Distributions of fatty acids in a stalagmite related to paleoclimate change at Qingjiang in Hubei,southern China

~~Distributions of fatty acids in a stalagmite related to paleoclimate change at Qingjiang in Hubei,southern China1. Dorale, J. A., Edward, R. L., Ito, E. et al., Climate and vegetation history of mid-continent from 75 to 25 ka: A speleothem record from Crevice Cave, Missouri, USA, Science, 1998, 282(5395): 1871-1874. 2. Li, B., Yuan, D., Qin, J. et al., Oxygen and carbon isotopic char- acteristics of rainwater, drip water and present speleofhems in a cave in Guilin area, and thei…     

Investigating the distribution and sources of organic matter in surface sediment of Coombabah Lake (Australia) using elemental,isotopic and fatty acid biomarkers

Extensive physical and biological measurements were made of the surface sediments within the shallow, semi-urbanised Coombabah Lake in southern Moreton Bay, Australia. Sediment bulk parameters (C/N ratios, δ¹³C and δ¹⁵N) and fatty acid biomarkers were used to determine distributions and sources of organic matter in the intertidal sediments. The determination of organic matter sources within coastal and estuarine settings is important in understanding the roles of organic matter as energy and nutrient sources. Spatial variability of biomarker values within the sediments were interpreted by thematic maps employing the Krigging algorithm. Grain size analysis indicated the lake was dominated by mud (<63 μm) in the southern (landward) and sand (>63 μm) in the northern (seaward) lake regions, respectively. Surface sediment organic C and N values ranged from 0.12% to 1.76% and 0.01% to 0.12% dry weight, respectively, and C/N ratios averaged 16.3±3.19%. Sedimentary δ¹³C values ranged from −26.1‰ to −20.9‰, with an average value of −23.9±1.0‰. Sedimentary δ¹⁵N values ranged from +1.7‰ to +4.8‰, with an average value of +2.8±0.8‰. Bulk sediment parameters suggested that sedimentary organic matter is provided predominantly by allochthonous sources in the form of fringing mangroves. Thirty-nine individual fatty acids were identified using gas chromatography–mass spectrometry. The mean contributions of long chain fatty acids (LCFAs), polyunsaturated fatty acids (PUFAs), saturated fatty acids (SAFAs) and bacterial fatty acids (BAFAs) were, respectively, 13.9±11.4%, 7.6±4.1%, 53.6±8.6% and 18.2±4.6% of the identified fatty acid methyl esters (FAMEs), with BAFAs occurring in all sampled sediments. Fatty acid compositions varied throughout lake sediments, which indicated spatial differences in autochthonous and allochthonous organic matter sources, including terrestrial and planktonic (i.e. zooplankton, diatoms and other algal species) sources. The contribution of organic matter from shoreline mangroves was confirmed by the presence of LCFAs and 18:2ω6 and 18:3ω3, which are markers for mangroves in this ecosystem. BAFAs were identified in increased proportions in sediments adjacent to urban developments and dominated by mud. Grain size was identified as a dominant factor in the fatty acid compositions and contributing values to FAME pool. Spatial patterns of C/N ratios, δ¹³C and δ¹⁵N values, and fatty acid biomarker contributions illustrated that there is a greater contribution of autochthonous and labile organic matter to the sedimentary organic matter pool in the northern (marine entrance) sediments compared to the more allochthonous sourced organic matter of the southern region of the lake. This study details the distribution and sources of organic matter within Coombabah Lake and illustrates the usefulness of a multiple biomarker approach in discriminating organic matter sources within estuarine environments.     

Chemical speciation of polycyclic aromatic hydrocarbons in sediments: Partitioning and extraction of humic substances

The primary objective of this study was to examine the chemical speciation of polycyclic aromatic hydrocarbons (PAHs) found in sediments endowed with different characteristics. To achieve this purpose and because the nature of the sediments influences the distribution of PAHs, we have analyzed four different types of sediments. To study the role of organic matter in the sequestration of PAHs, we fractionated humic substances into humic acids and humin-mineral fractions. After their separation and purification, the humic components were examined for their sorptive reactivity by extracting them with organic solvents; these extracts were subsequently subjected to GC/MS analysis. Our results show that PAHs are distributed between labile and sequestered fractions in sediments. A slower uptake of PAHs occurs when the sequestered fraction is formed, and this process can be prolonged and may be influenced by the characteristics if the sediment. Our study suggests that organic contaminants are available in muddy sediments for a longer period of time than in sandy sediments.     

