Average Organic Carbon Content Research Articles

Continuously observed light absorbing impurities in snow cover over the southern Altai Mts. in China: Concentrations, impacts and potential sources

The deposition of light absorbing impurities (LAIs) (e.g., black carbon (BC), organic carbon (OC), mineral dust (MD)) on snow is an important attribution to accelerate snowmelt across the northern Xinjiang, China. At present, there is still a lack of understanding of the LAIs concentration, elution and enrichment process in snow cover over Xinjiang. Based on these, continuously sampling during two years carried out to investigate the concentrations, impacts and potential sources of LAIs in snow at Kuwei Station in the southern Altai Mountains. The average concentrations of BC, OC and MD in the surface snow were 2787 ± 2334 ng g −1 , 6130 ± 6127 ng g −1 , and 70.03 ± 62.59 μg g −1 , respectively, which dramatically increased along with snowmelt intensified, reflecting a significant enrichment process of LAIs at the snow surface. Besides, high LAIs concentrations also found in the subsurface and melting layers of the snowpit, reflecting the elution and redistribution of LAIs. With the simulation of the SNow ICe Aerosol Radiative model, BC was the main dominant factor in reducing snow albedo and radiative forcing (RF), its impact was more remarkable in the snowmelt period. The average contribution rates of BC, MD and BC + MD to snow albedo reduction increased by 20.0 ± 1.9%, 13.0 ± 0.2%, and 20.5 ± 2.3% in spring compared with that in winter; meanwhile, the corresponding average RFs increased by 15.8 ± 3.4 W m −2 , 4.7 ± 0.3 W m −2 and 16.4 ± 3.2 W m −2 , respectively. Changes in the number of snowmelt days caused by BC and MD decreased by 3.0 ± 0.4 d to 8.3 ± 1.3 d. It indicated that surface enrichment of LAIs during snow melting might accelerate snowmelt further. Weather Research and Forecasting Chemistry model showed that the resident emission was the main potential source of BC and OC in snow. This implied that the mitigation of intensive snowmelt needs to mainly reduce resident emission of LAIs in the future. • Light absorbing impurities (LAIs) in snowpit were analyzed in the Altai Mountains. • A significant enrichment process of LAIs appeared on snow surface. • Black carbon (BC) had a greater role in snow albedo, radiative forcing and snowmelt than mineral dust. • Residential emission was the main source of BC and organic carbon deposited on snow. Capsule: Vertical variations and enrichment process of LAIs concentrations in snowpit were analyzed in the southern Altai Mountains.

Seasonal Variation of Carbonaceous Species of PM2.5 in a Small City in Sichuan Basin, China

Organic carbon (OC) and elemental carbon (EC) concentrations were measured in daily PM2.5 samples collected over four non-consecutive months representing four seasons from 2016 to 2017 in a small city in the east of Sichuan Basin. The average concentrations of OC and EC during the study periods were observed to be 15.5 ± 13.5 and 5.2 ± 4.7 μg∙m−3, respectively, both with the highest in winter. The OC and EC correlated well in fall and winter, implying that OC and EC were attributed to common emission sources. The estimated secondary OC (SOC) represented 37.2%, 46.7%, 26.9%, and 40.7% of the OC in spring, summer, fall, and winter, respectively. The highest concentration of SOC was found in winter, while the proportion of SOC/OC was highest in summer. Strong correlations were observed between OC vs. K+ and EC vs. K+ in fall and winter, suggesting that biomass burning was a significant source of carbonaceous aerosols. Four sources of OC and EC were resolved by the positive matrix factorization (PMF) model, including coal combustion (5.5% and 12.1%), building and road dust (19.7% and 18.1%), biomass burning (38.7% and 33.1%), and vehicle emission (36.1% and 36.7%), respectively. The potential source contribution function (PSCF) analysis signified that the main source areas of OC and EC were distributed in or nearby Wanzhou.

Hydrocarbon source potential evaluation insight into source rocks—A case study of the first member of the Paleogene Shahejie Formation, Nanpu Sag, NE China

