High Total Organic Carbon Content Research Articles

Integrated Formation Evaluation of a Complex Tight Oil Reservoir in Junggar Basin, Northwest China

Jimusaer tight oil reservoir is characterized by complex lithology, low permeability and high total organic carbon (TOC) content. These features make conventional logging responses very complicated and bring big troubles to reservoir identification. Horizontal well drilling is extremely difficult due to high heterogeneity and uncertain faulting. To maximize oil production with low cost, an integrated solution is provided. First, accurate reservoir characteristics of the pilot well was got using an unconventional evaluation approach by combining capture spectroscopy log, micro-resistivity imager log, nuclear magnetic resonance log, et al. Second, structure analysis for sidetracking well and well correlation between the sidetracking well and the pilot well were done to guide the horizontal section drilling. Third, reservoir quality and completion quality were evaluated for horizontal well, and a 3D structural model was built to optimize the stimulation design by combining reservoir quality, completion quality and natural fractures.

Marine palynology of the Oceanic Anoxic Event 3 (OAE3, Coniacian – Santonian) at Tarfaya, Morocco, NW Africa – transition from preservation to production controlled accumulation of marine organic carbon

The paper presented is the first comprehensive, fully quantitative, high resolution study of marine palynology from an OAE3 black-shale environment. It is based on 175 m core spanning the upper Turonian to lower Santonian at Tarfaya, Morocco, NW Africa, which has been sampled from centimetre to 3 m intervals. The results are integrated and discussed with lithology and geochemistry data to (1) distinguish between potential changes in production and preservation of total organic carbon (TOC) accumulation and (2) constrain the stratigraphic position of the Oceanic Anoxic Event 3 (OAE3).The succession is characterized by increased total organic carbon (TOC), varying between 1% and 19% (average about 6%). Distinct black-shale horizons of variable thickness appear episodically throughout the succession, with higher frequency in the late Turonian. Higher TOC contents do not strictly correlate to lithologic black-shales or peaks of a specific taxon of organic-walled algae. The palynomorph spectrum is strongly dominated by organic-walled algae, with the ratio of terrigenous sporomorphs to organic-walled algae (t/m index) varying between zero and 0.05 (average 0.01). The dominance of algal organic matter is corroborated by the prevalence of Type I kerogen identified using Rock-Eval pyrolysis. Dinocyst diversity is low, with the absolute taxa number varying from 7 to 27 between single samples. The peridinioid/gonyaulacoid ratio of dinocysts (p/g ratio) shows strong fluctuations, varying between 1 and 283 (average of about 100).The upper Turonian interval is dominated by Bosedinia spp., a dinocyst taxon formerly described as abundant only in lacustrine sediments from the Oligocene and Miocene of SE Asia. This dominance is episodically modified by the increase of the warm-temperate waters dinocysts fraction, here mainly represented by the genera Alterbidinium, Isabelidinium and Spinidinium. Within the Coniacian-Santonian, black-shale horizons are limited in number and are concentrated within the upper Coniacian to lower Santonian interval. The dinocysts show alternating, prominent peak abundances of Palaeohystrichophora spp. and the warm-temperate water dinocysts fraction, here mainly represented by the genera Trithyrodinium and Chatangiella. However, a final episode of increased proportions of Bosedinia spp. is confined to a 5 m thick black-shale horizon closely spanning the Coniacian-Santonian boundary.Changes in the ratio of total sulphur to total organic carbon (TS/TOC) reflect fluctuating oxygen contents of bottom waters throughout the late Turonian to Santonian. These are significantly parallelled by the alternation of dinocysts assemblages suggestive of enhanced upwelling and water column stratification respectively, probably reflecting changes in the mode of TOC accumulation. Accordingly, preservation largely prevails during the late Turonian interval and changes towards increased production within the Coniacian-Santonian. However, a final preservation-event is probably represented by the black-shale horizon closely spanning the Coniacian-Santonian boundary (top Dicarinella concavata foraminifera zone), which may reflect an episodic shutdown of a major upwelling cell. It is thus proposed, that the “culmination” of the OAE3 at Tarfaya may represent intermittent preservation of TOC within an otherwise high productivity environment related to a global cooling trend.

