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1.
对南海表层沉积物与沉降颗粒物有机碳的δ13C进行了对比研究,从古环境再造方面探讨了陆源和海源对南海表层沉积物的贡献。南海表层沉积物有机碳的δ13C比沉降颗粒物中有机碳的δ13C偏重表明,Suess效应对南海现代过程的影响不可忽视,两者的δ13C差值反映了Suess效应对南海现代过程的影响程度。利用两者的δ13C差值,对现代陆源和海源有机碳的δ13C进行修正后,计算得到,在南海陆架周围表层沉积物的有机碳中,陆源的比例为48%,海源的比例为52%;在远离陆架的表层沉积物的有机碳中,陆源的比例为14%,海源的比例为86%。  相似文献   

2.
Concentrations and vertical distributions of total nitrogen (TN), total phosphorus (TP) and their different forms in sediments obtained from nine locations of Lake Dalinouer in September 2008 were analyzed. The results demonstrated that TP in surface sediments ranged from 0.493 to 0.904 g/kg, and inorganic phosphorus was the main fraction of total phosphorus, ranging from 335 to 738 mg/kg. Simultaneously, the autogenetic calcium phosphorus (ACa-P) was the main fraction of inorganic phosphorus, ranging from 145.4 to 543.2 mg/kg. Vertical distribution of different phosphorus forms in different sediment cores was distinguishing, and most of them tended to increase toward the surface sediment, indicated that the phosphorus concentration was related to the humanity with a certain extent. The relationships between TP and occluded phosphorus and ACa-P were significant. Nitrogen in the sediment was composed mainly of organic nitrogen, accounting for grater than 80 % of TN. NO3 ?-N was the dominate fraction of inorganic nitrogen in the surface sediment, ranging between 51 and 346 mg/kg (151.1 ± 104.4 mg/kg), and accounting for between 2.2 and 17.7 % of total sediment nitrogen (6.2 ± 5.6 %). The ratio of organic carbon and TN in sediment was in range of 6.0–25.8 and presented a tendency of lake centre >lake sides, indicating that nitrogen accumulated in the sediments from lake sides came mainly from terrestrial source and nitrogen was mainly autogenetic in lake centre. Ratio of N:P in all sampling sites was below 14, indicated that N was the limiting nutrient for algal growth in this lake.  相似文献   

3.
沉积物的物质来源问题是海洋沉积学所关注的关键问题。以北部湾涠洲岛海域的沉积柱样为例,在过剩210Pb法构建良好的年代框架基础上,利用元素、稳定同位素、放射性核素多种方法,解析沉积物中有机物和无机物的来源问题。结果显示:基于δ13C指标获得的沉积物中海源和陆源有机物的平均贡献比例分别为95.0%和5.0%;基于Al、Cu、40K、226Ra多种代用指标的端元混合模型计算沉积物中生物成因和碎屑成因的无机物平均贡献比例分别为64.1%和35.9%;而沉积物中Pb分布无法满足端元混合模型的结果,说明存在人类活动的可能影响。进一步构建沉积柱样中基于δ13C的陆源有机物和基于40K的生源无机物的贡献比例的年代变化趋势,发现该变化趋势与人类活动和气候变化（厄尔尼诺现象）密切相关。总之,利用元素、稳定同位素、放射性核素多种方法综合解析沉积物中物质来源问题,尝试探索多种物源识别的代用指标,为北部湾涠洲岛海域的生态环境管理提供一定的科学依据。  相似文献   

4.
Analyses of organic carbon, total nitrogen, and inorganically bound ammonium (exchangeable and fixed ammonium) in two oxic deep-sea sediment cores from the Central Pacific Ocean revealed insufficiently high inorganic ammonium contents of these sediments to explain the low C/N ratios, although representing 20–45% of the total nitrogen.Both, organic carbon/total nitrogen ratios (ranging from 3.9?1.3) and organic carbon/organic nitrogen ratios (5.6?1.9) decrease with increasing sediment depth, the latter indicating a real enrichment of organic nitrogen compounds during diagenesis relative to total organic matter.Organic matter/alumina relationships indicate that this unusual preservation of organic nitrogen compounds is probably caused by sorption to clay minerals protecting them against bacterial attack.  相似文献   

