Amount Of Total Organic Carbon Research Articles

Using Thermogravimetry as a Simple Tool for Nutrient Assessment in Fire Affected Soils

AbstractNutrient availability can be a limiting factor in the recovery of ecosystems after wildfire. Its evaluation is therefore critical for selecting appropriate restoration strategies in the post‐fire period. This study explores, for the first time, the use of thermogravimetry (TG) as a rapid proxy for nutrient availability and soil recovery. Soil samples from five burned and unburned sites in Andisols of Tenerife (Spain) were selected to examine the medium‐term impact of fire. Key soil chemical parameters [pH, electric conductivity, cation exchange capacity (CEC), main cation and anions in the soil solution, total organic carbon (TOC), total nitrogen (TN) and available phosphorus] were determined and thermogravimetry performed. Burned soils showed significantly higher pH, Ca2+ and Mg2+ and a lower CEC, TOC and TN than the unburned counterparts, and a site‐dependent response for soluble SO42− and available phosphorus was observed in the medium term. Time elapsed since fire could have masked additional fire impacts. Thermogravimetry data allowed reasonable prediction of most soil properties and parameters, with r2 ranging from 0·4 to 0·9. The results demonstrate that soluble nutrient content is directly related to the amount of ash in the soil. The decrease of labile carboxyl‐C was associated with an increase of pH and decrease of CEC, whereas the increase of recalcitrant and refractory pools was associated with the amount of TOC and TN. The results suggest that this novel application of an established method can provide, following an initial calibration step, rapid and inexpensive proxies for key parameters necessary for assessing fire‐induced ecosystem degradation and designing suitable restoration strategies in the post‐fire period. Copyright © 2017 John Wiley & Sons, Ltd.

The resistance of centennial soil charcoal to the “Walkley-Black” oxidation

The “Walkley-Black” oxidation with dichromate is a routine protocol for the estimation of soil organic carbon (SOC) content. Dichromate oxidation is also used to quantify black carbon (BC) in soil and sediments based on the larger resistance of BC to dichromate oxidation than uncharred SOC. The aim of this study was (i) to evaluate whether dichromate-based SOC quantification methods discriminate between uncharred SOC and charcoal residues in the topsoil of pre-industrial charcoal kiln sites and (ii) to test the influence of aging on the recovery of charcoal by dichromate oxidation. We selected 40 topsoil samples from 20 pre-industrial charcoal kiln sites of Wallonia, Belgium, and adjacent reference soils unaffected by charcoal production. Samples included soils from forest and cropland, with a diversity of soil types and textural classes. SOC content was estimated by the original Walkley-Black procedure (results were multiplied by the traditional correction factor of 1.32), and by an adapted method that includes external heating of the digestion mixture to overcome incomplete oxidation of uncharred SOC and get rid of the correction factor of 1.32. Results were compared to the amount of total organic carbon (TOC) content, measured by dry combustion, and to the content of charcoal-C in soil, estimated by differential scanning calorimetry. The soil of a currently active charcoal kiln site was also analyzed and used as a reference subject to limited aging. 23.6% of charcoal-C was recovered by the Walkley-Black procedure in the soil of the currently active kiln site against 65% for the soil of pre-industrial kiln sites, which indicates that the resistance of charcoal to dichromate oxidation decreases with aging. The recovery of charcoal increased to 90% after boiling of the digestion mixture, providing evidence that heat catalyzes the oxidation of charcoal. The substantial oxidation of charcoal by dichromate and the variability of recovery according to the degree of alteration of charcoal and conditions of reaction support the idea that the quantification of BC based on its chemical resistance is challenging and can be subject to important biases if calibration is not adapted to the quality of BC of the sample of interest. Because the recovery of BC by the Walkley-Black method is incomplete, the presence of large amounts of BC in soils frequently affected by fire might be a significant cause of underestimation of SOC by the Walkley-Black method in regional and global databases.

