A late Quaternary lake record from the Qilian Mountains (NW China): evolution of the primary production and the water depth reconstructed from macrofossil, pollen, biomarker, and isotope data

The history (45–0 ka BP) of the aquatic vegetation composition of the shallow alpine Lake Luanhaizi from the NE Tibetan Plateau is inferred from aquatic plant macrofossil frequencies and aquatic pollen and algae concentrations in the sediments. C/N (range: 0.3–100), δ¹³C (range: −28 to −15‰), and n-alkane measurements yielded further information on the quantitative composition of sedimentary organic matter. The inferred primary production of the former lake ecosystem has been examined in respect of the alternative stable state theory of shallow lakes [Scheffer, M., 1989. Alternative stable states in eutrophic, shallow freshwater systems: a minimal model. Hydrobiological Bulletin 23, 73–83]. Switches between clear and turbid water conditions are explained by a colder climate and forest decline in the catchment area of Lake Luanhaizi. The macrofossil-based reconstruction of past water depth and salinity ranges, as well as other organic matter (OM) proxies allowed climatic inferences of the summer monsoon intensity during the late Quaternary. Around 45 ka BP, conditions similar to or even moister than present-day climate occurred. The Lake Luanhaizi record is further evidence against an extensive glaciation of the Tibetan Plateau and its bordering mountain ranges during the Last Glacial Maximum. Highest lake levels and consequently a strong summer monsoon are recorded for the early Holocene period, while gradually decreasing lake levels are reconstructed for the middle and late Holocene.     

Comparing Eulerian and Lagrangian eddy census for a tide-less,semi-enclosed basin,the Baltic Sea

Ocean Dynamics - Eddies in the global and coastal ocean play a key role in mixing and transport processes. Here, we present an eddy census for the Baltic Sea covering the years 2008–2010. The...     

The influence of climate on water chemistry states and dynamics in rivers across Australia

For effective water quality management and policy development, spatial variability in the mean concentrations and dynamics of riverine water quality needs to be understood. Using water chemistry (calcium, electrical conductivity, nitrate-nitrite, soluble reactive phosphorus, total nitrogen, total phosphorus and total suspended solids) data for up to 578 locations across the Australian continent, we assessed the impact of climate zones (arid, Mediterranean, temperate, subtropical, tropical) on (i) inter-annual mean concentration and (ii) water chemistry dynamics as represented by constituent export regimes (ratio of the coefficients of variation of concentration and discharge) and export patterns (slope of the concentration-discharge relationship). We found that inter-annual mean concentrations vary significantly by climate zones and that spatial variability in water chemistry generally exceeds temporal variability. However, export regimes and patterns are generally consistent across climate zones. This suggests that intrinsic properties of individual constituents rather than catchment properties determine export regimes and patterns. The spatially consistent water chemistry dynamics highlights the potential to predict riverine water quality across the Australian continent, which can support national riverine water quality management and policy development.     

Einsatz von Pflanzenkläranlagen zur Behandlung von schadstoffbelastetem Oberflächenabfluß städtischer Straßen

A combination of retention pond and reed bed was tested for its effectiveness in reducing non-point source runoff pollution from an urban area. This paper presents data on the development of reed plants (Phragmites australis Cav. Trin.), on the effectiveness of runoff purification and on the accumulation of contaminants in the pond sediment and the reed bed for the years 1993–1995. P. australis was well established and grew according to normal development. The measured length and biomass values of P. australis were larger on sand than on gravel and coarse materials. Toxic levels of heavy metals in the plants were not reached. Harvested plants can be composted. The purification system is effective within the following ranges: The rate of retention of suspended solids and heavy metals varies between 16% and 91%. For chemical oxygen demand the average values is 25%. Poor retention rates usually occur along with very low input concentrations. Generally retention within the reed bed is higher than in the pond. Between 1993 and 1995 the concentration of contaminants within the organic layer of the reed bed increased by 50% for lead and by 90% for poly aromatic hydrocarbons. Until 1994 the concentrations of mineral oil hydrocarbons also increased by 60%. Between 1994 and 1995 however the concentration of mineral oil hydrocarbons in the reed bed decreased rapidly by more than 50%: Mineral oil hydrocarbons underlie biological degradation within the reed bed. In the pond sediment a significant accumulation of heavy metals, poly aromatic hydrocarbons and mineral oil hydrocarbons has also been found. The concentrations of these contaminants are still far from inhibiting the function of the system.     

