Average Organic Carbon Content Research Articles

Impact of Deforestation and Erosion on Some Soil Physicochemical Properties and Microbial Activity on Steep Slopes

Deforestation and erosion are important indicators of the beginning of land degradation. This study aimed to present the changes in some physical, chemical, and microbial characteristics of the soil on sloping land on which deforestation has led to gully erosion. The study was conducted on dam slopes on which the forest cover had been removed, and gullies subsequently formed. Nine soil samples were taken from deforested and eroded slopes (SDE) and six soil samples were taken from slopes with forest vegetation (SF) for physical and chemical soil analysis. Thus, a total of 15 samples were taken from the study area to determine physical and chemical properties. To determine microbial biomass and activity, a total of 30 samples were taken from the same locations in duplicate. The results revealed that sand particles, bulk density, soil temperature, >2 mm/<2 mm fraction ratio, pH, and electrical conductivity increased markedly, whereas total porosity and organic carbon decreased (p≤0.05) in SDE soils. Moreover, it was found that the average organic carbon content of SDE soils decreased by more than five times compared to SF soils. Microbial biomass carbon and basal respiration in SDE and SF soils indicated a significant difference (p≤0.05). While the metabolic quotient indicated a marked difference (p≤0.05) between SDE and SF soils, the microbial quotient showed no significance (p>0.05). Furthermore, it was found that the most relevant physical and chemical soil characteristics of microbial biomass and activity were bulk density, pH, and organic carbon.

Correlation between polycyclic aromatic hydrocarbons and total organic carbon in surface sediments of the Bohai Sea and the North Yellow Sea.

The correlation between polycyclic aromatic hydrocarbons (PAHs) and organic carbon is an important indicator of the marine environment. In this paper, twenty-six surface sediment samples were collected from the Bohai Sea and the North Yellow Sea as the study area, and the contents of sixteen PAHs ranged from 71.34 ng·g-1 to 240.78 ng·g-1 with an average of 143.26 ng·g-1 by gas chromatography. The source analysis indicated the source of PAHs in the surface sediments of the study area was more complex, and the percentage of combustion sources was higher than that of petroleum sources, which might cause less negative ecological risks. The average content of total organic carbon (TOC) was 5.25%, as determined by automatic potentiometric titration, and the content of TOC was higher in the Bohai Sea than in the North Yellow Sea. TOC was significantly correlated with HWM-PAHs but was not correlated with LWM-PAHs, which proved organic matter was more effective in controlling high-molecular-weight PAHs than low-molecular-weight PAHs in the surface sediments of the Bohai Sea and the North Yellow Sea.

A Cryogenian interglacial source rock in South China: Geochemistry, spatial distribution and organic matter enrichment

The organic-rich Datangpo Formation was deposited between Sturtian and Marinoan glaciations during the Cryogenian in South China. As a set of source rocks with great petroleum exploration prospect, it is important to understand how the glacial ocean transformed into a favorable condition for organic matter (OM) accumulation for evaluating its hydrocarbon potential. Here, the organic and inorganic geochemical data were tested, and the lithological and geochemical data were compiled to study the spatial distribution and OM enrichment of Datangpo Formation. The Datangpo Formation is a set of good quality (average total organic carbon (TOC) content = 1.83 %), sapropelic OM type (light organic carbon isotopes (δ13Corg) and overmature source rocks (average solid bitumen Raman spectroscopy equivalent vitrinite reflectance (Requ) = 4.28%). The areas of thickest source rock are located in the Xiushan and Tongren, and spatial distribution was controlled by rift activity and the erosion by the Marinoan glaciation instead of the remnant glacial topography of the Sturtian glaciation. The OM enrichment of Datangpo Formation was controlled by anoxic/euxinic water condition, high sedimentary rate, and high productivity. The primary productivity in interval Ⅰ and Ⅱ was promoted by hydrothermal nutrients continued since late Sturtian glaciation and few terrigenous nutrients, and terrigenous nutrients of continental weathering during greenhouse period, respectively.

