Lake Sediment Cores Research Articles

Determining the effects of past gold mining using a sediment palaeotoxicity model

Ore processing techniques used in Yellowknife's largest mining operation, Giant Mine, is responsible for the atmospheric release of approximately 20,000 t of particulate arsenic trioxide and other heavy metal(loids). This rapid deposition of heavy metal(loids) may have caused ecological disturbances to aquatic food webs. Here we use 210Pb and 137Cs dated lake sediment cores from 20 lakes within a 40 km radius of Yellowknife to examine the spatial-temporal distribution of arsenic, antimony and lead. Further, we model the toxicity of the sediment to aquatic biota pre-, during, and post-mining using palaeotoxicity modelling, enrichment factor assessment, and comparisons to national sediment quality guidelines. We found that metal(loid) profiles in sediment peaked during the height of mining operations. These peak metal(loid) concentrations were highest in lakes near the mine's roaster stack, and decreased with distance from the historic mine. Palaeotoxicity modelling of lake sediment archives indicate that there is no significant difference in the mean predicted toxicity of pre- and post-mining samples (p = 0.14), however mining activities in the region significantly increased the predicted toxicity of sediments to aquatic organisms during mining operations (p < 0.001). In the years since roasting processes ceased, the mean palaeotoxicity of all lakes has decreased significantly (p < 0.05), indicating a projected pattern of biological recovery. Importantly, some lakes remain at an elevated risk, indicating that aquatic ecosystems in Yellowknife may continue to have lingering effects on aquatic biota despite the closure of the mine two decades ago.

Interpreting basal sediments and plant fossils in kettle lakes: insights from Silver Lake, Michigan, USA

We report on pollen, plant macrofossils, and associated lithostratigraphy of a sediment core extracted from the base of Silver Lake, a kettle lake in northern Lower Michigan, USA, which reveal a complex deglacial scenario for ice block melting and lake formation, and subsequent plant colonization. Complementary multivariate statistical and squared chord distance analyses of the pollen data support these interpretations. The basal radiocarbon age from the core (17 540 cal years BP) is rejected as being anomalously old, based on biostratigraphic anomalies in the core and the date’s incongruity with respect to the accepted regional deglaciation chronology. We reason that this erroneous age estimate resulted from the redeposition of middle-Wisconsin-age fossils by the ice sheet, mixed with the remains of plants that existed as the kettle lake formed at ca. 10 940 cal years BP by ice block ablation. Thereafter, the kettle lake became a reliable repository of Holocene-age fossils, documenting a mature boreal forest that existed until 10 640 cal years BP, followed by a pine-dominated mixed forest, an early variant of the mixed conifer–hardwood forest that persists to the present day. Our study demonstrates that researchers investigating kettle lakes, a common depositional archive for plant fossils in deglaciated landscapes, should exercise caution in interpreting the basal (Late Pleistocene/early Holocene-age) part of lake sediment cores.

Sediment record of polycyclic aromatic hydrocarbons in Dianchi lake, southwest China: Influence of energy structure changes and economic development

Sixteen polycyclic aromatic hydrocarbons (PAHs) in a sediment core from Dianchi Lake, southwest China, were analysed. The influence of changes in China’s energy structure for 2–6 ringed PAHs was investigated to assess sources and the impact of socioeconomic development on temporal changes in concentrations. The concentration of the ΣPAH16 ranged from 746 to 2293 ng g−1. Prior to the 1960s relatively low concentrations of the ΣPAH16 and a larger proportion of 2–3-ring PAHs indicated that biomass combustion was the main source of PAHs. A rapid increase in the concentrations of 2–3 ring PAHs between 1975 and 2004 was attributed to population growth and coal consumption. A declining trend since 2004 was interpreted as being due to local changes in household energy usage. Increased concentrations of 4-ring PAH between 1975–2005 and 5–6-ring PAHs between the 1980s to 2004 showed correlations with increased coal consumption and the number of motor vehicles, respectively. These were caused by rapid urbanization and industrialization in the Dianchi watershed following the implementation of the Reform and Open Policy in 1978. A subsequent decline in the concentrations of 4-ring and 5–6-ring PAHs may have been due to decreased coal consumption and improvements in emission standards, respectively. Source apportionment by a PMF model revealed that coal combustion (29.2%), vehicle emissions (24.2%), petrogenic sources (21.8%), and biomass combustion (24.9%) were the sources of PAHs in the lake sediment core, and that coal combustion was the most important regional source of PAHs pollution.