Effect of in-situ recycling of sugarcane crop residues and its industrial wastes on different soil carbon pools under soybean (Glycine max) - maize (Zea mays) system

A field experiment was conducted during summer 2011-12 at MPKV Farm, Rahuri to evaluate the effect of in-situ recycling of sugarcane crop residues and its industrial wastes on soil organic C fractions like labile carbon, microbial biomass C, particulate organic C, KMnO4 extractable C, physically protected particulate organic matter carbon (POMC) and significantly improved water stable aggregates in the cultivated soil under maize (Zea mays L.)-soybean [Glycine max (L.) Merr.] system. The active carbon pools like soil microbial biomass carbon (SMBC), water soluble carbohydrates (WHC) and acid hydrolysable carbon (AHC) was significantly improved in the treatment receiving 100% recommended dose of fertilizer along with in-situ compost of crop residues, press mud cake and methanated spent wash compost compared to burning of residues. Application of in-situ sugarcane residues with pressmud incorporation retainedabout19.6%, 38.8% and 33% more amount of total organic carbon (TOC), SMBC, AHC respectively, over burning of sugarcane crop residues and removal of stubbles after harvest of maize. The mean values of WSC (43 mg/kg) and the physically protected carbon, i.e. POMC (2014 mg/kg) were greater by 47% and 6.6% respectively, in the treatment (T7) receiving in-situ residue decomposition of sugarcane crop residues in combination with equal proportion (50%) of press mud cake and biomethanated spent wash over the burning of sugarcane crop residues and removal of stubbles after harvest of maize. After harvest of maize the maximum recalcitrant fraction (humic acid) of carbon was observed in the treatment T7 (in-situ decomposition of sugarcane crop residues + 50% press-mud cake + 50% biomethenated spent wash). This study clearly indicated that resistant fraction of carbon might be accumulated more where decomposed organic matter was applied regularly. It clearly indicated that application of in-situ decomposed residues and by-products of industrial waste in combination with NPK enhanced the below and above ground biomass production, SOC stock and carbon pools.

High fragility of the soil organic C pools in mangrove forests

Mangrove forests play an important role in biogeochemical cycle of C, storing large amounts of organic carbon. However, these functions can be controlled by the high spatial heterogeneity of these intertidal environments. In this study were performed an intensive sampling characterizing mangrove soils under different type of vegetation (Rhizophora/Avicennia/dead mangrove) in the Venezuelan coast. The soils were anoxic, with a pH~7; however other soil parameters varied widely (e.g., clay, organic carbon). Dead mangrove area showed a significant lower amounts of total organic carbon (TOC) (6.8±2.2%), in comparison to the well-preserved mangrove of Avicennia or Rhizophora (TOC=17–20%). Our results indicate that 56% of the TOC was lost within a period of 10years and we estimate that 11,219kgm−2 of CO2 was emitted as a result of the mangrove death. These results represent an average emission rate of 11.2±19.17tCO2ha−1y−1.

Ecology and distribution of living ostracod assemblages in a shallow endorheic lake: the example of the Lake Trasimeno (Umbria, central Italy)

<p>Ostracod assemblages from Lake Trasimeno (Umbria, central Italy), the largest endorheic lake in Italy, were investigated relating their species distribution and ecology to modern physical, chemical and biological parameters. Nineteen living species were collected in the lake<em> </em>(<em>Darwinula stevensoni, Candona (Candona) candida, Candona (Neglecandona) angulata, Fabaeformiscandona fabaeformis, Pseudocandona marchica, Cypria ophtalmica, Ilyocypris gibba, I. salebrosa, I. getica, Cypridopsis vidua, Eucypris virens, Trajancypris clavata, Herpetocypris helenae, Heterocypris salina, H. incongruens, Isocypris beauchampi, Cyprideis torosa, Limnocythere inopinata, </em>and<em> </em><em>L. stationis</em>)<em>. </em>All the identified species belong to the fresh-water Italian ostracod fauna but<em> </em><em>Cyprideis</em> <em>torosa </em>is documented in an oligohaline athalassic lacustrine environment in Italy for the first time.<em> </em>The occurrence of<em> </em><em>Ilyocypris</em> <em>salebrosa </em>represents the southernmost record in Italy and the westernmost in Eurasia. The recovery of<em> </em><em>Limnocythere</em> <em>stationis</em> represents the westernmost record in Eurasia. The distribution of the different ostracods recovered in Lake Trasimeno is linked to the dominant physical and chemical parameters for each ecological niche. Physical and chemical data along with substratum type, grain-size and presence of aquatic macrophytes have been related to different ostracods using a multivariate analyses approach (NMDS, CCA, Spearman’s rank correlation test). These results allow to differentiate several ecological niches within the lake and indicate that the main parameters affecting the ostracod assemblages are the aquatic macrophyte coverage, the Total Organic Carbon (TOC) and, to a lesser extent, temperature and type of substrate.<em> </em><em>Cyprideis</em> <em>torosa </em>and<em> </em><em>Candona </em>(<em>Neglecandona</em>)<em> </em><em>angulata </em>have been recovered both in the distal part of the lake and in the lakeshore area. In both cases they are associated with scarce or absent aquatic macrophytes and low amounts of TOC. The<em> </em>alternate dominance of these two species in the distal deeper assemblages seems to be mainly linked with the bottom oxygen availability, being<em> </em><em>C.(N.) angulata </em>dominant in the most oxygen-depleted sediments and<em> </em><em>C. torosa </em>dominant in higher oxygen conditions.<em> </em>Along the lakeshore area they are often discovered together with other prevailing species, such as<em> </em><em>Cypridopsis</em> <em>vidua </em>that is common in very shallow to shallow<em> </em>(20-140 cm) sites with high TOC content, abundant macrophytes and algae, and Limnocythere inopinata, which dominates slightly deeper areas (around 150-210 cm) where the previous species are almost absent. The Spearman’s rank correlation test showed significant positive correlation between some ostracods and macrophyte species.</p>