Long-Term Application of Manure and Different Mineral Fertilization in Relation to the Soil Organic Matter Quality of Luvisols

Long-term field experiments were conducted on luvisol at five sites in the Czech Republic (42–48-year duration). The average total organic carbon content in the soil varied between 9.0 and 14.0 g kg−1. In these trials, seven crops were rotated in the following order: clover, winter wheat, early potato, winter wheat, spring barley, potato, and spring barley with interseeded clover. Five treatments were studied: unfertilized treatment (Con), farmyard manure (F), and combinations of farmyard manure with three mineral fertilization levels (F+M1, F+M2, F+M3). Plant residues were not incorporated into the soil. An amount of 40 t ha−1 of farmyard manure fresh matter was applied twice during crop rotation. Intensive mineral fertilizer (F+M3) increased the average value of the carbon sequestration efficiency (CSE) by 12.9% and up to 26.3%. Combining organic and mineral fertilizers at moderate and higher intensities increased the soil organic matter quantity and quality compared to the unfertilized or manure treatment. Data on the glomalin content can be used to study the organic matter quality. We determined a strong correlation between the total glomalin content and the soil organic matter carbon, fulvic acid content, humic acid content, extractable carbon content, and dissolved organic carbon content, as well as the potential wettability index and aromaticity index.

Spatiotemporal variability of organic carbon in streams and rivers of the Northern Hemisphere cryosphere

The earth's cryosphere is the outpost of climatic warming, which leads to rapid changes of organic carbon (OC) transport from terrestrial to aquatic ecosystems. OC in the cryosphere rivers plays vital roles in the carbon cycle and river ecosystem health. Yet, we still lack a comprehensive assessment of the spatiotemporal patterns of riverine OC across the Northern Hemisphere cryosphere. Here, we compiled OC concentration, radiocarbon (14C), and the specific ultraviolet absorbance (SUVA) of dissolved OC (DOC) at 254 nm data from 1007 unique sites, extracted from 138 published literature between 1972 and 2022. Overall, the average DOC and particulate OC (POC) concentrations are 6.34 and 2.61 mg C L−1, respectively, with the average age of DOC and POC being ~1100 and ~4300 years BP, respectively, indicating the release of aged carbon pools. Seasonal variations in DOC and POC concentrations, Δ14C-DOC and SUVA254 were observed, with distinct spatial variations closely linked to specific watershed characteristics. We found permafrost-impacted watersheds displayed significantly higher DOC concentrations, younger OC ages but lower POC concentrations compared to glacier-impacted watersheds. Meanwhile, in boreal forest watersheds, DOC is the most concentrated and youngest in varied ecoregions. Additionally, in permafrost regions characterized by higher permafrost extent, ground ice content, or lowlands with thick overburden cover, riverine DOC is more concentrated and aromatic. We estimated that specific OC fluxes in glacier rivers are higher than that in permafrost rivers (4.77 and 1.86 g C m−2 yr−1, respectively). Our results highlight the complex and variable spatiotemporal patterns of riverine OC in the northern cryosphere, which are essential for assessing the impact of OC on the global carbon cycle and climate warming.

Carbon and Phosphorus in Volcanic Soils of Mt. Kerinci (Sumatra) After Long Term Tea and Paddy Cultivation

ABSTRACT Volcanic soils are well-known to have a high agronomical value, and in Sumatra, Mt. Kerinci volcanic soils produce one of the highest quality tea and rice. Declining soil organic carbon (C) and high phosphorus (P) retention are two main issues in volcanic soils in the area. Thus, this study aimed to study the dynamic of C) and P content in volcanic soils and to find the main controls of their variation from geochemical signatures. The soils of Mt Kerinci present a unique environment as one part of the area was converted from forest to tea plantation for about 100 years, and a nearby field had been used for paddy rice cultivation for about 200 years. The study was conducted in the Mt Kerinci area covering 5,922 ha in the north comprise of paddy soils (ps) and north tea soils (nts) and the south slope (south tea soils= sts). Soil samples were collected on a grid of 500 × 500 m under tea and paddy (n = 206 samples) at 0–20 and 20–40 cm depth. All soils have similar pH in H2O, but pH in KCl paddy soils (ps) > north tea soils (nts) > south tea soils (sts). The average content of soil organic Carbon (SOC) in paddy soils was 50% less than in the soils of tea plantations. The labile organic carbon content in paddy soils were lower than in soils of tea plantations. Most C was chemically bound to the metal complex. Higher P retention occurred in all soils. The CaO/TiO2 index indicated a weathering sequence of ps > nts > sts. Soil weathering controlled P retention with an increasing P retention as the soils weathered. Overall, the study suggests that cultivation in volcanic soils influenced the geochemical properties of the soils and subsequently their C and P contents.