5.
Allochthonous inputs of suspended particulate matter from freshwater environments to estuaries influence nutrient cycling and ecosystem metabolism. Contributions of different biogeochemical reactions to phosphorus dynamics in Tomales Bay, California, were determined by measuring dissolved inorganic phosphorus exchange between water and suspended particulate matter in response to changes in salinity, pH, and sediment redox. In serum bottle incubations of suspended particulate matter collected from the major tributary to the bay, dissolved inorganic phosphorus release increased with salinity during the initial 8 h; between 1–3 d, however, rates of release were similar among treatments of 0 psu, 16 psu, 24 psu, and 32 psu. Release was variable over the pH range 4–8.5, but dissolved inorganic phosphorus releases from sediments incubated for 24 h at the pH of fresh water (7.3) and seawater (8.1) were similarly small. Under oxidizing conditions, dissolved inorganic phosphorus release was small or dissolved inorganic phosphorus was taken up by particulate matter with total P content <50 μmoles P g?1; release was greater from suspended particulate matter with total phosphorus content >50 μmoles P g?1. In contrast, under reducing conditions maintained by addition of free sulfide (HS?), dissolved inorganic phosphorus was released from particles at all concentrations of total phosphorus in suspended particulate matter, presumably from the reduction of iron oxides. Since extrapolated dissolved inorganic phosphorus release from this abiotic source can account for only 12.5% of the total dissolved inorganic phosphorus flux from Tomales Bay sediments, we conclude most release from particles is due to organic matter oxidation that occurs after estuarine deposition. The abiotic, sedimentary flux of dissolved inorganic phosphorus, however, could contribute up to 30% of the observed net export of dissolved inorganic phosphorus from the entire estuary.  相似文献   

6.
Transport and fate of organic carbon by the fluvial system play a significant role in the global biogeochemical cycle of carbon. Previous studies show that the transportation of modern organic carbon from the Himalayan River system accounts for 10–20% of the total global flux to the oceans. Till date, no study has been published which dealt with the transport of organic carbon in the headwaters of the Ganga River. The Alaknanda River is a headwater stream of the Ganga, which flows in the Western Himalayas of India. Water and freshly deposited channel sediment samples were collected during the months of March 2014 and August 2014 and analysed for dissolved organic carbon (DOC), particulate organic carbon (POC) and channel organic carbon (COC). The observed variability of organic carbon concentration was correlated with factors such as discharge, physiography and suspended sediment concentration (SSC). The results show that seasonal erosivity in the basin influences its DOC concentration and physiography, thus acting as a key parameter which controls transportation, oxidation and residence time of the organic matter. The allochthonous input of sediments from the erosional activities is the major source of organic carbon. At Devprayag, Alaknanda contributes 66% of the total DOC flux carried by the Ganga River. The comparison with the previously published values indicate that due to differences in physiography and chemical weathering rate, the Ganga River transports organic carbon mainly as a dissolved load in its upstream and predominantly as POC down the Himalayan foothills.  相似文献   

7.
Data on hydrography, nutrients, suspended particles, and sedimented particles were collected at weekly intervals from November to May during 1995 to 1997 at a station in the coastal waters of Dona Paula Bay, India. Suspended and sedimented particles were analyzed for total suspended matter (SPM), total sedimented particulate matter (TPM), particulate organic carbon (POC), particulate organic nitrogen (PON), chlorophylla (chla), and diatom abundance. Variations in hydrography and nutrients influenced the quantity and composition of sedimented particles. The TPM, POC, PON, and chla fluxes showed small-scale seasonal variations and were higher in the summer (February to May) than in the winter (November to January). Resuspension of carbon accounted for approximately 25% of the gross POC and was highest in April 1997 (45%). The mean net POC flux was 197±90 mg C m−2 d−1 and accounts for 4.6% of the TPM. The average C∶N (w∶w) ratio of the sedimented material was 13.2±6.6. The POC:chla ratio was relatively higher in the sedimented material as compared to the suspended material. The particulate carbon reaching the bottom sediment was 39% of the primary production. The low organic carbon concentration (approximately 0.1% of dry sediment) in the sediments implies that about 98% of the sedimented carbon was either consumed at the sedimentwater interface or resuspended/advected before it was finally buried into the sediments.  相似文献   