The features of source rock hydrocarbon generation, expulsion, and retention are essential factors in petroleum resource potential evaluation. In this study, the improved hydrocarbon generation potential evaluation method was used to quantify the characteristics of the source rocks of the first member of the Paleogene Shahejie Formation (Es1) in the Nanpu Sag, Bohai Bay Basin, NE China. Based on the geological and geochemical data for the source rocks, the favorable exploration areas were predicted and the resource potential was evaluated. Our results show that Es1 is a set of high-quality source rocks with desirable geological (maximum thickness > 600 m) and geochemical (average total organic carbon content of 1.44%; dominantly type II kerogen; mature stage) characteristics. The improved hydrocarbon generation potential model shows that the hydrocarbon expulsion threshold is located at Ro=1.0%. The maximum hydrocarbon generation potential (Qg), hydrocarbon expulsion potential (Qe), hydrocarbon retention potential (Qs), and efficient hydrocarbon retention potential (Qse) are 549.31, 162.20, 387.11, and 287.11 mg HC/g TOC, respectively. The maximum hydrocarbon generation, expulsion, retention, and effective retention intensities are 250×104, 70×104, 180×104, and 150×104 t/km2, respectively. These parameters reach the highest value in the Linque and Caofeidian Sub-sag. The resource potential of the retention shale oil, the movable shale oil, and the conventional and the tight petroleum resources are 1.99×108, 4.38×108, and 1.37×108 t oil equivalent, respectively. This study offers a fresh and plain but operable workflow for resource evaluation, which can be applied in other petroliferous basins with low degree of exploration.

Predicting carbonaceous aerosols and identifying their source contribution with advanced approaches

Organic carbon (OC) and elemental carbon (EC) play important roles in various atmospheric processes and health effects. Predicting carbonaceous aerosols and identifying source contributions are important steps for further epidemiological study and formulating effective emission control policies. However, we are not aware of any study that examined predictions of OC and EC, and this work is also the first study that attempted to use machine learning and hyperparameter optimization method to predict concentrations of specific aerosol contaminants. This paper describes an investigation of the characteristics and sources of OC and EC in fine particulate matter (PM2.5) from 2005 to 2010 in the City of Taipei. Respective hourly average concentrations of OC and EC were 5.2 μg/m3 and 1.6 μg/m3. We observed obvious seasonal variation in OC but not in EC. Hourly and daily OC and EC concentrations were predicted using generalized additive model and grey wolf optimized multilayer perceptron model, which could explain up to about 80% of the total variation. Subsequent clustering suggests that traffic emission was the major contribution to OC, accounting for about 80% in the spring, 65% in the summer, and 90% in the fall and winter. In the Taipei area, local emissions were the dominant sources of OC and EC in all seasons, and long-range transport had a significant contribution to OC and in PM2.5 in spring.

Seasonal variation of carbonaceous species in PM1 measured over residential area of Delhi, India

Seasonal variation in the concentration of Organic Carbon (OC) and Elemental Carbon (EC) was investigated in PM1 size fraction over a residential area in Delhi, India. The sampling was carried out using a cascade impactor from April 2018 to March 2019. The OC/EC content in the sample was measured by a carbon analyzer (Thermal/Optical, DRI 2001). The annual average concentration of OC and EC was found to be 28.01 ± 14.61 μg/m3 and 10.40 ± 7.41 μg/m3, respectively in PM1 (139.52 ± 49.20 μg/m3). The highest concentrations of OC and EC were observed in the post-monsoon and winter season, respectively. Average OC & EC concentrations in summer, monsoon, post-monsoon, and winter seasons were found to be 22.57 ± 3.72 & 5.51 ± 1.28, 11.70 ± 3.07 & 3.60 ± 0.39, 42.06 ± 7.10 & 11.72 ± 2.45 and 37.28 ± 14.45 & 18.52 ± 6.23 µg/m3, respectively. Total carbonaceous material (TCM) accounted for approximately 40% of PM1 concentration. The annual average OC/EC ratio was observed to be 2.69, which ranged between 1.77 to 5.39. Analysis of carbon subfractions reveals OC3 and EC1 as the dominant fraction suggesting fossil fuel combustion as dominant emission sources. The exposure risk estimated on the basis of inhalation dose was observed very high during the winter season which can adversely affect the health of people. This study also revealed that the emissions from the residential area are the key source of OC and EC, along with PM1.

Fracture characteristics from outcrops and its meaning to gas accumulation in the Jiyuan Basin, Henan Province, China

