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1.
Ping Ding ChengDe Shen Ning Wang WeiXi Yi XingFang Ding DongPo Fu KeXin Liu Ping Zhao 《科学通报(英文版)》2010,55(23):2548-2556
Carbon isotopic compositions of soil CO2 in rainy season (July) from two natural soil profiles (DHLS & DHS) in the monsoon evergreen broadleaf forest in the Dinghushan Biosphere Reservoir (DBR), South China, are presented. Turnover and origins of soil CO2 are preliminarily discussed in this paper. Results show that the content of soil CO2 varies between 6120 and 18718 ppmv, and increases with increasing depth until 75 cm, and then it declines. In DHLS, soil CO2 δ13C ranges from −24.71‰ to −24.03‰, showing a significant inverse correlation (R2=0.91) with the soil CO2 content in the same layer. According to a model related to soil CO2 δ13C, the soil CO2 is mainly derived from the root respiration (>80%) in DHLS. While in DHS, where soil CO2 ? 13C ranges from −25.19‰ to −22.82‰, soil CO2 is primarily originated from the decomposition of organic matter (51%–94%), excluding the surface layer (20 cm, 90%). Radiocarbon data suggest that the carbon in soil CO2 is modern carbon in both DHLS and DHS. Differences in 14C ages between the “oldest” and “youngest” soil CO2 in DHLS and DHS are 8 months and 14 months, respectively, indicating that soil CO2 in DHLS has a faster turnover rate than that in DHS. The 14C values of soil CO2, which range between 100.0‰ and 107.2‰ and between 102.5‰ and 112.1‰ in DHLS and DHS, respectively, are obviously higher than those of current atmospheric CO2 and SOC in the same layer, suggesting that soil CO2 is likely an important reservoir for Bomb-14C in the atmosphere. 相似文献
2.
The level of atmosphericΔ14C and the fossil fuel derived CO 2 concentration in the Beijing area from May to September,2009, were systematically analyzed based on radiocarbon(14C)measurements of annual plants by accelerator mass spectrometry(AMS). The results show that the maximumΔ14C in Beijing was 29.6‰±2.2‰,and the minimum was–28.2‰±2.5‰,with a trend of decreasingΔ14C from the outer suburbs to inner suburbs to the urban center.This trend correlates well with increases in fossil fuel derived CO2 caused by human activities such as population density,industrial emissions and traffic,with lower values of atmosphericΔ14C associated with more intensive human activities.The fossil fuel derived CO 2 concentrations from May to September, 2009,ranged from 3.9±1.0 ppm to 25.4±1.0 ppm.It was calculated that each additional 1 ppm of CO2 from fossil fuels depleted the atmosphericΔ14C by approximately 2.70‰.This study suggests that 14C measurements of annual plants by AMS provide an effective method to rapidly trace fossil fuel derived CO2. 相似文献
3.
Zhongqin Li Mingjun Zhang Dahe Qin Cunde Xiao Lide Tian Jiancheng Kang Jun Li 《科学通报(英文版)》1999,44(24):2270-2270
Snow and firn samples recovered from two snow pits (2.5 and 4.5m deep) and one 50-m firn core along the route of the 1996/1997 Chinese First Antarctic Inland Traverse Expedition in Princess Elizabeth Land, East Antarctica, have been measured for chemical composition and oxygen isotope ratio. In the two snow pits, the variations of NO3- are partly in phase with that of δ18O, while the variations of Cl~ and Na+ are in inverse phase with that of δ18O. The variations of CI- , Na+ , NO3- and δ18O show obvious seasonal variations and annual stratag-raphy. However, with the depth increasing, the seasonal variations of δ18O are gradually smoothed below 3 m (corresponding to about 10-year mass accumulation) in depth while the seasonal variations of Cl- , Na+ and NO3- are kept fairly well in the whole profile of the 50-m firn core (corresponding to about 250-year mass accumulation). The results provide a useful tool for dating the snow stratum in this region. On the contrary, no obvious seasonal variations of Ca2 + are found in the profiles. 相似文献
4.