Geological Characteristics and Controlling Factors of Shale Gas in the Permian Shanxi Formation, the Southern North China Basin

Abstract Energy resources exploration has been taking place in the Southern North China Basin (SNCB) for decades, but no big breakthroughs have been made. A case study focusing on the Lower Permian Shanxi Formation in the Taikang Uplift of the SNCB is presented in this paper; based on the practice of shale gas exploration, we summarize the geological characteristics, geochemical characteristics, mineral characteristics, and pore type and analyze the exploration potential shale gas. The type of organic matter in the studied strata is mainly type III, the vitrinite reflectance (Ro) is between 2.1% and 3.4%, the average total organic carbon content is 1.66%, the mineral of shale is mainly composed of quartz and clay, and the main reservoir space types are mineral pores and microfractures. Through comprehensive evaluation, the sedimentary environment, organic matter abundance, physical properties, and mineral composition control the shale gas accumulation in the studied area.

Geological Characteristics of Shale Reservoir of Pingdiquan Formation in Huoshaoshan Area, Junggar Basin

Unconventional oil and gas, represented by shale gas and shale oil, have occupied an important position in global energy. The rapid growth of shale gas and shale oil production shows great potential for the exploration and development of shale resources. Junggar basin, the main oil-bearing basin in China, is rich in oil and gas resources, so it is of great practical significance to carry out systematic research on the geological characteristics of shale reservoirs in this region. To this end, this paper designates the shale reservoir of Pingdiquan Formation in Huoshaoshan area of the Jungar Basin as the research object, carries out a geological survey in that area, analyzes reservoir forming conditions using the geological interpretation method, analyzes different local trap reservoir types and their main control factors by dissecting the explored reservoir, optimizes and evaluates favorable traps using the source, fault, facies and circle coupling analysis method, establishes single good identification standard of sedimentary microfacies, and carries out well-connected sedimentary microfacies analysis. Using geochemical methods, such as rock pyrolysis, maceral analysis, vitrinite reflectance, kerogen carbon isotope, saturated hydrocarbon chromatography, etc., the abundance and types of organic matter of shale in different intervals are analyzed and the geological characteristics of shale reservoirs are evaluated. This paper aims to analyze the oil and gas content of the shale reservoir in Pingdiquan Formation in the Junggar Basin to provide reliable reservoir evaluation and guide better development of shale oil and gas resources in the future. The innovative expenditure of this paper lies in conducting the research from two aspects: the analysis of the main controlling factors of reservoir formation from the structural point of view and the analysis of the pore structure and geochemical characteristics of shale from the core experiment point of view, and also the classification of organic matter, so as to provide a basis for finding favorable traps. The results show that the shale sedimentary system in the study area is a small fluvial delta, which belongs to a compression structure, with developed NNE-oriented structural belts and faults; the structural form is a short-axis anticline as a whole, forming a structural coil closure at −900 m, with a trap area of 50 km2 and a closure height of 180 m. According to the geological interpretation method, 19 faults of all levels were found in the area and the vertical migration conditions of oil and gas were good. Pingdiquan Formation was oil-bearing, with many vertical oil-bearing strata and strong horizontal independence of the reservoir. The sedimentary thickness of the Permian Pingdiquan Formation in the study area is 300~1200 m and the oil-bearing strata are divided into 3 oil-bearing formations, 9 sublayers, and 22 monolayers from top to bottom. The abundance of organic matter in different strata is generally high, with an average total organic carbon content of 3.53%, an average hydrocarbon generation potential of 18.1 mg/g, an average chloroform asphalt content of 0.57%, and an average total hydrocarbon content of 3011 μg/g, all of which belong to the shale standard, especially Ping-2. The organic matter in different layers belongs to types I-II1, and the organic matter types are I-II1, I-II2, and II1-II2, respectively. The average carbon isotope of shale kerogen is −2.4%, which belongs to type II2 kerogen.

