A review of physicochemical properties of dissolved organic carbon and its impact over mountain glaciers

Investigating the characteristics and transformation of water-soluble carbonaceous matter in the cryosphere regions is important for understanding biogeochemical process in the earth system.Water-soluble carbonaceous matter is a heterogeneous mixture of organic compounds that is soluble in aquatic environments.Despite its importance,we still lack systematic understanding for dissolved organic carbon(DOC)in several aspects including exact chemical composition and physical interactions with microorganisms,glacier meltwater.This review presents the chemical composition and physical properties of glacier DOC deposited through anthropogenic emission,terrestrial,and biogenic sources.We present the molecular composition of DOC and its effect over snow albedo and associated radiative forcings.Results indicate that DOC in snow/ice is made up of aromatic protein-like species,fulvic acid-like materials,and humic acid-like materials.Light-absorbing impurities in surface snow and glacier ice cause considerable albedo reduction and the associated radiative forcing is definitely positive.Water-soluble carbonaceous matter dominated the carbon transport in the high-altitude glacial area.Owing to prevailing global warming and projected increase in carbon emission,the glacial DOC is expected to release,which will have strong underlying impacts on cryosphere ecosystem.The results of this work have profound implications for better understanding the carbon cycle in high altitude cryosphere regions.A new compilation of globally distributed work is required,including large-scale measurements of glacial DOC over high-altitude cryosphere regions,to overcome and address the scientific challenges to constrain climate impacts of light-absorbing impurities related processes in Earth system and climate models.

Total organic carbon content logging prediction based on machine learning:A brief review

The total organic carbon content usually determines the hydrocarbon generation potential of a formation.A higher total organic carbon content often corresponds to a greater possibility of generating large amounts of oil or gas.Hence,accurately calculating the total organic carbon content in a formation is very important.Present research is focused on precisely calculating the total organic carbon content based on machine learning.At present,many machine learning methods,including backpropagation neural networks,support vector regression,random forests,extreme learning machines,and deep learning,are employed to evaluate the total organic carbon content.However,the principles and perspectives of various machine learning algorithms are quite different.This paper reviews the application of various machine learning algorithms to deal with total organic carbon content evaluation problems.Of various machine learning algorithms used for TOC content predication,two algorithms,the backpropagation neural network and support vector regression are the most commonly used,and the backpropagation neural network is sometimes combined with many other algorithms to achieve better results.Additionally,combining multiple algorithms or using deep learning to increase the number of network layers can further improve the total organic carbon content prediction.The prediction by backpropagation neural network may be better than that by support vector regression;nevertheless,using any type of machine learning algorithm improves the total organic carbon content prediction in a given research block.According to some published literature,the determination coefficient(R^(2))can be increased by up to 0.46 after using machine learning.Deep learning algorithms may be the next breakthrough direction that can significantly improve the prediction of the total organic carbon content.Evaluating the total organic carbon content based on machine learning is of great significance.

Effect of Different Irrigation Methods on Dissolved Organic Carbon and Microbial Biomass Carbon in the Greenhouse Soil

The objective of this study was to investigate the contents and distribution of dissolved organic carbon （DOC） and microbial biomass carbon （MBC） at 0-100 cm soil depth under three irrigation treatments, viz., subsurface, drip and furrow irrigation in the greenhouse soil. The soil samples were collected at different depths （0-100 cm）, and the contents of soil total organic carbon （TOC）, DOC and MBC were analysed. The experiment was conducted for 10 yr, during which period the application of fertilizers and crop management practices were kept identical. The results showed that the contents of TOC, DOC and MBC were significantly affected by different irrigation regimes, decreased with the increase of soil depth. TOC at 0-10 and 80-100 cm soil depths followed the order of furrow irrigation 〉 subsurface irrigation 〉 drip irrigation, whereas at the depth of 10-80 cm followed the order of subsurface irrigation 〉 furrow irrigation 〉 drip irrigation. DOC and MBC contents at 0-100 cm soil depths followed the order of furrow irrigation 〉 drip irrigation 〉 subsurface irrigation, and drip irrigation 〉 furrow irrigation 〉 subsurface irrigation, respectively. The ratios of DOC and MBC to TOC accounted for 4.98-12.87% and 1.48-2.82%, respectively, which were the highest in the drip irrigation treatment, followed were in the furrow irrigation treatment, and the lowest in subsurface irrigation treatment. There were significant positive correlations among the contents of DOC, MBC and TOC in all irrigation treatments. The furrow irrigation facilitated the accumulation of TOC and DOC, while drip irrigation increased the MBC. The content of TOC and the ratios of DOC to TOC were the lowest in subsurface irrigation treatment.

