Optical characteristics and solar photodegradation of dissolved organic matter in Arkansas River, USA

Dissolved organic matter （DOM）, a mixture of numerous organic compounds of 30 to 300000 D, exists in all natural water resources including rivers, lakes and oceans, and plays a very important role in global carbon cycle and ecology. The DOM molecules absorb UV light strongly in short wavelengths and prevent microorganisms from being damaged by solar UV irradiation. Meanwhile, the large DOM molecules are then photodegraded into inorganic carbon and smaller organic molecules which are easier for bacterioplankton to digest. The Arkansas River is one of the largest rivers in the US, and a major input of organic materials to the Mississippi River and Gulf of Mexico. However, the photochemical properties of the DOM in the river water have not been investigated. To study this photodegradation process of the Arkansas River, water samples from the river were collected, filtered, sealed into quartz flasks, and exposed to sunlight for up to 15 hours. Some samples were retrieved from the flasks at certain time intervals. The intensity of the sunlight was measured during the exposure process at 30 min to 1 hr intervals. UV-vis absorption, fluorescence emission, 3D fluorescence spectra and DOM concentrations were determined for all retrieved samples. It was found that the total DOM concentration decreased while the dissolved inorganic carbon （DIC） concentration increased in the samples. UV absorption and fluorescence intensity of DOM decreased exponentially. The disappearance rate of UV absorption varied with wavelength. The loss of integral fluorescence was about 2.6 times that of the UV absorption at the excitation wavelength. In addition, the quantum yields also decreased, and the peak position of 3D fluorescence scan shifted to shorter wavelength.     

Characterization of organic matter deposited in the oriental zone from Moknine hypersaline environment, oriental Tunisia

The geochemistry data show that the total organic carbon （TOC） contents are high in the surface sediments in the eastern part of the Moknine＇ s Sebkha. Low decreasing of organic matter （ OM ） with increasing depth indicates the good preservation of OM in modern sediments. ＂Lignite levels＂ inserted in the sand sequence and deposited at the edge and in the intermediate zone are considered as lithologic and organic markers. It is characterized by high TOC and poor hydrogen index （HI） , indicating a higher plant origin and good preservation of OM in thin beds under anoxic condition. In all samples low values of HI are typical for strong terrigenous input in the Sebkha. Gas chromatography （GC） of saturate fraction showed that OM in the border zone is provided from plants but in the central zone OM is a mixture of terrestrial fraction and little fraction from microalgae. The study of free lipids indicated that this environment was influenced by intense bacterial and microbial activities, as evidenced by the abundance of n-alkanes and nC18-nC22.     

Origin and three-dimensional fluorescence spectrum of the chromophoric dissolved organic matter in Yangtze estuary, East China

Dissolved organic matter （DOM） is an important chemical component in natural water. Chromophoric dissolved organic matter （CDOM）, a fraction of optical properties, plays art important role in the biogeochemical cycle of nutrients in aquatic environment. People realized that DOM cycle is crucial in the global carbon and nitrogen flux, and also is inherently related to nutrients and trace metal elements. Therefore, CDOM was concerned by scientists in global oceanography and limnology fields. Water samples were collected from three sections （North Channel, South Channel and Zhuyuan） of the Yangtze （Changjiang River） estuary in March 2006 Three-dimensional excitation emission matrix （3-DEEM） fluorescence spectra were analyzed for those filtrates through Whatman GF/F filters. Dissolved organic carbon （DOC） was also measured by TOC analyzer. The tidal variety was also taken into account. The 3-D EEM fluorescence scans suggested the fluorescence characteristics of humic acid （Ex=332-344 nm, Em=439-451 nm） and fulvic acid （Ex=250-254 nm, Em=472-478 nm） were obvious, and the fluorescence group of protein-like and tyrosine （Ex=230 nm, Em=283 nm） was also found. They are mainly composed of CDOM in the Yangtze estuary. Further data analysis, especially the fluorescence index （f 450/500）, showed that terrestrial signal was rather strong （1.41-1.65） in the surface water, however, some terrestrial CDOM signals of bottom water showed excursions （1.28-1.39）. On the other hand, anthropogenic sign was impressed in the waters of Zhuyuan, which is one of the main drain outlets of Shanghai Metropolis. DOC concentrations ranged from 2.2 mg/L to 3.4 mg/L in Zhuyuan and South Channel, and from 2.0 mg/L to 2.4 mg/L in North Channel. The tide effect played a role in the composition of the CDOM measured by 3-D fluorescence scan technology.     

