Modern Accumulation Rates Research Articles

A synthesis of modern organic carbon accumulation rates in coastal and aquatic inland ecosystems

Organic carbon accumulation in the sediments of inland aquatic and coastal ecosystems is an important process in the global carbon budget that is subject to intense human modification. To date, research has focused on quantifying accumulation rates in individual or groups of aquatic ecosystems to quantify the aquatic carbon sinks. However, there hasn’t been a synthesis of rates across aquatic ecosystem to address the variability in rates within and among ecosystems types. Doing so would identify gaps in our understanding of accumulation rates and potentially reveal carbon sinks vulnerable to change. We synthesized accumulation rates from the literature, compiling 464 rate measurements from 103 studies of carbon accumulated in the modern period (ca. 200 years). Accumulation rates from the literature spanned four orders of magnitude varying substantially within and among ecosystem categories, with mean estimates for ecosystem categories ranging from 15.6 to 73.2 g C m−2 y−1 within ecosystem categories. With the exception of lakes, mean accumulation rates were poorly constrained due to high variability and paucity of data. Despite the high uncertainty, the estimates of modern accumulation rate compiled here are an important step for constructing carbon budgets and predicting future change.

Basal topographic controls on the stability of the West Antarctic ice sheet: lessons from Foundation Ice Stream

ABSTRACT Using observations of basal topography, ice thickness and modern accumulation rates, we use theory and a dynamic flowline model to examine the sensitivity of Antarctica's Foundation Ice Stream to changes in sea level, accumulation and buttressing at the grounding line. Our sensitivity studies demonstrate that the steep, upward-sloping basal topography inland from the grounding line serves to stabilize retreat of the ice stream, while the upward-sloping submarine topography downstream from the grounding line creates the potential for significant advance under conditions of modest sea-level lowering and/or increased accumulation rate. Extrapolating from Foundation Ice Stream, many nearby Weddell Sea sector ice streams are in a similar configuration, suggesting that the historical and projected responses of this sector's ice streams may contrast with those in the Amundsen or Ross Sea sectors. This work reaffirms that the greatest concerns for rapid West Antarctic Ice Sheet (WAIS) retreat are locations of reverse slopes, muted basal topography and limited lateral support.

Modern accumulation rates and sources of organic carbon in the NE Gulf of Cádiz (SW Iberian Peninsula)

Organic carbon (OC) content, elemental (C/N) and isotopic (δ 13C) composition of organic matter (OM) constrain relative contributions from both marine and terrestrial sources to modern sediments in the NE Gulf of Cadiz (GoC) shelf. C/N and (δ 13C) indicate a transition from a dominantly marine to a terrestrial input of OM deposited in Bay of Cadiz and the Guadalquivir prodelta. OC and mass accumulation rates (MARs, based on bulk density and 210Pb-derived sediment MAR) suggest that labile OM from primary productivity accounts for the low OC content and burial rates in sediments in the NE GoC shelf.

Volumetric budget calculation of sediment and carbon storage and export for a late Holocene mid-shelf mudbelt system (NW Iberia)

Confined fine-grained depoenters (mudbelts) on continental shelves play an important role as common and major fluviogenic submarine depocenters along the source-to-sink pathway and in global sedimentary and carbon cycles. This study provides a complete high-resolution isopach-based budget analysis using closely-spaced, high-resolution seismic-reflection data of an exemplary mid-shelf mudbelt system located on the open and narrow continental shelf of NW Iberia.The budget analysis reveals that 3.957–4.227km3 of sediments [i.e., 4073 to 4351Mt (dry)] are stored in this depocenter. In conjunction with river-discharge estimates, we calculate that, over the past 5300yr, approximately 34% to 36% of total fluvial sediments supplied to the ocean remain in the shelfal mud depocenter and the balance bypasses the shelf. Total accumulation values for TOC and CaCO3 amount to 40.31 to 43.46t and 174.73 to 186.68Mt, respectively. High-resolution isopach analysis shows high regional morphodynamic variability of the main sediment transit routes, an aspect easily overlooked by core-based or low-resolution profiling studies. The budget analysis reveals persistent low accumulation over the past 5300yr and thus clarifies that a uniformitarian view of applying modern accumulation rates to the late Holocene can significantly underestimate effective sediment off-shelf transport.

