Molecular weight and trace metal distributions in fulvic and humic acid fractions of coastal marine sediments

Molecular weight and trace metal distributions of fulvic and humic acid fractions of marine sediments from the Seto Inland Sea were investigated by using a gel filtration technique in combination with atomic absorption and emission spectrometries. A binary molecular weight distribution was found both in the fulvic acid fraction and in the humic acid fraction. The fulvic acid fractions with molecular weights of less than 1.5×10³ and of 5×10³?10⁴ accounted for 38–57 % and 25–41 % of the total fulvic acids, respectively, and the humic acid fractions with molecular weights of 10²?10⁴ and of over 2×10⁵ accounted for 58–73 % and 16–27 % of the total humic acids, respectively. The components with molecular weights of over 1.5×10³ contained 54 %, on average, of the Fe, Zn and Cu in the fulvic acid fraction, and the components with molecular weights of over 10⁴ contained 58 %, on average, of these metals in the humic acid fraction.     

Studies in seawater and lake water on interactions of trace metals with humic substances isolated from marine and estuarine sediments: I. Characterisation of humic substances

Two humic acids, HAL and HAN, isolated from marine sediments (Adriatic and Norwegian Sea) and humic (HAM) and fulvic (FAM) acids isolated from an estuarine sediment (Mahakam, Borneo) were characterized.The following characteristics: carbon content, hydrophobicity, degree of condensation and the content of aliphatic groups, are most pronounced for HAN, less pronounced for HAL and the least pronounced for HAM. The abundance of trace metals in the humic acids decreases in the following order: Al > Cu > Zn > Pb > Cd.Fulvic acid (FAM) has a lower carbon and a higher oxygen content than humic acids. It is hydrophilic and hardly any aliphatic groups were recorded. At pH 7 the predominant fraction of FAM has the apparent molecular weight of 20 000 daltons while the humic acids are of higher molecular weight.     

Characterization of humic and fulvic acids isolated from marine sediments of Sagami and Suruga Bays with C-13 and proton nuclear magnetic resonance

The C-13 and proton NMR spectra of marine humic and fulvic acids isolated from sediments of Sagami and Suruga Bays and Aldrich humic acid were obtained using pulse Fourier transform mode. The C-13 and proton NMR spectra, which clarified the differences in chemical characteristics among the various humic substances, showed that the marine humic acids had more aliphatic and less aromatic character than the Aldrich humic acid, and the marine fulvic acids had polysaccharide-like character. The C-13 NMR spectra of the marine humic substances, in particular, had many relatively well-resolved peaks with significant intensities, indicating the presence of variously bonded carbon atoms in them.     

Sedimentary humic substances in the northern Adriatic sea (Mediterranean sea)

Humic compounds were determined in sediments collected in an area of the Adriatic sea receiving fresh waters from the river Po. Sediment cores (10 cm) were sectioned into four layers which were analysed separately for redox potential (Eh), total phosphorus (TP), total organic carbon (TOC), humic (HA) and fulvic acid (FA) content. The structure of HA and FA was also investigated. The results showed that the TOC and TP content decreased from the coast to the open-sea stations. Humic and fulvic acid concentrations were also inversely correlated to the distance from the coast. Moreover, the humic and fulvic acids were closely correlated to the total organic content and to the total phosphorus content. The correlations found between humic substances (HS) and TOC and TP, respectively, could be explained both by an in situ formation due to the high content of nutrients and organic matter, and by a common source of HS, TOC and TP, namely the River Po discharge. The predominant presence of aliphatic carbon in the humic structures, the low degree of substitution and the high nitrogen content suggest that primarily humified compounds were formed in situ. Nevertheless, the River Po can act both as supplier of organic matter of which decomposition products lead to the formation of humic compound and as carrier of humified compounds.     

