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1.
Amino acid biogeo- and stereochemistry in coastal Chilean sediments   总被引：1，自引：0，他引：1  
The spatial distribution of total hydrolysable amino acids (THAA) and amino acid enantiomers (d- and l-forms) was investigated in sediments underlying two contrasting Chilean upwelling regions: at ∼23 °S off Antofagasta and at ∼36 °S off Concepción. The contribution of amino acids to total organic carbon (%TAAC: 7-14%) and total nitrogen (%TAAN: 23-38%) in surface sediments decreased with increasing water depth (from 126 to 1350 m) indicating that organic matter becomes increasingly decomposed in surface sediments at greater water depth. Changes in the ratio between the protein amino acid aspartate and its non-protein degradation product β-alanine confirmed this observation. Furthermore, estimates of THAA mineralization showed that sedimentary amino acid reactivity decreased with both increasing water depth as well as progressive degradation status of the organic matter that was incorporated into the sediment. Reactivity of organic matter in the sediment was also assessed using the Degradation Index (DI) developed by [Dauwe, B., Middelburg, J.J., 1998. Amino acids and hexosamines as indicators of organic matter degradation state in North Sea sediments. Limnol. Oceanogr.43, pp. 782-798.]. Off Concepción, DI was successfully applied to examine the degradation status of sedimentary organic matter at different water depths. However, unexpected results were obtained at the Antofagasta stations as DI increased with sediment depth, suggesting more degraded organic matter at the surface than deeper in the cores. The contribution of peptidoglycan amino acids to THAA was estimated from the concentrations of d-aspartate, d-glutamic acid, d-serine, and d-alanine. Peptidoglycan amino acids accounted for >18% of THAA in all investigated samples. In surface sediments peptidoglycan amino acids accounted for a progressively larger fraction of THAA at increasing water depths (up to >26%). Further, the contribution of peptidoglycan amino acids to THAA increased with increased sediment depth and age (up to 288-year-old) reaching up to 59%. Independent estimates based on d-amino acid concentrations in selected laboratory strains, bacterial counts and the sedimentary concentrations of d-amino acids indicate that a large fraction of the measured d-amino acids (>47 to >97%) originated from cell wall residues rather than from enumerated cells.  相似文献   

2.
对2003年中国第二次北极科学考察所获得的部分表层沉积物样品进行了总水解氨基酸(THAA)、氨基糖(HA)的测定。不同区域氨基酸主要成分不同,楚科奇海站位的氨基酸主要成分为甘氨酸(Gly)、谷氨酸(Glu),位于加拿大海盆的B80、B11、P27站THAA的主要成分为丝氨酸(Ser)。沉积物的总有机碳(TOC)、总氮(TN)、THAA、HA含量等特征随区域不同有较大差别,白令海峡的BS11站TOC、HA含量最低,加拿大海盆的B80站THAA、TN含量最低。楚科奇海R03站TOC、TN为最高,THAA在R11含量达最大值,HA在楚科奇海台的P11站最高。初步讨论了楚科奇海—加拿大海盆表层沉积物中氨基酸的空间分布,根据氨基酸选择性降解和主成份分析结果引入DI”指标,并对七个站位表层沉积物有机质新鲜程度进行了比较,新鲜度由大至小顺序为C15>BS11>R11>S11>P11>R03>B80,这与表层沉积物来源、水动力条件等有关,由此推测楚科奇海陆架、白令海峡沉积物有机质较楚科奇海台、加拿大海盆较为新鲜。  相似文献   

