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1.
Based on simultaneous use of organic and geochemical indicators (δ13C, C/N, and n-alkanes), the genesis of organic matter (OM) in recent bottom sediments of the Kara Sea was characterized. Maps for percentages and absolute masses of marine and terrigenous OM were drawn. The masses of buried marine and terrigenous OM were compared to its supply to the sea and onto the sea bottom.  相似文献   

2.
Data are presented on the content of aliphatic and polycyclic aromatic hydrocarbons (AHC and PAH, respectively) in the interstitial waters and bottom sediments of the Kara Sea compared to the distribution of the particulate matter and organic carbon. It was found that the AHC concentrations within the water mass (16 μg/l on average) are mainly formed by natural processes. The AHC distribution represents the variability of the hydrological and sedimentation processes in different regions of the sea. The widest ranges of the concentrations were registered in the Ob Bay-Kara Sea section: in the water (10–310 μg/l for the AHC and 0.4–7.2 ng/l for the PAH) and in the surface layer of the bottom sediments (8–42 μg/l for the AHC and 9–94 ng/g for the PAH). The differentiation of the hydrocarbons (HC) in the different media follows the marginal filter’s regularities; therefore, no oil and pyrogenic compounds are supplied to the open parts of the sea. In the sediment mass, the HC content is determined by the variations in the oxidative conditions in the sediment and its material’s composition.  相似文献   

3.
The organic matter (OM) pool has been studied in two sub-arctic north Norwegian fjords, Balsfjord and Ullsfjord, in July 2001 and June 2003. Besides general OM parameters such as dissolved organic carbon (DOC), particulate organic carbon and nitrogen (POC and PON), the distribution of specific compounds such as folic acid and surface active substances (SAS) was followed. The results are supported with data of salinity, temperature, and chlorophyll a (Chl a). This approach allowed assessment of the fate of the OM pool, and its distinct vertical, spatial, and seasonal variations. Fjord waters could be vertically divided into two layers: the upper mixed layer (UML), until 40 m depth, and the deep aphotic layer. Spatial variability between the two fjords is a consequence of different influences of shelf waters on the fjords. Significant enrichment of POC and PON concentrations (3–5 times), as well as those of particulate SAS and folic acid (up to 3.2 times) in the UML was recorded during the period of new production, in early June. Depletion of particulate OM in deep waters was ascribed to fast dissolution or remineralization in the UML or upper part of aphotic layer. OM in July 2001 was characterized with 15.9% higher DOC pool compared to June 2003, and had refractory properties, suggesting the fjords to be an important source of organic matter for the continental shelf ecosystem. The DOC pool in these subarctic fjords represents the major component of the OM pool. The DOC concentrations in fjords are lower than those in previously studied warmer seas (e.g. the Adriatic Sea), whereas the concentrations of folic acid and SAS are comparable to those in the Adriatic Sea.  相似文献   

4.
Research has been conducted in Nha Trang Bay (Southern Vietnam, the South China Sea) at the section from the estuary of the Cai River to the marine part of the bay, as well as in the area of coral reefs. The objects of the studies are the river and sea waters, the suspended matter, and the bottom sediments. Data on the dissolved organic carbon and the total nitrogen in the water are obtained. The organic carbon content is estimated in the suspended matter; the organic carbon and the molecular and group composition of the n-alkanes are determined in the bottom sediments. The molecular and group composition of the n-alkanes in the bottom sediments of the landfill have made it possible to identify three types of organic matter (OM): marine, mixed, and of mainly terrigenous origin. All the types of OM are closely related to the specificity of the sedimentation and the hydrodynamics of the waters in this water area.  相似文献   