Correlation of in vivo relative bioavailability to in vitro bioaccessibility for arsenic in household dust from China and its implication for human exposure assessment.

Incidental ingestion of household dust is an important arsenic (As) exposure pathway for children. However, compared to soils, assessment of As relative bioavailability (RBA) in household dust is limited. In this study, As-RBA in 12 household dust samples (7–38 mg kg(–1)) was measured using an in vivo mouse model and compared to As bioaccessibility determined using 4 assays [Solubility Bioaccessibility Research Consortium method (SBRC), in vitro gastrointestinal method (IVG), Deutsches Institut für Normunge.V. method (DIN), and physiologically based extraction test (PBET)]. Arsenic RBA ranged from 21.8 ± 1.6 to 85.6 ± 7.2% with samples containing low Fe and high total organic carbon content having higher As-RBA. Strong in vivo–in vitro correlations (IVIVC) were found between As-RBA and As bioaccessibility for SBRC and DIN (r2 = 0.63–0.85), but weaker ones were obtained for IVG and PBET (r2 = 0.29–0.55). The developed IVIVC for SBRC and DIN were used to calculate As-RBA based on As bioaccessibility for an additional 12 household dust samples. Although As bioaccessibility differed significantly (up to 7.7-fold) based on in vitro methods, predicted As-RBA was less variable (up to 3.0-fold) when calculated using As bioaccessibility data and the corresponding IVIVC. Our data suggested that both SBRC and DIN had potential to assess As bioavailability in household dust samples; however, additional research is needed.

Geochemical Characterization of Jurassic Source Rocks from Cuba: 2. Constancia Formation in Onshore Varadero Oils Fields

Samples collected from the Upper Jurassic Constancia Formation in the Varadero oilfields, located in the Northern Marginal Basin of Cuba were analyzed to evaluate the type and origin of the organic matter and their source rock potential. This study is based on geochemical analyses of whole rock (total organic carbon content (TOC), Rock-Eval pyrolysis), petrographical analyses (vitrinite reflectance, spore colouration index (SCI), palynofacies) and gas chromatography/mass spectrometry (GC-MS). Results obtained from 25 core samples collected from four petroleum exploration wells indicate that these rocks have organic carbon contents ranging from 0.13 wt% to high 5.84 wt%. The average hydrocarbon generation potential as determined by Rock-Eval pyrolysis potential (S2) is between 0.34–5 mg HC/g rock for samples with low TOC, suggesting good to excellent potential to generate oil and 5–49.9 mg HC/g rock for samples with high TOC. Based on palynofacies analyses three organic assemblages have been identified. Quantitative and qualitative analyses of palynofacies show that the Constancia Formation of Jurassic age, represent oxic proximal and suboxic-anoxic/marine restricted environment. The Amorphous organic matter is the dominant element of the particulate organic matter in the assemblages I, followed by structured terrestrial organic matter and spores/pollen in the assemblages III. The results of Rrandom and SCI suggest a maturity level of the organic matter ranging from immature to marginally mature. The Constancia extract rock are immature to early maturity evaluated from the C29-αα20S/(S + R) and C29–20R ββ/(ββ + αα) sterane indices.

Chemistry Analysis for Atmospheric Water Utilization as Drinking Water

AbstractWith the aim of developing condensed atmospheric water resources as drinking water, atmospheric water samples were collected in six different areas of Shenzhen, China: industrial area, commercial area, road, residential area, green land, and school. The following chemical analytes of atmospheric water were investigated: electrical conductivity (EC), pH, six anions (F−, Cl−, NO2−, NO3−, SO42−, PO43−), five cations (Na+, NH4+, K+, Mg2+, Ca2+), total organic carbon (TOC), total bacterial count, and nine trace metals (Cr, Mn, Ni, Cu, Zn, As, Se, Cd, Pb). Most of analyses met drinking water standards in China, and European Commission, except NO2− and total bacterial count; after filtered, all indicators for water quality were better than drinking water standards and even tap water. In different areas, atmospheric water quality was affected by certain ambient pollutants and showed its own specialty. In samples from road areas, high concentrations of Mn, NH4+, NO2−, SO42−, and TOC were attributable to ve...

