Paleoseismic data provide a long-term record of seismic activity to predict hazards for periods longer than one to a few centuries. In Sweden, the analysis reveals there was a drastic change in ...dominant seismic mode from a high to super-high deglacial mode to a low to moderately low mode in present and Late Holocene time. Paleoseismic criteria and characteristics include numerous different sources of information; viz. primary faults, bedrock deformation, sedimentary deformation, rock and sediment slides, liquefaction, sorting by shaking, tsunamis, differing geomorphic expressions, disordering and ordering of magnetic particles. By applying multiple criteria, it was possible to identify 44 paleoseismic events, including 23 events of estimated M 6–7, 12 events of M 7–8 and 6 events of M>8. Varve-dating often allows a precision as to a single year, in one case even to the season of a year. The key for paleoseismic reconstruction and testing is the application of multiple criteria.
In Protestant Cosmopolitanism and Diplomatic Culture, Daniel Riches investigates seventeenth-century Brandenburg-Swedish relations to present an image of early modern diplomacy driven by ...interpersonal networks grounded in their members' educational backgrounds, intellectual and cultural interests, religious convictions, and personal connections.
Lead (Pb) is a common contaminant in soils at e.g. mining, shooting range, and glassworks sites. In order to make reliable risk assessments and appropriate decisions on various “gentle remediation ...options”, such as applying phosphate, compost, or zero-valent iron to soils, the binding mechanism of Pb and its speciation needs to be known. Multi-surface geochemical equilibrium models are useful tools for estimating trace metal solubility and speciation, but for Pb the predictions are often poor. This study evaluates the recent parameterization for Pb in the Visual MINTEQ code for its ability to predict the solubility of Pb at different pH values in four historically contaminated Swedish soils. As an independent validation of the model performance, the modeled solid-phase speciation was compared to measured Pb speciation retrieved using extended X-ray absorption fine structure (EXAFS) spectroscopy. Furthermore, potential artefacts by the presence of Pb colloids were investigated by filtering solutions through both 0.45 μm and 10 kDa filters. The model accuracy for predicting Pb solubility was improved compared with previous studies producing log root mean square error (RMSE) values below 0.42 in three out of four soils, just by using generic assumptions. The use of ultrafiltered (<10 kDa) instead of the 0.45 μm-filtered Pb concentrations lowered the RMSE with ∼0.4 log units in two soils, giving a more accurate evaluation of the model performance. EXAFS proved to be a useful tool for validating and constraining the model, since the solid phase speciation did not exactly agree with the modeled results using default assumptions. However, a sample-specific optimization of the amount of “active” solid organic matter and Al + Fe hydroxides resulted in improved prediction of Pb solubility as well as better agreement with the EXAFS measurements. Solubility of Pb in the fourth, As-rich soil was probably controlled by Pb5(AsO4)3Cl (mimetite) with a solubility product constant of 10−83.53.
•Strongly enhanced modeling of Pb-solubility by accounting for colloidal phases.•Modeled solid-phase speciation validated by EXAFS measurements.•Sorption by organic matter or Fe/Al(hydr)oxides controlled Pb-solubility in 3 soils.•Mineral Pb5(AsO4)3Cl likely controlled Pb solubility in an As/Pb-contaminated soil.
In a record-linkage study in Stockholm, Sweden, the year 2011 prevalence of diagnosed autism spectrum disorders (ASD) was found to be 0.40, 1.74, 2.46, and 1.76 % among 0–5, 6–12, 13–17, and ...18–27 year olds, respectively. The corresponding proportion of cases with a recorded diagnosis of intellectual disability was 17.4, 22.1, 26.1 and 29.4 %. Between 2001 and 2011, ASD prevalence increased almost 3.5 fold among children aged 2–17 years. The increase was mainly accounted for by an eightfold increase of ASD without intellectual disability (from 0.14 to 1.10 %), while the prevalence of ASD with intellectual disability increased only slightly (from 0.28 to 0.34 %). The increase in ASD prevalence is likely contributed to by extrinsic factors such as increased awareness and diagnostics.
Carbon release due to permafrost thaw represents a potentially major positive climate change feedback. The magnitude of carbon loss and the proportion lost as methane (CH ₄) vs. carbon dioxide (CO ₂) ...depend on factors including temperature, mobilization of previously frozen carbon, hydrology, and changes in organic matter chemistry associated with environmental responses to thaw. While the first three of these effects are relatively well understood, the effect of organic matter chemistry remains largely unstudied. To address this gap, we examined the biogeochemistry of peat and dissolved organic matter (DOM) along a ∼40-y permafrost thaw progression from recently- to fully thawed sites in Stordalen Mire (68.35°N, 19.05°E), a thawing peat plateau in northern Sweden. Thaw-induced subsidence and the resulting inundation along this progression led to succession in vegetation types accompanied by an evolution in organic matter chemistry. Peat C/N ratios decreased whereas humification rates increased, and DOM shifted toward lower molecular weight compounds with lower aromaticity, lower organic oxygen content, and more abundant microbially produced compounds. Corresponding changes in decomposition along this gradient included increasing CH ₄ and CO ₂ production potentials, higher relative CH ₄/CO ₂ ratios, and a shift in CH ₄ production pathway from CO ₂ reduction to acetate cleavage. These results imply that subsidence and thermokarst-associated increases in organic matter lability cause shifts in biogeochemical processes toward faster decomposition with an increasing proportion of carbon released as CH ₄. This impact of permafrost thaw on organic matter chemistry could intensify the predicted climate feedbacks of increasing temperatures, permafrost carbon mobilization, and hydrologic changes.
Headwater streams can be important sources of carbon dioxide (CO₂) and methane (CH₄) to the atmosphere. However, the influence of groundwater–stream connectivity on the patterns and sources of carbon ...(C) gas evasion is still poorly understood. We explored these connections in the boreal landscape through a detailed study of a 1.4 km lake outlet stream that is hydrologically fed by multiple topographically driven groundwater input zones. We measured stream and groundwater dissolved organic C (DOC), CO₂, and CH₄ concentrations every 50 m biweekly during the ice-free period and estimated in-stream C gas production through a mass balance model and independent estimates of aquatic metabolism. The spatial pattern of C gas concentrations was consistent over time, with peaks of both CH₄ and CO₂ concentrations occurring after each groundwater input zone. Moreover, lateral C gas inputs from riparian soils were the major source of CO₂ and CH₄ to the stream. DOC mineralization and CH₄ oxidation within the stream accounted for 17–51% of stream CO₂ emissions, and this contribution was the greatest during relatively higher flows. Overall, our results illustrate how the nature and arrangement of groundwater flowpaths can organize patterns of stream C concentrations, transformations, and emissions by acting as a direct source of gases and by supplying organic substrates that fuel aquatic metabolism. Hence, refined assessments of how catchment structure influences the timing and magnitude of groundwater–stream connections are crucial for mechanistically understanding and scaling C evasion rates from headwaters.
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