Jens Hefter

Metabolites of xenobiotica and mineral oil constituents linked to macromolecular organic matter in polluted environments

Abstract The type of association between pollutants and humic substances of soils, sediments and river waters has been investigated. Metabolites, which can arise from the microbiological degradation of polyaromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB), were cleaved from the macromolecular matrix by selective chemical degradation techniques (OH − , BCl 3 , Rh/H 2 ). Hydrolysis reactions performed with Na 18 OH proved that some metabolites of pollutants form stable ester bonds by condensation processes with functional groups of humic substances, a phenomenon which has major implications for transport, toxicity and bioavailability of xenobiotica.

Organic pollutants associated with macromolecular soil organic matter: Mode of binding☆

A study of ether-linked moieties in macromolecular bound residues of polycyclic aromatic hydrocarbons (PAH) generated in bioremediation experiments was performed using high temperature hydrolysis degradation with subsequent analysis of the products by GC-MS. This hydrolysis reaction was specifically designed to cleave ether bonds including relatively stable diarylether structures. Among the reaction products, aromatic alcohols representing typical microbiologically derived metabolites of PAH were found in addition to natural compounds. Thus, parts of the bound residues appeared to be linked within the macromolecular material by ether bonds. Model experiments with an oxidoreductase enzyme and aromatic alcohols indicate the formation of these ether bonds to be an enzyme-catalysed process.

(-)-Verrucosan-2β-ol from the phototrophic bacterium Chloroflexus aurantiacus: first report of a verrucosane-type diterpenoid from a prokaryote

(-)-Verrucosan-2β-ol (C20H34O), a rare diterpene with a 3,6,6,5-tetracyclic ring system, has been isolated and identified for the first time from the phototrophic bacterium Chloroflexus aurantiacus. Furthermore, an unsaturated diterpenoid hydrocarbon (C20H32) with a similar carbon skeleton was found in the same organism. This prokaryote, naturally occurring in hot spring microbial mats, is considered to be one of the oldest bacterial life forms on earth. Verrucosane-type diterpenoids had previously been detected only in some liverworts (Hepaticae), forming a unique group in the plant kingdom.

Ethylene and methane in the upper water column of the subtropical Atlantic

The vertical distributions of ethylene and methane in the upper water column of the subtropical Atlantic were measured along a transect from Madeira to the Caribbean and compared with temperature, salinity, oxygen, nutrients, chlorophyll-a, and dissolved organic carbon (DOC).Methane concentrations between 41.6 and 60.7 nL L-1 were found in the upper 20 m of the water column giving a calculated average flux of methane into the atmosphere of 0.82 μg m-2 h-1. Methane profiles reveal several distinct maxima in the upper 500 m of the water column and short-time variations which are presumably partly related to the vertical migration of zooplankton.Ethylene concentrations in near surface waters varied in the range of 1.8 to 8.2 nL L-1. Calculated flux rates for ethylene into the atmosphere were in the range of 0.41 to 1.35 μg m-2 h-1 with a mean of 0.83 μg m-2 h-1. Maximum concentrations of up to 39.2 nL L-1 were detected directly below the pycnocline in the western Atlantic. The vertical distributions of ethylene generally showed one maximum at the pycnocline (about 100 m depth) where elevated concentrations of chlorophyll-a, dissolved oxygen, and nutrients were also found; no ethylene was detected below 270 m depth. This suggests that ethylene release is mainly related to one, probably phytoplankton associated, source, while for methane, enhanced net production occurs at various depth horizons. For surface waters, a simple correlation between ethylene and chlorophyll-a or DOC concentrations could not be observed. No considerable diurnal variation was observed for the distribution and concentration of ethylene in the upper water column.

Biomarker indications for microbial contribution to Recent and Late Jurassic carbonate deposits

SummaryBiomarker investigations were applied to the hydrocarbon fractions of three Recent (cyanobacterial mat, Lake Van microbialite and Lake Satonda microbialite) and two Late Jurassic carbonate samples obtained from sponge bioherms. The relative concentrations ofn-alkanes, monomethyl alkanes, acyclic isoprenoids, steroids and hopanoids in these samples are studied and their probable biological precursors are discussed. Normal alkanes with carbon chain lengths ranging from C15 to C34 and monomethyl alkanes ranging from C17 to C21 with a varying methyl branching pattern are found. The major hydrocarbons are low molecular weight (LMW)n-alkanes (C15–C21) with a slight to strong predominance ofn-heptadecane (C17). High molecular weight (HMW)n-alkanes occur in low to moderate relative concentrations showing a preference of odd-carbon numbered compounds with a maximum at C29. Within the acyclic isoprenoids, pristane, phytane/phytene, pentamethyl-eicosane, squalane and lycopane could be identified. Polycyclic terpenoids of the sterane and/or hopane type are present in all carbonate samples. The carbon numbers of these components range from 27 to 29 and 27 to 32, respectively. These organic compounds identified can be attributed to various source organisms such as cyanobacteria, archaebacteria, algae and vascular plants. All hydrocarbon fractions of the samples are characterized by moderate to high relative concentrations of compounds derived from cyanobacteria, signifying the role of these organisms as contributors to the Recent as well as to the Late Jurassic carbonate deposits.