Chemical characterization of humic substances isolated from mangrove swamp sediments: The Qinglan area of Hainan Island,China

In order to improve the understanding of structural and reactive features of sediment organic matter from mangrove swamp as well as evaluate the relationship between such features and the impact from different sources (marine and terrestrial), humic and fulvic acids were isolated from two mangrove swamp sediments located in the Qinglan harbors on Hainan Island, China. One is a forest surface sediment site (WWM2), and the other is an estuary subaqueous sediment site (BMW). The humic and fulvic acids were characterized and compared using chemical and spectroscopic methods, including elemental analysis, thermogravimetric analysis (TGA), Fourier Transformed Infrared Spectroscopy (FTIR), ¹³C nuclear magnetic resonance (¹³C NMR) and potentiometric titrations. The results indicated that there were less aliphatic compounds but more aromatic compounds and oxygen-containing functional groups in fulvic acids. Humic acids contained more long-chain hydrocarbons and nitrogen compounds. Comparison of the C/N ratios and δ¹³C values for the humic substances at both sites indicated a larger marine and/or microbial contribution to the BMW site. Humic substances at the WWM2 site have more acidic functional groups than those of the BMW site. Compared to the literature, more phenolic groups existed in the samples of both sites, which may be due to the autochthonous contribution of mangrove plants.     

The occurrence of high molecular weight humic material in recent organic-rich sediment from the Namibian shelf

The molecular size distribution of humic substances has been investigated in two recent sediment samples of different ages taken from a single core sample collected off Walvis Bay, south-west Africa. Extractable humic acids were found to be by far the major form of organic carbon in both sediments, the near-surface younger sample containing predominantly high molecular weight (>100 000 molecular weight) humic acids and little fulvic acids whilst the deeper, older sample contained relatively less humic acid and relatively more fulvic acid of a range of molecular weights. A significant age difference was found between the >300 000 molecular weight and the <30 000 molecular weight fractions of the near-surface sample, the lower molecular weight fraction being older than the higher molecular weight fraction.The data suggest that in this rapidly accumulating, organic-rich sediment the first step en route from the planktonic matter to the humic complexes is direct and rapid incorporation of the biogenic material into high molecular weight humic acids.     

A study of the formation of high molecular weight compounds during the decomposition of a field diatom population

This work has investigated the possible formation of humic and fulvic acids, particularly high molecular weight moieties, in degrading diatom debris. The diatom debris was collected, freshly sedimented, from a well characterized natural field diatom population and allowed to degrade under conditions similar to those found at the sediment-water interface of many marine, organic-rich sediments.Samples of the detritus and overlying water were taken regularly over a period of 4 months and analysed for the presence of humic compounds. In the case of the detrital material, a sequential series of extractions were used. Molecular weight fractionation of the extracted humic material was carried out using Diaflow Ultrafiltration Membranes and two different fractionation methods have been compared. It appears that the choice of method may have an important effect on the determined distribution of the humic material, particularly when humic acid concentrations are low.High molecular weight (> 300 000- > 100 000) humic and fulvic acids were found in all the detrital samples, the content increasing with the period of decomposition. No evidence of any humic material was found in extracts of the living diatoms, the conclusion being that this material had been formed in situ during the degradation of the diatom debris. Most (65–90%) of the humic material was extracted from the detritus using a mild 0·05 m NaOH extraction at room temperature. Fulvic acids comprised approximately 90% of the total 0·05 m NaOH extraction, being composed mainly of either low molecular weight compounds (40–50% < 10000) or high molecular weight compounds (38–48% > 100000). Levels of humic acids were much lower and included a wide range of molecular weight fractions.The relevance of these findings to the possible origin of humic material in certain marine sediments is discussed.     

HUMIC SUBSTANCES IN SEDIMENTS

In this paper the chemical characteristics of humic substances (humic acid and fulvic acid) from East China Sea surficial sediment are studied through combination of chemical and physical methods. Results show that humic acids have less aromatic hydrocarbon and more alkane structure.The contents of amino acids from hydrolyzate of humic substances are different. The amount of various amino acids (such as acidic, neutral or basic amino aicd) of fulvic acid is higher than that of humic acid. The distribution order of amino acid abundance in various kinds of sediments is neutral amino acid>aromatic amino acid> basic amino acid.In addition, mathematical statistic method is also used to study their distribution. All samples show similar regularities, i. e., the contents of glycine, alanine, aspartic and glutamic are very high and those of cystine and methionine are very low or even disappear.The above results further confirm that humic acid and fulvic acid have similar composition and structure.     