5.
渤海春季浮游细菌分布与生态环境因子的关系   总被引：11，自引：2，他引：11  
研究了 1 999年 4～ 5月渤海水体浮游细菌分布与生态环境因子的关系。结果显示 ,渤海春季表层水体浮游细菌含量与水温和溶解性有机碳呈正相关 ,相关系数分别为 0 .6 0 1 (P<0 .0 1 )和0 .4 0 6 (P<0 .0 5 ) ,并与溶解氧含量呈负相关 ,相关系数为 0 .5 1 9(P<0 .0 1 ) ;底层水体浮游细菌含量与水温、溶解性有机碳 (dissolved organic carbon,DOC)、颗粒性有机碳 (particulate organic carbon,POC)和叶绿素 a含量呈正相关 ,相关系数分别为 0 .82 0 (P<0 .0 1 ) ,0 .6 6 1 (P<0 .0 1 ) ,0 .5 31 (P<0 .0 1 )和 0 .4 42 (P<0 .0 5 ) ,并与溶解氧含量呈负相关 ,相关系数为 0 .6 5 0 (P<0 .0 1 )。表明水温和DOC、POC含量是渤海水域浮游细菌含量的主要限制因子 ,而水体中的溶解氧 (dissolved oxygen,DO)含量与浮游细菌的含量有关  相似文献   

6.
Detailed organic geochemical analyses were performed on surface water particulate samples of the lower Kalix River and northern Bothnian Bay collected during the spring flood of 2005. Both bulk geochemical and molecular biomarker analyses indicated a predominance of terrestrially-derived particulate organic matter (POM), both of higher plant and Sphagnum origin in the low salinity zone (LSZ) of the Kalix River estuary, with an increasing contribution of marine-derived POM in the offshore Bothnian Bay basin.Two-dimensional box modeling of the mixed surface layer in the LSZ indicated that 65% of the particulate organic carbon (POC) and between 73 and 93% of the terrestrial biomarker classes analyzed (high molecular weight n-alkanes, n-alkanoic acids and n-alkanols as well as sitosterol) were degraded in the course of their weeklong transit through the inner LSZ during the spring flood. This corresponds to field-based degradation rate constants for the biomarkers of 0.5 and 2.5 day− 1, which are similar to results reported from mesocosm experiments for related compounds. The degradation rate constant for terrestrial POC of 0.38 day− 1 was about 20 times larger than for DOC and suggests that POC mineralization stands for 44% of the total mineralization, which is much larger than previously considered.This sub-arctic river-export regime has a geochemistry resembling that of neighboring western Russian Arctic Rivers, suggesting that a large part of the OM coastally exported from northernmost Eurasian soils may be degraded within the vicinity of the river mouths and putatively be released as carbon dioxide. The 65% degradation of terrestrial POC in the coastal surface water of this sub-arctic recipient is substantially larger than a global-average of 35% used in recent budget estimates of the fate of terrestrially-exported POC on the pan-arctic shelves. Considering ongoing and predicted changes in the Arctic Region due to global warming a more efficient degradation of river-exported terrestrial POC may have far-reaching consequences for the large-scale biogeochemical cycling of carbon in the pan-arctic region and beyond.  相似文献   

