A low-cost gravity-style corer capable of multiple sediment recovery drives

Abstract. Hypolimnetic anoxia in eutrophic lakes can delay lake recovery to lower trophic states via the release of sediment phosphorus (P) to surface waters on short timescales in shallow lakes. However, the long-term effects of hypolimnetic redox conditions and trophic state on sedimentary P fraction retention in deep lakes are not clear yet. Hypolimnetic withdrawal of P-rich water is predicted to diminish sedimentary P and seasonal P recycling from the lake hypolimnion. Nevertheless, there is a lack of evidence from well-dated sediment cores, in particular from deep lakes, about the long-term impact of hypolimnetic withdrawal on sedimentary P retention. In this study, long-term sedimentary P fraction data since the early 1900s from Lake Burgäschi provide information on benthic P retention under the influence of increasing lake primary productivity (sedimentary green-pigment proxy), variable hypolimnion oxygenation regimes (Fe∕Mn ratio proxy), and hypolimnetic withdrawal since 1977. Results show that before hypolimnetic withdrawal (during the early 1900s to 1977), the redox-sensitive Fe∕Mn-P fraction comprised ∼50 % of total P (TP) in the sediment profile. Meanwhile, long-term retention of total P and labile P fractions in sediments was predominantly affected by past hypolimnetic redox conditions, and P retention increased in sedimentary Fe- and Mn-enriched layers when the sediment-overlaying water was seasonally oxic. However, from 1977 to 2017, due to eutrophication-induced persistent anoxic conditions in the hypolimnion and to hypolimnetic water withdrawal increasing the P export out of the lake, net burial rates of total and labile P fractions decreased considerably in surface sediments. By contrast, refractory Ca–P fraction retention was primarily related to lake primary production. Due to lake restoration since 1977, the Ca–P fraction became the primary P fraction in sediments (representing ∼39 % of total P), indicating a lower P bioavailability of surface sediments. Our study implies that in seasonally stratified eutrophic deep lakes (like Lake Burgäschi), hypolimnetic withdrawal can effectively reduce P retention in sediments and potential for sediment P release (internal P loads). However, after more than 40 years of hypolimnetic syphoning, the lake trophic state has not improved nor has lake productivity decreased. Furthermore, this restoration has not enhanced water column mixing and oxygenation in hypolimnetic waters. The findings of this study are relevant regarding the management of deep eutrophic lakes with mixing regimes typical for temperate zones.

Under the guidance of sequence stratigraphy theory and method, the comprehensive utilization of seismic, logging, drilling and core data, set up the pear tree fault fault depression sequence stratigraphy framework. Pear tree will sag from top to bottom drill in quaternary, upper cretaceous qingshankou formation, lower cretaceous quantou formation, denglouku group, the city group, shahe, fire stone mountain group and basement, and focus on description of quantou formation, denglouku group, the city group, shahe, fire stone mountain group interface features. And the seven tree, Qin Gutun key stratigraphic classification and correlation in the study area for research. 1 Regional geological survey Pear sag is located in the southeast uplift area, songliao basin is a composite basin superimposed fault depression, east of tanlu fault zone, pear, gongzhuling across two city, covers an area of about 2300 km, mining area resources 360 million tons of oil equivalent, 205 opening of exploratory well, the whole sag found nine oil and gas fields, proven oil reserves of 44.3585 million tons, proven degree is 20.6%; Proven gas geological reserves of 19.341 billion square, the proven degree is 13.5%. Is divided into four secondary structural belt, the Northern Slope zone, steep slope zone, the central structural belt, west slope area in the east. Figure 1 pear trees in the study area 2 Sequence interface features Shahe subgroups (K1sh):fault sequence, the distribution is controlled by fault depression, stratigraphic thickness generally 600-1400 m, in the pear tree faulted the thickest of up to 2500 m. 2nd International Conference on Electrical, Computer Engineering and Electronics (ICECEE 2015) © 2015. The authors Published by Atlantis Press 1302 To mulberry fracture is bounded in the west and east, south overlap, to the north by denudation. The group at the bottom of the alluvial fan and braided river sedimentary, the upper plate to sub-sag in shore and shallow lake to half deep lake deep lake facies, basin around the development of fan delta, alluvial fan and limnetic facies. The group stratum layer in the development of important hydrocarbon source rocks in this area. City group(K1yc):belong to fault sequence, the group characteristics of stratigraphic distribution and shahe subgroups similar characteristics, to mulberry fracture is bounded in the west and east, south direction overlap, north raised by denudation, stratum thickness is usually 200-800 m. Sedimentary characteristics, its inheritance shahe subgroups period water scope to further expand, but water is a bit lighter. Main development of braided river delta or alluvial fan, fan delta, littoral and shallow lake, half deep lake-deep lake deposits, such as high quality hydrocarbon source rocks, also can form high quality reservoir, often form since the author classifies the type accumulation combination. Denglouku group (K1d):belong to fault sequence, stratigraphic distribution features inherited battalion city group, the thickness of the 100-1500 m, lithology of light gray, gray, beige, gray sandstone, mudstone and grey, glutenite, unconformable contact with the overlying quantou group, development of sedimentary facies have shore shallow lake and deep lake half deep lake, fan delta deposit, etc. Quantou group (K1q):period of quantou formation in basin evolution into depression stage, no longer restricted by fault basin, are widely distributed. The sedimentary strata in the southern songliao basin are stable distribution, formation thickness usually is 500-1800 m. Lithology is given priority to with oxidation and tonal mudstone and sandstone and glutenite, dominant in river deposits, followed by flood plain, shore and shallow lake sedimentary, delta and its stable distribution of small. 3 The sequence stratigraphic framework analysis 3.1 The north-south direction stratigraphic framework analysis Around in the seismic section the reflection layer interface structure, logging and logging data has obvious feature. Shahe son of stone mountain fire at the bottom of the group, or basal surface of the basin, which is a Mesozoic strata, is formed by uplift period of basin tectonic activities area truncation unconformable surface, corresponding to the seismic reflection interface T5, equivalent to the Jurassic bottom reflection interface. Reflector above show the onlap phenomenon, basal generally strong reflection energy, lower for clutter weak reflection or layered weak reflection. Under interface is basement metamorphic rock, mudstone cover directly above the basement metamorphic rocks, the surface of discontinuity generally represents the sedimentary environment mutation, on logging curves at the same time also have obvious response (figure2). Figure2 sequence region and even the well seismic profiles Figure2 sequence region and even the well seismic profiles