Carbohydrates in humic and fulvic acids from Hiroshima Bay sediments

A core of 75 cm length from Hiroshima Bay, Seto Inland Sea in Japan, has been analyzed for the carbohydrate content of the humic and fulvic acids. These carbohydrates were found by gel filtration to be in the high molecular weight range. Carbohydrates were more abundant in fulvic acids than in humic acids. A comparison of carbohydrates in humic acids with those in fulvic acids showed that the former did not undergo diagenetic loss any faster than the latter. Identification of most alditol acetate in monosaccharides is based on the comparison of gas chromatographic retention indices and mass spectrometric fragmentation with those of authentic standard compounds. However, the compositional differences between carbohydrates in humic and fulvic acids were greater in the top section of 0–20 cm than in the 50–70 cm section. The processes which produce the humic-acid carbohydrates are operative either prior to or shortly after deposition.     

Studies in seawater and lake water on interactions of trace metals with humic substances isolated from marine and estuarine sediments: II. Voltammetric investigations on trace metal complex formation in the dissolved phase

In seawater and lake water the complexation of several heavy metals, present in the dissolved state at relevant trace levels, with humic substances isolated from two marine and an estuarine sediment has been studied by differential pulse anodic stripping voltammetry (DPASV) at a hanging mercury drop electrode (HMDE). Taking Zn(II) as an example, the aim of this study was to gain direct information on the general level of importance of humic substances for the speciation of certain heavy metals in fresh and saline waters.In seawater humic acids originating from different sediments have very similar complexing properties for Zn(II), decreasing slightly in the order HAN > HAL > HAM. In lake water HAL is most efficient for complexing Zn(II), followed by HAN and HAM.In both types of natural waters, the sedimentary fulvic acid is less efficient in complexing Zn(II) than the respective humic acid from the same site. In general, the complexing efficiency decreases in the order EDTA > NTA > humic acids > fulvic acid.The problem of humic acid adsorption at the electrode, which somewhat limits the investigation of Pb(II) and Cd(II), and the impact of pH on the amount of complexed Zn(II) are also discussed.The findings provide further direct evidence for the conclusion previously drawn from existing complexation data that because of the rather low levels of dissolved humics in large parts of the oceans, the complexation efficiency of humics for Cd, Pb and Zn is too low to affect the speciation pattern of these three heavy metals.     

Distribution of oxygen-containing functional groups and elements in humic acids from marine sediments

The elemental composition and oxygen-containing functional groups contents in the marine humic acids from the five sediment samples from Sagami Bay and Suruga Bay were determined. Kumada's method of classification of soil humic acids was applied to the marine humic acids. The carbon, nitrogen, hydrogen, oxygen and sulfur contents of the marine humic acids were, on average, 52.96, 5.12, 5.79, 34.99 and 1.13%, respectively, without wide variation. In comparison with terrestrial humic acids, the marine ones had relatively lower carbon content and higher hydrogen and nitrogen contents. It is suggested that the marine humic acids have more aliphatic and less aromatic character, as expected from their possible origins, e.g., phytoplankton. The total acidity, carboxyl, phenolic and alcoholic hydroxyl, carbonyl and methoxyl group contents in the marine humic acids were, on average, 5.80, 3.27, 2.53, 2.53, 3.09 and 0.41 milliequivalents per gram of dry ash-free humic acid (me g^–1), respectively. From quantitative data on the elemental composition and functional groups of the average marine humic acid, its empirical formula was calculated to be C₁₀₇H₁₃₈O₂₀(COOH)₉(OH)₇ ^phenolic (OH)₇ ^alcoholic (CO)₉(OCH)₃N₁₀S. The marine humic acids were similar to the so-called B type of soil humic acids with regard to the distribution of functional groups and spectroscopic properties.     