TiO 2 as an effective nanocatalyst for photocatalytic degradation of humic acid in water environment

Photocatalysis with TiO 2 is used to remove humic acid (HA) in a water environment under UVA and UVC light. The effects of operating parameters, including light intensity, HA concentration, catalyst dose, and contact time are investigated at neutral pH conditions. Results show that HA degradation increases with increasing contact time and light intensity and decreases with increasing HA concentration. Increasing catalyst dose increases the HA degradation up to an optimum value. At pH 7 with an initial HA concentration of 14 mg/L, UVA light of 0.236 mW/cm 2 and catalyst dose of 0.3 g/L, 100% efficiency of the HA degradation can be achieved in 3 h. Under identical experimental conditions with UVC light of 0.284 mW/cm 2 , the efficiency of HA degradation also reaches 100%. Based on total organic carbon (TOC) analysis, the mineralization of HA is found to be lower than the degradation of HA. A negligible amount of TOC on the catalyst surface confirms that HA removal is due to photocatalysis. Moreover, a higher degree of mineralization of HA is found under UVA light although degradation is better under UVC light. This indicates that TiO 2 under UVA light has relatively low selectivity to degrade different compounds, including various intermediates from HA degradation.

Zeolite Combined with Alum and Polyaluminum Chloride Mixed with Agricultural Slurries Reduces Carbon Losses in Runoff from Grassed Soil Boxes.

Carbon (C) losses from agricultural soils to surface waters can migrate through water treatment plants and result in the formation of disinfection by-products, which are potentially harmful to human health. This study aimed to quantify total organic carbon (TOC) and total inorganic C losses in runoff after application of dairy slurry, pig slurry, or milk house wash water (MWW) to land and to mitigate these losses through coamendment of the slurries with zeolite (2.36-3.35 mm clinoptilolite) and liquid polyaluminum chloride (PAC) (10% AlO) for dairy and pig slurries or liquid aluminum sulfate (alum) (8% AlO) for MWW. Four treatments under repeated 30-min simulated rainfall events (9.6 mm h) were examined in a laboratory study using grassed soil runoff boxes (0.225 m wide, 1 m long; 10% slope): control soil, unamended slurries, PAC-amended dairy and pig slurries (13.3 and 11.7 kg t, respectively), alum-amended MWW (3.2 kg t), combined zeolite and PAC-amended dairy (160 and 13.3 kg t zeolite and PAC, respectively) and pig slurries (158 and 11.7 kg t zeolite and PAC, respectively), and combined zeolite and alum-amended MWW (72 and 3.2 kg t zeolite and alum, respectively). The unamended and amended slurries were applied at net rates of 31, 34, and 50 t ha for pig and dairy slurries and MWW, respectively. Significant reductions of TOC in runoff compared with unamended slurries were measured for PAC-amended dairy and pig slurries (52 and 56%, respectively) but not for alum-amended MWW. Dual zeolite and alum-amended MWW significantly reduced TOC in runoff compared with alum amendment only. We conclude that use of PAC-amended dairy and pig slurries and dual zeolite and alum-amended MWW, although effective, may not be economically viable to reduce TOC losses from organic slurries given the relatively low amounts of TOC measured in runoff from unamended slurries compared with the amounts applied.