Long-term characterization of organic and elemental carbon at three different background areas in northern Europe

Elemental carbon (EC) and organic carbon (OC) are major components of atmospheric PM2.5. In this article we represent the results of long-term measurements (8–12 years) of EC and OC at three different background sites in Finland: in a rural area (Virolahti) since the summer 2010, in a marine environment (Utö) since the summer 2011, and in a clean arctic environment (Pallas/Matorova) since 2014. The concentrations of OC and EC were measured with a semi-continuous organic and elemental carbon analyser (SC-OCEC) in all the sites. The yearly average concentrations of OC varied between 0.96–3.1, 0.76–1.6 and 0.30–0.69 μg m−3 at the rural (Virolahti), marine (Utö) and arctic (Pallas/Matorova) sites, respectively. Similarly, the corresponding yearly average concentrations of EC ranged between 0.095–0.48, 0.090–0.2 and 0.010–0.086 μg m−3 at those sites. A clear seasonal variation in OC and EC concentrations was observed at each measurement site. OC concentrations were highest during summertime whereas EC concentrations were highest in wintertime. The seasonality of OC was clearest at the Arctic site that had also the largest temperature variation and shortest growing season resulting in a sharp increase in OC concentrations from June to August. At all the measurement sites, OC concentrations gradually increased when the temperature rose over sub-zero temperatures whereas the daily average EC concentrations did not show as apparent temperature dependence as OC. Based on the cluster analysis, highest OC and EC concentrations, and the highest total load for EC (23–32%), at all the sites were detected with the air mass origin of southeast. In the marine environment, the effect of black carbon from ship plumes was investigated. The limit for ship fuel sulfur content changed during the measurement period (in January 2015), but it was not observed to influence the Optical EC concentrations. Overall, long-term, continuous measurements are crucial when the time trends in air quality and the effect of emission mitigation actions are investigated. In this study, a slight decrease in OC was observed at the Marine site, however, a decrease for EC was seen both at the rural and marine sites suggesting that the emission mitigation actions like EURO limits for light vehicles or improved after-treatment systems developed for industry and energy production have already decreased the background concentrations in rural areas.

Self-Sourced Unconventional Tight Marlstone Reservoir Potential from Evaporative Lagoon of Triassic Leikoupo Formation in the Central Sichuan Basin

A breakthrough was made in tight marlstone reservoirs from an evaporative lagoon in the second sub-member of the third member of the Leikoupo Formation (Lei3-2) in the Central Sichuan Basin. The source rock characteristics, reservoir characteristics of the marlstone and geochemical parameters of the oil and natural gas were investigated to evaluate the unconventional hydrocarbon exploration potential of the tight marlstone from the evaporative lagoon. The results revealed that the source rocks were deposited in evaporative lagoon environments, and the average total organic carbon (TOC) content value for the samples was 0.75 wt%. The thermal maturity of the organic matter was relatively high, with a calculated vitrinite reflectance (Rc) of 1.7%. The characteristics of marlstones suggest that the potential source rocks had fair to good hydrocarbon generative potential. The condensate samples had low densities, low viscosities and high thermal maturity, with a Rc value of 1.7%. For the natural gas, the dry coefficient was around 0.90, and the carbon isotopic compositions of methane and ethane was −41.3‰ and −28.4‰, respectively. According to the carbon isotopic compositions, thermal maturity and geological background, the oil and natural gas from Lei3-2 are comparable with the marlstone of Lei3-2. Thus, the oil and natural gas is self-sourced and originates from the marlstone in the Lei3-2. Micropores and microfractures are often detected in the marlstone from Lei3-2, and a gypsum layer is conducive to the hydrocarbon preservation. These results suggest that the evaporative lagoon facies in Lei3-2 have large, self-sourced, unconventional, tight marlstone reservoir potential. This study also enhances the prospects for further oil and gas exploration of evaporative lagoon facies in other basins.

Carbon burial potential of the surface sediment and its associated anthropogenic impacts in the semi-closed area of Bohai Bay

Carbon burial potential in marine sediments plays an important role in global warming. However, they are easily disturbed by human activities in coastal areas. In this study, marine sediment samples were collected from the coastal area of Bohai Bay, and the effects of exogenous inputs on the carbon content and forms were evaluated. Results showed that the carbon content in sediments ranged from 12.45 g/kg to 19.14 g/kg, with an average of 16.23 g/kg ± 2.78 g/kg, and the average organic carbon (C-Org) content is 12.68 ± 1.14 g/kg, which accounts for about 75% of the total carbon storage in sediment. The content of inorganic carbon (CaCO3) did not change significantly, but the content of C-Org in the estuary area was significantly higher than that in other areas. The proportions of active components in C-Org such as light organic carbon (LOC) and neutral organic carbon (NOC) were relatively low, accounting for approximately 9.49% and 18.15% of the total organic carbon, respectively. The spatial distribution characteristics of LOC and NOC were similar to that of C-Org in the study area. This indicates that human activities have increased the content of C-Org and its active components in marine sediments. Although C-Org and its active components are of relatively low abundance, both are easily affected by human activities which increase pollutants associated with the active components of organic carbon in coastal sediments. Therefore, further consideration should be given to reducing the pollutants carried by exogenous inputs, so that cleaner carbon can be buried in the sediments of Bohai Bay.

