The long-term accumulation, burial and release of nutrients, such as carbon (C), nitrogen (N), and phosphorus (P) in lacustrine sediments are responsible for the global lake eutrophication. Interpretation of the spatiotemporal sedimentary record of nutrients (C, N, and P) in contrasting trophic level of lakes is helpful for understanding the evolutionary process of water eutrophication. Based on the radiochronology of 210Pbex and 137Cs, a comparative study of spatial and temporal concentrations, burial of total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP), the sources of organic matter were conducted using sediment cores from two plateau lakes Dianchi (DC) and Fuxian (FX) of SW China. Results showed that concentrations and burial of C, N, and P in sediments of DC, a shallow hypertrophic lake with the maximum depth of 5.8 m, were both higher than those in FX, an oligotrophic deep lake with the maximum depth of 155.0 m. For both lakes the molar ratio of TOC/TN increased in the sediments moving from north to south. The values of TOC/TN molar ratios increased over time in DC and were higher than in FX. The extremely high values of TOC/TN appeared in the central and southern parts of FX, indicating the impacts of accumulation effect and sediment focusing in the deeper region and indirect supplement from the Lake Xingyun (XY), an adjoining lake connected with FX via the Gehe River. Time-integrated sources identification in DC indicated the contribution of allochthonous sources was dominant over the past few decades, which contributed to the increased trophic level of the lake. The comparison of relationships of carbon accumulation rates (CAR), nitrogen accumulation rates (NAR), and phosphorous accumulation rates (PAR), the ratios of N/P and the utilizations of N and P fertilizer between DC and FX implied that both of N and P inputs should be limited for reducing the trophic level, but N control was predominant in comparison with P for both lakes. The results indicated that caution is required in plateau lakes to limit transition from oligotrophic to eutrophic in these lakes.

Metal contamination has become an increasingly severe environmental issue due to intense anthropogenic activities in recent decades. Many studies have reported a rapidly increasing trend of heavy metal contents in sedimentary records. In this study, two lacustrine sediment cores (LDL and YL) far away from scientific research stations were collected in Ny-Ålesund and analyzed for the vertical distributions of 17 elemental concentrations (Cu, Zn, Pb, Co, Ni, Cr, Sr, Ba, Mn, P, Ti, K2O, Na2O, CaO, MgO, Fe2O3, Al2O3), CIA and TOC contents. The results indicated that only the proxies Pb, P, CaO, TOC, and CIA showed an increasing trend in the upper 7 cm section of the sediment cores, while most of the elements\' concentrations decreased towards the surface. The rapid increase of TOC contents is likely related to the climate warming over the past 200 years, which promotes the prosperity of vegetation and thus leads to more input of organic matter into the lakes. Moreover, a large number of seabirds live around the sampling position and the seabird guano contains high concentrations of P, which could be regarded as an important nutrient source for vegetation. Additionally, the rapid climate warming could accelerate the chemical weathering rates, and thus lead to increased CaO contents in the sediment profiles according to its geological background. Therefore, the concentrations of other elements are very likely diluted by the high contents of organic matter and CaO in the upper part of the sediment cores. It is noteworthy that the rapidly increasing trend of Pb contents are related to the gas-oil powered generators in Ny-Ålesund and long-range atmospheric transport from Europe. This study highlighted the nonnegligible influence of climate warming on the inorganic elemental geochemistry distributions in remote lakes.

Lakes and lake sediments are significant components of the global carbon (C) cycle, and may store very large amounts of organic matter. Carbon sequestration in lakes is subject to substantial temporal and spatial variation and may be strongly affected by human activities. Here, we report accumulation rates (AR) of organic C (OC), total nitrogen (TN) and total phosphorous (TP), and investigate their responses to anthropogenic impact over the past 150 years by analyzing 62 sediment cores from 11 shallow lakes in the Songnen Plain, northeast China. From the center of each of the lakes, we selected one master core for age determination by 210Pb and 137Cs radioisotopes. The contents of OC, TN, TP, dry bulk density and mass specific magnetic susceptibility were then determined for all cores. The regional OCAR, TNAR and TPAR up-scaling from the multiple cores yielded mean values of 51.63 ± 15.13, 2.50 ± 0.98, and 0.90 ± 0.21 g m-2 yr-1, respectively. Nutrient AR in the studied lakes increased by a factor of approximately 2 × from the middle 19th century to the 1950s, and approximately 5 × after the 1950s. Elemental ratios show that the increase in OCAR is mainly the result of C autogenesis from the growth of aquatic plants stimulated by agricultural intensification, including increased chemical fertilizer application and farmland expansion. Significantly enhanced nutrient burial by these lakes after the 1950s resulted from increased anthropogenic impacts in northeast China. More sustainable agricultural practises, including a decrease in P fertilizer use, would result in a lowering of OCAR, TNAR and TPAR in the future.