Metagenome sequencing to unveil the resistome in a deep subtropical lake on the Yunnan-Guizhou Plateau, China

Causes and influencing mechanisms of differences in phosphorus occurrence forms in sediments of different types of urban lakes.

Arsenic contamination of lakebed sediments is widespread due to a range of human activities, including herbicide application, waste disposal, mining, and smelter operations. The threat to aquatic ecosystems and human health is dependent on the degree of mobilization from sediments into overlying water columns and exposure of aquatic organisms. We undertook a mechanistic investigation of arsenic cycling in two impacted lakes within the Puget Sound region, a shallow weakly-stratified lake and a deep seasonally-stratified lake, with similar levels of lakebed arsenic contamination. We found that the processes that cycle arsenic between sediments and the water column differed greatly in shallow and deep lakes. In the shallow lake, seasonal temperature increases at the lakebed surface resulted in high porewater arsenic concentrations that drove larger diffusive fluxes of arsenic across the sediment-water interface compared to the deep, stratified lake where the lakebed remained ~10#x00B0;C cooler. Plankton in the shallow lake accumulated up to an order of magnitude more arsenic than plankton in the deep lake due to elevated aqueous arsenic concentrations in oxygenated waters and low phosphate: arsenate ratios in the shallow lake. As a result, strong arsenic mobilization from sediments in the shallow lake was countered by large arsenic sedimentation rates out of the water column driven by plankton settling.

Abstract. The flux of reduced substances, such as methane and ammonium, from the sediment to the bottom water (Fred) is one of the major factors contributing to the consumption of oxygen in the hypolimnia of lakes and thus crucial for lake oxygen management. This study presents fluxes based on sediment porewater measurements from different water depths of five deep lakes of differing trophic states. In meso- to eutrophic lakes Fred was directly proportional to the total organic carbon mass accumulation rate (TOC-MAR) of the sediments. TOC-MAR and thus Fred in eutrophic lakes decreased systematically with increasing mean hypolimnion depth (zH), suggesting that high oxygen concentrations in the deep waters of lakes were essential for the extent of organic matter mineralization leaving a smaller fraction for anaerobic degradation and thus formation of reduced compounds. Consequently, Fred was low in the 310 m deep meso-eutrophic Lake Geneva, with high O2 concentrations in the hypolimnion. By contrast, seasonal anoxic conditions enhanced Fred in the deep basin of oligotrophic Lake Aegeri. As TOC-MAR and zH are based on more readily available data, these relationships allow estimating the areal O2 consumption rate by reduced compounds from the sediments where no direct flux measurements are available.

Methods and equipment used in obtaining cores from sand and silt sediments in deep fjord lakes are described. A piston corer was operated by a rig placed on a raft. The equipment was designed for easy dismantling to cover a coring program including several lakes.