Abstract The target Oil-Shale Member (TOSM) in the Upper Triassic Tanzhuang Formation in the Jiyuan Basin is about 140 m thick and its burial depth is generally between 3,000 and 7,000 m. This paper presents a study of fractures in outcrop analogs for the TOSM based on outcrop observations and experimental measurements. The role of fractures in gas accumulation in the Jiyuan Basin was also analyzed. Also, a workflow used in building discrete fracture models based on the outcrop observed data is described. Results show that the average total organic carbon content and vitrinite reflectance of the oil shale are 4.13 and 1.33%, respectively, with the organic matter type dominated by sapropel-humics (II1), indicating high potential for shale gas generation. Fracture characteristics showing mostly vertical or intersect the bedding at high angles, and partially unfilled. The fracture lengths and widths range from a few centimeters to several hundred meters, and 0.05 to 0.5 cm, respectively, and the average linear fracture density is 6.3 m. In addition, the average brittle-mineral content of the oil shale is 53.7%, indicating that the oil shale in the TOSM has strong fracability. The hydrocarbon generation occurred twice in the TOSM. The primary reservoir formed by the first hydrocarbon generation was destroyed by fractures and tectonic uplift, and partial hydrocarbon migrated to the Paleogene along the second-phase fractures to form a secondary reservoir. The gas formed by the second hydrocarbon generation was mainly migrated into the fracture network of the TOSM.

Soft rock increases the colloid content and crop yield in sandy soil

AbstractDesertification is reducing the amount of land available to produce food in semi arid and arid regions worldwide. Management techniques to reduce this problem are needed. This paper investigated if the addition of soft rocks to sandy soils would improve soil resilience and productivity. The model system selected for this study was located in Mu Us, China. Soft rocks are defined as a loose rock layer. Collected soft rock and sand from the same study area were compounded in the volume ratios of 0:1 (CK), 1:5 (C1), 1:2 (C2), and 1:1 (C3). The results revealed that the average content of soil organic carbon (SOC) with increasing soil depth and was 3.11 g kg−1 in the 20 to 30 cm soil depth. The highest average content of particulate organic carbon (POC) was observed in the 10‐20 cm soil layer (2.72 g kg−1). In the 10 to 20 cm soil depth, the polysaccharide content was the highest (125.3 and 119.08 μg g−1) in the C1 and C2 treatments. However, in all soil layers the C2 treatment had the highest (0.11 g kg−1) content of calcium carbonate. Compared with the CK treatment, the addition of soft rock increased of corn yield, the C2 treatment had the largest increase (65.46%). The corn yield showed a significantly positive correlation with polysaccharides at 10–20 cm. The overall results showed that soft rock o sand ratio of 1:2 could increase the crops yield, which was of great significance to the sustainable development of agriculture in the sand area.

Source rock maturity and petroleum generation in the Dahomey Basin SW Nigeria: Insights from geologic and geochemical modelling

Sedimentology, foraminifera paleoecology, geochemical and petroleum system modelling studies were performed on Cretaceous shales from onshore Orimedu-1 and offshore X (at a water depth of 914 m) wells in the Dahomey Basin, southwestern Nigeria to evaluate their maturity, hydrocarbon generation potentials, and regional significance for petroleum prospectivity. Foraminifera biofacies analysis of the studied shales suggests deposition in dominantly marine environments. The average total organic carbon content (TOC, wt%) and hydrogen index (HI, mgHC/gTOC) for Cenomanian, Turonian, and Coniacian shales in X-well are 1.3, 0.9, 1.3 and 406, 560, 214 respectively. While the Cenomanian and Turonian shales in Orimedu-1 have TOC (wt%) of 1.3 and 1.9, and HI (mgHC/gTOC) of 179 and 357 respectively. Well X source rocks contain predominantly marine-derived Type II kerogen, while Orimedu-1 well contain terrigenous-derived gas prone kerogen. The integration of recently acquired kinetic data from immature source rocks further constraints the prediction of petroleum generation in the study area.1D basin modelling of X well reveals that the Cenomanian Source Rock (CSR) is the most mature bed in the basin having attained the initial 10% transformation ratio (TR) at 87 Ma, got to peak TR (~50%) at 86 Ma, and reached 83% at 53.6 Ma With a present-day thermal maturity of 0.95% VRo. The Turonian source in well X also attained the initial 10% TR at 87 Ma, got to peak (~50% TR) at 86 Ma and 69% TR at 50 Ma. These modelled source beds are deeper than the source with 0.62 %VRo used for kinetic study. The observed maturity trend is mostly controlled by the regional erosive events associated with the West African rift system during Santonian and Eocene times. The source rocks in Orimedu-1 are immature. The timing of the generated and expelled hydrocarbons into the Cretaceous petroleum systems of Dahomey Basin is of regional significance with the entire Gulf of Guinea basins because of the similar evolution and sedimentation history along with recent discoveries and production of hydrocarbon.

