Humus Type Research Articles

Soil acid-base buffering in the step agriculture lands

Modern studies of chernozem soils in the northwestern Black Sea region have shown intense dehumification due to disruption of biogeochemical cycles caused by anthropogenic removal of organic matter and associated biophile elements. At former time, the humus zoning was typical for southern chernozems and now we noted the smoothing of this zoning. Acid-base buffering has a significant role in counteracting degradation processes, the buffering parameters could be integral indicators of soil chemicals balance. We studied the automorphic soils (arable chernozems) of the northwestern Black Sea region, their humus state, particle size distribution, and acid-base buffering parameters. We studied ordinary modal and micellar-carbonate chernozems on arable land and 40-year-old fallows, southern chernozems removed from irrigation 15 years ago and southern carbonate chernozems of the second floodplain terrace of the Danube River. We determined the neutralization index, degree of buffering capacity in the acid and alkaline ranges, equilibrium coefficient, and sodium absorption ratio to characterize the acid-base buffering. The studied soils belong to stable buffer agriculture lands by their acid-base buffer ability. We determined that soils have the parameters of chernozem type: low humus content, humate and humate-fulvate type of humus, average content of insoluble residue, high degree of humification, heavy-medium loam particle size distribution, and neutral soil solution. The acid-base buffer capacity is characterized by average values, the buffer capacity in the acid interval increases with depth, while decreases in the alkaline interval. We revealed a significant correlation between the ability to counteract the acid load and the content of physical clay. We believe that the agricultural use of southern chernozems leads to a decrease in soil resistance to acidification.

Características de la actividad enzimática y el humus en suelos de chinampa.

The chinampas are protected natural areas that have suffered degradation due to saline contamination and type of management. The objective was to study enzymatic activity and type of humus in chinampas with different salinity, land use and geographical location. Forty-five soil samples were studied, 15 at each site (Xochimilco, San Gregorio Atlapulco (SGA) and Tláhuac). Each site had a different use: five had pastures, five had agricultural crops and five were abandoned. pH, EC, saline ions, enzymatic activity (glucosidase, phosphatase, urease, sulfatase, catalase and dehydrogenase) and carbon in humic substances were evaluated. EC, PSI and pH classified the cultivated soils of SGA and Xochimilco as saline, but in Tláhuac the soils of abandoned and pasture chinampas were sodic saline. Geographic location and land use changed enzyme activity (except for urease and glucosidase) and characteristics of the humus [percentages of carbon of humic acids (HA) (humic acids), fulvic acids (FA), and humins]. There were statistical differences (Tukey P < 0.05). The cultivated soils had more urease, phosphatase and sulfatase activity, while in the pasturelands dehydrogenase and catalase were more active. Higher carbon content in AH was found in pastureland and chinampas of Tlahuac, while in SGA and abandoned chinampas carbon content was higher in FA.

Genesis and origin of natural gas in the Beidagang structural belt of Dagang oilfield

The south and north of Beidagang structure zone in Dagang oil field are Qikou sag and Banqiao sag respectively, it´s belong typical “two sag one uplift”, has abundant oil and gas source, developing reservoir condition is good. From now it has find various types of gas reservoirs in several heavy reservoirs and series of strata, so it has complex oil genesis and gas. This article collected a large number of natural gas samples systematically, launching a study on the composition and carbon isotope of natural gas, identifying the overall characteristics and causes of natural gas in Beidagang structure zone.Research shows in Beidagang structure zone, different heavy reservoirs and series of strata about composition and carbon isotope of natural gas are basically the same, methane contant is low, dry coefficient is small, spreading 0.8-0.89, belong typical wet gas. The distribution of methane and ethane carbon isotope are wide, insisting humic-type natural gas, sapropelic natural gas and biogas.Biogas are mainly distributed in Gangxi area, Banzhong, Bannan, Banbei, Tangjiahe, Baishuitou, Gangdong and Qianmiqiao area’s natural gas mainly is mainly the product of hydrocarbon source rock saprophytic organic matter mature stage in san-segment of Banqiao depression, Maxi ang Madong natural gas is the product of hydrocarbon source rock humus type organic matter mature stage of shahejie formation from Qikou depression. At present, the natural gas from the high over-maturity stage of the deep hydrocarbon source rocks in the depression is seldom distributed in the Beidagang structural belt, showing gas exploration in deep sag has a bright prospect.The high over mature stage natural gas in deep sag and Qikou depression Saproped-type hydrocarbon source rock crude oil cracking gas are important exploration target.

