•Analysis of brGDGT distributions in global peat dataset.•Correlation of brGDGT distributions with peat pH and mean annual air temperature.•Development of peat-specific temperature and pH proxies.
...Glycerol dialkyl glycerol tetraethers (GDGTs) are membrane-spanning lipids from Bacteria and Archaea that are ubiquitous in a range of natural archives and especially abundant in peat. Previous work demonstrated that the distribution of bacterial branched GDGTs (brGDGTs) in mineral soils is correlated to environmental factors such as mean annual air temperature (MAAT) and soil pH. However, the influence of these parameters on brGDGT distributions in peat is largely unknown. Here we investigate the distribution of brGDGTs in 470 samples from 96 peatlands around the world with a broad mean annual air temperature (−8 to 27°C) and pH (3–8) range and present the first peat-specific brGDGT-based temperature and pH calibrations. Our results demonstrate that the degree of cyclisation of brGDGTs in peat is positively correlated with pH, pH=2.49×CBTpeat+8.07 (n=51, R2=0.58, RMSE=0.8) and the degree of methylation of brGDGTs is positively correlated with MAAT, MAATpeat (°C)=52.18×MBT5me′−23.05 (n=96, R2=0.76, RMSE=4.7°C). These peat-specific calibrations are distinct from the available mineral soil calibrations. In light of the error in the temperature calibration (∼4.7°C), we urge caution in any application to reconstruct late Holocene climate variability, where the climatic signals are relatively small, and the duration of excursions could be brief. Instead, these proxies are well-suited to reconstruct large amplitude, longer-term shifts in climate such as deglacial transitions. Indeed, when applied to a peat deposit spanning the late glacial period (∼15.2kyr), we demonstrate that MAATpeat yields absolute temperatures and relative temperature changes that are consistent with those from other proxies. In addition, the application of MAATpeat to fossil peat (i.e. lignites) has the potential to reconstruct terrestrial climate during the Cenozoic. We conclude that there is clear potential to use brGDGTs in peats and lignites to reconstruct past terrestrial climate.
In lake sediment investigations of heavy metal pollution history, it has become a common approach to calculate enrichment factors (EFs) by normalizing elemental distributions to a reference ...lithogenic element. However, this approach requires that the reference element remains stable once it has been deposited to the sediment (it is not affected by diagenetic processes). This is rarely studied in well-controlled field experiments. Here, we test the commonly used reference elements titanium (Ti), zirconium (Zr), aluminum (Al), and rubidium (Rb). We use a unique series of freeze cores collected in different years since 1979 in Lake Nylandssjön in northern Sweden. This lake has sediment with distinct varves (annually laminated deposit). Element concentrations in individual varves were analyzed using X-ray fluorescence (XRF) spectroscopy. By tracking the newly formed surface varve from different cores across this core series, i.e., following the element concentration in a specific varve as it becomes progressively aged, it was possible to assess the potential impact of diagenetic processes on geochemical signatures. Results confirm the conservative character of the studied elements; there was neither an increasing nor a decreasing concentration trend with time during sediment ageing for any of these elements. Secondly, we addressed the question ‘which of them is the most appropriate for EFs estimates with the aim of distinguishing anthropogenic from geogenic inputs, for example in pollution studies’. To assess the reliability of the EFs we used lead (Pb) as an example, because anthropogenic Pb in the sediment could be independently calculated using stable Pb isotopes. When anthropogenic Pb concentrations calculated with Pb-EFs were compared to the anthropogenic Pb concentrations derived from stable Pb isotopes, the differences found were 20% for Ti, 10% for Zr, 11% for Al, and 27% for Rb when upper continental crust concentrations were used for the background ratio. Based on the results from Nylandssjön our suggestions are that (1) when using EFs on a single core, which is the normal case in paleolimnology, multiple reference elements should be used together and (2) the results from those should be critically evaluated.