The hydrocarbon generation and expulsion features of source rocks and tight oil potential of the second member of the Qiketai Formation, Shengbei area in the Turpan–Hami Basin, NW China

Significant progress in tight oil exploration has been reported in the second member of the Qiketai Formation (J2q2) in the Shengbei area of the Turpan–Hami Basin. Geochemical analyses were conducted to assess the quality of the J2q2 source rocks. The improved hydrocarbon generation potential method was utilized to quantify the hydrocarbon generation and expulsion features of the source rocks. The results showed that J2q2 source rocks were deposited in a reduced lacustrine setting with a high palaeoproductivity. The J2q2 source rocks are widely distributed (approximately 1,000 km2) and have a thickness that varies from 50 to 130 m. Moreover, they can be identified as a set of high‐quality source rocks (thermally mature rocks with Ro values >0.5%, consisting mainly of types I and II kerogen and possessing an average total organic carbon content of 2.68%). The oil–source correlation results reveal that the source of crude oil in the studied area is J2q2. The improved hydrocarbon generation potential method is established for different kerogen types to limit the influence of the kerogen type on the calculation. The hydrocarbon expulsion threshold of the type I model is located at Ro = 0.6%. The type II kerogen rocks have different characteristics, and the hydrocarbon expulsion threshold is located at Ro = 0.62%. The maximum hydrocarbon generation and expulsion intensities are 700 × 104 t/km2 and 400 × 104 t/km2, respectively. The hydrocarbon generation and expulsion amount of the J2q2 source rocks are 21.4 × 108 t and 12.3 × 108 t, respectively. The tight oil potential of the J2q2 tight oil in the Shengbei area is 4.09 × 108 t. The SB10 and SB6 well areas are favourable J2q2 tight oil exploration areas in the Shengbei area. The SB10 well area has the highest hydrocarbon generation and expulsion intensities in the study area and is the best tight oil exploration target.

Wintertime carbonaceous species and trace metals in PM10 in Darjeeling: A high altitude town in the eastern Himalayas

Carbonaceous components [organic carbon (OC), elemental carbon (EC), water soluble organic carbon (WSOC), primary organic carbon (POC), secondary organic carbon (SOC) and carbonaceous aerosols (CAs)] and major and trace elements (Na, Mg, Ca, Al, Fe, Ti, Cl, P, S, K, Cr, Ni, Cu, Zn, Mo and B) of PM10 were studied over the eastern Himalayan high altitude station [Darjeeling: 27.01°N and 88.15°E, 2200 m average mean sea level (amsl)] during winter 2018–19 (December 2018–February 2019). The carbonaceous aerosols/species (CAs) contributed to ~23% of PM10 mass concentration, whereas major and trace elements accounted for 10% of PM10. During the entire study period, the average concentrations of PM10, OC, EC, WSOC, POC, SOC and CAs were recorded as 48 ± 16 μg m−3, 5.39 ± 1.84 μg m−3, 2.60 ± 0.94 μg m−3, 3.87 ± 1.18 μg m−3, 3.40 ± 1.23 μg m−3, 1.99 ± 1.03 μg m−3 and 11.21 ± 3.78 μg m−3, respectively. Significant positive correlation between OC & EC and OC & WSOC have been observed which are indicating their common sources. WSOC/OC ratio was estimated to be 0.71 suggesting that the biomass burning is one of the major sources of carbonaceous aerosols at Darjeeling during winter. The significant positive correlation of PM10 with crustal elements (Al, Fe, Ca, Mg and Ti) as well as the correlation of Al with other crustal elements (Fe, Ca, Mg and Ti) indicates the abundance of mineral dust at the sampling site. Principal component analysis (PCA) identified the contribution of crustal/soil dust, biomass + coal burning, vehicular emissions and solid waste to the PM10 over the eastern Himalayan region of India.

Estimated contribution of vehicular emissions to carbonaceous aerosols in urban Beijing, China