Thermal maturity history and petroleum generation modelling for the Upper Jurassic Madbi source rocks in the Marib-Shabowah Basin, western Yemen

Widely exposed in the Marib-Shabowah Basin, the early Upper Jurassic Madbi Formation is divided into two units (Lam and Meem, youngest to oldest) believed to be major source rocks. The Madbi source rocks are characterized by relatively high total organic carbon contents (TOC) ranging from 0.5 to 10.0 wt%, meeting the standard as a fair to excellent source rock generative potential. They contain Type II kerogen grading to mixed Type II/III kerogens and Type III kerogen with HI values between 40 and 620 mg HC/g TOC. Vitrinite reflectance values range from 0.41 to 2.61% Ro, indicating sufficient thermal maturity for both oil and gas generation.Burial/thermal history models indicate that the Upper Jurassic Madbi source rocks passed the peak of oil generation stage and convert the oil to dry gas in the Late Jurassic to Late Cretaceous time. Oil generation began immediately after deposition in the Late Jurassic time (150–145 Ma) and maximum rates of oil with significant gas have been generated during Late Cretaceous time (110–65 Ma). The peak gas generation occurred during the early Tertiary. The modelled hydrocarbon expulsion evolution suggests that the timing of hydrocarbon expulsion from the Madbi source rocks began in the early Cretaceous (140 Ma) persisted to present-day. The modelling results also indicate that the peak hydrocarbon generation and expulsion from Madbi source rocks in the studied area occurs well after deposition of the seal rock and formation of traps, ensuring entrapment and preservation of migrated hydrocarbons.

Coal-Bearing Organic Shale Geological Evaluation of Huainan–Huaibei Coalfield, China

Organic shale in coal-bearing strata contains a large amount of shale gas resource in China. The organic shale is typically interlayered with coal beds and tight sandstone, and thus, joint development of the three unconventional gases, coal bed methane, tight gas, and shale gas, is becoming a frontier topic. In this paper, an integrated characterization of coal-bearing shale was implemented through a systematic series of measurements to assess the potential of shale gas in the Huainan–Huaibei coalfield. According to X-ray diffraction, quartz, kaolinite, and mixed illite/smectite (I/S) are the major minerals and the brittleness index for most samples is low to moderate (30–60). The risk of water swelling during hydraulic stimulation may be low in terms of the low concentration of smectite and mixed I/S. The efficiency of acid solution is limited by the low concentration of calcite and dolomite. The pore system has been well-developed on the basis of the thin section, scanning electron microscopy, mercury intrusion, and N2 physisorption. Microfractures and large macropores (1–15 μm) were observed in many samples. Slit shape is the predominant geometry of pores, followed by eclipse. Meso- and macropores are the best developed pores in coal-bearing organic shale, with two peaks at 2–3 and 100 nm. Specific surface area and clay minerals can significantly affect the gas adsorption capacity, but total organic carbon (TOC) content is the primary controlling factor. Furthermore, the high TOC content and appropriate thermal maturities imply high potential of gas generation with possible contribution from biogenic gas. These analyses indicate the Permian coal-bearing organic shale in the Huainan–Huaibei coalfield being a promising player in shale gas development.

Organic geochemistry of Mississippian shales (Bowland Shale Formation) in central Britain: Implications for depositional environment, source rock and gas shale potential

Marine Carboniferous shales are proven hydrocarbon source rocks in central Britain. In this contribution the depositional environment and shale gas/liquid potential of the lower Namurian part of the Bowland Shale Formation is studied using 77 thermally immature samples from the Duffield borehole.The Bowland Shale Formation comprises mudstone and turibidite lithofacies reflecting a pronounced sea level controlled cyclicity. The total organic carbon (TOC) content of the mudstones lithofacies (including marine bands) and of fine-grained rocks within the turibidite lithofacies varies between 1.3 and 9.1%. Hydrogen index (HI) values imply the presence of kerogen type III-II.According to biomarker ratios and bulk geochemical parameters, marine bands (maximum flooding surfaces, mfs) were deposited in deep water with slightly enhanced, normal, or slightly reduced salinity. Mudstones of the highstand systems tract (HST) were deposited in environments with normal to reduced salinity, whereas photic zone anoxia favoured the preservation of marine organic matter during deposition of the mfs and the HST. The supply of landplant debris increased during the HST. Turbidites and their non-calcareous mudstone equivalents represent lowstand systems tracts deposited in low salinity environments. Terrestrial organic matter dominates in turbiditic sediments, marine organisms prevail in time-equivalent mudstones. Mudstone beneath marine bands represents transgressive systems tracts when normal marine conditions and photic zone anoxia were re-established.The mudstone lithofacies exhibits a very good to excellent potential to generate conventional mixed oil and gas. TOC content of fine-grained rocks in the turbidite lithofacies depends on the amount of detrital minerals supplied from the south. Moreover, their organic matter is gas-prone. High TOC contents and large thicknesses of the mudstone lithofacies show that the Bowland Shale Formation holds a significant shale gas/liquid potential in areas with appropriate maturity. A relatively low average HI and high clay contents may have negative effects on the shale gas potential.

