Browsing by Author "Beer, J"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Beryllium isotopes as tracers of Lake Lisan (Last Glacial Dead Sea) hydrology and the Laschamp geomagnetic excursion
    (Elsevier Science BV, 2014-08-15) Belmaker, R; Stein, M; Beer, J; Christl, M; Fink, D; Lazar, B
    The content of the cosmogenic isotope Be-10 (t(1/2) = 1.39 Ma) in lacustrine sediments that deposit in lakes with a large watershed is susceptible to both climate and cosmogenic production rate variations. In order to distinguish between these two controls, we measured Be-10 and major elements in several sections of the annually laminated sediments of the Lake Lisan (the last Glacial precursor of the Dead Sea) that are composed of detrital sediments and primary (evaporitic) aragonites. The sections were selected to represent regional hydrology and climate as reflected by different lake configurations (level rise, drop and high-stands) and rapid change in the Be-10 production rate during the Laschamp geomagnetic excursion. Since the short-lived cosmogenic "sister" of Be-10, Be-7 (t(1/2) = 53.3 d) has virtually no recycled component, the recycled Be-10 in Lake Lisan detrital sediments was evaluated by measuring Be-7 in their modern equivalents: modern flood suspended matter, dust and mud cracks. Our results demonstrate that although the recycled Be-10 component is significant, secular variations in the Be-10 concentration in Lake Lisan sediments correlate with hydrological variations and geomagnetic excursions. During periods of moderate variations in Be-10 production rate, the Be-10 concentration in the Lisan detrital sediments positively correlates with lake level, Al + Fe content and the (Al + Fe)/(Ca + Mg) ratio. These correlations suggest that the Be-10 is adsorbed on the fine silicate component (probably clays) of the detrital laminae. The fine silicates together with carbonates were transported to Dead Sea drainage basin mainly as airborne dust that after a short residence time was washed into Lake Lisan as flood suspended matter. We suggest that preferential dissolution of carbonates in the flood suspended matter concentrated the residual fine component leading to the positive correlation between Be-10 and the (Al + Fe)/(Ca + Mg) ratio. During periods of increased water discharge more carbonates were dissolved and hence the Be-10 concentration in the detrital laminae increased. During periods of rapid increase in the Be-10 production rate (e.g. the Laschamp excursion), Be-10 showed a similar to 2 fold increase, beyond the above-mentioned correlations (lake levels and Al + Fe contents). This observation suggests that Lake Lisan can serve as a potential high-resolution archive of Be-10 production rate variations during periods of geomagnetic excursions. © 2014, Elsevier Ltd.
  • No Thumbnail Available
    Item
    Impact of tsunami inundation on soil salinsaltion - up to one year after the 2011 Tohoku-okitsunami
    (Springer, 2013-09-27) Chagué-Goff, C; Wong, HKY; Sugawara, D; Goff, JR; Nishimura, Y; Beer, J; Szczuciński, W; Goto, K
    The long-term effect of tsunami inundation on soil salinisation was assessed following the 2011 Tohoku-oki tsunami in two areas on the Sendai Plain, near Sendai airport in the Miyagi Prefecture and Matsukawa-ura near Soma in the Fukushima Prefecture. Data gathered over four sampling seasons 2, 5, 9 and 11 months after the tsunami near Sendai airport show that the salt content generally decreased with time. Concentrations were nevertheless higher in February 2012 than in October 2011, probably due to capillary action and evaporation following long periods with little precipitation in the winter, while the lower concentrations in October were attributed to dilution due to intense rainfall prior to the sampling period. In February 2012, the area with chloride concentrations over the guidelines for the establishment of rice seedlings still extended for nearly 1 km between 2.45 and 3.33 km inland. Chloride concentrations also reached the guideline values at the land surface 1.71 km inland. This corresponded to the limit of the area deemed not suitable for rice production by local rice farmers. However, recent observations revealed that rice crops were not only halted in 2011 but also in 2012, probably due to high salinisation of soil and/or surface and groundwater. Our study shows that soil salinisation was still recorded to nearly 15 cm depth in areas with fine-grained organic-rich soil ~2.5 km from the shoreline 11 months after the tsunami, and that water-leachable ions were preferentially retained in organic-rich muddy sediment and soil, reflecting the long-term impact of tsunami inundation. In Matsukawa-ura, salt crusts still covered the area flooded by the tsunami in February 2012 and both the soil and muddy tsunami deposit were characterised by high chloride and sulphate concentrations. The latter might also lead to sulphide toxicity. Remediation measures have been implemented in certain areas, but further research needs to be carried out to test the effectiveness of the measures being used to allow rice production to resume. © 2014, Springer Science+Business Media Dordrecht.
  • Thumbnail Image
    Item
    Insights from stable isotopes for evaluating weed invasion in urban bushland
    (University of New South Wales and Australian Nuclear Science and Technology Organisation, 2015-07-08) Beer, J; Chagué-Goff, C; Andrew, AS; Barry, LA
    Why is Pittosporum undulatum taking over in Sydney’s urban bushland? Bush regeneration manuals recommend removing the native shrub Pittosporum undulatum because it creates shady conditions suppressing regeneration of other native plants. We used stable isotope analysis to compare the water use efciency and nutrient cycling processes of Pittosporum with other plant species to determine why it has a competitive edge in urban bushland. We collected plant, litter and soil samples from eight sites along Wolli Creek in southern Sydney. Four sites were dominated by exotic weeds and Pittosporum undulatum (‘weedy' sites), while the other four sites were dominated by native vegetation species (‘native' sites). Plant, litter and soil samples were analysed for %C, %N, δ13C and δ15N. Plant material and litter at ‘native’ sites had a higher carbon content and lower nitrogen content compared to ‘weedy‘ sites. Soil and Pittosporum undulatum had similar %C and %N values regardless of whether they were collected from ‘native’ or ‘weedy’ sites. Initial results indicate that native species and exotic species had distinct δ13C values in their mature leaf tissue, suggesting higher water use efficiency of native plants. Pittosporum undulatum had a similar isotopic signature to other native species. Nitrogen isotope results show plant species have unique δ15N values reecting unique N capture strategies. Soil δ15N signatures were variable. Pittosporum undulatum was expected to be similar to the exotic plants in terms of isotopic signature, assuming that this native species is utilising resources in a similar way to invasive exotic species. Our pilot study indicates this is not the case, and thus nativespecies may be becoming dominant in urban bushland through other mechanisms. Further research is required to understand how nutrients are captured and cycled in urban bushland.