Temporal and Spatial Variability of Dissolved Organic Carbon Concentration in the Xijiang River, South China

A whole year analysis of riverine dissolved organic carbon (DOC) concentrations in the Xijiang River (XJR), South China, showed that the mean riverine DOC concentration (1.24 mg L-1) in the XJR was notably lower than the averaged value (5.75 mg L-1) of the global riverine DOC concentration in several major rivers. There is an inconspicuous monthly fluctuation of the DOC signal in the XJR, but on a semi-yearly time scale, however, the riverine DOC concentration had significant difference between hydrological seasons. The DOC level during the flood season (1.18 mg L-1) was less than that during the non-flood season (1.40 mg L-1). Owing to the concomitance of the flushing and dilution effects of the runoff during the high-water period, the variation of riverine DOC concentration with discharge in the XJR differed from that reported in many other major rivers. The DOC export flux above the city of Wuzhou was about 0.62× 106 g C km-2 yr-1. The DOC transported during the "056" Massive Flood period comprised 30.35% of the annual total, while the discharge accounted for 36.32% of the total annual flow. The characteristics in riverine DOC concentration in the XJR were attributed to the combined effect of the geomorphologic, monsoon climatic and hydrological processes as well as land-use within the drainage basin.

An improved method for quantitatively measuring the sequences of total organic carbon and black carbon in marine sediment cores

Understanding global carbon cycle is critical to uncover the mechanisms of global warming and remediate its adverse ef fects on human activities.Organic carbon in marine sediments is an indispensable part of the global carbon reservoir in global carbon cycling.Evaluating such a reservoir calls for quantitative studies of marine carbon burial,which closely depend on quantifying total organic carbon and black carbon in marine sediment cores and subsequently on obtaining their high-resolution temporal sequences.However,the conventional methods for detecting the contents of total organic carbon or black carbon cannot resolve the following specific difficulties,i.e.,(1)a very limited amount of each subsample versus the diverse analytical items,(2) a low and fluctuating recovery rate of total organic carbon or black carbon versus the reproducibility of carbon data,and(3)a large number of subsamples versus the rapid batch measurements.In this work,(i)adopting the customized disposable ceramic crucibles with the microporecontrolled ability,(ii)developing self-made or customized facilities for the procedures of acidification and chemothermal oxidization,and(iii)optimizing procedures and carbon-sulfur analyzer,we have built a novel Wang-Xu-Yuan method(the WXY method)for measuring the contents of total organic carbon or black carbon in marine sediment cores,which includes the procedures of pretreatment,weighing,acidification,chemothermal oxidation and quantification;and can fully meet the requirements of establishing their highresolution temporal sequences,whatever in the recovery,experimental efficiency,accuracy and reliability of the measurements,and homogeneity of samples.In particular,the usage of disposable ceramic crucibles leads to evidently simplify the experimental scenario,which further results in the very high recovery rates for total organic carbon and black carbon.This new technique may provide a significant support for revealing the mechanism of carbon burial and evaluating the capacity of marine carbon accumulation and sequestration.