Erratum to: Prognostication of hydrocarbon generative potential in the onshore and offshore Niger Delta, Nigeria using TOC content and rock-eval pyrolysis techniques

This article prognosticates the hydrocarbon generation potential of core samples from fields A, B, C and D in Niger delta, Nigeria. The objectives of this study are to characterize the quality of these core samples by organic geochemical analyses. A total of ten core samples collected from fields A, B, C and D in Niger delta were analyzed using total organic carbon (TOC) content analysis, rock-eval pyrolysis technique. The analytical results of the stud- ied core samples reveal that they have generally high total organic carbon contents (TOC), suggesting that conditions in the Niger delta favour organic matter production and preservation. There is a variation in the kerogen types and this may be attributed to the relative stratigraphic positions of the core samples within the Niger delta. The rock-eval results indicate that the samples from fields C and D contain predominantly Type II kerogen with a capacity to gen- erate oil and gas and hence have good generative potential. The samples from fields A and B contain mainly Type III kerogen and are gas-prone with moderate generative potential.

Nitrogen isotope chemostratigraphy across the Permian–Triassic boundary at Chaotian, Sichuan, South China

Nitrogen isotopic compositions of upper Permian to lowermost Triassic rocks were analyzed at Chaotian in northern Sichuan, South China, in order to clarify changes in the oceanic nitrogen cycle around the Permian–Triassic boundary (P–TB) including the entire Changhsingian (Late Late Permian) prior to the extinction. The analyzed ca. 40m thick interval across the P–TB at Chaotian consists of three stratigraphic units: the upper Wujiaping Formation, the Dalong Formation, and the lowermost Feixianguan Formation, in ascending order. The upper Wujiaping Formation, ca. 10m thick, is mainly composed of dark gray limestone with diverse shallow-marine fossils such as calcareous algae and brachiopods, deposited on the shallow shelf. In contrast, the overlying Dalong Formation, ca. 25m thick, is mainly composed of thinly bedded black mudstone and siliceous mudstone containing abundant radiolarians, deposited on the relatively deep slope/basin. Absence of bioturbation, substantially high total organic carbon contents (up to 15%), and abundant occurrence of pyrite framboids in the main part of the Dalong Formation indicate deposition under anoxic condition. The lowermost Feixianguan Formation, ca. 5m thick, is composed of thinly bedded gray marl and micritic limestone with minor fossils such as ammonoids and conodonts, deposited on the relatively shallow slope. δ15NTN values are in positive values around +1 to +2‰ in the upper Wujiaping Formation implying denitrification and/or anammox in the ocean. δ15NTN values gradually decrease to −1‰ in the lower Dalong Formation and are consistently low (around 0‰) in the middle Dalong to lowermost Feixianguan Formation. No clear δ15NTN shift is recognized across the extinction horizon. The consistently low δ15NTN values suggest the enhanced nitrogen fixation in the ocean during the Changhsingian at Chaotian. Composite profiles based on previous and the present studies demonstrate the substantial δ15N variation on a global scale in the late Permian to earliest Triassic; a systematic δ15N difference by low and high latitudes is particularly clarified. Although the enhanced nitrogen fixation throughout the Changhsingian at Chaotian was likely a regional event in northwestern South China, the composite δ15N profiles imply that the sea area in which fixed nitrogen is depleted has gradually developed worldwide in the Changhsingian, possibly acting as a prolonged stress to shallow-marine biota.