3.
通过对南太平洋劳盆地东劳扩张中心(ELSC)表层沉积物进行水解氨基酸(THAA)分析、氨基酸对映异构体比值(D/L)分析及总有机碳(TOC)分析,对沉积物中氨基酸含量和来源、有机质降解程度和采样区域生物活动性及温度特征等问题进行了探讨。结果表明,ELSC区域样品中有机质含量较低,TOC含量为0.70～2.15 mg/g(干重),THAA含量为30～511μg/g(干重),热液活动区域原位化能合成作用对沉积物中氨基酸的相对富集有较大的贡献。沉积物中THAA含量和生物群落活动状况与分布范围有关,样品矿物组分对氨基酸的保存亦有一定的影响。由于各采样点热液活动、沉积物类型、生物群落的类型及分布均有所不同,样品中个体氨基酸的组成分布特征有较大差异。以TOC中氨基酸态碳所占百分比TAAC%作为指标对样品有机质活性进行了判别,热液喷口区域样品有机质新鲜程度要普遍高于非热液喷口区域样品,高温热液环境对氨基酸降解途径有一定的影响。样品中个体氨基酸D/L比值变化范围较大,天冬氨酸(Asp)为0.08～0.46,谷氨酸(Glu)为0.06～0.19,丝氨酸(Ser)为0.01～0.81,丙氨酸(Ala)为0.10～0.30。根据样品中THAA含量、TAAC%及个体氨基酸的D/L比值可以粗略判断生物活动性的大小及细菌对THAA的相对贡献,但并不能准确地区分热液活动活跃区域和非活跃区域在温度和生物活动性方面的差异。  相似文献   

4.
Mineralization of organic matter (OM) in sediment is crucial for biogeochemical cycle of nitrogen (N) and phosphorus (P) in lake ecosystem. Light fraction OM (LFOM) is a reactive pool in sediment and is considered as labile fraction contributing to N and P cycling. In our study, the effect of LFOM on the process and characteristics of N and P mineralization in sediments of Taihu Lake were investigated with 77-day waterlogged incubation plus intermittent leaching at 27°C. Sediments from Yuantouzhu (Y) and Gonghu (G) were used, which were removed the LF. Results indicated that the organic nitrogen mineralized ranged from 14.3 to 19.5% of total nitrogen (193.49–378.93 mg kg−1 sediment) and the organic phosphorus mineralized ranged from 5.7 to 7.9% of total phosphorus (19.86–60.65 mg kg−1 sediment). The heavily polluted sediment had a higher mineralization rate and net mineral-N and mineral-P than slightly polluted sediment. LF stimulated the initial amounts of inorganic N and P and also can be the potential source for mineralization. After the LFOM removal, the net mineral-N of Y and G decreased 116.47 mg kg−1 sediment and 48.03 mg kg−1sediment, respectively, and the net mineral-P decreased 2.67 mg kg−1sediment for Y and 4.82 mg kg−1sediment for G. Two models were used to fit the observed mineral-N data vs. incubation days using a non-linear regression procedure: one is the effective cumulated temperature model, a thermodynamic model which assumes that N mineralization is affected by temperature; the other is the single first-order exponential model, which is a dynamic model. Based on root mean square error values for the two models, the effective cumulated temperature model made a better prediction of N mineralization than the other model for all the four treatments. The single first-order exponential model underestimated N mineralization during the first 14 days and the last 21 days, and overestimated it in the other days during the 77-day incubation. This indicated that temperature was the primary factor influencing N mineralization and the amount of mineral-N were correlated significantly with the effective cumulated temperature (T ≥ 15°C) and incubation time when waterlogged incubation plus intermittent leaching was used.  相似文献   

5.
We compared the degradation behaviour of amino sugars (ASs) and amino acids (AAs) during sedimentation in two lakes. Concentrations of individual ASs and AAs were measured in plankton, sediment trap and sediment samples from Lake Zug (LZ; eutrophic, stratified, permanently anoxic below 170 m) and Lake Brienz (LB; oligotrophic, oxic throughout the water column). In the plankton samples AAs comprised 37–50% of the organic carbon (Corg) and 41–65% of the N. With increasing water depth the fraction of Corg and N as AAs almost halved in both lakes. At the sediment surface the contribution of AAs to the Corg pool was slightly greater, but in the sediments the proportion further decreased downwards to values of 1% of the Corg pool in LB and 8% in LZ, and 3% and 17% of the N pool, respectively. ASs contributed to a smaller extent to the planktonic organic matter (OM). Within the water column, the contribution decreased in both lakes. In contrast, in the sediments the contribution of ASs to the Corg and N pools increased slightly with depth, indicating AS accumulation. We applied degradation indices based on ASs, AAs and chlorins, which all revealed transformation with OM sedimentation. However, some indices were more sensitive to early degradation (e.g. reactivity index) and others to an intermediate level of degradation (e.g. chlorin index and non-protein AAs). Despite the different trophic status and redox conditions, the general pattern of degradation was similar in both lakes, but was more pronounced in the sediments of the eutrophic LZ.  相似文献   