Post-pyrogenic Evolution of Sandy Soils under Pine Forests in the Baikal Region

The development of sandy soils under pine forests and the influence of forest fires on the soil properties have been studied in the Baikal region, The profile of background soils consists of a litter layer and a thin humus-accumulative horizon with features of grain bleaching in the lower part. In the WRB system, such soils are classified as Eutric Arenosols (Ochric). They have an acid reaction, fulvate humus, and slightly developed features of the Al–Fe-humus process. Post-pyrogenic soil successions depend on the type of fire. In fifteen years after the ground fire, a soil with specific pyrogenic horizons in the upper part of the profile was formed. It had a high content of carbonaceous matter and humus, a slightly acid reaction, and a relatively high content of exchangeable and total calcium. The soil humus was of the fulvate–humate type, and the humus pool considerably increased. These changes were related to the presence of charcoal microparticles adsorbing dispersed substances on their surface and detected in thin sections. After the crown fire with the destruction of the tree stand and activation of wind erosion, the features of pyrogenesis were poorly expressed in the soils. In this case, post-pyrogenic soils had a weakly developed immature profile, acid reaction, and a low content of humus of the humate–fulvate type. The properties of the background soils allow us to classify them as podzolized humic psammozems (Eutric Arenosols (Ochric)); the soils of post-pyrogenic successions after the ground fire can be classified as post-pyrogenic humic psammozems; after the crown fire, as humic psammozems.

Hydrocarbon biomarkers and isotopic composition of carbon from bitumoids and oils of Mesozoic sediments in the western part of the Yenisei-Khatanga oil and gas region

Based on analyzes of carbon isotopic composition, distribution and composition of hydrocarbon biomarkers of oils and bitumoids from source rocks of the Mesozoic sediments in the western part of the Yenisei-Khatanga oil and gas region and the northeast of the West-Siberian plate, two groups of oils and bitumoids are identified, genetically associated with organic matter, mainly sapropel type (I group) and mainly humus type (II group). The genetic correlation of oils and bitumoids has been made. Possible foci of generation, which participated in the formation of hydrocarbon deposits, have been determined.

Gas Diffusivity in the Forest Humus Layer

While several diffusivity models have been developed for mineral soils, there are few data for the forest humus layers that overlie, and are distinct from, the mineral soil. We measured soil gas diffusivity of the organic layer of spruce and beech stands. Total pore space and relative soil gas diffusivity were much higher in the humus layer than in mineral soil. An exponential diffusivity function was used to describe relative soil gas diffusivity in the humus layer of all spruce sites using one parameter set. The best-fit parameters exceeded the range recommended for mineral soil, indicating the distinctness in pore structure of mineral soil and the organic layer. Different model parameter sets were required to describe the different types of humus at the beech sites. As a consequence, traditional predictive models developed for mineral soil should not be used to derive diffusivity values to interpret the aeration status of the forest humus layer. Specific parameter sets should be used for calculating soil gas fluxes through these layers using the gradient flux approach.

ЭКОЛОГИЧЕСКАЯ УСТОЙЧИВОСТЬ ГУМУСА ПОЧВ ЗАПАДНОЙ СИБИРИ

The paper analyzes the issue of environmental sustainability (ES) of the system of humus substances. The main problem in studies of ES consists in determination of its most informative criteria. Besides the bioclimatic indices, the characteristics of humus such as its content, type of humus and degree of humification of organic matter were ascertained to be included into the number of obligatory criteria of ES. Additional study of humic acids as more chemically and biologically sustainable soil organic substances showed that the fraction of calcium humates (combined with exchangeable calcium) proved to be the most informative criteria of ES. The most representative data on ES are obtained at simultaneous study of virgin and arable soil samples.

Organic petrography and petroleum source rock evaluation of the Cretaceous Mamfe Formation, Mamfe basin, southwest Cameroon