Organic compounds in thermal water: The Mutnovskii area and the Uzon caldera

New data are reported relating to the presence and relative concentrations of organic compounds of medium volatility in samples from the water of hot springs and in the condensate of a steam–water mixture from wells drilled in the Mutnovskii geothermal area and from a well and springs in the Uzon caldera. The Mutnovskii area was found to contain 95 compounds belonging to 16 homologous series, with 71 compounds (12 series) in the Uzon caldera. Among these we found homologous series of biologically important compounds: carbonic acids, alcohols, ethers, aldehydes, ketones, and others. Evidence was obtained for a contribution of the abiogenic component in organic matter from sterile condensates of an overheated steam–water mixture from wells (alkanes, aromatic hydrocarbons, ketones, alcohols, and others) and in thermal water from natural discharges (in particular, alkanes and chlorine-containing hydrocarbons). The results of this study can be used for the preparation and conduction of laboratory experiments in prebiological chemistry under conditions that simulate a hydrothermal environment.     

Distribution and partitioning of polycyclic aromatic hydrocarbons (PAHs) in different size fractions in sediments from Boston Harbor, United States.

The concentrations of 16 US EPA priority pollutant polycyclic aromatic hydrocarbons (PAHs) were analyzed in four size fractions (< 62, 62-125, 125-250, and > 250 microm) in three contaminated Boston Harbor sediments. Total PAH concentrations ranged from 7.3 to 358 microg/g dry wt. and varied largely among the different size fractions in these sediments. For all three sites, the highest PAH concentrations were associated with the large size (> 250 microm) fractions while the fine silt and clay fractions (< 62 microm) contained relatively low PAHs. Despite the great concentration differences, the composition of PAHs in the four size fractions of these sediments showed similar patterns dominated by PAHs with three or more rings. By examining the distribution patterns of selected alkyl homologs to parent compounds, the results indicate that the major PAHs contributing to the high contamination in the inner harbor sediments were from pyrogenic sources. A positive correlation between PAHs and sedimentary organic carbon exists for all size fractions in the sediments. Calculated organic carbon normalized partition coefficients (log K(oc)) for selected major PAHs indicate near-equilibrium partitioning of PAHs among the different size fractions despite their large concentration variations. Sedimentary organic matter associated with different size fractions was the controlling factor for the observed distribution differences of PAHs among the size fractions. Our results also suggest that sedimentary organic matter with different origins and maturities may have somewhat different PAH sorption characteristics. Particulate organic matter of charcoal, plant detritus and Capitella fecal pellets in the sediments appear to sorb PAHs more strongly than organic matter associated with clay minerals. The strong association of PAHs with these organic particles in sediments will have a great influence not only on their distribution but also on long-term environmental impact.     

Carbon speciation and composition of natural microbial communities in polluted and pristine sediments of the Eastern Mediterranean Sea

Sediment samples collected from polluted (Augusta Bay) and pristine regions of the Eastern Mediterranean Sea (South Ionian Sea, Thracian Sea) were analyzed for black carbon, aliphatic hydrocarbons and phospholipid ester-linked fatty acids (PLFA). The aim of the study was to investigate the anthropogenic and biogenic inputs into the Eastern Mediterranean Sea and to evaluate the effects of refractory organic matter (e.g. black carbon) and the level of hydrocarbon contamination on benthic microbial community composition. Black carbon, generally considered to be chemically and biologically inert, comprised a significant but highly variable fraction of the sedimentary carbon pool in the analyzed sediments with a ratio to total organic carbon ranging from 0.02 to 0.66. Principal component analysis of the chemical characteristics of the sediments (organic carbon content, black carbon, bioavailable organic carbon, chlorophyll a, phaeopigments, aliphatic hydrocarbons) revealed clustering of samples along a gradient from the most productive and contaminated region of Augusta Bay to the carbon-poor and pristine sediments of the Thracian Sea. PLFA analysis revealed that gram-negative bacteria and microeukaryotes were most abundant in Augusta Bay and in the most impacted station of the Thracian Sea. The high levels of branched and odd-chain fatty acids recorded for these stations is probably linked to the elevated amounts of hydrocarbons at these stations; e.g. microbial communities may have developed the ability to degrade either naturally occurring aliphatic hydrocarbons or hydrocarbons derived from oil contamination.     

