Search

Radon (Rn) and helium (He) gases from uranium decay form distinct anomalies related to buried uranium deposits. In order to trace the geochemical anomalous sources from the volcanic-related uranium deposits in deeply buried areas, systematical Rn contents and He isotope ratios were analyzed from the Daguanchang uranium deposit. The soil gas Rn concentrations above the deep uranium are ten times higher than those in barren areas, indicating that instantaneous Rn content measurements can be used to detect deeply buried uranium. The helium isotope ratios (3He/4He) of the unmineralized samples from the mineralized drill hole (ZK1) are relatively lower and uniform compared to those of the samples from no-mineral drill hole (ZK2). However, the Th and U contents of the drill core samples from ZK1 are slightly lower than those of the samples from ZK2, indicating that the lower 3He/4He ratios in ZK1 are most likely due to the addition of 4He from underlying uranium intervals. The differences in the instantaneous Rn contents are consistent with the variations in the He isotope ratios of the drill core samples. These results demonstrate that soil gas Rn and 3He/4He ratios are useful tracers and can indicate the existence of deeply buried volcanic-related hydrothermal uranium ores. [ABSTRACT FROM AUTHOR]

Effective management of surface emissions from abandoned gob methane (AGM) is crucial for mitigating greenhouse gas emissions and ensuring public safety. An important geochemical characteristic of near-surface AGM migration is the potential presence of abnormal component concentrations in near-surface soil gas over abandoned coal gobs. To investigate this phenomenon, a surface geochemical survey was conducted based on four survey lines in the Dongyi and Dongsan abandoned gob groups in the Xinghua Coal Mine, Jixi Basin, in China. The gas chromatography technique was used to analyze the concentrations of methane, carbon dioxide, ethane, propane, and butane in the collected 43 soil gas samples. The results revealed a significant anomaly of soil gas concentrations, particularly methane and carbon dioxide anomalies, in the near-surface soil over abandoned gobs. The background concentration for methane was determined to be 7.49 ppm, with an anomalous threshold set at 10 ppm based on a statistical analysis and an iterative method. This threshold could be confirmed by examining the coupling and decoupling relationship between methane, carbon dioxide, and C2–3 as well. A spatial correlation between regions exhibiting anomalous methane and carbon dioxide concentrations and the positions of gob areas, abandoned surface wells, and faults was observed. Abandoned and sealed coalbed methane surface wells and faults near gas-rich gob areas have the potential to act as conduits for AGM leakage to the surface. Furthermore, concentrations of methane, carbon dioxide, and C2–3 in soil gas over abandoned coal gobs were significantly higher compared to areas unaffected by mining activities. This suggests that elevated concentrations of methane, carbon dioxide, and C2–3 in soil gas may originate from underground AGM. [ABSTRACT FROM AUTHOR]

Most marine gas hydrate systems follow a vertical pattern with hydrate overlying free gas. Here we document the discovery of a gas to hydrate system in a horizontal sand layer in the Qiongdongnan Basin of the South China Sea. Eight wells were drilled by the Guangzhou Marine Geological Survey in 2021–2022 to investigate the occurrence and mechanisms responsible for the formation of the system. We describe a free gas‐bearing sand reservoir at the center of the system sustained by advecting hot fluids and gas; away from the advecting zone, the cooler, surrounding sand reservoir is filled with hydrate. Observations at this site show that advective heat has a large control on hydrate formation in sands and may be a key mechanism which allows gas migration within the hydrate stability zone and the formation of high‐saturation hydrate in sand layers. Plain Language Summary: Natural gas hydrate, an ice‐like substance composed of water and gas, is commonly found in sediments under the ocean. Most marine hydrate systems follow a vertical pattern where hydrate‐bearing sediments overlie free gas‐bearing sediments; in addition, most hydrate is hosted in marine muds at low concentration. Here we document a horizontal system that transitions from high concentrations of free gas to high concentrations of hydrate in a horizontal sand layer in the northern South China Sea. Two recent drilling expeditions are conducted to explore this unique system. Seismic and logging data suggests that multiple processes including focused fluid flow, capillary sealing and heat transfer control the formation of the system. Key Points: We discover a gas hydrate system where gas transitions to hydrate in a flat‐lying sand layer in the northern South China SeaCapillary sealing occurs at the sand‐clay interface, preventing upward fluid advection and causes fluids to migrate laterallyAdvecting warm fluids and gas are the primary control on the hydrate and free gas system in this sand layer [ABSTRACT FROM AUTHOR]

Odor emission from the soil of pesticide-contaminated sites is a prominent environmental problem in China, but there are very few researches about the component and spatial distribution of odorous substances in the soil of contaminated sites. In this paper, to investigate the odor pollution condition of an organophosphorus pesticide production site in a city of South China, the odor pollutants in the soil and soil gas were analyzed and the key odor–contributing substances were identified. Besides, the correlation between the concentrations of odorous substances in soil and soil gas was analyzed, and the measured results were compared with the predicted results by the linear model and DED model. An off-line soil gas sampling device was designed to collect the gas emitted from soil because the groundwater level in the site was too shallow to build a soil gas well. The key odor substances were screened from the detection results of soil gas via odor activity value (OAV) analysis, which revealed that the key odorous substances included benzene, ethylbenzene, ammonia, toluene, m,p-xylene, methyl sulfide, dimethyl disulfide, and formaldehyde. Furthermore, the spatial distribution of the odor substances in the soil of the pesticide-contaminated site was closely related to the layout and geologic structure of the site. The odor pollutants in soil were mainly distributed near the phosmet production workshop and the drainage ditch network. As for the deep distribution, the odorous substances were mainly enriched in the silty clay or clay layer (5.6–11 m), followed by the sludge layer (1–3.6 m). Finally, the predicted model (linear model and DED model) analysis suggested that the linear model was more suitable for predicting the concentration of odorous substances in the soil gas with the detection data of soil in this pesticide-contaminated site. [ABSTRACT FROM AUTHOR]