Tian XiaoSi Zhu Cheng Sun ZhiBin Shui Tao Huang YunPing Flad Rowan Kimon Li YuMei 《科学通报(英文版)》2011,56(2):169-178
Based on AMS 14C dating data, carbon and nitrogen isotope analyses were conducted on mammal bone collagen of deer, cattle and pigs from the Zhongba site in the Three Gorges Reservoir region of the Yangtze River. These analyses were conducted to reconstruct palaeodiets of mammals, palaeoecology, palaeoenviroment and previous human activities in the study area. Results show that the collagen loss of bone did not change the in vivo isotopic composition of carbon and nitrogen stable isotopes, and most of the bone fossils were well preserved. The bone collagen of samples from deer had a mean δ13C of -23.1‰ and a mean δ15N of 4.7‰, suggesting that deer subsisted in a closed habitat and fed on branches and leaves. The bone collagen of cattle had a mean δ13C of –19.6‰ and a mean δ15N of 5.2‰, which indicates that cattle subsisted in an open habitat and fed on grasses and stems. The δ13C values show that both deer and cattle fed on C3 plants and lived in the same ecosystem, but the t-test results show that deer δ13C and δ15N values were both more negative than those of cattle, indicating that they inhabited different niches. The δ13C and δ15N values of cattle partially overlapped those of deer, suggesting some competition in diets between them. The t-tests show that the δ13C and δ15N values of pigs were more positive than those of cattle and deer, which signifies that pigs occupied a higher trophic level compared to cattle and deer. The wide range of pig δ13C values demonstrates that pig trading had been taking place from early Neolithic Age to late Bronze Age. There were no significant differences in deer δ13C and δ15N values among different archaeological periods, making it clear that climatic, ecological and environmental conditions were kept relatively stable from 2200 to 4200 a BP. This stability may have been responsible for the extensive and complete cultural layers at the Zhongba site. The minimum number of samples required to estimate the mean δ13C values of deer, pigs and cattle are 8, 73 and 16, respectively, and for mean δ15N values of deer, pigs and cattle, the minimum numbers are 4, 5 and 6, respectively. 相似文献
5.
We studied the records of elemental carbon (EC) of the last 21 ka in the Weinan loess section, Shanxi Province. The variations
of EC abundance and δ13CEC value along with depth (or age) were presented. There are four large peaks of EC abundance around the following years: 20.16
ka, 17.76 ka, 11.97 ka and 4.49 ka. Climatic situation was changed rapidly during these periods. The peaks around 11.97 ka
and 20.16 ka are particularly sharp, occurring over intervals of tens to hundreds of years, which could represent short-duration
intense events. δ13CEC values in the upper 4 m of the Weinan loess section vary between −11.71‰ and −21.34‰, which suggests that the vegetation
pattern of the last 21 ka on the Loess Plateau is C4-dominated grasses. 相似文献
6.
A murine CD4+ thymocyte subset with phenotype of TCRαβ+ 3G11− 6C10− CD4+ CD8− CD69+/- HSAmed/lo contains the cells in relatively functional matured status. The functional property of the cells in this subset is characterized
by the unique pattern of cytokine production at transitional stage from Th0 to Th2 type with the latter being the dominant
type. After being co-cultured with murine thymic medullary epithelial cell line (MTEC1) cells, a murine thymic medullary type
epithelial cell line, the TCRαβ+ 3G11− 6C10− CD4+ CD8− CD69+/- HSAmed/lo thymocytes, has exhibited significantly higher levels of proliferation capability and IL-6 production, whereas the production
of IL-4 and IL-10 is suppressed after co-culturing with MTECl. By contrast, MTECl could not induce thymocytes to secrete Thl
type of cytokines. The results suggest that MTECl can regulate functional status of this thymocyte subset and induce them
to develop into a specialized Th2 subset. 相似文献
7.