Variable Late Holocene 14C Reservoir Ages in Lake Bosten, Northwestern China

Radiocarbon (14C) dating has been widely used in paleoclimate reconstruction. However, the reliability of the 14C age in lake sediments is sensitive to the 14C reservoir effect, especially for a lake in arid regions. In this study, we evaluated the 14C reservoir ages under different hydroclimatic conditions over the past ~2300 years in Lake Bosten, northwestern China, by comparing with different dating results and with multi-proxy indices of a vertical-down sediment core collected in this lake. The 14C reservoir ages during ~ 1800 to 650 BP (a dry interval) are estimated to be approximately 1170 years older than those during ~ 650 -100 BP and those during 2200-1800 BP (wet intervals). We proposed that variation in 14C exchange rate between the dissolved CO2 in lake water and CO2 in the atmosphere, as well as the changing proportion of organic matter in the lake and the catchment, could have contributed to the variable 14C reservoir ages in Lake Bosten. The result of this study suggests that the 14C reservoir effect may be larger in dry periods than in wet periods in the arid/semi-arid area, which should be considered when establishing age models of lake sediment cores from these regions.

Patterns and drivers of development in a west Amazonian peatland during the late Holocene

Amazonian peatlands sequester and store large amounts of carbon below ground and contribute to regional biodiversity. They also present an outstanding opportunity for palaeoecological research. This study uses multiple peat cores to improve our understanding of the long-term development of a peatland (Quistococha) in Peruvian Amazonia, by providing a reconstruction of the spatial patterns of vegetation change and peat accumulation over time across the site. Peat cores taken along transects totalling c. 5 km were used to establish the peat thickness and visible stratigraphy. Of 29 new peat cores, four were selected for pollen analysis, supported by 15 radiocarbon dates. These complement two existing published pollen records from the site, from a peat core and a lake sediment core. Our study shows that peat initiation occurred across the site in the form of primary mire formation between 2400 and 1900 cal yr BP. Following peat initiation, five broadly similar phases of vegetation development are recorded in all the pollen sequences: Amazon floodplain, herbaceous sedge fen, mixed angiosperm flooded forest, mixed palm swamp, Mauritia-dominated palm swamp. In detail, there are differences in the pattern and timing of vegetation change between the sequences. Much of this spatial variation is likely to be the result of the underlying substrate topography. In addition, we find that the difference in vegetation composition between core sites was greater during the early stages of peat accumulation at Quistococha than it is today. Such spatial and temporal variability has significant implications for computer modelling of carbon accumulation in tropical peatlands and, consequently, our understanding of their role in the global carbon cycle. Our findings highlight key challenges for numerical modelling on Holocene timescales, namely the difficulty in quantifying long-term variations in primary productivity, the variable influence of sediment input on carbon accumulation during the early stages of peatland formation, and the difficulty of modelling water tables in sites with variable underlying topography.

Use of pre-industrial baselines to monitor anthropogenic enrichment of metals concentrations in recently deposited sediment of floodplain lakes in the Peace-Athabasca Delta (Alberta, Canada)

Well-designed monitoring approaches are needed to assess effects of industrial development on downstream aquatic environments and guide environmental stewardship. Here, we develop and apply a monitoring approach to detect potential enrichment of metals concentrations in surficial lake sediments of the Peace-Athabasca Delta (PAD), northern Alberta, Canada. Since the ecological integrity of the PAD is strongly tied to river floodwaters that replenish lakes in the delta, and the PAD is located downstream of the Alberta oil sands, concerns have been raised over the potential transport of industry-supplied metals to the PAD via the Athabasca River. Surface sediment samples were collected in September 2017 from 61 lakes across the delta, and again in July 2018 from 20 of the same lakes that had received river floodwaters 2 months earlier, to provide snapshots of metals concentrations (Be, Cd, Cr, Cu, Ni, Pb, V, and Zn) that have recently accumulated in these lakes. To assess for anthropogenic enrichment, surficial sediment metals concentrations were normalized to aluminum and compared to pre-industrial baseline (i.e., reference) metal-aluminum linear relations for the Athabasca and Peace sectors of the PAD developed from pre-1920 measurements in lake sediment cores. Numerical analysis demonstrates no marked enrichment of these metals concentrations above pre-1920 baselines despite strong ability (> 99% power) to detect enrichment of 10%. Measurements of river sediment collected by the Regional Aquatics- and Oil Sands-Monitoring Programs (RAMP/OSM) also did not exceed pre-1920 concentrations. Thus, results presented here show no evidence of substantial oil sands-derived metals enrichment of sediment supplied by the Athabasca River to lakes in the PAD and demonstrate the usefulness of these methods as a monitoring framework.