6.
Sources of organic matter (OM) and lipids were assessed and factors affecting OM degradation were studied for two sediment cores representing distinct depositional regimes (i.e., the oscillating oxic to suboxic/anoxic western basin and oxic Zaka Bay) for eutrophic Lake Bled, NW Slovenia. Lower surface organic carbon (OC) concentration was determined in the western basin than for Zaka Bay sediments (5.1 vs. 5.4 wt% dry sediment, respectively), but one order of magnitude greater total lipid concentration was observed in the former. Also, there was a higher proportion of autochthonous OM in the western basin (77% vs. 66%) on the basis of atomic C/N ratios. Lipid-based origin assessment suggested a similar contribution of autochthonous OM in the western basin (64–77%), but a lower one in Zaka Bay (<50%). It seems that redox potential is the main factor governing OM degradation in the western basin. In contrast, a contribution from more refractory terrestrial OM, via the surface inflow in Zaka Bay, and higher sedimentation rates may surpass redox effects in Zaka Bay. Overall, oxygen may play a more important role in degradation of the more labile pool (i.e., lipids) than bulk OM. Higher apparent degradation rate constants (k′) for lipids also suggested a greater lability than for OC, while respective k′ values were higher in the oxic than anoxic environment.  相似文献   

7.
Investigation of biogeochemistry and amino acids on a 30-m-long core from Mansar Lake has thrown light on palaeoclimate variability during the Holocene period. The C/N ratio between 6 and 10 with some deviations and δ13C mostly between −20 and −22‰ in the shallow core, as well as a C/N ratio greater than 13 reaching from 19 to 20 and correspondingly lower δ13C of –28‰ in the deeper core suggest an aquatic source of carbon in the former and a cellulose-rich land plant source in the latter. This is supported by the abrupt increase in organic carbon content in the deeper core compared to the shallow core, which indicates a hot and wet climatic regime during the early Holocene and dry and cold during the late Holocene period. The amino acid data AA-C/C% and AA-N/N% are higher in shallow sediments compared to deeper sediments, indicating an aquatic plant source in the shallow core and greater supply of land plant sources in the deeper core. The lower percentage of the non-protein amino acids β-alanine (ALA) and γ-amino-butyric acid in the shallow core compared to the deeper core indicates different sources of organic matter in the lake basin. The higher amino acid ratio Asp/β-Ala (16.99 av.) and Glu/γ-Aba (18.18 av.) in the shallow core and lower ratios (10.32 and 12.41 av.) in the deeper core, and Asp/Glu (1.52 av.) and β-Ala/γ-Aba (1.61 av.) ratios in the former, which are potential indicators of the nature of the organic matter, are higher in the shallow core relative to the deeper core (1.33 and 1.23 av.), indicating relative biodegradation of organic matter in deeper sediments. It has been observed that the organic matter associated with the dry season is relatively less biodegraded, as evidenced from their higher ratios, and is more biodegraded in the wet season as their ratios are lower in the river sediments. In the absence of a bacterial contribution of organic matter from the soil source in this lake, since Mansar Lake is a non-drainage type, it is envisaged that the climatic variation may be responsible for biodegradation in the deeper core sediments. Therefore, the C/N ratio and δ13C values supported by amino acid data, the latter being significant in revealing primary productivity and a terrestrial source of organic matter, suggest a hot and wet climatic regime during the early Holocene (ca. 7580 bp) and a dry and cold in the late Holocene period (ca. 4050 bp).  相似文献   