Phenotypic analysis of the medullary-type CD4 CD8+ (CD8SP) thymocytes has revealed phenotypic heterogeneity within this cell population. The phenotype of mature peripheral
CDS+T cells is TCRαβ+CD3+Qa-2+HSA 3G11−6C10, whereas in the medullary-type CD8SP thymocytes, 20% are Qa-2+; 33%, HAS; 30%, 3G11; and 70% are 6C10. The disparate expression patterns of these four cell surface markers suggest that
medullary-type CD8SP thymocytes may undergo phenotypic maturation process. According to the distribution of these four cell
surface markers, six subgroups of CD8SP thymocytes have been identified. The precursor-progeny relationship along with developmental
pathway is postulated as follows: 6C10+HSA+3G11 Qa-2→ 6C10+HSA+ 3G11+Qa-2 → 6C10 HSA+3G11+Qa-2 → 6C10−HSA−3G11+Qa-2 → 6C10−HSA−3G11 Qa-2 → 6C10−HA S 3G11 Qa-2+, the cells in the last subgroup exit the thymus and home into periphery. 相似文献
8.
The Na^+/H^+ antiporter plays key roles in maintaining low cytoplasmic NaNa^+ level and pH homeostasis, while little is known about the Carboxyl-terminal hydrophilic tails of prokaryotic antiporters. In our previous study, the first Na^+/H^+ antiporter gene nhaH from moderate halophiles was cloned from Halobacillus dabanensis D-8 by functional complementation. A topological model suggested that only nine amino acid residues (^395PLIKKLGMI403) existed in the hydrophilic C-terminal domain of NhaH. The C-terminal truncated mutant of NhaH was constructed by PCR strategy and designated as nhaH△C. Salt tolerance experiment demonstrated that the deletion of hydrophilic C-terminal nine amino acid residues significantly inhibited the complementation ability of E. coil KNabc, in which three main Na^+/H^+ antiporters nhaA, nhaB and chaA were deleted. Everted membrane vesicles prepared from E. coil KNabc/nhaHAC decreased both Na^+/H^+ and Li^+/H^+ exchange activities of NhaH, and also resulted in an acidic shift of its pH profile for Na^+, indicating a critical role of the short C-terminal domain of NhaH antiporter in alkali cation binding/translocation and pH sensing. 相似文献
9.
The binding reaction between 10-hydroxycamptothecin (10-HCPT) and human serum albumins (HSA) is studied by means of fluorescence
spectroscopy, UV-Vis absorption spectrum, 1H NMR spectrum, and molecular simulation. The results indicate that the binding
reaction of 10-HCPT and HSA is a single static quenching process, and the binding equilibrium constant for 10-HCPT binding
with HSA is estimated K
0= 4.93×104 L · mol−1 at 25 °C with the molar ratio of 1:1. The distance (r) and energy transfer efficiency (E) between donor (HSA) and acceptor (10-HCPT) are obtained as follows, r =3.51 nm; E =0.27. The enthalpy change (ΔH
⦵) and entropy change (ΔS
⦵) are calculated at different temperatures, and the hydrophobic force and shidipole force are the functions in the reaction.
The results show that 10-HCPT binds within the subdomain II A of HSA by the hydrophobic force, and the 10-OH and 20-OH of
10-HCPT bind with both residue Leu-238 of HSA and Ala 291 of HSA by hydrogen bonds.
Biography: LI Guizhi(1962–), female, Associate professor, research direction: organic analysis. 相似文献
10.
Determination of trophic relationships within a Bohai Bay food web using stable δ15N and δ13C analysis 总被引:2,自引:0,他引:2
WANYi HUJianying ANLihui ANWei YANGMin ItohMitsuaki HattoriTatsuya TAOShu 《科学通报(英文版)》2005,50(10):1021-1025
This study measured stable carbon and nitrogen isotope ratios in phytoplankton, zooplankton, five invertebrates species, eight fishes species and three seabirds species collected in Bohai Bay. δ^13C ranged from -25.38‰ to -11.08‰ showing a relative low enrichment in the food web from Bohai Bay. The mean δ^13C of mullet is higher than that of other organisms, and this might be due to that mullet is migration fish and feeds mainly on inshore sources. δ^15N ranged from 4.08‰ to 13.98‰, and showed a step-wise enrichment with trophic level of 3.8‰. The δ^15N enrichment factor was used to construct an isotopic food web model to establish trophic relationships within this marine food web. According to this model, exact trophic levels of all organisms were estimated as 1.46-2.10, 1.91-3.32, 2.55-4.23 and 2.98-4.28 for plankton, invertebrates, fishes, and seabirds. 相似文献
11.