Volcanism is one of the major natural processes emitting mercury (Hg) to the atmosphere, representing a significant component of the global Hg budget. The importance of volcanic eruptions for ...local-scale Hg deposition was investigated using analyses of Hg, inorganic elemental tracers, and organic biomarkers in a sediment sequence from Lake Chungará (4520 m a.s.l.). Environmental change and Hg deposition in the immediate vicinity of the Parinacota volcano were reconstructed over the last 2700 years, encompassing the pre-anthropogenic and anthropogenic periods. Twenty eruptions delivering large amounts of Hg (1 to 457 μg Hg m−2 yr−1 deposited at the timescale of the event) were locally recorded. Peaks of Hg concentration recorded after most of the eruptions were attributed to a decrease in sedimentation rate together with the rapid re-oxidation of gaseous elemental Hg and deposition with fine particles and incorporation into lake primary producers. Over the study period, the contribution of volcanic emissions has been estimated as 32% of the total Hg input to the lake. Sharp depletions in primary production occurred at each eruption, likely resulting from massive volcaniclastic inputs and changes in the lake-water physico-chemistry. Excluding the volcanic deposition periods, Hg accumulation rates rose from natural background values (1.9 ± 0.5 μg m−2 yr−1) by a factor of 2.3 during the pre-colonial mining period (1400–900 yr cal. BP), and by a factor of 6 and 7.6, respectively, during the Hispanic colonial epoch (400–150 yr cal. BP) and the industrial era (~140 yr cal. BP to present). Altogether, the dataset indicates that lake primary production has been the main, but not limiting, carrier for Hg to the sediment. Volcanic activity and climate change are only secondary drivers of local Hg deposition relative to the magnitude of regional and global anthropogenic emissions.
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•We studied mercury deposition in Lake Chungará (18°S) over the last ~2700 years.•Parinacota volcano produced 20 tephra layers recorded in lake sediments.•Lake primary production was the main, not limiting, carrier of Hg to the sediment.•Volcanoes contributed to ~30% of Hg inputs to the lake over the study period.•Last 400 years anthropogenic Hg emissions overwhelmed the volcanic activities.
A critical gap in the understanding of the global cycling of mercury is the limited data describing the natural background atmospheric deposition rate of mercury before the advent of pollution. ...Existing estimates of the natural deposition rate are typically about 2−5 μg of Hg m-2 year-1 (see, for example, Swain et al. Science 1992, 257, 784−787), based on studies that generally rely on short, 210Pb-dated lake sediment and peat cores that span the past 150 years. Analyses of mercury in long peat cores in southcentral Sweden indicate that natural mercury deposition rates in the period 4000−500 BP were lower, about 0.5−1 μg of Hg m-2 year-1. This suggests that recent mercury accumulation rates in the peat (15−25 μg of Hg m-2 year-1) and measured atmospheric deposition rates of mercury in Sweden over the past 3 decades (5−30 μg of Hg m-2 year-1) (Munthe et al. Water, Air, Soil Pollut.: Focus 2001, 1, 299−310) are at least an order of magnitude greater than the prepollution deposition rate, rather than representing only a 3−5-fold increase, as has generally been estimated.
We have applied a single-bog multi-core approach to reconstruct historical Pb and Hg accumulation in an ombrotrophic bog from NW Spain, Chao de Lamoso (Xistral Mountains). Mercury was determined ...using a LECO-ALTEC AMA-254 analyzer, Pb with an EMMA-XRF analyzer and stable lead isotopes (four cores) by Quadrupole ICP-MS. Maximum concentrations were 74–122μgg−1 for Pb and 142–300ngg−1 for Hg. Higher variability was found for Hg than for Pb (2–3 times and 1.5 times, respectively). The slopes of the relationship between Hg and Pb cumulative inventories also suggested differences in relative accumulation of both elements. This substantial spatial variability indicates that, compared with Pb, a more extended sampling may be needed for an accurate estimation of Hg accumulation in mires.
The isotopic records showed higher and almost constant 206Pb/207Pb ratios (average 1.174±0.004) in the lower sections and a continuous decrease to the surface (minimum 1.141). By using the change in the isotopic composition of Pb we estimated a chronology for the last ∼200years which enabled and approximation of the temporal trends in metal pollution. Based on the average isotopic composition of the studied cores and the application of a simple binary mixing model, six periods with increasing proportions of pollution Pb were identified: prior to ∼1875 AD, with an average proportion lower than 16%; ∼1875–1910 AD, increasing up to 24%; ∼1910–1950 AD, up to 35%; ∼1950–1970, up to 54%; ∼1970–1980 AD, up to 74%; and after ∼1980 AD, increasing up to 80%. The period with the highest rate of increase in recent (since ∼1900 AD) pollution Pb (equivalent to 2% year−1) seems to have started at the maximum in Pb accumulation around the early 1970s. The Hg records showed a more simple evolution with four main phases: prior to ∼1875 AD with enrichments around 1.5-fold the background, ∼1875–1955 AD with increasing enrichments; from ∼1955 AD to ∼1980 AD with maximum values (up to 4.2-fold); and from ∼1980 AD to present, with a steady decline to 2.4-fold.
