In this work, the nonlinear optical (NLO) response of suspensions of Au nanoclusters encapsulated into hybrid block copolymer micelles was investigated by using the Z‐scan technique, employing 35 ps, 532 nm laser pulses. The block copolymer used for the encapsulation of the Au nanoclusters was poly (isoprene‐b‐acrylic acid) (PI‐PAA). The real and imaginary parts of the third‐order nonlinear susceptibility χ(3) of the dispersions were determined and were both found to be of the order of 10–13 esu for Au concentration ranged between 1 to 20 mM and of positive sign. All dispersions were exhibiting strong optical limiting action. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

To assess potential impacts on receiving systems, associated with storm water contaminants, laboratory 10-d amphipod (Eohaustorius estuarius) survival toxicity tests were performed using intact sediment cores collected from Paleta Creek (San Diego Bay, CA, USA) on 5 occasions between 2015 and 2017. The approach included deposition-associated sediment particles collected from sediment traps placed at each of 4 locations during the 2015 to 2016 wet seasons. The bioassays demonstrated wet season toxicity, especially closest to the creek mouth, and greater mortality associated with particles deposited in the wet season compared with dry season samples. Grain size analysis of sediment trap material indicated coarser sediment at the mouth of the creek and finer sediment in the outer depositional areas. Contaminant concentrations of metals (Cd, Cu, Hg, Ni, Pb, and Zn) and organic compounds (polycyclic aromatic hydrocarbons [PAHs], polychlorinated biphenyls [PCBs], and pesticides) were quantified to assess possible causes of toxicity. Contaminant concentrations were determined in the top 5 cm of sediment and porewater (using passive samplers). Whereas metals, PAHs, and PCBs were rarely detected at sufficient concentrations to elicit a response, pyrethroid pesticides were highly correlated with amphipod toxicity. Summing individual pyrethroid constituents using a toxic unit approach suggested that toxicity to E. estuarius could be associated with pyrethroids. This unique test design allowed delineation of spatial and temporal differences in toxicity, suggesting that storm water discharge from Paleta Creek may be the source of seasonal toxicity.

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