IMPLEMENTING ARTIFICIAL NEURAL NETWORKS MODELLING AFTER THE TREATMENT OF OIL REFINERY EFFLUENTS USING ADVANCED OXIDATION PROCESSES

The present study aims at evaluating the treatment of polycyclic aromatic hydrocarbons (PAH) present in oil refinery effluents by advanced oxidation process (AOP), besides analysing the data obtained using artificial neural networks (ANN). The AOP process managed to degrade 10 different PAH initially found in the samples analysed. The efficiency analysis of the process was also evaluated, according to the amounts of total organic carbon (TOC). The ANN Multilayer Perceptron used consisted of 3 layers. Experimental and simulated data used in the training were compared in both trial and validation processes concluding that the amounts were very similar. The network used was able to monitor precisely the tendency of the data and the amounts of TOC, observing the correlation coefficient on both modelling strategies employed. The values of R2 were 0.994 in the first modelling, using the activation function logsig, and 0.996 in the second one, using tansig. Both modelings used the training algorithm Levenberg- Marquardt, corroborating the efficiency of the process employed.

Biodegradability of algal-derived organic matter in a large artificial lake by using stable isotope tracers.

In order to understand the biodegradability of algal-derived organic matter, biodegradation experiments were conducted with (13)C and (15)N-labeled natural phytoplankton and periphytic algal populations in experimental conditions for 60days. Qualitative changes in the dissolved organic matter were also determined using parallel factor analysis and the stable carbon isotopic composition of the hydrophobic dissolved organic matter through the experimental period. Although algal-derived organic matter is considered to be easily biodegradable, the initial amounts of total organic carbon newly produced by phytoplankton and periphytic algae remained approximately 16 and 44% after 60days, respectively, and about 22 and 43% of newly produced particulate nitrogen remained. Further, the dissolved organic carbon derived from both algal populations increased significantly after 60days. Although the dissolved organic matter gradually became refractory, the contributions of the algal-derived organic matter to the dissolved organic matter and hydrophobic dissolved organic matter increased. Our laboratory experimental results suggest that algal-derived organic matter produced by phytoplankton and periphytic algae could contribute significantly to the non-biodegradable organic matter through microbial transformations.

Spatial Variability of Soil Properties in Archeological Dark Earth Sites under Cacao Cultivation

Soils with an A horizon formed by human activity, an anthropogenic A horizon, are found in the Amazon Region. Few studies have examined the spatial distribution of the properties of these soils. We mapped the spatial variability of some soil properties in an area of Archaeological Dark Earth (ADE) in the Brazilian Amazon. A sampling grid was defined over an area of 42 × 88 m under cacao cultivation in which sampling points were established at a spacing of 6 × 8 m, for a total of 88 points. Samples were collected from the 0.00-0.05, 0.05-0.10, 0.10-0.20, and 0.20-0.30 m depth layers. Soil texture, aggregate stability, and organic carbon (OC) analyses were performed on disturbed soil samples. Undisturbed samples were used to determine soil macroporosity (Macro), microporosity (Micro), total porosity (TP), and soil resistance to penetration (RP). The results were analyzed by descriptive statistic, Pearson correlation (p<0.01), and geostatistics. Soil bulk density, total pore volume, and geometric mean diameter are dependent on the total amount of OC in the ADE area. Increased soil bulk density and RP are proportional to a decrease in OC content and lower Micro and TP. Moreover, soil resistance to penetration is influenced by soil water and clay content with depth.