Soil profile CO2 transport and production are vital in the carbon stock in desert artificial vegetation ecosystem. In this study, soil profile CO2 concentration, soil water content, and temperature at depths of 0–40 cm were measured at four revegetated sites (1956, 1964, 1981, and 1987), located in the southeastern edge of Tengger Desert, China. The gradient method was applied to simulate soil gas diffusion coefficient and soil profile CO2 efflux. Soil CO2 efflux and production were significantly higher in upper layers than in bottom layers. The soil profile CO2 concentration, CO2 efflux, and production were not significantly increased with revegetation age. The simulated soil surface CO2 efflux were 0.54, 0.49, 0.44, and 0.25 μmol·m−2·s−1 at 1956, 1964, 1981, and 1987 revegetated sites, respectively. The soil surface CO2 efflux mainly came from the 0–10 cm layers, contributing to 76.4–94.9% of the total. CO2 uptake occurred in the 10–35 cm soil layer. Structural equation modelling explained 97.0% of the variations in soil surface CO2 efflux. The effects of soil CO2 concentration, temperature, and water content in the 10-cm layer and plant properties on soil surface CO2 efflux were 0.977, 0.516, − 0.358, and − 0.156, respectively. Interaction between soil temperature and water content was significant and the value was 0.439, indicating that the soil temperature and water content significantly influenced soil CO2 efflux. These results indicated that revegetation would not significantly affect the soil surface CO2 efflux and provided some theoretical basis for the study of soil carbon cycle mechanism in desert artificial vegetation ecosystem. [ABSTRACT FROM AUTHOR]

Urumqi City, located in the northwest of China, is a city with a high indoor radon concentration in a nationwide indoor radon survey in China. This study focuses on the assessment of the indoor radon level and its distribution in this city. Indoor radon measurement using RAD7 and solid nuclear track detector (SSNTD), soil gas radon measured by RAD7, and the determination of the specific activity of uranium and radium in soil samples by a high pure germanium spectrometer were performed from 2021 to 2023. The results reveal a wide range of indoor radon concentrations in Urumqi, with anomalies above 400 Bq/m3 in some dwellings. The arithmetical and geometric mean values of indoor radon concentration are 80 ± 77 Bq/m3 and 58 Bq/m3, respectively. The geometric mean value of radon measured by SSNTD is 101 Bq/m3. The distribution of areas with a high indoor radon concentration is spatially consistent with deep and large active faults or overlapping and intersection zones of multiple groups of faults. It is recommended to conduct a more comprehensive investigation and research into the elevated radon potential and radioactivity associated with building materials. [ABSTRACT FROM AUTHOR]

BTEX (benzene, toluene, ethylbenzene, and xylene), as characteristic pollutants in chemical plant sites, are widely present in the environment and pose a serious threat to the health and safety of nearby residents. Studying the spatial distribution characteristics and transport fluxes of BTEX in soil and air at contaminated sites and the health risks they pose to humans is of great significance for fine pollution control and environmental management. This study took a typical decommissioned steel plant as a case study. A total of 23 soil and air samples were collected from different locations to investigate the spatial distribution characteristics of BTEX in soil and air. The transport and fate of BTEX in soil and air were evaluated using the fugacity model, and finally, a human health risk assessment was conducted. The results indicate a relatively severe level of benzene pollution in both soil and air. The maximum exceedance factor of benzene in soil samples is 31.5, with the concentration exceedance depth at 1.5 m. The maximum concentration of benzene in air samples is 4.98 μg·m−3. Benzene, at 5.9% of the site, shows a low flux with negative values, while other components at various locations all exhibit a trend of transport from the soil phase to the atmospheric phase. Benzene is the pollutant that contributes the most to the transport flux from soil to air within the site. The coking area and sewage treatment area are key areas within the steel mill where BTEX accumulate easily in the soil. The non-carcinogenic risk values of the individual components of BTEX in the soil are below the acceptable risk level. However, the carcinogenic risk value of benzene in the children's exposure scenario exceeds the carcinogenic risk level of 10−6. The carcinogenic risk range of various components of BTEX in the air is 2.63 × 10−6~3.88 × 10−5, with 28.6% of the locations exceeding the threshold of 10−6. The range of the total HI (hazard index) is 2.08 × 10−4~1.81 × 10−1, all of which is below the safety threshold of 1. The results of this study will provide scientific support for the fine pollution control and environmental management of industrial contaminated sites with BTEX as their typical pollutants. [ABSTRACT FROM AUTHOR]

In the search for precursors to earthquakes, correlation has been found between geochemical characteristics of soil gases and seismic activity. In this paper we present evidence that seismic waves can trigger emission of soil radon (Rn) and carbon dioxide (CO2). An active experiment was performed in two fault zones in China, the Annighe fault in Sichuan province and the Xiadian fault in Heibei province. An active seismic source was used to generate seismic waves at 10 m depth in wells within bedrock. Rn and CO2 detectors were placed around the wells at a distance of ∼1 m for observing the effects of the seismic waves on the emission of the gases. The observations confirm that the seismic waves have a significant and direct effect on the concentration and flux of soil radon and carbon dioxide. When the seismic events were triggered, the observed concentrations of Rn and CO2 immediately increased and reached peak values within 5–50 min and 30–60 min, with corresponding increases of Rn and CO2 concentrations by 10.5%–238.7% and 3.1%–54.1%, respectively. The measured concentrations and flux of CO2 and Rn after the passage of the seismic waves showed strong correlation, confirming the suggestion that CO2 is the carrier gas for Rn. To the best of our knowledge this is the first direct, in‐situ measurement of gas emission caused by the passage of seismic waves and provides important constraints for better understanding of geochemical earthquake precursors. Plain Language Summary: Observed geochemical properties of soil gases migrated from the deep Earth can be used to survey seismicity, volcanic activity and emission of greenhouse gases. However, due to difficulty in natural earthquake prediction, most observations on the geochemical effects linked to seismic activity are conducted after or away from naturally occurring events, with the effects normally inferred from seismic parameters. In this study, an active seismic source based on methane gaseous detonation was employed to artificially produce seismic events along two fault zones, and in‐situ measurements of concentrations and flux of radon (Rn) and carbon dioxide (CO2) were conducted. These observations showed strong correlation between concentrations and flux of CO2 and Rn after the events, in agreement with the hypothesis that CO2 is the carrier gas for Rn in tectonically active settings. Key Points: Soil CO2 and Rn emission triggered by a new type active source that excited at 10 m deep well in bedrock are observed at first timeQuantitative effect of seismicity on the concentration and flux of soil CO2 and Rn are presentedEmission of CO2 and Rn after the seismicity show strong correlation and proved that CO2 is the carrier gas for Rn [ABSTRACT FROM AUTHOR]