For the most recent period (after ∼1980 AD), the combination of decreasing Pb and Hg concentrations and accumulation rates/enrichments, and low 206Pb/207Pb ratios, may point to a higher relative importance of local sources (i.e. coal burning in a nearby power plant) in atmospheric metal pollution in the area.
Lakes are a key feature of arctic landscapes and can be an important component of regional organic carbon (OC) budgets, but C burial rates are not well estimated. ²¹⁰Pb-dated sediment cores and ...carbon and organic matter (as loss-on-ignition) content were used to estimate OC burial for 16 lakes in SW Greenland. Burial rates were corrected for sediment focusing using the ²¹⁰Pb flux method. The study lakes span a range of water chemistries (conductivity range 25–3400 lS cm⁻¹), areas (< 4–100 ha) and maximum depths (~ 10–50 m). The regional average focusing-corrected OC accumulation rate was ~ 2 g C m⁻² y⁻¹ prior to 1950 and 3.6 g C m⁻² y⁻¹ after 1950. Among-lake variability in post-1950 OC AR was correlated with in-lake dissolved organic carbon concentration, conductivity, altitude and location along the fjord. Twelve lakes showed an increase in mean OC AR over the analyzed time period, ~ 1880–2000; as the study area was cooling until recently, this increase is probably attributable to other global change processes, for example, altered inputs of N or P. There are ~ 20,000 lakes in the study area ranging from ~ 1 ha to more than 130 km², although over 83% of lakes are less than 10 ha. Extrapolating the mean post-1950 OC AR (3.6 g C m⁻² y⁻¹) to all lakes larger than 1000 ha and applying a lower rate of ~ 2gCm⁻² y⁻¹ to large lakes (> 1000 ha) suggests a regional annual lake OC burial rate of ~ 10.14 × 10⁹ g C y⁻¹ post 1950. Given the low C content of soils in this area, lakes represent a substantial regional C store.
Mining in Falun, Sweden, was first mentioned in a deed from ad 1288, but previous studies of peat and lake sediments inferred that mining began during the fifth to eighth centuries. In order to ...reassess these findings, we performed new geochemical analyses on new samples from three key sites: Tisksjöbergets myr, a buried mire alongside the mine; Tisken, a small lake in Falun; and Runn, the main recipient for waters draining through Falun. At Tisksjöbergets myr, the peat contains up to 6% copper, giving it the characteristics of a cupriferous bog. Hence, this record is not useful for tracing early mining. The sediments of Tisken—upon which many of the old interpretations have relied—contain numerous cut wood fragments, and two of those gave young and reversed radiocarbon dates (19th and 16th centuries for 192 and 187 cm, respectively). This indicates that the sediment was derived from infilling and, thus, has little value as a historical record. Runn's sediment—the only reliable record—provides clear evidence of a rapid onset of large‐scale mining from c. ad 1245, with abrupt increases in ore‐related elements—for example, a 34‐fold increase in copper—this increase is consistent with the mid‐13th century burial of the mire at Tisksjöberget.
Healthy diet, exercise, and sleep practices may mitigate stress and prevent illness. However, lifestyle behaviors of acute care nurses working during stressful COVID-19 surges are unclear.
To ...quantify sleep, diet, and exercise practices of 12-hour acute care nurses working day or night shift during COVID-19-related surges.
Nurses across 10 hospitals in the United States wore wrist actigraphs and pedometers to quantify sleep and steps and completed electronic diaries documenting diet over 7-days.
Participant average sleep quantity did not meet national recommendations; night shift nurses (n = 23) slept significantly less before on-duty days when compared to day shift nurses (n = 34). Proportionally more night shift nurses did not meet daily step recommendations. Diet quality was low on average among participants.
Nurses, especially those on night shift, may require resources to support healthy sleep hygiene, physical activity practices, and diet quality to mitigate stressful work environments.