Mercury (Hg) transformations in sediments are key factors in the Hg exposure pathway for wildlife and humans yet are poorly characterized in Arctic lakes. As the Arctic is rapidly warming, it is important to understand how the rates of Hg methylation and demethylation (wich determine Hg bioavailability) change with temperature in lake sediments. Methylation and demethylation potentials were determined for littoral sediments (2.5 m water depth) in two deep and two shallow lakes in the Canadian Arctic using Hg stable isotope tracers at incubation temperatures of 4, 8, or 16 °C for 24 h. Compared to sediments from other regions, Hg methylation and demethylation potentials in these sediments are low. The maximum depth of the lake from which sediment was collected exerted a stronger influence over methylation potential than sediment Hg concentration or organic matter content; the shallowest lake had the highest Hg methylation potential. Sediments from the shallowest lake also demonstrated the greatest response to the temperature treatments, with significantly higher methylation potentials in the 8 and 16 °C treatments. Sediments from the deep lakes demonstrated greater demethylation potentials than shallow lakes. The methylmercury to total Hg ratio in sediments supported the measured transformation potentials as the lake with the greatest methylation potential had the highest ratio. This study supports previous works indicating that Hg methylation potential may increase as the Arctic warms, but demethylation potential does not respond to warming to the same degree, indicating that Hg methylation may predominate in warming Arctic sediments.

In eutrophic lacustrine ecosystems, drifting algal blooms are easily trapped by emergent macrophytes in downwind littoral zones, potentially altering carbon cycling processes; yet, knowledge remains limited about the mechanisms driving these changes. In this study, Microcystis and Phragmites, two dominant photosynthetic organisms in a hypereutrophic (Lake Taihu, China), were collected to simulate their co-decomposition processes. We demonstrate how molecular-level biomarkers could be used to elucidate the degradation dynamics of these two distinct organic forms in mixtures. Microcystis-derived carbon accelerated the decomposition rate of mixed systems (positive co-metabolism effect), rather than retarding it. The decomposition rate of TOC (total organic carbon) directly measured in the mixed treatments was 14% higher than when the two substrates were incubated alone. The use of specific fatty acid biomarkers facilitated more accurate tracking, demonstrating 1.09 times higher decomposition rates for Phragmites detritus in mixed treatments than in single Phragmites treatments. Furthermore, Microcystis showed 0.98 times higher decomposition rates in mixed treatments than in single treatments. The addition of Microcystis detritus to Phragmites detritus might meet microbial stoichiometric requirements, increasing the abundance of decomposing bacteria in Phragmites detritus, and accelerating decomposition rates, resulting in the co-metabolism of Microcystis and Phragmites carbon. Given the increasing occurrence of algal blooms in eutrophic lakes, the processes documented here might enhance greenhouse gas emissions from lakes with continued global climate warming.

Cores (15 to 40 cm of depth) were collected from 11 lakes of the Songnen Plain in northeastern China to reconstruct changes in potentially harmful trace element (PHTE) inputs as tracers of human activities. In each profile, most PHTE enrichment factors do not differ significantly from the pre-industrial values (EF < 1.5), except for Cd (EF = 2-5.5). This shows that detrital material accounts for a large part of the PHTE supply to the Songnen Plain lakes. Radiometric dating of the cores (210Pb, 137Cs) showed that Cd contamination started from the mid-20th century and sharply increased in the 1980s\', a pattern that matches the rapid economic and industrial growth of China. Comparison with other records in China suggests that a large part of the anthropogenic Cd in these lakes is likely local in origin. Although the Cd inputs, controlled by carbonate minerals, probably originated from a combination of sources, an intensification in agricultural practices, through the use of chemical fertilizers, manure and wastewater would explain these discrepancies between records. These findings highlight the importance of local factors on the Cd geochemical cycle in China. The large anthropogenic component of the Cd inventory compared to other PHTEs (Cu, Ni, Pb, Sb, V, Zn) and its high toxicity indicate that it should be prioritized in future environmental management.

