Distribution and alteration of amino acids in bulk DOM along a transect from bay to oceanic waters   总被引：2，自引：0，他引：2  

Youhei Yamashita  Eiichiro Tanoue 《Marine Chemistry》2003,82(3-4):145-160

A systematic survey of the concentrations and composition of total hydrolyzable amino acids (THAA) in bulk dissolved organic matter (DOM) was conducted at 11 stations along the 137°E transect from bay to oceanic areas in the northwestern Pacific. Concentrations of THAA and their contributions to dissolved organic carbon were high in the bay and coastal areas, declined toward the oceanic area and decreased with depth in the water columns. From the distribution patterns of the relative abundances of amino acids along the transect, individual amino acids were divided into four groups. One group included tyrosine, valine, isoleucine, phenylalanine, leucine and tryptophan, and was considered to represent easily degradable THAA, while glycine and alanine belonged to a more biorefractory group of THAA. Principal components analysis (PCA) was conducted to quantitatively differentiate patterns of amino acid composition. Amino acid groups based on PCA agreed with the groups classified by distribution patterns, indicating that first principal component scores reflected the degree of degradation of THAA in DOM, and were defined as a degradation index (DI). Two amino acids, glycine and alanine, increased in relative abundance with increasing DI, while valine, isoleucine, phenylalanine and leucine decreased with decreasing DI. The agreement indicated that the degradation process was the key factor controlling the quantity and quality of THAA in bulk DOM.  相似文献   

不同种群泥蚶肉营养成分的比较研究   总被引：24，自引：1，他引：24  

张永普  贾守菊  应雪萍 《海洋湖沼通报》2002,(2):33-38

本文对广西北海、浙江乐清湾和山东乳山湾的3个野生种群和2个养殖种群泥蚶肉的营养成分进行了比较研究，结果表明：同一地区野生种群干物质中中的可溶性糖、脂肪和灰分含量高于养殖种群，蛋白质、不饱和脂肪酸。不同野生种群水分含量和干物质中的蛋白质、脂肪、灰分、不饱和脂肪、高度不饱和脂肪酸、氨基酸总量及必需氨基酸的含量以广西野生种群最高，可溶性糖含量以乐清野生种群最高。  相似文献   

Tracing the inputs and fate of marine and terrigenous organic matter in Arctic Ocean sediments: A multivariate analysis of lipid biomarkers   总被引：4，自引：0，他引：4  

Mark B. Yunker  Laura L. Belicka  H. Rodger Harvey  Robie W. Macdonald 《Deep Sea Research Part II: Topical Studies in Oceanography》2005,52(24-26):3478

An understanding of the carbon cycle within arctic sediments requires discrimination between the terrigenous and marine components of organic carbon, insight into the removal mechanisms for labile carbon during burial and appreciation of shelf-to-basin processes. Using a large data set of multiple molecular organic markers (alkanes, alkanols, sterols, saturated and unsaturated fatty acids, dicarboxylic acids), we apply (1) principal components analysis (PCA) to obtain a robust comparison of biomarker compositions in Arctic Ocean sediments, (2) geometric mean (GM) linear regression of the PCA variables to estimate the relative contributions of labile/marine and stable/terrigenous sources to each biomarker and (3) the slope of the GM regression of each biomarker with TOC to provide a novel measure of the removal rate of each biomarker relative to phytol. The PCA- and TOC-based indices generally increase together: biomarkers with very high TOC-based removal rates such as the saturated and unsaturated n-alkanoic acids generally have a high labile/marine content from PCA, while the sterols have low removal rates, but exhibit a range of labile/marine content values and the n-alkanes and n-alkanols have low values for both. A dominant feature of all PCA models examined is a progressive decrease in the autochthonous/marine biomarkers with each increase in sediment core depth, which points to a universal diagenetic alteration of organic carbon with depth in the cores. The PCA model also displays a shelf to basin trend that is non-diagenetic and implies the ongoing (centuries or more) delivery of long-chain n-alkanes, n-alcohols and n-alkanoic acids in a matrix that is pre-formed and well-preserved within the sediments. Terrigenous biomarker distributions within the PCA model suggest that atmospheric transport of plant waxes in aerosols and the water borne transport of very fine plant macerals likely have significant roles in the export of these vascular plant biomarkers to the basins. Biomarker ratios and profiles of the PCA-based labile/marine content with core depth indicate that the PCA model is more strongly influenced by the biomarker lability than the marine content, while increases in the marine content are largely responsible for the shifts in composition for near-surface core sections.  相似文献   