Anthropogenic versus natural control on trace element and Sr–Nd–Pb isotope stratigraphy in peat sediments of southeast Florida (USA), ∼1500 AD to present

Analysis of a well-dated peat core from Blue Cypress Marsh (BCM) provides a detailed record of natural and anthropogenic factors that controlled the geochemical cycles of a number of trace elements in Florida over the last five centuries. The trace elements were divided into “natural” and “anthropogenic” groups using concentration trends from the bottom to the top of the core. The “natural” group includes Li, Sc, Cr, Co, Ga, Ge, Zr, Nb, Cs, Ba, Hf, Y, Ta, Th, and REE (Rare Earth Elements). These elements show similar concentrations throughout the core, indicating that changes in human activities after European arrival in the “New World” did not affect their geochemical cycles. The “anthropogenic” group includes Pb, Cu, Zn, V, Sb, Sn, Bi, and Cd. Upcore enrichment of these elements indicates enhancement by anthropogenic activities. From the early 1500s to present, fluxes of the “anthropogenic” metals to the marsh increased significantly, with modern accumulation rates several-fold (e.g., V) to hundreds of times (e.g., Zn) greater than pre-colonial rates. The dominant input mechanism for trace elements from both groups to the marsh has been atmospheric deposition. Atmospheric input of a number of the elements, including the anthropogenic metals, was dominated by local sources during the last century. For several elements, long-distant transport may be important. For instance, REE and Nd isotopes provide evidence for long-range atmospheric transport dominated by Saharan dust. The greatest increase in flux of the “anthropogenic” metals occurred during the 20th century and was caused by changes in the chemical composition of atmospheric deposition entering the marsh. Increased atmospheric inputs were a consequence of several anthropogenic activities, including fossil fuel combustion (coal and oil), agricultural activities, and quarrying and mining operations. Pb and V exhibit similar trends, with peak accumulation rates in 1970. The principal anthropogenic source of V is oil combustion. The decline in V accumulation after 1970 in the BCM peat corresponds to the introduction of low-sulfur fuels and the change from heavy to distilled oils since the 1970s. After the 1920s, Pb distribution in the peat follows closely the history of alkyl lead consumption in the US, which peaked in the 1970s. Pb isotopes support this inference and furthermore, record changes in the ore sources used to produce leaded gasoline. Idaho ores dominated the peat Pb isotope record until the 1960s, followed by Pb from Mississippi Valley Type deposits from the 1960s to the 1980s. Enhanced fluxes of Cu, Zn, Cd, Sn, Sb, Bi, and to some extent Ni during the last century are likely also related to fossil fuel combustion. Local agricultural activities may also have influenced the geochemical cycles of Cu and Zn. The peat record shows enhanced U accumulation during the last century, possibly related to phosphate mining in western Florida. Sr isotopes in the peat core also reflect anthropogenic influence. The 87Sr/ 86Sr ratio decreases from natural background values in the basal part of the core to lower values in the upper part of the core. The Sr isotope shift is probably related to quarrying operations in Florida, and marks the first time an anthropogenic signal has been detected using the Sr isotope record in a peat core.

Modern accumulation rates and a budget of sediment off the Gaoping (Kaoping) River, SW Taiwan: A tidal and flood dominated depositional environment around a submarine canyon

