Water quality management and load reduction are subject to inherent uncertainties in watershed systems and competing decision objectives. Therefore, optimal decision-making modeling in watershed load reduction is suffering due to the following challenges: (a) it is difficult to obtain absolutely ``optimal'' solutions, and (b) decision schemes may be vulnerable to failure. The probability that solutions are feasible under uncertainties is defined as reliability. A reliability-oriented multi-objective (ROMO) decision-making approach was proposed in this study for optimal decision making with stochastic parameters and multiple decision reliability objectives. Lake Dianchi, one of the three most eutrophic lakes in China, was examined as a case study for optimal watershed nutrient load reduction to restore lake water quality. This study aimed to maximize reliability levels from considerations of cost and load reductions. The Pareto solutions of the ROMO optimization model were generated with the multiobjective evolutionary algorithm, demonstrating schemes representing different biases towards reliability. The Pareto fronts of six maximum allowable emission (MAE) scenarios were obtained, which indicated that decisions may be unreliable under unpractical load reduction requirements. A decision scheme identification process was conducted using the back propagation neural network (BPNN) method to provide a shortcut for identifying schemes at specific reliability levels for decision makers. The model results indicated that the ROMO approach can offer decision makers great insights into reliability tradeoffs and can thus help them to avoid ineffective decisions. (C) 2015 Elsevier B.V. All rights reserved.
Fe3O4@SiO2 magnetic nanoparticles modified by grafting poly(1-vinylimidazole) oligomer (FSPV) was fabricated as a novel adsorbent to remove Hg(II) from water. Fourier transform infra-red spectroscopy confirmed the successful grafting of oligomer, and thermogravimetric analysis showed FSPV had a high grafting yield with organic content of 22.8%. Transmission electron microscopy image displayed that FSPV particles were polymer-coated spheres with size of 10–20 nm. With saturation magnetization of 44.7 emu/g, FSPV particles could be easily separated from water with a simple magnetic process in 5 min. The Hg(II) adsorption capacity of FSPV was found to be 346 mg/g at pH 7 and 25 °C in 10 mM NaCl. Moreover, the removal of Hg(II) by FSPV was not obviously affected by solution pH (from 4 to 10) or humic acid (up to 8 mg/L as TOC). The presence of seven common ions including Na+, K+, Ca2+, Mg2+, Cl−, NO3−, and SO42− (up to 100 mM ionic strength) slightly increased the adsorption of Hg(II) by FSPV. X-ray photoelectron spectroscopy analysis revealed that the N atom of the imidazole ring was responsible for the bonding with Hg(II), whereas the bonding of Hg with N did not result in cleavage of Hg–Cl bond in HgCl2 and HgClOH. The regeneration of Hg(II)-loaded FSPV could be achieved with 0.5 M HCl rapidly in 10 min, and the removal of Hg(II) maintained above 94% in five consecutive adsorption–desorption cycles. Therefore, FSPV could serve as a promising adsorbent for Hg(II) removal from water.
Ye et al. have determined a maximum nitrous acid (HONO) yield of 3% for the reaction HO2 center dot H2O + NO2, which is much lower than the yield used in our work. This finding, however, does not affect our main result that HONO in the investigated Po Valley region is mainly from a gas-phase source that consumes nitrogen oxides.
[6,6]-Phenyl-C61-butyric acid-4'-hydroxyl-azobenzene ester (PCBAb) was synthesized and used as the acceptor in the fabrication of reversible UV-VIS response bi-state polymer solar cells (PSCs) based on the photoinduced cis-trans isomerization of PCBAb. The device can be switched between ``active'' and ``sleep'' by the irradiation of UV and visible light, respectively. The active device has a PCE of 2.0%. With UV irradiation, the device goes to ``sleep'' with a lowered PCE (0.4%), and simultaneously decreased J(sc), V-oc and FF, while after visible light treatment, the device is made ``active'' again. The mechanism of the bi-state process involves the different electron mobilities of the isomers. (C) 2015 Elsevier B.V. All rights reserved.
Eutrophication has become a top environmental issue for most lake ecosystems in the world and enhanced phosphorus (P) input is usually considered the primary stressor. Focused on the role of phosphorus in eutrophic lakes, a bibliometric approach was applied to quantitatively evaluate the main interests of research and trends in this area. Using data from the Science Citation Index Expanded database between 1900 and 2013, a total of 3,875 publications was returned by searching topic keywords. Spatial, temporal, and interactive characteristics of the articles, countries, and keywords are presented using time series, frequency, and co-occurrence analysis. Result shows that the annual publications on P in eutrophic lakes keep an exponential growth (R (2) = 0.93; p < 0.0001) over the last two decades, reflecting an increasing attraction in this area. However, publications of phosphorus research make up only 40 % of total records in eutrophic lakes, indicating that there are other significant topics in eutrophication problems of lakes. The USA is the largest output country in this area, contributing 23 % of the total articles, followed by China with a proportion of 15 %. However. China has replaced the USA as the largest output country in the world since 2011, but its citation per paper is significantly lower than the USA, indicating its' favor on quantity over quality. Based on international cooperation analysis, five regional groups were found, and the USA, the UK, P.R. China, Sweden, and German are the centers of their groups. The top 20 title keywords, author keywords and keywords plus were identified according to their frequency to assist our understanding of interests of research and modes. Surprisingly, nitrogen is a high co-occurrence keyword in this study, and its share of publications with P research in eutrophic lakes is increasing rapidly. Furthermore, the high correlation between P and N research in spatial distribution also indicates the increasing significance of N research in eutrophic lakes.