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17001. 题目: Benthic nutrient cycling at the sediment-water interface in a lagoon fish farming system (northern Adriatic Sea, Italy)
文章编号: N18070504
期刊: Science of The Total Environment
作者: Elisa Petranich, Stefano Covelli, Alessandro Acquavita, Cinzia De Vittor, Jadran Faganeli, Marco Contin
更新时间: 2018-07-05
摘要: Metabolism and carbon, oxygen, and nutrient fluxes (DIC, DOC, DO2, NO2 , NO3 , NH4 +, PO4 3 and SiO4 4 ) were studied during three surveys at two sites (VN1 and VN3) located at a fish farm at the Marano and Grado Lagoon (northern Adriatic Sea), using an in situ benthic chamber. Field experiments were conducted in July and October 2015 and March 2016 at a depth of approximately 2 m along the main channels of the fish farm. Water samples were collected by a scuba diver every 2 h in order to investigate daily fluxes of solutes across the sediment-water interface (SWI). Regarding the solid phase, Corg/Ntot and Corg/Porg molar ratios suggested an autochthonous marine origin of the organic matter and a minor preservation of P in the sediments, respectively; high values of sulphur (Stot) were also encountered (0.8–2%). The conditions at VN3 were mostly anoxic with high NH4 + levels (30–1027 μM) and the absence of NO3 . Substantial daily patterns of all solutes occurred especially in autumn and winter. On the contrary, fluxes at VN1 were less pronounced. Usually, inverse correlations appeared between dissolved O2 and DIC trends, but in our system this was observed only at VN3 in autumn and accomplished by a parallel increase in NH4 +, PO4 3 and SiO4 4 during intense nutrient regeneration. These results are significantly different than those reported for open lagoon environments, where nutrient regeneration at the SWI and in surface sediments is the primary source of nutrients available for assimilation processes, especially during the warmer period of the year when the natural nutrient input by fresh water inflows is limited. Due to the importance of this site for aquaculture, biodiversity and ecosystem services, useful suggestions have been provided from this study in order to improve the quality of this unique aquatic system.

17002. 题目: Characterisation of dissolved organic matter using Fourier-transform ion cyclotron resonance mass spectrometry: Type-specific unique signatures and implications for reactivity
文章编号: N18070503
期刊: Science of The Total Environment
作者: Xi-Zhi Niu, Mourad Harir, Philippe Schmitt-Kopplin, Jean-Philippe Croué
更新时间: 2018-07-05
摘要: This study investigated the chemodiversity and unique signatures for dissolved organic matter (DOM) from different types of water using high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). Eight freshwater hydrophobic DOM (HPO) share 10–17% formulas that were mainly lignin-like compounds. Unique signatures were synthesized: unique to the high-humic HPO (Suwannee River and Blavet River) were condensed aromatic and some aliphatic compounds with H/C > 1.5 and O/C < 0.2, which is considered as decisive of these black river water. Medium-humic isolates (Loire River, Seine River, South Platte River, and Ribou Dam) did not show explicit unique signatures. Nonetheless, enhanced chemodiversity was observed for medium-humic isolates extracted from a variety of indigenous environmental conditions. As an example, South Platte River HPO isolated in winter showed signatures similar to low-humic HPO (Colorado River), i.e., predominantly aliphatic CHO (H/C > 1.0). Effluent HPO was mainly aliphatic molecules with 0.2 < O/C < 0.5 and enriched in S-bearing molecules, and molecules unique to glacial DOM (Pony Lake) incorporated N-bearing compounds that were inferiorly oxidized and were considered as microbial-derived. The weight-averaged double bond equivalent and elemental ratio derived from FTICR-MS were compared with SUVA254 and the results from elemental analysis. This acts as the first study to synthesize unique chemical compositions that distinguish different types of DOM and determine certain reactivity. It is also a significant reference for future studies using similar types of DOM.