Study on the Sedimentary Environments and Its Implications of Shale Reservoirs for Permian Longtan Formation in the Southeast Sichuan Basin

Marine–continental transitional shale is one of the most promising targets for shale gas exploration in the Lower Yangtze region. To investigate the sedimentary environments and the regularity of the enrichment of the Longtan shale, multiple techniques including core and thin-section observations, geochemical and elemental analyses, X-ray diffraction, scanning electron microscopy (SEM), and low-pressure nitrogen adsorption (LPNA) were used to analyze the sedimentology, mineralogy, and pore structure of the Longtan shale. The core descriptions and thin-section observations showed that the Longtan shale was deposited in marine–delta transitional environments including delta-front, shore swamp, mixed tidal flat and shallow shelf environments. The Sr/Cu, V/Cr, CIA, EF (Mo), EF (U), and other major and trace element results indicated warm and moist climates and water-reducing conditions in the Longtan period. Both the climate and water conditions were favorable for organic matter production and preservation. The geochemical results showed that the Longtan shale was in the overmature stage (Ro values ranging from 2.4% to 3.57%) and that the average total organic carbon (TOC) content was 5.76%. The pore system of the Longtan shale consisted of inorganic pores with a small number of organic pores and microfractures. The porosity and specific surface area were mainly affected by the TOC and clay mineral contents. An effective combination of brittle mineral particles, organic matter, and clay minerals provided the necessary conditions for pore preservation. The organic pores, intergranular pores in clay minerals, and brittle mineral pores formed the main network system for the Longtan shale. In summary, the lithological combinations, organic geochemistry, and pore structure system were all affected by the sedimentary environments.

Altitudinal Gradients Modify the Ecological Stoichiometry and Enzyme Activities of Soil in a Natural Secondary Quercus spp. Forest of the Dabie Mountains

Understanding the vertical distribution and driving mechanisms behind soil carbon (C), nitrogen (N), and phosphorus (P) contents and enzyme activities along elevation gradients is of great significance for the healthy and sustainable management of forest ecosystems. For this study, the 0–20 cm soil-layer samples of different natural Quercus spp. secondary forests from eight altitude gradients (ranging from 250 to 950 m) were investigated to quantify their physicochemical properties, ecological stoichiometry characteristics, and enzyme activities. The results indicated that the soil nutrient content of natural secondary Quercus spp. forests in the Dabie Mountains was low, with average soil organic carbon (SOC) and total phosphorus (TP) contents of 19.86 ± 3.56 g·kg−1 and 0.68 ± 0.10 g·kg−1, respectively, which were 19.14% and 12.82% lower, respectively, than the Chinese average. In terms of vertical spatial distribution, the SOC, total nitrogen (TN), and TP contents of the soil at high altitudes (≥750 m) were greater than those at middle- and low-altitude areas and reached the maximum value at or near the top of the mountain (850–950 m). The stoichiometric attributes of the soil ecosystem fluctuated with the higher altitudes in vertical space; however, the fluctuation range was not significant. The C:N, N:P, and C:P ratios reached their maximum values at altitudes of 250, 750, and 850 m, respectively. However, the overall average value remained generally lower than the national average; thus, in forest management, attention should be paid to the supplementation of the soil with C and P. The activities of soil sucrase, urease, acid phosphatase, and catalase were interconnected across the overall space, and increased with altitude. The SOC, TP, and pH were the main factors that influenced the changes in soil enzyme activities.

Hydrocarbon generation and retention potential of Chang 7 organic-rich shale in the Ordos Basin, China