葛氏长臂虾Palaemon gravieri磷脂成分的分析   总被引：1，自引：0，他引：1  

杨文鸽  娄永江  董明敏 《海洋科学》2001,25(7):45-46

对葛氏长臂虾的总脂和磷脂含量进行了测定，并对磷脂组分、总脂和磷脂肪酸组成进行了分析。结果表明：葛氏长臂虾的磷脂组分以PC和PE为主，磷脂含量为8．59‰-8.98‰，占总脂的33．76％－35．72％；与大豆和蛋黄的磷脂相比，葛氏长臂虾总脂和磷脂含有更多的PUFA，而虾磷脂中的脂肪酸不饱和度及EPA与DHA之和要高于其总脂。  相似文献   

Henry's law coefficients of formic and acetic acids     

Bryan J. Johnson  Eric A. Betterton  David Craig 《Journal of Atmospheric Chemistry》1996,24(2):113-119

The Henry's law constants, K _H, of dilute aqueous formic and acetic acids were determined experimentally as a function of concentration and temperature using a new counterflow packed-column technique. K _H was found to be (8.9±1.3)×10³ and (4.1±0.4)×10³ M atm^-1 at 25°C for HCOOH and CH₃COOH, respectively. The reaction enthalpies, H, were found to be –51±2 kJ mol^-1 and –52±1 kJ mol^-1 for formic and acetic acid, respectively. These are in good agreement with calculated thermochemical values.Whereas the K _H values are in reasonably good agreement with certain other experimentally determined values, K _H (HCOOH) is two to three times higher than calculated thermochemical values while K _H (CH₃COOH) is lower than the two calculated values.The best experimental values appear to be (11±2)×10³ M atm^-1 and (7±3)×10³ M atm^-1 for HCOOH and CH₃COOH, respectively.  相似文献   

Late Holocene environmental reconstruction using cave sediments from Belize     

Jason S. Polk  Philip E. van Beynen  Philip P. Reeder 《Quaternary Research》2007,68(1):53-63

Cave sediments collected from Reflection Cave on the Vaca Plateau, Belize show variations in the δ¹³C values of their fulvic acids (FAs), which indicate periods of vegetation change caused by climatic and Maya influences during the late Holocene. The δ¹³C values range from − 27.11‰ to − 21.52‰, a shift of ∼ 5.59‰, which suggests fluctuating contributions of C₃ and C₄ plants throughout the last 2.5 ka, with C₄ plant input reflecting periods of Maya agriculture. Maya activity in the study area occurred at different intensities from ∼ 2600 cal yr BP until ∼ 1500 cal yr BP, after which agricultural practices waned as the Maya depopulated the area. These changes in plant assemblages were in response to changes in available water resources, with increased aridity leading to the eventual abandonment of agricultural areas. The Ix Chel archaeological site, located in the study area, is a highland site that would have been among the first agricultural settlements to be affected during periods of aridity. During these periods, minimal water resources would have been available in this highly karstified, well-drained area, and supplemental groundwater extraction would have been difficult due to the extreme depth of the water table.  相似文献   

The high content of polyunsaturated fatty acids in Nannochloropsis limnetica (Eustigmatophyceae) and its implication for food web interactions, freshwater aquaculture and biotechnology     

Lothar Krienitz  Manfred Wirth 《Limnologica》2006,36(3):204-210

In the eustigmatophycean Nannochloropsis limnetica the content of polyunsaturated fatty acids (PUFA) is extremely high in comparison to different planktonic green algal taxa in freshwater ecosystems. The sums of n-6 and n-3 fatty acids in N. limnetica were ten-fold higher than in the other picoplankton Choricystis minor and Pseudodictyosphaerium jurisii, and higher than in the nanoplanktonic green algae Chlorella vulgaris, Monoraphidium neglectum and Scenedesmus obtusiusculus. The content of fatty acids in N. limnetica was highly variable under different culture conditions. The highest concentrations of PUFA in N. limnetica were found in non-aerated suspension cultures, with a high content of phosphate (40 mg l⁻¹ K₂HPO₄) in the culture medium: linoleic acid 22.19 mg g⁻¹ DW, arachidonic acid 10.52 mg g⁻¹ DW, and eicosapentaenoic acid 55.56 mg g⁻¹ DW. N. limnetica represent a high-quality food resource in freshwater food chains. Furthermore, cultures of this eustigmatophycean alga have a high potential for use in biotechnology and aquaculture.  相似文献   

The role and significance of extracellular polymers in activated sludge. Part I: Literature review     