Comparison of the structures of humic acids from marine sediments and degraded field diatoms by 13C- and 1H-NMR spectroscopy

Humic acids isolated from marine sediments of the Peru continental shelf and from a degraded field diatom population dominated by the diatoms Skeletonema costatum, Nitzschia seviata and Thalassiosira sp. were characterized on the basis of infrared spectra and ¹³C- and proton-NMR spectra. Aliphatic structures were found to constitute the major fraction of humic acids and they appear to be highly branched. Carbohydrates and to a lesser extent aromatic materials, carbonyl-, ether-, alcohol- and amino groups are important contributors to the structure of marine humic acids. A close relationship was observed between the chemical structure of the sedimentary humic acid and the plankton humic acid.     

Interactions of marine plankton with transuranic elements. II. Influence of dissolved organic compounds on americium and plutonium accumulation in a diatom

To assess the significance of naturally occurring dissolved organic matter (DOM) on complexation of transuranic elements in seawater, a series of bioassay experiments was conducted in which the effect of DOM on the accumulation of ²⁴¹ Am, ²³⁷Pu (III–IV), and ²³⁷Pu (V–VI) by the marine diatom Thalassiosira pseudonana was measured. EDTA at 0.3μM complexed both metals substantially, resulting in reduced radio-isotope uptake by the diatom; the greatest effect was on Pu (III–IV). In contrast, there was no apparent complexation of either element by equimolar concentrations of marine fulvic (MFA) or humic acids (MHA), naturally occurring photooxidizable DOM (uncharacterized), or diatom exudates, as none of these materials reduced isotope uptake; on the contrary, there were indications that some of this DOM enhanced transuranic bioaccumulation in the diatom slightly. Subsequent experiments showed this enhancement was probably due to complexation of transition metals by the DOM, leading to fewer ambient ions ‘competing’ for binding sites on the cells; ²⁴¹ Am uptake rates were negatively correlated (r =? 0.846, P < .01) with Σ ASV-labile Cu + Zn + Cd + Pb. These experiments suggest that naturally occurring DOM may not appreciably complex Am or Pu or greatly affect their bioavailability in the sea.     

Chemical forms of chromium in natural water

The interaction of chromium (III) with humic substances obtained from pond sediment was experimentally studied using electrophoresis combined with ultrafiltration. The results show that within the neutral pH range chromium (III) in the presence of humic substances and some organic acids forms uncharged and/or negatively charged organic complexes of various molecular weights. A part of the chromium(III)-humic or -fulvic acid complexes having a negative charge was of lower molecular weight. Chromium (III) spiked in fresh water exists as various soluble anionic and/or uncharged species, and the molecular weights of these anionic complexes correspond to those of chromium(III)-humic and -fulvic complexes. These complexes may remain as stable dissolved forms for 10 days. The significance of the occurrence of chromium(III)-organic complexes in natural water in the geochemical cycle of chromium in the hydrosphere is discussed.     

冲绳海槽沉积物干酪根特征

本文采用元素分析、镜下观察、红外光谱、扫描电镜和热解分析等技术,分析了冲绳海槽柱状样中腐植酸、富里酸和干酪根的化学、物理特征,并探讨了它们之间的成因关系和干酪根类型。沉积物的产烃能力甚差,每吨沉积物仅能生成0.49～1.18kg烃类物质。     

Carbohydrates in humic and fulvic acids from sediments of Suo sound, Japan

Vertical distributions of carbohydrates in humic and fulvic acids isolated from coastal sediments in Suo sound were investigated by gas chromatography and Sephadex gel chromatography. Humate carbohydrates were composed of fulvic acid carbohydrates (70 to 95%). Apparent molecular weight distribution of fulvic acid carbohydrates in vertical direction of sediments was 3·5 to 7·4% below molecular weight (M.W.) 1000, 32 to 42% for M.W. 1000 to 5000, 7·4 to 24% for M.W. 5000 to 10 000, 11·5 to 15·5% for M.W. 10 000 to 25 000, and 28 to 34% for M.W. over 25 000, respectively. Humic acid carbohydrates are present in high molecular weight over 25 000. Fulvic acid carbohydrates decreased with increasing depth. A decrease of humate carbohydrates occurred between the surface layers to 20 cm depth, below 20 cm vertical change of carbohydrates was not observed.     