Preliminary data on formation and depositional environments of lake Chaika in the central part of the Curonian Spit (Kaliningrad region, Russia, South-Eastern Baltic)

Lake Chaika is the only major water body present in the sand barriers of the entire territory of South-Eastern Baltic shoreline. The article provides new insights into the formation of Lake Chaika, based on data acquired through a lithological investigation of the lake sediment core combined with an organic matter content analysis, a macrofossil analysis, a radiocarbon AMS-dating and a bathymetric survey. The study revealed that Lake Chaika was formed around 500 years ago. The kettle of the lake appears to have not been submerged during the Littorina transgressions. During the mid-late Holocene, the kettle of the lake was occupied by the peat-forming ecosystems of alder carrs and sedge fens with scattered alder. The accumulation of ligneous and sedge peat occurred. The sand horizon, separating the gyttja layer from peat deposits, is considered to be a time marker for the so-called “sand disaster”, which began in the study site 200-250 years earlier than in the main territory of the Curonian Spit. There are three main formation phases of the lake’s ecosystem: the period of carrs (5390–510 cal. yr BP), the “sand disaster” period (≈550–500 cal. yr BP) and the proper lake period (500 cal. yr BP – present time).

Vegetation history of Eastern Ladoga region (Russia) during the Holocene based on pollen study of Piskarskoe Lake sediment core

The Onega-Ladoga isthmus is a relatively poorly studied part of the Northwestern Russia in terms of palaeo palynology. However, this area is a very important for understanding of human colonization of the Karelia Region. In addition, archaeological sites, beginning from the end of the Paleolithic, have been discovered here. This allows us to trace the human impact on the environment for the past 10,000 years. It found that the vegetation around of Lake Piskarskoe several times changed from cold-loving to warm-loving, and from hygrophytic to mesophytic. A Piskarskoe wetland began to form as a bog at the end of the Atlantic period while the maximum swamping rates happened in the Subatlantic period. As the lake is placed in a hard-reached area, there were not any anthropogenic indicators in spectra. This requires a detailed multimethod study of the core to define indicators of anthropogenic impact.

An Arctic watershed observatory at Lake Peters, Alaska: weather–glacier–river–lake system data for 2015–2018

Abstract. Datasets from a 4-year monitoring effort at Lake Peters, a glacier-fed lake in Arctic Alaska, are described and presented with accompanying methods, biases, and corrections. Three meteorological stations documented air temperature, relative humidity, and rainfall at different elevations in the Lake Peters watershed. Data from ablation stake stations on Chamberlin Glacier were used to quantify glacial melt, and measurements from two hydrological stations were used to reconstruct continuous discharge for the primary inflows to Lake Peters, Carnivore and Chamberlin creeks. The lake's thermal structure was monitored using a network of temperature sensors on moorings, the lake's water level was recorded using pressure sensors, and sedimentary inputs to the lake were documented by sediment traps. We demonstrate the utility of these datasets by examining a flood event in July 2015, though other uses include studying intra- and inter-annual trends in this weather–glacier–river–lake system, contextualizing interpretations of lake sediment cores, and providing background for modeling studies. All DOI-referenced datasets described in this paper are archived at the National Science Foundation Arctic Data Center at the following overview web page for the project: https://arcticdata.io/catalog/view/urn:uuid:df1eace5-4dd7-4517-a985-e4113c631044 (last access: 13 October 2019; Kaufman et al., 2019f).