8.
The source, quantity and quality of sedimentary organic matter (SOM) were investigated in the surface sediments of Lake Fuxian, a deep oligotrophic lacustrine system in China. Granulometry, biochemical organic composition, bulk organic proxies and their stable isotopes were determined in the surface sediments (0–4 cm). The values of δ13C, δ15N and atomic ratio of total organic carbon to total nitrogen (TOC/TN) indicated that the sediments in the large partial lake were influenced by autochthonous organic matter. The concentrations of TOC, protein (PRT) and total hydrolysable amino acids may be mainly modulated by phytodetritus sinking from euphotic zones since they correlated significantly with chlorins. Otherwise, the lack of correlation between chlorins concentrations and carbohydrate (CHO) and lipid (LIP) indicated that the latter may have an additional terrestrial source. The highest sediment quantity was found in the deepest station NC owing to its fine sediment. Stations near northwestern shore accumulated more SOM than other littoral stations, which was in accordance with sewage discharge strength. Degradation quality indices, such as chlorin index, degradation index, PRT/CHO, and LIP/CHO, were in general agreement in showing the degraded status of SOM in Lake Fuxian. No clear spatial patterns were found in sediment degradation quality, which may be influenced by bottom oxygen concentration in the deep stations.  相似文献   

9.
Newly vegetated sites provide opportunities to enlighten organic matter (OM) transformation mechanisms in soils and sediments at very early stages of development which, in turn, is relevant to better understand general ecosystem functioning. Mine acid soils and sediments in the Lusatian open cast lignite mining district (Germany) contains a high concentration of fossil carbon (lignite) in ad mixture with recent OM from the local vegetation, both contributing to the humified OM pool. In this study, analytical pyrolysis (Py–GC–MS) was used to monitor the different C sources (lignite or plant derived) in developing mine tailing soils and sediments and their degree of degradation in contrasting environments. Representative vegetation and the organic carbon (OC) rich soil/sediment fraction (humus fraction) were sampled at two depths (0–5 and 5–10 cm) in three plots along a transect covering an upland forest soil, a partially submerged sediment at the land–water interface and a constantly submerged sediment. The analysis of plant (lipds, isoprenoids, methoxyphenols and carbohydrates) and possible lignite (alkyl napththalenes, alkyl benzenes and PAHs) biomarkers released after pyrolysis supports previous findings in the area using other proxies. It was possible to discern OM sources in soil/sediment humus fractions, both from the substrate (lignite) as well as from the prevailing vegetation of the area. Environmental conditions in the submerged sediment seem to favour OM protection and the accumulation of decomposing plant material, whereas more intense OM degradation seems to prevail in the land–water interface areas characterized by fluctuating water level. In addition, a well resolved series of organic sulfur compounds (OSCS) found in the submerged sediments of rehabilitated acid lakes, indicates the possible occurrence of particular mechanisms of C preservation in this extreme anoxic S rich environment, i.e. via sulphur “quenching” with plant derived lipids during early diagenesis.  相似文献   