Anna Raszka  Monika Chorvatova  Jiri Wanner 《洁净——土壤、空气、水》2006,34(5):411-424

In biological wastewater treatment, bacteria tend to aggregate by forming flocs, biofilms and even granules. A large part of the floc structure in activated sludge is composed of extracellular polymers. The extracellular polymeric substances (EPS) are mainly responsible for the structural and functional integrity of biofilms/flocs and they are considered to be important for the physico‐chemical properties of activated sludge. This review considers the composition of EPS and proportion between the constituents. Moreover it includes the relationship between the EPS constituents and sludge properties such as sludge retention time, hydrophobicity and surface charge.  相似文献   

Lipid biomarkers and carbon-isotopes of modern travertine deposits (Yellowstone National Park, USA): Implications for biogeochemical dynamics in hot-spring systems     

Chuanlun L. Zhang  Bruce W. Fouke  Aaron D. Peacock  Yongsong Huang 《Geochimica et cosmochimica acta》2004,68(15):3157-3169

Lipid biomarkers and ¹³C fractionation patterns were used to understand the dynamics of carbon cycling during microbial metabolisms in different environments of travertine precipitation (called facies) at Spring AT-1 on Angel Terrace in the Mammoth Hot Springs complex of Yellowstone National Park, USA. Microbial mats that encrust travertine deposits were collected for analyses of lipid biomarkers and carbon isotopes along the continuous drainage outflow system of Spring AT-1. The spring water exhibits a continuous temperature drop from 71°C in the vent at top to 24°C in the distal slope at bottom. Phospholipid fatty acids (PLFA) and glycolipid fatty acids (GLFA) exhibit distinctly different compositions in each of the facies, which are consistent with partitioning of the bacterial 16S rRNA gene sequences in the Spring AT-1 travertine facies (Fouke et al., 2003).The δ¹³C composition of total biomass within the microbial mats decreases from −16.1‰ in the vent to −23.5‰ in the distal slope. However, lower values occur in the pond (−26.0‰) and the proximal slope (−28.0‰) between the vent and the distal slope. Isotopic compositions of PLFA and GLFA have variations similar to those of total biomass. The average δ¹³C values of PLFA are −12.4 ± 5.2‰ (n = 10 individual fatty acids, same below) in the vent, −33.0 ± 3.1‰ (n = 11) in the pond, −33.7 ± 3.8‰ (n = 16) in the proximal slope, and −22.4 ± 3.4‰ (n = 10) in the distal slope; the average δ¹³C values of GLFA are −19.6 ± 3.0‰ (n = 3) in the vent, −30.4 ± 4.7‰ (n = 8) in the pond, −36.9 ± 2.8‰ (n = 12) in the proximal slope, and −27.9 ± 3.1‰ (n = 13) in the distal slope. In particular, fatty acids in the vent are enriched in ¹³C relative to the total biomass, which is consistent with the notion that the biosynthetic pathways of the extant microbial community in the vent may be dominated by Aquificales using the reversed tricarboxylic acid cycle. Fractionations between fatty acids and total biomass in the pond, the proximal slope and the distal slope suggest the involvement of other biosynthetic pathways for CO₂ fixation by extant microbial populations. The results indicate that lipid biomarkers provide valuable information on the changing diversity and activity of microbial communities in different depositional environments. Carbon-isotope fractionations, on the other hand, can provide insight into the operating biosynthetic pathways associated with different organisms in the changing environment. This integrated approach may serve as a powerful tool for identifying functional metabolism within a community and identify shifts in microbial community structure in modern hot-spring systems.  相似文献   

古里雅冰芯中生物有机酸的初步分析   总被引：9，自引：3，他引：6  

孙俊英  秦大河  姚檀栋  李忠勤 《冰川冻土》1998,(2)

甲酸、乙酸是全球对流层中普遍存在的化学成分,它们对偏远地区降水中的酸度有很大影响,降水中存在的甲酸、乙酸必然会在冰川和冰盖中保存下来．然而,目前很少有文章报道山地冰川中甲酸、乙酸的测定结果及环境意义．我们用离子色谱法测定了古里雅上部５ｍ冰芯中甲酸、乙酸的浓度,结果显示,甲酸、乙酸具有明显的季节变化,峰值一般对应于夏季层位,说明甲酸、乙酸的来源不同于阳离子,粉尘不是其主要来源．将甲酸、乙酸的记录与冰芯中δ１８Ｏ和阳离子的记录对比,得出甲酸具有较敏感的气候指示意义．  相似文献