Ninety-two box cores collected during 2004–2006 from an area of ~ 3000 km 2 off the Gaoping (formerly spelled Kaoping) River, SW Taiwan, were analyzed for fallout radionuclides ( 210Pb, 137Cs and 7Be) to elucidate sedimentation rates and processes, and for the calculation of a sediment budget. The study area is located at an active collision margin with a narrow shelf and a submarine canyon extending essentially into the river's mouth. The results indicate fairly constant hemipelagic sedimentation in much of the open margin and for most of the time except in the inner shelf and along the axis of the canyon where sediment transport is more dynamic and is controlled by tidal current and wave activities constantly, and by fluvial floods or gravity-driven flows episodically. Sedimentation rates in the study area derived from 210Pb and constrained by 137Cs vary from 0.04 to 1.5 cm/yr, with the highest rates (> 1 cm/yr) flanking the Gaoping canyon over the upper slope (200–600 m) and the lowest rates (< 0.1 cm/yr) in the distal basin beyond the continental slope. The depocenter delineated from 210Pb-based sedimentation rates overlaps with the area covered by a flood layer resulting from super-typhoon Haitang in July 2005. Such correspondence supports the notion that the processes operating on event timescale have bearing on the formation of the sediment strata over centennial or longer timescales. From the distribution of sedimentation rates, sediment deposited in the study area annually is estimated to be 6.6 Mton/yr, accounting for less than 20% of Gaoping River's sediment load. The calculated budget, coupled with the presence of the short-lived 7Be and non-steady-state distribution of low levels of 210Pb in sediments along the canyon floor, suggests rapid transport of sediment from Gaoping River's mountainous watershed (the source) via the Gaoping (Kaoping) Submarine Canyon and adjacent channels (as the conduit and temporary sink) to the abyssal plain and the Manila Trench in the South China Sea (the ultimate sink).

Modern accumulation rates of biogenic silica in Baikal bottom sediments: significance of diatom species composition

The modern distribution of biogenic silica (SiO 2biog) in Baikal surface (0–0.2 and 0–0.5 cm) sediments, its mass accumulation rates (MAR), and the processes responsible for this distribution were studied. The contents of SiO 2biog were determined in samples from 87 stations evenly distributed throughout the lake water area. These data were used to calculate the MAR of SiO 2biog and compile SiO 2biog and MAR distribution maps. The maps showed that the MAR varies significantly throughout the study area. Its highest values have been established in North Baikal. In Central and South Baikal the MAR values are much lower, and the minimum values are observed in the Selenga shoal. This MAR distribution pattern is consistent with the distribution of frustules of Aulacoseira baicalensis endemic diatoms throughout the surface sediments. Compared with other modern diatom species, this one has the most massive and heaviest frustules, which undergo the least dissolution when settling. This suggests that the above species plays a leading role in the accumulation of biogenic silica in modern Baikal bottom sediments, whereas the role of thin-walled species is minor because of their small mass and partial or complete dissolution in water on settling. Dilution of the sediments with terrigenous material is less significant for the SiO 2biog accumulation.

Temporal and spatial complexity in post-glacial sedimentation on the tectonically active, Poverty Bay continental margin of New Zealand

On the eastern Raukumara Ranges of the New Zealand East Coast, active tectonics, vigorous weather systems, and human colonisation have combined to cause widespread erosion of the mudstone- and sandstone-dominated hinterland. The Waipaoa River sedimentary dispersal system is an example that has responded to environmental change, and is now New Zealand's second largest river in terms of suspended sediment discharge. This paper presents new sediment accumulation rates for the continental shelf and slope that span century to post-glacial time scales. These data are derived from radiochemical tracer, palynological, tephrostratigraphic, and seismic methods. We hypothesise on the temporal and spatial complexity of post-glacial sedimentation across the margin and identify the broad extent of sediment dispersal from the Waipaoa system. The ∼15 km 3 Poverty Bay mid-shelf basin lies adjacent to the mouth of the Waipaoa River, reaching a maximum thickness of ∼45 m. A post-glacial mud lobe of an additional ∼3 km 3 extends through the Poverty Gap and out onto the uppermost slope, attaining 40 m thickness in a structurally controlled sub-basin. Here, an offset in the last-glacial erosion surface indicates that deposition was sympathetic with fault activity and the creation of accommodation space, implying that sedimentation was not supply limited. Contrary to classical shelf sedimentation models, the highest modern accumulation rate of 1 cm y −1 occurs on the outer-shelf sediment lobe, approximately ∼2 times the rate recorded at the mid-shelf basin depocentre, and ∼10 times faster than the excess 210Pb rates estimated from the slope. Pollen records from slope cores fingerprint Polynesian then European settlement, and broaden the spatial extent of post-settlement sedimentation initially documented from the Poverty Bay mid-shelf. Changes in sub-millennial sedimentation infer a 2–3-times increase in post-settlement accumulation on the shelf but a smaller 1–2 times increase on the slope. Over longer time scales, seismic evidence infers slower but steady sedimentation since the last transgression, and that significant cross-shelf sediment pathways pre-date the increase in sedimentation resulting from colonisation and deforestation. From a summation of coastal bedload, shelf and slope sediment mass accumulation, the total sediment budget for the Holocene is ∼1 Mt y −1. Under modern conditions a larger proportion of the Waipaoa sediment dispersal system likely extends onto the slope and beyond.