Origin of hydrocarbons in bottom sediments of the Ivankovo Reservoir

The composition of hydrocarbons (aliphatic and polycyclic aromatic) is studied in the surface layer of bottom sediments of the Ivankovo Reservoir. Their concentrations are found to be high both per dry mass and in the composition of C_org. The concentration range was 0.42 to 28.15% for C_org, 141.9 to 3451.8 μg/g for aliphatic hydrocarbons (0.2–51.2% C_org), and 28.2–9161 ng/g for polycyclic aromatic hydrocarbons ((0.04–6.58) × 10^?3 % C_org). The distribution of hydrocarbons is shown to be determined not only by the lithologic type of sediments, but also by their input from petroleum and pyrogenic sources.     

Organic matter in the Soultz HDR granitic thermal exchanger (France): natural tracer of fluid circulations between the basement and its sedimentary cover

Organic matter has been observed in cores of the Soultz-sous-Forêts granite (Alsace, France) at depths between 2158 and 2160 m, in a highly fractured and altered zone. The granite is overlain by a 1400-m-thick sedimentary cover containing petroleum (Pechelbronn oil field). The Soultz area is devoted to Hot Dry Rock geothermics thanks to a high geothermal gradient (up to 100 °C/km). During drilling operations, an artesian source produced oil in a fractured zone of the sedimentary cover (Buntsandstein). Its gas-chromatography and mass-spectrometry (GC-MS) analysis revealed the presence of normal alkanes (n-alkanes, i.e. linear hydrocarbons) centered on C₁₇, branched alkanes with a major C₁₉ peak, and few unsaturated hydrocarbons. The aromatic fraction is present in small amounts. In the Soultz granite, where it is altered, organic matter is exclusively associated with tosudite (interstratified clay mineral) which crystallized in plagioclase sites during a hydrothermal alteration episode. Organic matter has been later displaced and concentrated along veinlets in which illite and carbonates have crystallized during another hydrothermal alteration stage. The soluble organic matter analyzed by GC-MS is composed of aliphatic acids, n-alkanes with a bimodal C₁₈ and C₂₄-C₂₅ centered distribution, alkylbenzenes and aromatic acids. Organic compounds in the granite would either originate from a single source (immature sediments) or from two sources (immature sediments and migration of the Pechelbronn oil). No real evidence was found to prove which hypothesis is the best one. The presence of organic matter in the granite shows the importance of fluid flows between the sedimentary cover and the granitic basement through major fractures. In addition, the impregnation of plagioclase pseudomorphs with organic matter is made possible due to their high interconnection degree and to the intergranular microfracturation of the granite. The succession of several hydrothermal events with different physico-chemical characteris- tics may also be inferred from the occurrence of organic matter found in association with neoformed clay minerals in the granite.     

The recognition of biodegraded petroleum-derived aromatic hydrocarbons in recent marine sediments

Aromatic hydrocarbon fractions isolated from sediments polluted with crude oil, from sampling stations in and around Sullom Voe, Shetland Islands, were found to exhibit, as the major feature in their gas chromatograms, an unresolved complex mixture or ‘hump’. This feature was absent from the gas chromatograms of the aromatic hydrocarbon fractions isolated from corresponding unpolluted sediments in the region. The observed aromatic hump had little resemblance to the distribution of aromatic hydrocarbons in a typical North Sea crude oil. Incubation studies, however, showed that such a hump was appearing when oil-spiked sediments were aerobically biodegraded. From these incubation studies it was also evident that alkylaromatic hydrocarbons in the crude oil were biodegraded before any change in the normal alkanes was apparent. Therefore, the presence of an unresolved complex mixture in the gas chromatograms of aromatic hydrocarbon fractions from recent sediments can act as a marker to recognize contamination by crude oil.     