Distribution characteristics of dissolved organic carbon in annular wetland soil-water solutions through soil profiles in the Sanjiang Plain,Northeast China

Overwhelming evidence reveals that concentrations of dissolved organic carbon （DOC） have increased in streams which brings negative environmental impacts. DOC in stream flow is mainly originated from soil-water solutions of watershed. Wetlands prove to be the most sensitive areas as an important DOC reserve between terrestrial and fluvial biogeosystems. This reported study was focused on the distribution characteristics and the controlling factors of DOC in soil-water solutions of annular wetland, i.e., a dishing wetland and a forest wetland together, in the Sanjiang Plain, Northeast China. The results indicate that DOC concentrations in soilwater solutions decreased and then increased with increasing soil depth in the annular wetland. In the upper soil layers of 0-10 cm and 10-20 cm, DOC concentrations in soil-water solutions linearly increased from edge to center of the annular wetland （R^2 = 0.3122 and R^2 = 0.443）. The distribution variations were intimately linked to DOC production and utilization and DOC transport processes in annular wetland soil-water solutions. The concentrations of total organic carbon （TOC）, total carbon （TC） and Fe（II）, DOC mobility and continuous vertical and lateral flow affectext the distribution variations of DOC in soil-water solutions. The correlation coefficients between DOC concentrations and TOC, TC and Fe（II） were 0.974, 0.813 and 0.753 respectively. These distribution characteristics suggested a systematic response of the distribution variations of DOC in annular wetland soil-water solutions to the geometry of closed depressions on a scale of small catchments. However, the DOC in soil pore water of the annular wetland may be the potential source of DOC to stream flow on watershed scale. These observations also implied the fragmentation of wetland landscape could bring the spatial-temporal variations of DOC distribution and exports, which would bring negative environmental impacts in watersheds of the Sanjiang Plain.

Microbial Biomass Carbon and Total Organic Carbon of Soils as Affected by Rubber Cultivation

Soil samples were collected from different rubber fields in twenty-five plotsselected randomly in the Experimental Farm of the Chinese Academy of Tropical Agriculture Scienceslocated in Hainan, China, to analyse the ecological effect of rubber cultivation. The results showedthat in the tropical rubber farm, soil microbial biomass C (MBC) and total organic C (TOC) wererelatively low in the content but highly correlated with each other. After rubber tapping, soil MBCof mature rubber fields decreased significantly, by 55.5 percent. compared with immature rubberfields. Soil TOC also decreased but the difference was not significant. Ratios of MBC to TOCdecreased significantly. The decreasing trend of MBC stopped at about ten years of rubbercultivation. After this period, soil MBC increased relatively while soil TOC still kept indecreasing. Soil MBC changes could be measured to predict the tendency of soil organic matterchanges due to management practices in a tropical rubber farm several years before the changes insoil TOC become detectable.

Concentrations and seasonal dynamics of dissolved organic carbon in forest floors of two plantations （Castanopsis kawakamii and Cunninghamia lanceolata） in subtropical China

The concentrations and seasonal dynamics of DOC in forest floors of monoculture plantations of Castanopsis kawakamii and Chinese fir （Cunninghamia lanceolata） were assessed in Sanming, Fujian, China （26°11′30″N, 117°26′00″E）. Forest floor samples were taken in January, April, July and October in 2002 and divided into undecomposed material （horizon Oi）, partially decomposed organic material （horizon Oe）, and fully decomposed organic material （horizon Oa）. Upon collection. DOC concentrations of samples were analyzed by a High Temperature TOC. The results showed that the annual average DOC concentration of Chinese fir （1341.7 mg·kg^-1） in the forest floor was higher than that of Castanopsis kawakamii （ 1178.9 mg·kg^-1）. Difference in DOC concentrations was observed among three horizons of the forest floor. DOC concentration of forest floor in the two forests was the highest in horizon Oe. Seasonal trends of DOC concentrations in different horizons of forest floors were similar and the maximal value occurred in autumn （or winter）. The concentration and temporal change of DOC in studied forests were probably related to the variation in moisture, temperature, biological activity and quantity of organic matter in the forest floor.