17003. 题目: Culture and horticulture: Protecting soil quality in urban gardening
文章编号: N18070502
期刊: Science of The Total Environment
作者: Francesca Bretzel, Claudia Caudai, Eliana Tassi, Irene Rosellini, Manuele Scatena, Roberto Pini
更新时间: 2018-07-05
摘要: Urban cultivation for food production is of growing importance. The quality of urban soil can be improved by tillage and the incorporation of organic matter, or can be degraded by chemical treatments. Urban gardeners have a role in this process, through the selection of various cultivation techniques. Our study focuses on an allotment area in the town of Pisa (Italy), which since 1995 has been run as a municipal vegetable garden by the residents. We analysed the soil and compared the data with those collected five years previously, to verify the possible changes in soil properties and fertility. We also interviewed the gardeners regarding their backgrounds, motivations and cultivation practices. We looked for possible changes in the soil quality attributable to the cultivation techniques. We found that the allotment holders influenced the soil quality through the cultivation techniques. Organic carbon, electrical conductivity and the content of copper increased unevenly in relation to the gardeners' cultivation practices. At the same time the study highlights that the urban gardeners were not completely aware of how to protect and enhance the fertility and the quality of urban soil. We believe that town councils should be responsible for providing correct information to the allotment holders and thus prevent the possible misuse of urban soil to grow food, as this can affect everyone's health.

17004. 题目: Exposure of Brazilian soil and groundwater to pollution by coccidiostats and antimicrobial agents used as growth promoters
文章编号: N18070501
期刊: Science of The Total Environment
作者: Alejandro Yopasá-Arenas, Anne Hélène Fostier
更新时间: 2018-07-05
摘要: The World Health Organization has identified antimicrobial resistance as one of the most important threats to global health. Brazil is one of the world's leading meat producers and the Brazilian use of veterinary antimicrobials as therapeutic agents and prophylactic or growth promoters in animal production remains problematic. Many antimicrobials are not completely metabolized and their excretion represents a significant source of environmental exposure. The aim of this work was to estimate the exposure risk of soil and groundwater to pollution by growth promoters (GPs) and anticoccidial additives (AAs) in Brazil by using a method based on a geographical information system (GIS). The principle adopted is that the greater the amount of animals, the greater the quantity of antimicrobials present, and the greater the soil vulnerability to pollution. Our research showed that GPs and AAs are extensively used in the Brazilian animal production system. An analysis of market data showed that zinc bacitracin, monensin, salinomycin, colistin and tylosin are representative GPs and AAs. This study presents a qualitative approach for risk assessment based on worst-case scenarios. First, the probable environmental concentration was estimated using a correlation between the number of heads of the herds of poultry and cattle, and the amounts of drug released. The leaching risk potential was characterized for each compound, as proposed in ISO 15175. The potential of soil pollution was evaluated for each antimicrobial as a function of its binding and dissipation rates. These rates were calculated using georeferenced data of organic carbon, average temperature, water balance and hydro-geological parameters. The consequences were modeled based on Brazilian soil usage. Finally, the risk was calculated by combining the different maps generated using spatial multi-criteria decision analysis. Higher risk was found for the midwest, southeast and south regions of Brazil. Groundwater was found to be more vulnerable than soil.

17005. 题目: Environmental assessment concerning trace metals and ecological risks at Guanabara Bay, RJ, Brazil
文章编号: N18070402
期刊: Environmental Monitoring and Assessment
作者: Valquiria Maria de Carvalho Aguiar, Paula Ferreira Falheiro Abuchacra, José Ant?nio Baptista Neto, Allan Sandes de Oliveira
更新时间: 2018-07-04
摘要: Three-stage sequential extraction BCR was applied to surface sediments from the west part of Guanabara Bay to assess the mobility of Zn, Cu, Pb, Ni, Cr, and Mn. Results were satisfactory for the analysis of certificate standard material (BCR 701), with recoveries between 71 (Cu) and 123% (Cr). Evaluation of organic matter composition classified the area as eutrophic (CHO:PRT > 1), with aged organic detritus at some stations. Zn exhibited by far the greatest bioavailability, with 43.49% of its concentrations associated with the exchangeable fraction. Cu and Cr showed stronger affinity for organic matter, with 51.18 and 48.73% of their concentrations, respectively, bounded to the oxidizable fraction. Pb presented higher concentrations in the reducible fraction (45.41%). The strongest lithogenic contribution was shown by Ni (31.91%) and Mn (35.44%). PCA clearly showed the determinant role of organic matter and fine sediments in the distribution of metals in the study area and also a common source for these elements, with the exception of Cu. Risk Assessment Code (RAC) established Zn as the most concerning element in the study area. The decreasing mobility order, based on the sum of the three extractable fractions of BCR, was Pb > Cu > Cr > Zn > Ni > Mn. The comparison of the results with sediments quality guidelines (SQG) proved fractionation to be mandatory in the evaluation of effective ecological risk concerning trace elements in sediments.

