadings in the Upper Mississippi River

Sediment cores from Lake Pepin, a natural lake on the Upper Mississippi River, reveal the historical trends in trace metal use and discharge in the watershed. Lead-210 dated concentration profiles of trace metals (Ag, Cd, Cr, Cu, Hg, Pb, V, Zn) in sediment cores from throughout the lake generally showed low and stable concentrations prior to settlement (circa 1830), peak concentrations between 1940 and 1975, and substantial decreases thereafter. Whole-lake sediment accumulation rates increased greatly over the period of record, from 79,000 metric tons year⁻¹ prior to 1830, to 876,000 metric tons year⁻¹ during the 1990s. Whole-lake accumulation rates of most trace metals peaked in the 1960s but decreased sharply after that. Sediment and trace metal accumulation rates decreased in the downstream direction, and approximately two-thirds of the sediment and trace metal mass accumulated in Lake Pepin since 1800 was deposited in the upper 30% (by area) of the lake. The dramatic declines in trace metal concentrations and accumulation rates in Lake Pepin sediments since 1970 coincide with increased pollution control and prevention efforts throughout the watershed, including the implementation of secondary treatment at a large municipal wastewater treatment plant upstream. This is one of eight papers dedicated to the “Recent Environmental History of the Upper Mississippi River” published in this special issue of the Journal of Paleolimnology. D.R. Engstrom served as guest editor of the special issue.     

Sediment variability and transport in the littoral area of the abandoned Yellow River Delta,northern Jiangsu

The delta evolution and erosion process of the abandoned Yellow River Delta (AYRD) have been extensively studied. However, the variation of sediment at a large littoral scale along the north coast of Jiangsu is less understood. In this study, the data of surface sediment samples obtained in the littoral area of the Yellow River Delta in 2006 and 2012 is used to study the sediment variability and sediment transport trends by using the geostatistics analysis tool and the grain size trend analysis model. In order to ensure the applicability of the model, the geostatistics method is used to determine the characteristic distance (D _c) with the average range value (Ao) of grain size parameter. Filtering method (removing data that not at a sampling station) is used to improve accuracy of data selection. The results show that sedimentary spatial correlation in Lianyun Port area and southern part of the abandoned Yellow River Delta (AS) is better than that in the northern part of the abandoned Yellow River Delta (AN). Sediment in the area is found to be anisotropy at the northeast-southeast direction. The grain size trend analysis reveals that the sediment trend is towards bayhead and southerly in the Haizhou Bay, southeasterly along the shoreline in the south Lianyun Port, northwesterly in AN and easterly-southeasterly in AS respectively. The investigation of possible relationships between D _c, Ao, sediment transport and delta evolution shows a close link between D _c and Ao of one sediment combination. It is also found that sediment transport trends could reasonably represent the delta evolution to a certain degree.     

Acidity and organic carbon in lake water: variability and estimation of means

The demand for a single value to characterize the pH (and other chemical variables) of a lake, in order to calibrate palaeolimnological reconstructions, requires an answer to the question of whether means should be of untransformed or log data. The temporal frequency distributions of acidity and organic carbon in seven rivers and lakes (surface samples) in Norway are approximately lognormal. Thus log means describe the distributions better than untransformed means. Estimated standard deviations, which are similar for the rivers and lakes, are independent of the mean values. Restricting observations to the autumn does not result in better estimation of mean annual values.     

The role of iron and sulfur in the visual appearance of lake sediment varves

Easily discernible sediment varves (annual laminations) may be formed in temperate zone lakes, and reflect seasonal changes in the composition of the accumulating material derived from the lake and its catchment (minerogenic and organic material). The appearance of varves may also be influenced by chemical processes. We assessed the role of iron (Fe) and sulfur (S) in the appearance of varves in sediments from Lake Nylandssjön in northern Sweden. We surveyed Fe in the lake water and established whether there is internal transport of Fe within the sediment. We used a unique collection of seven stored freeze cores of varved sediment from the lake, collected from 1979 to 2004. This suite of cores made it possible to follow long-term changes in Fe and S in the sediment caused by processes that occur in the lake bottom when the sediment is ageing. We compared Fe and S concentrations using X-ray fluorescence spectroscopy (XRF) in specific years in the different cores. No diagenetic front was found in the sediment and the data do not suggest that there is substantial vertical transport of Fe and S in the sediment. We also modeled Fe and S based on thermodynamic, limnological, and sediment data from the lake. The model was limited to the five components H⁺, e^?, Fe³⁺, SO₄ ^2?, H₂CO₃ and included the formation of solid phases such as Fe(OH)₃ (amorphous), FeOOH (aged, microcrystalline), FeS and FeCO₃. Modeling showed that there are pe (redox) ranges within which either FeS or Fe(OH)₃/FeOOH is the only solid phase present and there are pe ranges within which the two solid phases co-exist, which supports the hypothesis that blackish and grey-brownish layers that occur in the varves were formed at the time of deposition. This creates new possibilities for deciphering high-temporal-resolution environmental information from varves.     