Micro faunal assemblages in the Ordovician – Silurian successions from the Pin Valley of Tethys Himalaya, India

The Spiti basin together with the Zanskar basin forms the largest basin among the Tethyan Himalayan successions and forms one of the best-developed sec-tions in the Tethyan Tibetan belt. The basin is one of the classical areas, which depicts a continuous fos-siliferous Palaeozoic - Mesozoic successions. The present studies are focused on the Ordovician and Si-lurian successions of the Pin valley of the Spiti basin. Pin valley exposes richly fossiliferous lithological successions from Neoproterozoic to Cretaceous; therefore, it is an ideal section for the detail paleobi-ological and geological studies.     

‘Indicator’ carbonaceous phyllite/graphitic schist in the Archean Kundarkocha gold deposit,Singhbhum orogenic belt,eastern India: Implications for gold mineralization vis-a-vis organic matter

Carbonaceous rocks in the form of graphitic schist and carbonaceous phyllite are the major host rocks of the gold mineralization in Kundarkocha gold deposit of the Precambrian Singhbhum orogenic belt in eastern India. The detection of organic carbon, essentially in the carbonaceous phyllite and graphitized schist within the Precambrian terrain, is noted from this deposit. A very close relationship exists between gold mineralization and ubiquitous carbonaceous rocks containing organic carbon that seems to play a vital role in the deposition of gold in a Precambrian terrain in India and important metallogenetic implications for such type of deposits elsewhere. However, the role played by organic matter in a Precambrian gold deposit is debatable and the mechanism of precipitation of gold and other metals by organic carbon has been reported elsewhere. Fourier transform infrared spectroscopy (FTIR) results and total organic carbon (TOC) values suggest that at least part of the organic material acted as a possible source for the reduction that played a significant role in the precipitation of gold. Lithological, electron probe analysis (EPMA), fluid inclusions associated with gold mineralization, Total Carbon (TC), TOC and FTIR results suggest that the gold mineralization is spatially and genetically associated with graphitic schist, carbonaceous phyllite/shale that are constituted of immature organic carbon or kerogen. Nano-scale gold inclusions along with free milling gold are associated with sulfide mineral phases present within the carbonaceous host rocks as well as in mineralized quartz-carbonate veins. Deposition of gold could have been facilitated due to the organic redox reactions and the graphitic schist and carbonaceous phyllite zone may be considered as the indicator zone.     

Matrix protected organic matter in a river dominated margin: A possible mechanism to sequester terrestrial organic matter?

The provenance of organic matter in surface sediments from the northern Gulf of Mexico was investigated by analyzing the compositions of lipid biomarkers (n-alkanes, fatty acids, sterols) liberated after a series of chemical treatments designed to remove different organo-mineral matrix associations (i.e. freely extractable, base-hydrolyzable, unhydrolyzable). Bulk analyses of the organic matter (carbon content, carbon:nitrogen ratios, stable and radiocarbon isotopic analyses) were also performed on the intact sediments and their non-hydrolyzable, demineralized residue. We found recognizable lipids from distinct sources, including terrestrial vascular plants, bacteria and marine algae and zooplankton, within each of the isolated fractions. Based on the lipid signatures and bulk compositions, the organic matter within the unhydrolyzable fractions appeared to be the most diagenetically altered, was the oldest in age, and had the highest abundance of terrigenous lipids. In contrast, the base-hydrolyzable fraction was the most diagentically unaltered, had the youngest ages and was most enriched in N and marine lipids. Our results indicate that fresh, autochthonous organic matter is the most important contributor to base-hydrolyzable lipids, whereas highly altered allochthonous sources appear to be predominant source of unhydrolyzable lipids in the surface sediments from the Atchafalaya River shelf. Overall, the lipid biomarker signatures of intact sediments were biased towards the autochthonous source because many of the organic compounds indicative of degraded, terrigenous sources were protected from extraction and saponification by organo-mineral matrices. It is only after these protective matrices were removed by treatment with HCl and HF that these compounds became evident.     

