The characteristics of petroleum hydrocarbons and the risks they pose to the ecosystem were studied in the Xihe River, which is an urban river located in Shenyang, China. High levels of aliphatic hydrocarbons (AHc) and polycyclic aromatic hydrocarbons (PAHs) were observed in the river due to the discharge of wastewater from industrial and municipal facilities for a long period of time. High-molecular-weight hydrocarbons, including unresolved complex mixtures (UCM) of n-alkanes between n-C16 and n-C32 and of PAHs with four to six rings, were the dominant hydrocarbons in the river, particularly in suspended particulate matter (SPM) and sediments. The AHc was mainly from petrogenic sources, whereas PAHs was from both pyrolytic and petrogenic source inputs. Our results suggest that there is a high risk of toxicity for the soils and groundwater of the study area. The overall toxicity in the sediments can be described using the toxic equivalent (TEQ) of dibenzo[a,h]anthracene (DBA) based on benzo(a)pyrene (TEQ(BaP)) and dioxins (TEQ(TCDD)) toxic equivalent concentrations. The TEQ values for benzo(a)pyrene (TEQ(BaP)) and dioxins (TEQ(TCDD)) presented a consistent assessment of sediment PAHs. 相似文献
City logistics is a discipline specialized to cope with the sustainability problems encountered in urban freight transport. A key characteristic of it is the heterogeneity of the stakeholders involved. Besides the traditional logistics actors such as shippers, carriers and receivers that share consistent interests (i.e. price and quality), city logistics highly respect the interests of public administrators and citizens that care more about the social welfare. To reach an optimal balance between private and public benefit, it is necessary to understand and in turn forecast the behavior pattern of different groups. In recent years, agent-based modeling has been practiced as an unconventional tool to fulfill this task for its strong capability on capturing the dynamic behavior of individual stakeholders and their interconnections. Referring to other domains (e.g. energy system) where the application of agent-based modeling is relatively mature, a following urgency is to achieve interoperability and in turn reusability between models via introducing formal ontology as a shared template with which developers can standardize their models. This paper introduces an initiative of developing an ontology that formalizes the domain knowledge of city logistics. 相似文献
Stream sediments play an important role in the transport and storage of phosphorus in the stream ecosystems. This research investigated the sorption and fraction of P in the sediments of a long-term seriously contaminated river, the Daliao river system, using isotherm sorption and selective sequentially extraction tests. Results indicated that the total content of P in the sediments was 479–1202 mg kg−1, depending on iron content in the sediments. The content of potential bioavailable P, including soluble and loosely bound P, Al bound P, Fe bound P, and reductant soluble P was only 10–20% of total P in the sediments of the Hun river and Taizi river, while it was 40–55% in the sediments of the Daliao river, the downstream of the river system. Equilibrium phosphorus concentration without net P sorption (EPC0) was from 0.05 to 0.54 mg L−1, with an increasing trend from upstream to downstream, indicating increasingly release potential. On the other hand, the upstream sediment generally sorbed more P than the downstream sediment for each river at the same equilibrium P concentration. The binding energy constant of P on the strong sites of the sediments generally decreased from 2.24 to 2.65 L mg−1 at upstream to 0.41 L mg−1 at downstream or estuary, suggesting that the strong binding sites have been occupied and partly saturated by the phosphate added by point and diffuse sources along the river. On the other hand, molar ratio of Fe to TP contents in the sediments showed sorption capacity of the sediments to P might be under-saturated. The added or sorbed P by the isotherm test was primarily bound to Fe oxides and secondly to Al oxides. Long-term pollution of the river lead to the decrease of P sorption capacity of the river sediment and the increase of P release potential. 相似文献
Eighteen polycyclic aromatic hydrocarbons (PAHs) were analyzed in 29 surface water, 29 suspended particulate matter (SPM), 28 sediment, and 10 pore water samples from Daliao River water system in dry season. The total PAH concentration ranged from 570.2 to 2318.6 ng L(-1) in surface water, from 151.0 to 28483.8 ng L(-1) in SPM, from 102.9 to 3419.2 ng g(-1) in sediment and from 6.3 to 46.4 microg l(-1) in pore water. The concentration of dissolved PAHs was higher than that of particulate PAHs at many sites, but the opposite results were generally observed at the sites of wastewater discharge. The soluble level of PAHs was much higher in the pore water than in the water column. Generally, the water column of the polluted branch streams contained higher content of PAHs than their mainstream. The environmental behaviors and fates of PAHs were examined according to some physicochemical parameters such as pH, organic carbon, SPM content, water content and grain size in sediments. Results showed that organic carbon was the primary factor controlling the distribution of the PAHs in the Daliao River water system. Partitioning of PAHs between sediment solid phase and pore water phase was studied, and the relationship between logK(oc) and logK(ow) of PAHs on some sediments and the predicted values was compared. PAHs other than naphthalene and acenaphthylene would be accumulated largely in the sediment of the Dalaio River water system. The sources of PAHs were evaluated employing ratios of specific PAHs compounds and different wastewater discharge sources, indicating that combustion was the main source of PAHs input. 相似文献
Computer chip is always accompanied by the increase of heat dissipation and miniaturization.The miniature heat pipes are widely used in notebook computer to resolve the heat dissipation problems.Maximum heat removed model of miniature heat pipes building by grey model is presented.In order to know the foundation for modeling,the smooth grade of error examination is inquired and the accuracy of grey relational grade is verified.The model can be used to select a suitable heat pipes to solve electric heat problems in the future.Final results show that the grey model only needs four experiment data and its error value is less than 10%,further,it is better than computational fluid dynamics (CFD) model. 相似文献
Neutral water splitting is attractive for its use of non-corrosive and environmentally friendly electrolytes. However, catalyst development for hydrogen and oxygen evolution remains a challenge under neutral conditions. Here we report a simple electrodeposition and reductive annealing procedure to produce a highly active Ni-Co-Cr metal/metal oxide heterostructured catalyst directly on Ni foam. The resulting electrocatalyst for hydrogen evolution reaction (HER) requires only 198 mV of overpotential to reach 100 mA/cm2 in 1 M potassium phosphate (pH = 7.4) and can operate for at least two days without significant performance decay. Scanning transmission electron microscopy coupled with electron energy loss spectroscopy (STEM-EELS) imaging reveals a Ni-Co alloy core decorated with blended oxides layers of NiO, CoO and Cr2O3. The metal/metal oxide interfaces are suggested to be responsible for the high HER activity.