Human influence on heavy metal distribution in the Upper Lake Nansi sediments, Shandong Province, China

Core and surface sediment samples were collected from three sub-lakes (Lake Nanyang, Lake Dushan and Lake Zhaoyang) in the Lake Nansi Basin, Shandong Province. In order to reveal the characteristics of spatial and historical distribution of heavy metals in different sublakes of the Upper Lake Nansi, heavy metal (As, Cr, Cu, Hg, K, Mn, Ni, Pb, Zn, Al, Fe, Ti and V) concentrations of sediment samples were investigated. Based on the activity of137Cs in the sediments, the modern accumulation rate of Lake Nansi sediments is 3.5 mm/a. Our results show that the whole Upper Lake Nansi has been already polluted by heavy metals, among which Lake Nanyang has been polluted seriously by mercury, as well as by lead and arsenic, while Lake Dushan has been most seriously polluted by lead and arsenic. Historical variation of heavy metal (Cr, Cu, K, Ni, Zn, Al, Fe, Ti and V) concentrations shows an abrupt shift in 1962, resulting in a division of two periods: from 1957 to 1962 when metal enrichment increased with time, and from 1962 to 2000 when it decreased with time, while that of some anthropogenic elements such as Hg, Pb and Mn tend to increase toward the surface. However, the variation trend of As in the sediments is different from that of Hg, Pb and Mn, with its maximum value appearing in 1982. Since 1982 the concentrations of As have decreased due to the forbidden use of arsenite pesticides. This variation trend revealed changes in manner of human activity (coal combustion, waste discharges from both industries and urban sewage) within the catchment during different periods.

Topographic control of regional accumulation rate variability at South Pole and implications for ice-core interpretation

AbstractSnow-accumulation rates are known to be sensitive to local changes in ice-sheet surface slope because of the effect of katabatic winds. These topographic effects can be preserved in ice cores that are collected at non-ice-divide locations. The trajectory of an ice-core site at South Pole is reconstructed using measurements of ice-sheet motion to show that snow was probably deposited at places of different surface slope during the past 1000 years. Recent accumulation rates, derived from shallow firn cores, vary along this trajectory according to surface topography, so that on a relatively steep flank mean annual accumulation is ∼18% smaller than on a nearby topographic depression. These modern accumulation rates are used to reinterpret the cause of accumulation rate variability with time in the long ice-core record as an ice-dynamics effect and not a climate-change signal. The results highlight the importance of conducting ancillary ice-dynamics measurements as part of ice-coring programs so that topographic effects can be deconvolved from potential climate signals.

History of Mercury Loading in the Upper Mississippi River Reconstructed from the Sediments of Lake Pepin

An array of sediment cores was analyzed to determine historical trends in mercury (Hg) accumulation in Lake Pepin, a natural lake on the Upper Mississippi River. Whole-basin Hg accumulation rates increased from 3 kg/yr before European settlement (ca. 1830) to a maximum of 357 kg/yr in the 1960s. The recent Hg accumulation rate (110 kg/yr, 1990−1996) is experimentally indistinguishable from measured Hg loadings in the river entering the lake, indicating that accumulation rates in Lake Pepin correspond quantitatively to river loadings. The modern accumulation rate represents a decline of almost 70% from the peak value, reflecting large decreases in Hg inputs to the Mississippi River from industrial and municipal point sources in the metropolitan Minneapolis/St.Paul area upstream. A total of 18.1 t of Hg has been deposited in Lake Pepin since 1800; half of that (9.0 t) was deposited between 1940 and 1970, when regional growth accelerated rapidly but pollution control mechanisms were inadequate. Point sources accounted for approximately 60% of the Hg accumulating in Lake Pepin in the 1960s, but these inputs have been virtually eliminated since then.

