北方泥炭沼泽中酚类物质释放的热敏感性研究:以英国威尔士地区雨养和矿养泥炭沼泽为例     

向武  Chris Freeman 《地球化学》2008,37(2):157-164

利用高精度多梯度热培养系统,对英国威尔士地区两类典型的北方泥炭沼泽中酚类物质和溶解有机碳释放的热敏感性进行了为期1年的调查研究.研究结果表明,雨养泥炭沼泽(Bog)酚类物质释放的热敏感性Q10(总酚)月变化为0.92～1.57,而矿养泥炭沼泽(Fen)的月变化范围为0.93～1.30.酚类释放的热敏感性与土壤温度大致呈正相关关系.此外,土壤温度与溶解有机碳释放的热敏感性Q10(DOC)也呈正相关关系.总体上,雨养泥炭沼泽的热敏感性比矿养泥炭沼泽略高.除温度外,水文条件和植被等多种环境因子对酚类物质和溶解有机碳释放的热敏感性也有较大影响.研究结果还表明酚碳热敏感性比值Q10o(总酚)/Q10(DOC)相对稳定,土壤温度的变化对其影响有限.  相似文献   

Seasonal Variations in Benthic Community Metabolism and Nitrogen Dynamics in a Shallow, Organic-Poor Danish Lagoon     

Erik Kristensen 《Estuarine, Coastal and Shelf Science》1993,36(6)

The dynamics of benthic primary production and community respiration in a shallow oligotrophic, marine lagoon (Fællestrand, Denmark) was followed for 1·5 years. The shape of the annual primary production cycle was explained primarily by seasonal changes in temperature (r² = 0·67-0·72) and daylength (r² = 0·63), whereas temperature almost explained all variation in benthic community respiration (r² = 0·83-0·87). On a daily basis the benthic system was autotrophic during spring and summer supplied by 'new' and 'regenerated' nitrogen and predominantly heterotrophic during fall and winter caused by light and nutrient limitation. The linear depth-relationship between porewater alkalinity and ammonium indicated that the C:N ratio of mineralized organic matter is low in spring and summer (3-6) and high in fall and winter (9-16). This is inversely related to net primary production and thus the input of labile, nitrogen-rich algal cells. Accordingly, mineralization occurred predominantly in the upper 2-5 cm of the sediment. The pool of reactive material (microalgal cells) was estimated to account for 12% of total organic carbon in the upper 3 cm, and had an average turnover time of less than 1 month in summer. Assimilation of organic carbon by benthic animals was equivalent to about 30% of the annual gross primary production. Grazing reduced chlorophyll a concentration in the sediment during summer and spring to values 30-40% lower than in winter, but maintained a 3-4 times higher specific microalgal productivity. The rapid turnover of organic carbon and nitrogen, and important role of benthic microalgae showed that the benthic community in this oligotrophic lagoon is of a very dynamic nature.  相似文献   

Spatial and seasonal variations in depth profile of trace metals in saltmarsh sediments from Sapelo Island, Georgia, USA   总被引：1，自引：0，他引：1  

Alakendra N. Roychoudhury   《Estuarine, Coastal and Shelf Science》2007,72(4):675-689