8.
From February 1992 until June 1993, the distribution of dissolved and particulate phosphorus and nitrogen was investigated in the Ems estuary at approximately monthly intervals. Nutrient import was quantified from the river load. Nutrient export to sea was quantified from river discharge and from the salinity-nutrient gradient in the outer estuary. In addition, sediment cores were taken from four sites along the main axis of the estuary in October 1992. On the basis of these data a nitrogen and phosphorus budget was made. On an annual basis, 45 × 106 mol P and 2,360 × 106 mol N are imported into the Ems estuary. Freshwater runoff is the main source of input, accounting for about 92% of the nitrogen input and 71% of the phosphorus input. Import of particulate phosphorus from the sea is important in the phosphorus budget (27%). Seventy-five percent of the nitrogen input is transported to the North Sea. Denitrification is the major loss factor (19% of the nitrogen input), and burial explains 6%. Of the phosphorus input, 60% is transported to the North Sea and 40% accumulates in the sediment. Nitrogen import during summer explains about one third of the annual primary production, indicating that nitrogen turn over is about three times. Phosphorus import during summer explains less than 16% of the annual primary production. We suggest that trapping of particulate P and adsorption onto Fe(oxy)hydroxides during the entire year and the release of Fe-bound P during summer after reduction of Fe(oxy)hydroxides is instrumental in sustaining high primary production, which could not be sustained if it depended only on P imported during the growing season.  相似文献   

9.
One year’s measurements of surficial sedimentation rates (1986–1987) for 26 Maine marsh sites were made over marker horizons of brick dust. Observed sediment accumulation rates, from 0 to 13 mm yr?1, were compared with marsh morphology, local relative sea-level rise rate, mean tidal range, and ice rafting activity. Marshes with four different morphologies (back-barrier, fluvial, bluff-toe, and transitional) showed distinctly different sediment accumulation rates. In general, back-barrier marshes had the highest accumulation rates and blufftoe marshes had the lowest rates, with intermediate values for transitional and fluvial marshes. No causal relationship between modern marsh sediment accumulation rate and relative sea-level rise rate (from tide gauge records) was observed. Marsh accretionary balance (sediment accumulation rate minus relative sea-level rise rate) did not correlate with mean tidal range for this meso- to macro-tidal area. Estimates of ice-rafted debris on marsh sites ranged from 0% to >100% of measured surficial sedimentation rates, indicating that ice transport of sediment may make a significant contribution to surficial sedimentation on Maine salt marshes.  相似文献   

10.
Chesapeake Bay sediments were examined for biogeochemical evidence of eutrophication trends using two mesohaline sediment cores. Measurements of 210Pb geochronology and sediment profiles of organic carbon, nitrogen, organic phosphorus, inorganic phosphorus, and biogenis silica (BSi) were used used to develop temporal concentration trends. Recent sediments have 2–3 times as much organic carbon and nitrogen as sediments from 80 to 100 yr ago, but the increases result from both changes in organic matter deposition and time-dependent changes in organic matter decomposition rates. Despite increases in phosphorus loading, no major changes in phosphorus concentration were noted throughout most of the century; anthropogenic phosphorus deposition, though not evident in sulfidic mid-bay sediments, must occur in more oxidizing sediment environments in both the northern and southern bays. Temporal trends in BSi concentrations are much less evident and the lack of substantial increases in this century suggest that BSi inputs may be capped by late spring-summer Si limitation.  相似文献   

11.
Total nitrogen, phosphorus and organic carbon were compared in natural and transplanted estuarine marsh soils (top 30 cm) to assess nutrient storage in transplanted marshes. Soils were sampled in five transplanted marshes ranging in age from 1 to 15 yr and in five nearby natural marshes along the North Carolina coast. Dry weight of macroorganic matter (MOM), soil bulk density, pH, humic matter, and extractable P also were measured. Nutrient pools increased with increasing marsh age and hydroperiod. Nitrogen, phosphorus and organic carbon pools were largest in soils of irregularly flooded natural marshes. The contribution of MOM to marsh nutrient reservoirs was 6–45%, 2–22%, and 1–7% of the carbon, nitrogen and phosphorus, respectively. Rates of nutrient accumulation in transplanted marshes ranged from 2.6–10.0, 0.03–1.10, and 84–218 kmol ha?1yr?1 of nitrogen, phosphorus and organic carbon, respectively. Accumulation rates were greater in the irregularly flooded marshes compared to the regularly flooded marshes. Approximately 11 to 12% and 20% of the net primary production of emergent vegetation was buried in sediments of the regularly flooded and irregularly flooded transplanted marshes, respectively. Macroorganic matter nutrient pools develop rapidly in transplanted marshes and may approximate natural marshes within 15 to 30 yr. However, development of soil carbon, nitrogen and phosphorus reservoirs takes considerably longer.  相似文献   