The Mamfe basin is thought to be a rift splay segment of the southern Benue Trough and is genetically link to the Abakaliki and Anambra sub-basins in Nigeria. In the Mamfe basin very little studies have been done on maceral characterization and hydrocarbon generative potential of the Cretaceous black shale. Organic petrography and Rock–Eval pyrolysis studies were done on the black shale outcropping in the basin. The objectives were to determine the types of macerals present, and their relative abundance as well as their hydrocarbon generation potential; to assess the black shale's source rocks richness and quality; and to evaluate the source rock thermal maturity and the relationship between maturity and hydrocarbon generation. The results of this investigation indicated that the maceral content include relatively low percentages of vitrinite (4.9%), inertinite (3.4%) and scare liptinite (0.5%). The total organic carbon of the samples vary from 0.17 to 4.53 wt%, (mean = 1.11 wt%) indicating poor to good source rocks generative potential while the S1 values ranges from 0.04–1.25 mg HC/g rock, (mean = 0.23 mg HC/g rock), indicating poor–fair source rocks generation potential. Most of the samples are mature-peak mature for gaseous hydrocarbon generation. Based on the organic petrography and geochemical analyses performed on the black shale samples of the Mamfe Formation, they are described as mainly humic type III-reworked/oxidized type IV kerogen. The genetic potential of these source rocks is low and free hydrocarbon are absent. Given the prevalence of type III/IV kerogen, thermal maturity levels and hydrocarbon yield, it can be concluded that the source rocks of the Mamfe Formation have some moderate to fair potential for gaseous hydrocarbon which have not yet been generated at the present outcrop levels.

Molecular structure-reactivity correlations of humic acid and humin fractions from a typical black soil for hexavalent chromium reduction

Different soil humus fractions are structurally distinct from each other molecularly, however, the relationship between their microscopic molecular structures and the macroscopic reduction of Cr(VI) is still unknown, especially for the humin fraction. In this study, different humus fractions (HA, humic acid; HMi, humin linked to iron oxides; HMc, humin linked to clay; and HMr, humin residue) were sequentially extracted from a typical black soil and well characterized. It was found that HA, HMi and HMc were the same type of humus with similar molecular structures, while HMr was structurally different from the other fractions with a high cellulose content. The removal rate of Cr(VI) in solution decreased with progressive humus fractionation, namely, HA > HMi > HMc > HMr. Based on the two-dimensional correlation spectroscopic analysis (2DCOS) of the FTIR data, the changing functional groups of all humus fractions during reacting with Cr(VI) followed a similar order: carboxyl > phenol > hydroxyl > methyl > methylene. According to the correlation analysis, Cr(VI) reduction rates by different humus fractions were mainly determined by the content of phenol (R2 = 0.99) instead of carboxyl (R2 = 0.28). Except for HMr, the Cr(VI) reduction rates of different humus fractions were also positively correlated with surface and bulk polarity (R2 = 0.98 and 0.99) but not with aromaticity or aliphaticity (R2 = 0.21).

THE MICROMORPHOLOGY AND MINERALOGY OF GRAY FOREST SOILS IN VLADIMIR OPOLYE

The investigations were conducted on the gray forest heavy clay loamy soils, formed on the loess-like loams, which are widely spread on the territory of Vladimir Opolye. The eluvial-illuvial profile differentiation, its different intensity and the specificity of illuvial coatings (fine dispersed clayey and humus-clayey coatings with sparse skeletal content of soil) is confirmed. The presence of the coarse wooden plant residues, thick humus-clayey illuvial coatings within the illuvial horizons speak about the forest origin of the grey forest soils in Vladimir Opolye. The micromorphology of humus horizon reflects the direction of the soil forming process and the ecological status of soils. The illimerization is the main process of the matter migration and soil profile differentiation. The mixed-layer formations prevail in the clayey fraction. Mica, quartz, and K-feldspars are the prevailing compounds of the fine and medium silt within the gray forest soils. In the silt fraction of the second humus horizon prevail quartz and feld-spar. The most of the nutrients is concentrated in the clayey and fine-silt frac-tion. The micromorphological investigations confirmed the theory, which speaks about the presence of forest (the presence of illuvial coatings) as well as steppe soils (mull humus type in the SHH, the presence of primary and newly formed carbonates) specificities in the modern soil forming process within the gray forest soil of Vladimir Opolye.

Genesis of Oils in Eastern Kamchatka: Evidence from Hydrocarbon Biomarkers

Gas chromatography and gas chromatography–mass spectrometry data on oils from wells and seeps in the Eastern Kamchatka Basin indicate that, according to their composition and the distributions of biomarker molecules, these oils can be classified into three groups, which differ in the composition of the parent organic matter, litho–facies sedimentation conditions, and catagenetic transformations. Oils from the wells were determined to be produced by organic matter of the sapropel type of marine facies in the main oil window (MC2). Condensate from the natural seep was generated at higher catagenesis grades (MC2–3) by organic matter of the sapropel–humus type of littoral facies. Uzon oil shows are demonstrated to be formed in a continental environment by organic matter of the humus–sapropel type and were not genetically related to oil from the Paleogene–Neogene source rocks of the Bogachevka Formation.