7.
The sources and distribution of organic matter (OM) in surface waters and sediments from Winyah Bay (South Carolina, USA) were investigated using a variety of analytical techniques, including elemental, stable isotope and organic biomarker analyses. Several locations along the estuary salinity gradient were sampled during four different periods of contrasting river discharge and tidal range. The dissolved organic carbon (DOC) concentrations of surface waters ranged from 7 mg l−1 in the lower bay stations closest to the ocean to 20 mg l−1 in the river and upper bay samples. There was a general linear relationship between DOC concentrations and salinity in three of the four sampling periods. In contrast, particulate organic carbon (POC) concentrations were significantly lower (0.1–3 mg l−1) and showed no relationship with salinity. The high molecular weight dissolved OM (HMW DOM) isolated from selected water samples collected along the bay displayed atomic carbon:nitrogen ratios ([C/N]a) and stable carbon isotopic compositions of organic carbon (δ13COC) that ranged from 10 to 30 and from −28 to −25‰, respectively. Combined, such compositions indicate that in most HMW DOM samples, the majority of the OM originates from terrigenous sources, with smaller contributions from riverine and estuarine phytoplankton. In contrast, the [C/N]a ratios of particulate OM (POM) samples varied significantly among the collection periods, ranging from low values of 5 to high values of >20. Overall, the trends in [C/N]a ratios indicated that algal sources of POM were most important during the early and late summer, whereas terrigenous sources dominated in the winter and early spring.In Winyah Bay bottom sediments, the concentrations of the mineral-associated OM were positively correlated with sediment surface area. The [C/N]a ratios and δ13COC compositions of the bulk sedimentary OM ranged from 5 to 45 and from −28 to −23‰, respectively. These compositions were consistent with predominant contributions of terrigenous sources and lesser (but significant) inputs of freshwater, estuarine and marine phytoplankton. The highest terrigenous contents were found in sediments from the river and upper bay sites, with smaller contributions to the lower parts of the estuary. The yields of lignin-derived CuO oxidation products from Winyah Bay sediments indicated that the terrigenous OM in these samples was composed of variable mixtures of relatively fresh vascular plant detritus and moderately altered soil OM. Based on the lignin phenol compositions, most of this material appeared to be derived from angiosperm and gymnosperm vascular plant sources similar to those found in the upland coastal forests in this region. A few samples displayed lignin compositions that suggested a more significant contribution from marsh C3 grasses. However, there was no evidence of inputs of Spartina alterniflora (a C4 grass) remains from the salt marshes that surround the lower sections of Winyah Bay.  相似文献   

8.
Dissolved and particulate organic matter was measured during six cruises to the southern Ross Sea. The cruises were conducted during late austral winter to autumn from 1994 to 1997 and included coverage of various stages of the seasonal phytoplankton bloom. The data from the various years are compiled into a representative seasonal cycle in order to assess general patterns of dissolved organic matter (DOM) and particulate organic matter (POM) dynamics in the southern Ross Sea. Dissolved organic carbon (DOC) and particulate organic carbon (POC) were at background concentrations of approximately 42 and 3 μM C, respectively, during the late winter conditions in October. As the spring phytoplankton bloom progressed, organic matter increased, and by January DOC and POC reached as high as 30 and 107 μM C, respectively, in excess of initial wintertime conditions. Stocks and concentrations of DOC and POC returned to near background values by autumn (April). Approximately 90% of the accumulated organic matter was partitioned into POM, with modest net accumulation of DOM stocks despite large net organic matter production and the dominance of Phaeocystis antarctica. Changes in NO3 concentration from wintertime values were used to calculate the equivalent biological drawdown of dissolved inorganic carbon (DICequiv). The fraction of DICequiv drawdown resulting in net DOC production was relatively constant (ca. 11%), despite large temporal and spatial variability in DICequiv drawdown. The C : N (molar ratio) of the seasonally produced DOM had a geometric mean of 6.2 and was nitrogen-rich compared to background DOM. The DOM stocks that accumulate in excess of deep refractory background stocks are often referred to as “semi-labile” DOM. The “semi-labile” pool in the Ross Sea turns over on timescales of about 6 months. As a result of the modest net DOM production and its lability, the role DOM plays in export to the deep sea is small in this region.  相似文献   