Worldwide attention has been focused on air pollution associated with vehicle emissions. With the highest number of vehicles, Beijing has experienced air pollution related to vehicle emissions. To better recognize the contributions of vehicle emissions to organic carbon (OC) and elemental carbon (EC), hourly measurements of OC and EC in PM2.5 were conducted in urban Beijing from June 1, 2016 to May 31, 2017 in addition to auxiliary measurements of water-soluble ions and elements. The average concentrations of OC and EC were 11.9 ± 11.1 and 3.7 ± 3.6 μg/m3 during the study period, respectively, while those of OC and EC during the nighttime (0:00–6:00), morning rush hour (7:00–9:00) and evening rush hour (17:00–19:00) were 12.9 ± 12.9 μg/m3 and 4.4 ± 4.3 μg/m3, 10.4 ± 9.8 μg/m3 and 3.7 ± 3.1 μg/m3, and 12.3 ± 8.7 μg/m3 and 3.5 ± 2.4 μg/m3, respectively. The diurnal variations in OC and EC concentrations showed higher values during the nighttime, morning rush hour and evening rush hour. Strong correlations were found between OC and CO (r2 = 0.76–0.79) and between OC and NOx (r2 = 0.63–0.68); strong correlations were also found between EC and CO (r2 = 0.76–0.81) and between EC and NOx (r2 = 0.63–0.68) during the nighttime, morning rush hour and evening rush hour. The results of source apportionment based on the hourly PM2.5-associated chemical composition by a positive matrix factorization model showed that vehicle emissions accounted for 23.0% of PM2.5. From the profiles of the source apportionment of PM2.5, it could be found that vehicle emissions contributed 51.2%, 51.3% and 25.2% of the concentrations of OC, EC and PM2.5 on average during the nighttime, respectively. The contributions of vehicle emissions to OC, EC and PM2.5 during the nighttime were higher than or close to those during the evening rush hour and the morning rush hour. This result indicated that vehicular emissions play an important role in carbonaceous aerosols and PM2.5 during the nighttime. The above results provide insight into the quantitative evaluation of the contribution of vehicular emissions to OC, EC and PM2.5 and thus could provide references for pollution control in areas with high vehicular emissions.

Impacts of PM2.5 sources on variations in particulate chemical compounds in ambient air of Bangkok, Thailand

In this study, PM2.5-bound carbonaceous compounds, including organic carbon (OC), elemental carbon (EC), water-soluble ionic species (WSIS), and polycyclic aromatic hydrocarbons (PAHs) in the ambient air of Bangkok were analysed. The mean PM2.5 concentration was 77.0 ± 21.2 μg m−3, while the average concentrations of OC, and EC were 8.03 ± 4.02, and 2.62 ± 1.49 μg m−3, respectively. The relatively high OC/EC ratio (3.52 ± 1.41) coupled with a strong positive correlation between K+ and carbonaceous compounds (K+vs. OC (r = 0.86), K+vs. EC (r = 0.87), K+vs. Char-EC (r = 0.82)) suggest that biomass burning are one of the major contributors to PM2.5 in the sampling area. A comparatively high abundance of both B[g,h,i]P and Ind guides that vehicular exhausts, industrial combustion, and burning of waste might reflect the sources of these PAHs in Bangkok's atmosphere. Interestingly, hierarchical cluster analysis (HCA) indicated that the main source of PM2.5 was a mixture of various combustion activities (e.g. biomass burning, vehicular exhaust, fossil fuel, coal, and industrial emissions). Principal Component Analysis (PCA) successfully classified five principal sources of PM2.5, including vehicular exhaust, biomass burning, sea salt aerosol, power plant, and industrial emissions, which accounted for 43.7%, 24.0%, 10.5%, 6.48%, and 4.46%, respectively. These results indicated that the effects of vehicular exhausts and biomass burning played an important role in governing the PM2.5 level in ambient air of Bangkok. The findings of this study aid policymakers in launching effective air quality control strategies based on the source apportionment analysis.

Gas-bearing property of the Lower Cambrian Niutitang Formation shale and its influencing factors: A case study from the Cengong block, northern Guizhou Province, South China

To gain a better understanding of the gas-bearing property of Lower Cambrian Niutitang Formation shale and its influencing factors, the shale gas-bearing conditions, gas content, and composition in the Cengong block were investigated in this work based on wells CY1, TX1, and TM1. The Niutitang shale reservoir is characterized by large thickness, abundant organic matter with an average total organic carbon content of 4.74%, and high quartz content averaging 53.9%; therefore, it has good shale gas-bearing potential. The results of water immersion and ignition tests intuitively revealed the existence of shale gas based on the occurrence of continuous dense clusters of bubbles and long flames of 1–2 m. The Langmuir volumes of shale samples from well TM1, which ranged from 1.70 to 5.53 m3/t, were positively associated with TOC content and Brunauer–Emmett–Teller surface area, indicating a strong adsorption capacity and significant adsorbed gas potential. However, large differences were observed among the three wells with regard to gas-bearing properties; wells CY1 and TX1 had average total gas contents of 1.25 and 0.33 m3/t, respectively; the gas composition of well TM1 was dominated by nitrogen (N2), with contents generally exceeding 95%. Furthermore, the gas from well TX1 was mainly composed of methane with an average content exceeding 80%. Burial depth and TOC and quartz contents had significant control on the vertical distribution of gas content, and local tectonic preservation conditions resulted in differences of gas-bearing properties among various wells. The measured, lost, and total gas contents all presented positive correlations with TOC, quartz contents, and porosity, and were negatively related to clay content. The shale formed in deep-water shelf environments had better gas-bearing properties than that formed in shallow-water shelf environments. The broad axis of the box syncline in the Cengong block is a favorable location for shale gas accumulation, and fault development affects the shale gas plane distribution. Because of the influence of faults, the shale of well TM1 had low hydrocarbon content. Furthermore, based on the combined patterns of folds and faults as well as other special specific factors, a classification scheme of shale gas accumulation patterns in South China was developed.

