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Liu G.,Lanzhou Jiaotong University | Liu G.,Engineering Research Center for Cold | Liu Z.,CAS Nanjing Institute of Geography and Limnology | Smoak J.M.,University of South Florida | Gu B.,University of Florida
Quaternary International | Year: 2015

Lake Chenghai, a brackish lake located in southwest China, has changed from oligotrophic to mesotrophic and finally eutrophic conditions since the 1990s. In the late 1990s, planktivorous icefish were introduced into the lake, which dramatically altered the fish population. A paleolimnological evaluation using the cladoceran remains was conducted in order to analyze the effects of increasing nutrient load and fish introduction on the cladoceran community of this lake. Our results showed that the dominant cladocerans were littoral species, with a low abundance of planktonic Bosmina in the sediment. Increasing eutrophication since the late 1990s greatly enhanced the abundance of cladoceran assemblages, especially for the species that prefer eutrophic conditions. Meanwhile, the species which prefer oligotrophic conditions were extirpated. The changes in Daphnia ephippium length suggested that the planktivorous icefish have varying effects on the body size of different species. © 2014 Elsevier Ltd and INQUA. Source

Liu G.,Lanzhou Jiaotong University | Liu G.,Engineering Research Center for Cold | Liu Z.,CAS Nanjing Institute of Geography and Limnology | Liu Z.,Jinan University | And 3 more authors.
Hydrobiologia | Year: 2014

Environmental controls on cladoceran community structure in lake ecosystems are complex and may involve many environmental parameters including trophic state and fish populations. In Lake Erhai, a plateau lake located in southwest China, it was hypothesized that a combination of lake eutrophication and planktivorous fish introduction would increase the abundance of cladoceran, while also decreasing cladoceran size. To test this hypothesis, we examined temporal changes in cladoceran microfossils in the sediments of Lake Erhai over the past century. The influence of changing macrophyte coverage within the littoral region of the lake was also considered. Results demonstrated that cladoceran abundance (measured as flux of cladoceran fossils in the sediments) increased markedly accompanying eutrophication of the lake. In addition, there was a shift in the dominant cladoceran species from those species that prefer oligotrophic conditions to those that prefer mesotrophic and eutrophic conditions. A reduction in the ephippium length of Daphnia spp. was observed and attributed to the introduction of the planktivorous fish Neosalanx taihuensis. Our findings indicated that eutrophication and fish introduction were the main controls affecting cladoceran community structure during the recent decades, and predation by planktivorous fish had an important impact on Daphnia body size. © 2014 Springer International Publishing Switzerland. Source

Ren Y.,Lanzhou Jiaotong University | Ren Y.,Engineering Research Center for Cold | Zhao B.,Lanzhou Jiaotong University | Zhao B.,Engineering Research Center for Cold | And 3 more authors.
Journal of Colloid and Interface Science | Year: 2011

Quantitative structure-property relationship (QSPR) models for the cloud points of nonionic surfactants were developed based on CODESSA descriptors. Essentials accounting for a reliable model were considered carefully. Four descriptors were selected by a generic algorithm (GA) method to link the structures of nonionic surfactants to their corresponding cloud-point values. The descriptors were also analyzed using principal component analysis (PCA). Nonlinear models based on support vector machine (SVM) and projection pursuit regression (PPR) were also developed. All models were validated in two ways, i.e., internal cross-validation (CV) and a test set. The results are discussed in light of the main factors that influence the property under investigation and its modeling. In addition, an independent external data set of 16 nonionic surfactants was used to check the generalization ability of the optimum model. © 2011 Elsevier Inc. Source

Zhou J.,Lanzhou Jiaotong University | Zhou J.,Engineering Research Center for Cold | Wang S.F.,Lanzhou Jiaotong University | Wang S.F.,Engineering Research Center for Cold
Advanced Materials Research | Year: 2013

Desorption experiments of coconut shell activated carbon (CSAC) saturated with Pb2+ had been conducted in presence of dual-frequency and single-frequency (30 kHz,500 kHz,1200 kHz) ultrasound. The desorption efficiency was better at dual-frequency ultrasound than at single-frequency ultrasound. The best of desorption efficiency of Pb2+ was 65.5% at 500×500 kHz. The desorption efficiency of Pb2+ increased by increasing temperature, but when the temperature was more than 50°C, the desorption efficiency decreased initially. The stability of CSAC was not affected with cavitation effect produced by ultrasound of frequency of 500×500 kHz. The carbon loss was less. The rate of loss was only 0.6%. In conclusion, ultrasound was used as alternative method to regenerate activated carbon adsorbing with heavy metal ion. © (2013) Trans Tech Publications, Switzerland. Source

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