17006. 题目: Soil quality of an Iranian forest ecosystem after conversion to various types of land use
文章编号: N18070401
期刊: Environmental Monitoring and Assessment
作者: M. H. Rasouli-Sadaghiani, M. Barin, S. Siavash Moghaddam, C. A. Damalas, K. Ghodrat
更新时间: 2018-07-04
摘要: The impact of land-use change on parameters of the soil was evaluated in soil samples from arable land, orchard land, and grassland in West Azerbaijan, Iran, compared with their adjacent natural forestland, using some biological indices. Microbial biomass carbon (MBC); microbial basal respiration (BR); metabolic quotient (qCO2); substrate induced respiration (SIR); carbon availability index (CAI); the microbial quotient, i.e., the ratio of microbial carbon to soil organic carbon (Cmic/Corg); and soil organic carbon (SOC) were calculated in collected soil samples. Deforestation and long-term land use showed adverse effects on soil biological properties. The spatial distribution of MBC, BR, SIR, and SOC, followed the order: forestland > grassland > orchard land > arable land. SOC showed the highest decline by 67.7% in arable land, 43.6% in orchard land, and 36.3% in grassland, with an average reduction of 49.2% compared with forestland. Similarly, BR and MBC decreased by an average reduction of 41.3 and 34.8%, respectively, compared with forestland. By contrast, the qCO2 index, the CAI index, and the Cmic/Corg ratio were not affected significantly by land use, except from a significant raise of the Cmic/Corg ratio in the arable land. Land-use change exerted a remarkable negative influence on soil quality with several soil attributes affected due to cropping compared with adjacent grassland and forestland. At the field level, proper management practices that increase SOC in the soil, e.g., effective recycling of crop residues and manures, should be considered, when land is continuously cultivated.

17007. 题目: Oceanic fronts control the distribution of dissolved barium in the Southern Ocean
文章编号: N18070319
期刊: Marine Chemistry
作者: Kimberley M. Pyle, Katharine R. Hendry, Robert M. Sherrell, Oliver Legge, Andrew J. Hind, Dorothee Bakker, Hugh Venables, Michael P. Meredith
更新时间: 2018-07-03
摘要: The globally-observed relationship between oceanic barium and the macronutrient silicic acid results from the shared influence of large-scale ocean circulation and mixing on the two elements, and the inherent link between barium and organic matter formation and dissolution. A detailed examination of deviations from barium-silicon correlations can reveal variations in non-conservative processes within the marine barium cycle. Here, we present a high-resolution dataset of dissolved barium and macronutrients from the Drake Passage and the Scotia and Weddell Seas. Our new results highlight the influence of Southern Ocean frontal zones on barium cycling and the deviations of barium and macronutrient distributions as a result of spatial variations in phytoplankton assemblages and in barite formation processes. These new data also reinforce findings that water mass mixing and ocean circulation, in particular the location of oxygen minima, play a key role in barium distribution. Our findings have implications for the use of sedimentary barium as a proxy for export production, which may be complicated by physical water circulation changes or shifts in plankton community structure.

17008. 题目: Branched GDGT variability in sediments and soils from catchments with marked temperature seasonality
文章编号: N18070318
期刊: Organic Geochemistry
作者: Min Cao, Gemma Rueda, Pedro Rivas-Ruiz, M? Carmen Trapote, Mona Henriksen, Teresa Vegas-Vilarrúbia, Antoni Rosell-Melé
更新时间: 2018-07-03
摘要: The distributions of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in sediments are used as a proxy measurement to infer changes in past mean annual air temperatures (MAT). When applied to high resolution sedimentary sequences, measurement of brGDGT distributions is employed to reconstruct MAT at subdecadal time scales. In addition, brGDGT proxy estimates are also sometimes purported to be seasonally biased in environments where annual brGDGT production may not be constant during a seasonal cycle. The main aim of this study was to assess the occurrence of seasonality in the production and distribution of brGDGTs and the seasonality bias of the derived temperature proxy. For this purpose, we examined brGDGT distributions and brGDGT-derived MAT estimates in surface soils and settling/suspended particulate matter over one year, from two sites located in the same latitude but at different altitudes, in the Catalan Pyrenees, as well as at one site in southern Norway. These locations have marked seasonal temperature cycles, which were expected to maximize the possibility of detecting any seasonal bias in the production and compositions of brGDGTs. The results show that brGDGT abundance is heterogeneous and increases with soil humidity. The brGDGT distributions and some of the brGDGT-derived proxy measurements in soils are relatively stable throughout the year and do not change significantly in the suspended particulate matter in the river or settling particulate matter in traps. Our study shows that the impact of the seasonality of temperature on brGDGT distribution was absent in the soils studied, regardless of altitude or latitude on a catchment/regional scale. As soils are likely to contain a brGDGT signature which is representative of average environmental conditions in the catchment at least over decades, brGDGT proxy reconstructions derived from soil sources are more suitable to infer variability in environmental parameters over the same timescales (i.e. decades or longer). On shorter timescales (i.e. annual), sediment downcore variability in brGDGTs is likely to be related to changes derived from in situ production and sediment sources.

