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There are enormous differences in benzo[a]pyrene (BaP) acute toxicity tests on Daphnia magna, according to previous publications. The explanations of the reasons for this extreme variation are necessary. In this context, the acute toxicity tests of different experiment conditions (light/dark, culture medium, and solvent) were conducted on Daphnia magna with BaP as the toxicant of concern. Based on the experiments above, molecular dynamics (MD) simulations were employed to investigate the mechanisms of action. According to our results, the significant influence of light exposure on the acute toxicity test of BaP (p < 0.05) on D. magna was recorded. On the basis of the MD simulations, it was possible that BaP may not affect the normal operation of Superoxide Dismutase and Catalase directly, and it could be quickly transferred from the body through Glutathione S-transferase and Cytochromes P450. Therefore, when exposed to light, the oxidative stress process intensifies, causing damage to Daphnia magna. Apparently, the ecotoxicity tests based on inhibition for D. magna cannot adequately reflect the toxic effects of BaP. [ABSTRACT FROM AUTHOR]

A compatible relationship between "man" and "land" is the essence of regional sustainable development. In this article VENSIM PLE is used to set up a system dynamics (SD) model of the regional man-land system of Xiangfan, Hubei Province, China. The model is used to simulate dynamic behaviors of society and economy in the face of environmental catastrophe, in order to explore dynamic response among subsystems in man-land systems, and to research mechanisms of regional sustainable development. The model is also used to forecast impacts from the south- to-north water transfer project in China on the environment, society and economy within a time span of 50 years. The model is further used to verify the effects of suggested regulatory policies. The simulation results show counterintuitive outcomes. The most serious impact on Xiangfan caused by the water transfer project would be on economic growth, not on environment quality. However, if a series of regulatory policies were carried out in advance of the water project's construction, the trends of concern could be effectively eased. SD provides tools for precisely understanding complex man-land systems, which always seem counterintuitive. However, there still exist limitations and disadvantages in the model that must be overcome. It is believed that the next logical step in deriving better dynamic models of man-land systems is to integrate SD with other advanced algorithms or technologies. [ABSTRACT FROM AUTHOR]

Objective: To recognize and assess the impact of the South-to-north Water Transfer Project (SNWTP) on the ecological environment of Xiangfan, Hubei Province, situated in the water-out area, and develop sound scientific countermeasures., Methods: A three-layer BP network was built to simulate topology and process of the eco-economy system of Xiangfan. Historical data of ecological environmental factors and socio-economic factors as inputs, and corresponding historical data of ecosystem service value (ESV) and GDP as target outputs, were presented to train and test the network. When predicted input data after 2001 were presented to trained network as generalization sets, ESVs and GDPs of 2002, 2003, 2004... till 2050 were simulated as output in succession., Results: Up to 2050, the area would have suffered an accumulative total ESV loss of RMB104.9 billion, which accounted for 37.36% of the present ESV. The coinstantaneous GDP would change asynchronously with ESV, it would go through an up-to-down process and finally lose RMB89.3 billion, which accounted for 18.71% of 2001., Conclusions: The simulation indicates that ESV loss means damage to the capability of socio-economic sustainable development, and suggests that artificial neural networks (ANNs) provide a feasible and effective method and have an important potential in ESV modeling.