The composition and its impact on the methane sorption of lacustrine shales from the Upper Triassic Yanchang Formation, Ordos Basin, China

The organic geochemistry, mineralogy and methane sorption of lacustrine shales of the Upper Triassic Yanchang Formation, collected from the south-eastern Ordos Basin, were investigated to characterize them and clarify the effects of shale composition on their sorbed gas capacity. These Yanchang shales have recently been selected as a target area for shale gas exploration in typical terrestrial strata in China. The two main sections of these shales containing type II organic matters, Chang 7 and Chang 9, have relatively high total organic carbon content (TOC) of 2–10%. The two shales also have similar mineralogies, mainly comprising quartz, clay minerals and feldspars. Both the Chang 7 and Chang 9 shales are generally in the oil window; Chang 9 is slightly more mature than Chang 7. Higher methane sorption capacity was observed for Chang 9 than for Chang 7 shales, determined on a dried basis at 50 °C. Methane sorption measurements were further performed on three samples from which the residual bitumen had been extracted, and their corresponding kerogen fractions, to gain insight into the effects of shale composition on methane sorption. This was significantly higher in solvent-extracted samples than in raw samples, indicating that residual bitumen largely restricts methane sorption on such shales. A positive correlation between the amount of clay minerals and methane sorption capacity of bulk rocks was evident, suggesting that clay mineral content is relevant to methane sorption. This result was also supported by the much higher methane sorption capacity of solvent-extracted shales compared to the extracted kerogen from those shales, when measured sorption data was normalized to TOC values. The effects of both residual bitumen and clay mineral on the methane sorption of bulk rocks have complicated the evaluation of methane sorption on organic matter in these mature shales.

Spatial and temporal heterogeneity in the distribution of an Antarctic amphipod and relationship with the sediment

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 502:169-183 (2014) - DOI: https://doi.org/10.3354/meps10715 Spatial and temporal heterogeneity in the distribution of an Antarctic amphipod and relationship with the sediment Helena P. Baird1,2,*, Jonathan S. Stark1 1Terrestrial and Nearshore Ecosystems Theme, Australian Antarctic Division, Kingston, Tasmania 7050, Australia 2Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania 7001, Australia *Corresponding author: hpbaird@utas.edu.au ABSTRACT: The nearshore Antarctic environment is subject to increasing anthropogenic impact, yet the ecological processes influencing some of its most dominant species remain poorly understood. We examined patterns of the distribution and abundance of the Antarctic amphipod Orchomenella franklini in relation to the local environment. Samples of benthic sediment were collected in East Antarctica across several spatial and temporal scales and were analysed for the abundance of O. franklini and various sediment properties. O. franklini was found to reach extremely high densities (>41000 m-2), yet abundance was strongly heterogeneous on all spatial scales tested. Temporal variation in abundance was also significant and was location-specific, potentially reflecting fluctuations in food supply and variable conditions resulting from ice disturbance. Principal component analysis and generalised additive modelling revealed evidence of a relationship between the distribution of O. franklini and the sediment, which was consistent with its deposit-feeding trophic niche. Generally, the abundance of O. franklini increased with decreasing sediment grain size and increasing trace element concentration. Abundance also peaked at high (though not maximum) total organic carbon content. This is one of the first empirical demonstrations of a correlation between discrete physical sediment traits and the abundance of an infaunal benthic species in the Antarctic, with evidence consolidated from 2 geographic regions. The influence of local conditions on the abundance of O. franklini provides insight on the heterogeneity of Antarctic benthic ecosystems. KEY WORDS: Benthic sediment · Peracarid crustacean · Population density · Metals · Grain size · Anthropogenic impact · Environmental change Full text in pdf format Supplementary material PreviousNextCite this article as: Baird HP, Stark JS (2014) Spatial and temporal heterogeneity in the distribution of an Antarctic amphipod and relationship with the sediment. Mar Ecol Prog Ser 502:169-183. https://doi.org/10.3354/meps10715 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 502. Online publication date: April 15, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

Distribution, chemical speciation and source of trace elements in surface sediments of the Changjiang Estuary