10.
Direct exploration of subglacial lakes buried deep under the Antarctic Ice Sheet has yet to be achieved. However, at retreating margins of the ice sheet, there are a number of locations where former subglacial lakes are emerging from under the ice but remain perennially ice covered. One of these lakes, Hodgson Lake (72°00.549′S, 068°27.708′W) has emerged from under more than 297–465 m of glacial ice during the last few thousand years. This paper presents data from a multidisciplinary investigation of the palaeolimnology of this lake through a study of a 3.8 m sediment core extracted at a depth of 93.4 m below the ice surface. The core was dated using a combination of radiocarbon, optically stimulated luminescence, and relative palaeomagnetic intensity dating incorporated into a chronological model. Stratigraphic analyses included magnetic susceptibility, clast provenance, organic content, carbonate composition, siliceous microfossils, isotope and biogeochemical markers. Based on the chronological model we provisionally assign a well-defined magnetic polarity reversal event at ca 165 cm in the lake sediments to the Mono Lake excursion (ca 30–34 ka), whilst OSL measurements suggest that material incorporated into the basal sediments might date to 93 ± 9 ka. Four stratigraphic zones (A–D) were identified in the sedimentological data. The chronological model suggests that zones A–C were deposited between Marine Isotope Stages 5–2 and zone A during Stage 1, the Holocene. The palaeolimnological record tracks changes in the subglacial depositional environment linked principally to changing glacier dynamics and mass transport and indirectly to climate change. The sediment composition in zones A–C consists of fine-grained sediments together with sands, gravels and small clasts. There is no evidence of overriding glaciers being in contact with the bed reworking the stratigraphy or removing this sediment. This suggests that the lake existed in a subglacial cavity beneath overriding LGM ice. In zone D there is a transition to finer grained sediments characteristic of lower energy delivery coupled with a minor increase in the organic content attributed either to increases in allochthonous organic material being delivered from the deglaciating catchment, a minor increase in within-lake production or to an analytical artefact associated with an increase in the clay fraction. Evidence of biological activity is sparse. Total organic carbon varies from 0.2 to 0.6%, and cannot be unequivocally linked to in situ biological activity as comparisons of δ13C and C/N values with local reference data suggest that much of it is derived from the incorporation of carbon in catchment soils and gravels and possibly old CO2 in meteoric ice. We use the data from this study to provide guidelines for the study of deep continental subglacial lakes including establishing sediment geochronologies, determining the extent to which subglacial sediments might provide a record of glaciological and environmental change and a brief review of methods to use in the search for life.  相似文献   

11.
Sediment cores were sampled from Xiamen Western Bay at five sites during the summer and winter of 2006 and Hg–Au microelectrodes were used to make on board measurements of the concentration gradients of dissolved oxygen, Mn2+, and Fe2+ within the sediments. The O2 concentrations decreased sharply from about 200 μmol L−1 in the bottom seawater to zero within a depth of a few millimeters into the sediment. Dissolved Mn2+ was detected below the oxic zones with peak concentrations up to 600 μmol L−1, whereas dissolved Fe2+ had peak concentrations up to 1,000 μmol L−1 in deeper layers. The elemental contents of organic carbon and nitrogen within the sediments were analyzed and their C/N ratios were in the range of 9.0 to 10.1, indicative of heavy terrestrial origin. Sediments from two sites near municipal wastewater discharge outlets had higher organic contents than those from the other sites. These high organic contents corresponded to shallow O2 penetration depths, high dissolved Mn2+ and Fe2+ concentrations, and negative redox potentials within the sediments. This indicated that the high organic matter content had promoted microbial respiration within the sediments. Overall, the organic content did not show any appreciable decrease with increasing sediment depths, so a quadratic polynomial function was used to fit the curve of O2 profiles within the sediments. Based on the O2 profiles, O2 fluxes across the seawater and sediment interface were estimated to be in the range 6.07 to 14.9 mmol m−2 day−1, and organic carbon consumption rates within the surface sediments were estimated to be in the range 3.3 to 20.8 mgC cm−3 a−1. The case demonstrated that biogeochemistry within the sediments of the bay was very sensitive to human activities such as sewage discharge.  相似文献   