The knowledge of the spatial distribution, sources, and air–soil exchange of polycyclic aromatic compounds (PACs) in an oilfield area is essential to the development of effective control practices of PAC pollution. In this study, 48 passive air samples and 24 soil samples were collected during 2018–2019 in seven functional areas (e.g., urban, oil field, suburban, industrial, agricultural, near pump units, and background) in the Yellow River Delta (YRD) where the Shengli Oilfield is located, and 18 parent polycyclic aromatic hydrocarbons (PAHs) and five alkylated-PAHs (APAHs) were analyzed from all the air and soil samples. The ΣPAHs in the air and soil ranged from 2.26 to 135.83 ng/m3 and 33.96 to 408.94 ng/g, while the ΣAPAHs in the atmosphere and soil ranged from 0.04 to 16.31 ng/m3 and 6.39 to 211.86 ng/g, respectively. There was a downward trend of atmospheric ΣPAH concentrations with increasing the distance from the urban area, while both ΣPAH and ΣAPAH concentrations in the soil decreased with distance from the oilfield area. PMF analyses show that for atmospheric PACs, coal/biomass combustion was the main contributor in urban, suburban, and agricultural areas, while crude production and processing source contributes more in the industrial and oilfield area. For PACs in soil, densely populated areas (industrial, urban, and suburban) are more affected by traffic sources, while oilfield and near-pump unit areas are under the impact of oil spills. The fugacity fraction ( f f ) results indicated that the soil generally emitted low-molecular-weight PAHs and APAHs and act as a sink for high-molecular-weight PAHs. The incremental lifetime cancer risk (ILCR) of Σ(PAH+APAH) in both the air and soil, were below the threshold (≤10−6) set by the US EPA. [ABSTRACT FROM AUTHOR]

Asbestos has been confirmed as a major pollutant in asbestos-mining areas that are located in western China. In general, asbestos-fibre dust will is released into the environment due to the effect of intensive industrial activities and improper environmental management, such that the health of residents in and around mining areas is jeopardised. A typical asbestos mining area served as an example in this study to analyse the content and fibre morphology of asbestos in soil and air samples in the mining area. The effects of asbestos pollution in and around the mining areas on human health were also assessed based on the U.S. Superfund Risk Assessment Framework in this study. As indicated by the results, different degrees of asbestos pollutions were present in the soil and air, and they were mainly concentrated in the mining area, the ore-dressing area, and the waste pile. The concentration of asbestos in the soil ranged from 0.3% to 91.92%, and the concentration of asbestos fibres in the air reached 0.008–0.145 f·cc−1. The results of the scanning-electron microscope (SEM) energy suggested that the asbestos was primarily strip-shaped, short columnar, and granular, and the asbestos morphology of the soils with higher degrees of pollution exhibited irregular strip-shaped fibre agglomeration. The excess lifetime cancer risk (ELCR) associated with the asbestos fibres in the air of the mining area was at an acceptable level (10−4–10−6), and 40.6% of the monitoring sites were subjected to unacceptable non-carcinogenic risks (HQ > 1). Moreover, the waste pile was the area with the highest non-carcinogenic risk, followed by the ore dressing area, a residential area, and a bare-land area in descending order. In the three scenarios of adult offices or residences in the mining area, adults' outdoor activities in the peripheral residence areas, and children's outdoor activities, the carcinogenic-and non-carcinogenic-risk-control values in the air reached 0.1438, 0.2225 and 0.1540 f·cc−1, and 0.0084, 0.0090 and 0.0090 f·cc−1, respectively. The results of this study will lay a scientific basis for the environmental management and governance of asbestos polluted sites in China. [ABSTRACT FROM AUTHOR]

Deeply excavated expansive soil canal slopes can have instability risks during operations. The deformation mechanism is analyzed using internal and external factors, such as engineering geology, hydrogeology, rainfall, and groundwater levels in the middle expansive soil canal slope in the central line of the South-to-North Water Diversion Project, Taocha District, Nanyang City, Henan Province, China. The stability of the canal slope and the effect of the reinforcement and disposal measures are evaluated with a geological survey, manual inspection of the defects, safety monitoring data analysis, hidden danger geophysical detection, and stability numerical simulation. The following conclusions are drawn: (1) the surface-refilled cement-treated soil failed to isolate the water vapor exchange between the expansive soil and the atmosphere; and (2) the stagnant water in the upper layer is replenished by precipitation, leading to the increase in the groundwater level during the rainy season and the decrease in the groundwater level during the dry season. Shear creep deformation occurs along the fissure of the second to fourth grade canal slopes. The potential sliding surface consists of a gentle dip angle leading edge and a steep dip angle trailing edge. The arrangement of the antisliding piles on the water-passing section and the crack surface distribution had an effect, and the potential shear outlet is in the first grade berm, the deformed body is still developing, and the trailing edge is not apparent. The potential failure mode of the slope is deep sliding, and the current safety factor is 1.002. A combination of groundwater discharge and micropile reinforcement is required to improve the stability of the canal slope. After the drainage and reinforcement are implemented, the slope's deep antislide stability safety factor increases to 1.462, which met the safety requirements. The results could provide a reference for the operation management and reinforcement governance of similar projects. [ABSTRACT FROM AUTHOR]

