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824 Ergebnisse:

Trophic transfer of nano-TiO2 in a paddy microcosm: A comparison of single-dose versus sequential multi-dose exposures.
Environmental pollution (Barking, Essex : 1987) (2016)
Jung In Kim, Hyung-Geun Park, Kwang-Hyeon Chang, D H Nam, Min-Kyeong Yeo

In the present study, replicated paddy microcosm systems were used to investigate the environmental fate and trophic transfer of titanium nanoparticles (NPs) over a period of 14 days. Most TiO2 NPs immediately settled down in the sediment, and high accumulations of nano TiO2 in the sandy loam sediment and biofilm were observed. The test organisms (quillworts, water dropworts, duckweeds, biofilms, river snails, and Chinese muddy loaches) and environmental media (freshwater, sandy loam sediment) were exposed to sequential low doses (2 mg/L at 1 h, 4 days, and 9 days) or a single high-dose (6 mg/L) of TiO2 NPs. The bioconcentration factors (BCFs) of nano-TiO2 in biofilms, quillworts, duckweeds, and Chinese muddy loaches were higher in the sequential multi-dose group than in the single-dose group. Chinese muddy loaches showed higher bioaccumulation factors (BAFs) over their prey than river snails. The difference in the carbon isotope ratios between Chinese muddy loaches and river snails was less than 2‰, and an approximately 4‰ difference in the stable nitrogen isotope ratio was observed in the two aquatic predators from their major prey (e.g., biofilms or particulate organic matter). The trophic levels between biofilms and river snails and between biofilms and Chinese muddy loaches were 2.8 and 2.4 levels, respectively. These results indicate that these two predators consumed biofilm and other alternative preys at a higher level than biofilm. Although the trophic transfer rates of TiO2 are generally low, relatively higher biomagnification factors (BMFs) were found in Chinese muddy loaches (0.04-0.05) than in river snails (0.01-0.02). These results suggest that TiO2 NPs show greater movement in the sediment than in the water and that TiO2 NPs can be retained through aquatic food chains more after a sequential low-dose exposure than after a single high-dose exposure.

Records of bulk organic matter and plant pigments in sediment of the “red-tide zone” adjacent to the Changjiang River estuary
Chinese Journal of Oceanology and Limnology (2016)
Zhenjun Kang, Rencheng Yu, Fanzhou Kong, Yunfeng Wang, Yan Gao, Jianhua Chen, Wei Guo, Mingjiang Zhou

Cultural eutrophication caused by nutrient over-enrichment in coastal waters will lead to a cascading set of ecosystem changes and deleterious ecological consequences, such as harmful algal blooms (HABs) and hypoxia. During the past two decades since the late 1990s, recurrent large-scale HABs (red tides) and an extensive hypoxic zone have been reported in the coastal waters adjacent to the Changjiang River estuary. To retrieve the history of eutrophication and its associated ecosystem changes, a sediment core was collected from the “red-tide zone” adjacent to the Changjiang River estuary. The core was dated using the 210Pb radioisotope and examined for multiple proxies, including organic carbon (OC), total nitrogen (TN), stable isotopes of C and N, and plant pigments. An apparent up-core increase of OC content was observed after the 1970s, accompanied by a rapid increase of TN. The concurrent enrichment of δ13C and increase of the C/N ratio suggested the accumulation of organic matter derived from marine primary production during this stage. The accumulation of OC after the 1970s well reflected the significant increase of primary production in the red-tide zone and probably the intensification of hypoxia as well. Plant pigments, including chlorophyll a, β-carotene, and diatoxanthin, showed similar patterns of variation to OC throughout the core, which further confirmed the important contribution of microalgae, particularly diatoms, to the deposited organic matter. Based on the variant profiles of the pigments representative of different microalgal groups, the potential changes of the phytoplankton community since the 1970s were discussed.
Schlagworte: C , N , ec , oc , po , EA

A microbial carbonate response in synchrony with the end-Triassic mass extinction across the SW UK.
Scientific reports (2016)
Yadira Ibarra, Frank A Corsetti, Sarah E Greene, David J Bottjer

The eruption of the Central Atlantic Magmatic Province (CAMP)-the largest igneous province known-has been linked to the end-Triassic mass extinction event, however reconciling the response of the biosphere (at local and nonlocal scales) to potential CAMP-induced geochemical excursions has remained challenging. Here we present a combined sedimentary and biological response to an ecosystem collapse in Triassic-Jurassic strata of the southwest United Kingdom (SW UK) expressed as widely distributed carbonate microbialites and associated biogeochemical facies. The microbialites (1) occur at the same stratigraphic level as the mass extinction extinction, (2) host a negative isotope excursion in δ(13)Corg found in other successions around the world, and (3) co-occur with an acme of prasinophyte algae 'disaster taxa' also dominant in Triassic-Jurassic boundary strata of other European sections. Although the duration of microbialite deposition is uncertain, it is likely that they formed rapidly (perhaps fewer than ten thousand years), thus providing a high-resolution glimpse into the initial carbon isotopic perturbation coincident with the end-Triassic mass extinction. These findings indicate microbialites from the SW UK capture a nonlocal biosedimentary response to the cascading effects of massive volcanism and add to the current understanding of paleoecology in the aftermath of the end-Triassic extinction.