17009. 题目: Sedimentary records of human activity and natural environmental evolution in sensitive ecosystems: A case study of a coral nature reserve in Dongshan Bay and a mangrove forest nature reserve in Zhangjiang River estuary, Southeast China
文章编号: N18070311
期刊: Organic Geochemistry
作者: Dongyi Li, Yonghang Xu, Yunhai Li, Jianjun Wang, Xijie Yin, Xiang Ye, Aijun Wang, Liang Wang
更新时间: 2018-07-03
摘要: Total organic carbon (TOC), total nitrogen (TN), δ13Corg, δ15N, and grain size were measured in two sediment cores from reserves adjacent to Dongshan Bay, China. The aims were to identify organic matter (OM) sources and to evaluate the combined impact of human activity and natural environmental processes over the last 100 yr. In a coral reserve far from the estuary of Zhangjiang River, the average sediment accumulation rate (SAR) was 0.51 cm/yr from ca. 1839–2015, and the values of δ13Corg and C/N (atomic ratio of TOC to total N) ranged from 21.9‰ to 23.7‰ and from 5.7 to 8.1, respectively. In a mangrove forest reserve near the estuary, SAR averaged 0.49 cm/yr from ca. 1891–1985 and 2.41 cm/yr from ca. 1985–2015, and the δ13Corg and C/N values ranged from 22.7‰ to 26.3‰ and from 9.3 to 21.7, respectively. By combining a comparison plot of C/N and δ13Corg and a binary mixing model (based on δ13Corg and Norg/Corg, respectively), the major OM sources were assigned and their sedimentary contributions estimated. The sedimentary OM in the coral reserve had mainly an offshore marine authigenic signature with an average terrigenous contribution of <27%. In the mangrove forest reserve, the sedimentary OM was a mixture of terrestrial and marine sources, with an average terrigenous contribution of >56%. While input from the Zhangjiang River declined from the 1980 s, urban development, deforestation and land reclamation contributed to an overall increase in the total mass accumulation rate (MAR). The coral was also severely damaged by the advent of poaching around the same time. These two factors collectively resulted in a rapid decrease in OM content and OC accumulation rate (CARorg ) of the sediments until the establishment of the coral reserve in 1997. Changes in terrain and climate and the construction of water conservancy facilities were traditionally the primary factors responsible for changes in the sedimentary environment of the mangrove forest reserve. Since the 1980s, however, the expansion of the mangrove forest along with human activity has led to rapid increases in MAR and CARorg ; while, protective measures and a favorable climate have also promoted the growth of the mangrove forest.

17010. 题目: The composition and radiolysis impact on aromatic hydrocarbons in sedimentary organic matter from the Mulga Rock (Australia) uranium deposit
文章编号: N18070310
期刊: Organic Geochemistry
作者: Paul F. Greenwood, Chao Shan, Alex I. Holman, Kliti Grice
更新时间: 2018-07-03
摘要: Our interest in the effect of ionizing radiation on sedimentary organic matter (OM) has extended to the molecular distributions and stable isotopic values of aromatic hydrocarbons. Thermally immature sediments (%Ro = 0.26; Tmax < 421 °C) spanning a 173–5280 ppm radiolytic gradient from the Mulga Rock Uranium Deposit (Western Australia) contained high abundances of vascular plant sourced aromatic (and aliphatic) terpenoids. Terpenoids with 2–5 rings and various levels of aromatisation were detected in the aromatic fractions of these sediments. The extent of aromatisation increased with sedimentary U/radiolytic levels, attributed to free-radical promoted reactions including dehydrogenation and oxidation of aliphatic precursors. The sediment with the highest U content (5280 ppm) showed only diterpenoids and low MW PAHs, reflecting complete radiolytic removal of higher MW terpenoids. A larger number and variety of terpenoid products were detected from the other sediments (U ≤ 1700 ppm) from which several radiolytically promoted reaction pathways were identified. Cadinene, for instance, was subject to competing hydrogenation and dehydrogenation reactions which gave cadinane and progressively aromatised diterpenoid analogues, respectively. Pentacyclic terpane precursors were also progressively aromatised and partially converted to des-A-triterpenoid or C-ring cleaved triterpenoid (tetracyclic) products. These reactions are typical of the natural diagenetic transformation of plant terpenoids, with the main effect of the high radiolytic levels an apparent hastening of diagenetic processes. The δ13C values of several aromatised products indicated a slight 13C enrichment with increasing aromatisation, likely due to preferential abstraction of H from 12C.