The satellite reversion of dissolved organic carbon (DOC) based on the analysis of the mixing behavior of DOC and colored dissolved organic matter: the East China Sea as an example

The retrieval of dissolved organic carbon （DOC） distribution by remote sensing is mainly based on the em- pirical relationship of DOC concentration and colored dissolved organic matter （CDOM） concentration in many literatures. To investigate the nature of this relationship, the distributions and mixing behaviors of DOC and CDOM are reviewed in the world＇s major estuaries and bays. It is found that, generally, the C- DOM concentration is well correlated with the salinity in most estuaries, while DOC usually shows a non- conservative behavior which leads to a weak correlation between the DOC concentration and the CDOM concentration. To establish a good satellite reversion of the DOC concentration, the East China Sea（ECS） was taken as an example, and the mixing behavior of DOC and CDOM as well as the influence of biogeo- chemical processes were analyzed except for the physical mixing process with the data from late autumn （November, 2010） and winter （December, 2009） cruises. In the two ECS cruises, the CDOM concentration was found to be tightly correlated with the salinity, influenced little by the photochemical or biological pro- cesses. The data from the winter cruise show that DOC followed a conservative mixing along the salinity gradient, while in the late autumn cruise it was significantly affected by the biological activities, resulting in a poor correlation between the DOC and the CDOM. Accordingly, an improved DOC algorithm （CSDM） was proposed： when the biological influence was significant （Chl a greater than 0.8 μg/dm3）, DOC was retrieved by the conservative and biological model, and if the conservative mixing was dominant （Chl a less than 0.8 μg/dm3）, the direct DOC concentration and CDOM concentration relationship was used. Based on the pro- posed algorithm, a reasonable DOC distribution for the ECS from satellite was obtained in this study, and the proposed method can be applied to the other large river-dominant marginal sea.

An Effective Method of UV-Oxidation of Dissolved Organic Carbon in Natural Waters for Radiocarbon Analysis by Accelerator Mass Spectrometry

Radiocarbon(14C) measurement of dissolved organic carbon(DOC) is a very powerful tool to study the sources, transformation and cycling of carbon in the ocean. The technique, however, remains great challenges for complete and successful oxidation of sufficient DOC with low blanks for high precision carbon isotopic ratio analysis, largely due to the overwhelming proportion of salts and low DOC concentrations in the ocean. In this paper, we report an effective UV-Oxidation method for oxidizing DOC in natural waters for radiocarbon analysis by accelerator mass spectrometry(AMS). The UV-oxidation system and method show 95%± 4% oxidation efficiency and high reproducibility for DOC in both river and seawater samples. The blanks associated with the method was also low(about 3 μg C) that is critical for 14 C analysis. As a great advantage of the method, multiple water samples can be oxidized at the same time so it reduces the sample processing time substantially compared with other UV-oxidation method currently being used in other laboratories. We have used the system and method for 14 C studies of DOC in rivers, estuaries, and oceanic environments and have received promise results.

Dynamics of dissolved organic carbon in the mires in the Sanjiang Plain,Northeast China

Mires in boreal area had proved to be an important dissolved organic carbon （DOC） reserve for the sensitivity to climate change and human interfering. The study was focused on the temporal and spatial dynamics and controlling factors of DOC in a seasonallywaterlogged mire （SLM） and perennially-waterlogged mire （PLM） in the Sanjiang Plain, Northest China. In the two mires, DOC concentrations in both surface water and upper soil strata experienced pronounced seasonal variation. DOC concentrations in the surface waters were the greatest and averagely was 47.82 in SLM and 34.84 mg/L and PLM, whereas that in soil water at 0.3-m depth had little difference （20.25 mg/L in SLM and 26.51 mg/L in PLM）. Results revealed that DOC concentrations declined 5-8 times vertically from the surface down to groundwater. DOC in the groundwater only was in a very small part with the average concentration of 5.18 mg/L. In relation to the surface water, DOC concentrations varied positively with temperature just before 8 August, and only in early spring and later autumn DOC concentrations exhibited identifiable spatial trends along with standing water depths in PLM. It was supposed that the influences from standing water depth took effect only in conditions of low temperature, and temperature should be the most powerful factor controlling DOC dynamics in the mires. Redox potential （Red） showed negative relationship with DOC values while total nitrogen （TN） and the majority of free ions in the soil solution exhibited no relationship. High soil TOC/TN ratio and low redox potentials also led to DOC accumulation in the mires in the Sanjiang Plain.

