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991.
JGOFS results showed that the ocean is a major sink for the increasing atmospheric carbon dioxide resulting from human activity.
However, the role of the coastal seas in the global carbon cycling is poorly understood. In the present work, the inorganic
carbon (IC) in the Yangtze River Estuary and Jiaozhou Bay are studied as examples of offshore sediments. Sequential extraction
was used to divide inorganic carbon in the sediments into five forms, NaCl form, NH3 H2O form, NaOH form, NH2OH HCl form and HCl form. Studied of their content and influencing factors were also showed that NaCl form < NH3 H2O form<NaOH form < NH2OH HCl form<HCl form, and that their influencing factors of pH, Eh, Es, water content, organic carbon, organic nitrogen, inorganic
nitrogen, organic phosphorus and inorganic phosphorus on inorganic carbon can be divided into two groups, and that every factor
has different influence on different form or on the same form in different environment. Different IC form may transform into
each other in the early diagenetic process of sediment, but NaCl form, NH3 H2O form, NaOH form and NH2OH HCl form may convert to HCl form ultimately. So every IC form has different contribution to carbon cycling. This study
showed that the contribution of various form of IC to the carbon cycle is in the order of NaOH form>NH2OH HCl form>NH3 H2O form>NaCl form>HCl form, and that the contribution of HCl form contributes little to carbon cycling, HCl form may be one
of end-result of atmospheric CO2. So Yangtze River estuary sediment may absorb at least about 40.96×1011 g atmospheric CO2 every year, which indicated that offshore sediment play an important role in absorbing atmospheric CO2. 相似文献
992.
Short- and Long-term Tannin Induced Carbon, Nitrogen and Phosphorus Dynamics in Corsican Pine Litter 总被引:1,自引:1,他引:0
Klaas G. J. Nierop Jacobus M. Verstraten Albert Tietema Joke W. Westerveld Piet E. Wartenbergh 《Biogeochemistry》2006,79(3):275-296
Pine litter amended with either tannic acid (TA) or condensed tannins (CTs) was studied to assess the effects on C, N and
P mineralization in relation to the fate of tannins by incubation experiments during various time intervals. TA induced a
rapid short-term effect resulting in high C respiration and net N and P immobilisation. After one week of incubation, TA was
decomposed and net C, N and P mineralization and net nitrification resembled that of the control (non-amended litter). CTs
exhibited effects on net mineralization on longer terms, i.e. after several weeks of incubation until the end of the experiment
(84 days). While net N and P mineralization were greatly reduced, net nitrification was only slightly affected. Most likely
CTs formed complexes with organic N of the substrate thereby reducing net N mineralization, while such complexes were not
involved in net nitrification processes. The reduction of net P mineralization is due to the lack of need for P by microbes
when they cannot get access to N. The fact that decreasing amounts of extractable CTs were accompanied by increasing effects
on mineralization processes with incubation time strongly suggests that CTs were incorporated into the litter in such a way
that they were inextricable by the common solvents needed to measure tannins, such as for the Folin–Ciocalteu and HCl–butanol
assays. 相似文献
993.
E. S. Bernhardt J. J. Barber J. S. Pippen L. Taneva J. A. Andrews W. H. Schlesinger 《Biogeochemistry》2006,77(1):91-116
Emissions of CO2 from soils make up one of the largest fluxes in the global C cycle, thus small changes in soil respiration may have large
impacts on global C cycling. Anthropogenic additions of CO2 to the atmosphere are expected to alter soil carbon cycling, an important component of the global carbon budget. As part
of the Duke Forest Free-Air CO2 Enrichment (FACE) experiment, we examined how forest growth at elevated (+200 ppmv) atmospheric CO2 concentration affects soil CO2 dynamics over 7 years of continuous enrichment. Soil respiration, soil CO2 concentrations, and the isotopic signature of soil CO2 were measured monthly throughout the 7 years of treatment. Estimated annual rates of soil CO2 efflux have been significantly higher in the elevated plots in every year of the study, but over the last 5 years the magnitude
of the CO2 enrichment effect on soil CO2 efflux has declined. Gas well samples indicate that over 7 years fumigation has led to sustained increases in soil CO2 concentrations and depletion in the δ13C of soil CO2 at all but the shallowest soil depths. 相似文献
994.
Impacts of Biological Soil Crust Disturbance and Composition on C and N Loss from Water Erosion 总被引:4,自引:0,他引:4
Nichole N. Barger Jeffrey E. Herrick Justin Van Zee Jayne Belnap 《Biogeochemistry》2006,77(2):247-263
In this study, we conducted rainfall simulation experiments in a cool desert ecosystem to examine the role of biological soil
crust disturbance and composition on dissolved and sediment C and N losses. We compared runoff and sediment C and N losses
from intact late-successional dark cyanolichen crusts (intact) to both trampled dark crusts (trampled) and dark crusts where
the top 1 cm of the soil surface was removed (scraped). In a second experiment, we compared C and N losses in runoff and sediments
in early-successional light cyanobacterial crusts (light) to that of intact late-successional dark cyanolichen crusts (dark).