REE and (э)Nd of clay fractions in sediments from the eastern Pacific Ocean: Evidence for clay sources

Clay fractions in the non-calcareous surface sediments from the eastern Pacific were analyzed for clay minerals, REE and 143Nd/144Nd. Montmorillonite/illite ratio (M/I ratio), total REE contents ((REE), LREE/HREE ratio and cerium anomaly (бCe) may effectively indicate the genesis of clay minerals. Clay fractions with M/I ratio >1, бCe (0.85, (REE (400 μg/g, LREE/HREE ratio (4, and REE patterns similar to those of pelagic sediments are terrigenous and autogenetic mixed clay fractions and contain more autogenetic montmorillonite. Clay fractions with M/I ratio <1, бCe=0.86 to 1.5, ΣREE=200 to 350 μg/g, LREE/HREE ratio (6 and REE distribution patterns similar to that of China loess are identified as terrigenous clay fraction. The 143Nd/144Nd ratios or (э)Nd values of clay fractions inherit the features of terrigenous sources of clay minerals. Clay fractions are divided into 4 types according to (э)Nd values. Terrigenous clay minerals of type I with the (э)Nd values of -8 to -6 originate mainly from North American fluvial deposits. Those of type II with the (э)Nd values of -9 to -7 are mainly from the East Asia and North American fluvial deposits. Those of type III with (э)Nd values of -6 to -3 could come from the central and eastern Pacific volcanic islands. Those of type IV with (э)Nd values of -13 to -12 may be from East Asia eolian. The terrigenous and autogenetic mixed clay fractions show patchy distributions, indicating that there are volcanic or hot-spot activities in the eastern Pacific plate, while the terrigenous clay fractions cover a large part of the study area, proving that the terrigenous clay minerals are dominant in the eastern Pacific.     

Distribution and source differentiation of PAHs and PCBs among size and density fractions in contaminated harbor sediment particles and their implications in toxicological assessment

Sediment samples collected from Kaohsiung Harbor (Taiwan) were analyzed for 15 priority polycyclic aromatic hydrocarbons (PAHs) and 118 individual polychlorinated biphenyl (PCB) congeners in various particle size fractions and two density fractions. The PAHs in the low density fraction were a much more sensitive and effective indicator of the PAH source than those in the sediment as a whole. Hierarchical cluster analysis of PAH analytes in the low density sediments revealed significant differences in compositional patterns between locations and among size fractions. In the sediment samples from both study sites, the low density fraction particles had up to 155 and 150 times higher concentrations of PAHs and PCBs, respectively, than those in the corresponding high density fractions. In addition, the total toxic benzo[a]pyrene and 2,3,7,8-tetrachlorodibenzodioxin (TCDD, dioxin) equivalents in the sediment low density fractions were much higher (up to 170 and 273 times, respectively) than the corresponding high density fractions.     

Assessment of water and bottom sediment conditions in the bights of Koz’mina and Lake Vtoroe (Nakhodka Gulf,Peter the Great Bay,the Sea of Japan)

The state of the water area in the Bays of Koz’mina and Lake Vtoroe (Nakhodka Gulf is evaluated. The data given include water temperature and salinity, biochemical oxygen demand, pH, alkalinity, chlorophyll a, organic matter, biogenic elements, oil products, detergents, polycyclic aromatic hydrocarbons, phenols, and organochlorine pesticides in water and bottom sediments. Pollutants may enter the system of bights from both onshore sources and the open part of the bay. The water and bottom sediments in this part of the bay show higher values of BOD5 and the concentrations of oil products, polycyclic aromatic hydrocarbons, phenols, and organochlorine pesticides. The anthropogenic load on the water body is shown to increase because of the new industrial construction on its shore.     

Chemical forms of heavy metal contaminants in sediments of Miyun reservoir

The chemical forms, spatial distribution and sources of As, Hg, Cd, Pb and Zn in sediments of the Miyun reservoir were studied. The results of sequential extraction demonstrate that most of As, Pb and Zn were bound to the residual fraction, Hg was associated with the sulfide fraction while Cd was associated with the carbonate fraction and the residual fraction. On the vertical profiles the concentrations of the heavy metals in total and each fractions mostly decreased with increasing depths in sediments, suggesting that the heavy metals input from the upstream watershed increases yearly. Summation of the residual fraction, the sulfide fraction and the carbonate fraction accounts for 60.03%―85.60% of the total heavy metal contents in the sediments, which represent the geochemical background values of the elements and relate closely to soil erosion. Results of the main factor analysis show that most sediments of the reservoir come from the upstream soil erosion, the point source pollution and domestic waste. Moreover, the microbial activities taking place on the sediment-water interface are also one of the major factors to cause the increasing content of the organic matter fraction and the iron-manganese oxide fraction. Environmental change of the reservoir water could make the removability of the heavy metals increase, leading to the increase of their concentrations in pore water in sediments, and imperiling water quality of the reservoir.     