The terrestrial water cycle links the soil and atmosphere moisture reservoirs through four fluxes: precipitation, evaporation, runoff, and atmospheric moisture convergence (net import of water vapor to balance runoff). Each of these processes is essential for sustaining human and ecosystem well‐being. Predicting how the water cycle responds to changes in vegetation cover remains a challenge. Recently, changes in plant transpiration across the Amazon basin were shown to be associated disproportionately with changes in rainfall, suggesting that even small declines in transpiration (e.g., from deforestation) would lead to much larger declines in rainfall. Here, constraining these findings by the law of mass conservation, we show that in a sufficiently wet atmosphere, forest transpiration can control atmospheric moisture convergence such that increased transpiration enhances atmospheric moisture import and results in water yield. Conversely, in a sufficiently dry atmosphere increased transpiration reduces atmospheric moisture convergence and water yield. This previously unrecognized dichotomy can explain the otherwise mixed observations of how water yield responds to re‐greening, as we illustrate with examples from China's Loess Plateau. Our analysis indicates that any additional precipitation recycling due to additional vegetation increases precipitation but decreases local water yield and steady‐state runoff. Therefore, in the drier regions/periods and early stages of ecological restoration, the role of vegetation can be confined to precipitation recycling, while once a wetter stage is achieved, additional vegetation enhances atmospheric moisture convergence and water yield. Recent analyses indicate that the latter regime dominates the global response of the terrestrial water cycle to re‐greening. Evaluating the transition between regimes, and recognizing the potential of vegetation for enhancing moisture convergence, are crucial for characterizing the consequences of deforestation as well as for motivating and guiding ecological restoration. [ABSTRACT FROM AUTHOR]

Iron ore tailing is a major solid waste requiring advanced recycling methods because ore tailing powder is polluting air and water resources. For instance, about 300 million tons of tailings are disposed yearly in 1229 iron ore tailings dams in the Hebei province in China. Iron ore tailings can be recycled as functional materials because these tailings are similar to natural silicate minerals. Here, we review the conversion iron ore tailings into functional materials by different technologies. Functional materials include magnetic nanoparticles made of zero-valent iron or iron oxide, and nanoporous materials such as silica or zeolite. We present applications to the removal of water, air and soil contaminants, by physical, chemical and biological methods. Overall, iron ore tailings-based materials show excellent performances for water treatment, air purification and soil remediation. [ABSTRACT FROM AUTHOR]

As the west rim of an ejective fold zone, the Huaying Mountain fault zone (HMFZ) in the eastern Sichuan Basin (SB) plays an important role in the tectonic evolution of the SB. The distribution and characteristics of HMFZ are strongly associated with tectonic activities and have greatly impacted the distribution of oil and gas reservoirs. However, its distribution and characteristics have remained poorly understood due to a lack of geophysical data, especially areal gravity survey and magnetotellurics (MT) survey, which are admittedly advantageous for detecting the edges of geological structures. Therefore, we carried out the ground geophysical surveys that areal gravity survey and MT survey, and acquired 1:250,000-scale real gravity data and MT data for the first time in this area. Optimized edge-detection methods were adopted to process the areal gravity data, allowing us to characterize the planar distribution of faults more reliably and convincingly. We found that the southern HMFZ is well developed and primarily trends in NNE and NE, whereas the subordinate faults trend in N-S and W-E. Vertical information for the faults extracted using the improved depth from the extreme points method revealed that the fault dominantly dipped to the SE, which was consistent with the results of MT inversion. Based on the spatial distribution of the faults, we further discussed the gravity anomaly, fault distribution, Luzhou palaeo uplift, and the distribution and characteristics of oil-gas resources, and found the convincing evidence to analysis the distribution of oil and gas resources in this region. [ABSTRACT FROM AUTHOR]

The burning of fossil fuels by humans emits large amounts of CO2 into the atmosphere and strongly affects the Earth's carbon balance, with grassland ecosystems changing from weak carbon sinks that were previously close to equilibrium to core carbon sinks. Chinese grasslands are located in typical arid–semi-arid and semi-arid climatic regions, and drought events in the soil and atmosphere can have strong and irreversible consequences on the function and structure of Chinese grassland ecosystems. Based on this, we investigated the response of the gross primary production (GPP) of Chinese grasslands to land–atmosphere moisture constraints, using GPP data simulated through four terrestrial ecosystem models and introduced copula functions and Bayesian equations. The main results were as follows: (1) Soil moisture trends were not significant, and changes were dominated by interannual variability. The detrended warm-season SM correlated with GPP at 0.48 and 0.63 for the historical and future periods, respectively; thus, soil moisture is the critical water stress that regulates interannual variability in Chinese grassland GPP. (2) The positive correlation between shallow SM (0–50 cm) and GPP was higher (r = 0.62). Shallow-soil moisture is the main soil layer that constrains GPP, and the soil moisture decrease in shallow layers is much more likely to cause GPP decline in Chinese grasslands than that in deep-soil water. (3) The probability of GPP decline in Chinese grasslands caused by drought in shallow soils of 0–20 and 20–50 cm is 32.49% and 27.64%, respectively, which is much higher than the probability of GPP decline in deeper soils. In particular, soil drought was more detrimental to grassland GPP in Xinjiang and the Loess Plateau. (4) The probability of soil drought causing GPP decline was higher than that of atmospheric drought during the historical period (1.78–8.19%), but the probability of an atmospheric drought-induced GPP deficit increases significantly in the future and becomes a key factor inhibiting GPP accumulation in some regions (e.g., the Loess Plateau). Our study highlighted the response of grassland ecosystems after the occurrence of soil drought, especially for the shallow-soil-water indicator, which provides important theoretical references for grassland drought disaster emergency prevention and policy formulation. [ABSTRACT FROM AUTHOR]