The soils of mountainous territories (in the Russian)

Specific soils of mountainous regions having no analogues on plains occupy less than 3% of Russia. On the soil maps of Russian Federation (1 : 2.5 M scale, 1988), they are represented by 10 mapping units, the names of which, along with the term “mountainous” reflecting characteristic properties of these soils (general youth, thin profiles, high content of gravels, underlying by hard bedrock) contain information about the particular landscape conditions of soil formation. For updating of the map, the soils shown on it are renamed in agreement with the new Russian substantive-genetic soil classification system. The profile-genetic approach lying in the basis of this system excludes the use of landscape terms in soil names. The reclassification of mapping units is performed with due account for individual features of each particular polygon shown on the map. In essence, it consists of the search of information about the soil properties for identification of the diagnostic horizons and genetic properties of the soils to give formulae of their horizonation (in symbols of diagnostic horizons and properties). This search is based on the program and explanatory text to the map and various regional publications presenting information about the soils and the agents of soil formation. The formulae of the profiles are used to determine classification position of the soils in the substantive-genetic classification system. Most of the soils from this section of the legend belong to the order of organo-accumulative soils. The differences between them are related to differences in the types of humus and surface organic horizons. In the case of the low thickness of the profiles, the soils belong to the orders of lithozems and/or poorly developed stony soils (petrozems). As a rule, the same unit in the legend to the map corresponds to two or more soils in the new classification system. The mapping unit “mountainous forest-meadow soils” has been subdivided into five different soils with due account for the regional specificity of soil properties and landscape features. In the course of this study, several suggestions to improve the classification system of Russian soils have been made.

Polycyclic Aromatic Hydrocarbons Content in Contaminated Forest Soils with Different Humus Types

The aim of the study was to determine polycyclic aromatic hydrocarbon (PAH) content in different forest humus types. The investigation was carried out in Chrzanów Forest District in southern Poland. Twenty research plots with different humus types (mor and mull) were selected. The samples for analysis were taken after litter horizons removing from a depth of 0–10 cm (from the Of- and Oh-horizon total or A-horizon). pH, organic carbon and total nitrogen content, base cations, acidity, and heavy metal content were determined. In the natural moisture state, the activity of dehydrogenase was determined. The study included the determination of PAH content. The conducted research confirms strong contamination of study soil by PAHs and heavy metals. Our experiment provided evidence that different forest humus types accumulate different PAH amounts. The highest content of PAHs and heavy metals was recorded in mor humus type. The content of PAHs in forest humus horizon depends on the content and quality of soil organic matter. Weaker degradation of hydrocarbons is associated with lower biological activity of soils. The mull humus type showed lower content of PAHs and at the same time the highest biological activity confirmed by high dehydrogenase activity.

Factors responsible for Ixodes ricinus nymph abundance: Are soil features indicators of tick abundance in a French region where Lyme borreliosis is endemic?

In Europe, the hard tick Ixodes ricinus (Acari: Ixodidae) is the main vector of Lyme borreliosis spirochetes (Borrelia burgdorferi sensu lato group). A field study was conducted to evaluate the abundance of Ixodes nymphs in the French region of Alsace, where Lyme borreliosis is endemic, and to determine whether environmental factors such as soil moisture and composition may be associated with nymph abundance. In the ten sites studied, ticks were collected by drag sampling from March to October in 2013 and 2014. Temperature, relative humidity, saturation deficit, soil pH, humus composition and type of vegetation were recorded at each site. The abundance of I. ricinus was highly variable from one site to another. Inter-annual variations were also observed, since the nymph abundance were higher in 2013 than in 2014. This study shows that humus type can be indicative of nymph abundance. Three types of humus were observed: (1) moder, (2) mull, and (3) mull-moder humus. One of them, moder humus, which is characterized by a thick layer of fragmented leaves, was found in multivariate analyses to be strongly associated with the nymph abundance. This study demonstrates that factors such as saturation deficit do not suffice to explain the differences in nymph abundance among sites. The composition of the soil and especially the type of humus should also be taken into consideration when assessing acarological risk.