A relatively high rainfall intensity of approximately 38 mm per 10-min period was used to ensure that at least some runoff
was generated from all plots. Losses of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and ammonium (NH4+ ) were significantly higher from trampled plots as compared to scraped and intact plots. Sediment C and N losses, which made
up more than 98% of total nutrient losses in all treatments, were more than 4-fold higher from trampled plots relative to
intact plots (sediment C g/m2, intact = 0.74, trampled = 3.47; sediment N g/m2, intact = 0.06, trampled = 0.28). In light crusts, DOC loss was higher relative to dark crusts, but no differences were observed
in dissolved N. Higher sediment loss in light crusts relative to dark crusts resulted in 5-fold higher loss of sediment-bound
C and N. Total C flux (sediment + dissolved) was on the order of 0.9 and 7.9 g/m2 for dark and light crusts, respectively. Sediment N concentration in the first minutes after runoff from light crusts was
3-fold higher than the percent N of the top 1 cm of soil, suggesting that even short-term runoff events may have a high potential
for N loss due to the movement of sediments highly enriched in N. Total N loss from dark crusts was an order of magnitude
lower than light crusts (dark = 0.06 g N/m2, light = 0.63 g/m2). Overall, our results from the small plot scale (0.5 m2) suggest that C and N losses are much lower from intact late-successional cyanolichen crusts as compared to recently disturbed
or early-successional light cyanobacterial crusts. 相似文献
995.
Soil organic carbon (SOC) models have been widely used to predict SOC change with changing environmental and management conditions,
but the accuracy of the prediction is often open to question. Objectives were (i) to quantify the amounts of C derived from
maize in soil particle size fractions and at various depths in a long-term field experiment using 13C/12C analysis, (ii) to model changes in the organic C, and (iii) to compare measured and modelled pools of C. Maize was cultivated
for 24 years on a silty Luvisol which resulted in a stock of 1.9 kg maize-derived C m−2 (36% of the total organic C) in the Ap horizon. The storage of maize-derived C in particle size fractions of the Ap horizon
decreased in the order clay (0.65 kg C m−2) > fine and medium silt (0.43) > coarse silt (0.33) > fine sand (0.13) > medium sand (0.12) > coarse sand (0.06) and the
turnover times of C3-derived C ranged from 26 (fine sand) to 77 years (clay). The turnover times increased with increasing soil depth. We used
the Rothamsted Carbon Model to model the C dynamics and tested two model approaches: model A did not have any adjustable parameters,
but included the Falloon equation for the estimation of the amount of inert organic matter (IOM) and independent estimations
of C inputs into the soil. The model predicted well the changes in C3-derived C with time but overestimated the changes in maize-derived C 1.6-fold. In model B, the amounts of IOM and C inputs
were optimized to match the measured C3- and C4-derived SOC stocks after 24 years of continuous maize. This model described the experimental data well, but the modelled
annual maize C inputs (0.41 kg C m−2 a−1) were less than the independently estimated total input of maize litter C (0.63 kg C m−2 a−1) and even less than the annual straw C incorporated into the soil (0.46 kg C m−2 a−1). These results indicated that the prediction of the Rothamsted Carbon Model with independent parameterization served only
as an approximation for this site. The total amount of organic C associated with the fraction 0–63 μm agreed well with the sum of the pools ‘microbial biomass’, ‘humified-organic matter’ and IOM of the model B. However, the
amount of maize-derived C in this fraction (3.4 g kg−1) agreed only satisfactorily with the sum of maize-derived C in the pools ‘microbial biomass’ and ‘humified organic matter’
(2.6 g kg−1). 相似文献
996.
准确了解陆地生态系统中碳密度的时空格局及其影响因子和作用机制,对于估算和预测不同类型生态系统中的植被和土壤的碳存储能力、判定碳汇、制定缓解全球变化的合理政策措施,具有重要意义。该文综述了现有研究中发现的世界陆地生态系统碳密度空间分布的地带性规律及中国陆地生态系统碳密度格局的独特特点。在全球尺度上,植被碳密度分布与植物生物量格局基本一致,除北方森林外其余大部分随纬度升高而减小;土壤碳密度则随纬度升高而增大。陆地生态系统中北方森林和热带森林的总体碳密度最高,不同的是,前者的碳主要集中在土壤中,而后者则集中在植被中。但在区域尺度上,由于气候、地形及人类活动影响,这种规律性可能会发生变化甚至不起作用。水热条件、土壤养分、生物多样性、气候和大气CO2浓度的变化以及土地利用与覆盖变化等是碳密度空间格局形成和发生变化的驱动因子。在某一特定区域,它们通过直接或间接提高植被净初级生产力,抑制呼吸和分解作用来增加陆地生态系统碳密度。综合分析特定时空条件下各因子对碳存储量的影响是解释碳密度分布现状,预测碳密度格局变化的关键,但目前的研究对各项驱动因子的作用机制、影响强度及多个因子间的相互作用仍不是很清楚,需要加强该方面的研究力度。碳密度研究中的数据获取、机理分析和过程模拟等方面仍存在很大的不确定性,因此有必要建立规范统一的碳密度测量估算系统和更为精准有效的估算模型,进行多尺度、多精度水平的综合研究。 相似文献
997.