Investigating the emissions of soil gas including radon, mercury and carbon dioxide (222Rn, Hg and CO2) from the solid earth to the atmosphere through active fault zones is of great significance for accession of atmospheric environment. In this study, the concentrations and fluxes of 222Rn, Hg and CO2 were measured at the main active fault zones at the western margin of the Ordos block, China. The concentrations of 222Rn, Hg and CO2 were in the range of 0–60.1 kBq m−3, 3–81 ng m−3 and 0.04–9.23%, respectively, while the fluxes of 222Rn, Hg and CO2 are in the range of 1.99–306.99 mBq m−2 s−1, 0–15.12 ng m−2 h−1 and 0–37.91 g m−2d−1, respectively. Most of the major fault zones at the study area are CO2 risk-free regions (CO2 concentration in soil gas < 5%). However, the extend of 222Rn pollution at the fault zones of F1, F4, F5 and F9 (the fault number) and that of Hg pollution at the fault zones of F2, F4, F5 and F7 were higher than the pollution level of 1. The annual emission of Hg and CO2 from the western margin of the Ordos block was estimated to be 2.03 kg and 0.70 Mt, respectively. Comprehensive analyses indicated that the higher emission rates of soil gases from the active fault zones were related to the seismic activities. The results suggest that the earthquake activity is a dominant factor enhancing the emission of 222Rn, Hg and CO2 from the solid earth through active fault zones and, furthermore, resulting great impact on the atmospheric environment. [ABSTRACT FROM AUTHOR]

Introduction: Plant species composition in forest ecosystems can alter soil greenhouse gas (GHG) budgets by affecting soil properties and microbial communities. However, little attention has been paid to the forest types characterized by understory vegetation, especially in boreal forests where understory species contribute significantly to carbon and nitrogen cycling. Method: In the present study, soil GHG fluxes, soil properties and bacterial community, and soil environmental conditions were investigated among three types of larch forest [Rhododendron simsii-Larix gmelinii forest (RL), Ledum palustre-Larix gmelinii forest (LL), and Sphagnum-Bryum-Ledum palustre-Larix gmelinii forest (SLL)] in the typical boreal region of northeast China to explore whether the forest types characterized by different understory species can affect soil GHG fluxes. Results: The results showed that differences in understory species significantly affected soil GHG fluxes, properties, and bacterial composition among types of larch forest. Soil CO2 and N2O fluxes were significantly higher in LL (347.12 mg m-2 h-1 and 20.71 µg m-2 h-1) and RL (335.54 mg m-2 h-1 and 20.73 µg m-2 h-1) than that in SLL (295.58 mg m-2 h-1 and 17.65 µg m-2 h-1), while lower soil CH4 uptake (-21.07 µg m-2 h-1) were found in SLL than in RL (-35.21 µg m-2 h-1) and LL (-35.85 µg m-2 h-1). No significant differences between LL and RL were found in soil CO2, CH4, and N2O fluxes. Soil bacterial composition was mainly dominated by Proteobacteria, Actinobacteria, Acidobacteria, and Chloroflexi among the three types of larch forest, while their abundances differed significantly. Soil environmental variables, soil properties, bacterial composition, and their interactions significantly affected the variations in GHG fluxes with understory species. Specifically, structural equation modeling suggested that soil bacterial composition and temperature had direct close links with variations in soil GHG fluxes among types of larch forest. Moreover, soil NO3 --N and NH4 + - N content also affected soil CO2, CH4, and N2O fluxes indirectly, via their effects on soil bacterial composition. Discussion: Our study highlights the importance of understory species in regulating soil GHG fluxes in boreal forests, which furthers our understanding of the role of boreal forests in sustainable development and climate change mitigation. [ABSTRACT FROM AUTHOR]

The decline in soil nutrients is becoming a major concern of soil degradation. The possibility of using organic waste as a soil additive to increase nutrients and essential components is significant in soil quality protection and waste management. The aim of this study was to investigate the effects of composted spent mushroom substrate (MS), giant panda feces (PF), and cattle manure (CM) as organic fertilizers in soil microbial communities and metabolites in blueberry orchard in China, which were measured by using high-throughput sequencing and gas chromatography-mass spectrometry (GC-MS)-based metabolomics. Altogether, 45.66% of the bacterial operational taxonomic units (OTUs) and 9.08% of the fungal OTUs were detected in all treatments. Principal coordinates analysis demonstrated that the bacterial and fungal communities in MS and PF treatments were similar, whereas the communities in the not-organic fertilized control (CK) were significantly different from those in the organic fertilizer treatments. Proteobacteria, Acidobacteria, and Bacteroidetes were the dominant bacterial phyla, and Basidiomycota, Ascomycota, and Mortierellomycota the dominant fungal phyla. Redundancy analysis indicated that pH and available potassium were the main factors determining the composition of microbial communities. The fungal genera Postia, Cephalotrichum, and Thermomyces increased in organic fertilizer treatments, and likely promoted the degradation of organic fertilizers into low molecular-weight metabolites (e.g., amino acids). PCA and PLS-DA models showed that the metabolites in CK were different from those in the other three treatments, and those in CM were clearly different from those in MS and PF. Co-occurrence network analysis showed that several taxa correlated positively with amino acid contents. The results of this study provide new insights into organic waste reutilization and new directions for further studies. [ABSTRACT FROM AUTHOR]

An increasing number of studies have demonstrated that natural source zone depletion (NSZD) in the vadose zone accounts for the majority (90%~99%) of the natural attenuation of light non-aqueous phase liquid (LNAPL). Until now, 0.05 to 12 kg/a.m2 NSZD rates at tens of petroleum LNAPL source zones have been determined in the middle or late evolution stage of LNAPL release, in which limited volatile organic compounds (VOCs) and methane (CH4) were detected. NSZD rates are normally estimated by the gradient method, yet the associated functional microbial activity remains poorly investigated. Herein, the NSZD at an LNAPL-releasing site was studied using both soil gas gradient methods quantifying the O2, CO2, CH4, and VOCs concentrations and molecular biology methods quantifying the abundance of the pmoA and mcrA genes. The results showed that the methanogenesis rates were around 4 to 40 kg/a.m2. The values were greater than the rates calculated by the sum of CH4 escaping (0.3~1.2 kg/a.m2) and O2 consuming (3~13 kg/a.m2) or CO2 generating rates (2~4 kg/a.m2), suggesting that the generated CH4 was oxidized but not thoroughly to CO2. The functional gene quantification also supported the indication of this process. Therefore, the NSZD rates at the site roughly equaled the methanogenesis rates (4~40 kg/a.m2), which were greater than most of the previously studied sites with a 90th percentile value of 4 kg/a.m2. The study extended the current knowledge of the NSZD and has significant implications for LNAPL remediation management. [ABSTRACT FROM AUTHOR]