Glacial‐to‐Holocene evolution of sea surface temperature and surface circulation in the subarctic northwest Pacific and the Western Bering Sea

It has been proposed that North Pacific sea surface temperature (SST) evolution was intimately linked to North Atlantic climate oscillations during the last glacial-interglacial transition. However, during the early deglaciation and the Last Glacial Maximum, the SST development in the subarctic northwest Pacific and the Bering Sea is poorly constrained as most existing deglacial SST records are based on alkenone paleothermometry, which is limited prior to 15 ka B.P. in the subarctic North Pacific realm. By applying the TEXL86 temperature proxy we obtain glacial-Holocene-SST records for the marginal northwest Pacific and the Western Bering Sea. Our TEXL86-based records and existing alkenone data suggest that during the past 15.5 ka, SSTs in the northwest Pacific and the Western Bering Sea closely followed millennial-scale climate fluctuations known from Greenland ice cores, indicating rapid atmospheric teleconnections with abrupt climate changes in the North Atlantic. Our SST reconstructions indicate that in the Western Bering Sea SSTs drop significantly during Heinrich Stadial 1 (HS1), similar to the known North Atlantic climate history. In contrast, progressively rising SST in the northwest Pacific is different to the North Atlantic climate development during HS1. Similarities between the northwest Pacific SST and climate records from the Gulf of Alaska point to a stronger influence of Alaskan Stream waters connecting the eastern and western basin of the North Pacific during this time. During the Holocene, dissimilar climate trends point to reduced influence of the Alaskan Stream in the northwest Pacific.

Dansgaard‐Oeschger forcing of sea surface temperature variability in the midlatitude North Atlantic between 500 and 400 ka (MIS 12)

Using a high-resolution record of alkenone-based sea surface temperatures (SSTs) from the midlatitude North Atlantic covering the period between 500 and 400 ka here we show that during Marine Isotope Stage (MIS) 12, SSTs in this region were characterized by numerous abrupt jumps in the order of 3–6°C, spaced every 3–4 ka. We argue that these abrupt warming events in the midlatitude North Atlantic reflect Dansgaard-Oeschger (D/O) events, which are corroborated by the correlation to the synthetic record of Greenland climate for this time period. These results demonstrate that during MIS 12 the direct influence of high-latitude climate was far larger than during the last glacial and reached all the way into the midlatitude North Atlantic. In addition the consistent temporal lag between surface water cooling and appearance of ice-rafted debris demonstrates that icebergs were not the cause for cooling in the North Atlantic at this time. We hypothesize that the extreme impact of D/O events during MIS 12 as recorded in our record must have had an imprint on global climate and will therefore be important to evaluate future high-resolution climate records or model efforts that cover this time period.

The Southern Westerlies During the Holocene: Paleoenvironmental Reconstructions from Chilean Lake, Fjord, and Ocean Margin Sediments Combined with Climate Modeling

This project aimed at investigating centennial to millennial-scale changes of the strength and position of the southern westerly wind belt (SWW) using multi-proxy paleoprecipitation and paleoceanographic records combined with transient model runs. The proxy data records reveal a distinct latitudinal anti-phasing of wind changes between the core and northern margin of the SWW over the Holocene. During the early Holocene, the SWW core was enhanced and the northern margin was reduced, whereas the opposite pattern is observed in the late Holocene. These Holocene changes resemble modern seasonal wind belt variations and can be best explained by varying sea-surface temperature fields in the eastern South Pacific. Transient modeling experiments from the mid- to late Holocene are not yet consistent with these proxy results. However, a good data-model agreement exists when investigating the potential impact of solar variability on the SWW at centennial time-scales during the latest Holocene with periods of lower (higher) solar activity causing equatorward (southward) shifts of the SWW.

n-Alkanoic Compounds in Sulphur-Rich Macromolecular Substances: A Detailed Investigation of Sulphur Incorporation and Cross-Linking

A selective stepwise chemical degradation technique is applied to investigate alkanoic structural subunits in sulphur-rich macromolecular fractions (resins, asphaltenes, kerogens). Emphasis is given to the sulphur speciation in terms of intermolecular (thioether, thiodiether) and intramolecular (thiolane, thiophene) linking of structural subunits. The degradation sequence comprises two steps: (I) a desulphurization and (II) an oxidation of aromatic moieties liberating alkyl substituents as mono-and dicarboxylic acids. In this study, nickel boride is used for the desulphurization. The efficiency of the reagent is compared to other desulphurization reagents (Raney nickel, nickelocene/LiAlH4). The use of deuteriated nickel boride allows to label the site of former sulphur functionalities with deuterium. The reagent is tested on a set of reference compounds to elucidate the deuteriation pattern of various sites and types of sulphur bonds (e. g. thioether, thiolane, thiophene). Ruthenium tetroxide is used to release alkanoic substituents of aromatic subunits.

Deglacial mobilization of pre-aged terrestrial carbon from degrading permafrost

The mobilization of glacial permafrost carbon during the last glacial–interglacial transition has been suggested by indirect evidence to be an additional and significant source of greenhouse gases to the atmosphere, especially at times of rapid sea-level rise. Here we present the first direct evidence for the release of ancient carbon from degrading permafrost in East Asia during the last 17 kyrs, using biomarkers and radiocarbon dating of terrigenous material found in two sediment cores from the Okhotsk Sea. Upscaling our results to the whole Arctic shelf area, we show by carbon cycle simulations that deglacial permafrost-carbon release through sea-level rise likely contributed significantly to the changes in atmospheric CO2 around 14.6 and 11.5 kyrs BP.Permafrost-derived carbon (C) may have been an additional source of greenhouse gases during the last glacial-interglacial transition. Here the authors show that ancient C from degrading permafrost was mobilised during phases of rapid sea-level rise, partially explaining changes in atmospheric CO2 and ∆14C.