To evaluate biogeochemical characteristics, eco-environmental risks and sources of trace elements (TEs: As, Hg, Se, Sb, Te, Sn, Bi and Ge), their total concentrations and chemical speciation in surface sediments collected from the Changjiang Estuary were determined. Total concentrations for As, Hg, Se, Sb, Te, Sn, Bi and Ge were 4.57–30.20, 0.01–0.40, 0.04–0.38, 0.36–1.48, 0.02–0.10, 0.48–6.58, 0.13–0.64 and 0.83–2.43 μg/g, respectively, with higher values at the estuary. This distribution pattern was attributed to the riverine input and high clay and total organic carbon contents. The sequential extraction suggested that TEs mainly occurred in residual fractions. The risk assessment code suggested that As, Hg and Sn were at low risk, whereas Bi, Se, Sb, Te and Ge were at medium risk. The geoaccumulation index (Igeo) and principal component analysis indicated that Se and Sn mainly came from the natural input (crustal and biological inputs), whereas As, Sb, Hg, Bi and Te came from both of the crustal and anthropogenic inputs via atmosphere and rivers. In addition, Ge possibly came from the natural (crustal and biological inputs) and anthropogenic inputs.

A mineralogical and organic geochemical overview of the effects of Holocene changes in Amazon River flow on three floodplain lakes

A synthesis of the impacts of the Amazon River hydrological changes on the sedimentation process of organic matter (OM) in three different floodplain lakes (Santa Ninha, Maracá, and Comprido lakes) is presented in this study. Today the Santa Ninha and Maracá lakes are directly and permanently connected with the main channel of the Amazon River, in contrast to Comprido Lake, which is indirectly and periodically influenced by the Amazon River due to its greater distance from the main channel. All three lake sediment records showed a reduced river inflow due to dry climatic conditions during the early and middle Holocene followed by an increased fluvial input during the wetter late Holocene. In Santa Ninha and Maraca Lakes, the reduced river inflow period was recorded by sediments with a low abundance of smectite (on average ~20wt.%), a clay mineral mainly transported by the fluvial system, high total organic carbon (TOC) contents (on average ~8.2wt.%), and a predominantly acidic soil OM input evidenced by high concentrations (on average 180μggTOC−1) of branched glycerol dialkyl glycerol tetraethers (GDGT). During the late Holocene, a higher smectite abundance (on average ~43 wt.%) and a lower TOC content (on average ~1.4 wt.%) pointed to greater dilution by riverine lithogenic matter. This change was accompanied by a proportional increase in the aquatically produced crenarchaeol, suggesting a higher lake water level. In Comprido Lake, a sedimentation gap occurred during the early and middle Holocene. The wetter late Holocene, since 3000calyears BP, was characterized by high TOC values (on average ~9wt.%) and a sharp increase in soil OM input as recorded by an increase in branched GDGT concentrations (on average ~81μggTOC−1), but the smectite content was low (on average ~14%). This combination suggests that the soil OM input to Comprido Lake from the local catchment area became dominant during the wet-climate late Holocene due to the large distance of the lake from the Amazon River main channel. Consequently, our study shows that the sedimentation processes of OM in Amazonian floodplain lakes were strongly influenced by variations in the hydrodynamic regime of the Amazon River during the Holocene. However, the impacts of the variations on the three floodplain lakes were different depending on the distance of each lake from the main channel of the Amazon River.

Uptake kinetics of five hydrophobic organic pollutants in the earthworm Eisenia fetida in six different soils

Hydrophobic organic contaminants in soils may pose toxicity or transfer to food chains after their uptake to soil biota. However, uptake data for earthworms are usually limited, as: (a) only fixed exposure times are studied instead of whole uptake kinetics and (b) studies including compounds with different environmental properties and more than two soils of different properties are quite rare. In our study, five persistent organic pollutants (phenanthrene, pyrene, lindane, p,p’-dichlorodiphenyltrichloroethane (p,p’-DDT), and polychlorinated biphenyl congener No. 153 (PCB 153)) were added to six soils of a wide range of soil properties. Detailed kinetics of uptake to earthworms Eisenia fetida were measured. Results indicated that an equilibrium of concentrations for p,p’-DDT and PCB 153 was reached after 11 days of exposure in all soils. Uptake of phenanthrene, pyrene, and lindane was strongly influenced by the decrease in concentrations in the soils, resulting in peak-shaped accumulation curves. Only in soils with the highest total organic carbon content (7.9 and 20.2%), the equilibrium of lindane concentrations was achieved (after 17 and 5 days of exposure, respectively). We recommend calculating bioaccumulation factors as a ratio of the uptake and elimination rate constants to precise the risk assessment.