Vulnerability assessment through index modeling: a case study in Muriganga–Saptamukhi estuarine interfluve,Sundarban, India

The coastal regions, deltas, and estuaries are severely affected by the sea level rise and cyclonic activities and climate changes. Sundarban delta is one of the most mysterious landscapes in the world, which has successively evolved due to sediment accumulation by the great Ganga and Brahmaputra river system. The area is characterized by low-lying islands and a flat topography coupled with macro-tidal activities, powerful surges, and seasonal cyclonic events. All these conditions put together this landscape defenseless to frequent flood and erosion. Since the last hundred years, the face of Sundarban has been changed remarkably from wildest to human-occupied territory by protecting this low-lying flat plain from tidal inundation through artificial embankment. In this background, the current study attempts to highlight the spatial extent and magnitudes of internal risk factors of the region using the composite vulnerability index. Coastal vulnerability defines a system’s openness to flood and erosion risk due to hydrogeomorphic exposures and socio-economic susceptibility in conjunction with its capacity/incapacity to be resilient and to cope, recover, or adapt to an extent. Coastal vulnerability assesses the potential risk from erosion and flooding of any low-lying coastal region due to its physiographical and hydrological exposures, socio-economic and political susceptibility, and resilience capacity. A natural system affects the socio-economic scenario of any region. Hence, multidimensional databases can be more effective to understand the extent of exposure, susceptibility, and resilience of any system. To throw some light on the situation of vulnerability of western estuarine Sundarban, between Muriganga and Saptamukhi interfluve, the composite vulnerability index has been carried out to delineate the magnitude and spatial extent of vulnerability with the help of quantitative techniques and geospatial tools. The estuarine tracts and coastal parts of the Ganga delta are two of the most densely populated areas in the world. The study highlights the critical situation of the population under different potential risk classes residing in the study area with the intention of suggesting some proper course of action of planning and management to conserve coastal communities in their original habitat.     

Kaveri crater – An impact structure in the Precambrian terrain of southern India

The region to the east of Palghat gap is of low elevation and nearly circular in shape. It forms a part of the Kaveri river basin. The predominantly gneissic terrain is surrounded by the charnockitic hill ranges, prominent among which are Nilgiris and Biligirirangan to the north; and Anaimalai and Kodaikanal to the south. The charnockite massifs have a steep slope facing the circular feature and a gentler slope in the opposite direction. Fractures/faults/shear zones are noticed in many parts. The Bouguer anomaly in the gneissic terrain is elliptical in shape and positive, relative to the surrounding elevated region. The magnetic contours are also elliptical and the magnetic basement is deeper by about one km compared to regions in the periphery. The shallow seismic velocity picture from Chennimalai to Palani indicates a graben structure. The velocity structure also depicts a 4–5 km Moho upwarp near Chennimalai. Junction between the gneissic and charnockitic terrain and even beyond, is marked by the presence of pseudotachylites and breccia. Field and petrographic studies indicate presence of suevite, Planar Deformation Features (PDF), Planar Fractures, diaplectic glass of quartz and plagioclase and spherical inclusion in suevite. These evidences taken together point to an extra-terrestrial impact which created a crater of approximately 120 km in diameter. Several lines of indirect evidences point to Neoproterozoic age for the impact. Kaveri Crater is the fourth largest crater on the surface of the Earth; other larger craters being Vredefort (160 km), Chicxulub (150 km) and Sudbury (130 km).     

Molecular composition and indigenity of organic matter in Late Neoproterozoic sedimentary rocks from the Yangtze region, South China

1 Introduction As a linkage between the biosphere and the geosphere, organic geochemistry, especially molecular markers, has become a powerful tool for investigating important geological events and the evolutionary history of ancient life on Earth (Kvenvo…     

Quantification and characterization of condensed organic matter in sediments from the Pearl River Delta and Estuary, South China

Nonhydrolyzable carbon （NHC） and black carbon （BC） were measured upon treatments with the HCl/HF/trifluoroacetic acid method, and with the combustion method at 375 ℃, respectively in three contaminated soils from the urban area of Guangzhou and twenty-two bulk and size-fractionated sediments from the Pearl River Delta and Estuary, China. The isolated NHC and BC fractions were also characterized using elementary analysis, radiocarbon accelerated mass spectroscopy （AMS）, solid state ^13C cross-polarization and magic angle spinning unclear magnetic resonance spectroscopy （^13C-CP/MAS NMR）, Fourier transformed infrared spectroscopy （FTIR）, and Raman microspectrometry. The results showed that the NHC and BC accounted for 25.6%-84.7 % and 4.14%-17.3%, respectively, of the total organic carbon （OC） with averages of 51.9% and 11.2% in the soils and sediments. For the less contaminated, low OC fiver and estuary sediments （WR and C08）, the OC and NHC concentrations increased with decreasing particle size.     