9.
Meteorological and oceanographic conditions in the Northern Adriatic Sea in a year notable for massive mucilage formation (2004) were compared with those in years where this phenomenon did not occur (2003, 2005 and 2006) to suggest possible links. The months preceding the mucilage event in 2004 were considered the ‘incubation period’ and were characterized by a strong freshet in May which increased the water column stability. Winter cooling and scarcity of freshwater inputs from the Po River triggered the dense water formation and intrusion in the northern basin. Weak southeasterly winds and an increase in surface seawater temperatures contributed to maintain and reinforce the water column stability, and at the same time an intense diatom spring bloom created the conditions for accumulation of organic matter. The interplay of climatological forcings and biological processes caused temporal variations of dissolved organic carbon (DOC) and particulate organic carbon (POC) in the basin, with POC playing an important role in the aggregation process, as suggested by its increase relative to DOC before massive mucilage formation. We therefore suggest that high POC/total particulate nitrogen ratios in the suspended particulate organic fraction, a steep increase of POC/Chlorphyll a, and the decreased DOC/POC ratios represent ‘early warning’ signals of the main processes that lead to mucilage events in the Northern Adriatic Sea.  相似文献   

10.
Particulate organic carbon (POC) in surface sediments of the Baltic Sea   总被引：2，自引：2，他引：0  
In this study, particulate organic carbon (POC) contents and their distribution pattern in surficial sediments of the Baltic Sea are presented for 1,471 sampling stations. POC contents range from approx. 0.1% in shallow sandy areas up to 16% in deep muddy basins (e.g. Gotland Basin). Some novel relationships were identified between sediment mass physical properties (dry bulk density (DBD), grain size) and POC levels. Notably, the highest POC concentrations (about 10–17 mg cm–3) occur in sandy mud to mud (60–100% mud content) with intermediate POC contents of about 3–7% and DBDs of 0.1–0.4 g cm–3. Areas with this range in values seem to represent the optimum conditions for POC accumulation in the Baltic Sea. The maximum POC contents (8–16%) are found in fluid mud of the central Baltic Sea characterized by extremely low DBDs (<0.1 g cm–3) and moderate POC concentrations (4–7 mg cm–3). Furthermore, sediment mass accumulation rates (MAR), based on 210Pb and 137Cs measurements and available for 303 sites of the Baltic Sea, were used for assessing the spatial distribution of POC burial rates. Overall, these vary between 14 and 35 g m–2 year–1 in the mud depositional areas and, in total, at least 3.5 (±2.9) Mt POC are buried annually. Distribution patterns of POC contents and burial rates are not identical for the central Baltic Sea because of the low MAR in this area. The presented data characterize Baltic Sea sediments as an important sink for organic carbon. Regional differences in organic carbon deposition can be explained by the origin and transport pathways of POC, as well as the environmental conditions prevailing at the seafloor (morphology, currents, redox conditions). These findings can serve to improve budget calculations and modelling of the carbon cycle in this large brackish-water marginal sea.  相似文献   

11.
The results of microbiological, biogeochemical, and isotope geochemical studies in the Kara Sea are described. The samples for these studies were obtained during the 54th voyage of the research vessel Akademik Mstislav Keldysh in September 2007. The studied area covered the northern, central, and southwestern parts of the Kara Sea and the Gulf of Ob. The quantitative characteristics of the total bacterial population and the activity of the microbial processes in the water column and bottom sediments were obtained. The total population of the bacterioplankton (BP) varied from 250000 cells/ml in the northern water area to 3000000 cells/ml in the Gulf of Ob. The BP population depended on the content of the water suspension. The net BP production was minimal in the central water area, amounting to 0.15–0.2 μg C/(l day), and maximal (0.5–0.75 μg C/(l day)) in the Gulf of Ob. The organic material at the majority of the stations in the Ob transect predominantly contained light carbon isotopes (−28.0 to −30.18‰) of terrigenous origin. The methane content in the surface water layer varied from 0.18 to 2.0 μl CH4/l, and the methane oxidation rate changed in the range of 0.1–100 nl CH4/(l day). The methane concentration in the upper sediment layer varied from 30 to 300 μl CH4/dm3; the rate of the methanogenesis was 44 to 500 nl CH4/(dm3 day) and that of the methane oxidation, 30 to 2000 nl CH4/(dm3 day). The rate of the sulfate reduction varied from 4 to 184 μg S/(dm3 day).  相似文献   

