History Matters: Pre-Exposure to Wastewater Enhances Pesticide Toxicity in Invertebrates

Disturbance regimes determine communities’ structure and functioning. Nonetheless, little effort has been undertaken to understand interactions of press and pulse disturbances. In this context, leaf-shredding macroinvertebrates can be chronically exposed to wastewater treatment plant effluents (i.e., press disturbance) before experiencing pesticide exposure following agricultural runoff (i.e., pulse disturbance). It is assumed that wastewater pre-exposure alters animals’ sensitivity to pesticides. To test this hypothesis, we exposed model-populations of the shredder <i>Gammarus fossarum</i> to wastewater at three field-relevant dilution levels (i.e., 0%, 50%, and 100%). After 2, 4, and 6 weeks, survival, leaf consumption, dry weight, and energy reserves were monitored. Additionally, animals were assessed for their sensitivity toward the neonicotinoid insecticide thiacloprid using their feeding rate as response variable. Both wastewater treatments reduced gammarids’ survival, leaf consumption, dry weight, and energy reserves. Moreover, both wastewater pre-exposure scenarios increased animals’ sensitivity toward thiacloprid by up to 2.5 times compared to the control. Our results thus demonstrate that press disturbance as posed by wastewater pre-exposure can enhance susceptibility of key players in ecosystem functioning to further (pulse) disturbances. Therefore, applying mitigation measures such as advanced treatment technologies seems sensible to support functional integrity in the multiple-stress situation

Photo-switchable spin-crossover iron(III) compound based on intermolecular interactions

Iron(III) spin-crossover compounds, [Fe(qnal)2]CF3SO3・MeOH (1・MeOH) and [Fe(qual)2]CF3SO3・acetone (1・acetone) were prepared and their spin transition properties were characterized by magnetic susceptibility measurement, Mӧssbauer spectroscopy and single crystal analysis. Two iron(III)compounds exhibited abrupt spin transition with thermal hysteresis loop(T1/2↑=115　K and T1/2↓=104 K for 1・MeOH, and T1/2↑=133 K and T1/2↓=130 K for 1・acetone). Single crystal analysis revealed both of the structures in high-spin(HS)and low-spin(LS)states for 1・acetone. The difference of bond length between the HS and LS states for 1・acetone was~0.10 Å, which was corresponding to that of typical iron(III)SCO compounds. Specially, it showed strong intermolecular interactions by π-π stacking formed between the neighbor complexes leading to 2-D sheet. Both 1・MeOH and 1・acetone exhibited LIESST effect when it was illuminated at 1000 nm. We also confirmed that the introduction of strong intermolecular interactions, such as π-π stacking, can play an important role in LIESST effect

Two-dimensional atom-phonon coupling model for spin conversion: role of metastable states

Spin conversion, (SC), compounds are composed of molecules organized around a transition metal ion. The ion spin value is smaller for the ion fundamental level than for its first excited one. So, increasing the temperature changes the spin mean value. This spin conversion can be continuous or can display a first order phase transition called spin transition. The atom phonon coupling model, introduced recently, allows to describe at least qualitatively different experimental results. Up to now, this model has been applied on a linear chain of atoms. In this paper we apply it on a square lattice. We study the thermal variations of different thermodynamic parameters and the metastable states which are present around the transition. In this study, it is expected that the critical point of some (SC) compounds can be reached by applying on them a small hydrostatic pressure; it is also expected that ultrasound pulses can induce, at a very low temperature, a conversion between the stable low spin state and the metastable high spin state and it is also predicted that the crystal sound velocity can display a discontinuity at the first order phase transition