Anthropogenic effect on deposition dynamics of lake sediments based on 137Cs and 210Pbex techniques in Jiuzhaigou National Nature Reserve, China

Radionuclide dating techniques characterized by 137Cs and 210Pbex have recently been applied in the study of lake sediments around the world. In this study, a chronological series of sediment cores was established based on 137Cs and 210Pbex analyses along with the evaluation of sediment properties, such as particle size distribution, total organic carbon (TOC), carbonate content, and acid-insoluble residue, to study sediment accumulation rates, sediment sources, and responses to human activities in the Jiuzhaigou National Nature Reserve in southwestern China. In terms of the particle size distribution of sediments, silt content was the highest, and clay and sand contents were relatively low. The sediments displayed high TOC contents because of the significant amounts of vegetation grown in the lakes. The carbonate content was also high due to the overall geological background of carbonates in Jiuzhaigou. Carbonate content tended to decline from top to bottom in the sediment cores, whereas the acid-insoluble residue tended to increase. These results suggested that the depth variation of the environmental parameters of the sediments in two lakes in Jiuzhaigou would correspond to each other. The results indicated that the sediment rate of Jiuzhaigou was generally high with strong siltation, indicating that serious soil loss was induced by intensive human activities in the basin over the past decades. The increases in the mass accumulation rate, contents of acid-insoluble residue, and mean particle size during the periods of 1840–1900s, late 1930s-early 1950s, 1966–1978, and 2003–2006 revealed the occurrence of severe soil and water loss as a result of extensive agricultural expansion, large-scale deforestation, and road construction in Jiuzhaigou. The deposition rate and the properties of lacustrine sediments could reflect the significant impact of human activities on lake sedimentation during Jiuzhaigou’s history.

Spatial Distributions of Humic Substances and Evaluation of Sediment Organic Index on Lake Dalinouer, China

The aim of this study is to examine and interpret the spatial distribution of sedimentary humic substances in Lake Dalinouer. Humic substances in sediments were analyzed separately in different fractions: humins (HM), humic acid (HA), fulvic acid (FA), and different forms of organic carbon. The results showed that total organic carbon (TOC) contents varied from 7.25 to 65.54 g kg−1 with a mean of 36.37 ± 17.74 g kg−1. It was found that high TOC concentrations were at lake’s center and low TOC concentrations occurred at the estuary of inflows. Different redox conditions caused by water depth were of the most important factors which might influence TOC contents. Concentrations of HM, HA, and FA in sediments were detected in range of 6.40–58.16 g kg−1, 0.27–3.50 g kg−1, and 0.27–4.26 g kg−1, respectively. Of them, HM was the dominant form and accounted for 74–94% of TOC and 80–90% of humus. Organic Sediment Index (OSI) was used to assess the organics accumulation, and the value of OSI ranged from 0.001 to 0.30, which indicated that Lake Dalinouer was relatively clean. The relative high degree of humidification was found in the eastern of lake, where it should be taken into consideration seriously.

Microstructural characterisation of organic-rich shale before and after pyrolysis

Organic-rich shales, traditionally considered as source rocks, have recently become an ambitious goal for the oil and gas industry as important unconventional reservoirs. Understanding of the initiation and development of fractures in organic-rich shales is crucially important as fractures could drastically increase the permeability of these otherwise low-permeable rocks. Fracturing can be induced by rapid decomposition of organic matter caused by either natural heating, such as emplacement of magmatic bodies into sedimentary basins, or thermal methods used for enhanced oil recovery. In this work the authors study fracture initiation and development caused by dry pyrolysis of Kimmeridge shale, which is characterised with a high total organic carbon content of more than 20%. X-ray diffraction (XRD) analysis exhibits high carbonate (both calcite and dolomite) and low clay (illite) content. Field emission gun scanning electron microscopy (FEG-SEM) shows that kerogen is presented either as a load-bearing matrix or as a filling of the primary porosity with pores being of micron size. Cylindrical samples of the Kimmeridge shale are heated up to temperatures in the range of 330–430°C. High-resolution X-ray microtomographic (micro-CT) images are obtained. The microtomographic images are processed using AVIZO (Visualization Sciences Group) to identify and statistically characterise large kerogen-filled pores and pre-existing and initiated cracks. The relationship between the total area of fractures and the temperature experienced by the sample has been obtained. Total organic carbon content is determined for samples subjected to heating experiments. This approach enables a quantitative analysis of fracture initiation and development in organic-rich shales during heating.