17011. 题目: Archaeal and bacterial glycerol dialkyl glycerol tetraether (GDGT) lipids in environmental samples by high temperature-gas chromatography with flame ionisation and time-of-flight mass spectrometry detection
文章编号: N18070309
期刊: Organic Geochemistry
作者: Sabine K. Lengger, Paul A. Sutton, Steven J. Rowland, Sarah J. Hurley, Ann Pearson, B. David A. Naafs, Xinyue Dang, Gordon N. Inglis, Richard D. Pancost
更新时间: 2018-07-03
摘要: Archaeal isoprenoidal glycerol dibiphytanyl glycerol tetraether lipids (iGDGTs) and their non-isoprenoidal branched bacterial analogues (brGDGTs) have widespread applications in biogeochemistry and paleothermometry. Analysis of GDGTs usually involves separation using high performance liquid chromatography, typically coupled via atmospheric pressure chemical ionisation to mass spectrometric detection in selected ion-monitoring mode (HPLC–APCI-MS). However, reliable determination of ratios and, in particular, quantification by this technique, can be challenging due to differences in ionisation efficiencies of the various compounds. Quantification of GDGTs also relies on external calibration of the relative response to an internal standard with authenticated GDGTs, which are often not readily accessible. Here, we tested the suitability of high temperature gas chromatography with flame ionisation detection (HTGC-FID) for the determination of concentrations and tetraether lipid-based ratios in marine and terrestrial samples. For this, we identified GDGTs in environmental samples using HTGC coupled to time-of-flight mass spectrometry (HTGC–MS). Using a purified GDGT standard, we show we can quantify GDGT-0 in environmental samples by GC-FID. Some GDGT-based ratios measured by HTGC-FID exhibited a linear correlation (1:1) with ratios derived from HPLC–MS and weight-based ratios of mixtures of purified standards. However, ratios relying on minor isomers, such as TEX86 and MBT/CBT have many unresolved challenges for determination by HTGC. Detection limits were higher than for HPLC–MS. However, the advantages of employing HTGC-based methods include: (1) the independence from MS tuning-related differences in ionisation energies; (2) the potential for direct comparison with other, non-GDGT based biomarkers; and (3) a more complete insight into biomarker distributions in environmental samples by the extension of the temperature range. Quantitative elution of GDGTs from a HTGC column as demonstrated herein, will also enable their analysis by compound-specific isotope ratio mass spectrometry.

17012. 题目: Assessment of apolar lipids in subseafloor rocks and potential contaminants from the Atlantis Massif (IODP Expedition 357)
文章编号: N18070308
期刊: Organic Geochemistry
作者: Katherine A. Hickok, Tran B. Nguyen, Susan Q. Lang
更新时间: 2018-07-03
摘要: International Ocean Discovery Program Expedition 357 drilled 17 boreholes across the Atlantis Massif with the goals of investigating carbon cycling and the presence of life in a zone of active serpentinization. The expedition recovered multiple lithologies including gabbros, basalts, carbonate sands, and serpentinites. A subset of contrasting lithologies were analyzed for apolar lipid content to determine if non-volatile organic molecules can be detected in the oceanic subsurface. The definitive detection and identification of abiotic and biological lipids in the subsurface of an actively serpentinizing system would be a significant step towards understanding a variety of scientific processes, including the evolution of pre-biotic chemistry, microbial habitability, and the global carbon cycle. Given the high potential for contamination during drilling, a suite of materials used in sample collection and processing were also analyzed to characterize their signatures. An n-alkane series ranging from C18 to C30 with δ13C isotopic values of 30.9‰ to 28.8‰ was present in lithologically diverse samples. Multiple lines of evidence point to the rock saw used to remove core exteriors during sample processing as the source of these compounds. Many of the other sample-handling procedures designed to reduce surface contamination were determined to be effective and could be implemented in future projects. This result highlights the value of careful prevention and characterization of contamination to allow for more accurate interpretations of complex and dynamic subsurface processes, and the importance that future reports of these compounds occurs in conjunction with thorough contamination assessments.