•Nurses suffered high stress during COVID-19 hospital surges.•Night shift nurses slept less than day shift before workdays.•Nurses did not walk recommended steps per day when off-duty.•Diet quality and sleep quantity for all nurses were suboptimal.•Nurses who walked more steps per day reported less stress on average.
The high‐resolution mercury record of a Posidonia oceanica mat in the northwest Mediterranean provides an unprecedented testimony of changes in environmental mercury (Hg) loading to the coastal ...marine environment over the past 4315 yr BP. The period reconstructed made it possible to establish tentative preanthropogenic background Hg levels for the area (6.8 ± 1.5 ng g–1 in bulk sediments). A small, but significant, anthropogenic Hg increase was identifiable by ~2500 yr BP, in agreement with the beginning of intense mining in Spain. Changes in the record suggest four major periods of anthropogenic Hg pollution inputs to the Mediterranean: first, during the Roman Empire (2100–1800 yr BP); second, in the Late Middle Ages (970–650 yr BP); third, in the modern historical era (530–380 yr BP); and fourth, in the industrial period (last 250 years), with Hg concentrations two‐, four‐, five‐, and tenfold higher than background concentrations, respectively. Hg from anthropogenic sources has dominated during the last millennium (increase from ~12 to ~100 ng g–1), which can be related to the widespread historical exploitation of ore resources on the Iberian Peninsula. The chronology of Hg concentrations in the mat archive, together with other Hg pollution records from the Iberian Peninsula, suggests regional‐scale Hg transport and deposition and shows earlier marine Hg pollution than elsewhere in Europe. Moreover, the mat also records a higher number of historic contamination phases, in comparison with other natural archives, probably due to the fact that the bioaccumulating capacity of P. oceanica magnify environmental changes in Hg concentrations. In this study, we demonstrate the uniqueness of P. oceanica meadows as a long‐term archive recording trends in Hg abundance in the marine coastal environment, as well as its potential role in the Mediterranean as a long‐term Hg sink.
Key PointsUniqueness of P oceanica as archives of Hg abundance and Hg sink in marine areasEarly Hg pollution in the Iberian Peninsula than anywhere else in EuropeThe bioaccumulation capacity of P oceanica magnifiy changes in Hg concentrations
As a consequence of deposition of atmospheric pollution, the lead concentration in the mor layer (the organic horizon) of remote boreal forest soils in Sweden is raised far above natural levels. How ...the mor will respond to decreased atmospheric pollution is not well known and is dependent on future deposition rates, downward migration losses and upward fluxes in the soil profile. Plants may contribute to the upward flux of lead by ‘pumping’ lead back to the mor surface through root uptake and subsequent litter fall. We use lead concentration and stable isotope (
206Pb,
207Pb and
208Pb) measurements of forest vegetation to quantify plant uptake rates from the soil and direct from the atmosphere at two sites in northern Sweden; an undisturbed mature forest and a disturbed site with Scots pine (
Pinus sylvestris) growing on a recently exposed mineral soil (C-horizon) containing a minimum of atmospherically derived pollution lead. Analyses of forest mosses from a herbarium collection (spanning the last ∼100 yr) and soil matrix samples suggest that the atmospheric lead deposited on plants and soil has an average
206Pb/
207Pb ratio of 1.15, while lead derived from local soil minerals has an average ratio of ∼1.47. Since the biomass of trees and field layer shrubs has an average
206Pb/
207Pb ratio of ∼1.25, this indicates that 70% ± 10% of the inventory of 1 ± 0.8 mg Pb m
−2 stored in plants in the mature forest originates from pollution. Needles, bark and apical stemwood of the pine growing on the disturbed soil, show lower
206Pb/
207Pb ratios (as low as 1.21) than the roots and basal stemwood (having ratios > 1.36), which indicate that plants are able to incorporate lead directly from the atmosphere (∼50% of the total tree uptake). By partitioning the total uptake of lead into uptake from the atmosphere and different soil layers using an isotopic mixing model, we estimate that ∼0.03 ± 0.01, 0.02 ± 0.01 and 0.05 ± 0.01 mg Pb m
−2 yr
−1 (mean ± SD), is taken up from the mor layer, the mineral soil and the atmosphere, respectively, by plants in the undisturbed mature forest. These small fluxes, which are at least a magnitude lower than reported downward migration losses, suggest that plant uptake will not strongly prolong the self-cleaning rate of the mor layer.
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