Highly precise 40Ar-39Ar dating results demonstrate that the ages of potash-rich volcanic rocks in western Shandong Province are 114.7–124.3 Ma,
and that of the lamprophyres is 119.6 Ma. The potash-rich volcanic rocks have relatively high (87Sr÷86Sr)i ratios (0.708715–0.711418) and distinctly negative εnd values (−11.47–−17.54), and are enriched in radiogenic lead (206Pb÷204Pb=17.341−17.622, 207Pb÷204Pb=15.525−15.538, 208Pb÷204Pb = 37.563−37.684). Similarly, the lamprophyres also have quite low εnd values (−11.57–−19.64). Based on the fact that the Sr, Nd and Pb isotopic compositions of potash-rich volcanic rocks are
very consistent with that of the clinopyroxene separates, and by integrating comprehensive analyses of their tectonic settings,
and extensive comparisons of the Sr, Nd isotopic compositions with that of the related simultaneous rocks, it is concluded
that the potash-rich volcanic rocks and lamprophyres in western Shandong Province were most possibly derived from the partial
melting of enriched mantle which was caused by source contamination and metasomatism of subducted continental crustal materials. 相似文献
12.
Carbon isotope ratios (δ13C) of plants, litter and soil organic matter (0–5 cm, 5–10 cm and 10–20 cm) on the eastern slope of Mount Gongga were measured. The results show that δ13C values of plants, litter and soil organic matter all decrease first and then increase with altitude, i.e δ13C values gradually decrease from 1200 to 2100 m a.s.l., and increase from 2100 to 4500 m a.s.l. The δ13C altitudinal variations are related to the distribution of C3 and C4 plants on the eastern slope of Mount Gongga, because C4 plants are observed to grow only below 2100 m, while C3 plants occur at all altitudes. There are significantly positive correla-tions among δ13C of vegetation, δ13C of litter and δ13C of soil organic matter, and litter, 0–5 cm, 5–10 cm and 10–20 cm soil or-ganic matter are 0.56‰, 2.87‰, 3.04‰ and 3.49‰ greater in δ13C than vegetation, respectively. Considering the influences of rising concentration of atmospheric CO2 and decreasing δ13C of atmospheric CO2 since the industry revolution on δ13C of plants, 1.57‰ is proposed to be the smallest correction value for reconstruction of paleovegetation using δ13C of soil organic matter. 相似文献
13.
Variation of soil Δδ13C values in Xifeng loess-paleosol sequence and its paleoenvironmental implication 总被引:1,自引:0,他引:1
NING Youfeng LIU Weiguo AN Zhisheng 《科学通报(英文版)》2006,51(11):1350-1354
The carbon isotopic compositions of soil organic matter (SOM) and total carbonate (TC) in Xifeng Ioess-paleosol sequence have been studied. The δ^13CsoM values vary from -23.8‰ to -20.2‰, which are higher in interglacial than in glacial stages. Contrary to δ^13Csoi values, the δ^13CTc values vary from -8.5‰ to -3.6‰ and are lower in interglacial than in glacial stages. The differences (△δ^13C) between the δ^13CsoM and δ^13CTc values vary from 14.1‰ to 19.4‰. Our results from the Xifeng loesspaleosol sequence indicate that the △δ^13C values represent the ratio of primary carbonate (PC) to secondary carbonate (SC). The △δ^13C values were high in the loess stages, and the maximal PC-to-SC ratio can reach 6:4. But in the paleosol stages, the △δ^13C values were low, with a small proportion of PC. The △δ^13C values in Ioess-paleosol sequence also indicate the contributions of the dust to the loess sediment in the Chinese Loess Plateau because the dust contains the PC. 相似文献
14.