Dynamics of the Organic Matter Content of Bottom Sediments along the Razdolnaya River–Amur Bay Boundary (Sea of Japan)

Oceanology - The contents of Corg, humiс acids (HA), and fulvic acids (FA) in soil and riverine and marine bottom sediments have been investigated along a transect between the Razdolnaya...     

Humic substances in estuarine soils colonized by Spartina maritima

This study characterizes humic substances (HS) from two soils colonized by Spartina maritima at different physiographical positions in estuarine environments on the north-western coast of the Iberian Peninsula: the Villaviciosa site, a stand close to the main tidal channel, and the Ortigueira site, located in the low salt marsh. Humic and fulvic acids were extracted from the soils and characterized qualitatively by the following spectroscopic techniques: Fourier transform infrared spectroscopy, fluorescence spectroscopy and solid-state ¹³C nuclear magnetic resonance.The characterized HS showed a predominance of low humified compounds with a high proportion of aliphatic components and a low degree of aromaticity. The HS composition differed substantially between sites. In the Villaviciosa soil, the large amount of nonpolar aliphatic components and the very low degree of aromaticity may indicate a significant contribution of marine organic matter and/or microbial material to the HS. However, in the HS from the Ortigueira soil, the higher proportion of polysaccharides together with the presence of lignin-derived compounds may indicate greater inputs of vascular plant material. The δ¹³C isotopic composition of the bulk soils highlights the large input of Spartina maritima debris to the Ortigueira site, whereas in the Villaviciosa site, organic contributions from this C4 vascular plant were not so evident.The results indicate that in these soils colonized by Spartina maritima, physiographical position has an important effect on the composition of soil HS and, therefore, must be considered in the study of organic matter characteristics in such estuarine environments.     

环境因子对菲在黄河口沉积物上吸附的影响

为研究多环芳烃从河口到近海的环境归趋行为与生态风险,考察了沉积物质量浓度、溶解性有机质、温度、盐度4种典型环境因子对菲在黄河口沉积物上吸附的影响,比较了黄河口与近海两种沉积物对菲的吸附性能。研究结果表明,沉积物质量浓度越低,单位质量颗粒物的菲吸附量越高;共存的溶解性有机质对菲的吸附具有增促作用,且腐殖酸比黄腐酸的作用更显著;温度的升高不利于菲的吸附,而盐度的增加有利于菲的吸附。菲在沉积物上的吸附是分配作用与表面吸附两种行为的耦合,其中黄河口沉积物以表面吸附为主,而近海沉积物以分配作用为主。近海沉积物菲吸附量显著高于黄河口沉积物菲吸附量。基于此,菲从河口到近海的迁移过程中,更易于在沉积物表面发生吸附沉降,从而可能降低水相中的生态危害,但对近海底栖生物具有潜在的健康生态风险。     

海洋浮游植物分解和代谢产物中高分子有机物的紫外、红外和~1H-核磁共振光谱特征

用GDX 102树脂从海洋浮游植物三角褐指藻(Phaeodactylum tricornutum)的分解产物和代谢产物中分离提取腐植类物质(DHS,EHS)及乙醇可溶物(DES,EES),用~1H-NMR,IR和UV光谱进行结构分析,并同海水中腐植质(HS)和乙醇可溶物(ES)做了比较。结果表明,DHS,EHS和HS都以高支链烷烃、碳水化合物和氨基酸结构为主要组分,另有少量芳烃和杂环化合物。它们的化学结构很相似,说明DHS和EHS是海水腐植质的重要来源。