Mercury enrichments in core sediments in Hugli–Matla–Bidyadhari estuarine complex,north-eastern part of the Bay of Bengal and their ecotoxicological significance

Mercury concentrations (Hg_T) in fine-grained fraction (<63 μm) of core sediments of the Hugli–Matla–Bidyadhari estuarine complex, India were analyzed. Results revealed a wide range of spatial variations (<4–93 ng g⁻¹ dry weight) with a definite enhancement level at the lower stretch of the estuarine complex infested with mangrove plants, which might act as a sink to Hg_T. An elevated concentration of Hg was encountered in surface/subsurface layer of the core in majority of the cases resulting from physical, biogenic and postdepositional diagenetic processes that remobilized and resuspended the metal from deeper sediments. A strong positive correlation was observed between the Hg and clay fraction content of the sediments, while the correlations of Hg with Al, Fe and Mn were poor. Based on the index of geoaccumulation (I _geo) and effects range-low (ER-L) value, it is considered that the sediments are less polluted and thus there is less chance of ecotoxicological risk to organisms living in sediments.     

Elemental and organic geochemistry of Gondwana sediments from the Krishna–Godavari Basin,India

Elemental and organic geochemical studies have been carried out on the Gondwana sediments, collected from the outcrops of Permian and Jurassic–Cretaceous rocks in the Krishna–Godavari basin on the eastern coast of India, to understand their paleo and depositional environment and its implications for hydrocarbon generation in the basin. Amongst the studied formations, the Raghavapuram, Gollapalli and Tirupati form a dominant Cretaceous Petroleum System in the west of the basin. Raghavapuram shales and its stratigraphic equivalents are the source rock and Gollapalli and Tirupati sandstones form the reservoirs, along with basaltic Razole formation as the caprock. Major element systematics and X-ray diffraction study of the sandstones indicate them to be variably enriched with SiO₂ relative to Al₂O₃ and CaO, which is associated, inherently with the deposition and diagenesis of the Gondwana sediments. Post-Archean Average Shale normalized rare earth elements in shales show enrichment in most of the samples due to the increasing clay mineral and organic matter assemblage. A negative europium and cerium anomaly is exhibited by the REE's in majority of rocks. Composed primarily of quartz grains and silica cement, the Gollapalli and Tirupati sandstones have characteristics of high quality reservoirs. The shales show a significant increase in the concentration of redox sensitive trace elements, Ni, V, Cr, Ba and Zn. The total organic carbon content of the shales ranges between 0.1 and 0.5 wt%. Programmed pyrolysis of selected samples show the Tmax values to range between 352–497 °C and that of hydrogen index to be between 57–460 mgHC/gTOC. The organic matter is characterized by, mainly, gas prone Type III kerogen. The n-alkane composition is dominated by n-C₁₁–C₁₈ and acyclic isoprenoid, phytane. The aromatic fraction shows the presence of naphthalene, anthracene, phenanthrene, chrysene and their derivatives, resulting largely from the diagenetic alteration of precursor terpenoids. The organic geochemical proxies indicate the input of organic matter from near-shore terrestrial sources and its deposition in strongly reducing, low oxygen conditions. The organic matter richness and maturity derived from a favorable depositional setting has its bearing upon the Gondwana sediments globally, and also provides promising exploration opportunities, particularly in the Raghavapuram sequence of the KG basin.     

Sedimentary organic matter record of recent environmental changes in the St. Marys River ecosystem,Michigan–Ontario border

Lake George, located in the St. Marys River, has been heavily impacted by human-induced environmental changes over the past century. The effects of human impacts starting in the late nineteenth century and of natural, gradual diagenesis can be distinguished in the bulk organic matter and molecular contents of the sedimentary record. Organic carbon concentrations increase from 0.5% in sediments deposited 200 years ago to ∼4% in recent sediments. A fourfold increase in organic carbon mass accumulation rates accompanies the change in concentrations. Elevated C/N ratios in near-modern sediments indicate that increased delivery of land-derived organic matter has been responsible for much of the recent increases in sedimentary organic carbon. Organic δ¹³C and δ¹⁵N values change significantly and coincidentally with the environmental changes, reflecting depressed algal productivity since the introduction of industrial effluents to the aquatic system, increased delivery of land-derived organic matter and some impacts of acid rain. Increases in microbial and petroleum hydrocarbon contributions occur in sediments deposited since 1900. Fatty acid distributions provide evidence of substantial microbial reworking of organic matter throughout the sedimentary record.     