The carbon isotope and sequence stratigraphic record of the Sheinwoodian and lower Homerian stages (Silurian) of the Midland Platform, UK
Palaeogeography, Palaeoclimatology, Palaeoecology (2016)
Helen E. Hughes, David C. Ray

New high resolution δ13Ccarb isotope data are presented through the Sheinwoodian and lower Homerian stages of the Wenlock Series (Silurian) from sections in Shropshire, Herefordshire and the West Midlands (UK). This data identifies the well-known Early Sheinwoodian positive Carbon Isotope Excursion (ESCIE), the minor mid-ESCIE negative shift, and an Early Homerian positive Carbon Isotope Excursion (EHCIE) in the region of 1.4‰, as developed upon the Midland Platform and in close proximity to the Sheinwoodian and Homerian GSSPs. These carbon isotope excursions have been correlated against graptolite, conodont and chitinozoan frameworks from across the Midland Platform, and alongside details of sedimentology and faunas, have allowed for the establishment of a sequence stratigraphic framework. These integrated data sets reveal that the shallow-water Barr–Buildwas–Woolhope limestones reflect approximately synchronous deposition across the Midland Platform; in that they all contain the ESCIE and five widely traceable depositional cycles. Moreover, biostratigraphic and sequence stratigraphic frameworks from across the Midland Platform (Avalonia) confirm that both the ESCIE and the five cycles are synchronous with records from other palaeocontinents (Baltica and Laurentia) and indicate that the early Sheinwoodian graptolite zones as established in the type area are in need of review.

Root rather than leaf litter input drives soil carbon sequestration after afforestation on a marginal cropland
Forest Ecology and Management (2016)
Ya-Lin Hu, De-Hui Zeng, Xiang-Qing Ma, Scott X. Chang

Afforestation on croplands has been proposed as a means to mitigate the increasing emission of anthropogenic CO2. However, the relative contribution of above- and belowground litter input on soil organic carbon (SOC) sequestration following afforestation is not fully understood. We used a 270-day laboratory incubation experiment to examine the impact of litter type (i.e., leaf vs. fine root litter) of a poplar tree (Populus simonii Carr., C3 plant) on soil respiration and the turnover of new vs. old soil C in surface (0–10cm) and subsurface mineral soils (40–50cm) collected from a marginal cropland planted to maize (Zea mays L., C4 plant) in a semi-arid region in northeast China. Our results showed that fine root rather than leaf litter addition helps to sequester SOC even though soil microbial respiration rates were stimulated by both leaf and fine root litter input. Neither leaf nor fine root litter addition stimulated mineralization of old soil C across the two soil layers, but more new C was incorporated into the soil with fine root addition as compared with leaf litter addition. Moreover, the subsurface soil had greater potential to sequester SOC as compared to the surface soil. Our results suggest that root rather than leaf litter input drives soil carbon sequestration on the marginal soil, especially in the subsurface soil, and planting deep-rooted trees with large belowground biomass production could be used to increase SOC sequestration in marginal croplands.

Hydrological and Land Use Control of Watershed Exports of DOM in a Large Arid River Basin in Northwestern China
Journal of Geophysical Research: Biogeosciences (2016)
Yue Hu, YueHan Lu, Jennifer W Edmonds, Chuankun Liu, Sai Wang, Oindrila Das, Jie Liu, Chunmiao Zheng

We evaluated variation in dissolved organic matter (DOM) export as a function of hydrology and land use from a large arid river basin in northwestern China. Two soil-derived, humic-like (C1 and C2) and three protein-like fluorescence components (C3, C4, and C5) were identified. During high discharges, river water DOM had higher values of DOC concentration, percent humic fluorescence, and humification index, but lower values of fluorescence index and percent protein fluorescence than found at base flow, suggesting that flow paths shifted to shallower depths flushing out topsoil organic matter. Loading of DOC and soil-derived humic fluorescence were driven largely by discharge, with values over 10 times higher during high discharges than at base flow. Furthermore, both δ13C-DOC and C1 at high flows positively correlated with %agricultural lands within 1 km river buffers, demonstrating that near-river agricultural activities enhanced storm export of soil DOM. At base flow, C4 positively correlated with %agricultural lands, showing stimulation of aquatic bacterial carbon production as a result of elevated nutrient inputs from agricultural lands. Percent contributions of humic fluorescence in groundwater varied with well depths in shallow wells, but this pattern was not observed for deeper groundwater, suggesting that humic DOM could serve as a water source tracer indicating deeper aquifers were isolated from river water and shallow groundwater. Together, our data demonstrate that hydrology and land use controlled the sources and amount of riverine DOM in this large agricultural basin and that regulating storm runoff and near-river agricultural activities should be incorporated in ecosystem-based management of water resources.
Schlagworte: C , O , ge , GH

Two new oxygen-containing biomarkers isolated from the Chinese Maoming Oil Shale by silica gel column chromatography and preparative gas chromatography
Journal of Separation Science (2016)
Xiangyun Zhang, Hong Lu, Jing Liao, Caiming Tang, Guoying Sheng, Ping'an Peng

Two biomarkers, 5,9-dimethyl-6-isopropyl-2-decanone (1) and 4,9,11-trimethyl-6-isopropyl-2-dodecanone (2), were isolated from Chinese Maoming Oil Shale by silica gel column chromatography and preparative gas chromatography. Their structures were elucidated by using spectroscopic techniques.

