Vertical zonation of testate amoebae in the Elatia Mires, northern Greece : palaeoecological evidence for a wetland response to recent climate change or autogenic processes?

The Elatia Mires of northern Greece are unique ecosystems of high conservation value. The mires are climatically marginal and may be sensitive to changing hydroclimate, while northern Greece has experienced a significant increase in aridity since the late twentieth century. To investigate the impact of recent climatic change on the hydrology of the mires, the palaeoecological record was investigated from three near-surface monoliths extracted from two sites. Testate amoebae were analysed as sensitive indicators of hydrology. Results were interpreted using transfer function models to provide quantitative reconstructions of changing water table depth and pH. AMS radiocarbon dates and 210Pb suggest the peats were deposited within the last c. 50 years, but do not allow a secure chronology to be established. Results from all three profiles show a distinct shift towards a more xerophilic community particularly noted by increases in Euglypha species. Transfer function results infer a distinct lowering of water tables in this period. A hydrological response to recent climate change is a tenable hypothesis to explain this change; however other possible explanations include selective test decay, vertical zonation of living amoebae, ombrotrophication and local hydrological change. It is suggested that a peatland response to climatic change is the most probable hypothesis, showing the sensitivity of marginal peatlands to recent climatic change

Determination of Rn-222 in freshwater: development of a robust method of analysis by alpha/beta separation liquid scintillation spectrometry.

Liquid scintillation spectrometry is used widely for determining 222Rn in natural waters; however, the benefits of α/β separation have not been fully explored. The extractants toluene and Ultima Gold F were compared, and both performed well for a range of extreme waters. A robust method for calibrating extraction and counting efficiencies has been developed. Detection limits are 20 mBq l−1 (toluene) and 16 mBq l−1 (UGF) for a 60 min count and 600-ml sample, halving the required sample volume

Development of a Novel DGT Passive Sampler for Measuring Cs-137 In Situ in Marine Environments

Cs-137 is the most released fission product in the marine environment. It is important to develop a robust in situ technique for its monitoring. The existing diffusive gradients in thin films (DGT) passive sampling techniques for in situ measurement of Cs+ have some limitations due to the ion competition and high pH of seawater. A new DGT sampler based on potassium zinc hexacyanoferrate (KZFCN) as a binding layer has been developed and investigated for the measurement of the time-weighted average concentration of Cs-137 in seawater. This binding layer proved a working pH range of 2–12 and an ionic strength of up to 0.75 M. Two types of diffusive gels were tested and agarose gel (AGE) was chosen for the KZFCN-DGT sampler. The measured Cs+ diffusion coefficient (1.71 × 10–5 cm2·s–1 at 25 °C) in the diffusive gel from seawater was within the expected range published in the literature. The measured concentrations of Cs-137 in seawater obtained by laboratory deployments of the KZFCN-DGT samplers for up to 4 weeks showed good precision (RSD = 13%) and accuracy (relative error = 8.5%) values. The performance test results demonstrated that the KZFCN-DGT sampler is suitable for long-term monitoring of Cs-137 in seawater due to its high capacity and resistance to ion competition and high pH

Sediment dynamics in an upland temperate catchment : changing sediment sources, rates and deposition.

Accelerated erosion and transport of fine sediment from upland temperate catchments can reflect increased erosivity and/or erodibility, due in turn to climatic and/or human forcing. Identification of sediment fluxes and sources over Holocene timescales can both enable understanding of the relative impacts of these forcings, and provide perspective on recent sediment fluxes. Here we present a ~ 5,500 year record of sediment fluxes and sources from Lake Bassenthwaite utilising magnetic measurements and fuzzy clustering, coupled with independent pollen and archaeological records, to identify the timing and impact of catchment disturbance. This record shows that recent sediment flux increases (i.e., within the last 150 years) are unprecedented in scale throughout the mid-late Holocene and appear to be in response to specific human changes occurring within the catchment. Earlier episodes of human activity, from the mid-Holocene onwards, show no link with increased lake sediment fluxes, indicating either limited catchment impact and/or ‘buffering’ through within-catchment sediment storage. Increasingly intensive land use and reduction of sediment storage through revetment construction on a key inflow, Newlands Beck, have resulted in 3 x increases in lake sediment flux. These data may be significant for other upland temperate areas, as increasing land use pressures and reduced sediment storage capacity may not only increase contemporary sediment flux, but increase sensitivity to predicted increases in rainfall and storminess as a result of global warming