Effects of Fertilization Types and Cultivation Years on Dissolved Organic Carbon(DOC) in Paddy Soil under Water-logging Condition

In this study, the spatial and temporal distribution characteristics of dis- solved organic carbon （DOC） in water-logged paddy soil in Yanbian were investigat- ed under conditions of different fertilization types （single application of chemical fer- tilizer, mixed application and chemical and organic fertilizers and single application of organic fertilizer） and cultivation years （80 years and 120 years）. The results showed that the spatial and temporal distribution of DOC in water-logged paddy soil changed significantly with time going by. The single application of chemical fertilizer or mixed application of chemical and organic fertilizers contributed to the release of DOC in top paddy soil under water-logging condition; the single application of organ- ic fertilizer promoted the accumulation of DOC in bottom paddy soil, resulting in great heterogeneity of DOC in the vertical space, but the single application of chem- ical fertilizer weakened the vertical spatial heterogeneity of soil DOC; the DOC con- tent in the 80-year-old water-logged paddy soil was higher and more stable than that in the 120-year-old soil.

Temporal and spatial characteristics of dissolved organic carbon in the Wujiang River,Southwest China

River systems play an important role in the global carbon cycle. Rivers transport carbon to the ocean and also affect the carbon cycle in the coastal ocean. The flux from land to the ocean is thought to be a very important part of the land carbon budget. To investigate the effect of dam-building on dissolved organic carbon(DOC)in rivers, three reservoirs of different trophic states in the Wujiang basin, Guizhou Province, were sampled twice per month between May 2011 and May 2012. Temporal and spatial distributions of DOC in the reservoirs and their released waters were studied. It was found that different factors controlled DOC in river water, reservoir water, and released water. DOC in the rivers tended to be affected by primary production. For reservoirs, the main controlling factors of DOC concentration varied by trophic state. For the mesotrophic Hongjiadu Reservoir, the effect of primary production on DOC concentration was obvious. For the eutrophic Dongfengdu Reservoir and the hypereutrophic Wujiangdu Reservoir, primary production was not significant and DOC came instead from soil and plant litter.

Review and suggestions for estimating particulate organic carbon and dissolved organic carbon inventories in the ocean using remote sensing data

Dissolved organic carbon（DOC） and particulate organic carbon（POC） are basic variables for the ocean carbon cycle.Knowledge of the distribution and inventory of these variables is important for a better estimation and understanding of the global carbon cycle.Owing to its considerable advantages in spatial and temporal coverage,remote sensing data provide estimates of DOC and POC inventories,which are able to give a synthetic view for the distribution and transportation of carbon pools.To estimate organic carbon inventories using remote sensing involves integration of the surface concentration and vertical profile models,and the development of these models is critical to the accuracy of estimates.Hence,the distribution and control factors of DOC and POC in the ocean first are briefly summarized,and then studies of DOC and POC inventories and flux estimations are reviewed,most of which are based on field data and few of which consider the vertical distributions of POC or DOC.There is some research on the estimation of POC inventory by remote sensing,mainly in the open ocean,in which three kinds of vertical profile models have been proposed：the uniform,exponential decay,and Gauss models.However,research on remote-sensing estimation of the DOC inventory remains lacking.A synthetic review of approaches used to estimate the organic carbon inventories is offered and the future development of methods is discussed for such estimates using remote sensing data in coastal waters.

Terrestrial dissolved organic carbon consumption by heterotrophic bacterioplankton in the Huanghe River estuary during water and sediment regulation