Geostandards and Geoanalytical Research Bibliographic Review 2019

This bibliographic review gives an outline of publications in 2019 focusing on reference materials (RMs) used in geochemistry and related fields, such as palaeoclimate and environmental research.     

Genetic implications of new lead isotope measurements on Schwarzwald vein and Upper Triassic sediment galenas

We report the results of a lead isotopic investigation of galena from vein deposits from the Southern Schwarzwald (33 samples) and from various localities (6) from the galena horizon of the South German Keuper. The total range of isotopic ratios for the veins and the Keuper leads is:18,29 <²⁰⁶Pb/²⁰⁴Pb < 18,97; 15,59 <²⁰⁷Pb/²⁰⁴Pb < 15,70; 38,42 <²⁰⁸Pb/²⁰⁴Pb < 38,90. The lead isotopic systems give anomalous ages when compared with lead evolution models ofHolmes (1946, 47)Houtermans (1946),Stacey &Kramers (1975) andCumming &Richards (1975). This indicates a more complex lead evolution than allowed for in these models.Small but significant variations in the isotopic ratios of lead were observed in galenas from within a number of veins and between veins. Also leads in galena from Hercynian veins within granitic host rocks in the Southern Schwarzwald were found to be more radiogenic than galena leads in veins found in gneisses in the Central Schwarzwald. These results strongly suggest a local influence on the lead isotopic compositions of the vein galenas and also place constraints on the age of the veins and models of vein formation.Galenas from Tertiary veins were found to have lower²⁰⁷Pb/²⁰⁴Pb ratios in comparison with ratios observed in Hercynian vein leads, suggesting that the Tertiary veins contain a compound of older retarded lead from a source not identified in the present study.The Keuper sedimentary galenas were found to have relatively homogenous lead isotopic ratios which fall within the range of isotopic compositions of the Hercynian vein leads. The galenas from the Upper Triassic (Keuper) are slightly more radiogenic than the more isotopically variable galena leads from the uppermost Permian (Kupferschiefer;Wedepohl et al. 1978).

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Zusammenfassung An Bleiglanzen von Gängen des mittleren und südlichen Schwarzwaldes (33 Proben) und von verschiedenen Lokalitäten (6) der Bleiglanzbank des süddeutschen Keupers wurden massenspektrometrische Blei-Isotopen-Untersuchungen durchgeführt.Die Werte fallen in die Bereiche: 18,29 <²⁰⁶Pb/²⁰⁴Pb < 18,97; 15,59 <²⁰⁷Pb/²⁰⁴Pb < 15,70; 38,42 <²⁰⁸Pb/²⁰⁴Pb < 38,90. Aus den Blei-Isotopenverhältnissen erhält man anomale Blei-Entwicklungsalter, wenn man die Modellevon Holmes (1946, 47),Houtermans (1946),Stacey &Kramers (1975) undCumming &Richards (1975) zugrunde legt. Das zeigt, daß die Entwicklung dieses Bleis komplexer ablief, als die genannten Modelle annehmen.Kleine aber signifikante Unterschiede in der Blei-Isotopenzusammensetzung wurden für Proben eines Gangsystems und zwischen den verschiedenen Gängen beobachtet. Das Blei aus Bleiglanzen von variscischen Gängen des St. Blasien-Granits (Südostschwarzwald) ist radiogener als das der Gänge in den Gneisen des Zentral-Schwarzwaldes. Diese Beobachtung zeigt, daß die Blei-Isotopenwerte mit der lokalen geologischen Situation verknüpft sind und ist von Bedeutung für die Diskussion der Alter und Entstehungs-modelle der Bleiglanze.Bleiglanz aus den als Tertiär angesehenen Gängen zeigt niedere²⁰⁷Pb/²⁰⁴-Verhältnisse als die variscischen Gang-Bleiglanze. Daraus kann man auf eine ältere zurückgebliebene Bleikomponente schließen, deren Quelle jedoch noch nicht gefunden wurde. Die Bleiglanze aus der Keuper-Bleiglanzbank ergaben relativ einheitliche Isotopenverhältnisse, welche in die Verteilung der Schwarzwälder Bleie fallen. Sie sind etwas radiogener als die isotopisch sehr variablen Bleiglanz-Isotopenwerte des Zechsteins (Kupferschiefer;Wedepohl et al. 1978).

