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Based on the actual operation scenario of metro, this paper proposes an uneven parameter stray current distribution model. The model combines the calculation method of multi-section traction power supply of metro and establishes an uneven parameter stray current distribution model in different calculation domains with the metro operation position and the traction substation position as the boundary points. The improved dynamic boundary conditions were used to calculate the model. Compared with the experimental data, the average maximum deviation between the two was 0.677. Meanwhile, the dynamic space–time distribution characteristics of stray current and the change law of rail-to-ground voltage were obtained through simulation analysis. In addition, the calculation model for ground potential gradient distribution under stray current interference was established by discretizing stray currents within each calculation domain, and the characteristics of ground potential gradient distribution were simulated and analyzed. The results showed that the distribution period of stray current was approximately equal to the headway, and the waveform change lagged behind the rail-to-ground voltage. The fluctuation degree of ground potential gradient was obviously affected by the length of power supply interval and train operation conditions. [ABSTRACT FROM AUTHOR]

Based on the results of the National Survey of Peat Resources (1983-1985) and the investigation results on the peatlands of China, the storage and density of the organic carbon in the peatlands of China were estimated. The total organic carbon storage (OCS) of the peatlands in China, including bare peatlands and buried peatlands, are 1.503 × 10 t, unevenly distributed over 30 provincial level administrative units and 16 climatic zones. Peatland organic carbon storage (POCS) in Sichuan (6.45 × 10 t) and Yunnan provinces (2.91 × 10 t) is the highest, accounting for 62.29% of the total POCS. Humid zone of plateau has the highest POCS of 7.14 × 10 t, especially in the Zoigê Plateau, where the POCS is 6.30 × 10 t, accounting for 41.92% of the total POCS of China. The organic carbon density (OCD) of the peatlands in China mostly ranges from 80 kg/m to 140 kg/m, and the range of the maximum is 270-360 kg/m, and the minimum is less than 80 kg/m. Divided by the Yanshan Mountain, Taihang Mountains and Hengduan Mountains, the peatland oganic carbon density (POCD) is lower on the northwestern side than that on the southeastern side. Jiangxi Province has the highest POCD due to the ancient buried peatlands. The OCD of the bare peatlands is mostly in the range of 60-150 kg/m, and that of the buried peatlands is more than 100 kg/m. In the bare peatlands, the OCD generally increases from the surface layer to the below surface layer, and then decreases with the depth. Although the peatlands area in China is small, the OCS per unit area is far higher than the other soil types, so peatlands protection can effectively mitigate climate change. [ABSTRACT FROM AUTHOR]

The regularity of CH4 emission from marshland in the Sanjiang Plain was studied by sampling in the open field and analyzing under laboratory condition, the annual emission amount is also estimated. By Grey Relatively Analysis we know that the soil temperature in the 10-cm depth of grass-root layer is close related with CH4 emission. CH4 emission has different kinds of diurnal emission modes:before-dawn maximum mode, night maximum mode and irregular fluctuation mode. The seasonal variation trend of CH4 emission rates is going up steadily from May to August and dropping down from September, the maximum lies behind the maximum of temperature. CH4 emission rates of different marshland types are different, the CH4 emission rate of Glyceriaspiculosa — Carex marshland is always higher than that of Carex lasiocarpa marshland. The paper also studies the difference of CH4 emission rates in different managing modes and analyzes the emission rates between China and U. S. A. The result shows: the average value of CH4 emission rate is 17.26mg/(m2·h), the annual amount of CH4 emission is about 0.75Tg. [ABSTRACT FROM AUTHOR]

The Sanjiang Plain of China is a low plain. Its total area is 10.89×104 km2 and marsh area takes up 10.20%. Marsh is a kind of vegetation type with strong carbon-fixing ability among the terrestrial ecosystem and carbon cycle performing in the form of carbon dioxide. This paper discusses the fixation of atmospheric CO2 by marsh plant; the transfer of carbon from marsh to atmosphere; the change of CO2 and vertical transfer of CO2 near atmosphere of the earth; the carbon flow among marsh plants, soil and atmosphere. Some scientific data about the biological production, carbon content of marsh plants and the capacity for releasing and fixing are used to explain the carbon cycle of marsh in the Sanjiang Plain. [ABSTRACT FROM AUTHOR]

There is limited information available on CO2 concentration and flux over marsh. The objective of this work was to characterize CO2 concentration and flux within and above marsh plant ( Carex lasiocarpa Ehrh. and C. pseudocuraica F. Schm) canopy at heights 0.5, 1.0 and 1.5 m. CO2 concentration was measured sequentially every 3 hours by using an infrared gas analyzer. Soil and air temperature, wind speed, net radiation and soil heat flux were also measured simultaneously. Extremely daily minimum and maximum CO2 concentration ranged from 250 to 754 µmd/mol for the 4-year work. The typical minimum and maximum values ranged from 314 to 464 µmol/mol at the height of marsh plant (about 0.5 m) during the fruiting period and mature date. The seasonal changes in CO2 concentration show that the minimum CO2 concentration occurred in the fruiting period and mature date, and both of their minimum values were 314 µmol/mol. This illustrates that CO2 consumed by photosynthesis was stable during the period. The flux of CO2 can be thought as a turbulent diffusion phenomenon. By micrometeorological methods, the diurnal CO2 fluxes were measured in the flowering period, fruiting period, early mature date, late mature date and yellow-ripe stage. Their values were −0.18, 38.15,24.13,10.9 and 4.91 µmol/mol respectively. [ABSTRACT FROM AUTHOR]

Mire is the product of the Quaternary. It mostly formed, developed and declined after the postglacial age. Therefore the chemical element analysis, spore-pollen analysis,C dating, mire plant determination for mire sediment, and the study on hierarchy relation of mire sediment, can provide a lot of information for restoring paleogeography, paleoclimate and environmental change. So some people called mire sediment-peat as 'database of environment'. [ABSTRACT FROM AUTHOR]