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The assumed dominance of chloride (Cl - ) in terrestrial ecosystems is challenged by observations of extensive formation of organically bound Cl (Cl org ), resulting in large soil Cl storage and internal cycling. Yet, little is known about the spatial distribution of Cl in ecosystems. We quantified patterns of Cl distribution in different habitats along a boreal hillslope moisture gradient ranging from relatively dry upland coniferous forests to wet discharge areas dominated by alder. We confirmed that dry habitats are important for Cl storage but found that Cl pools tended to be larger in moist and wet habitats. The storage of Cl org was less important in wet habitats, suggesting a shift in the balance between soil chlorination and dechlorination rates. Cl concentrations in the herb layer vegetation were high in wet and moist sites attributed to a shift in plant species composition, indicating plant community-dependent ecosystem Cl cycling. Mass-balance calculations showed that internal Cl cycling increased overall ecosystem Cl residence times at all sites and that plant uptake rates of Cl - were particularly high at wet sites. Our results indicate that habitat characteristics including plant communities and hydrology are key for understanding Cl cycling in the environment.

Climate change is predicted to have far reaching consequences for the mobility of carbon in arctic landscapes. On a regional scale, carbon cycling is highly dependent on interactions between terrestrial and aquatic parts of a catchment. Despite this, studies that integrate the terrestrial and aquatic systems and study entire catchments using site-specific data are rare. In this work, we use data partly published by Lindborg et al. (2016a) to calculate a whole-catchment carbon mass-balance budget for a periglacial catchment in West Greenland. Our budget shows that terrestrial net primary production is the main input of carbon (99% of input), and that most carbon leaves the system through soil respiration (90% of total export/storage). The largest carbon pools are active layer soils (53% of total carbon stock or 13 kg C m -2 ), permafrost soils (30% of total carbon stock or 7.6 kg C m -2 ) and lake sediments (13% of total carbon stock or 10 kg C m -2 ). Hydrological transport of carbon from the terrestrial to aquatic system is lower than in wetter climates, but the annual input of 4100 kg C yr -1 (or 3.5 g C m -2 yr -1 ) that enters the lake via runoff is still three times larger than the eolian input of terrestrial carbon. Due to the dry conditions, the hydrological export of carbon from the catchment is limited (5% of aquatic export/storage or 0.1% of total export/storage). Instead, CO 2 evasion from the lake surface and sediment burial accounts for 57% and 38% of aquatic export/storage, respectively (or 0.8% and 0.5% of total export/storage), and Two-Boat Lake acts as a net source of carbon to the atmosphere. The limited export of carbon to downstream water bodies make our study system different from wetter arctic environments, where hydrological transport is an important export pathway for carbon., (Copyright © 2019 The Author(s). Published by Elsevier B.V. All rights reserved.)

Detection of endangered species is invaluable for conservation efforts, yet many traditional sampling techniques are ineffective at low population abundances or during certain periods of the year. Here, we compared results from a newly developed eDNA approach and the traditional observational method for the endangered pool frog (Pelophylax lessonae). Analysis using an occupancy-modeling framework indicated that the probability of pools being occupied using eDNA (0.93) was higher than for the traditional method of counting calling males and silent observed individuals (0.72). Detailed analysis revealed complementarity among the methods. That is, the traditional method gave a high rate of observation in June, whereas eDNA gave at least as many or more observations during other parts of the year. Discrepancies among the methods depended on the dominant lifecycle stage, and eDNA concentrations were higher when juveniles were present than at times when spawning occurred. eDNA concentrations were also positively related to P. lessonae observations. Our study demonstrates that an eDNA protocol for monitoring of endangered amphibian species can be particularly valuable during periods when individuals are hard to detect by observational methods, and provides guidance to sampling efforts for research and monitoring programs in other regions and systems.

Nanoparticles (NPs) have been shown to enhance X-ray radiotherapy and proton therapy of cancer. The effectiveness of radiation damage is enhanced in the presence of high atomic number (high-Z) NPs due to increased production of low energy, higher linear energy transfer (LET) secondary electrons when NPs are selectively internalized by tumour cells. This work quantifies the local dose enhancement produced by the high-Z ceramic oxide NPs Ta 2 O 5 and CeO 2 , in the target tumour, for the first time in proton therapy, by means of Geant4 simulations. The dose enhancement produced by the ceramic oxides is compared against gold NPs. The energy deposition on a nanoscale around a single nanoparticle of 100nm diameter is investigated using the Geant4-DNA extension to model particle interactions in the water medium. Enhancement of energy deposition in nano-sized shells of water, local to the NP boundary, ranging between 14% and 27% was observed for proton energies of 5MeV and 50MeV, depending on the NP material. Enhancement of electron production and energy deposition can be correlated to the direct DNA damage mechanism if the NP is in close proximity to the nucleus., (Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.)

Understanding the fundamental mechanisms involved in the induction of biological damage by ionizing radiation remains a major challenge of today's radiobiology research. The Monte Carlo simulation of physical, physicochemical and chemical processes involved may provide a powerful tool for the simulation of early damage induction. The Geant4-DNA extension of the general purpose Monte Carlo Geant4 simulation toolkit aims to provide the scientific community with an open source access platform for the mechanistic simulation of such early damage. This paper presents the most recent review of the Geant4-DNA extension, as available to Geant4 users since June 2015 (release 10.2 Beta). In particular, the review includes the description of new physical models for the description of electron elastic and inelastic interactions in liquid water, as well as new examples dedicated to the simulation of physicochemical and chemical stages of water radiolysis. Several implementations of geometrical models of biological targets are presented as well, and the list of Geant4-DNA examples is described., (Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.)

Purpose: To study the influence of DNA configuration on the direct damage yield. No indirect effect has been accounted for., Methods: The GEANT4-DNA code was used to simulate the interactions of protons and alpha particles with geometrical models of the A-, B-, and Z-DNA configurations. The direct total, single, and double strand break yields and site-hit probabilities were determined. Certain features of the energy deposition process were also studied., Results: A slight increase of the site-hit probability as a function of the incident particle linear energy transfer was found for each DNA configuration. Each DNA form presents a well-defined site-hit probability, independently of the particle linear energy transfer. Approximately 70% of the inelastic collisions and ~60% of the absorbed dose are due to secondary electrons. These fractions are slightly higher for protons than for alpha particles at the same incident energy., Conclusions: The total direct strand break yield for a given DNA form depends weakly on DNA conformation topology. This yield is practically determined by the target volume of the DNA configuration. However, the double strand break yield increases with the packing ratio of the DNA double helix; thus, it depends on the DNA conformation.