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Résumé Une étude isotopique du plomb a été effectué sur des galènes provenant de filons de la Forêt Noire Centrale et du Sud (33 échantillons) et de différentes localités (6) de l'horizon à galène du Keuper du Sud de l'Allemagne.Les valeurs de plomb se situent dans les intervalles suivants: 18,29 <²⁰⁶Pb/²⁰⁴Pb < 18,97; 15,59 <²⁰⁷Pb/²⁰⁴Pb < 15,70; 38,42 <²⁰⁸Pb/²⁰⁴Pb < 38,90.Les rapports isotopiques du plomb indiquent des âges d'évolution de plomb anormaux, si l'on prend pour base les modèles d'évolution deHolmes (1946, 47),Houtermans (1946),Stacey &Kramers (1975) etCumming &Richards (1975). Cela montre que l'évolution du plomb s'est déroulée d'une façon plus complexe que ne le supposent les modèles mentionnés. Des différences minimes mais significatives ont été observées dans la composition isotopique du plomb, pour des échantillons d'un système filonien et entre différents filons. Le plomb des galènes des filons hercyniens du granite de St. Blasien (Forêt Noire du Sud Est) est plus radiogénique que celui des filons trouvés dans les gneiss de la Forêt Noire Centrale. Cette observation montre que la composition isotopique du plomb est liée à la situation géographique locale et est d'une grande importance pour la discussion des âges et des modèles de formation des galènes.Les rapports²⁰⁷Pb/²⁰⁴Pb des galènes des filons considérés comme d'âge tertiaire sont moins élevés que ceux des galènes d'âge hercynien, ce qui permet de supposer une composante de plomb plus âgée, «retardée» dont on n'a pu jusqu'ici déceler la source. Le plomb des galènes du Keuper a une composition isotopique relativement homogène, qui se trouve dans la gamme de celle observée pour le plomb des galènes de la Forêt Noire. Leur plomb est légèrement plus radiogénique que celui des galènes du Zechstein qui a une composition isotopique très variable (Kupferschiefer;Wedepohl et al., 1978).

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— (33 ) (6 ) - . : 18,29 <²⁰⁶Pb/²⁰⁴Pb < 18,97; 15,59 <²⁰⁷Pb/²⁰⁴Pb < 15,70; 38,42 <²⁰⁸Pb/²⁰⁴Pb < 38,90. , Holmes'a, 1946; Houterman'a, 1946, Stacey & Kramer'a, 1975 Cumming & Richard'a, 1975, . , , , ., , . St. Blasien (- ) , . , , . ²⁰⁷Pb/²⁰⁴Pb, . , . , . , , .

     

An ostracod-conductivity transfer function for Tibetan lakes

About 145 freshwater to hypersaline lakes of the eastern Tibetan Plateau were investigated to develop a transfer function for quantitative palaeoenvironmental reconstructions using ostracods. A total of 100 lakes provided sufficient numbers of ostracod shells. Multivariate statistical techniques were used to analyse the influence of a number of environmental variables on the distributions of surface sediment ostracod assemblages. Of 23 variables determined for each site, 19 were included in the statistical analysis. Lake water electrical conductivity (8.2%), Ca% (7.6%) and Fe% (4.8%, ion concentrations as % of the cations) explained the greatest amounts of variation in the distribution of ostracod taxa among the 100 lakes. Electrical conductivity optima and tolerances were calculated for abundant taxa. A transfer function, based on weighted averaging partial least squares regression (WA-PLS), was developed for electrical conductivity (r ² = 0.71, root-mean-square-error of prediction [RMSEP] = 0.35 [12.4% of gradient length], maximum bias = 0.64 [22.4% of gradient length], as assessed by leave-one-out cross-validation) based on 96 lakes. Our results show that ostracods provide reliable estimates of electrical conductivity and can be used for quantitative palaeoenvironmental reconstructions similarly to more commonly used diatom, chironomid or pollen data.     

