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(searched for: doi:10.1016/j.scitotenv.2017.08.148)
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International Journal of Environmental Research and Public Health, Volume 20; https://doi.org/10.3390/ijerph20020935

Abstract:
Chemical analysis was performed on sediment core samples collected from three salt lakes, Amara Lake, Caineni Lake, and Movila Miresii Lake, located in the northeast of the Romanian Plain. The concentration of 10 main elements, 6 heavy metals (HMs), 8 rare earth elements (REEs), and 10 trace elements (TEs)—determined using neutron activation analysis (NAA)—showed variability dependent on the depth sections, lake genesis and geochemical characteristics (oxbow, fluvial harbor/liman and loess saucer type). The assessment of pollution indices (contamination factor, pollution load index, geoaccumulation index, and enrichment factor) highlighted low and moderate degrees of contamination for most of the investigated elements. Principal component analysis (PCA) extracted three principal components, explaining 70.33% (Amara Lake), 79.92% (Caineni Lake), and 71.42% (Movila Miresii Lake) of the observed variability. The principal components extracted were assigned to pedological contribution (37.42%—Amara Lake, 55.88%—Caineni Lake, and 15.31%—Movila Miresii Lake), salts depositions (due to the lack of a constant supply of freshwater and through evaporation during dry periods), atmospheric deposition (19.19%—Amara Lake, 13.80%—Caineni Lake, and 10.80%—Movila Miresii Lake), leaching from soil surface/denudation, rock weathering, and mixed anthropogenic input (e.g., agricultural runoff, wastewater discharges) (13.72%—Amara Lake, 10.24%—Caineni Lake, and 45.31%—Movila Miresii Lake).
, , N. M. Kehrwald, , , S. Hanif, E. O. Erhenhi, J. M. Ramirez Aliaga, D. B. McWethy, A. E. Myrbo, et al.
Published: 13 October 2021
Journal: PLOS ONE
Abstract:
Rano Raraku, the crater lake constrained by basaltic tuff that served as the primary quarry used to construct themoaistatues on Rapa Nui (Easter Island), has experienced fluctuations in lake level over the past centuries. As one of the only freshwater sources on the island, understanding the present and past geochemical characteristics of the lake water is critical to understand if the lake could have been a viable freshwater source for Rapa Nui. At the time of sampling in September 2017, the maximum lake depth was ~1 m. The lake level has substantially declined in the subsequent years, with the lake drying almost completely in January 2018. The lake is currently characterized by highly anoxic conditions, with a predominance of ammonium ions on nitrates, a high concentration of organic carbon in the water-sediment interface and reducing conditions of the lake, as evidenced by Mn/Fe and Cr/V ratios. Our estimates of past salinity inferred from the chloride mass balance indicates that it was unlikely that Rano Raraku provided a viable freshwater source for early Rapa Nui people. The installation of an outlet pipe around 1950 that was active until the late 1970s, as well as grazing of horses on the lake margins appear to have significantly impacted the geochemical conditions of Rano Raraku sediments and lake water in recent decades. Such impacts are distinct from natural environmental changes and highlight the need to consider the sensitivity of the lake geochemistry to human activities.
, Teresa Vegas-Vilarrúbia, Juan Pablo Corella, Mari C. Trapote, Encarni Montoya, Blas Valero-Garcés
Published: 13 August 2021
Quaternary Science Reviews, Volume 268; https://doi.org/10.1016/j.quascirev.2021.107128

The publisher has not yet granted permission to display this abstract.
, Paolo Villa, Gary Free, Claudia Giardino, Mariano Bresciani
Published: 1 January 2021
Journal: Wetlands
Wetlands, Volume 41, pp 1-14; https://doi.org/10.1007/s13157-021-01395-9

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, Cheng Liu, Kai He, Qiushi Shen, Jicheng Zhong
Published: 31 December 2020
Science of the Total Environment, Volume 767; https://doi.org/10.1016/j.scitotenv.2020.144868