Nearly 20%–50% of the annual terrestrial dissolved organic carbon(DOC)from the Huanghe(Yellow)River was transported to the estuary during the 5-14d of water and sediment regulation.The concentration of DOC increased sharply during the period of water and sediment regulation,which may promote the terrestrial DOC consumption by heterotrophic bacterioplankton.Water and sediment regulation provides an ideal condition for the study of terrestrial DOC consumption by heterotrophic bacterioplankton when terrestrial DOC increases sharply in rainy season,which may help to seek the fates of terrestrial DOC in the estuaries and coasts.In this study,the concentration and stable isotope of DOC,the biomass,growth,and respiration of heterotrophic bacterioplankton were determined.By the study,we found both average percent contribution of terrestrial DOC to the DOC pool and Contribution of terrestrial DOC to the carbon composition of heterotrophic bacterioplankton decreased as distance from the river mouth increased off shore,which was deceased from(39.2±4.0)%,(37.5±4.3)%to(30.3±3.9)%,(28.2±3.9)%respectively.255-484μg C/(L·d)terrestrial DOC was consumed by heterotrophic bacterioplankton.And 29%-45%terrestrial DOC consumed by heterotrophic bacterioplankton releasing as CO2 by respiration.Comparing with tropical estuary,terrestrial DOC consumed by heterotrophic bacterioplankton was lower in temperate estuary(this study).Temperature may limit the consumption of terrestrial DOC by heterotrophic bacterioplankton.

Spatial Variation of Dissolved Organic Carbon in Soils of Riparian Wetlands and Responses to Hydro-geomorphologic Changes in Sanjiang Plain, China

Spatial variation of dissolved organic carbon(DOC) in soils of riparian wetlands and responses to hydro-geomorphologic changes in the Sanjiang Plain were analyzed through in situ collecting soil samples in the Naoli River and the Bielahong River. The results showed that the average contents of DOC for soil layer of 0–100 cm were 730.6 mg/kg, 250.9 mg/kg, 423.0 mg/kg and 333.1 mg/kg respectively from riverbed to river terrace along the transverse directions of the Naoli watershed. The content of the soil DOC was the highest in the riverbed, lower in the high floodplain and much lower in the river terrace, and it was the lowest in the low floodplain. The difference in the content and vertical distribution of DOC between the riverbed and the three riparian wetlands was significant, while it was not significant among the low floodplain, the high floodplain and the river terrace. The variability of soil DOC was related to the hydrological connectivity between different landscape position of the riparian wetlands and the adjacent stream. Extremely significant correlations were observed between DOC and total organic carbon(TOC), total iron(TFe), ferrous iron(Fe(II)) whose correlation coefficients were 0.819, –0.544 and –0.709 in riparian wetlands of the Naoli River. With the increase of wetland destruction, soil p H increased and soil DOC content changed. The correlation coefficients between soil DOC and TOC, TFe, Fe(II) also changed into 0.759, –0.686 and –0.575 respectively in the Bielahong River. Under the impact of drainage ditches, the correlations between soil DOC and TFe, Fe(II) were not obvious, while the soil p H was weakly alkaline and was negatively correlated with soil DOC in the previous high floodplain. It indicates that riparian hydro-geomorphology is the main factor that could well explain this spatial variability of soil DOC, and the agricultural environmental hydraulic works like ditching also must be considered.

Distribution of dissolved organic carbon in and near the Prydz Bay, Antarctica

During the 16th Chinese National Antarctic Research Expedition (CHINARE) (from November 1999 to April 2000) seawater samples were collected for (DOC) determination in the Prydz Bay and its nearby sea areas. DOC concentrations were determined-by high temperature catalytic oxidation (HTCO) method. The results shows that DOC concentrations, in the upper water column (0 similar to 100 in) range from 14.3 to 181.1 mumol/dm(3), with averaging 52.5 mumol/dm(3) (n = 55). These values are slightly higher than those reported for the Ross Sea, the Pacific Ocean and others. Profiles of DOC concentration in the study areas show a decreasing concentration with increasing depth in the upper 100 m, which is related to biological activities in the water column. DOC concentrations below 100 in are relatively constant with a mean of 40.4 gammamol/dm(3). These DOC are unactive for physical and biological activities and are called refractory DOC. Concentration of the refractory DOC in the study area is consistent with the previous reported values for the Southern Ocean, which is about 41 mumol/dm(3). Based on the difference between the measured DOC concentration and the refractory concentration, the excess DOC concentration in the upper column can be calculated at every station. The excess DOC shows a spatial variability with a higher excess in the north of 64degreesS and little excess in the south of 64degreesS. In conclusion, DOC concentrations in the Prydz Bay and its nearby sea areas,are, consistent with the previous reported values in the Southern Ocean, which show a low DOC concentration with respect to the other oceans. Distribution of surface DOC concentrations in the study areas shows an increase from the southwestern to the northeastern, which is ascribed to the northern spread of continental shelf water from the Prydz Bay in summer. Contents of DOC and their distribution in the Prydz Bay and its nearby sea areas are mainly controlled by physical and biological processes.