Seasonal variation of carbonaceous PM2.5 in an Istanbul traffic site

The seasonal variation of fine carbonaceous aerosol was evaluated in an urban traffic site in Istanbul. PM2.5 samples were collected on selected days during four seasons between Jan 2017–Jan 2018. Daily PM2.5 concentrations were obtained experimentally by the gravimetric method in Beşiktaş, while hourly concentrations were obtained from the Air Quality Monitoring Network of Istanbul in Çatladıkapı, Silivri, Kağıthane, and Ümraniye. Organic carbon (OC) and elemental carbon (EC) concentrations were determined by a thermo-optical carbon analyzer for samples collected in Beşiktaş. The 24-h US-EPA air quality standard of 35 μg m−3 was exceeded 13, 25, 41, 42, and 57% of the time in Çatladıkapı, Silivri, Kağıthane, Ümraniye, and Beşiktaş, respectively. These exceedances occurred mainly during the fall and winter owing to a combination of emissions from fuel combustion for residential heating, traffic and industry, and poor air dispersion due to weak atmospheric motion and low mixing heights. Average OC concentrations ranged as 6.62–7.32 μg m−3 during spring and summer, and 13.76–14.1 μg m−3 during fall and winter. The OC concentrations observed in this work during the summer and winter were 2–4 and 3–6 times higher than concentrations observed in the USA and Europe, respectively. The EC concentrations did not show considerable seasonal variation, with values between 2.16 and 3.26 μg m−3. EC concentrations in Beşiktaş were 7 and 9 times higher than concentrations observed in the USA and Europe, in order. Results obtained in this study could be helpful for future implementation of policies and strategies to reduce emissions from combustion sources in order to comply with the air quality standards.

Study on the Changes of Calcium Carbonate and Organic Carbon in the Soil after the Feldspathic Sandstone and Sand Compounding

By analyzing the changes of calcium carbonate and free iron oxide in inorganic cement materials in different proportions of the feldspathic sandstone and sand compounding soil under different tillage years (2a and 9a), the calcium carbonate and free soil in the soil were determined in two years. The average content and relationship of iron oxide. The results show that the average content of calcium carbonate is the highest in the mixed soil of feldspathic sandstone and sand in the ratio of 1:2, the ratio is more favorable for the accumulation of calcium carbonate in 0-30cm soil surface inorganic colloid. The difference of organic carbon content in 0-10cm and 10-20cm soil layers was significant, but it was not significant in 20-30cm soil layers. After the mixture of feldspathic sandstone and sand for 9a, the highest content of organic carbon in each soil layer is the mixture of feldspathic sandstone and sand according to 1:1. From the mixture soil which has been cultivated for 9a, the soil layers of 10-20 cm and 20-30 cm, the content of organic carbon tends to be stable in each proportion. The average organic carbon content was 2.00 g/kg in 2a and 3.37 g/kg in 9a, which increased by 68.50% compared with 2a.

Variation of carbonaceous species and trace elements in PM10 at a mountain site in the central Himalayan region of India