This study investigates the hydrocarbon generation and retention potential of Chang 7 organic-rich shale, with an emphasis on the producibility of retained hydrocarbons, using a sample set chosen to represent a maturity spectrum of 0.54–0.9% R o and organic matter of type II and mixed type II–III. Based on the present-day hydrogen index (HI pd ), the sample sets were divided into three sections: Upper, Middle and Lower. The three sections have a high hydrocarbon generation potential, with an average original total organic carbon (TOC o ) content of 12.27, 3.10 and 5.13 wt%, of which 49.39, 23.62 and 49.86 wt% represents generative organic carbon (GOC), and an original hydrogen index (HI o ) of 581.27, 278.05 and 586.82 HC g −1 rock in the Upper, Middle, and Lower sections, respectively. The bulk of the analysed samples exhibited moderate–high oil saturation, yet the oil crossover effect was only observed in two organic-rich samples, indicating organic-rich shale-oil resource systems. The sorption capacity of organic matter controls oil retention in the Chang 7 shale system, where the oil saturation index increases with increasing maturity in the oil window until a maximum retention capacity of about 82–83 mgHC g −1 TOC is reached at a vitrinite reflectance of 0.8% and thereafter decreases with further maturity. Supplementary material: A detailed spreadsheet of the back-calculated original geochemical parameters using the mass-balance method of Jarvie (2012 a ) is available at https://doi.org/10.6084/m9.figshare.c.6387577

Distribution characteristics and optical properties of carbonaceous aerosol: brown carbon and black carbon in Nanchang, inland China

PM2.5 samples were collected from October 31, 2019, to November 10, 2019, in Nanchang for 10 consecutive days. The mass concentrations of PM2.5 and carbon components were measured, and the distribution characteristics of carbonaceous aerosols were discussed. The optical properties of carbonaceous aerosols were quantified by the thermal-optical method and solvent extraction method, respectively. The results showed that the average concentrations of organic carbon (OC) and elemental carbon (EC) in aerosols in Nanchang were 11.79 ± 3.86 and 3.51 ± 1.59 μg m−3, respectively. The average OC/EC was 3.62, and OC2, OC3, OC4 and EC1 accounted for relatively large proportions (19.55, 24.96, 22.37 and 17.38%). Carbonaceous aerosols in Nanchang were greatly affected by coal combustion, vehicle exhaust emissions and secondary organic carbon (SOC) formation. For particulate brown carbon (BrC), the average light absorption coefficient (babs) and mass absorption efficiency (MAE) at 405 nm were 16.87 Mm−1 and 1.49 m2g−1, respectively. The average Absorption Ångström exponent (AAE) was 8.58. For water-soluble organic carbon (WSOC) and methanol-soluble organic carbon (MSOC), the average babs,365,WSOC and babs,365,MSOC were 14.79 and 22.51 Mm−1, respectively. The mean values of AAE300-600,WSOC and AAE300-600,MSOC were 4.17 and 4.84, respectively. The mean MAE365,WSOC and MAE365,MSOC were 1.83 and 2.18 m2 g−1, respectively. The mean value of MAEBC at 405 nm was 10.28 m2 g−1. The optical properties of particulate BrC and dissolved BrC were similar at 405 nm. The light absorption of BrC cannot be ignored, although BC was the main light absorption component.

Secondary formation and source analysis of carbonaceous components in PM1 in a typical city, Southwest of China

Carbonaceous components are major components of PM1, which have a significant impact on climate change, air quality and human health. However, the secondary formation and source analysis of carbonaceous components in PM1 are still unclear. Therefore, in order to study the secondary formation and sources of carbonaceous components in PM1, PM1 samples were collected in Chengdu, a typical city located in southwest of China, from 2018 to 2019. The concentrations of organic carbon (OC), elemental carbon (EC) and isotopic compositions of carbon (δ13C) in PM1 were determined using a thermal/optical carbon analyzer and elemental analyzer-isotope ratio mass spectrometer. In addition, the δ13C values from relevant potential sources (C3 plants, C4 plants, vehicle exhaust and coal) were also determined. The results showed that the annual average concentrations of OC and EC in PM1 in Chengdu were 6.43 ± 3.30 μg·m−3 and 1.99 ± 0.98 μg·m−3, accounting for 13.83% and 4.28% of the PM1 mass concentration, respectively. The concentrations of OC in PM1 ranked in the order of winter > summer > spring > autumn, while the concentrations of EC varied in the order of winter > spring > autumn > summer. The concentrations of OC and EC in PM1 reached the maximum in winter, mainly due to the special meteorological conditions and significantly higher pollutant emissions. The correlations of OC and EC were higher in spring, autumn and winter, and lower in summer. It showed that OC and EC might have the same sources in spring, autumn and winter, while the sources of OC and EC were relatively complex in summer. The annual average concentration of secondary organic carbon (SOC) in PM1 was 2.23 ± 1.22 μg·m−3. The concentrations of SOC were higher in autumn and winter and lower in spring and summer. The special meteorological conditions and significantly higher pollutant emissions are important reasons for the higher SOC concentrations in winter. On the other hand, the low temperature in winter can also promote the formation of SOC. The results of carbon isotopic compositions indicated that the carbonaceous components in PM1 were mainly derived from vehicle exhaust (52.4%), C3 plants combustion (26.2%), coal burning (16.2%) and C4 plants combustion (5.2%). The findings help to deepen the understanding of the secondary formation and sources of carbonaceous components in PM1 and provide theoretical guidance for environmental management.