Compared with shallow lakes, less attention has been paid on pollutions in deep lakes. Lake Fuxian is the largest deep lake and an important water resource in China. The knowledge on organochlorine pesticides (OCPs) in sediments of Lake Fuxian was rare. Fifteen surface sediments and one sediment core were collected from Lake Fuxian. Sediment chronology was dated with the activities of 137Cs and 210Pb. Twenty-one OCPs in the surface sediments and sediment core were analyzed by a GC-MS. Spatial and temporal occurrences of OCPs in the sediments of this lake were studied. Correlations, isomer ratios, and principal component analysis (PCA) were applied to apportion the sources of OCPs in the sediments of this lake. The OCPs in the sediments of Lake Fuxian were dominated by p,p'-DDT (4,4'-dichlorodiphenyltrichloroethane) and HCHs (hexachlorocyclohexane). The concentration of ΣOCPs in the surface sediments ranged from 0.42 to 67.5ngg-1, with an average of 42.3 ± 23.5ngg-1 (mean ± SD, n = 15). The concentration of ΣOCPs in the sediment core varied from 3.5 to 707.9ngg-1 in the period from 1950 to 2010, with an average of 167.7 ± 203.7ngg-1 (n = 24). The highest concentrations and fluxes of α-HCH, γ-HCH, and p,p'-DDT were found in the years of 1964 and 1967, respectively. The fluxes of HCH isomers in the sediment core decreased in the orders as γ-HCH > β-HCH > α-HCH in the period from 1950 to 2010. The concentrations of HCHs and p,p'-DDT in the sediments of Lake Fuxian were higher than those of most shallow and deep lakes in the world. HCHs and p,p'-DDT were derived from both the technical HCH and DDT and the usage of lindane and dicofol. Technical DDT and technical HCH may be used simultaneously, but technical DDT and lindane were not applied simultaneously in the catchment. Lindane was used not only in the period from 2002 to 2010 but also in the period from 1950 to 1964 in the catchment.

The organic-rich mudstones within the lacustrine deposits of the Chang 7 member in the Ordos Basin are recognized as the primary source rocks of the Mesozoic petroleum system. Previously, scholars have extensively investigated the formation processes of high-quality source rocks in the deep lake facies of the southern part of the basin. However, systematic studies on the differential enrichment of organic matter in the Chang 7 member across the entire basin are lacking. In this study, geochemical analyses, including rock pyrolysis, total organic carbon (TOC) content, saturate hydrocarbon gas chromatography–mass spectrometry, and major and trace element analyses, are performed to determine the hydrocarbon generation potential of the Chang 7 member source rock in shallow lake facies and illustrate the differences in the organic matter enrichment of this member between the deep and shallow lake facies. The shallow lake facies Chang 7 member source rocks in the northern part of the basin are generally of medium to high quality. These rocks are mature and feature II1–II2 organic matter types, which can be considered as effective source rocks for oil-gas accumulation in suit. In shallow lake facies, a warm and humid climate facilitated the input of nutrients from terrigenous clastics for primary producer, which resulted in higher organic matter abandunce in the shallow lake facies of the Chang 7₁₊₂ sub-member interval compared to coeval deep lake sediments. Conversely, the deep lake facies of the Chang 7₃ sub-member interval, influenced by volcanic and hydrothermal activity, exhibited significantly higher organic matter abundance. Frequent and intense volcanic activities introduced volcanic ash and hydrothermal inputs, which reduced gas exchanges between atmosphere and watermass, as well as increased water salinity, fostering a stratified and anoxic-euxinic watermass that promoted organic matter preservation. However, shallow lake regions remained less affected by volcanic influences due to long distance from volcanic and hydrothermal activity area, with organic matter accumulation primarily driven by terrigenous nutrient supply under warm-humid climatic conditions.

Mechanism and control of lake eutrophication

Natural and anthropogenic influences on sterol geochemical characteristics in lake sediments and implications for using sterols as paleoenvironmental indicators