An isotope (δ 34 S) filter and geolocator results constrain a dual feather isoscape (δ 2 H, δ 13 C) to identify the wintering grounds of North American Barn Swallows
The Auk (2016)
Keith A. Hobson, Kevin J. Kardynal

ABSTRACT The discovery of spatial patterns in naturally occurring isotopes (e.g., δ2H, δ13C) at continental scales has been tremendously important in providing a method to infer potential breeding and wintering origins of migratory animals through assignment to tissue-specific isoscapes. Single-isotope (i.e. δ2H) assignments of birds to molting origins in South America have been limited by the lack of strong spatial gradients in precipitation δ2H there. We integrated an mvnpdf (multivariate normal probability density function) approach using δ2H and δ13C values in tail feathers to determine wintering origins of adult Barn Swallows (Hirundo rustica) breeding in eastern Canada (n = 208). Spatial assignments were conducted using precipitation (δ2H) and theoretical plant-based (δ13C) isoscapes for South America calibrated for feathers of Nearctic–Neotropical migrant songbirds. We also measured feather δ34S values of Barn Swallows equipped with geolocators (n = 9) and of a larger group of Barn Swallows (n = 12...

Deforestation for oil palm alters the fundamental balance of the soil N cycle
Soil Biology and Biochemistry (2016)
R. Liz Hamilton, Mark Trimmer, Chris Bradley, Gilles Pinay

Expansion of commercial agriculture in equatorial regions has significant implications for regional nitrogen (N) budgets. Here we investigate changes in N availability and turnover in Southeast Asia following the replacement of tropical forest with oil palm plantations along a chronosequence of oil palm maturity (3-months to 15-year-old stands) and secondary to primary forest succession in Sabah, Malaysian Borneo. Ten sites were sampled during March and April 2012 and rates of gross ammonium (NH4+) and nitrate (NO3-) production (mineralisation and nitrification) and consumption (n = 8), potential denitrification and "anaerobic ammonium oxidation" ("anammox") (n = 12) were determined using 15N isotope additions to soil cores and slurries respectively. Gross mineralisation rates (0.05-3.08 g N m-2 d-1) remained unchanged in oil palm relative to forests. However, a significant reduction in gross nitrification (0.04-2.31 g N m-2 d-1) and an increase in NH4+ immobilisation disrupt the pathway to nitrogen gas (N2) production substantially reducing (by > 90%) rates of denitrification and "anammox" in recently planted oil palm relative to primary forest. Potential nitrous oxide (N2O) emissions were greater than potential N2 production and remained unchanged across the chronosequence indicating a potentially increased ratio of N2O:N2 emission when soils were first disturbed. These results are an important precursor to studies that could yield improved estimates of regional N turnover and loss in Southeast Asia which will have global implications for N biogeochemical cycling.

Total energy expenditure assessed by salivary doubly labelled water analysis and its relevance for short-term energy balance in humans.
Rapid communications in mass spectrometry : RCM (2016)
Stefano Guidotti, Berthe M A A A Verstappen-Dumoulin, Henk G Jansen, Anita T Aerts-Bijma, André A van Vliet, Anton J W Scheurink, Harro A J Meijer, Gertjan van Dijk

RATIONALE: The doubly labelled water (DLW) method is a stable isotopic technique for measuring total energy expenditure (TEE). Saliva is the easiest sampling fluid for assessing isotopic enrichments, but blood is considered superior because of its rapid exchange with body water. Therefore, we compared a large range of isotopic enrichments in saliva and blood, and related TEE in subjects with their ad libitum total energy intake (TEI). The relevance of these parameters to body weight and fat change over an 8-day interval was also assessed. METHODS: Thirty subjects underwent DLW analysis over either 8 or 14 days, during which time initial and final blood and saliva enrichments were compared. TEI was assessed by dieticians over the 8-day period only. Isotope ratio mass spectrometry was used for the measurement of δ(2) H and δ(18) O values. RESULTS: No discrepancies were observed between sampling fluids over a wide range of enrichments. During the 8-day period, average TEI exceeded TEE by ~5% or less. Using saliva as sampling fluid, TEI and TEI-TEE, but not TEE, were positively correlated to body weight change. TEI-TEE and physical activity EE (AEE), but not TEI, correlated, respectively, positively and negatively to changes in fat mass. CONCLUSIONS: The DLW method in humans can be reliably applied using saliva as sampling fluid. TEI-TEE as well as AEE contributes significantly to changes in fat mass over an 8-day period. Copyright © 2015 John Wiley & Sons, Ltd.
Schlagworte: H , O , med , GH