12.
Surficial sediment composition and spatial variability reflect the dynamics and level of natural and anthropogenic impact in estuarine systems. The aim of this study is to evaluate some key environmental and sedimentary variables, as well as to evaluate the current environmental quality in the tide-dominated Caravelas estuarine system (Brazil). Sixty-five surficial sediment samples were studied for grain size as well as calcium carbonate, total organic carbon, total nitrogen, metals, semi-metals and rare earth elements and for organic matter δ13C. Based on the spatial distribution of these data and summarizing our findings, three sectors can be individualized in the Caravelas estuarine system: i. Barra Velha inlet; ii. the main channel of the Caravelas estuary, and iii. the channel interconnecting Caravelas and Nova Viçosa estuaries. In the inlet the sedimentary organic matter is provided essentially by marine sources, which corroborates the small continental input. Freshwater dissolved organic carbon and particulate organic carbon occur in the interconnecting channel, proving the occurrence of the residual transport towards the Caravelas estuary, with continental contribution towards Caravelas River. The geochemical fingerprint indicates that the Barreiras Group, composed by Neogene terrigenous deposits, located west of the study area, as an important source of terrigenous material to the entire Caravelas estuary system. The higher values of heavy rare earth elements (between 20 and 30 mg kg−1) in the northern sector of the study area may be related to the high degree of chemical weathering in magmatic or metamorphic rocks, which occur to the north of the study area.  相似文献   

13.
From November of 1973 to May of 1974, 15 arrays of sediment traps were placed along 33 km of southern Lake Champlain to sample the distribution of effluent from a large paper plant located on the western shore which had commenced operation in 1971. In the arrays located near the effluent diffuser pipeline as much as 2.3 cm of sediment accumulated, whereas elsewhere in the lake less than 1 cm accumulated. In the area of accelerated accumulation, sediments contained high concentrations of several components used in or derived from paper manufacturing. Values for kaolinite, expressed as the ratio of kaolinite to chlorite, for example, were as high as 1.4, anatase (TiO2) concentrations were as high as 0.8%, organic carbon 8.7%, and phosphorus 254 μg/g; all were more abundant than in sediments collected in traps to the south or north. In surficial bottom sediments collected near each array organic carbon and phosphorus were also higher (4.2% and 127 μg/g respectively) near the diffuser than elsewhere. Thus, the new plant after three years of production measurably affected the composition of suspended sediment and surficial bottom sediment despite the construction and use of extensive facilities to reduce the flow of pollutants to the lake.  相似文献   

14.
Long-term interdisciplinary studies of the Rhode River estuary and its watershed in the mid-Atlantic coastal plain of North America have measured fluxes of nitrogen and phosphorus fractions through the hydrologically-linked ecosystems of this landscape. These ecosystems are upland forest, cropland, and pasture; streamside riparian forests; floodplain swamps; tidal brackish marshes and mudflats; and an estuarine embayment. Croplands discharged far more nitrogen per hectare in runoff than did forests and pastures. However, riparian deciduous hardwood forest bordering the cropland removed over 80 percent of the nitrate and total phosphorus in overland flows and about 85 percent of the nitrate in shallow groundwater drainage from cropland. Nevertheless, nutrient discharges from riparian forests downslope from croplands still exceeded discharges from pastures and other forests. The atomic ratio of nitrogen to phosphorus discharged from the watersheds into the estuary was about 9 for total nutrients and 6 for inorganic nutrient fractions. Such a low N:P ratio would promote nitrogen rather than phosphorus limitation of phytoplankton growth in the estuary. Estuarine tidal marshes trapped particulate nutrients and released dissolved nutrients. Subtidal mudflats in the upper estuary trapped particulate P, released dissolved phosphate, and consumed nitrate. This resulted in a decrease in the ratio of dissolved inorganic N:P in the estuary. However, the upper estuary was a major sink for total phosphorus due to sediment accretion in the subtidal area. Bulk precipitation accounted for 31 percent of the total nongaseous nitrogen influx to the landscape, while farming accounted for 69 percent. Forty-six percent of the total non-gaseous nitrogen influx was removed as farm products, 53 percent either accumulated in the watershed or was lost in gaseous forms, and 1 percent entered the Rhode River. Of the total phosphorus influx to the landscape, 7 percent was from bulk precipitation and 93 percent was from farming. Forty-five percent of the total phosphorus influx was removed as farm products, 48 percent accumulated in the watershed, and 7 percent entered the Rhode River. These nitrogen and phosphorus discharges into the Rhode River, although a small fraction of total loadings to the watershed, were large enough to cause seriously overenriched conditions in the upper estuary.  相似文献   