12.
The biomarker composition and stable isotope (C, O) ratio values of organic matter (OM) and carbonate from sediment cores from the oligotrophic Lake Brienz and the eutrophic Lake Lugano (both in Switzerland) are compared, in order to obtain information about OM sources and transformation processes. Eutrophic conditions at Lake Lugano are reflected in elevated total organic carbon (TOC) content and hydrogen index (HI) values, as well as higher lipid concentrations. Parallel down core trends in δ13C values of TOC and calcite in the Lake Lugano sediments reflect bioproductivity cycles. Variations in δ18O values of calcite are consistent with changes in mean summer temperature over the time interval covered by the core. In contrast, such a correlation does not exist for Lake Brienz and there the stable isotope composition of calcite reflects its allochthonous origin. In the sediments of both lakes, fatty acid (FA) distributions and the composition of n-alkanols and n-alkanes indicate highly variable proportions of autochthonous OM sources (algae, zooplankton, bacteria) and OM from land plants. Enhanced in situ microbial synthesis during sediment deposition in Lake Lugano is suggested by the higher TOC-normalised concentrations of branched chain FAs (C15–C17), hopanoic acids and triterpenoid alcohols (i.e. tetrahymanol, diplopterol). Variations in the concentrations of cholesterol are related to contributions from zooplankton and/or green algae, while sitosterol concentrations reflect the input of vascular plants. Periods of increased input of OM from diatoms are evidenced by high 24-methylcholesta-5,22-dien-3β-ol (either epibrassicasterol or brassicasterol) and/or highly branched isoprenoid (HBI) alkenes concentrations. High relative concentrations of diplopterol in Lake Lugano sediments are consistent with the predominance of cyanobacteria commonly observed in eutrophic lakes. The presence of archeol and hydroxyarcheol in very low concentrations in the Lugano sediments argues for the activity of methanogens and/or anaerobic methanotrophs.Differences in OM degradation processes are reflected in higher chlorin index values in the Brienz sediments but higher saturated vs. unsaturated n-FAs in the core from Lugano. Higher concentrations of branched chain FAs and 16:1ω7 n-FA, as well as enhanced 18:1ω7/18:1ω9 n-FA, are consistent with enhanced bacterial biomass in the Lugano water column or sediments. The preservation of phytol seems to be enhanced in sediments with a high relative contribution of land plant OM. Major factors affecting OM accumulation in the lakes are differences in OM sources (i.e. terrestrial OM vs. autochthonous production), extent of bacterial activity and most likely oxygen availability in the water column.  相似文献   

13.
Vertical distribution patterns of organic geochemical constituents and the enzymes aminopeptidase and β-glucosidase provide insights about the nature and reactivity of sediment organic matter in the sandy sediments of two shallow “South Texas” estuaries. Sediment total organic carbon (TOC) δ13C values indicated that the organic matter (OM) was derived more from a mixture of seagrass and phytoplankton than from terrigenous OM. Down-core amounts of TOC and total nitrogen (TN) were <0.2% of dry weight, respectively. Enzyme activities were highest near surface and ranged from 25 to 1 μM/h for aminopeptidase as compared to 5 to 0.2 μM/h for glucosidase. In Aransas Bay, aminopeptidase activity correlated with sediment TN content (r s = 0.30) and β-glucosidase with TOC content (r s = 0.27). In Copano Bay, aminopeptidase correlated with TOC, TN, and carbohydrate content (r s = 0.89, 0.90, and 0.83, respectively). Variations of glucosidase activity also related positively to TOC, TN, and total carbohydrate content (r s = 0.68, 0.77, and 0.48, respectively). Overall, enzyme activities in these low OM, sandy sediments resembled those for other benthic marine environments.  相似文献   

14.
Two boreholes and ten piezometers in the Ganges flood plain were drilled and installed for collecting As-rich sediments and groundwater. Groundwater samples from the Ganges flood plain were collected for the analysis of cations (Ca2+, Mg2+, K+, Na+), anions (Cl−, NO3 −, SO4 2−), total organic carbon (TOC), and trace elements (As, Mn, Fe, Sr, Se, Ni, Co, Cu, Mo, Sb, Pb). X-ray powder diffraction was performed to characterize the major mineral contents of aquifer sediments and X-ray fluorescence (XRF) to analyze the major chemical composition of alluvial sediments. Results of XRF analysis clearly show that fine-grained sediments contain higher amounts of trace element because of their high surface area for adsorption. Relative fluorescence index (15–38 QSU) of humic substance in groundwater was measured using spectrofluorometer, the results revealed that groundwater in the Ganges flood plain contains less organic matter (OM). Arsenic concentration in water ranges from 2.8 to 170 μg/L (mean 50 μg/L) in the Ganges flood plain. Arsenic content in sediments ranges from 2.1 to 14 mg/kg (mean 4.58 mg/kg) in the flood plains. TOC ranges from 0.49 to 3.53 g/kg (mean 1.64 g/kg) in the Ganges flood plain. Arsenic is positively correlated with TOC (R 2 = 0.55) in sediments of this plain. Humic substances were extracted from the sediments from the Ganges flood plain. Fourier transform infrared analysis of the sediments revealed that the plain contains less humic substances. The source of organic carbon was assigned from δ13C values obtained using elemental analysis-isotope ratio mass spectrometry (EA-IRMS); the values (−10 to −29.44‰) strongly support the hypothesis that the OM of the Ganges flood plain is of terrestrial origin.  相似文献   