Jia-ying Xin Jun-ru Cui Jian-zhong Niu Shao-feng Hua Chun-gu Xia Shu-ben Li Li-min Zhu 《Biocatalysis and Biotransformation》2004,22(3):225-229
Methanotrophs can oxidize methane to carbon dioxide through sequential reactions catalyzed by a series of enzymes including methane monooxygenase, methanol dehydrogenase, formaldehyde dehydrogenase, and formate dehydrogenase. When suspensions of methanotrophic bacteria of Methylosinus trichosporium IMV 3011 were incubated at 32°C with methane and oxygen, there was an extracellular accumulation of methanol from methane oxidation in response to carbon dioxide addition. Maximal accumulation of methanol was achieved with 40% carbon dioxide in the mixed reaction gases. A continuous experiment was performed in a continuous ultrafiltration reactor. The optimum gas mixture containing 20% (v v-1) methane, 20% oxygen, 20% nitrogen and 40% carbon dioxide was used to provide substrates and to maintain the transmembrane pressure. The product (methanol) was removed in the eluate buffer. The initial methanol concentration in the eluate buffer was 8.22 μmol L-1. The bioreactor was operated continuously for 198 h without obvious loss of productivity. 相似文献
998.
In this work, the excellent catalytic activity of highly ordered mesoporous carbons (OMCs) to the electrooxidation of nicotinamide adenine dinucleotide (NADH) and hydrogen peroxide (H(2)O(2)) was described for the construction of electrochemical alcohol dehydrogenase (ADH) and glucose oxidase (GOD)-based biosensors. The high density of edge-plane-like defective sites and high specific surface area of OMCs could be responsible for the electrocatalytic behavior at OMCs modified glassy carbon electrode (OMCs/GE), which induced a substantial decrease in the overpotential of NADH and H(2)O(2) oxidation reaction compared to carbon nanotubes modified glassy carbon electrode (CNTs/GE). Such ability of OMCs permits effective low-potential amperometric biosensing of ethanol and glucose, respectively, at Nafion/ADH-OMCs/GE and Nafion/GOD-OMCs/GE. Especially, as an amperometric glucose biosensor, Nafion/GOD-OMCs/GE showed large determination range (500-15,000mumoll(-1)), high sensitivity (0.053nAmumol(-1)), fast (9+/-1s) and stable response (amperometric response retained 90% of the initial activity after 10h stirring of 2mmoll(-1) glucose solution) to glucose as well as the effective discrimination to the possible interferences, which may make it to readily satisfy the need for the routine clinical diagnosis of diabetes. By comparing the electrochemical performance of OMCs with that of CNTs as electrode material for the construction of ADH- and GOD-biosensors in this work, we reveal that OMCs could be a favorable and promising carbon electrode material for constructing other electrochemical dehydrogenase- and oxidase-based biosensors, which may have wide potential applications in biocatalysis, bioelectronics and biofuel cells. 相似文献
999.
Mauro de Paula Moreira Celso S. Yamakawa Victor Haber Perez Ranulfo Monte Alegre 《World journal of microbiology & biotechnology》2008,24(9):1937-1942
The effect of carbon source addition on the operation of a sequencing batch reactor in order to remove nitrogen and COD of
poultry wastewater was studied. The reactor was constructed with a glass tube having a volume of 7 l and a jacket for temperature
control. The reactor bottom consisted of a conical porous stone in order to promote liquor aeration and agitation. Initial
conditions and operation strategies were adjusted to improve the final effluent quality. According to the attained experimental
results, it was verified that nitrification and denitrification can occur simultaneously in aerated culture, contrary the
observation of some authors. 相似文献
1000.
G. S. Prasad S. Girisham S. M. Reddy K. Srisailam 《World journal of microbiology & biotechnology》2008,24(10):2055-2059
A filamentous fungus Cunninghamella blakesleeana was screened for its ability to biotransform the anthelmintic drug albendazole. The fungus produced three metabolites in
the presence of the carbon and nitrogen sources studied. The transformation was identified by HPLC and the structures of the
transformation products were assigned by LC-MS-MS analysis and on the basis of previous reports. The results indicated that
the fungus metabolized albendazole into albendazole sulfoxide (M1), albendazole sulfone (M2) and an N-methyl metabolite of albendazole sulfoxide (M3). The effect of carbon and nitrogen source on the biotransformation of albendazole
was significant. Among the carbon and nitrogen sources studied, fructose and urea respectively produced maximum extent of
biotransformation in terms of substrate depletion. Among the carbon sources studied, maltose produced a higher percentage
of M1 whereas M2 and M3 were produced to their maximum extent in presence of d-fructose in terms of metabolite per unit quantity of biomass. In the case of nitrogen sources, ammonium acetate, calcium
nitrate and barium nitrate produced maximum percentage of M1, M2 and M3 respectively. The results reveal that the carbon and
nitrogen source significantly influence the microbial transformation both qualitatively and quantitatively. 相似文献