Geochemical characteristics of natural gases from different petroleum systems in the Longgang gas field, Sichuan Basin, China

Located in the Sichuan Basin, China, the Longgang gas field consists of three vertically developed petroleum systems with the Triassic Leikoupo Formation as a dividing interface. There is one marine petroleum system below the interface and one continental petroleum system above it. The marine petroleum system is composed of coal measures, the main source rock in the Longtan Formation, and marine reef reservoirs in the Changxing and Feixianguan formations. The continental petroleum system can also be subdivided into two sets. One is the Xujiahe petroleum system sourced from the Xujiahe coal measures in the Upper Triassic formation. The other is a Jurassic petroleum system that is sourced from Jurassic lacustrine black shales. The gas pools in the marine system contain H2S gas. The gases are very dry and the δ13C1 and δ13C2 values display less negative values with an average of −29.2 and −25.0‰, respectively. The gases are humic origin generated at highly to over mature stages from coal measures of the Longtan Formation. The natural gas in the continental petroleum system does not contain H2S. The natural gases from the Xujiahe petroleum system are mainly wet gases with a few dry gases, and belong to typical humic type sourced from coal measures of the Xujiahe Formation. All the gases from this Jurassic petroleum system are wet gases and the alkane gases show more negative carbon isotopic values typical of sapropels. These are derived from the lower Jurassic lacustrine black mudstone. The three sets of petroleum systems in the Longgang gas field are vertically well separated. Each system has its own source rock, and there are no gases from other sources despite multiple tectonic events in the past. The reservoirs had been in a relatively stable tectonic condition with excellent seals by cap rocks during the gas accumulation period.

Tree species effects are amplified by clay content in acidic soils

The tree species composition of many forests in western and central Europe has changed considerably over the last century, as large areas of mixed deciduous forests were replaced by conifer plantations. In this study, we aim to evaluate whether conversion of mixed broadleaved forest to Norway spruce (Picea abies) on the acidic soils of the Gaume forest (southern Belgium) affected soil quality in terms of soil acidity, exchangeable calcium and aluminium, humus type and earthworm communities, and determine whether this effect is mitigated or amplified by an edaphic gradient in clay content. In this ancient deciduous woodland, stands were partly converted from mixed deciduous forest to Norway spruce monocultures 30–60 years ago. A twin-plot setup was established, where we sampled pairs of adjacent deciduous and Norway spruce plots along a gradient in clay content varying between 3 and 34%. This design allowed to evaluate the effects of soil type and conversion independently. In the deciduous plots, forest type ranged from mixed oak-hornbeam forest to oak-beech forest. The first has a higher clay content, higher exchangeable calcium, mull humus type, low forest floor mass and the presence of burrowing earthworms (endogeics), while the latter is characterised by high forest floor mass and presence of only litter-dwelling earthworms (epigeics), respectively. Our results provide evidence that the natural biogeochemical gradient converges to a narrow and acid range after conversion. When comparing Norway spruce plots with adjacent broadleaved stands, topsoil pH, calcium concentrations and total earthworm biomass were significantly lower, endogeic and epi-anecic earthworms were mostly absent, and the exchangeable aluminium was significantly higher. Contrary to the current paradigm, the impact of conversion in these acidic soils is largest for the stands with the highest clay content, where the larger exchange capacity allows greater accumulation of exchangeable aluminium when pH becomes sufficiently low. These findings have important implications for forest management: for systems near a threshold in soil process domain, it is important to realise that the sites with higher CEC and more favourable pH-values are the ones that will have larger trajectories and deteriorate the most upon acidification. Hence restoring such stands into more natural deciduous or mixed forest may become increasingly difficult.

Classification of humus forms in Caspian Hyrcanian mixed forests ecoregion (Iran): Comparison between two classification methods

Temperate forest productivity and functioning may be explained by complex interactions among tree canopy composition, topographic conditions, climate, morphogenetic identification and classification of humus forms. In this study, we report the main morphological feature of humus profiles classified according to both American (AHCM) and European (EHCM) classifications under the six most common forest stands in northern Iran, i.e., Alnus subcordata (AS), Acer velutinum (AV), Fagus orientalis-Carpinus betulus (FO-CB), Carpinus betulus (CB), Fagus orientalis (FO), and Fagus orientalis-Carpinus betulus-Parrotia persica (FO-CB-PP). Organic and organic-mineral layers samples were collected in 61 permanent plots (20 × 20 m) within a 30 × 30 cm metal frame, for identification. Our result showed that Mull was the dominant humus system according to both classifications, whereas Mor (AHCM) and Amphi (EHCM) were the less frequent humus systems in the study area. Mull and Amphi (EHCM) were dominant at the lowest slope and altitude under AS canopy cover; Moder was usually present at intermediate slope and altitude under FO-CB and FO-CB-PP; while Mor was the dominant form at intermediate slopes and highest altitudes under FO and FO-CB. Due to the temperature changes and litter decomposition, altitude seems to be the best predictor of humus type and litter thickness. Our findings also indicate that EHCM could be preferred in the identification and classification of humus forms in temperate deciduous forests in Iran.