15.
太湖东部湖湾水生植物生长区底泥氮磷污染特征   总被引：6，自引：0，他引：6  
向速林  朱梦圆  朱广伟  许海 《沉积学报》2014,32(6):1083-1088
为了解太湖东部湖湾(贡湖湾、光福湾、渔洋湾)表层底泥中氮、磷的污染特征及其与水生植物生长的关系,采集了各湖湾滨岸带水生植物生长区的表层底泥,探讨了水生植物的生长与分布对表层底泥中总氮(TN)、总磷(TP)及总有机碳(TOC)等含量的影响,并对表层底泥进行营养评价.结果表明,水生植物生长密集区底泥中TN、TP、TOC的含量均显著低于水生植物零星生长区,说明水生植物的生长对太湖东部湖湾表层底泥中营养盐与有机碳含量具有较为明显的影响;相关性分析显示,表层底泥中TOC与TN含量呈显著相关性(R2=0.832 8),而与TP的相关性则较弱(R2=0.166 5),反映了TOC在湖泊底泥中的沉积可能成为湖泊氮的重要来源,而对磷的影响较小.利用有机指数与有机氮指数两种方法分别对东部各湖湾底泥进行污染评价,贡湖湾、光福湾、渔洋湾底泥有机指数平均值分别为0.142 7、0.228 6与0.208 6,均属较清洁与尚清洁水平,而各湖湾有机氮指数平均值均为Ⅲ与Ⅳ级,说明底泥已遭受了一定程度的氮污染.因此,对水生植物零星生长区表层底泥中氮含量的控制与削减有利于湖泊富营养化的预防与治理.  相似文献   

16.
《Applied Geochemistry》2006,21(1):48-57
Core samples of boreal terrestrial sediments from depths of 0–300 cm at Rikubetsu, Hokkaido, Japan were analyzed for alkaline and acid phosphatase enzymatic activities. Enzymatic activities of alkaline phosphatase (ALP) and acid phosphatase (ACP) were greatest at the surface and decreased with depth; ALP and ACP activities were 25.5 and 22.0 nmol min−1 g−1, respectively, within the top 5 cm. These biological indicators were compared with measurements of microbial cell density and chemical indicators, including total organic C (TOC) and total hydrolyzed amino acids (THAA). The product–moment correlation coefficients (r) for ALP and ACP versus microbial cell density were 0.949 and 0.810, respectively. The coefficients for THAA and TOC versus ALP were 0.997 and 0.995, respectively. Vertical distributions of enzymatic activity are highly consistent with the observed microbial biomass profile and diagenetic organic matter in the sediment. However, the vertical profile of PO4 concentration shows a negative correlation coefficient for ALP and ACP of −0.937 and −0.855, respectively. Consequently, ALP and ACP were shown to be useful biomarkers of microbial activities in the terrestrial sediment over the past 10 ka at Rikubetsu, Hokkaido, Japan.  相似文献   

17.
The distribution and nature of sedimentary organic matter (OM) have been examined in sediment cores collected from the lower reaches, including estuary, of the Godavari River in order to understand sedimentation patterns, sources, and diagenesis of OM. The samples were analyzed for organic carbon (Corg), total nitrogen, amino acids and hexosamines. The observed irregular trends in Corg distribution with depth indicate the unstable nature of bed sediment in the lower reaches of the river. Yet, in the lower estuarine region, regular trends in Corg distribution with depth reflect the deposition of sediment. The atomic ratio of Corg and total nitrogen (C/N; 10.5–16.1) also supported this observation. The distribution of amino acids and diagenetic indicators (β-ala+γ-aba mol.%, AA/HA and Glc-NH2/Gal-NH2) in individual cores revealed the post-depositional changes in the OM. In the core sediment from the lower reaches, there was no clear cut trend in amino acid content with depth. In the estuarine region, however, amino acid content was very low (50.5 and 186.5 μg g−1) in the upper layers compared to that in the lower layers (558.5 and 1099.3 μg g−1). Reactivity index (range 0.3–3.7) revealed that OM in the upper few centimeters, especially in the lower estuarine region, was more reactive relative to that in the deeper layers.  相似文献   