Factors affecting the formation of disinfection by-products during chlorination and chloramination of secondary effluent for the production of high quality recycled water

During the production of high quality recycled water by reverse osmosis membrane filtration secondary effluent must be disinfected to limit biofouling on the membrane surface. Advanced Water Treatment Plants in South East Queensland, Australia use disinfectant contact times ranging from 30 min up to 24 h. Disinfectants such as chlorine and chloramines react with effluent organic matter to generate disinfection by-products (DBPs) which could be potentially hazardous to human health if the water is destined for supplementing public water supplies. In this context, secondary effluents are of concern because of their high total organic carbon content which can act as DBP precursors. Also, effluent organic matter may form different DBPs to those formed from natural organic matter during conventional drinking water treatment, either in quantity, identity or simply in the abundance of different DBPs relative to each other. It cannot be assumed per se with certainty that DBP formation will be affected in the same way by operational changes as in drinking water production.Response surface modelling has been employed in this study at the bench scale to investigate the effect of reaction time (0–24 h), pH (5.5–8.5), temperature (23–35 °C), disinfection strategy (chlorine vs chloramines used prior to membrane treatment) and the interaction between these different parameters on DBP formation during disinfection of secondary effluent.The concentration of halogenated DBPs formed during the first 24 h of reaction with the different disinfectants followed the order chlorination >> in line-formed monochloramine > pre-formed monochloramine. Contact time with chlorine was the major influencing factor on DBP formation during chlorination, except for the bromine-containing trihalomethanes and dibromoacetonitrile for which pH was more significant. Chlorination at high pH led to an increased formation of chloral hydrate, trichloronitromethane, dibromoacetonitrile and the four trihalomethanes while the opposite effect was observed for the other targeted DBPs. Temperature was identified as the least influencing parameter compared to pH and reaction time for all DBPs in all the disinfection strategies, except for the formation of chloral hydrate where pH and temperature had a similar significance and bromoform that was similarly affected by temperature and reaction time. Chloramines employed at pH 8.5 reduced the concentration of all studied DBPs compared to pH 5.5. Furthermore, reaction time was the most significant factor for trichloronitromethane, chloroform, trichloroacetonitrile, dichloroacetonitrile and bromochloroacetonitrile formation while pH was the most influencing factor affecting the formation of the remaining DBPs.

Fractal characteristics of shales from a shale gas reservoir in the Sichuan Basin, China

Nanopore structure greatly affects gas adsorption and transport in shales. Such structures in shale samples from the Lower Cambrian strata of the Sichuan Basin of China have been investigated using X-ray diffraction, total organic carbon content (TOC) tests, porosity and permeability tests, nitrogen adsorption, and methane adsorption experiments. Fractal dimensions were obtained from the nitrogen adsorption data using the Frenkel–Halsey–Hill method. The relationships between TOC, clay minerals, pore structure parameters and fractal dimension have been investigated. Based on the physical description of the fractal surfaces, the impact of fractal dimension on adsorption capacity has also been discussed. The results showed that the shale samples had fractal geometries with fractal dimensions ranging from 2.68 to 2.83. The organic matter is a controlling factor on fractal dimension, shown by positive correlation between TOC and fractal dimension. Fractal dimension increases with increasing surface area and pore volume, and also increases with decreasing pore diameter because of the complicated pore structure. Micropores have a greater impact on fractal dimension than mesopores and macropores. A negative correlation between fractal dimension and permeability was observed, especially for shales with high TOC and micropores counts. The fractal dimension can be used to evaluate adsorption capacity. Shale samples with larger fractal dimensions have higher methane adsorption capacity. Fractal analysis leads to a better understanding of the pore structure and adsorption capacity of a shale gas reservoir.