Matter In Lake Sediments Research Articles

Inferring paleotemperature from the D/ H ratio of lacustrine organic matter

Linking the D/ H ( δD) records of the kerogen from bulk organic matter in lake sediments to known temperature– δD of precipitation relationships may offer new possibilities in paleoclimate studies. Here, we examine the hydrogen isotope ratio obtained from a radiocarbon-dated lake core from Wisconsin situated in the Midwestern part of the United States, to infer paleo-surface temperatures. Paleotemperatures were estimated by converting the δD values of the organic fraction to the δD values of the lake water and by implication to that of local precipitation. The temperature estimates show that the middle Holocene from 7000 to 5000 years before present (BP) was warmer by about 3 °C, in general agreement with speleothem data from the Midwestern United States. Our study shows the usefulness of the D/ H rations of kerogen from bulk sediment as a climate proxy that can compliment compound specific hydrogen isotope studies.

In situ adsorption of mercury, methylmercury and other elements by iron oxyhydroxides and organic matter in lake sediments

Samples of authigenic material, sediment overlying water and oxic surface sediment (0–0.5-cm depth) from a perennially oxygenated lacustrine basin were analysed to investigate which solid phases are important for binding a suite of trace elements (Ag, As, Ca, Cd, Cu, Hg, In, methylmercury (MeHg), Mg, Mo, Pb, Sb and Zn). The authigenic material, which was collected with inert Teflon sheets deployed for several years across the sediment–water interface, contained mainly poorly crystallized Fe oxyhydroxides and natural organic matter, presumably humic substances derived from the watershed. Manganese oxyhydroxides were not present in the collected authigenic material due to the slightly acidic condition (pH = 5.6) of the lake that prevents the formation and recycling of these compounds. Conditional equilibrium constants for the adsorption of cationic (KFe–M) and anionic (KFe–A) trace elements onto the authigenic Fe oxyhydroxides were estimated from their concentrations in the authigenic material and in bottom water samples. These field-derived values of KFe–M and KFe–A were compared with those predicted by the surface complexation model, using laboratory-derived intrinsic adsorption constants and the water composition at the study site. Equilibrium constants (KPOM–M) were also calculated for the adsorption of the cationic trace elements onto the humic substances contained in the diagenetic material. The field-derived values of KPOM–M were compared to those predicted by the speciation code WHAM 6 for the complexation of the trace elements by dissolved humic substances in the lake. Combining the results of the present study with those on the distributions of trace elements in the porewater and solid-phase sediments reported in previous studies at the same site, it was determined whether the trace elements bind preferentially to Fe oxyhydroxides or natural organic matter in oxic sediments. The main inferences are that the anionic trace elements As, Mo and Sb, as well as the cationic metal Pb are preferentially bound to the authigenic Fe oxyhydroxides whereas the other trace elements, and especially Hg and MeHg, are preferentially bound to the humic substances.

Late Holocene paleoenvironmental changes in subtropical Taiwan inferred from pollen and diatoms in lake sediments

We analyzed pollen, spores, diatoms, organic carbon, nitrogen, and δ13C of organic matter in lake sediments to infer climate changes and reconstruct the paleo-environment of subtropical Taiwan over the past ∼1300 years. A 31.5-cm sediment core that represents deposition from 650 AD to present was taken from a mountain lake, Duck Pond, located 760 m a.s.l. We differentiated five zones using cluster analysis on pollen and spore assemblages. Fluctuations in the relative abundances of arboreal taxa, herbaceous plants, and ferns reflect changes in the relative amounts of woody versus grassland vegetation. Such shifts are associated with changes in temperature and humidity and are consistent with climatic periods reported for the temperate region of central China. Climate changes inferred from the pollen assemblages are also correlated well with changes in the ratios of fern spores to pollen, with organic carbon to nitrogen, and with the δ13C values in the sediments. Fluctuations in these data throughout the entire core were in good agreement with the changes in pH inferred from diatom assemblages. This study provides evidence of climate change in northern Taiwan over the past 1.3 millennia, assuming that climate can be inferred from the ratio of arboreal to non-arboreal pollen and from the pH of the aquatic environment.