Assessment of polycyclic aromatic hydrocarbon input to urban wetlands in relation to adjacent land use

The relationship between polycyclic aromatic hydrocarbons (PAHs) in wetland surface sediments and adjacent land use was assessed in the Elizabeth River, VA, an urbanized sub-estuary of the Chesapeake Bay. Significant differences (p<0.05) in surface sediment PAH concentration between sites indicated adjacent land use had a substantial influence on PAH concentration in wetland sediments. Wetlands adjacent to parking lots and petroleum industrial sites exhibited the highest PAH concentrations of all wetlands examined. Overall, commercial land uses had the highest PAH concentrations and automotive sources dominated (52-69%) PAH input to wetland surface sediments irrespective of adjacent land use.     

Methane levels in shallow subtropical lake sediments: Dependence on the trophic status of the lake and allochthonous input

The vertical sediment profiles (10 cm) of the margins of three shallow subtropical lakes (Rio Grande, Brazil) with different trophic states and surrounding areas were evaluated to identify the effects of the allochthonous input on the methane concentration in the sediment. Sediment cores were collected to quantify the organic matter content (OM) and total carbon (TC), total nitrogen (TN), total phosphorous (TP) and methane (CH₄) concentrations.The three lakes were distinguished according to the trophic status and classified as oligotrophic, dystrophic and eutrophic. The natural characteristics of the dystrophic and eutrophic lakes have been changed due to the allochthonous input of leaves and twigs (Eucalyptus sp.) and the excreta of birds, respectively. In the eutrophic lake, the allochthonous input contributed to high autochthonous production. The highest values of OM, TC, TN and TP were found in the superficial sediments of the dystrophic and eutrophic lakes. The accumulation of allochthonous organic matter in the littoral zone promoted changes in the vertical sediment profiles and contributed to increases in the CH₄ concentrations in the sediment.     

Effects of watershed land use on sources and nutritional value of particulate organic matter in temperate headwater streams

Suspended particulate organic matter (POM) in headwater streams is an important source of food and energy to stream food webs. In order to determine the effects of watershed land use on the sources and characteristics of POM, we compared the lipid composition of POM (fatty acid, aliphatic alcohol and sterol) from streams influenced by different types of watershed land use. Eight first-order streams discharging to the York River Estuary (Virginia, USA) were sampled during baseflow conditions bi-monthly from February to November 2009, including streams draining forest-dominated, pasture-dominated, cropland-dominated, and urban land-dominated watersheds. Allochthonous vs. autochthonous lipids showed that POM in most of these streams was dominated by allochthonous sources (59.5 ± 14.2 vs. 39.6 ± 14.5 % for aliphatic alcohols and 52.9 ± 11.5 vs. 34.1 ± 10.3 % for sterols). The relative abundance of allochthonous vs. autochthonous lipid inputs to POM varied as a function of land use type. POM in streams draining forest-dominated watersheds contained a higher proportion of allochthonous lipids and a lower proportion of autochthonous lipids than the streams influenced by human land use. The contribution of bacterial fatty acids differed significantly among sampling times (P = 0.003), but not among land use types (P = 0.547). Stepwise linear regression model selected nitrate and temperature as the best predictors of variation in bacterial inputs to POM. Proxies used to assess the nutritional value of POM potentially available to stream consumers included C:N ratios, and the concentrations of total long-chain polyunsaturated fatty acids, eicosapentaenoic acid, arachidonic acid, and cholesterol. None of these nutritional proxies differed among sampling months (P ≥ 0.171), but the proxies showed that the nutritional value of POM in forest streams was lower than in urban streams. Collectively, these findings suggest that human land use in upstream watersheds alters the source composition and nutritional value of stream POM, which not only impacts food quality for stream biota, but also potentially changes the characteristics of OM reaching downstream ecosystems.     