Fildes Peninsula, with a high density of scientific stations, has been significantly impacted by anthropogenic activities. However, the contamination from penguins, a biovector that transports pollutants from ocean to land, has seldom been assessed. In this study, 32 lacustrine surface sediment samples on Fildes Peninsula and 8 lacustrine surface sediment samples on Ardley Island were collected to determine Cu, Zn, Pb, Ni, Cr, Cd, Co, Sb, Hg and P levels. The results showed that the heavy metal contents of lacustrine sediments on Ardley Island are significantly higher than those on Fildes Peninsula. The contaminants on Fildes Peninsula are mainly derived from anthropogenic activities, while the contaminants on Ardley Island are transported to the lacustrine sediments in the form of penguin guanos after a series of biomagnification in the food chain. The results indicated that the impact of penguin-transported contamination on Antarctic environment outweighs human activities near scientific stations in some areas. Therefore, more attention should be paid to the impacts of Antarctic animals on the Antarctic environment.

The purpose of this study is to implement a work that is a part of a project funded by the Italian National Antarctic Research Program (PNRA, Piano Nazionale di Ricerche in Antartide) within the main thematic focus \"Chemical Contamination-Global Change\". This research was devoted to detect and characterize micro and nano components with strong complexing capability towards metal ions at trace level in sea water, lakes and lacustrine sediments, sampled during the XXII expedition of PNRA. In particular, in the present work, the sorption complexation capacity of an Antarctic lacustrine sediments toward Cu(II) and Pb(II) is described. The characterization of the sorption was undertaken, studying kinetics and isotherm profiles. The lake here considered is Tarn Flat in the area of Terra Nova Bay. The sorption equilibria of Cu(II) and Pb(II) on the lacustrine sediments were reached in about 10 h, and they were best modelled by the Langmuir equation. Preliminary, to establish if the data here obtained were consistent with those reported for the same area in other expeditions, a common multivariate techniques, namely the principal component analysis (PCA), was applied and finally the consistency of the data has been confirmed.

A borehole drilling campaign has allowed the study of a former littoral lagoon located next to the harbour city of Cartagena in South-East Spain (close to the Sierra de Cartagena polymetallic ore deposits). This lagoon, which developed during the Holocene, was first a shallow sedimentary marine environment and later evolved into a swampy semi-endorheic basin named \"Almarjal\" (after the Arab term from the fourteenth century). The lagoon eventually dried out and at present forms part of the substratum of the modern sector of the city urban area. The basin representative sediments are sapropelic black silty facies forming a continuous sedimentary archive, accounting for more than 8000 years of depositional phenomena. The geochemical study of these sediments, together with their absolute calibrated dating by 14C, allows definition of successive stages of mining and metallurgical activities in the area. In turn, this information provides a more comprehensive perspective regarding metal pollution, particularly lead contamination during different periods of the Recent Prehistory and the Classical Age. The results indicate that the beginning of contamination by lead and other heavy metals occurred as early as 4500 years ago, when the Final Chalcolithic period was taking place in the South-East of the Iberian Peninsula. This finding provides further insights regarding the debate on the origins of lead mining and metallurgy in SE Spain.

Empirical constraints on orbital gravitational solutions for the Solar System can be derived from the Earth\'s geological record of past climates. Lithologically based paleoclimate data from the thick, coal-bearing, fluvial-lacustrine sequences of the Junggar Basin of Northwestern China (paleolatitude ∼60°) show that climate variability of the warm and glacier-free high latitudes of the latest Triassic-Early Jurassic (∼198-202 Ma) Pangea was strongly paced by obliquity-dominated (∼40 ky) orbital cyclicity, based on an age model using the 405-ky cycle of eccentricity. In contrast, coeval low-latitude continental climate was much more strongly paced by climatic precession, with virtually no hint of obliquity. Although this previously unknown obliquity dominance at high latitude is not necessarily unexpected in a high CO2 world, these data deviate substantially from published orbital solutions in period and amplitude for eccentricity cycles greater than 405 ky, consistent with chaotic diffusion of the Solar System. In contrast, there are indications that the Earth-Mars orbital resonance was in today\'s 2-to-1 ratio of eccentricity to inclination. These empirical data underscore the need for temporally comprehensive, highly reliable data, as well as new gravitational solutions fitting those data.