Applications of standard and advanced statistical methods to TOC estimation in the McArthur and Georgina basins, Australia

Multiple potential shale-gas plays have been identified in Australia. The total estimates of recoverable dry and wet shale gas exceed 157 tcf. Technological advances and more informed estimations of total organic carbon (TOC) abundance and distribution might further increase the assessments of recoverable shale gas. TOC content is known only at the depths where laboratory measurements on recovered core samples are performed. However, reliable estimation of potential resources can be based only on information about vertical and lateral distribution in organic matter throughout the prospective gas-shale reservoir. This information commonly is obtained from conventional wireline logs such as gamma ray, density, transit time, and resistivity. Methods routinely used for these estimations were developed for organic-rich shales from Northern American basins, where organic matter of marine Type I and Type II typically is observed. In prospective Australian basins, organic matter ranges from marine Type I to terrestrial Type III. This fact, along with different depositional history of Australian reservoirs, might lead to quite different logging-tool responses. Thus, the relations between the amount of TOC and estimation from logs might be quite different.

월악산 소나무림의 유기탄소 분포와 순환을 통한 생태계서비스 가치평가

Valuation of ecosystem services through organic carbon distribution and cycling in the Pinus densiflora forest at Mt. Worak National Park were investigated from January 2013 through December 2013. The amount of carbon allocated to above and below ground biomass was 32.17 and 8.04 ton C . Amount of organic carbon in litter layer was 5.55 ton C . Amount of organic carbon within 50cm soil depth was 58.62 ton C 50cm-. Total amount of organic carbon in this Pinus densiflora forest was estimated to 104.38 ton C . The estimated amount of won in this Pinus densiflora forest in terms of total organic carbon was about 10.44 million won . The amount of carbon evolved through soil respiration was 4.44 ton C . The amount of carbon evolved through microbial respiration and root respiration was 2.18 and 2.27 ton C , respectively. The amount of organic carbon absorbed from the atmosphere of this Pinus densiflora forest was 0.44 ton C when estimated from the difference between net primary production and microbial respiration. This amount will come to about 44,000 won in Korean currency.

Budget and distribution of organic carbon in Quercus serrata Thunb. ex Murray forest in Mt. Worak

The carbon cycle came into the spotlight due to the climate change and forests are well-known for their capacity to store carbon amongst other terrestrial ecosystems. The annual organic carbon of litter production, forest floor litter layer, soil, aboveground and belowground part of plant, standing biomass, net primary production, uptake of organic carbon, soil respiration, etc. were measured in Mt. Worak in order to understand the production and carbon budget of Quercus serrata forest that are widely spread in the central and southern part of the Korean Peninsula. The total amount of organic carbon of Q. serrata forest during the study period (2010-2013) was 130.745 ton C ha^-1. The aboveground part of plant, belowground part of plant, forest floor litter layer, and organic carbon in soil was 50.041, 12.510, 4.075, and 64.119 ton C ha^-1, respectively. The total average of carbon fixation in plants from photosynthesis was 4.935 ton C ha^-1 yr^-1 and organic carbon released from soil respiration to microbial respiration was 3.972 ton C ha^-1 yr^-1. As a result, the net ecosystem production of Q. serrata forest estimated from carbon fixation and soil respiration was 0.963 ton C ha^-1 yr^-1. Therefore, it seems that Q. serrata forest can act as a sink that absorbs carbon from the atmosphere. The carbon uptake of Q. serrata forest was highest in stem of the plant and the research site had young forest which had many trees with small diameter at breast height (DBH). Consequentially, it seems that active matter production and vigorous carbon dioxide assimilation occurred in Q. serrata forest and these results have proven to be effective for Q. serrata forest to play a role as carbon storage and NEP.

A novel photoelectro-peroxone process for the degradation and mineralization of substituted benzenes in water

A novel photoelectro-peroxone (PEP) process was developed by combining conventional ozonation, UV irradiation, and electrolysis process to treat substituted benzene (nitrobenzene, chlorobenzene, and benzaldehyde) solutions. The PEP process involves electrochemically generating H2O2 from O2 in the sparged ozone generator effluent (O2 and O3 gas mixture) at a carbon-based cathode. The in-situ generated H2O2 then undergoes UV-induced photolysis and reacts with the sparged O3 to yield OH, which can rapidly and non-selectively oxidize most organic pollutants. Thanks to the enhanced OH production, the PEP process considerably increased the pseudo-first order rate constants for the degradation of the three substituted benzenes to ∼4.7–8.4 times of the simple linear combination of the individual ozonation, UV, and electrolysis processes. In addition, the PEP process was capable of removing 98% total organic carbon (TOC) from the substituted benzene solution in 15min with a specific energy consumption (SEC) of 0.66kWh (gTOCremoved)−1. In comparison, UV/O3 and electro-peroxone (EP, i.e., ozonation in combination with electro-generation of H2O2) processes took ∼90min to remove the same amount of TOC with SEC of 3.56 and 1.07kWh (gTOCremoved)−1, respectively. Furthermore, the presence of Fe2+/Fe3+ did not negatively affect TOC removal by the PEP process, whereas it decreased the efficiency of the EP process considerably. The results indicate that the PEP process can significantly improve the kinetics and energy efficiency for substituted benzene mineralization compared with conventional ozonation, UV photolysis, electrolysis, and their combined processes (UV/O3 and EP) that have been previously investigated, and may thus offer a highly effective and energy-efficient alternative for wastewater treatment.