12.
Distribution of particulate organic carbon (POC) and dissolved organic carbon (DOC) in seawater, and chemical composition of surficial sediments were studied in relation to pulpmill effluent and dumping of dredge spoil containing wood debris in Alberni Inlet, British Columbia, Canada. The maximum concentration of POC (377–584µg Cl–1) was observed at the surface around the dumping area (5–7 km seaward of the inlet's head), and at the location immediately adjacent to the dump site POC was elevated throughout the water column (50 m). While POC tended to decrease in the surface layer for a distance of about 25km down-inlet, measureable effects of POC in the deeper water did not extend beyond 600m from the dump site. The dump site was conspicuous by the large maximum in C:N ratio (46.3). In contrast, DOC was observed to be highest (4.25mg Cl–1) at the head of the inlet where pulpmill effluent was being discharged and a secondary maximum was found about 10km down-inlet from the dump site. The data suggest that a considerable proportion of the dredge spoil sinks rapidly near the dump site, probably within several hundred metres. Some of the spoil, perhaps low density wood debris may travel considerably further with the surface water where by leaching it may contribute to some extent to the surface DOC before sinking into deeper water.  相似文献   

13.
In 1998–1999, beam attenuation coefficient (bac) profiles, suspended particulate matter (SPM) and particulate organic carbon (POC) concentrations were assessed during five cruises in the Saronikos Gulf, eastern Mediterranean, Greece. SPM and POC concentrations (0.05–1.84 mg l−1 and 10.2–468.6 μg l−1, respectively) exhibited strong spatial and temporal variations, related to the different environmental characteristics of various sectors of the gulf, including wind regime and biological productivity. The Elefsis and Keratsini bays, as well as the area around Psyttaleia Island, showed the highest POC concentrations. The vertical distribution of POC at stations in the western basin, as well as in the inner and outer Saronikos Gulf is characterised by higher POC concentrations in surface waters, associated with higher biological activity. The wastewater treatment plant effluents discharged south of the Psyttaleia Island are a major source of organic particles which directly influence the intermediate water layers, at least during the stratification period. Assessments of relationships between bac and SPM or POC concentrations revealed a relatively strong correlation between bac and POC. An equation converting bac readings to POC concentration was established which can be applied to historical and/or future bac measurements, independently of season. POC concentrations estimated from calibrated continuous transmissometer readings were used to estimate the standing stock of POC in the Saronikos Gulf, which varied between 6,110×106 and 13,450×106 g C during the period June 1998 to February 1999.  相似文献   

14.
三峡截流后长江口秋季TSM、POC和PN的分布特征   总被引：2，自引：0，他引：2  
基于2004年11—12月长江口56个站位的悬浮体调查资料,分析了长江口区悬浮体总量(TSM)、颗粒有机碳(POC)和颗粒氮(PN)质量浓度的平面分布特征,探讨该区TSM及颗粒有机质的物质来源和三峡截流对长江三角洲的影响。结果表明,表、底层TSM与POC、PN质量浓度之间存在显著的正线性相关关系并都呈现出南高北低的格局,说明了长江悬浮颗粒物入海后主要沿东南方向输运。POC、PN质量分数与POC、PN的质量浓度不同,它们与TSM质量浓度对数有负相关关系。由于河口区底质再悬浮作用显著,TSM和POC、PN质量浓度呈现表层低、底层高的特点。长江口悬浮体主要来自长江径流和底质沉积物的再悬浮。与三峡截流前数据的对比表明,截流对目前长江口区的TSM和POC尚未造成明显的影响。  相似文献   