17013. 题目: Glacial-interglacial vegetation changes in northeast China inferred from isotopic composition of pyrogenic carbon from Lake Xingkai sediments
文章编号: N18070307
期刊: Organic Geochemistry
作者: Weiwei Sun, Enlou Zhang, Enfeng Liu, Jie Chang, Rong Chen, Ji Shen
更新时间: 2018-07-03
摘要: Understanding the changes in monsoon intensity and ecosystem response at different timescales is crucial for the well-being of humans, yet the paleoclimatic interpretation of stable carbon isotope (δ13C) values from northeast China records is debatable. In this study, reported δ13C data from 76 surface soils in northeast China are compiled, and a δ13C record of pyrogenic carbon (δ13CPyC) from Lake Xingkai in northeast China since the last interglacial period is presented. The aim was to investigate the orbital timescale environmental implication of geological δ13CPyC data for northeast China. The results showed a distinct increase in δ13C values of surface soils, which correlated with increasing temperature of the warmest month. Higher temperature favored the expansion of C4 plants, while precipitation had only a weak correlation with δ13C values of surface soils in the region. On an orbital timescale, the δ13CPyC record from Lake Xingkai generally reflected paleovegetation change, suggesting that the abundance of C4 plants was relatively high during the warm periods, changing to almost purely C3 plants during the cold periods. Both modern and geological analysis suggest that the climatic factor determining the δ13C in northeast China was temperature of the warmest month. This is similar to the situation for mid-latitudes such as the Chinese Loess Plateau, in contrast to low latitudes such as southern China.

17014. 题目: Sediment records of long chain alkyl diols in an upwelling area of the coastal northern South China Sea
文章编号: N18070306
期刊: Organic Geochemistry
作者: Xiaowei Zhu, Guodong Jia, Shengyi Mao, Wen Yan
更新时间: 2018-07-03
摘要: Long chain alkyl diols in sediment cores were studied in the Yuedong Upwelling (YDU) area in the coastal northern South China Sea to investigate whether sea surface temperature (SST) and upwelling intensity over the last few decades can be traced by the diol-derived indices, i.e., the LDI (long chain diol index) as a proxy for SST and the DI-1 and DI-2 (diol index 1 and 2) as proxies for upwelling intensity. The influence of riverine long chain alkyl diols (e.g., 1,13- and 1,15-diols), which may affect LDI-reconstructed SSTs, was largely ruled out based on the comparison between diol distributions in suspended particulate materials in the Pearl River estuary and the core sediments. LDI-derived SSTs in downcore sediments matched well with local annual mean SSTs. The records of DI-2 changed in parallel with the local wind stress and inversely with SST at times of upwelling, suggesting that DI-2 is an effective proxy for upwelling intensity of YDU. The DI-1 showed a generally inverse variation pattern with DI-2, implying a major influence by SST, and it is thus not an applicable upwelling indicator for YDU. A negative relationship of DI-1 and a positive relationship of DI-2 with LDI-derived SST were observed. This occurrence might be attributed to El Ni o–Southern Oscillation (ENSO), because the SST and upwelling intensity were largely modulated by ENSO, showing a warm annual mean SST during the years of enhanced El Ni o and intensified summer upwelling.

17015. 题目: Variations in abundance and distribution of methyltrimethyltridecylchromans (MTTCs) in sediments from saline lacustrine settings in Cenozoic lacustrine basins, China
文章编号: N18070305
期刊: Organic Geochemistry
作者: Kaixi Jiang, Chunming Lin, Xia Zhang, Chunfang Cai, Fei Xiao, Wenxiang He, Li Peng
更新时间: 2018-07-03
摘要: This study examines the abundance and distribution of MTTCs and biomarker compositions in samples of MTTC-rich sediments obtained from Paleogene strata in the Bohai Bay, Jianghan and Western Qaidam Basins in China. Biomarker signatures, including high C35/C34 hopane ratios, high gammacerane index values, low pristane/phytane (Pr/Ph) ratios and the presence of aryl isoprenoids, indicate saline lacustrine settings and photic zone euxinia (PZE). The distributions of MTTCs indicate significant palaeosalinity differences in the depositional environments of the three sets of samples obtained from the Bohai Bay, Jianghan and Western Qaidam Basins. These sets of samples were deposited under normal to mesosaline, meso- to hypersaline and hypersaline environments, respectively. The δ-MTTC% values are positively correlated with the values of the gammacerane index, but are negatively correlated with the Pr/Ph ratios. This result demonstrates that MTTCs do not form in the upper or lower parts of stratified water columns, but may form in the euxinic portions of photic zones. Therefore, MTTC parameters can only be used to reconstruct palaeosalinity in the euxinic portions of photic zones and are not applicable to the upper or lower parts of stratified water columns. This paper infers that variations in palaeosalinity in the euxinic portions of photic zones likely play a key role in controlling the distribution and abundance of MTTCs.