An isotopic model for the origin of autochthonous organic matter contained in the bottom sediments of a reservoir

Geochemical analysis of surface sediment samples collected in 2005 and 2006 was used to evaluate the potential sources of the organic matter present in sediments of southeast Poland's Solina Reservoir.Statistical analysis of sediment variables(carbon to nitrogen ratio, and the carbon 13 and nitrogen 15 isotope ratios) determined for the organic fraction indicated significant spatial variability with respect to sources of organic matter. A binary mixing model was developed from literature sources to predict the relative contributions of allochthonous and autochthonous production to sediment organic matter.Autochthonous production was shown to account for 60-75% of bulk sedimentation in the lacustrine parts of the reservoir, near the dam. In contrast, autochthonous production accounted for only 25% of sedimentation in the riverine zone receiving stream inputs. Statistical analysis identified the δ~(15)N of organic matter as the best predictor of the source of organic matter. Multiple regression analysis indicated that two water-quality variables(nitrate and dissolved silica) were significantly related to the δ~(15)N signature of organic matter. This led to a conclusion that limnetic nitrate and dissolved silica concentrations were regulating organic matter production in the Solina Reservoir.     

Allochthonous subsidies of organic matter across a lake–river–fjord landscape in the Chilean Patagonia: Implications for marine zooplankton in inner fjord areas

Ecosystems can act as both sources and sinks of allochthonous nutrients and organic matter. In this sense, fjord ecosystems are a typical interface and buffer zone between freshwater systems, glaciated continents, and the coastal ocean. In order to evaluate the potential sources and composition of organic matter across fjord ecosystems, we characterized particulate organic matter along a lake–river–fjord corridor in the Chilean Patagonia using stable isotope (δ¹³C) and lipid (fatty acid composition) biomarker analyses. Furthermore, estimates of zooplankton carbon ingestion rates and measurements of δ¹³C and δ¹⁵N in zooplankton (copepods) were used to evaluate the implications of allochthonous subsidies for copepods inhabiting inner fjord areas. Our results showed that riverine freshwater flows contributed an important amount of dissolved silicon but, scarce nitrate and phosphate to the brackish surface layer of the fjord ecosystem. Isotopic signatures of particulate organic matter from lakes and rivers were distinct from their counterparts in oceanic influenced stations. Terrestrial allochthonous sources could support around 68–86% of the particulate organic carbon in the river plume and glacier melting areas, whereas fatty acid concentrations were maximal in the surface waters of the Pascua and Baker river plumes. Estimates of carbon ingestion rates and δ¹³C in copepods from the river plume areas indicated that terrestrial carbon could account for a significant percentage of the copepod body carbon (20–50%) during periods of food limitation. Particulate organic matter from the Pascua River showed a greater allochthonous contribution of terrigenous/vascular plant sources. Rivers may provide fjord ecosystems with allochthonous contributions from different sources because of the distinct vegetation coverage and land use along each river’s watershed. These observations have significant implications for the management of local riverine areas in the context of any human project that may modify terrestrial habitats as well as the productivity, food webs, and community structure of rivers, lakes, fjords, and the coastal ocean in the Chilean Patagonia.     

Extraterrestrial Organic Compounds in Meteorites

Many organic compounds or their precursorsfound in meteorites originated in the interstellar or circumstellarmedium and were later incorporated intoplanetesimals during the formation of thesolar system. There they either survivedintact or underwent further processing tosynthesize secondary products on themeteorite parent body.The most distinct feature of CI and CM carbonaceouschondrites, two typesof stony meteorites, is their high carbon content(up to 3% of weight), either in theform of carbonates or of organic compounds. The bulkof the organic carbon consistsof an insoluble macromolecular material with a complexstructure. Also present is asoluble organic fraction, which has been analyzedby several separation and analyticalprocedures. Low detection limits can be achievedby derivatization of the organicmolecules with reagents that allow for analysisby gas chromatography/massspectroscopy and high performance liquidchromatography. The CM meteoriteMurchison has been found to contain more than70 extraterrestrial amino acids andseveral other classes of compounds includingcarboxylic acids, hydroxy carboxylicacids, sulphonic and phosphonic acids, aliphatic,aromatic and polar hydrocarbons,fullerenes, heterocycles as well as carbonylcompounds, alcohols, amines and amides.The organic matter was found to be enriched indeuterium, and distinct organiccompounds show isotopic enrichments of carbon andnitrogen relative to terrestrialmatter.