Chemical characterization of marine aerosols from two cruises over the South China Sea: Importance of biomass burning and secondary formation

Total suspended particle (TSP) samples were collected during June–July 2015 in the northern South China Sea (NSCS) and August–September 2016 in the western South China Sea (WSCS). Water-soluble ions (WSIs), organic carbon (OC), elemental carbon (EC), and organic compounds were measured. The average concentrations of WSIs, OC, EC and organic compounds were 19.4 ± 10.9 μg m−3, 2.48 ± 1.54 μgC m−3, 0.31 ± 0.25 μgC m−3 and 789 ± 217 ng m−3 in the NSCS, and were 10.2 ± 4.71 μg m−3, 1.76 ± 1.82 μgC m−3, 0.43 ± 0.32 μgC m−3 and 781 ± 342 ng m−3 in the WSCS. In both cruises, sea salt ions (Na+ and Cl−) and secondary inorganic ions (SO42−, NO3−, and NH4+) were the main species of WSIs, accounting for 54.0 % and 43.6 % in the NSCS, and for 35.0 % and 54.0 % in the WSCS. The secondary products (dicarboxylic acids and aromatic acids) (NSCS: 73.3 %; WSCS: 73.9 %) and saccharides (NSCS: 19.0 %; WSCS: 18.0 %) accounted large fractions of organic compounds in aerosol particles over the SCS. These results suggest sea salt emissions and secondary formation are the main sources of the aerosols over the SCS in summer. The positive correlations between the biomass burning tracers (nss-K+ and levoglucosan) and OC as well as organic compounds indicated that biomass burning from nearby continents was also an important source of organic aerosols over the SCS. Based on back-trajectory analysis and satellite fire spots, Indochina Peninsula and China were proposed as the main continental source areas of non-sea salt WSIs and organic compounds. Our results highlight the significant contribution of continental outflow especially biomass burning and photochemical secondary oxidation to the organic compositions of aerosol particles over the SCS in summertime.

Physical property differences of source rocks in the Lucaogou Formation and adsorption ability variation under their influence

Shale gas exploration is very important for the China in the further. There are many findings of shale gas in Northwest China, especially in Junggar Basin Permian Lucaogou Formation of the Xinjiang Uygur Autonomous Region. However the basic geological characteristics of Lucaogou Formation is not still clear. In order to solve this problems, Quanzijie shale gas collected from the southern margin of the Junggar Basin is taken as the study area, and shale gas resources are investigated and evaluated using the organic-rich shale section. On this basis, the investigation and evaluation of shale gas resources in the Lucaogou Formation is performed. The reservoir performance, preservation conditions, compressibility, and gas-bearing properties of gas-bearing shale intervals are identified. The results are as follows: The vertical and horizontal lithological and lithofacies variations of the source rocks of the Lucaogou Formation are clarified. This layer is characterized by the upward thinning of grain size and the upward darkening of color in the vertical direction. The layer can be divided into upper and middle-lower sections, with organic shale being most developed in the upper section, and sandstone and dolomite being more developed in the middle and lower area. The main hydrocarbon source rocks are developed in the upper area of the Lucaogou Formation. The total thickness of the hydrocarbon source rocks is 78.12–513.73 m. The lithology is mainly gray-black shale, silty mudstone, and oil shale. The average organic carbon content is 4.86%. The maturity of the organic matter is mainly 0.7–0.8%. The shale reservoirs have a high content of brittle minerals, but the physical properties both of the shale and sandstone reservoirs are poor. These are generally ultra-low porosity and ultra-low permeability reservoirs, in which the oil and gas reservoir space is mainly fractures.