Microbial communities play critical roles in fixing carbon from the atmosphere and fixing it in the soils. However, the large‐scale variations and drivers of these microbial communities remain poorly understood. Here, we conducted a large‐scale survey across China and found that soil autotrophic organisms are critical for explaining CO2 fluxes from the atmosphere to soils. In particular, we showed that large‐scale variations in CO2 fixation rates are highly correlated to those in autotrophic bacteria and phototrophic protists. Paddy soils, supporting a larger proportion of obligate bacterial and protist autotrophs, display four‐fold of CO2 fixation rates over upland and forest soils. Precipitation and pH, together with key ecological clusters of autotrophic microbes, also played important roles in controlling CO2 fixation. Our work provides a novel quantification on the contribution of terrestrial autotrophic microbes to soil CO2 fixation processes at a large scale, with implications for global carbon regulation under climate change. [ABSTRACT FROM AUTHOR]

Knowledge of the difference between soil and air temperatures (ΔT) is helpful to improve our understanding on the land‐atmosphere thermal interactions and temperature‐dependent soil processes. Based on 272 stations across China, this study investigated the spatiotemporal variations of the annual and seasonal ΔT (difference between soil temperature at a depth of 0.4 m and air temperature) from 1981 to 2014, and quantified the relative contributions of multiple environmental variables (snow cover, precipitation, vegetation, soil moisture, and solar radiation) to ΔT variation for the first time. Air temperature primarily controls soil temperature dynamics, but the asynchronous trends of soil and air temperatures may lead to the complexity of the land‐atmosphere relationship. Almost no apparent trends in ΔT were detected for the entire China (except in summer), but the spatial heterogeneity of trends was evident. Snow cover conditions greatly dominated the ΔT dynamics both annually and seasonally (except in summer). The relative contribution of snow cover duration to ΔT variation was significantly greater than that of mean snow depth for the entire China, but the regional differences in the contributions of the two variables were noticeable at different seasons. The greening of vegetation closely associated with the ΔT variation in annual, autumn and winter, and soil moisture exerted a great influence on summer ΔT, associated with sunshine duration (a proxy for surface solar radiation). The amount of precipitation made a slight impact on ΔT at either seasonal or annual scales. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of Soil & Water Conservation is the property of Bulletin of Soil & Water Conservation Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Alterations in plant litter inputs into the soil are expected to significantly affect soil greenhouse gas (GHG) emissions. However, the influence on boreal forest soils is not clear, given the large amount of accumulated soil organic matter that may buffer the impacts from the input of fresh litter. In this study, we conducted a litter manipulation experiment to explore the effects of the litter layer on soil GHG fluxes in a Dahurian larch (Larix gmelinii) forest ecosystem in northeastern China. Three litter treatments were implemented, namely aboveground litter removal (LR), litter double (LD), and unchanged litter input (CK). The associated microclimate, litter characteristics, and soil properties were also measured. The results showed that this larch forest soil acts as a source of CO2 and N2O but acts as a sink for CH4 for all litter manipulation treatments. LD increased the soil CO2 and N2O fluxes by 15% and 34%, while LR decreased them by 8% and 21%, respectively. However, soil CH4 uptake decreased by 34% in LD treatment and increased by 22% in LR treatment, respectively. Litter manipulation treatments can not only affect soil GHG fluxes directly but also, via their effects on soil MBC, NH4+−N, and NO3−−N content, indirectly affect variations in soil CO2, CH4 and N2O fluxes, respectively. Our study highlights the importance of the plant litter layer in regulating soil GHG between the atmosphere and soil in a Dahurian larch forest ecosystem, especially for litter addition. Considering the natural increase in litter quantity over time, this important regulatory function is essential for an accurate estimation of the role of boreal forests in mitigating future climate change. [ABSTRACT FROM AUTHOR]

Intensive irrigation coupled with excessive nitrogen (N) fertilizer input has resulted in high soil greenhouse gas (GHG) emissions in vegetable cropping systems. Biochar as a soil amendment has been advocated as a desirable option to reduce GHG emissions in agricultural systems, but its interactive effects with soil N availability in vegetable systems have yet to be clarified. We performed a field study to examine how biochar interacts with N fertilizer in driving annual methane (CH4) and nitrous oxide (N2O) emissions from an intensively-irrigated greenhouse vegetable cropping system acting as both sources of atmospheric CH4 and N2O in subtropical China. Biochar amendment significantly increased soil CH4 emissions by 33% and 85%, while it decreased soil N2O emissions by 22% and 12% with and without N fertilizer input, respectively. Fertilizer N combination weakened the positive response of CH4 to biochar while it enhanced the mitigation potential of biochar for N2O. Annual direct emission factors of fertilizer N for N2O were estimated to be 1.35% and 1.94% for the fields with and without biochar amendment, respectively. Annual flux-sustained global warming potential (SGWP) and greenhouse gas intensity (GHGI) were significantly decreased by biochar amendment, and this mitigation effect was enhanced with fertilizer N combination. Altogether, we highlight that biochar can reconcile higher yield and lower climatic impact in intensive vegetable cropping systems in subtropical China, particularly in vegetable soils with high N availability. [ABSTRACT FROM AUTHOR]

In recent years, the exploration of concealed deposits has become extremely urgent as the shortage of surface resources worsens. In this study, naturally formed nanoparticles in five media (deep-seated fault gouge, ascending gas flow, soil, shallow groundwater and deep groundwater) in Chaihulanzi Au deposit, China, were analyzed by transmission electron microscopy. The characteristics of category, shape, lattice parameters, chemical component and association were obtained. The results show that deep media can carry natural nanoparticles to the surface media, resulting in an increased proportion of O and metal chemical valence such as Pb and Cu in nanoparticles. The metal elements Au, Ag, Cu, Zn and As in nanoparticles correspond to those of orebody minerals. Au-Ag-Cu, Fe-As, Cu-Sn and Pb-Zn element associations in nanoparticles are similar to those of mineral composition or orebody paragenesis in Chaihulanzi deposit. Compared with nanoparticle characteristics in deposit and background areas, it can be deduced that natural ore-bearing nanoparticles come from concealed orebodies. With the characteristics of more oxide forms and the dislocation of the crystal lattice, these nanoparticles are formed by faulting and oxidation. Nanoparticles produced in concealed orebodies that migrate from the deep to the surface media could be used for prospecting. [ABSTRACT FROM AUTHOR]