Abstract:
Global lakes serve as a key natural source of methane (CH4) and suffer from increasing hypoxia due to unprecedented anthropogenic activities and climate change. A black bloom is a temporary hypoxia triggered by a longstanding algal bloom, which facilitates CH4 production by creating reducing conditions and abundant algae-sourced organic carbon. One-year investigations were conducted to examine temporal CH4 dynamics in the water and sediment pore water in black bloom prone areas (BBPAs) in Lake Taihu, China, where there had been at least two recorded black bloom events. The CH4 in the water changed significantly with time (p < 0.001), with the highest concentrations appearing in warm months when an abnormal lower dissolved oxygen content was observed at different sites, which were one to two orders of magnitude higher than other months. Compared with the control site, there were significantly higher CH4 concentrations in BBPA waters (p < 0.001), which was consistent with the higher CH4 in the sediment pore water. Methane dynamics in the water showed significant positive correlations with temperature, total phosphorus, total nitrogen, ammonia-N, and soluble reactive phosphorus (p < 0.05), but showed a significant inverse correlation with dissolved oxygen (p < 0.01). Redundancy analysis indicated dissolved oxygen made the largest contribution to CH4 dynamics in the BBPAs. A significant increase in the CH4 in water will turn BBPAs into temporary hot spots with substantial CH4 emissions with the appearance of black blooms. The results provide new insights into understanding future CH4 dynamics under globally prevailing algal blooms and climate change.
Published: 31 October 2020
Science of the Total Environment, Volume 755; https://doi.org/10.1016/j.scitotenv.2020.143418

Abstract:
Global spread of anoxia in aquatic ecosystems has become a major issue that may potentially worsen due to global warming. The reconstruction of long-term hypolimnetic anoxia records can be challenging due to lack of valid and easily measurable proxies.
, Sayuri Naito, Hisashi Ikeda, Kuniaki Tanaka, Takuma Murakami, Shinya Ochiai, Yoshiki Miyata, Mayuko Shimizu, Asuka Hayano, Konami Fukui, et al.
Published: 2 October 2020
Quaternary Science Reviews, Volume 248; https://doi.org/10.1016/j.quascirev.2020.106576

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, Pedro Rivas-Ruiz, Maria Del Carmen Trapote, Teresa Vegas-Vilarrúbia, Valentí Rull,
Published: 20 June 2020
Journal: Chemical Geology
Chemical Geology, Volume 551; https://doi.org/10.1016/j.chemgeo.2020.119759

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Published: 19 February 2020
Journal of Paleolimnology, Volume 63, pp 283-304; https://doi.org/10.1007/s10933-020-00116-2

Abstract:
Accurate lake sediment-derived palaeoenvironmental reconstructions require in-depth knowledge on sediment record formation processes. In order to understand formation of laminated sediments in the eutrophic Lake Kierskie (western Poland) we conducted a year-round (November 2015–October 2016), monthly sediment trap study along with physico-chemical water properties, water transparency, hardness, alkalinity, nutrients and solute content, trophic state indices, and the phytoplankton assemblage monitoring. Sedimentation in Lake Kierskie primarily resulted from the activity of photosynthetic organisms. The maxima of biogenic silica accumulation were synchronous with the bloom of centric diatoms observed in March and April. These were followed by the most intensive precipitation of CaCO3 noted between mid-April and mid-June, that corroborated with the domination of Stephanodiscus hantzschii and small flagellate forms acting as nucleation sites for crystal formation. At the same time shift from the diatom-dominated assemblages to the communities composed of chlorophytes, cryptophytes, and dinoflagellates, the groups with cellulose external covering, resulted in decreased proportion between SiO2 and organic matter. CaCO3 precipitation continued in the summer months, however its amount decreased simultaneously with a drop in S. hantzschii biomass. The significant overall flux of biogenically mediated materials from epilimnion was promoted by eutrophic towards hypertrophic conditions in Lake Kierskie revealed by the trophic state indices. Mixing of the water column in autumn triggered resuspension and redeposition of the previously deposited sediments resulting in the second, after the early spring, maximum sediment flux. Minima of sediment accumulation were observed during the winter water stratification when the smallest particles sedimented from suspension. The sediment flux to the lake bottom recorded by us in a 1-year, monthly sediment trap study matches a sequence of pale, whitish lamina deposited during spring and summer, followed by dark, grayish or black lamina deposited in the autumn and winter, observed in the macroscopic investigation of the short (0.5 m) core from Lake Kierskie. Preservation of distinct laminations in the dimictic Lake Kierskie is supported by anoxic hypolimnion developed under the high supply of organic matter from epilimnion of this highly eutrophic lake.
Published: 2 January 2020
by MDPI
Journal: Quaternary
Quaternary, Volume 3; https://doi.org/10.3390/quat3010001