Spatial pattern of recent sediment and diatom accumulation in a small,monomictic, eutrophic lake

Spatial variability of sediment and diatom deposition was assessed in a small monomictic, eutrophic lake in Northern Ireland (Lough Augher, Co. Tyrone) using measurements from 17 sediment cores. Loss-onignition profiles in water depths >6 m showed good repeatability, while littoral cores were more variable with localised profiles. Dry mass accumulation rates, derived by biostratigraphic correlation to a ²¹⁰Pb dated master core, were variable and not correlated with water depth. Basin mean dry mass accumulation rate was 0.068 g cm^-2 yr^-1 (range 0.036–0.09) prior to 1900, and 0.19 g cm^-2 yr^-1 (range 0.11–0.3) after 1974. Post-1940 cumulative fluxes were estimated for dry mass (range 3.49–916 g cm^-2) and diatoms (range 16.9–113.8×10⁷ frustules cm^-2). Cumulative dry mass was inversely correlated (r=–0.64) with distance from the inflow, indicating its localised influence. No variable was correlated with water depth except frustules of planktonic diatoms (r=0.66). However, high cumulative fluxes of diatoms and dry mass away from the inflow suggest that the expansion of the littoral macrophyte community may be responsible for decreased resuspension in shallow water, and together with increased sediment trapping, has enhanced sediment accumulation in shallow water over recent time periods.     

Dating of the Dome Fuji shallow ice core based on a record of volcanic eruptions from AD 1260 to AD 2001

We measured the concentration of non-sea-salt sulfate () in the Dome Fuji shallow ice core (Antarctica) from the surface to 40 m depth with the aim of dating the core with reference to the record of volcanic eruptions. Three huge spikes related to large-scale volcanic eruptions were detected at depths of 12.5, 29.9, and 38.8 m, correlated to the eruptions of Tambora (AD 1815), Kuwae (AD 1452) and an unknown event (AD 1259), respectively. We identified another nine spikes related to accurately dated eruption events. The shallow ice core was dated from AD 1260 to AD 2001 based on these 12 eruption events and the assumption of constant annual snow accumulation in the periods between eruption events. The results yield a maximum correction of ∼20 years compared with the dating proposed in a previous study. The annual accumulation varied within ±∼15% of the average water equivalent value over the study period (25.5 mm).     

Rates of sediment deposition in a hypersaline lake in the northern Great Plains,western Canada

Remarkably high rates of sedimentation (up to nearly 60 kg m⁻² yr⁻¹) are documented for offshore areas of Freefight Lake, a deep, hypersaline, meromictic lake in the northern Great Plains of Canada. Most material in the offshore sediment traps consists of soluble and suparingly soluble endogenic salts. Deposition of allogenic sediment is minor. The observed high sedimentation rates are in response to several mechanism: (i) freeseout precipitation of salts from the mixolimnion; (ii) redistribution of shallow water endogenic precipitates by turbidity flows and interflow processes; and (iii) precipitation of salts from within the monimolimnion Because the bottom water mass of the lake is essentially isothermal and isochemical, large scale temperature induced remobilization of these salts at or near the sediment-water interface is unlikely. Similarly, the morphology of the basin suggests that resuspension of bottom sediment by waves in the offshore areas of the basin is negligible. Although the sedimentation rates observed in Freefight Lake are extraordinarily high and considerably greater than other modern lacustrine sedimentation rates documented in the literature to date, the observed rates are entirely compatible with suggested accumulation rates of ancient evaporite sequences. Palliser Tringle Global Change Contribution Number 6.