Deglaciation history at the Alpine‐Mediterranean transition (Argentera‐Mercantour, SW Alps) from 10Be dating of moraines and glacially polished bedrock

AbstractEstimating the extent and age of the last glacial maxima as well as the chronology of glacial recessions in various environmental contexts is key to source‐to‐sink studies and paleoclimate reconstructions. The Argentera‐Mercantour massif is located at the transition between the Alps and the Mediterranean Sea, therefore, its deglaciation chronology can be compared to the sediment budget of the Var River basin. Based on 13 new cosmic‐ray exposure (CRE) beryllium‐10 (10Be) datings performed on moraines and polished crystalline bedrocks and 22 reassessed 10Be CRE ages from similar altitude nearby steep basement surfaces, and from a lake sediment core, we can constrain the deglaciation chronology of the Argentera‐Mercantour massif. These data allow for the first time to fully reconstruct the deglaciation history at the scale of the entire massif in agreement with a major glacier recession at c. 15 ka, at the onset of Bølling transition between the Oldest and Older Dryas. Main deglaciation of the upper slopes [2700–2800 m above sea level (a.s.l.)] occurred after the Last Glacial Maximum (LGM) at 20.8–18.6 ka, followed by the main deglaciation of the lower slopes (2300 m a.s.l.) at 15.3–14.2 ka. Finally, the flat polished surfaces above 2600 m a.s.l. and the zones confined within narrow lateral valleys were likely affected by progressive ice melting of remaining debris covered glaciers and moraine erosion following the Younger Dryas re‐advance stage between 12 and 8–9 ka. At lower elevations, the Vens Lake located at 2300 m a.s.l., allows evidence of the onset of lake sedimentation at c. 14 ka and a transition towards a vegetated environment that mainly occurred before 8 ka. Moraine final stabilization at 5 ka might reflect denudation acceleration during the Holocene humid phase. This contribution reveals a glacier–climate relationship more sensitive to warming phases in the southern Alps highlighted by a major decrease of glaciers after c. 15 ka. This major deglaciation is correlated with a 2.5‐fold decrease of sediment discharge of rivers into the Mediterranean Sea. © 2019 John Wiley &amp; Sons, Ltd.

Investigating the molybdenum and uranium redox proxies in a modern shallow anoxic carbonate rich marine sediment setting of the Malo Jezero (Mljet Lakes, Adriatic Sea)

The molybdenum (Mo) and uranium (U) isotope compositions recorded in carbonate rich sediments are emerging as promising paleo-redox proxies. However, the effects of early diagenetic effects within the sediments on these isotope systems are not well constrained. We examined the Mo and U isotopic systematics in anoxic carbonate rich sediments in a semi enclosed karstic marine lake (Malo Jezero) of the Island of Mljet, Adriatic Sea.Measurements of water column redox behavior in the lake since the 1950s, have shown a transition from anoxic-sulfidic conditions in the deeper water column to more oxic conditions and anoxia refined to the sediment and pore-waters. A 50 cm long sediment core from the deepest part of the lake, show a transition from moderate to high authigenic Mo and U accumulation with depth, consistent with the changing lake redox environment in the past. In the deep euxinic part of the core, the authigenic Mo and U are isotopically lighter and heavier, respectively, than seawater, following similar systematics as observed in other modern euxinic basins, with high, but non-quantitative, Mo and U uptake into the sediments.Based on Bahamas bank carbonate sediments, it has been suggested that the 238U/235U ratio is ~+0.25‰ higher compared to seawater from the effects of early carbonate sediment diagenesis and this carbonate vs. seawater off-set is applicable to carbonate rich sediments across the geological past. The shallower part of lake sediment core was deposited under similar redox conditions as the Bahamas sediments, and these sediments show an average 238U/235U ratio +0.31 ± 0.01‰ (2SE) higher than seawater. Although the average 238U/235U ratios for these two carbonate rich settings are similar, caution is necessary when inferring seawater 238U/235U compositions from such sediments, as they contain U from different sources (e.g. diagenetic uptake and carbonate-bound). The Mo isotope compositions within the same Malo Jezero sediments are variable but approaches the seawater composition at low pore-water H2S concentrations. This show the potential of using the Mo isotope composition from carbonate rich sediments to infer the seawater composition, however, further work is required to establish the link between the Mo isotope composition and the chemistry of the pore water environment.