Modern accumulation rates and a sediment budget for the Eel shelf: a flood-dominated depositional environment

The northern California continental margin is periodically impacted by geologically significant storms, which have a marked influence on terrigenous sediment supply, flood deposition, and long-term accumulation of fine-grained sediment on the Eel shelf. Accumulation of Eel River muds on the adjacent shelf was investigated using 210Pb and 137Cs geochronologies, in order to understand the fate of sediment discharged by the Eel River and to relate patterns of net sediment accumulation (100-yr time scale) to sediment dynamics. 210Pb data demonstrate that modern accumulation of river mud occurs from the 50-m isobath seaward. Across-shelf accumulation rates decrease from maximum mid-shelf values of 0.6–1.7 g cm −2 yr −1 to values of 0.2–0.4 g cm −2 yr −1 at the shelf break, with a spatially weighted mean of 0.5 g cm −2 yr −1 (0.4 cm/yr) for the entire shelf. 210Pb xs sediment-depth profiles from the region of highest accumulation rate are characterized by subsurface intervals of low and uniform activity, which are produced by flood deposition. In some cores, particular 210Pb xs activity intervals may be associated with major Eel River floods of 1955, 1964, and 1974. It is postulated that, because of the coincidence of high-river-flow events and southerly winds during cyclonic winter storms, net northward transport allows for preferential deposition of fine-grained sediment north of the river mouth. Over the past ∼100 years, fluvial sediment input combined with marine dispersal processes have produced a mid-shelf depocenter, evident by both the spatial distribution of 210Pb accumulation rates and by clay-rich flood layers partially preserved in shelf deposits. A fine-grained sediment budget for the dispersal system, based on hydrological data and 210Pb geochronologies, demonstrates that a maximum of ∼20% (3×10 9 kg/yr) of the mean annual supply of fluvial mud (14×10 9 kg/yr) is trapped on the shelf. The results of this study demonstrate that: (1) short-term sedimentation processes associated with floods can influence sediment accumulation on longer time scales; and (2) a major fraction of fine-grained sediment supplied to tectonically active margins by flood-prone mountainous rivers bypasses narrow continental shelves.

Temperature, accumulation, and ice sheet elevation in central Greenland through the last deglacial transition

We present a combined heat‐ and ice‐flow model, constrained by measurements of temperature in the Greenland Ice Sheet Project 2 (GISP2) borehole and by the GISP2 δ18O record and depth‐age scale, which determines a history of temperature, accumulation rate, and ice sheet elevation for the past 50,000 years in central Greenland. Important results are: that the temperature increase from average glacial to Holocene conditions was large, approximately 15°C, with a 20°C warming from late glacial to Holocene; that the average accumulation rate during the last glacial maximum (between 15 and 30 kyr B. P.) was 5.5 to 7 cm yr−1, approximately 25% of the modern accumulation rate; that long‐term (500–1000 years) averaged accumulation rate and temperature have been inversely correlated during the most recent 7 millennia of the Holocene; and that the Greenland Ice Sheet probably thickened during the deglacial transition. The inverse correlation of accumulation rate and temperature in the mid and late Holocene suggests that the Greenland Ice Sheet is more prone to volume reduction in a warmed climate than previously thought and demonstrates that accumulation rate is not a reliable proxy for temperature. The elevation history of the ice sheet is poorly constrained by the model, and independent evidence is needed. We also present a simple estimate of the response time for thinning of the interior region of an ice sheet due to retreat of its margins. This was approximately 1900 years for central Greenland during deglaciation.