Holocene glaciation and climate evolution of Baffin Island, Arctic Canada

Lake sediment cores and cosmogenic exposure (CE) dates constrain the pattern of deglaciation and evolution of climate across Baffin Island since the last glacial maximum (LGM). CE dating of erratics demonstrates that the northeastern coastal lowlands became ice-free ca.14 ka as the Laurentide Ice Sheet (LIS) receded from its LGM margin on the continental shelf. Coastal lakes in southeastern Baffin Island started to accumulate sediment at this time, whereas initial lacustrine sedimentation was delayed by two millennia in the north. Reduced organic matter in lake sediment deposited during the Younger Dryas chron, and the lack of a glacial readvance at that time suggest cold summers and reduced snowfall. Ice retreated rapidly after 11 ka but was interrupted by a widespread readvance of both the LIS and local mountain glaciers ∼9.6 ka (Cockburn Substage). A second readvance occurred just before 8 ka during a period of unusually cold summers, corresponding to the 8.2 ka cold event in the Greenland Ice Sheet. Most local glaciers were behind their present margins before 7 ka, and in some instances much earlier, although the Foxe Dome of the LIS continued to slowly retract toward the present day Barnes Ice Cap throughout the Holocene. Pollen in lake sediments is rare and dominated by exotic sources prior to 12 ka. Subsequently, grass tundra became established, followed by modern tundra vegetation ca. 8 ka, with subtle changes in pollen assemblages in the late Holocene. Lake primary productivity peaked in the early Holocene, before terrestrial vegetation or marine surface waters reached their apparent thermal maxima. Lacustrine, marine, and glacial proxies all reflect significant late Holocene cooling. The onset of Neoglaciation is well dated in lacustrine records at ca. 6 ka, with intensification after 2.5 ka. The expansion of local glaciers during the Little Ice Age represents the most extensive advance since 7 ka. We suggest that the replacement of Atlantic surface waters by cold, low-salinity Arctic Ocean water, coupled with the steady reduction of summer insolation, resulted in a significant positive sea-ice feedback that produced a larger late Holocene summer temperature depression over the Baffin region than in the Pacific sector of the Arctic.

Biogeochemistry as an Indicator of Organic Matter Sources, Paleolimnological and Paleoenvironmental Changes in Lacustrine Sediments—A Study of Two Himalayan Lakes

Biota living in lakes and their watersheds are the sources of organic compounds for lake sediments. Much of the organic matter contained in sediments has undergone microbial reprocessing. Nevertheless, organic matter in lake sediments can retain source information and thereby contribute to the paleolimnological record. In sediment cores from Mansar and Surinsar lakes of Lesser Himalaya, Jammu, C/N ratios and 13C values suggest that the primary source of organic carbon was vascular land plants. Low total nitrogen contents, low amino acid/amino sugar ratios, low amino acid carbon and nitrogen contents, and low 15N values, the latter in Mansar lake, suggest terrigenous organic matter higher in lignin or carbohydrate contents and biodegradation in bottom sediments. The higher 15N values in Surinsar lake indicates more autochthonous contribution of organic content. Variations in the organic carbon and total nitrogen contents in the cores are related to grain size, inorganic carbonate, and degradation at the bottom levels. The 210Pb data of the core fractions of these lakes show variation in the rate of sedimentation in Mansar lake, that is, 8.2 mm/yr in the northern and 4.5 mm/yr in the southern flank, whereas in Surinsar lake, it is 7.2 mm/yr, which indicates variation in sedimentation/erosion in the lake basins.

Modern Climatic Signals Recorded in Xincuo Lake Sediments in Zoige Basin, Eastern Tibetan Plateau, China

依据湖泊沉积记录进行古气候环境要素定量复原是过去全球变化研究的重要内容.本文通过若尔盖盆地兴措湖近代湖泊沉积特征、沉积物总有机碳及其同位素指标分析,并与器测气象资料进行比较,对兴措湖近代湖泊沉积物中有机碳及其同位素指标所代表的气候环境信息进行了定量研究.在此基础上,建立了兴措湖沉积物总有机碳及其同位素记录与对应的降水和气温间的函数关系.为定量恢复该区长尺度历史时期古气候环境特征提供了基础.;Climatic proxy of stable carbon isotope, together with total organic carbon content, in organic matter in lake sediment is one of the most effective methods to reconstruct past climatic evolutionary sequences. By coupling the indexes of TOC and δ¹³C_org in Xingcuo lake sediments and instrumental meteorological data in Zoige Basin, Eastern Tibetan Plateau and by building relative function relations among them, we probed quantitatively modern climatic signals recorded in those indexes. The results showed that there were remarkable relations between contents of TOC and precipitation, δ¹³C_org and air temperature, of which coefficence reaches to-0.67 and -0,75, respectively. Besides, we also demonstrated that average variation between contents of TOC and precipitation (dTC/dP) is -0.046%·mm^-1 and -0.84‰·℃^-1 for δ¹³C_org and air temperature (dδC/dT). According to the above, relative function relations among them were built.

Humus and phosphorus composition of 3 lake sediments in Yamaguchi M Prefecture

Abstract Most of the organic matter in lake sediments, as in soils, consists of heterogeneous and colored polymers collectively known as humic substances. It is considered that these substances play a major role in the geochemical cycle of carbon in lakes (Ishiwatari 1985). Humic substances can be divided into humic acid, fulvic acid, and humin fractions. Ishiwatari (1985) reported the distribution and optical properties of fractions extracted from 9 lake sediments. On the other hand, although phosphorus is an essential element for plant growth in lakes, phosphorus is often the main factor causing eutrophication (Vollenweider 1976). The release of phosphorus from lake sediments may be responsible for eutrophication, and may be related to the forms of phosphorus present. Some reports on the phosphorus composition of lake sediments have been published (Hosomi and Sudo 1979; Nakajima et al. 1979; Hurumai and Ohgaki 1982; Joh 1983).