This study was undertaken to elucidate the impact of early diagenetic processes on the accumulation of trace metals in Sapelo Island saltmarsh sediments as a function of time, space and sediment properties. Samples were collected from three sites in summer (May 1997) and winter (January 1998) along a transect from an unvegetated Creek Bank through a vegetated Tidal Levee to the vegetated midmarsh with evident lateral heterogeneity caused by hydrologic regime, macrophytes and microbial and macrofaunal activities. A suite of trace metals (As, Ba, Cr, Co, Cu, Cd, Mo, Ni, Pb, Th, Ti, U, V, Zn and Zr) was analyzed to obtain their depth-distribution at the three sites. Spatially marked differences were observed, that were primarily related to hydraulic flushing of trace metals away from the sites in high-energy regimes, rapid downward mixing and reworking of sediment via bioturbation, and below-ground degradation and production of Spartina biomass. Although sulfate reduction and the formation of acid volatile sulfide and pyrite were dominant processes throughout the marsh, the trace metal scavenging role of sulfides was not apparent. However, possible sulfurization of organic matter, leading to enhanced trapping of trace metals with organic carbon, may have played an important role in sequestration of trace metals.No similarity was observed visually between the depth trends of trace metals and sediment properties (grain size, iron-oxyhydroxide content, acid volatile sulfides and pyrite content) that are known to play a major role in trace metal partitioning. Only organic carbon content closely followed the trace metal profiles at all the three sites. Minor variation in depth-integrated sediment trace metal content was observed seasonally at each of the three sites. Furthermore, the depth trend of profiles of individual trace metals also did not vary significantly over the seasons either.  相似文献   

Seasonal DOC accumulation in the Black Sea: a regional explanation for a general mechanism   总被引：2，自引：0，他引：2  

Gustave Cauwet  Gaëlle Dliat  Anton Krastev  Galina Shtereva  Sylvie Becquevort  Christiane Lancelot  Andr Momzikoff  Alain Saliot  Adriana Cociasu  Lucia Popa 《Marine Chemistry》2002,79(3-4)

During three cruises in the Black Sea, organised in July 1995 and April–May 1997, biological and chemical parameters that can influence the carbon budget were measured in the water column on the NW shelf, particularly in the mixing zone with Danube River waters. We observed in early spring (end of April–May) conditions an important input of freshwater organisms that enhanced the microbial activity in the low salinity range. High bacterial activity regenerates nitrogen in the form of nitrates, but is also responsible for an important consumption of ammonium and phosphate, leading to a high N/P ratio and a strong deficit in phosphorus. The consequence is a limitation of phytoplankton development but also a production of carbohydrates that accumulate all along the salinity gradient. These mechanisms are responsible for a seasonal accumulation of dissolved organic carbon (DOC) that increases from 210 μM in winter to about 280 μM in summer. All this excess DOC disappears during winter, probably degraded by bacterial activity. The degradation of carbon-rich organic matter increases the phosphorus demand by bacteria bringing limitation to phytoplankton primary production.  相似文献   

Algal blooms in high turbidity, a result of the conflicting consequences of turbulence on nutrient cycling in a shallow water estuary     

R. Fichez  T.D. Jickells  H.M. Edmunds 《Estuarine, Coastal and Shelf Science》1992,35(6)

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Evidence for the grazing hypothesis: Grazing reduces phytoplankton responses of the HNLC ecosystem to iron enrichment in the western subarctic pacific (SEEDS II)     

《Journal of Oceanography》2007,63(6):983-994

A mesoscale iron-enrichment study (SEEDS II) was carried out in the western subarctic Pacific in the summer of 2004. The iron patch was traced for 26 days, which included observations of the development and the decline of the bloom by mapping with sulfur hexafluoride. The experiment was conducted at almost the same location and the same season as SEEDS (previous iron-enrichment experiment). However, the results were very different between SEEDS and SEEDS II. A high accumulation of phytoplankton biomass (∼18 mg chl m⁻³) was characteristic of SEEDS. In contrast, in SEEDS II, the surface chlorophyll-a accumulation was lower, 0.8 to 2.48 mg m⁻³, with no prominent diatom bloom. Photosynthetic competence in terms of F _v/F _m for the total phytoplankton community in the surface waters increased after the iron enrichments and returned to the ambient level by day 20. These results suggest that the photosynthetic physiology of the phytoplankton assemblage was improved by the iron enrichments and returned to an iron-stressed condition during the declining phase of the bloom. Pico-phytoplankton (<2 μm) became dominant in the chlorophyll-a size distribution after the bloom. We observed a nitrate drawdown of 3.8 μM in the patch (day 21), but there was no difference in silicic acid concentration between inside and outside the patch. Mesozooplankton (copepod) biomass was three to five times higher during the bloom-development phase in SEEDS II than in SEEDS. The copepod biomass increased exponentially. The grazing rate estimation indicates that the copepod grazing prevented the formation of an extensive diatom bloom, which was observed in SEEDS, and led to the change to a pico-phytoplankton dominated community towards the end of the experiment.  相似文献   