The sedimentary record of Moose Lake: implications for glacier activity in the Mount Robson area, British Columbia

The postglacial sedimentary environment of Moose Lake was investigated using 3.5 kHz subbottom profiles and cores from the sediment surface. A late phase in the deglaciation of the upper Fraser River valley involved a valley glacier that flowed east to west and that terminated near the present-day outlet of Moose Lake. The overdeepened Fraser valley was infilled with ice-contact sediments, including terminal and recessional moraines, thereby damming westward drainage and forming Moose Lake. Eastward glacier retreat resulted in the deposition of ice blocks in the shallow west zone of the lake, where subsequent melting disturbed conformable glaciolacustrine deposits. The main Moose Lake basin records a transition from proximal to distal proglacial environments. However, late glacial and postglacial sediments are dominated by settling from suspension. Coarse, but localized, sediment inputs are derived from the Thunder Creek fan-delta and avalanche activity on the north-facing slope of the south shore. Depths to major acoustic reflectors and known modern accumulation rates of 2.7 mm a−1 indicate that the upper 15.5 m of sediment fill represents deposition during the Holocene and accounts for less than one third of the total late glacial and postglacial sediment yield. Sedimentary structures visible in cores and 14C dating confirm the varved nature of the upper 3 m of sediment. Extreme positive departures in varve thickness are related to above-average discharge to Moose Lake following persistent, glacier-melt-augmented summer flows. The Moose Lake varve chronology confirms the general pattern inferred from other regional evidence of climate deterioration after 1600 AD, which led to glacier advance and moraine emplacement in the Canadian Rocky Mountains.

Time partitioning in cratonic carbonate rocks

Research Article| November 01, 1991 Time partitioning in cratonic carbonate rocks Bruce H. Wilkinson; Bruce H. Wilkinson 1Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109-1063 Search for other works by this author on: GSW Google Scholar Bradley N. Opdyke; Bradley N. Opdyke 1Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109-1063 Search for other works by this author on: GSW Google Scholar Thomas J. Algeo Thomas J. Algeo 2Department of Geology, University of Cincinnati, Cincinnati, Ohio 45221-0037 Search for other works by this author on: GSW Google Scholar Author and Article Information Bruce H. Wilkinson 1Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109-1063 Bradley N. Opdyke 1Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109-1063 Thomas J. Algeo 2Department of Geology, University of Cincinnati, Cincinnati, Ohio 45221-0037 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1991) 19 (11): 1093–1096. https://doi.org/10.1130/0091-7613(1991)019<1093:TPICCR>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Bruce H. Wilkinson, Bradley N. Opdyke, Thomas J. Algeo; Time partitioning in cratonic carbonate rocks. Geology 1991;; 19 (11): 1093–1096. doi: https://doi.org/10.1130/0091-7613(1991)019<1093:TPICCR>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Dissimilarity in relations between thickness, duration, and accumulation rate in Holocene sections, metre-scale Phanerozoic cycles, and epoch-interval Phanerozoic sequences reflects variation in the distribution of depositional and hiatal time at different scales of observation. Modern accumulation rates are strongly dependent on duration of deposition; lower rates correspond to longer durations. Phanerozoic cycle thicknesses are similar to those of Holocene sections, suggesting that both formed while filling similar amounts of accommodation space. However, accumulation rates of Phanerozoic cycles and sequences are about two orders of magnitude less than in modern settings, and they show neither strong dependence on duration of accumulation nor significant variation over Phanerozoic time. Hence, net accumulation is primarily controlled by regional subsidence rate. These relations also allow for determination of that fraction of cycle period recorded as rock and that corresponding to hiatal time at intercycle boundaries. Depending on subsidence rate and amount of compaction, most cratonic carbonate units accumulated over 3% to 30% of the time represented by sequences in which they occur. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Scandinavian limnochronology of sediments and heavy metals

Sediment and peat accumulation rates as well as heavy metal fluxes are examined in Scandinavian lakes, marine coasts and peatlands. Modern accumulation rates are determined using Pb-210 and other chronological tools. Mean deposition rates in the past 150 ± 20 yrs are 3–95, 40–190 and 1–5 mg·cm−2·yr−1 for lakes, marine coasts and peatlands respectively. The Pb-210 fluxes at the investigated sites are quite variable. The lowest values are found for peatlands 0.04–0.20 pCi·cm−2·yr−1 while coastal marine environments showed 0.35–0.70 pCi ·cm−2·yr−1. A wide range of variation of Pb-210 fluxes is obtained for the studied lake sediments 0.01–0.51 pCi·cm−2·yr−1.