15.
The data on the qualitative and quantitative variability of the organic matter (OM) and its transformation rates in the waters of the Ob Inlet during different seasons are considered. The OM distribution was quite nonuniform over the entire Ob Inlet aquatic area: the concentrations of Corg varied from 2.8 to 14.1 mg/L and from 0.32 to 4.59 mg/L for the dissolved and particulate forms, respectively. The maximum concentrations of dissolved OM were registered in the main flow of the Ob River water supplied to the bay, whereas the minimum concentrations were characteristic for the near-bottom layers formed by the Kara Sea waters of high salinity in the northern part of the bay. Both in the summer and in the autumn, the fraction of particulate matter within the total OM reached its maximum values in the mixing zone of the Taz and Ob riverine waters, as well as in the mixing zone of the Ob River and Kara Sea waters. These boundary zones were characterized by the widest variability of the elemental (C: N: P) and biochemical (proteins and carbohydrates) composition of the OM, as well as of its transformation rates measured by the activities of the enzymes (alkaline phosphatase and the electron transport system).  相似文献   

16.
During the first year of the Northeast Pacific GLOBEC program we examined the spatial distributions of dissolved and particulate organic carbon and nitrogen in the surface waters off the Oregon and Washington coasts of North America. Eleven east–west transects were sampled from nearshore waters to 190 km offshore. Hydrographic data and the distribution of inorganic nutrients were used to characterize three distinct water sources: oligotrophic offshore water, the Columbia River plume, and the coastal upwelling region inshore of the California Current. Warm, high salinity offshore water had very low levels of inorganic nutrients, particulate organic carbon (POC) and dissolved organic carbon (DOC). Warm, low salinity water in the Columbia River plume was relatively low in nitrate, but showed a strong negative correlation between salinity and silicate. The river plume water had the highest levels of total organic carbon (TOC) (up to 180 μM) and DOC (up to 150 μM) observed anywhere in the sampling area. Cold, high salinity coastal waters had high nutrient levels, moderate to high levels of POC and particulate organic nitrogen (PON), and low to moderate levels of DOC and dissolved organic nitrogen (DON). Each of these regions has characteristic C:N ratios for particulate and dissolved organic material. The results are compared to concentrations and partitioning of particulate and dissolved organic carbon and nitrogen in other regions of the North Pacific and North Atlantic Oceans.  相似文献   

17.
The considered area of the Russian sector of the Arctic Basin was characterized in August–September of 2008 by the wide horizontal and vertical variability of the concentrations of dissolved and particulate organic matter (OM), as well as of its elemental and biochemical composition. The concentration ranges amounted to 51.6–434 and 2.2–18.6 μM, respectively, for the dissolved and particulate Corg; up to 1.9–30.2 μM for Norg; and up to 0.08–1.53 μM for Porg. The maximum values were characteristic for the Russian Arctic shelf. The analysis of the authors’ and published data showed that a pronounced accumulation of OM, mainly in the dissolved form, took place in the Arctic Basin within the past 12 years. The concentrations of dissolved OM were higher in the western sector of the Russian Arctic than those in the eastern sector. The main biochemical components in all the waters constituting the Arctic Ocean are carbohydrates and lipids for dissolved OM and proteins and carbohydrates for particulate matter.  相似文献   

18.
Lipid classes in a small, eutrophicated salty lake (Rogoznica Lake, middle Adriatic), which is often subject to appeareance of anoxic conditions, were analyzed at the end of winter (March) and in summer (July) 2008. The results are supported with DOC, POC, phytoplankton, temperature, salinity and oxygen data. During both March and July massive, diatom blooms were recorded with maximum values at 5 m depth. Total lipids were found at high concentrations that were similar for the samplings in two months. Total particulate lipids dominated the pool, and showed large variations from 46.37 to 369.88 μg/l, with the highest concentration observed in the bottom anoxic layer in March. The variations for dissolved lipids were smaller and ranged from 44.82 to 124.35 μg/l. Opposite to lipids, DOC values increased 1.5 times between the two samplings, from the value of average 0.95 mg C/l in March to the average value of 1.44 mg/l in July. Conformingly with diatom blooms, POC was found in July at high concentrations (0.28–1.50 mg C/l), contributing to total organic carbon up to 46%. The distribution of organic carbon and lipids showed the tendency of accumulation toward deeper layers. The characterization of individual lipid classes revealed the dominance of phospholipids, indicating that the lipids in the lake mainly originated from the photosynthetically active phytoplankton community, which is sustained by high production of oxygen (oxygen saturation up to 200%). Low contribution of neutral lipids in the particulate fraction points to high availability of nutrients for present phytoplankton community. Lipid breakdown indices were found at significantly higher concentrations in March compared to July. Sea surface microlayer, the hydrophobic boundary, appeared to be generally lipid depleted in comparison to the sub-surface water. Qualitative analysis of sulfolipids revealed the potential of the lake for the occurrence of chemical interaction of sulfur with present organic matter.  相似文献   