Observations of carbonaceous species [organic carbon (OC), elemental carbon (EC), water soluble organic carbon (WSOC), carbonaceous aerosols (CAs) and secondary organic carbon (SOC) ] and trace elements (As, Cr, Ni, Zn, Na, Mg, Al, P, K, Ca, Ti, Fe, and Mn) in PM10 are made over a high altitude site (ARIES, Nainital, 29.4° N, 79.5° E, ~1958 m amsl) in the central Himalayan region during October 2018−February 2019 to explore their possible sources. The average concentrations of PM10, OC, EC, WSOC, CA and SOC were recorded as 44±13 µg m-3, 3.66±1.26 µg m-3, 1.29±0.61 µg m-3, 2.28±0.76 µg m-3, 7.15±1.96 µg m-3 and 1.45±0.73 µg m-3, respectively during the study period. The concentrations of PM10, OC, EC, WSOC, CAs and SOC were significantly varied during autumn (October-November) and winter (December-February) seasons. During both the seasons, significant positive linear trend between OC & EC and OC & WSOC have been observed which is indicative of their common sources of carbonaceous aerosols at the study site. WSOC/OC ratio was estimated as 0.56 and 0.67 during autumn and winter, respectively suggested that the biomass burning could be one of the major sources of carbonaceous aerosols at Nainital. The significant positive correlation of PM10 with crustal elements (Al, Fe, Ca, Mg and Ti) as well as correlation of Al with other crustal elements (Fe, Ca, Mg and Ti) indicates the abundance of mineral dust at the sampling site. The observed Fe/Al ratio (1.07) also indicates mineral dust as a source at the sampling site, similarly, Ca/Al ratio (1.36) indicates that aerosols over this region is rich in Ca mineral as compared to average continental crust. Principal component analysis (PCA) identified the contribution of crustal/soil dust, biomass burning and industrial emissions to the PM10 over the central Himalayan region of India. Five days back trajectory analysis indicates that the air mass impacting the sampling site is from local surrounding area in Uttrakhand as well from Himachal Pradesh, Jammu & Kashmir, Ingo Gangetic Plain (IGP) region, Pakistan, Afghanistan region and Thar Desert.

The influence of rigid matrix minerals on organic porosity and pore size in shale reservoirs: Upper Devonian Duvernay Formation, Alberta, Canada

Organic porosity is an important component of the pore system in many shale hydrocarbon reservoirs. While much research has been directed towards understanding the development of organic porosity as a function of thermal maturity, relationships between mineralogy and organic porosity have been less extensively investigated. This study illustrates the role of rigid matrix minerals, particularly biogenically-sourced microcrystalline quartz, on organic porosity and pore size evolution.The Upper Devonian Duvernay Formation of western Canada is a siliceous-calcareous self-sourced reservoir with 3.2-3.79 wt. % average total organic carbon (TOC) content in a study area occurring in the volatile oil to dry gas thermal maturity zones. Biogenic silica is widely distributed throughout the matrix as microcrystalline quartz and locally comprises >50 wt. % of the rock. Porosity and pore size data gathered from BIB- and FIB-SEM, helium porosimetry, H1 NMR T2, and MICP indicate that organic porosity and pore size is enhanced when in association with biogenic silica. Biogenic silica forms a rigid siliceous matrix framework that limits compaction of pores and ductile organic matter and clay minerals. Where biogenic silica concentration is low, clay mineral (mica+illite) interparticle micro- and fine mesopores dominate. In these samples detrital quartz and biogenic silica have limited influence on pore size other than to preserve the small fraction of organic macropores. The occurrence of biogenic- and clay-dominated pore systems varies systematically with stratigraphic and lateral variations in lithofacies, and sharp contrasts are observed across sequence boundaries. The observation that mineralogy strongly influences organic pore preservation confirms that studies examining the relationship between thermal maturity and organic porosity must account for mineralogical variations.

Assessment of shale gas potential of the lower Permian transitional Shanxi-Taiyuan shales in the southern North China Basin

The geological research and exploration evaluation of marine–continental transitional shale gas are lagging behind the rapid development of marine and continental shale-gas resources in China. To investigate the shale-gas potential of the lower Permian Shanxi and Taiyuan formations in the southern North China Basin, a series of measurements on representative core samples were conducted to characterise shale features, including sedimentary environment, organic geochemistry, mineral composition, pore structure and gas-bearing capacity. The average total organic carbon (TOC) content of the Shanxi and Taiyuan shales reaches 1.68 and 2.26 wt%, respectively, and deposition took place in environments of rapidly changing depositional conditions, where predominantly gas-generating type III kerogen was preserved in the sediments. Regarding the sedimentary environments, different microfacies can affect effective thickness, abundance of organic matter, mineral composition and gas content in the Shanxi and Taiyuan formations. In addition, TOC content, inertinite, chlorite, thermal maturity and pyrite have significant impacts on gas contents. Although the Shanxi-Taiyuan shales are not comparable with gas-producing shales in the USA, there are some similarities in shale reservoir parameters such as the relatively higher organic richness (>2.0 wt% TOC) and gas content (∼2.0 m3/t) than in the well-developed Longmaxi and Yanchang shales. Consequently, the Shanxi-Taiyuan shales could be classified as potential shale-gas targets owing to their relatively favourable reservoir properties and gas accumulation. However, some complex geological conditions, such as the greater burial depth (>3500 m), higher clay content (>45%), deficiency of organic-matter hosted pores but other well-developed types of pore-microfracture, extremely high thermal maturity (>3.0% R o), several large unsealed faults, etc. may impact gas production in the study areas. Therefore, local geological conditions should be fully considered for the exploration and development of transitional shale gas in the southern North China Basin. KEY POINTS Main controlling factors of shale-gas content in transitional Shanxi-Taiyuan shales. Influence of sedimentary microfacies on shale reservoir parameters. Detailed investigation of transitional shale-gas potential in southern North China Basin, China.

