共查询到10条相似文献，搜索用时 125 毫秒
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Andrea Lübben Olaf Dellwig Sandra Koch Melanie Beck Thomas H. Badewien Sibylle Fischer Rainer Reuter 《Ocean Dynamics》2009,59(2):263-275
The spatial and temporal distributions of chromophoric dissolved organic matter (CDOM) and dissolved organic carbon (DOC)
was studied in the East-Frisian Wadden Sea (Southern North Sea) during several cruises between 2002 and 2005. The spatial
distribution of CDOM in the German Bight shows a strong gradient towards the coast. Tidal and seasonal variations of dissolved
organic matter (DOM) identify freshwater discharge via flood-gates at the coastline and pore water efflux from tidal flat
sediments as the most important CDOM sources within the backbarrier area of the Island of Spiekeroog. However, the amount
and pattern of CDOM and DOC is strongly affected by various parameters, e.g. changes in the amount of terrestrial run-off,
precipitation, evaporation, biological activity and photooxidation. A decoupling of CDOM and DOC, especially during periods
of pronounced biological activity (algae blooms and microbial activity), is observed in spring and especially in summer. Mixing
of the endmembers freshwater, pore water, and open sea water results in the formation of a coastal transition zone. Whilst
an almost conservative behaviour during mixing is observed in winter, summer data point towards non-conservative mixing. 相似文献
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Characterizing the properties of dissolved organic matter isolated by XAD and C-18 solid phase extraction and ultrafiltration 总被引：1，自引：0，他引：1
Sara B. Schwede-Thomas Yu-Ping Chin Karl J. Dria Patrick Hatcher Edith Kaiser Barbara Sulzberger 《Aquatic Sciences - Research Across Boundaries》2005,67(1):61-71
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Brittany R. Kruger Brent J. Dalzell Elizabeth C. Minor 《Aquatic Sciences - Research Across Boundaries》2011,73(3):405-417
In this study, samples were taken from three contrasting freshwater sources and amended with salt in order to determine the
influence of salinity and dissolved organic matter (DOM) composition on DOM recovery via ultrafiltration and solid phase extraction
(SPE) with C18 disks. Salt addition caused variable recovery of DOM when using C18 SPE, and ultraviolet–visible spectroscopic characterization of the extracted material showed spectral responses that varied
among sample sources. In contrast, increasing sample salinity from 0 to 30 ppt consistently caused a 15–25% reduction in the
amount of high molecular weight DOM isolated by ultrafiltration for both dissolved organic carbon (DOC) and chromophoric DOM
(CDOM), regardless of DOM composition. We hypothesize that a change in conformation (such as coiling or disaggregation) of
DOM molecules occurs in the presence of salt, allowing them to pass through the ultrafiltration membrane and thereby decreasing
the DOM retained by ultrafiltration. These results are important because they demonstrate that changes in salinity can influence
DOM recovery in estuaries. Interpretation of DOM characteristics along estuarine gradients needs to account for potential
artifacts introduced by sample isolation techniques. 相似文献
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Brandon M. Stephens Elizabeth C. Minor 《Aquatic Sciences - Research Across Boundaries》2010,72(4):403-417
The chemical characteristics of bulk (sterile-filtered) and high molecular-weight dissolved organic matter (HMW DOM) were
analyzed for freshwater (St. Louis River, Minnesota to Lake Superior) and saline (Elizabeth River, Virginia to Chesapeake
Bay) river-to-receiving basin transects. Dissolved organic carbon concentrations and UV–Visible spectroscopy of bulk DOM demonstrated
a reduction in organic carbon, colored DOM and aromatic compounds downstream in both transects. The proportion of DOM recoverable
via ultrafiltration as HMW material also decreased downstream in both transects, although there was an offset in recoveries
between the transects that may be explained by the effects of ionic strength and/or differences in ultrafiltration technique.
The analysis of HMW DOM by Fourier transform infrared spectroscopy illustrated similar trends between transects, with a general
shift from aromatic/carboxylic compounds nearshore to aliphatic/carbohydrate materials offshore. The parallel changes observed
along saline and freshwater transects imply that similar processes play significant roles in the down-gradient alteration
of DOM and that ionic strength or pH changes cause second-order effects. 相似文献