Sedimentary environments of organic matter from Middle Permian source rocks in northern Xinjiang, China

1IntroductionThe formation of the Junggar,Turpan and Ili ba-sins is ascribed to Hercynian orogeny between theJunggar and Tianshan Mountains during the MiddlePermian.The rock assemblage of thick and stable sedi-mentary dark muddy shales interbedded with th…     

Refractory organic matter in sediments from the North–West African upwelling system: abundance,chemical structure and origin

Refractory (insoluble and nonhydrolyzable) organic matter (ROM) was studied in sediments underlying the north–west African upwelling system. Two core samples: beginning of glacial isotope stage 4 (ca. 70,000 yr BP; depth bsf 360 cm) and interglacial isotope substage 5d (ca. 90,000 yr BP; depth bsf 480 cm) were analyzed, along with a surface sample. ROM, which accounts for a substantial part of the total organic matter (OM) in these sediments (ca. 20% for the two core samples and 10% for the surface sample), was isolated and examined for its morphological and chemical features using a combination of transmission and scanning electron microscopy, spectroscopy (FTIR, solid state ¹³C NMR) and analytical pyrolysis (Curie point flash pyrolysis–GC–MS). These studies allowed the chemical structure of the three ROMs (chiefly based on melanoidin-type macromolecules) and their mechanism of formation (degradation–recondensation of products mainly derived from proteinaceous material) to be established. Such a formation probably began in the water column and continued within the sediment upper layers. Important differences, concerned both with OM chemical structure and preservation mechanism, were noted upon comparison with recently studied sediments underlying the Peru upwelling system. These differences between the two systems, in spite of similarities in primary production, must reflect the combined influence of factors such as upwelling intensity (primary productivity), water depth and iron supply.     

Sand dunes and valley fills from Preboreal glacial-lake outburst floods in south-eastern Norway – beyond the aeolian paradigm

A major glacial-lake outburst flood in the Glomma valley, south-eastern Norway, took place during the final decay of the Scandinavian Ice Sheet. A combined morphological, geophysical and sedimentological study provides new insight into the variety of processes and deposits of the flood. The studied succession, some tens of metres in thickness, comprises the fill of a major flood basin that developed during hydraulic ponding. Large-scale sand dunes and bars accumulated downstream of locations with expanding flow. Most notable are 10 m high, concentric dune ridges that accumulated downstream of a topographical constriction hosting a high-velocity flow. Flow expansion at the outlet generated intense turbulence and scouring. The sand-loaded eddies helped feeding the semi-stationary dune ridges that grew vertically and downflow under high aggradation rates. Internal structures vary but reflect an overall shift in sedimentation from prevailing supercritical flow to overall subcritical flow conditions at high flood levels. Loading by water and sediment caused large-scale, synsedimentary deformation, increasing local accommodation space. Fast-falling flood levels caused stronger flow locally, while mud and fine sand settled in stagnant pools. The fall caused a significant drop in hydrostatic pressure. This triggered a release of excess pore pressure causing massive dewatering and fluidisation. Water-escape structures include numerous (sub)vertical pipes. The present study shows that outburst flood-generated, large-scale dunes can develop in well-sorted, fine sand and are thereby easily confused with aeolian deposits. Several dune fields in south-eastern Norway are here reinterpreted as the product of at least two major flood events. Sandy dune fields with similar characteristics elsewhere in Scandinavia should likely also be reinterpreted, and the role of outburst floods during the final deglaciation of Scandinavia has seemingly been underestimated. The study emphasises the importance of ponding, flow expansion, sorting, rapidly changing pressure conditions and deformation for outburst flood-related sedimentation.     

Citizenship,abandonment and resistance in the India–Bangladesh borderland

Drawing on ethnography in the enclaves in India and Bangladesh, this paper explores a multifaceted yet enduring relationship between citizenship, abandonment and resistance. Following the partition in 1947, the enclave residents’ citizenry was enacted like other Indian or Bangladeshi citizens’ disregarding these enclaves’ trans-territorial reality. This paper will demonstrate that enclave dwellers did not live in the ‘citizenship gap’, the difference between rights and benefits of citizenship, rather they lived without any citizenship rights. Life in these enclaves was highly complex and experiences in the enclaves challenge the usefulness of citizenship as a universal framework of analysis for the people who are ranked as citizen but never have it. In this context, a combination of the reverse conceptualisation such as citizenship and Agamben’s conceptualisation of abandonment not only allows for these dimensions of lived experiences to be addressed and explored, it also focuses on the temporal aspect of citizenship implicated in politics. Finally, the paper calls for widening the consideration of the empirical study on everyday citizenship practices and experiences around the globe to extend and intensify the citizenship literatures.