17016. 题目: Binding of heavy metals by oxidised kerogen in (palaeo)weathered black shales
文章编号: N18070304
期刊: Chemical Geology
作者: Arkadiusz Derkowski, Leszek Marynowski
更新时间: 2018-07-03
摘要: Sub-aerial weathering of black shales drives the gradual leaching of sulphur- and organic-bound heavy metal elements, which are abundant in these rocks due to geochemical deposition conditions. The formation of oxygen functional groups in kerogen, however, can lead to an opposing mechanism, metal adsorption and binding, similar to a process common in soils. An increase in cation exchange capacity (CEC) measured previously in metal complexes in black shales oxidised under laboratory conditions implies that the same phenomenon may occur in naturally oxidised black shale. This idea was tested on a unique, well-developed and -preserved Permian palaeoweathering profile containing two neighbouring but diverse black shales from the Devonian/Carboniferous boundary in the Holy Cross Mountains (Poland). In the studied black shale beds, the oxygen groups formed in kerogen in the partially-weathered zone were found to be responsible for significant changes in adsorption properties measured using hexamminecobalt(III) and Cu(II) triethylenetetramine cations, which are common probes for CEC. Compared to a pristine part of black shales, the partially weathered zone was depleted of total organic carbon (TOC), sulphur, and sulphur- and organic-bound metals, and highly enriched in Cu, which is generally present in low levels in the nascent shales. In the partially weathered zone, where TOC content is reduced, apparent CEC values surpass the CECs predicted from the contents and structures of clay minerals and correlate linearly with the content of oxygen groups developed during weathering. The adsorption properties of carboxyl groups in oxidised kerogen are suggested as being responsible for the syn- or post-weathering enrichment in Cu caused by the remobilisation of older Cu-sulphide ores present in the area. As opposed to natural weathering, aggressive oxidation, e.g. under laboratory conditions produces a high proportion of cross-linked oxygen groups that do not participate in metal cation adsorption. The CEC values of artificially oxidised samples reached a limit corresponding to those of naturally oxidised shales.

17017. 题目: Contribution of the Excited Triplet State of Humic Acid and Superoxide Radical Anion to Generation and Elimination of Phenoxyl Radical
文章编号: N18070303
期刊: Environmental Science & Technology
作者: Yuan Chen, Xu Zhang, Shixiang Feng
更新时间: 2018-07-03
摘要: Contributions of excited triplet state of humic acid (3HA*) and superoxide radical anion (O2 –), which is mainly generated via the reaction of O2 with HA-derived reducing intermediates (HA –), to phenol transformation were revealed using acetaminophen, 2,4,6-trimethylphenol and tyrosine as probe molecules. Phenol transformation was initiated by 3HA*, leading to the formation of the phenoxyl radical (PhO ), but the distribution of transformation intermediates was codetermined by 3HA* and HA –. The influence of HA – essentially resulted from the production of O2 –, which affected the fate of PhO . PhO could undergo dimerization, or react with O2 –, leading to either phenol peroxide formation (radical addition) or phenol regeneration (electron transfer). In addition, PhO could bind to HA or react with HA radicals, particularly in the absence of O2 and O2 –. These PhO reactions were dependent on the reduction potential and structure of PhO . This study also proved that the reaction of phenol with 1O2 and the reaction of PhO with O2 – lead to the same oxidation product. The contributions of 3HA* and its generated 1O2, HA – and its generated O2 – to phenol transformation were pH-dependent.

