Search

Studies based on metal isotope changes at micro-scale interfaces within soils (i.e., between aggregates of different size fractions) can provide further insight into soil-plant interactions during long-term phytoextraction. Here, aggregate size separation was conducted on two contaminated soils that underwent phytoextraction using Zn/Cd hyperaccumulator Sedum plumbizincicola over six consecutive seasons. The dynamic changes in Zn and Cd concentrations, chemical fractionations and isotope compositions in soil aggregates were investigated. As phytoextraction proceeded from the first (C1) to the sixth (C6) season, shoot Zn displayed a marginally heavier isotope composition despite the essentially constant Zn isotope composition of bulk soils and the 50–250, 5–50, 1–5, and

Abstract This study aims to establish whether zinc (Zn) and cadmium (Cd) share similar physiological mechanisms for uptake and translocation in cacao plants (Theobroma cacao L.). Multiple-collector ICP-MS was used to determine the Zn stable isotope compositions in the roots, stems and leaves of 19 diverse cacao genotypes grown in hydroponics with 20 µmol L−1 CdCl2. Additional plants of one genotype were grown in hydroponic solutions containing lower Cd concentrations (0 and 5 µmol L−1 added CdCl2). Regardless of the Cd concentration used in the exposures, the Zn stable isotope compositions show the same systematic patterns in plant organs, with δ66Znroot > δ66Znstem > δ66Znleaf (δ66Zn denotes relative differences in 66Zn/64Zn ratios in parts per thousand). The mean Zn stable isotope fractionation between the plants and the hydroponic solutions was ε66Znuptake = –1.15 ± 0.36‰ (2SD), indicating preferential uptake of isotopically light Zn by plants from the hydroponic solution. The mean stable isotope fractionation factor associated with translocation of Zn from roots to shoots, ε66Znseq-mob = + 0.52 ± 0.36‰ (2SD), shows that isotopically heavy Zn is preferentially sequestered in the cacao roots, whilst isotopically light Zn is mobilised to the leaves. A comparison with the Cd stable isotope compositions of the same plants shows that both isotopically light Zn and Cd are preferentially taken up by cacao plants. In contrast to Zn, however, the cacao roots retain isotopically light Cd and transfer isotopically heavy Cd to the leaves.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Cadmium is a trace metal of interest in the ocean partly because its concentration mimics that of phosphate. However, deviations from the global mean dissolved Cd/PO4 relationship are present in oxygen deficient zones, where Cd is depleted relative to phosphate. This decoupling has been suggested to result from cadmium sulphide (CdS) precipitation in reducing microenvironments within sinking organic matter. We present Cd concentrations and Cd isotope compositions in organic-rich sediments deposited at several upwelling sites along the northeast Pacific continental margin. These sediments all have enriched Cd concentrations relative to crustal material. We calculate a net accumulation rate of Cd in margin settings of between 2.6 to 12.0 × 107 mol/yr, higher than previous estimates, but at the low end of a recently published estimate for the magnitude of the marine sink due to water column CdS precipitation. Cadmium in organic-rich sediments is isotopically light (δ114/110CdNIST-3108 = +0.02 ± 0.14‰, n = 26; 2 SD) compared to deep seawater (+0.3 ± 0.1‰). However, isotope fractionation during diagenesis in continental margin settings appears to be small. Therefore, the light Cd isotope composition of organic-rich sediments is likely to reflect an isotopically light source of Cd. Non-quantitative biological uptake of light Cd by phytoplankton is one possible means of supplying light Cd to the sediment, which would imply that Cd isotopes could be used as a tracer of past ocean productivity. However, water column CdS precipitation is also predicted to preferentially sequester light Cd isotopes from the water column, which could obfuscate Cd as a tracer. We also observe notably light Cd isotope compositions associated with elevated solid phase Fe concentrations, suggesting that scavenging of Cd by Fe oxide phases may contribute to the light Cd isotope composition of sediments. These multiple possible sources of isotopically light Cd to sediments, along with evidence for complex particle cycling of Cd in the water column, bring into question the straightforward application of Cd isotopes as a paleoproductivity proxy.

Word of the ever more intensifying crisis of political parties is regarded as common sense in the public and scientific discourse. However, a glance cast at history shows that crisis narratives are not a new phenomenon, they rather accompany the parties since their founding. This is owed to the fact that parties are measured according to their ideal democratic conceptions to which they inevitably fail, due to their organizational character. Thus it is even more necessary to take a look at parties from an organizational-theoretical perspective and to question them according to their internal procedures, programs and member roles. Against this background, we sketch current inclusive and exclusive practices developed by German parties and examine which persons or groups experience particular privileges or marginalization in this respect. Beyond ideological frontiers we ask how parties can turn into „inclusive organizations“. Please find enclosed the description of each article in this Special Issue, all applying an empirical perspective on parties apart from the convential crisis diagnosis

Die Rede von einer sich verschärfenden „Krise der Parteien“ gilt in öffentlichen wie wissenschaftlichen Diskursen als Common Sense. Ein Blick in die Geschichte zeigt jedoch, dass Krisenerzählungen keineswegs eine neuartige Erscheinung sind, sondern Parteien seit deren Entstehung begleiten. Dies ist dem Umstand geschuldet, dass Parteien stets an demokratischen Idealvorstellungen gemessen werden, an denen sie aufgrund ihrer Formierung als Organisationen zwangsläufig scheitern müssen. Umso notwendiger erscheint es, Parteien aus organisationstheoretischer Perspektive in den Blick zu nehmen und sie nach ihren eigenlogischen Verfahren, Programmen und Mitgliederrollen zu befragen. Vor diesem Hintergrund skizzieren wir aktuelle Praktiken der Inklusion in und Exklusion von deutschen Parteien und welche Personen(-gruppen) hierbei eine besondere Privilegierung oder Marginalisierung erfahren. Über ideologische Trennlinien hinweg fragen wir danach, wie Parteien zu „inklusiven Organisationen“ werden können. Im Anschluss findet sich die Beschreibung der einzelnen Beiträge des Special Issue, die sich alle an der Empirie „ihre Finger schmutzig machen“ und Parteien abseits von Krisendiagnosen erforschen.