Early diagenesis of organic matter in lake sediments: a stable carbon isotope study of pore waters

The isotopic composition of organic carbon ( δ 13C) in the upper 8 cm of sediment in Mohonk Lake, a freshwater lake in New York State, U.S.A., was measured to be −27 ± 1‰ (relative to PDB) with a slight trend toward enrichment of 13C down the sediment column. No palaeoenvironmental signal can be inferred from these data due to largescale seasonal changes in the PT of autochthonous organic carbon. The sediment pore waters were analyzed for dissolved inorganic carbon (DIC), the isotopic composition of the DIC ( δ 13C DIC) and total alkalinity (ΣAlk). The depth profiles reveal steep gradients in each of these species in both the shallow (littoral zone) and deep sediments. ΣAlk and DIC increased by a factor of three from bottom water concentrations to 5 cm below the sediment-water interface and δ 13C DIC increased by ∼ 20‰ at 8-cm depth. ΣAlk and DIC concentrations in the littoral sediments also increased by a factor of 5 by 10-cm depth with a δ 13C DIC increase of + 15%o to that depth. The positive enrichment in 13C must be due to methane fermentation which produces as a by-product CO 2 that is 13C enriched. A mass-balance calculation showed that ∼66% of DIC produced within the deep sediments and 55% within the littoral sediments was from CO 2 generated via methanogenesis plus methane oxidation. The ratio of breakdown rate of organic matter to sedimentation rate calculated from a diagenetic model of the carbonate species was 0.8 and 0.25 cm −1 for the deep and littoral sediments, respectively. Simple diagenetic models fitted to the dissolved carbonate species do not reproduce the observed carbon-isotope profiles. 13C-poor DIC derived from anaerobic oxidation of methane is proposed as the likely cause of the lower than expected δ 13C-values.

Decomposition of organic matter in lake sediments

Analyse de la diminution de concentration avec la profondeur du carbone, de l'azote et du phosphore, dans les sediments de 64 lacs, reservoirs et estuaires aux Etats-Unis

Characteristics of insoluble organic matter in lake sediments as revealed by alkaline potassium permanganate oxidation

Characteristics of insoluble organic matter in lake sediments as revealed by alkaline potassium permanganate oxidation

Changes in spruce composition following burial in lake sediments for 10,000 yr

Organic matter in lake sediments is a mixture of biological materials from a number of modern sources plus variable amounts of recycled detrital material. Hence, it is usually difficult to distinguish input variations over time from the diagenesis of organic matter. Comparison of old material of known biological origin with younger material helps resolve this problem. We have compared the compositions of wood and needles from a modern white spruce (Picea glauca) with those from a white spruce buried for 10,000 yr in a lake bottom. Although the tissues are structurally well preserved, some chemical changes are evident in the old samples. Total fatty acid concentrations decrease by over 90%. Sterol and hydrocarbon concentrations are similar in the modern and 10,000-yr-old wood, but the concentration of sterols is lower in the old needles. Cellulose components in the wood have decreased relative to lignin components, although both types of materials remain in high concentration in comparison to other organic components.

Field measurements of ingestion and assimilation for the Australian brine shrimp Parartemia zietziana Sayce (Crustacea: Anostraca)

AbstractIngestion and assimilation of the brine shrimp Parartemia zietziana were measured in the field. Populations in Pink Lake and Lake Cundare were used; both lakes are shallow (< 1 m), saline (> 60°/00), and located in western Victoria; they have tow primary production. P. zietziana relies largely on organic matter in lake sediment for food. Ingestion rate was measured in situ in Pink by following the uptake of 14C from labelled sediment. The rate of faecal pellet production was measured (in both lakes) by allowing animals to defaecate for 24 h in a net suspended in the lake. Ingestion rate varied from 0.35 to 13 01 × 10–1 mg dry wt h‐1 individual‐1 for a range in dry weight of shrimp from 0.2 to 2.3 mg individual‐1; for a similar range in weight, defaecation varied from 0.08 to 2.03 × 10‐1mg dry wt h‐1 individual‐1. These rates were converted to joules and assimilation efficiencies of 30–60% calculated. Regressions showed that change in dry weight of shrimp accounted for > 90% of the variance in both rates.

Vertical profile of microbiological decomposition rate for organic matter in lake sediments from the viewpoint of methane fermentation.

Core samples were collected from Lake Suwa and Lake Kizaki in Nagano Prefecture, Japan. They were divided into several pieces at 2 or 15cm intervals. Each of them was taken in a soil injector and incubated at 26-27°C for about 40 days. The production of CH4 in the surface sediments amounts to about 200ml/100g of dry sediment and markedly decreases toward 20cm core depth to about 20ml/100g. In sediments deeper than 20cm, the production of CH4 gradually decreases to nearly zero at a depth of about 60cm. The vertical profile of the CH4 production is similar to those of various organic components. The methane production in the core samples from 50 to 100cm, mixed with sodium acetate corresponds to about 70% of what is theoretically expected from the amount of sodium acetate added. For samples from 100 to 140cm, however, it decreases on a straight line to zero. This seems to reveal that the decrease in CH4 production for deeper parts of the core samples is not only caused by the decrease in the substrates for methane fermentation but also by the decrease in microbiological activities for methane fermentation resulting in gradual disappearance from 100cm toward 140cm core depth.