The distribution and ecosystem risk of 16 polycyclic aromatic hydrocarbons (PAHs) in the Luan River, China, has been investigated. summation operatorPAHs levels ranged from 37.3 to 234 ng L(-1) in water, from 20.9 to 287 ng g(-1) in sediment and from 36.9 to 378 ng g(-1) in bank soil, respectively. A method based on toxic equivalency factors (TEFs) and risk quotient (RQ) which can be used to assess the ecosystem risk of summation operatorPAHs sensitively and accurately was invented and a new ecosystem risk classification of summation operatorPAHs was suggested. The results indicated that the PAHs in aquatic environment of the Luan River resulted in low ecosystem risk and at S9 the ecosystem risk of PAHs in water was moderate. Low and moderate molecular PAHs presented much more ecosystem risk than high molecular PAHs in the Luan River basin and the mean ecosystem risk in water was higher than that in sediment and bank soil.

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We provide constructions of multilinear groups equipped with natural hard problems from indistinguishability obfuscation, homomorphic encryption, and NIZKs. This complements known results on the constructions of indistinguishability obfuscators from multilinear maps in the reverse direction. We provide two distinct, but closely related constructions and show that multilinear analogues of the DDH assumption hold for them. Our first construction is symmetric and comes with a κ-linear map e : G κ −→ G T for prime-order groups G and G T. To establish the hardness of the κ-linear DDH problem, we rely on the existence of a base group for which the κ-strong DDH assumption holds. Our second construction is for the asymmetric setting, where e : G 1 ו • •×G κ −→ G T for a collection of κ + 1 prime-order groups G i and G T , and relies only on the 1-strong DDH assumption in its base group. In both constructions, the linearity κ can be set to any arbitrary but a priori fixed polynomial value in the security parameter. We rely on a number of powerful tools in our constructions: probabilistic indistinguishability obfuscation, dual-mode NIZK proof systems (with perfect soundness, witness-indistinguishability, and zero knowledge), and additively homomorphic encryption for the group Z + N. At a high level, we enable "bootstrapping" multilinear assumptions from their simpler counterparts in standard cryptographic groups and show the equivalence of PIO and multilinear maps under the existence of the aforementioned primitives. * This paper has been handled by Ivan Bjerre Damgård as acting editor in chief and communicated by Alon Rosen.

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