Response of Cladocera fauna to environmental change based on sediments from Shengjin Lake, a Yangtze River-connected lake in China

Shengjin Lake is a typical Yangtze River-connected lake, that is also a national nature reserve and a Wetland of International Importance. In order to evaluate the eco-environmental evolution of Shengjin Lake, a210Pb- and 137Cs-dated sediment core collected from the upper part of the lake was analyzed. Based on a biological indicator (subfossil cladoceran) and geochemical indicators (loss on ignition (LOI), total organic carbon (TOC), δ13C of bulk sediments (δ13Corg), total phosphorous (TP) and total nitrogen (TN)), we revealed the changes in the cladoceran assemblages and eco-environmental processes of Shengjin Lake. The results showed that there was a healthy ecological environment with low nutrient levels in Shengjin Lake before the 1980s. However, the increasing levels of the eutrophic species B. longirostris, nutrients (TN and TP) and organic matters (LOI and TOC), and the decreasing δ13Corg in recent decades indicated that the trophic state of Shengjin Lake has increased since the 1980s. This corresponded with increasing anthropogenic effects, including land reclamation, chemical fertilizer application, and sluice construction. In addition, the droppings of water birds also promoted increases in nutrient and organic matters levels in Shengjin Lake.

Transformation of sulfur species in lake sediments at Ardley Island and Fildes Peninsula, King George Island, Antarctic Peninsula

In Antarctica, penguins transport sulfur and other bio-elements in the form of guano from marine to terrestrial environments where they become deposited in ornithogenic soils and sediments, including lake or pond systems. Transformation of sulfur species in these terrestrial and aquatic deposits, however, has rarely been studied. Here, we used the cold diffusion method to analyze various sulfur species in a lake deposit of ornithogenic sediment core (C1) and a pristine lake sediment core (C2), collected from Ardley Island and Fildes Peninsula, Antarctic Peninsula, respectively. The total organic carbon, total phosphorus, total nitrogen and various sulfur species in C1 were more fluctuant and much higher than those in C2, indicating a primary source from penguin guano. In core C1, organic sulfur (Org-S) was the main form of sulfur, and sulfate (SO42−) was the main form of inorganic sulfur. The acid volatile sulfur (AVS) in C1 was much higher than pyrite sulfur (CRS). In the pristine lake sediment core C2, Org-S and SO42− were the main sulfur species. CRS was the primary form of reduced inorganic sulfur in C2 sediments in contrast to the AVS in C1, indicating that AVS had been effectively transformed into CRS in C1. Our results demonstrate that the high levels of organic matter in C1 likely limited the transformation of AVS to CRS.

A bat guano deposit in Jamaica recorded agricultural changes and metal exposure over the last >4300 years

Bats are excellent ecological indicators because they are long-lived, globally distributed, and show predictable responses to environmental stressors. Unaltered bat guano deposits, although rare, can serve as environmental archives to reveal changes in dietary patterns over millennial time scales. We inferred changes in agricultural and industrial practices using a continuous 4300-year-old bat guano deposit from Jamaica. Cadmium, mercury, lead, and zinc increased during the Industrial Revolution, (which began in ca. 1760), a period characterized by elevated emissions of metals to the atmosphere. Beginning in the early 20th century, decreases in 206Pb/207Pb isotopes tracked the history of leaded gasoline use. Metal concentrations in the bat guano deposit exceeded those recorded in two nearby lake sediment cores from Jamaica. Carbon, nitrogen, and sulfur stable isotope profiles in bat guano tracked the agricultural history of Jamaica, specifically the introduction of nitrogen fertilizers, sugarcane, and possibly fungicides. Bat populations are under stress globally, and such intact guano deposits provide potentially critical information on long-term changes in their food source and exposure to metals.

A multi-proxy μ-XRF inferred lake sediment record of environmental change spanning the last ca. 2230 years from Lake Kanono, Northland, New Zealand

Reliable interpretation of annual-resolution climate proxies for wind, precipitation, and detrital influx are required for identifying the onset and periodicities of climatic events. In particular, this is essential for the evaluation of inter-annual, decadal, and centennial trends driven by shifting positions of the Southern Westerly Winds (SWW) and subsequent storm belts associated with the Southern Annular Mode (SAM) and El Niño Southern Oscillation (ENSO). Here we present a quasi-annual data set of μ-XRF time series spanning ca. 2230 years from lake sediment cores from Lake Kanono, Northland, New Zealand. The μ-XRF time series were interpreted using a combination of principal component analysis (PCA) and cluster analysis, then verified with comparison to regionally averaged empirical rainfall and wind climate station data. Our results show that the wavelet patterns align with the PCA results allowing the μ-XRF time series to be classified into: Group I (detrital) and Group II (biological productivity and normalized climate proxies). The normalized Group II μ-XRF time series wavelet analyses displayed periodicities in the 2–16 year frequency, likely associated with ENSO, from ca. 237 BCE – 1330 CE. The data show clear evidence of both Polynesian and European settlement phases in this part of northern New Zealand, and that Polynesian settlement impact was coeval with changes in ENSO intensity and a phase shift in SAM ca. 1350 CE. The Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) appear in the μ-XRF time series data as separate clusters. This data suggests that the MCA is associated with windy/dry conditions with intermittent storminess. During the LIA, the 2–16 year periodicity associated with ENSO decreased and centennial to multi-decadal length periodicities increase, which may be an indication of an underlying SAM signal within the data. European settlement also had a direct impact on the lake basin via increased detrital influx, likely from farming activities and intensification of local forestry operations.