An analytical method of accelerated solvent extraction combined with gas chromatographic – microelectron capture detection (GC-μECD) was developed for the determination of energetic compounds (ECs) in soils from Chinese ammunition-contaminated sites. The results showed that the recoveries of most compounds were 82.86 ± 7.35 − 109.70 ± 10.82%, 82.53 ± 6.18 − 99.21 ± 1.88%, 80.44 ± 1.73 − 108.20 ± 4.58% at spiked levels of 20, 100, and 500 ng, respectively. Each spiked level was analyzed in triplicate with relative standard deviations from 3.51 to 13.34%, 1.90 to 10.51%, and 0.50 to 5.90%. GC-μECD is highly sensitive to these electronegative compounds with method detection limits (MDL) from 0.64 to 3.48 ng·g−1. This technique has the advantages of high efficiency, reduced solvent consumption, low detection limits, and suitability for a wide range of compounds. The developed approach was successfully applied to the determination of energetic compounds in soils collected from four ammunition-contaminated sites in China. The concentrations of energetic compounds in soil were from 5.60 to 9.22 × 105 ng·g−1 at these sites. The results show that the present method accurately simultaneously determined multiple energetic compounds that may assist with the characterization of soil pollution. [ABSTRACT FROM AUTHOR]

Copyright of World Nuclear Geoscience is the property of World Nuclear Geoscience Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The characteristics of airborne bacteria and fungi in different types of buildings are still unclear. This article applied the culturing and next-generation sequencing methods to characterize the airborne bacteria and fungi in five types of buildings during winter in Kunming, China. Results showed that the mean concentrations of fungi in different buildings were similar (approx. 387 ± 388 CFU/m3). The highest culturable bacterial concentration was found in residences, while the lowest was in the library. Lowering relative humidity, PM2.5 concentration and occupant density can reduce the bacterial concentrations. The major bacterial size in residences and in a hospital was 1.1–2.1 μm, while in other buildings was 2.1–3.3 μm. The PM2.5 concentration and occupant activities are key factors that could affect the microorganism size distributions. The community structures of the bacteria in the library and fungi in the hospital showed distinctive differences from the results in other buildings. The community structure of outdoor microorganisms showed great differences between soil and air samples. This study is helpful to give practical implications for assessing microbial characteristics in different types of buildings and provide valuable data for the formulation of indoor bioaerosol standards in China. [ABSTRACT FROM AUTHOR]

Radon is a naturally emitted gas that is observed in soils, subsoils, air, and all types of water. Because there is a statistically significant association observed between seismic activity and active concentration levels of radon readings, a dissolved form of radon in water near-fault locations such as wells or springs, has significant observational value. Furthermore, as the temperature of the water rises, the dissolved radon in the water might transfer to the air, a process known as degassing. Thus, radon measurements in all types of water such as groundwater, tap waters, and bottled drinking waters have been investigated by covering several aspects of the degassing process, namely, health issues, monitoring volcanic activities, and predicting seismic activities by employing various methods. In this paper, radon measurements of sampled waters removed from the well located at Yishui Seismic Station in China are utilized to monitor the degassing temperature and predict earthquakes. For this purpose, an experiment is devised to collect water samples manually. Then, the amount of radon dissolved in the water samples is examined to find a stable degassing temperature range at Yishui Seismic Station. An experimental setup is constructed to collect data for 20 days. The most important findings found regarding this research can be expressed as follows. (1) When the degassing temperature is observed to be higher than 5°C, the influence on radon value changes greatly. (2) The observations of the radon degassing temperatures in the Yishui well are found to be stable between 18°C and 23°C. [ABSTRACT FROM AUTHOR]

Amendment application is one of the effective measures used to remediate structural problems in coarse‐textured soils. However, the application of water‐based spent drilling mud (WBSM) as a potential amendment and its associated impacts on physical and hydraulic soil properties is not well‐studied. This research aimed to investigate the effect of the application of WBSM on basic hydrophysical properties of coarse‐textured loessial soil sampled from the Loess Plateau, China. Application of WBSM to repacked loessial soil at four application rates (0, 25.0, 50.0, 75.0 g kg−1, dry basis), denoted as control (H0), low (HDL), medium (HDM) and high (HDH), respectively, was used to investigate changes in soil bulk density (ρb), soil total porosity (ƒ), saturated hydraulic conductivity (Ks), relative gas diffusivity (Dp/Do), soil‐water retention and soil evaporation characteristics. The results showed that the soil ρb in HDL and HDM decreased by 4.0% and 5.5%, respectively, as compared to H0 (p < 0.05). Measured Ks changed to 36.7% (HWL), 12.2% (HWM) and 4.4% (HWH) as compared to H0 (5.56 cm d−1). The application of WBSM further decreased the percentage of soil pore sizes >30 μm, but increased the proportion of medium pore sizes (≥30–50 μm), micro pore sizes (≥0.3–5 μm) and extremely micro pore sizes (<0.3 μm), which was attributed to the clogging effect of the fine and clay particles contained in WBSM. Decline in Dp/Do, however, was observed with increasing WBSM, likely due to the increased pore tortuosity in fine‐grained soil. The van Genuchten soil‐water retention model parameters differed largely across the WBSM application rates, with increased soil available water‐holding capacity by 50.9%, 65.9% and 64.1% in HDL, HDM and HWH, respectively, as compared to H0. However, WBSM application also increased soil available water‐holding capacity and reduced evaporative water loss, which has useful implications for the management of coarse‐textured soils with a distinct water deficit in fragile ecosystems. Widespread use of WBSM to amend coarse‐textured soils requires further studies to evaluate the effects of WBSM amendments in field trials and its environmental consequences. Highlights: Water‐based spent drilling mud (WBSM) altered the texture of loessial soil.WBSM increased soil total porosity and changed pore size distribution.WBSM affected the characteristics of soil water and gas transport.The soil water availability was improved by WBSM application. [ABSTRACT FROM AUTHOR]