17018. 题目: Influence of pO2 on Iron Redox Cycling and Anaerobic Organic Carbon Mineralization in a Humid Tropical Forest Soil
文章编号: N18070302
期刊: Environmental Science & Technology
作者: Chunmei Chen, Christof Meile, Jared Wilmoth, Diego Barcellos, Aaron Thompson
更新时间: 2018-07-03
摘要: Ferrous iron (FeII) oxidation is an important pathway for generating reactive FeIII phases in soils, which can affect organic carbon (OC) persistence/decomposition. We explored how pO2 concentration influences FeII oxidation rates and FeIII mineral composition, and how this impacts the subsequent FeIII reduction and anaerobic OC mineralization following a transition from oxic to anoxic conditions. We conducted batch soil slurry experiments within a humid tropical forest soil amended with isotopically labeled 57FeII. The slurries were oxidized with either 21% or 1% pO2 for 9 days and then incubated for 20 days under anoxic conditions. Exposure to 21% pO2 led to faster FeII oxidation rates and greater partitioning of the amended 57Fe into low-crystallinity FeIII-(oxyhydr)oxides (based on M ssbauer analysis) than exposure to 1% pO2. During the subsequent anoxic period, low-crystallinity FeIII-(oxyhydr)oxides were preferentially reduced relative to more crystalline forms with higher net rates of anoxic FeII and CO2 production—which were well correlated—following exposure to 21% pO2 than to 1% pO2. This study illustrates that in redox-dynamic systems, the magnitude of O2 fluctuations can influence the coupled iron and organic carbon cycling in soils and more broadly, that reaction rates during periods of anoxia depend on the characteristics of prior oxidation events.

17019. 题目: Overlooked Risks of Biochars: Persistent Free Radicals trigger Neurotoxicity in Caenorhabditis elegans
文章编号: N18070301
期刊: Environmental Science & Technology
作者: Thora Lieke, Xuchao Zhang, Christian E.W. Steinberg, and Bo Pan
更新时间: 2018-07-03
摘要: In recent years, biochars have gained increasing interest in mitigating climate changes and revitalizing contaminated or drained soil. Studies determining their impact on the ecosystem, especially on soil invertebrates, however, are still scarce and the neurotoxic potential of biochars has never been evaluated before. Using the model organism Caenorhabditis elegans we determined the neurotoxic effect of biochar produced from rice straw by pyrolysis at 500 °C at concentrations ranging from 0 to 2000 mg C·L–1. Biochar had a hormetic effect on locomotion behavior. Furthermore, high concentrations impaired defecation as well as the recognition and response to a chemical attractant. None of the potential toxic chemicals in the biochar had sufficient high concentrations to explain the detected neurotoxic effect. Using electron paramagnetic resonance (EPR) spectroscopy, we detected free radicals in the biochar. Detrimental reaction of free radicals with biotic macromolecules can induce oxidative stress responses and are a potential reason for the evaluated neurotoxic effect of biochar. Overall, we were able to prove that biochars have the potential to act as weak neurotoxins to soil organisms and effects of persistent free radicals should be investigated further.

17020. 题目: δ13C of aromatic compounds in sediments, oils and atmospheric emissions: A review
文章编号: N18070204
期刊: Organic Geochemistry
作者: Alex I. Holman, Kliti Grice
更新时间: 2018-07-02
摘要: This review discusses major applications of stable carbon isotopic measurements of aromatic compounds, along with some specific technical aspects including purification of aromatic fractions for baseline separation. δ 13C measurements of organic matter (OM) in sediments and oils are routine in all fields of organic geochemistry, but they are predominantly done on saturated compounds. Aromatic compounds are important contributors to sedimentary organic matter, and provide indication of diagenetic processes, OM source, and thermal maturity. Studies have found evidence for a small 13C-enrichment during diagenetic aromatisation of approximately 1–2‰, but the formation of polycyclic aromatic hydrocarbons (PAHs) from combustion and hydrothermal processes seems to produce no effect. Likewise, maturation and biodegradation also produce only small isotopic effects. An early application of δ 13C of aromatic compounds was in the classification of oil families by source. Bulk measurements have had some success in differentiating marine and terrigenous oils, but were not accurate in all settings. Compound-specific analyses measure certain aromatics with strong links to source, therefore allowing more accurate source identification. δ 13C measurements of individual aromatic compounds also allow identification of higher plant input in ancient sediments, even after severe diagenetic alteration or combustion to PAHs. Perylene, a PAH with a historically contentious origin, was assigned a source from wood-degrading fungi on the basis of its isotopic composition. Stable carbon isotopic measurements are also important in the analysis of organic matter from Chlorobiaceae, which is an important indicator of photic zone euxinic conditions in ancient sediments. A large range of aromatic products are formed from the carotenoid pigments of Chlorobiaceae, with an enriched carbon isotopic composition characteristic of the reverse tricarboxylic acid photosynthetic pathway employed by this family of organisms. In future, site-specific isotope analysis using techniques such as nuclear magnetic resonance spectrometry and high-resolution isotope ratio mass spectrometry may reveal more information about isotopic effects associated with aromatisation processes and maturation.

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