Sublacustrine geomorphology and modern sedimentation in a glacial scour basin, June Lake, eastern Sierra Nevada, U.S.A.

ABSTRACTSmall sub-alpine glacial lakes are often targeted as Holocene paleoclimate archives, but their evolution as landforms and depositional basins is understudied. At June Lake in the eastern Sierra Nevada of California (USA), bathymetry, surface sediment composition, and seismic stratigraphy are studied to assess the modern sedimentary system and gain insight into the basin's origins. A basin-wide seismic survey reveals sublacustrine morphological features that attest to the role of ice in scouring the June Lake basin, including a prominent abraded bedrock shoal and an adjacent overdeepened depression. The seismic survey reveals four acoustically distinct stratigraphic units that reflect the history of sedimentation following glacial scouring. The youngest of these is represented in the recovered lacustrine core records as hemipelagically deposited, organic-rich, laminated diatomaceous oozes alternating with coarse tephra beds. The organic-rich oozes are characterized by low carbon and nitrogen stable-isotope values and occur in profundal areas of the modern lake floor. These sediments suggest an algae-dominated productivity regime and preservation of organic matter at depth. With no perennial streams entering June Lake, surface-sediment grain-size distribution and geochemistry are controlled by water depth and basin morphology. Additional modern facies types include poorly sorted coarse detrital landslide deposits below steep basin walls and volcaniclastic sandy gravel in windward littoral areas. These data provide a modern facies model for sedimentation in ice-scoured, hydrologically closed sub-alpine lakes and a baseline for future paleoclimate studies using June Lake sediment cores.

Spatial distribution of environmental indicators in surface sediments of Lake Bolshoe Toko, Yakutia, Russia

Abstract. Rapidly changing climate in the Northern Hemisphere and associated socio-economic impacts require reliable understanding of lake systems as important freshwater resources and sensitive sentinels of environmental change. To better understand time-series data in lake sediment cores, it is necessary to gain information on within-lake spatial variabilities of environmental indicator data. Therefore, we retrieved a set of 38 samples from the sediment surface along spatial habitat gradients in the boreal, deep, and yet pristine Lake Bolshoe Toko in southern Yakutia, Russia. Our methods comprise laboratory analyses of the sediments for multiple proxy parameters, including diatom and chironomid taxonomy, oxygen isotopes from diatom silica, grain-size distributions, elemental compositions (XRF), organic carbon content, and mineralogy (XRD). We analysed the lake water for cations, anions, and isotopes. Our results show that the diatom assemblages are strongly influenced by water depth and dominated by planktonic species, i.e. Pliocaenicus bolshetokoensis. Species richness and diversity are higher in the northern part of the lake basin, associated with the availability of benthic, i.e. periphytic, niches in shallower waters. δ18Odiatom values are higher in the deeper south-western part of the lake, probably related to water temperature differences. The highest amount of the chironomid taxa underrepresented in the training set used for palaeoclimate inference was found close to the Utuk River and at southern littoral and profundal sites. Abiotic sediment components are not symmetrically distributed in the lake basin, but vary along restricted areas of differential environmental forcing. Grain size and organic matter are mainly controlled by both river input and water depth. Mineral (XRD) data distributions are influenced by the methamorphic lithology of the Stanovoy mountain range, while elements (XRF) are intermingled due to catchment and diagenetic differences. We conclude that the lake represents a valuable archive for multiproxy environmental reconstruction based on diatoms (including oxygen isotopes), chironomids, and sediment–geochemical parameters. Our analyses suggest multiple coring locations preferably at intermediate depth in the northern basin and the deep part in the central basin, to account for representative bioindicator distributions and higher temporal resolution, respectively.

