In recent years, scientists have been increasingly interested in the energy embodied in traded goods among countries. In this article, the direct energy intensities in various economic sectors of China were calculated with the data of energy consumption and output value of each sector, and the input-output table was used to estimate the external energy consumption. The total energy intensity of all sectors was then obtained. From the data of international trade, the energy embodied in goods trade of China was estimated for the period of 1994-2001. During this period, the average energy intensity of imported goods was always higher than that of exported ones. As a country with a surplus in international goods trade, China actually imported net embodied energy in the past few years. The net embodied energy imported was at the same magnitude of the imported energy in the form of fossil fuels. 相似文献
Concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) in soil, moss and reindeer dung collected at Ny-Ålesund of the Arctic were measured to investigate their accumulation trends and distribution in the three compartments. Compared with the other regions, the proportions of 2 + 3 ring PAHs to the total PAHs were higher, whereas the proportions of 5 + 6 ring PAHs were lower in the three compartments at Ny-Ålesund. Significant log/log-linear relationship was observed between the sub-cooled liquid vapor pressure MathML source" title="View the MathML source" align="absbottom" border="0" height=18 width="26"/> and the soil/moss quotient (QSM). The relation was similar to the relationship between the gas/particle partition coefficient (KP) and MathML source" title="View the MathML source" align="absbottom" border="0" height=18 width="19"/> of PAHs, implying QSM would be a “mirror image” of KP. Excellent log/log-linear relationships were observed between QSM and KOA as well as between the moss/dung quotient (QMD) and KOW. The results presented here indicate the physicochemical properties are suitable for characterizing the distribution of PAHs in soil, moss and reindeer dung. 相似文献
Uptake of organic contaminants by plant roots consists of two consecutive steps: sorption to plant roots and entrance into root xylem tissues through epidermal and endodermic membranes. Most research pertaining to phytoremediation assumed that sorption to plant roots is linear and non-competitive. A growing body of evidence, however, is suggesting that sorption to plant roots is nonlinear and competitive. The objective of this study was to examine the concentration effects of chemical constituents on the competitive sorption of trichloroethylene (TCE) and tetrachloroethylene (PCE) to the roots of Typha latifolia. Competitive sorption was clearly demonstrated by the reduced sorption of TCE and PCE in bi-solute systems than in single-solute systems. Concentration is an important factor affecting the extent of competition. In bi-solute systems, the PCE/TCE ratio on root surface approximately reflected the contaminant footprints in solution. The result was attributed to limited high energetically favorable sorption sites on the root surface and similar sorption mechanisms of TCE and PCE. The results hold significant importance for the application of phytomonitoring of organic contaminant mixtures. 相似文献
The relationship between the improvement of sludge dewaterability and variation of organic matters has been studied in the process of sludge pre-conditioning with modified cinder, especially for extracellular polymeric substances (EPS) in the sludge. During the conditioning process, the decreases of total organic carbon (TOC) and soluble chemical oxygen demand (SCOD) were obviously in the supernatant especially for the acid modified cinder (ACMC), which could be attributed to the processes of adsorption and sweeping. The reduction of polysaccharide and protein in supernatant indicated that ACMC might adsorb EPS so that the tightly bound EPS (TB-EPS) decreased in sludge. In the case of ACMC addition with 24 g·L–1, SRF of the sludge decreased from 7.85 × 1012 m·kg–1 to 2.06 × 1012 m·kg–1, and the filter cake moisture decreased from 85% to 60%. The reconstruction of “floc mass” was confirmed as the main sludge conditioning mechanism. ACMC promoted the dewatering performance through the charge neutralization and adsorption bridging with the negative EPS, and provided firm and dense structure for sludge floc as skeleton builder. The passages for water quick transmitting were built to avoid collapsing during the high-pressure process.