Abstract:
In Quaternary paleosciences, the rationale behind analogical inference presupposes that former processes can be explained by causes operating now, although their intensity and rates can vary through time. In this paper we synthesised the results of different modern analogue studies performed in a varved lake. We discuss their potential value to obtain best results from high resolution past records. Different biogeochemical contemporary processes revealed seasonality and year-to-year variability, e.g., calcite precipitation, lake oxygenation, production and deposition of pollen and phytoplankton growth. Fingerprints of the first two of these processes were clearly evidenced in the varve-sublayers and allow understanding related to past events. Pollen studies suggested the possibility of identifying and characterizing seasonal layers even in the absence of varves. Marker pigments in the water column were tightly associated with phytoplankton groups living today; most of them were identified in the sediment record as well. We observed that 50% of these marker pigments were destroyed between deposition and permanent burying. In another study, seasonality in the production/distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs) and derived temperature estimates were investigated in catchment soils and particles settling in the lake. The signatures of brGDGTs in depositional environments mainly were representative of stable conditions of soils in the catchment that last over decades; no brGDGTs seemed to be produced within the lake. The main contribution of this review is to show the advantages and limitations of a multiproxy modern-analogue approach in Lake Montcortès as a case study and proposing new working hypotheses for future research.
, J. Tibby, L.J. Arnold, C. Barr, P.S. Gadd, J.C. Marshall, G.B. McGregor, G.E. Jacobsen
Published: 19 November 2019
Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 538; https://doi.org/10.1016/j.palaeo.2019.109463

The publisher has not yet granted permission to display this abstract.
Published: 1 August 2019
Science of the Total Environment, Volume 694; https://doi.org/10.1016/j.scitotenv.2019.133690

Abstract:
This study proposes a novel framework to accurately estimate water quality profiles in deep lakes based on parameters measured at the water surface, considering Boulder Basin of Lake Mead as a case study. Hourly-measured meteorological data were used to compute heat exchange between lake and atmosphere. Heat fluxes combined with every 6-hour measured water temperature, conductivity, and dissolved oxygen (DO) profiles, from the water surface to a depth of 100 m over a 48-month period, were used to train seven different artificial neural network-based methods for estimating water quality profiles. Effects of different factors influencing lake water quality, including lake-atmosphere interactions, wind-induced mixing, thermocline depth, winter turnover, oxygen depletion and other factors were investigated in different methods. A method employing stationary wavelet transform with a depth-progressive estimation of temperature, conductivity, and DO generated the smallest average relative errors of 0.52%, 0.22%, and 0.62%, respectively in the water column over a 48-month period. Abrupt changes in temperature, conductivity, and DO profiles due to thermal stratification, winter turnover, and oxygen hypoxia increased estimation errors. The largest errors occurred near the interface between the epilimnion and metalimnion, where vertical mixing intensity significantly decreased.
, Ludvig Löwemark, Rik Tjallingii, Bernd Zolitschka
Published: 5 April 2019
Quaternary International, Volume 514, pp 5-15; https://doi.org/10.1016/j.quaint.2019.04.002

The publisher has not yet granted permission to display this abstract.
Published: 6 December 2018
Science of the Total Environment, Volume 657, pp 585-596; https://doi.org/10.1016/j.scitotenv.2018.12.078

Abstract:
This study explores the long-term drivers of changes in lake mixing regime and the causes of lacustrine anoxia in the 2000 year-long, varved sediment record from Lake Żabińskie in northeastern Poland. Annually resolved geochemical data (μXRF and CNS) and pollen data were used to find links between changes in catchment land use and lake mixing regime. Furthermore, we tested the applicability of the Fe/Mn ratio for the reconstruction of past water ventilation. Multivariate statistical analyses show that Fe and Mn were mostly independent of terrestrial inputs and lake trophy, meaning that the Fe/Mn ratio mainly responded to changes in redox potential in hypolimnetic waters. Characteristic changes of the Fe/Mn ratio corresponded to transformations of woodland cover in the catchment as registered by changes of the arboreal/non-arboreal pollen ratio. Six main phases of different lake mixing intensity were distinguished. The local landscape was more open during phases of intensified human impact and catchment deforestation, leading to the intensification of lake mixing. At times of negligible human impact, the catchment was mostly wooded, and thus the lake was well sheltered from intense wind-driven mixing. This led to periods of prolonged anoxia. The Fe/Mn record accurately traced past changes in lake mixing intensity and related shifts in water column oxygenation. During the last two millennia, the mixing regime of Lake Żabińskie mostly depended on human activity in the catchment and landscape openness, while long periods of anoxia were not exclusive to only the most recent sediments.
Monica Pinardi, , Paolo Villa, Ilaria Cazzaniga, , Viktor Tóth, , Martina Austoni, , Claudia Giardino
Published: 1 September 2018
Journal: Limnologica
Limnologica, Volume 72, pp 32-43; https://doi.org/10.1016/j.limno.2018.08.002

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