Abstract. Trivalent iron is known to occur in amethysts in three different environments: substitutional with an as yet unidentified alkali ion in an adjacent interstitial site on the twofold axis (so-called $1 center), substitutional with a proton on one of the four oxygen neighbors ($2 center) and without detectable charge compensation (so-called I center because it was proposed to be in interstitial sites, but its nature is still disputed). The alkali ion in the Sz center was now identified as Li and the Li and Fe superhyperfine (shf) tensors were determined by electron paramagnetic resonance at low temperatures in samples of unusually high quality. The fine structure and ~H shf structure tensors for the $2 center with the proton on an oxygen with longer bond distance were evaluated and the geometry of the oxygen coordination was estimated by application of the superposition model. For the I center the 57Fe and zgsi shf splittings were determined and the evidence in favor of assignment to an interstitial site is reviewed.

Purpose Boric acid was applied in an earthworm field test according to ISO 11268-3 as a possible alternative for the currently used reference substances that may no longer be available in the near future. Material and methods The test site was a pasture with a silt-and clay-dominated soil, a pH of 5.7 and an organic content of 2.8%. In addition to a water-only control, two separate treatments of boric acid were applied: single applications at rates of 187 and 750 kg/ha. In order to investigate the acute impact of this compound, biological sampling was undertaken 4 weeks after application by hand sorting combined with formaldehyde extraction. Results and discussion The earthworm community consisted of seven species commonly found at German grassland sites. In the control plots, mean abundance was very high: 984 individuals per square metre before application and 390 individuals per square metre 4 weeks following application of boric acid. In the treated plots, abundance and biomass were reduced by more than 50% compared to the control plots, respectively. In general, juvenile earthworms as well as the epigeic species were affected most strongly.Conclusions On the basis of this study, boric acid has the potential to be an alternative reference substance in assessing the acute impact on earthworm species in field tests.

Thiamethoxam is a widely used neonicotinoid insecticide that has been detected in surface water monitoring programs in North America and Europe. This has led to questions about its toxicity to nontarget insects, specifically those with an aquatic life stage. To address the uncertainty associated with possible impacts from environmental exposures, a chronic (35-d) outdoor mesocosm study with a formulated product containing thiamethoxam was conducted. The specific focus of the study was the response of mayflies (Ephemeroptera), which have been reported to be particularly sensitive in laboratory studies. A range of concentrations (nominally 0.1, 0.3, 1.0, 3.0, and 10.0 mg/L thiamethoxam), plus untreated controls were tested, and the abundance and emergence of mayflies (Cloeon dipterum) were assessed weekly for 35 d. Mean measured time-weighted average exposures were within 6% of nominal over the duration of the study, with the mean half-life of thiamethoxam in each treatment ranging from 7 to 13 d. Statistically significant reductions in both larval abundance and adult emergence were observed at 10.0, 3.0, and 1.0 mg/L following 1, 2, and 3 wk of exposure, respectively. Exposure to 0.1 and 0.3 mg/L thiamethoxam had no statistically significant effect on larval mayfly abundance or adult emergence at any point in the study. These findings support a 35-d no-observed-effect concentration (NOEC) of 0.3 mg thiamethoxam/L for mayflies (C. dipterum) under chronic conditions. Furthermore, because the 95th percentile of environmental concentrations has been reported to be 0.054 mg/L, these results indicate that populations of C. dipterum and similarly sensitive aquatic insects are unlikely to be significantly impacted by thiamethoxam exposure in natural systems represented by the conditions in our study.

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Trivalent ions of Fe, Cr and Mo are easily incorporated into CsCl‐type lattices. Evidently their geometries partly derive from those for divalent ions by exchange of a neutral molecule by hydroxyl or halide. In the ammonium halides hydrogen bonding manifests itself in predominance of low site symmetries and dynamic effects. Evidence for interstitial incorporation of di‐ and trivalent ions in quartz and isomorphous ABO4 compounds is also presented. EPR data for Fe3+ indicate simultaneous incorporation of O2− or OH− in the c‐axis channels. A kinetic reason for preferred interstitial incorporation is proposed. Enhanced mobilities of these as well as certain main constituents may also enhance the reactivities.