一种腐屑食性鱼类对生态系统氮循环的影响     

线薇薇  孙松  刘瑞玉 《中国海洋大学学报(自然科学版)》2004,34(4):549-554

研究表明 :腐屑食性鱼类——梭鱼对环境中有机氮的摄入能力随体重的增加而增加 ,随温度的升高 ,体重系数显著减少。摄入氮 (CN,mg/ d)与体重 (W,g)和温度 (T,℃ )的数值关系可用如下模型表示 :CN=0 .6 370 W1 .0 642 ln(3.70 0 8T)。体重为 1 0 0 g的梭鱼每日可消耗环境中 332 mg氮有机质。梭鱼氮的吸收效率主要受温度的影响 ,而氮的转化效率与体重呈显著的正相关关系。随体重的增加 ,排泄氮所占比例降低  相似文献   

The “Zero-order Model” revisited: Paul Schindler's influence on the development of trace metal scavenging models     

Santschi  Peter H.  Honeyman  Bruce D.  Quigley  Matthew S. 《Aquatic Sciences - Research Across Boundaries》1993,55(4):230-239

In 1975 Paul Schindler produced the first oceanic trace metal scavenging model to explicitly include the role of surface chemistry as a control on trace metal water column residence times. The eighteen years that have elapsed since the publication of Schindler's seminal paper have seen the development of a variety of oceanic scavenging models; yet, the fundamental insight of his Zero-order Model remains the benchmark. This paper describes the role of Paul Schindler's work on surface chemistry in providing a framework for the current generation of trace element scavenging models.  相似文献   

Kinetics of redox cycling of iron coupled with fulvic acid     

Yiwei Deng  Werner Stumm 《Aquatic Sciences - Research Across Boundaries》1993,55(2):103-111

The kinetics of conversion of iron(III) (hydr)oxides to ferrous iron mediated by fulvic acid have been investigated in order to improve the understanding of the redox cycling of iron at the oxic-anoxic boundary in natural waters. Under the conditions similar to natural waters, fulvic acid is able to reduce the iron(III) (hydr)oxide. The kinetics of the reaction depend on the reactivity of iron(III) (hydr)oxides and the reducing power of the fulvic acid. The rate of reaction is 60 nm/h obtained under following conditions: total concentration of Fe(III) 1.0 × 10^–4 M, pH 7.5, fulvic acid 5 mg/L. The rate is considered as a net result of reduction and oxidation in the > Fe^III-OH/Fe(II) wheel coupled with fulvic acid. In a real natural water system, reductants other than fulvic acid may be of importance. The results obtained in the laboratory, however, provide evidence that the Fe(OH)₃(s)/Fe(II) redox couple is able to act as an electron-transfer mediator for the oxidation of natural organic substances, such as fulvic acid by molecular oxygen either in the absence of microorganisms or as a supplement to microbial activity.  相似文献   

The role of sediments in the phosphorus cycle in Lake Lugano. I. Geochemical approach     

D. Span  J. Dominik  M. A. Lazzaretti  J. -P. Vernet 《Aquatic Sciences - Research Across Boundaries》1992,54(3-4):277-284

The bottom sediment from three coring stations in Lake Lugano (Lago di Lugano) show major differences in their role in the P-cycles related to their geochemistry and characteristics of sedimentation. In the northern basin, the deepest sediment may be considered practically inactive, due to a permanently reduced condition at the sediment-water interface. In the southern basin, the sediments are active with respect to P-recycling with strong seasonal variations. One of the sites (Figino) behaves as a sink for P due to a high iron content and an important rate of detrital sedimentation.  相似文献