15.
对崇明东滩采集的表层样和柱状样品，进行样品的总磷(TP)、无机磷(IP)和有机磷(OP)以及有机质含量等的测定，分析了磷的分布变化特征并对其影响因素和环境意义进行了探讨。  相似文献   

16.
Observations of the composition and rate of input of organic matter to the sea floor were made at three locations in lower Cook Inlet, Alaska, during five cruises taken in the spring and summer of 1978. Total particulate, plant pigment, carbon, nitrogen, fecal pellet, and phytoplankton cell fluxes, inferred from sediment trap samples, were related to algal biomass and production in overlying waters. A daily average of 7.5% of the phytoplankton biomass was lost to the bottom. Of this loss, 83% was attributable to zooplankton grazing and fecal pellet production. At the three sampling sites, an average of 39 g C m?2 (range of 17–60 g C m?2, was sedimented to the bottom between May and August. This carbon flux represented an average of 12% of the total primary production measured for that time period. Kachemak Bay eastern arm of the inlet, is identified as an extremely productive embayment in which large amounts of organic matter were transferred to the sea floor.  相似文献   

17.
Net system production ranged from 13% to 29% of apparent system production in enclosures modelling coastal marine waters. Net production was measured by direct and indirect methods along with factors which impact its magnitude and fate. The direct measures of carbon, phosphorus, and nitrogen content of accumulating flocculent material in enclosures without sediment agreed with indirect measures by net system metabolism and by net sediment storage from nutrient mass balances. Increased nutrient supply, increased the absolute, but not relative, net system production ultimately stored in the sediment. Net production as dry weight of floc did not agree with that calculated from oxygen metabolism owing to a high silicon content of the organic matter. The presence of a benthic macrofauna decreased net system production storage by about 28–54%.  相似文献   

18.
辽河大伙房水库汇水区农业非点源污染入库模拟   总被引：1，自引：0，他引：1  
利用输出系数法和SWAT模型,对大伙房水库汇水区农业非点源污染(ANSP)进行了入库模拟研究,并用2006—2009年的水文和水质监测数据对模型进行了校准和验证。研究结果表明:汇水区年均输入到水库的泥沙量、总氮和总磷负荷分别为82.65×103 t、1 873.49t和81.97t;月入库泥沙量、总氮和总磷负荷与径流量有着较强的相关性,ANSP的产生和迁移受降水、径流过程影响很大,每年7、8月份的氮、磷和泥沙流失量达到年内最大值,分别占全年流失总量的42.64%、44.42%和67.91%。水库汇水区各流域对水库氮、磷污染的贡献率由大到小依次为:浑河流域(清原段)、苏子河流域、社河流域和水库周边小流域。  相似文献   