Evaluation of Dissolved Organic Carbon Using Synchronized Fluorescence Emission Spectra and Unsupervised Method of Principal Component Analysis (PCA) and Independent Component Analysis (ICA)

Dissolved organic matter (DOM) can be originated from autochthonous or allochthonous sources, where allochthonous DOM can be from pedogenic sources (humic substances—HSs) or anthropogenicsources (wastewater). The analysis of fluorescence emission, excitation, synchronous or excitation-emission matrix (EEM) have been used to identify the main source or probable contribution of dissolved compounds, such as humic acids (HA), fulvic acids (FA) and dissolved organic carbon (DOC) from sewage, but does not quantify. Fluorescence emission is a powerful technique to detect and qualify organic dissolved compounds but fails in quantitative aspects. In this work, we propose an in situ method for direct determination of DOC using synchronous fluorescence spectra with independent component analysis (ICA). Well known standard solutions were used for method development and validation. In this work, we show that it is possible to predict the number of independent contributions using an unsupervised method based on iterative Principal Component Analysis and Independent Component Analysis (PCA-ICA) approach over combined matrix results. Within these results it’s also possible to see that with a very small amount of independent components it is possible to describe environmental samples of HA, FA and primary productivity (PP).

Centennial-scale records of total organic carbon in sediment cores from the South Yellow Sea, China

Global carbon cycling is a significant factor that controls climate change.The centennial-scale variations in total organic carbon(TOC)contents and its sources in marginal sea sediments may reflect the influence of human activities on global climate change.In this study,two fine-grained sediment cores from the Yellow Sea Cold Water Mass of the South Yellow Sea were used to systematically determine TOC contents and stable carbon isotope ratios.These results were combined with previous data of black carbon and (210)~Pb dating from which we reconstructed the centennial-scale initial sequences of TOC,terrigenous TOC(TOC_(ter))and marine autogenous TOC(TOC_(mar))after selecting suitable models to correct the measured TOC(TOC_(cor)).These sequences showed that the TOC_(ter) decreased with time in the both cores while the TOC_(mar) increased,particularly the rapid growth in core H43 since the late 1960s.According to the correlation between the Huanghe(Yellow)River discharge and the TOC_(cor),TOC_(ter),or TOC_(mar),we found that the TOC_(ter) in the two cores mainly derived from the Huanghe River and was transported by it,and that higher Huanghe River discharge could strengthen the decomposition of TOC_(mar).The newly obtained initial TOC sequences provide important insights into the interaction between human activities and natural processes.

Total Organic Carbon Enrichment and Source Rock Evaluation of the Lower Miocene Rocks Based on Well Logs: October Oil Field, Gulf of Suez-Egypt

October oil field is one of the largest hydrocarbon-bearing fields which produces oil from the sand section of the Lower Miocene Asl Formation. Two marl (Asl Marl) and shale (Hawara Formation) sections of possible source enrichment are detected above and below this oil sand section, respectively. This study aims to identify the content of the total organic carbon based on the density log and a combination technique of the resistivity and porosity logs (Δlog R Technique). The available geochemical analyses are used to calibrate the constants of the TOC and the level of maturity (LOM) used in the (Δlog R Technique). The geochemical-based LOM is found as 9.0 and the calibrated constants of the Asl Marl and Hawara Formation are found as 11.68, 3.88 and 8.77, 2.80, respectively. Fair to good TOC% content values (0.88 to 1.85) were recorded for Asl Marl section in the majority of the studied wells, while less than 0.5% is recorded for the Hawara Formation. The lateral distribution maps show that most of the TOC% enrichments are concentrated at central and eastern parts of the study area, providing a good source for the hydrocarbons encountered in the underlying Asl Sand section.