Subfossil Cladocera from surface sediment in thermokarst lakes in northeastern Siberia,Russia, in relation to limnological and climatic variables

Subfossil Cladocera were sampled and examined from the surface sediments of 35 thermokarst lakes along a temperature gradient crossing the tree line in the Anabar-river basin in northwestern Yakutia, northeastern Siberia. The lakes were distributed through three environmental zones: typical tundra, southern tundra and forest tundra. All lakes were situated within the continuous permafrost zone. Our investigation showed that the cladoceran communities in the lakes of the Anabar region are diverse and abundant, as reflected by taxonomic richness, and high diversity and evenness indices (H = 1.89 ± 0.51; I = 0.8 ± 0.18). CONISS cluster analysis indicated that the cladoceran communities in the three ecological zones (typical tundra, southern tundra and forest-tundra) differed in their taxonomic composition and structure. Differences in the cladoceran assemblages were related to limnological features and geographical position, vegetation type, climate and water chemistry. The constrained redundancy analysis indicated that T_July, water depth and both sulphate (SO₄ ^2?) and silica (Si⁴⁺) concentrations significantly (p ≤ 0.05) explained variance in the cladoceran assemblage. T_July featured the highest percentage (17.4 %) of explained variance in the distribution of subfossil Cladocera. One of the most significant changes in the structure of the cladoceran communities in the investigated transect was the replacement of closely related species along the latitudinal and vegetation gradient. The results demonstrate the potential for a regional cladoceran-based temperature model for the Arctic regions of Russia, and for and Yakutia in particular.     

Biomarker and compound-specific δ<Superscript>13</Superscript>C evidence for changing environmental conditions and carbon limitation at Lake Koucha,eastern Tibetan Plateau

A sediment core from Lake Koucha (eastern Tibetan Plateau) was investigated using organic biomarkers and their stable carbon isotope signatures. The correlation between TOC content, total amount of aquatic macrophyte-derived n-alkanes (e.g. nC₂₃) and δ¹³C values of TOC and nC₂₃ indicates that Lake Koucha was macrophyte-dominated before 8 cal ka BP. Shortly after the lake turned from a saline to a freshwater system at 7.2 cal ka BP, a variety of algal and bacterial markers such as hopanoids and isoprenoids emerged, of which phytane, pentamethylicosene (PMI), moretene and diploptene are particularly abundant. Phytane and PMI show different isotopic signals (≈−18 and ≈−28‰, respectively), which indicates that they originated from different sources. Phytane may have been derived from cyanobacteria, while methanogenic archaea may be the source of PMI. The isotopic depletion of diploptene and moretene (≈−60‰) indicates the presence of methanotrophs. After 6.1 cal ka BP, the saturated C₂₀ highly branched isoprenoid (HBI) became the dominant constituent of the aliphatic hydrocarbon fraction. Such dominance has rarely been reported in lacustrine environments, and indicates a strong presence of algae (most likely diatoms) or cyanobacteria. At 4.7 cal ka BP, the appearance of an unsaturated C₂₅ HBI, which is a specific biomarker for diatoms, was noted. Furthermore, the level of nC₁₇-alkane was observed to increase in abundance in the uppermost two samples. These results suggest that the lake was phytoplankton-dominated during the last 6.1 ka. Relatively low biomarker concentrations and δ¹³C values at 6.0, 3.1 and 1.8 cal ka BP indicate the occurrence of cool periods, which is in agreement with inferences from other locations on the Tibetan Plateau. The δ¹³C values of nC₂₃ range from −23.5 to −12.6‰, with high values at the peak of macrophyte abundance at ca. 11 cal ka BP and at the phytoplankton maximum between ca 6.1 and 2.8 cal ka BP. Thus, aquatic macrophyte-derived mid-chain n-alkanes have been found to be excellent indicators of carbon-limiting conditions, which lead to the assimilation of isotopically-enriched carbon species. The limitation of carbon sources could be a localized phenomenon occurring in dense plant stands (as in the older section of the core), or it may be induced by high primary productivity (as in the younger section). Since the δ¹³C value of the inorganic carbon source may vary, the offset between the δ¹³C values of nC₂₃ and TIC could serve as a more precise proxy for carbon-limiting conditions in lacustrine environments, which could in turn be interpreted with respect to lacustrine paleo-productivity.