19.
External nutrient loadings, internal nutrient pools, and phytoplankton production were examined for three major subsystems of the Chesapeake Bay Estuary—the upper Mainstem, the Patuxent Estuary, and the 01 Potomac Estuary—during 1985–1989. The atomic nitrogen to phosphorus ratios (TN:TP) of total loads to the 01 Mainstem, Patuxent, and the Potomac were 51, 29 and 35, respectively. Most of these loads entered at the head of the estuaries from riverine sources and major wastewater treatment plants. Approximately 7–16% for the nitrogen load entered the head of each estuary as particulate matter in contrast to 48–69% for phosphorus. This difference is hypothesized to favor a greater loss of phosphorus than nitrogen through sedimentation and burial. This process could be important in driving estuarine nitrogen to phosphorus ratios above those of inputs. Water column TN: TP ratios in the tidal fresh, oligohaline, and mesohaline salinity zones of each estuary ranged from 56 to 82 in the Mainstem, 27 to 48 in the Patuxent, and 72 to 126 in the Potomac. A major storm event in the Potomac watershed was shown to greatly increase the particulate fraction of nitrogen and phosphorus and lower the TN:TP in the river-borne loads. The load during the month that contained this storm (November 1985) accounted for 11% of the nitrogen and 31% of the phosphorus that was delivered to the estuary by the Potomac River during the entire 60-month period examined here. Within the Mainstem estuary, salinity dilution plots revealed strong net sources of ammonium and phosphate in the oligohaline to upper mesohaline region, indicating that these areas were sites of considerable internal recycling of nutrients to surface waters. The sedimentation of particulate nutrient loads in the upper reaches of the estuary is probably a major source of these recycled nutrients. A net sink of nitrate was indicated during summer. A combination of inputs and these internal recycling processes caused dissolved inorganic N to P ratios to approach 16:1 in the mesohaline zone of the Mainstem during late summer; this ratio was much higher at other times and in the lower salinity zones. Phytoplankton biomass in the mesohaline Mainstem reached a peak in spring and was relatively constant throughout the other seasons. Productivity was highest in spring and summer, accounting for approximately 33% and 44%, respectively, of the total annual productivity in this region. In the Patuxent and Potomac, the TN:TP ratios of external loads documented here are 2–4 times higher than those observed over the previous two decades. These changes are attributed to point-source phosphorus controls and the likelihood that nitrogen-rich nonpoint source inputs, including contributions from the atmosphere, have increased. These higher N:P ratios relative to Redfield proportions (16:1) now suggest a greater overall potential for phosphorus-limitation rather than nitrogen-limitation of phytoplankton in the areas studied.  相似文献   

20.
《Applied Geochemistry》2004,19(5):769-786
Heavy metal (Zn, Cd, Cu and Pb) mass balances in the Lot-Garonne fluvial system have been established for 1999 and 2000. The mean annual discharges of these years are close to the mean discharge of the previous decade. The estimated annual dissolved and particulate fluxes in this model watershed integrate daily input from diffuse and point sources, diffusive fluxes at the water/sediment interface, changes in the dissolved-particulate partition and changes in sediment stock. Cadmium, Zn, Cu and Pb entering the Gironde estuary via the Garonne River (11–14 t a−1 of Cd; 1330–1450 t a−1 of Zn; 126–214 t a−1 of Cu and 127–155 t a−1 of Pb) are mainly transported in the particulate phase and the major part (i.e. ∼74 to 96% for Cd, ∼60% for Zn, ∼50 to 60% for Cu and ∼80% for Pb) is transported by the Lot River. The main anthropogenic heavy metal point source is located in a small upstream watershed (Riou-Mort River) accounting for at least 47% (Cd), ∼20% (Zn), ∼4% (Cu) and ∼7 to 9% (Pb) of the total heavy metal inputs into the Garonne River, although it contributes only 1% of the discharge. Mass balances for 1999 suggest that under mean annual hydrologic conditions on the basin scale, the heavy metal budget of the Lot-Garonne fluvial system is balanced and that the stocks of Cd [200 t; Environ. Tech. 16 (1995) 1145] and Zn in the Lot River sediment are constant under mean discharge conditions. Heavy metal input by molecular diffusion at the sediment surface represents an important component of dissolved metal inputs into the system (e.g. 30% for Cu). Except for Cu, these dissolved inputs are totally removed from solution by SPM. Based on the generally constant Zn/Cd (∼50) concentration ratio in sediment cores from the polluted Lot River reaches and the sediment stock of Cd [200 t; Environ. Tech. 16 (1995) 1145], the present day Zn stock in the Lot River sediments has been estimated at about 10,000 t. In addition to the mobilization of river-bed sediment and associated heavy metals by intense floods, local human activities, including river-bed dredging, may strongly modify the heavy metal budget of the river system. In 2000, the dredging-related remobilization of polluted Lot River sediment released 2–6 t Cd. This additional Cd point source was estimated to account for 15–43% of the gross inputs into the Gironde Estuary.  相似文献   

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