宁夏草地土壤有机碳空间特征及其影响因素

PDF HTML阅读 XML下载 导出引用 引用提醒 宁夏草地土壤有机碳空间特征及其影响因素 DOI: 10.5846/stxb202201040022 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（42061037） Spatial characteristics of soil organic carbon in grassland of Ningxia and its influencing factors Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:草地是重要的碳汇资源库，在陆地生态系统碳循环中扮演着重要角色。探明草地土壤有机碳的空间分布格局及其影响因素对于推动区域生态系统碳汇管理，实现"双碳"目标和绿色高质量发展具有重要意义。以宁夏三种主要草地类型为研究对象，基于野外样点调查，采用结构方程模型，分析了草地土壤有机碳的空间分布特征及其影响因素。结果表明：不同类型草地土壤有机碳含量表现为草甸草原高于典型草原，荒漠草原最低，垂直剖面上均随土壤深度的增加而降低。草甸草原和荒漠草原有机碳空间变异自表层向下逐渐增大，典型草原在20-40 cm土层变异系数达到最大。有机碳分布在区域上从南部六盘山山地向中部干旱风沙带逐渐降低。路矩分析发现，海拔高度、地上生物量、降水量、温度和土壤含水量可解释土壤有机碳空间变异的91.4%。海拔高度对土壤有机碳总效应最大（作用系数为0.78），海拔高度引起的降水和温度等要素区域分异间接影响土壤有机碳含量；地上生物量对土壤有机碳的直接正向效应最大（0.559）；降水量对土壤有机碳效应分为直接效应和作用于生物量及土壤含水量的间接影响；温度表现为通过生物量对土壤有机碳间接产生负向效应（-0.259）。宁夏草地土壤有机碳的空间分布主要受降水量和与其密切相关的生物量的支配作用。近20年来降水量增多和草地人为干扰减少，宁夏草地碳汇作用显著。 Abstract:Grasslands are important contributors of carbon sequestration among terrestrial ecosystems, which play an important role in the global biogeochemical cycle and energy exchange. Based on field surveys in July-August 2021, soil samples of meadow steppe, typical steppe and desert steppe in Ningxia were collected. The organic carbon contents, bulk density, total nitrogen, and pH of these soil samples were measured. We also monitored factors affecting carbon distribution such as altitude, annual precipitation, annual mean temperature, aboveground biomass and soil water content. Results indicated that content of the soil organic carbon decreased along the vertical soil profile, the average organic carbon content followed the order of meadow steppe > typical steppe > desert steppe. The distribution of grassland soil organic carbon gradually decreased from the Liupan Mountains in the south to the dry sand belt in the middle along the altitude. Soil organic carbon was significantly positively correlated with aboveground biomass, annual precipitation, altitude and soil total nitrogen density, and significantly negatively correlated with annual mean temperature (P<0.001), positively correlated with soil water content, and negatively with soil bulk density (P<0.01), and no obvious correlation with soil pH. Amos structural equation model was applied to evaluate the combined effects of environmental factors on grassland soil organic carbon. The most important factors affecting organic carbon was altitude (r=0.78), which mainly caused regional differentiation of precipitation and temperature to affect soil organic carbon indirectly; followed by aboveground biomass (r=0.559); then annual precipitation (0.539), which not only directly but also indirectly affected the soil organic carbon by altering aboveground biomass and soil water content positively. Annual mean temperature indirectly affected organic carbon negatively by influencing aboveground biomass (r=-0.259). The spatial distribution of grassland organic carbon in Ningxia was dominated by precipitation and aboveground biomass closely related to precipitation. In the past 20 years, with the increase of precipitation and the reduction of grassland anthropogenic disturbance, grassland ecosystem in Ningxia had a very significant carbon sink function. 参考文献 相似文献 引证文献

An Appraisal of Fertility Status of Problem Soils of Tiruchirappalli District in Cauvery Delta Zone, Tamil Nadu, India

Soil fertility is an important factor for plant growth and has a global impact on both developed and developing countries. The present investigation was carried out on soil fertility status of farm in ADAC&amp;RI, Trichy which comes under the Cauvery Delta Zone of Tamil Nadu. The pH value indicates that ADAC&amp;RI farm soils are very strongly alkaline in nature. The rating of electrical conductivity was normal with values ranging from 0.16 – 0.72 dS m-1. The farm soil was low in available nitrogen, medium to high in available phosphorus and potassium. The average organic carbon content was low in the farm soil with values of 4.09 and 4.33 g kg-1 in A and D block, respectively. The available sulphur content of the farm was recorded as sufficient. This study clearly shows that, most of the soil nutrients in the ADAC&amp;RI, farm was found to be low and need proper management practices to improve the soil quality for better crop production. The present investigation reveals the effect of sodicity on the status of available nutrients in soil.