Mechanism of hydrogen sulfide generation from a composite waste landfill site: a case study of the ‘Sudokwon Landfill Site’, Korea

This study analyzes the mechanism of hydrogen sulfide generation in a composite landfill site where demolition and domestic wastes were deposited. The total amount of organic carbon recorded during the period 2000–2014 was 11.4 times that of SO42−. The amounts of organic carbon and SO42− removed through landfill gas were 16.0 and 6.1 %, respectively, during the same period. The COD/SO42− ratio of the leachate was 10.9 in 2001, which drastically decreased to 4.5 in 2007 by the increase in CH4 concentration; thereafter, no great variations in this ratio were observed up to 2014. It was found that the concentration of H2S sharply increased after methane concentrations reached their highest levels. The year around 2006 may be the equilibrium time point among the waste supply, LFG generation, and leachate water quality. In conclusion, if the ratio of landfill organic carbon to SO42− is about 10, and the COD/SO42− ratio is about 9 in the state of equilibrium, there appears to be no hindrance to the generation of CH4 and H2S.

Study on the leachable behavior of cation exchange resins

The amount of total organic carbon (TOC) leached from cation exchange resins (CERs) in condensate demineralizers are related to the quality of reactor water in nuclear power plants (NPPs). In the recent years, quality problems of CERs used by ChinShan and KuoSheng NPPs have been identified. Prior to use, TOC and sulfate concentrations must be reduced to meet the criteria; however, this involves an extended purification process and heavy use of water resources. Even in cases where resin can be used, the quality of the water in the reactor remains poor. This study, therefore, investigated the leachates of resins from these NPPs in order to establish a reference for the quality of deep bed CERs. Gel permeation chromatography and ion-pair chromatography were used to identify molecular peaks in the CER leachates in order to elucidate the molecular distributions. We also sought to determine TOC and sulfate concentrations of post-UV treatment using long-term soaking tests, in which the solutions used to soak resins were drained off for analysis on a daily basis. Hydrogen peroxide is employed to accelerate the aging process associated with decomposition in soaking tests to determine the stabilities of the resins.

Carbon storage in a Holocene deltaic sequence: An example from the Nobi Plain, central Japan

We estimated the rate of accumulation and total amount of organic carbon (OC) stored in Holocene sediments of the Nobi Plain of central Japan by analyzing 2701 existing borehole sections and 218 14C ages, reconstructing the three-dimensional stratigraphic architecture of the delta system, calculating the volume of sediments in the delta, and using OC contents measured from sediments from eight boreholes on the plain. We calculated that a total of 167 Tg of OC was stored in deltaic deposits on the plain during the past 6000 years. A dramatic increase in the amount of stored OC since 1000 cal BP is probably a combined result of increases in sediment supply to the delta in response to human activities in the drainage basin and expansion of the area of subaerial delta as a result of progradation. OC accumulation rates for the Nobi Plain during the past 6000 years ranged from 15.3 to 37.5 g m−2 y−1, which are comparable to rates obtained from other Holocene delta, and to rates from floodplain and lake systems with higher OC contents in their sediments. The higher sedimentation rates of the deltaic deposits compensates for their lower OC contents.