Research Article| February 01, 1999 Tectonic and sediment supply control of deep rift lake turbidite systems: Lake Baikal, Russia C. Hans Nelson; C. Hans Nelson 1U.S. Geological Survey, Menlo Park, California 94025, USA Search for other works by this author on: GSW Google Scholar Evgeny B. Karabanov; Evgeny B. Karabanov 2Department of Geological Science, University of South Carolina, Columbia, South Carolina 29208, USA Search for other works by this author on: GSW Google Scholar Steven M. Colman; Steven M. Colman 3U.S. Geological Survey, Woods Hole, Massachusetts 02543, USA Search for other works by this author on: GSW Google Scholar Carlota Escutia Carlota Escutia 4Ocean Drilling Program, Texas A & M University, College Station, Texas 77845, USA Search for other works by this author on: GSW Google Scholar Geology (1999) 27 (2): 163–166. https://doi.org/10.1130/0091-7613(1999)027<0163:TASSCO>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation C. Hans Nelson, Evgeny B. Karabanov, Steven M. Colman, Carlota Escutia; Tectonic and sediment supply control of deep rift lake turbidite systems: Lake Baikal, Russia. Geology 1999;; 27 (2): 163–166. doi: https://doi.org/10.1130/0091-7613(1999)027<0163:TASSCO>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentBy SocietyGeology Search Advanced Search Abstract Tectonically influenced half-graben morphology controls the amount and type of sediment supply and consequent type of late Quaternary turbidite systems developed in the active rift basins of Lake Baikal, Russia. Steep border fault slopes (footwall) on the northwest sides of half-graben basins provide a limited supply of coarser grained clastic material to multiple small fan deltas. These multiple sediment sources in turn laterally feed small (<10 km diameter) unchannelized sublacustrine sand-rich aprons that are deposited at the slope base on the lake floor. Gradual slopes of the southeastern ramp margins (hanging wall) of the lake basins, conversely, feed finer grained sediment from larger drainages into two different types of channelized turbidite sublacustrine fan systems: (1) small (5–20 km) laterally fed sand-rich fans sourced by local rivers, often originating from glaciated valleys; and (2) large (>65 km) axially fed elongate mud-rich fans sourced by regional exterior drainage of the Selenga River that supplies large quantities of silt. Basin plain turbidites in the center of the linear basins and axial channels that are controlled by rift-parallel faults are fed from, and interfinger with, aprons and fans. The predictability of the turbidite systems in Lake Baikal provides the best example yet studied of how tectonics and sediment supply interact to control the development of a wide variety of coeval turbidite systems on a single basin floor. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not currently have access to this article.

The collapse of the Fundão tailings dam in 2015 triggered widespread contamination across the Doce River basin, yet its long-term effects on lacustrine environments remain poorly understood. This study investigates how sediment mineralogy influences the retention and mobility of potentially toxic elements (PTEs) in shallow and deep lakes of the Lower Doce River. Between 2018 and 2019, bottom sediment samples (0-5cm) were collected from three deep lakes (Limão, Nova, and Juparanã) and three shallow lakes (Areão, Areal, and Monsarás). Twenty-four sediment samples were analyzed for mineralogy (X-ray diffraction and Fourier-transform infrared spectroscopy) and PTE concentrations using sequential extraction followed by ICP-MS/MS. PTEs were fractionated through a six-step sequential chemical extraction designed to isolate soluble/exchangeable, carbonate-bound, Fe oxide-bound (including poorly crystalline and crystalline phases), and pyrite-associated fractions. The results show that goethite and hematite are the main Fe oxyhydroxides in lake sediments, suggesting the legacy of deposited tailings. Deep lakes contain well-crystallized, Al-substituted goethites that enhance the retention of As, Cr, and V in more stable geochemical fractions. In contrast, shallow lakes, especially Areal and Monsarás, exhibit slightly higher hematite content and goethites with lower Al substitution and specific surface area, indicating reduced stability and greater susceptibility to redox-driven dissolution. Additionally, PTEs such as Co, Cu, Ni, Pb, and Zn are primarily associated with poorly crystalline Fe phases like ferrihydrite and lepidocrocite, which are prone to dissolution under anoxic conditions. Risk assessments indicate higher carcinogenic risks from As, Cr, and Ni exposure in shallow lakes, especially for children.

Multiple sedimentation: A method for analysis and separation of particle mixtures

The seasonal dynamics of freshwater lake ice and its interactions with air and snow are studied in two small subarctic lakes with comparable surface areas but contrasting depths (4.3 versus 91 m). Two, 2.9 m long thermistor chain sensors (Snow and Ice Mass Balance Apparatuses), were used to remotely measure air, snow, ice, and water temperatures every 15-min between December 2021 and March 2022. Results showed that freeze-up occurred later in the deeper lake (Ryan Lake) and earlier in the shallow lake (Landing Lake). Ice growth was significantly faster in Ryan Lake than in Landing Lake, due to cold water temperatures (mean (Tw¯) =0.65 to 0.96°C) persisting beneath the ice. In Landing Lake, basal ice growth was hindered because of warm water temperatures (Tw¯=1.5 to 2.1°C) caused by heat released from lake sediments. Variability in air temperatures at both lakes had significant influences on the thermal regimes of ice and snow, particularly in Ryan Lake, where ice temperatures were more sensitive to rapid changes in air temperatures. This finding suggests that conductive heat transfer through the air-water continuum may be more sensitive to variability in air temperatures in deeper lakes with colder water temperatures than in shallow lakes with warmer water temperatures, if snow depths and densities are comparable. This study highlights the significance of lake morphology and rapid air temperature variability on influencing ice growth processes. Conclusions drawn aim to improve the representation of ice growth processes in regional and global climate models, and to improve ice safety for northern communities.