18.
Ammonium release from sediments has significant effects on the water quality in eutrophic lakes. In this study, the ammonium release kinetics and adsorption–desorption processes were investigated in 13 sediments of 6 shallow lakes from the middle and lower reaches of Yangtze River region, China. The results show that First Order Model best described the ammonium release process, the maximal release capacity had a strong correlation with organic matter (OM), cationic exchange capacity (CEC), total nitrogen (TN) and total phosphorus (TP). But it only had a weak correlation with Fe, Ca and Al. The ammonium release capacity in more polluted sediments was higher than that in less polluted sediments. The average release rate within 0–5 min was the highest among the experimental period, the amount released within 0–5 min accounted for approximately 50–70% of the total release capacity. The ammonium release rate had a significant and positive correlation with OM. But it did not have a strong correlation with TN, TP, Fe, Ca and Al. The ammonium potential release capacity (obtained when the water/sediment ratio was about 2,500) had strong and positive relation with OM and maximal release capacity, and it may provide useful information for the sediment release risk assessment. Henry Model best described the ammonium sorption isotherms, and ammonium adsorption–desorption equilibrium concentration can be considered as the ammonium release threshold to assess the release risk in the sediments.  相似文献   

19.
太湖及其主要入湖河流沉积磷形态分布研究   总被引：57，自引：6，他引：57  
选择了我国第三大浅水湖泊--太湖及其主要入湖河流进行沉积磷形态的连续提取研究.太湖湖区沉积磷中不稳态磷(LP)及铝结合态磷(Al-P)含量很低,其余形态磷为铁结合态磷(Fe-P)＜钙结合态磷(Ca-P)＜有机磷(Org-P).河流沉积物中有机磷的相对含量高于湖泊沉积物,绝对含量平均值约为湖泊沉积物的3.9倍,铁结合态磷的绝对含量约为湖泊沉积物的3/4,湖区沉积物Fe-P含量与水体中PO3-4-、Chla呈显著正相关关系,同时与间隙水的氧化性呈显著负相关关系.太湖各湖区沉积物的磷形态表现为空间差异较大,活性组分的差异性要大于活性较差的组分.总的来说北部湖区沉积物中Fe-P和Org-P含量高于其他湖区,这与太湖北部湖区水体高营养级和藻类爆发关系密切.湖区沉积磷的垂直分布规律较复杂,既有随深度增加的,也有随深度降低的,河流沉积物同样如此.这与太湖及河流生态条件、污染物排放以及沉积动力学条件不同有关.  相似文献   

20.
Aggregation of particulate organic matter (POM) and mineral grains may result in physical protection of organic matter (OM). To test this, phytoplankton cells of the dinoflagellate Scrippsiella trochoidea were inoculated with a natural bacterial assemblage and incubated with or without the clay montmorillonite. Within 5 h, aggregation of phytoplankton OM and clay resulted in transfer of the majority (∼80%) of OM into the >1.6 g cm−3 density fraction. Degradation of particulate organic carbon (POC), particulate nitrogen (PN), dissolved organic carbon (DOC), and dissolved and particulate total hydrolyzable amino acids (THAA), were modeled with a multi-G approach. Quantity of resistant OM was between two and four times larger during clay incubation relative to clay-free incubation. The two incubations did not exhibit significant differences in degradation state of particulate amino acids nor were there indications of preferential sorption of basic amino acids. The results suggest that a considerable fraction of phytoplankton OM can become resistant, at least on a timescale of weeks, mostly due to aggregation of POM and clay mineral grains.  相似文献   

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