Export and remineralization of POM in the Southern Ocean and the South China Sea estimated from 210Po/210Pb disequilibria 总被引:1,自引:0,他引:1
Disequilibria between ^210Po and ^210Pb in the upper water and their potential applications as a proxy of particle export and remineralization were examined in the Southern Ocean (station IV3) and the South China Sea (NS44). ^210po was deficit in surface waters but excessive relative to ^210Pb in subsurface waters. Good positive correlation between ^210Po and particulate organic carbon (POC) indicated deficits and excess of ^210Po resulted from particulate organic matter (POM) export and remJneralization respectively, which was also supported by the decreased δ^13C and increased δ^15N downwards as a result of particle remineralization. On the basis of ^210Po/^210Pb box-model, POC export flux out of the surface waters were 1.2 mmol C. m^-2. d^-1 and 2.3 mmol C. m^-2. d^-1 for station NS44 and IV3, respectively. In the subsurface waters, remineralization fluxes of ^210Po were 0.062 Bq. m^-2.d^-1 and 0.566 Bq.m^-2.d^-1 for station NS44 and IV3 along with the recycle efficiency of 52±26% and 119±52%, respectively. Remineralized fluxes of POM derived from ^210Po and exported POC were 0.6 mmol C.m^-2.d^-1 and 2.7 mmol C. m^-2. d^-1 for NS44 and IV3. This study suggested that ^210Po was a powerful tracer of particle export and remineralization. 相似文献
15.
This study deals with δ13 C variation in karst soil system of Yaji Karst Experiment Site, Guilin, a typical region of humid subtropical karst formations.
Samples of near ground air, plant tissue, soil and water (soil solution and karst spring) were respectively collected on site
in different seasons during 1996–1999. Considerable variation of δ13 C values are not only found with different carbon pools of soil organic carbon, soil air CO2 and soil water HCO3−, but also with the soil depths and with different seasons during a year. The °13 C values of CO2 both of near ground air and soil air are lower in July than those in April by 1‰–4‰ PDB. Our results indicate that the δ13 C values of carbon in the water and air are essentially dependent on interface carbon interaction of air-plant—soil-rock—water
governed by soil organic carbon and soil CO2 in the system. 相似文献
16.
Southwest monsoon changes indicated by oxygen isotope of ostracode shells from sediments in Qinghai Lake since the late Glacial 总被引:5,自引:0,他引:5
LIU XingQi SHEN Ji WANG SuMin WANG YongBo LIU WeiGuo 《科学通报(英文版)》2007,52(4):539-544
The δ 18O records of ostracode shells in sediments of core QH-2000 from Qinghai Lake can be used as a better proxy to reflect monsoon changes. Low monsoon precipitation between 17.5 and 11 cal. ka BP is indicated by positive δ 18O values averaging 2.37‰. A fast shift in δ 18O from positive at 11 cal. ka BP to negative at 10 cal. ka BP indicates sharp increase of monsoon precipitation. An interval of generally high monsoon precipitation is observed between 10 and 6 cal. ka BP with δ 18O values averaging -2.15‰. Decrease of monsoon precipitation between 6 and 2.5 cal. ka BP is indicated by positive δ 18O values. δ 18O keeps positive values averaging 3.0‰ between 2.5 and 0 cal. ka BP suggesting low high monsoon precipitation. The climatic changes indicated by δ 18O records of ostracode shells in sedi- ments of core QH-2000 from Qinghai Lake and our broader regional comparison show that the climate in Qinghai Lake since the late Glacial is probably controlled by southwest monsoon other than southeast monsoon. 相似文献
17.