19.
《Marine Chemistry》2001,76(3):155-174
Laboratory experiments were conducted to evaluate the net exchange of organic carbon (OC) between sediments and overlying water during episodes of resuspension. Surface sediment samples collected from six locations within the Hudson River Estuary and the Inner New York Bight were resuspended in their respective bottom waters for periods ranging from 30 s to 2 h. After resuspension, dissolved organic carbon (DOC) concentration generally reached levels greater than that predicted by conservative mixing of pore water and bottom water, indicating net release of OC from the sediment particles. The amount of OC released during the 1-h extractions comprised ≤0.1% of the total sediment pool, but correlated positively (R2=0.65, P<0.052) with the amount of particulate organic carbon (POC) found in the high-density fraction of the sediment matrix. This suggests that the mineral-bound fraction of sedimentary OC was the major source for the excess DOC released into solution, and that across various sedimentary environments, only a small (but fairly constant) fraction of the total sedimentary POC may be poised for rapid transfer to the water column.  相似文献   

20.
In most natural sedimentary systems labile and refractory organic material (OM) occur concomitantly. Little, however, is known on how different kinds of OM interact and how such interactions affect early diagenesis in sediments. In a simple sediment experiment, we investigated how interactions of OM substrates of different degradability affect benthic nitrogen (N) dynamics. Temporal evolution of a set of selected biogeochemical parameters was monitored in sandy sediment over 116 days in three experimental set-ups spiked with labile OM (tissue of Mytilus edulis), refractory OM (mostly aged Zostera marina and macroalgae), and a 1:1 mixture of labile and refractory OM. The initial amounts of particulate organic carbon (POC) were identical in the three set-ups. To check for non-linear interactions between labile and refractory OM, the evolution of the mixture system was compared with the evolution of the simple sum of the labile and refractory systems, divided by two. The sum system is the experimental control where labile and refractory OM are virtually combined but not allowed to interact. During the first 30 days there was evidence for net dissolved-inorganic-nitrogen (DIN) production followed by net DIN consumption. (Here ‘DIN’ is the sum of ammonium, nitrite and nitrate.) After  30 days a quasi steady state was reached. Non-linear interactions between the two types of OM were reflected by three main differences between the early-diagenetic evolutions of nitrogen dynamics of the mixture and sum (control) systems: (1) In the mixture system the phases of net DIN production and consumption commenced more rapidly and were more intense. (2) The mixture system was shifted towards a more oxidised state of DIN products [as indicated by increased (nitrite + nitrate)/(ammonium) ratios]. (3) There was some evidence that more OM, POC and particulate nitrogen were preserved in the mixture system. That is, in the mixture system more particulate OM was preserved while a higher proportion of the decomposed particulate N was converted into inorganic N. It can be concluded that during the first days and weeks of early diagenesis the magnitude and composition of the flux of decompositional dissolved N-compounds from sediments into the overlying water was influenced by non-linear interactions of OM substrates of different degradability. Given these experimental results it is likely that the relative spatial distributions of OM of differing degradability in sediments control the magnitude and composition of the return flux of dissolved N-bearing compounds from sediments into the overlying water column.  相似文献   

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