The impact of heavy metals on the soil fauna of selected habitats in Niepołomice forest

Pollution of soils with heavy metals is particularly dangerous to living organisms. Invertebrates are sensitive to changes in soil conditions, and, therefore, may be considered invaluable indicators of soil disruptions. This study has been undertaken to determine heavy metal content in the in soil and extracted soil fauna in two types of forest habitats of Niepolomice Forest and to establish their impact on pedofauna– their density, diversity and trophic structure. The investigated sites varied in the soil or humus type, and the composition of forest stand and ground cover. The analysis of the pH value showed that the studied soils had acidic (pH 4.45-4.85). Small differences were observed in the content of heavy metals (lead, cadmium, nickiel, zinc and copper) in soil humid forest and fresh mixed forest. It results from the studies that the heavy metal content did not exceed the standards set out for the soils of Poland . The bioconcentration factor shows that both saprophytes and predatory invertebrates collected the largest amounts of zinc and smaller amounts of cadmium, and the remaining metals were collected in the following order: Cu> Ni> Pb. The results obtained show that the tested heavy metals could have an impact on the density and diversity of meso-and macrofauna. Probably soil fauna affected by other factors (soil moisture, organic matter content, type of humus) .

Postpyrogenic Polycyclic Soils in the Forests of Yakutia and Transbaikal region

Periodical forest fires are typical natural events under the environmental and climatic conditions of central and southern Yakutia and Transbaikal region of Russia. Strong surface fires activate exogenous geomorphological processes. As a result, soils with polycyclic profiles are developed in the trans-accumulative landscape positions. These soils are specified by the presence of two–three buried humus horizons with abundant charcoal under the modern humus horizon. This indicates that these soils have been subjected to two–three cycles of zonal pedogenesis during their development. The buried pyrogenic humus horizons accumulate are enriched in humus; nitrogen; total and oxalate-extractable iron; exchangeable bases (Са+2 and Mg+2); and the fractions of coarse silt, physical clay (<0.01 mm), and clay (<0.001 mm) particles in comparison with the neighboring mineral horizons of the soil profile. The humus of buried pyrogenic horizons is characterized by the increased content of humic acids, particularly, those bound with mobile sesquioxides (HA-1) and calcium (HA-2) and by certain changes in the type of humus.

Geochemical characteristics of light hydrocarbons and their influencing factors in natural gases of the Kuqa Depression, Tarim Basin, NW China

In order to determine the source of the light hydrocarbons in the Kuqa Depression of the Tarim Basin, Northwest China, their geochemical characteristics are documented, and possible influencing factors are discussed in a broad context on the basis of geochemical analyses of natural gas samples from 19 wells in combination with previously reported natural gas components and carbon isotope values from the same depression. The biomarker analytical results show that (a) methyl cyclohexane (37.5–60.3%) of natural gas predominates the C7 light hydrocarbon series (methyl cyclohexane, heptanes, and dimethyl cyclopentane), and (b) the heptane content (25.0–54.8%) is also relatively high. The C6–7 light hydrocarbon series (aromatics, normal alkanes, and cycloalkanes) have abnormally high aromatics (benzene and toluene) content (26.2–83.8%). Heptane value (13.31–37.77%) and isoheptane value (2.10–7.64%) indicate that the Kuqa natural gases are of high maturity and typical of coal‐derived gas (gas generated by sapropelic source rock). Their light hydrocarbons, however, appear to have some characteristics of mixed‐source organic matter. Specifically, the light hydrocarbons in the Dina 2 gas field show characteristics of the coal‐derived gas; those in the Dabei gas field show some features of the oil‐associated gas (gas generated by humic source rock), whereas those in the Kela 2 and Keshen 2 gas fields and Well Yangtake‐101 display characteristics of the mixed source organic matter. The abnormally high content of the aromatics in the Kuqa Depression may have resulted mainly from their high productivity during the thermal maturity of humic type organic matters and the gases accumulation of late stage. The different relative contents of the aromatics in various oil and gas fields may have been accounted by different organic matter types, maturity, and distribution patterns of source rocks.