Chemical characterization and sources of PM2.5 at a high-alpine ecosystem in the Southeast Tibetan Plateau, China

Abstract The study of atmospheric chemical compositions in remote areas is of great significance for understanding the biogeochemical impact of atmospheric dry deposition on ecosystems. In this study, a total of 50 p.m.2.5 samples were collected at a high alpine forest of Mt. Gongga, Eastern Tibetan Plateau from May 2015 to May 2016 to investigate the characteristics of PM2.5 mass concentration and its major compositions including elemental carbon (EC), organic carbon (OC), and 24 trace elements. The average PM2.5 mass concentration was 17.19 ± 8.81 μg/m3, which was at an intermediate level compared with other areas of Tibetan Plateau. The yearly average concentrations of OC and EC were 2.98 ± 1.95 and 0.43 ± 0.33 μg/m3, accounting for 19.49% and 2.51% of PM2.5 mass, respectively, and the sums of the total concentrations of the 24 analyzed trace elements were 3.70 ± 0.80 μg/m3, accounting 27% of PM2.5 mass concentration. PM2.5, EC and OC showed the higher concentrations and larger fluctuation in the dry season (October 2015 to May 2016) compared with those in the wet season (June 2015 to September 2015), which was attributed to the multiple factors including the increases of biomass burning and fossil fuel emissions, the relatively shallow boundary layer height and lower temperature, and the less precipitation. Two distinct seasonal patterns were observed for the 24 analyzed trace elements in PM2.5: the crustal-derived trace elements like Fe, Al, Mn and Sr showed the higher concentrations in the wet season, while anthropogenic-derived elements such as Cd, Pb, Ni and Zn exhibited the higher level during the dry season. Six sources were identified for PM2.5 at Mt. Gongga with the application of the positive matrix factorization (PMF). Biomass burning (27.06%) and crustal source (26.93%) were the two main sources, followed by secondary formation (16.41%), traffic-related source (12.89%), coal burning (10.57%) and industrial metallurgical process (6.15%). Finally, it was proposed that the atmospheric acidic processing could not only promote the dissolution of Fe, but also enhance the solubility of the other trace elements in the atmosphere during the transport. Accordingly, this would increase the bioavailability and/or toxicity to the biotic and plants.

Pore characteristics and evolution mechanism of shale in a complex tectonic area: Case study of the Lower Cambrian Niutitang Formation in Northern Guizhou, Southwest China

The Lower Cambrian Niutitang Formation is one of the most important shale reservoirs in the Northern Guizhou. To study the characteristics of pore structures and the relationships between shale's physical properties and pore structures in the complex tectonic area, from the perspective of hydrocarbon generation and evolution, the mineral composition, pore structure characteristics of shale samples in northern Guizhou were analyzed using X-ray diffraction (XRD), optical microscopic composition analysis, focused ion beam-scanning electron microscopy (FIB-SEM), vitrinite reflectivity and nitrogen adsorption experiments. Results indicate that the pore structures can be categorized into conical, ink bottle, spherical, elliptical, beaded, irregular, and plate-like intersecting microfractures. Shale samples are organic-rich with an average total organic carbon content of 4.39%. Organic matter is consumed within the shale matrix during the hydrocarbon generation and evolution, which increases the organic pore size and the proportion of organic pores. The high TOC content is conducive to developing organic pores. In addition, the average content of brittle minerals is greater than 70%. High content of brittle minerals during diagenesis is conducive to developing the residual pores at the edges of mineral particles and dissolved pores within mineral particles. Thus, the high content of brittle minerals and TOC content is favorable for the development of meso-macropores. The content of clay minerals within the shale samples ranges from 6.3% to 42.2%, with an average of 20.02%. Micropores and mesopores mainly occur in the clay minerals. Pores in clay minerals are easily compacted under tectonic stress. Meanwhile, high thermal evolution degree and the vitrinite reflectance Ro greater than 3.5 is not conducive to developing pores. Hence, high TOC content, high brittle minerals content, and thermal evolution degree ranging from 0.6% to 3% make the Lower Cambrian Niutitang Formation shale reservoirs favorable for shale gas exploration.