Diclofenac (DCF) is a widely used nonsteroidal anti-inflammatory drug that is regularly detected in surface waters. To support a robust aquatic risk assessment, two early life stage (ELS) tests, compliant with the Organisation for Economic Co-operation and Development (OECD) test guideline 210, were conducted in rainbow trout and in zebrafish. Population relevant endpoints, such as hatching, growth, and survival, and in the trout study, histopathological effects in potential target organs, were examined. The bioconcentration of DCF in rainbow trout was measured in a separate study according to OECD test guideline 305. The bioconcentration factor (BCF) in rainbow trout remained below 10, demonstrating no relevant bioconcentration of DCF in fish. In the rainbow trout ELS test, the no observed effect concentration (NOEC) including histopathology was 320 µg/L. The effect of DCF on zebrafish growth was less clear, and the NOEC can be interpreted as 10 µg/L. However, for a number of reasons, the authors consider the moderately reduced growth of zebrafish exposed to concentrations of up to 320 µg/L not a repeatable, treatment-related effect of DCF. This leads us to a conclusion that DCF has, with high probability, no adverse effect on both fish species up to 320 µg/L. This NOEC indicates a sufficient safety margin for fish populations, because concentrations of DCF in European rivers are in the range of ng/L to low µg/L. Environ. Toxicol. Chem. 2013;32:442–452. © 2013 SETAC

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We show by scanning tunneling microscopy (STM) imaging that native oxide growth in moist air on hydrogen terminated Si(111) 1×1 surfaces begins by continuing formation of small oxide nuclei, 10–20 Å in diameter, in the topmost Si layer. Their statistical distribution on the flat terraces points to a homogeneous nucleation process. Oxidation is extremely slow; after about 800 h only one complete monolayer is oxidized. In addition, a small number of three-dimensional oxide nuclei, several layers deep and 50–100 Å in width, are formed at step edges as a minority species, which may be related to surface defects or contaminations.

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Adsorption and desorption of oxygen on a Pd(110) surface have been investigated by low energy electron diffraction (LEED), nuclear reaction analysis (NRA), and Rutherford backscattering (RBS). Exposure of Pd(110) to O2 at 100 K and subsequent heating, produces the following surface phases in sequence: pseudo-(2×1), c(2×6), and c(2×4). Exposure at 280 K produces only the c(2×4) phase. Above 400 K the (2×3)-1D and c(2×4) form in sequence upon O2 exposure. The phase transition (2×3)-1D to c(2×4) is accompanied by the continuous movement of the third order beams in (2×3)-1D to the half order positions. The transition between the c(2×4) and (2×3)-1D is reversible above 400 K, and depends only on the oxygen coverage. NRA indicates that the saturation coverage of oxygen with exposure to O2 at 100 K is close to 1 ML (1 ML=9.4×1014 O atoms cm−2 ). The c(2×4) and (2×3)-1D phases have surface coverages of 0.50±0.05 and 0.23±0.05 ML, respectively. The RBS results show that the surface exposed at low temperature, the (2×3)-1D and the c(2×4) phases all involve reconstruction of the Pd surface. In the low temperature exposed surface, more than a monolayer of Pd atoms are displaced laterally from their bulk-like locations in the surface region, indicating that there are displacements in at least the second layer. In the c(2×4) phase more than 0.6 ML of Pd atoms are laterally displaced. Models for the two phases are tentatively proposed.