Source apportionment of priority PAHs in 11 lake sediment cores from Songnen Plain, Northeast China

Elevated concentrations of polycyclic aromatic hydrocarbons (PAHs) have been observed with rapid agricultural and industrial development in the Songnen Plain, Northeast China, but the prospective sources have not been yet apportioned. The concentration of PAHs was measured in 31 sediment samples from 11 Songnen Plain lakes in 2015. The background flux of PAHs in these lake sediments is < 463 μg m−2 year−1. The maximal concentration of 16 U.S. EPA priority PAHs (599 ng g−1) recorded in this study is lower or similar to that found in most of the lake sediments across China, but higher than remote areas, such as North America Rocky Mountains. Both concentration and flux of PAHs increased after the 1950s, which correspond to the industrial development in this area and would probably mark the beginning of the Anthropocene in this region. A chemical mass balance model estimated that straw burning was a major source of Σ13PAH (3–6 rings) during the past 200 years, with an average contribution of 22.1%, followed by forest fire (21.2%), burning of gasoline (19.1%), coal (12.2%), coke (4.8%) and diesel (3.9%), whereas the contribution from crude oil and natural gas was negligible (<1%). Straw burning (20.2–25.2%) and forest fire (16.7–30.6%) were major sources of PAHs and contributed increasing flux in the past 200 years. The elevated level of PAH recorded after 1950s in this region are also from burning of gasoline (26.1–26.4%), coal (15.3–15.8%), and coke (5.1–9.0%). The contribution of petrogenic sources (e.g., direct oil spill) to the concentration of Σ13PAH seemed to be ignorable, at least in these lakes.

Distribution of Organochlorine Pesticide and Polychlorinated Biphenyl Residues in Lake Sediment Cores from the Plitvice Lakes National Park (Croatia)

The occurrence and distribution of 11 organochlorine pesticides (OCPs) and their degradation products as well as of 17 polychlorinated biphenyl congeners (PCBs) were investigated for the first time in sediments of three (Lake Prošće, Lake Kozjak, Lake Kaluđerovac) out of 16 cascading karst lakes within the protected area of the Plitvice Lakes National Park in central Croatia. The 15-cm-long sediment cores were divided for analysis into three 5-cm-long segments. The abundance and levels of sediment-associated OCPs and PCBs were evaluated with respect to sampling location and sediment depth, presumed age of deposition, and organic carbon content. The burden of sediments with OCPs and PCBs decreased downstream with the highest mass fractions measured in the uppermost Lake Prošće (total OCPs 2.72-5.86μgkg-1d.m., total PCBs 0.37-1.78µgkg-1d.m.) and the lowest in Lake Kaluđerovac (total OCPs 0.30-0.58μgkg-1d.m., total PCBs 0.07-0.12µgkg-1d.m.). The predominant organochlorine pollutants were DDT-type compounds (total DDX, w = 0.30-5.72µgkg-1d.m.) with p,p'-DDE and p,p'-DDD accounting for up to 100% and 50%, respectively, of the total DDX. The findings indicated an old input of p,p'-DDT that largely converted to its degradation products. The OCP and PCB mass fractions in the Plitvice lake sediments were at trace levels characteristic for preserved pristine natural environments with no or limited anthropogenic impact wherein long-range atmospheric transport is considered as their main source.

Lake Onego development in the late glacial assessed with the use of GIS technologies

The GIS-based reconstructions of Lake Onego development in the Late Glacial (14500–12300 yrs ago) were performed. Reconstructions have been based on the deglaciation model of the Lake Onego depression, digital elevation model of the lake depression, SRTM model of its drainage basin and on the data obtained from the palaeolimnological studies of numerous lake sediment cores. This allowed us to distinguish six main stages of the lake development for which a series of detailed schemes were produced. 1. Formation of the ice-dammed lake as a result of the ice sheet retreating (14.5 cal ka BP). 2. Emerging of the southern and central parts of the lake basin from the ice cover (14.0 cal ka BP). 3. The maximum development of the proglacial lake (13.3 cal ka BP). The lake area in this period was around 33 000 km2. 4. The first regression (13.2 ka BP). 5. The second regression (12.4 ka BP). 6. The third regression (12.3 ka BP), when the area of the lake dropped to 18 000 km2. We created detailed digital maps of the main stages of Lake Onego development during the Late Glacial and calculated the spatial parameters of the lake. The quantitative data obtained in this study would be used in estimation of the volumes of the lake and outflow discharges in the past. Maps are available in electronic form.