Depositional environment and hydrocarbon potential of the Middle Triassic strata of the Sverdrup Basin, Canada

This study summarizes the results of petrographic and geochemical analysis of Middle Triassic strata from the Sverdrup Basin in the Canadian Arctic. In this work, we investigate the distribution and depositional conditions of dispersed organic matter (OM) as a preliminary step towards understanding the potential of this stratigraphic interval as an unconventional reservoir. Closely-spaced samples from three Middle Triassic cores (southern margin, basin centre, northern margin) are analyzed using Rock-Eval analysis, inductively coupled plasma-mass spectrometry (ICP-MS), and organic petrology. Total organic carbon (TOC) ranges between 0 and 4.8wt.%, with the most organic-rich interval having a median TOC value of 3.2wt.%. Kerogen type varies from Type II to Type III throughout the sampled intervals. Samples from near the top of the regressive systems tract of the Anisian 3rd order sequence (basin centre) and near the middle of the Ladinian 3rd order sequence (southern margin) contain predominantly reworked, highly oxidized macerals and abundant coarser clastic material. Results support oxic to suboxic depositional conditions for these intervals. By contrast, samples from near the base of regressive systems tracts of both sequences (basin centre and northern margin) have the highest amounts of TOC (i.e., median=3.2wt.% and 1.4wt.%), containing retained migrabitumen and abundant labile primary kerogen, respectively. The base of the Ladinian regressive systems tract near the basin axis was deposited under anoxic conditions and can be considered a prospective shale oil interval. Small-scale cyclic clastic influx episodes along the northern margin of the basin show changes from oxic to suboxic bottom waters. These cycles may be considered evidence for northerly-derived sediment from Crockerland during the Middle Triassic. The results and interpretations of this study can be applied to analogous fine-grained successions in other basins to better understand their unconventional reservoir potential.

Brittleness evaluation of resource plays by integrating petrophysical and seismic data analysis

The main considerations for well planning and hydraulic fracturing in unconventional resources plays include the amount of total organic carbon and how much hydrocarbon can be extracted. Brittleness is the direct measurement of a formation about the ability to create avenues for hydrocarbons when applying hydraulic fracturing. Brittleness can be directly estimated from laboratory stress-strain measurements, rock-elastic properties, and mineral content analysis using petrophysical analysis on well logs. However, the estimated brittleness using these methods only provides “cylinder” estimates near the borehole. We proposed a workflow to estimate brittleness of resource plays in 3D by integrating the petrophysics and seismic data analysis. The workflow began by brittleness evaluation using mineral well logs at the borehole location. Then, we used a proximal support vector machine algorithm to construct a classification pattern between rock-elastic properties and brittleness for the selected benchmark well. The pattern was validated using well-log data that were not used for constructing the classification. Next, we prestack inverted the fidelity preserved seismic gathers to generate a suite of rock-elastic properties volumes. Finally, we obtained a satisfactory brittleness index of target formations by applying the trained classification pattern to the inverted rock-elastic-property volumes.

Spatial and temporal variations of organic matter contents and potential sediment nutrient index in the Sundarbans mangrove forest, Bangladesh

This paper has investigated the total organic carbon contents together with total nitrogen, total phosphorous, electrical conductivity and grain size parameters of the surface sediments of the Sundarbans mangrove forest in Bangladesh. The results showed that the seasonal variations of Total Organic Carbon (TOC) and Total Nitrogen (TN) were significant at all sampling points. TOC and TN content at the monsoon were quite higher than that of the winter season. TOC and TN also showed strong positive correlations between them and negatively correlated with Total Phosphorus (TP). Depending on the distributions of TOC and TN, the studied forest ranges could be arranged at the following order: Sarankhola and Chandpai ranges > Khulna range > Satkhira range. In contrast, TP content showed the reverse order of TOC and TN, where the higher concentrations were generally distributed at the southern parts of Sundarbans. Besides, TOC and TN showed linear positive correlations with grain size distribution where fine grained sediments contain higher amount of TOC and TN. However, in terms of grain size variation, TP reversed the results of TOC and TN. Thus “grain size effect” was an important factor for influencing the distributions of sediment nutrients. Carbon-Nitrogen (C/N) ratios showed the highest contribution of terrestrial organic carbon near the Sarankhola and Chandpai ranges were iso-lines projecting towards northeast, indicating the influence of the upstream river water. Sediment Nutrient Indexes (SNI) were low, although reasonably variable, in forest floor directly receiving effluents from other anthropogenic sources/farms. It was evident that potential nutrient levels changed from the high values at northeast sites to the southwest sites, and this pattern was common across the four forest ranges.