Preliminary results of the study on wind erosion in the Qinghai-Tibetan Plateau using137Cs technique
The worldwide fallout of caesium-137 (137Cs) associated with the nuclear weapon tests during the 1950s and 1960s has provided a valuable man-made tracer for studies
of soil erosion and sediment delivery. But relatively few researchers have used it to estimate wind erosion. In this note,
the137Cs technique is introduced into the studies of wind erosion and its modern processes in the Qinghai-Tibetan Plateau. Two137Cs reference inventories of 982.11 and 2 376.04 Bq · m−2 were established preminarily, distributed in the south and middle-north parts of the studied area respectively. By analyzing
the patterns of137Cs depth profiles from sampling sites, the aeolian processes of erosion and deposition in nearly 40 years have been revealed,
i.e. the shrub coppice dunes (S1) and semi-fixed dunefields (S3) experienced the alternation of erosion and deposition, while
the grasslands (S4, S6 and S7) and dry farmlands (S5) suffered erosion only. By using137Cs model, the average wind erosion rates for shrub coppice dune (S1), semi-fixed dune fields (S3), dry farmlands (S5) and
grasslands (S4, S6 and S7) were estimated to be 84.14, 69.43, 30.68 and 21.84 t · ha1 · a−1 respectively, averaging 47.59 t · ha−1 · a−1 for the whole plateau, which can be regarded as of the medium erosion standard. These results derived from Cs for the first
time have significant implications for the further research of wind erosion and desertification control in the Qinghai-Tibetan
Plateau. 相似文献
18.
Isotopic composition of atmospheric water vapor before and after the monsoon’s end in the Nagqu River Basin 总被引:4,自引:0,他引:4
YU Wusheng YAO Tandong TIAN Lide WANG Yu YIN Changliang 《科学通报(英文版)》2005,50(23):2755-2760
Atmospheric water vapor samples were collected in the Nagqu River Basin in the middle of Tibetan Plateau between August and October in 2004. Results show that there exist some fluctuations of the δ^18O of atmospheric water vapor, especially before and after the monsoon's end.Moreover, the variety trend of the δ^18O of atmospheric water vapor inverse correlates with that of dew point. Precipitation events make an important effect upon the variation of δ^18O of atmospheric water vapor. During the whole sampling period, the δ^18O values of atmospheric water vapor are low while precipitation events occurred. The moisture origins w also contribute to the variation of δ^18O of atmospheric water vapor. The oceanic moisture transported by the southwest monsoon results in lower δ^18O of atmospheric water vapor in the Nagqu River Basin. Compared with the influence of the oceanic moisture, the δ^18O values, however, appear high resuiting from the effect of the continental air mass in this region. 相似文献
19.
Surface soil samples collected over a high spatial resolution in eastern China were analyzed for carbon isotope composition (δ^13C) of total organic carbon (TOC) and higher plant-derived long-chain n-alkanes, with the latter reported as weighted mean values. The two sets of δ^13C values are significantly correlated and show similar trends in spatial variation. The spatial distribution of δ^13C shows less negative values in the mid-latitudes between 31°N and 40°N and more negative ones at higher and lower latitudes. This is consistent with previously reported carbon isotope data from surface soil phytoliths in the same region and suggests that the mid-latitude area provides relatively favorable growing condi- tions for C4 plants. Furthermore, δ^13C values of both TOC and long-chain n-alkanes from 12 surface soil samples collected from a small grassland in north China displayed similar carbon isotope values and the difference between paired δ^13C of a soil samples remains relatively constant. Our data demonstrate that in eastern China, soil δ^13C composition of both TOC and long-chain n-alkanes is effective indicators of C3/C4 ratios of the prevailing vegetation. This work suggests that -22‰ and -32‰ are good es- timated end members for the weighted mean δ^13C values of long-chain n-alkanes (C27, C29 and C31 n-alkanes) from soils under dominant C4 or C3 vegetation, allowing us to reconstruct paleovegetation trends. 相似文献
20.
SONG Zhiguang WANG Cuiping 《科学通报(英文版)》2006,51(14):1736-1740
The methanogenic archaea and sulfate reduction bacteria are flourishing in the sediments associated with gas venting and gas hydrate settings on the sea floor, where the anaerobic oxidation of methane (AOM) me-diated by these bacteria is the dominant path… 相似文献