Greenhouse gases are ever increasing at the great risk of climate change in recent years. Climate change adaptation has been the most fundamental measure to achieve carbon neutrality. It is a high demand to reduce the agricultural carbon and nitrogen emission for water use efficiency during irrigation. In this study, a systematic investigation was made to clarify the effects of tillage systems on greenhouse gas emission and water use efficiency in farmland fields using the winter wheat-summer maize rotation system. The farmland experimental site was selected in the plot of the ninth production team of Zhoujiazhuang Town, Jinzhou City, Hebei Province of China. The test area was about 30 000 m² with a width and length of 91, and 330 m, respectively. A total of 54 plots were then divided into the experimental area, each with a randomly arranged area of 120 m² (8 m×15 m). The field experiment was performed on the different tillage and irrigation systems during the winter wheat-summer corn growing season from 2017 to 2018. The influencing factors were also determined, including the irrigation quantity, fertilizer application rate, and tillage mode. Among them, the conventional irrigation and fertilizer application were set as the control group in this case. The rotary and deep tillage modes were set at the same time. A total of 18 experimental treatments were carried out, each of which was arranged in the three experimental plots for repeat. Some parameters were measured, including the soil gas emission flux, crop water use efficiency, and crop yield. The test results show that: 1) There was a very significant level in the single factor effects of irrigation amount and fertilizer application rate on the yield and water use efficiency, as well as the effect of tillage mode on the yield, except for water use efficiency. There was no significant interaction between the three factors. Since the irrigation amount in a certain range increased the yield of the winter wheat, too much irrigation amount led to a significant decrease in the grain yield. The water use efficiency was higher than before when the irrigation amount was in the middle and low level. 2) There was the highest flux of N2O emission in summer during the growing period of winter wheat, while the lowest in spring and winter. Specifically, the N2O emission flux of soil showed several peaks, most of which occurred after irrigation during the growing period of summer corn. There was a positive correlation between the soil CO2 emission flux and soil surface temperature during the growing period of winter wheat. The peak of soil CO2 emission flux during the growing period of summer maize was concentrated in the stages from the seedling emergence to the jointing and from the tasseling to the silking. 3) There was a significant level in the interaction effects of irrigation water, fertilizer application, and tillage modes on the CO2-eq emission fluxes of winter wheat and summer maize. The mean N2O and CO2 emission fluxes were 261.57 mg/m² and 7 885.52 kg/hm², respectively, under the rotary tillage. In the deep tillage, the mean values of N2O and CO2 emission fluxes were 331.91 mg/m² and 9 313.69 kg/hm², respectively. The cumulative emission fluxes of N2O and CO2 under rotary tillage were 21.19% and 15.33% lower than those under deep tillage. 4) The low to medium level of irrigation and fertilizer application under the rotational tillage greatly contributed to the improved water utilization and crop yield, while reduced CO2-eq emissions. The CO2-eq emissions decreased by 3.4%, whereas, the water utilization increased by 8.16% under the low water and medium fertilizer rototill conditions. The CO2-eq emissions decreased by 1.9%, whereas, the water utilization increased by 19.9% under the medium water and low fertilizer rototill conditions. The CO2-eq emissions decreased by 13.8%, whereas, the water use efficiency increased by 12.24% under the low water and low fertilizer rototill conditions. The findings can provide a strong reference for the water saving and emission reduction of winter wheat and summer corn. [ABSTRACT FROM AUTHOR]

To monitor the natural radiation level in a River region in Southern China, an investigation was conducted into the terrestrial γ dose rate and soil Rn concentration. The in-situ survey took place at 541 points, using portable γ dose rate scintillators and radon detectors. The mean γ dose rate and the soil Rn concentration have been determined to be 100 ± 40 nGy h−1 and 4000 ± 3000 Bq m−3, respectively. The high radiation spots were observed at the eastern edge and the southwest corner of the study region, which could be attributed to the granite rocks that dominated the areas. [ABSTRACT FROM AUTHOR]

Soil radon anomaly is a common phenomenon in karst areas. In this paper, the geochemical behavior of radium (Ra) in the process of carbonate rock weathering and soil formation was used to reveal the accumulation mechanism of soil radon. In the karst area and non-karst area, 24 soil points were collected to measure radon and radium, and a carbonate weathering profile was collected in the karst area. The research showed that: (1) the theoretical radon value obtained from Ra is far greater than the radon value measured on site, indicating that soil Ra can provide a potential source for the source of soil Rn; (2) through the study of the geochemical behavior of Ra during the weathering process, it was found that Ra was significantly enriched during carbonate weathering. This paper deepened the understanding of the geochemical behavior of radionuclides (Ra, Rn) in karst environments. [ABSTRACT FROM AUTHOR]

The Pan-Eurasian Experiment (PEEX) Science Plan, released in 2015, addressed a need for a holistic system understanding and outlined the most urgent research needs for the rapidly changing Arctic-boreal region. Air quality in China, together with the long-range transport of atmospheric pollutants, was also indicated as one of the most crucial topics of the research agenda. These two geographical regions, the northern Eurasian Arctic-boreal region and China, especially the megacities in China, were identified as a "PEEX region". It is also important to recognize that the PEEX geographical region is an area where science-based policy actions would have significant impacts on the global climate. This paper summarizes results obtained during the last 5 years in the northern Eurasian region, together with recent observations of the air quality in the urban environments in China, in the context of the PEEX programme. The main regions of interest are the Russian Arctic, northern Eurasian boreal forests (Siberia) and peatlands, and the megacities in China. We frame our analysis against research themes introduced in the PEEX Science Plan in 2015. We summarize recent progress towards an enhanced holistic understanding of the land–atmosphere–ocean systems feedbacks. We conclude that although the scientific knowledge in these regions has increased, the new results are in many cases insufficient, and there are still gaps in our understanding of large-scale climate–Earth surface interactions and feedbacks. This arises from limitations in research infrastructures, especially the lack of coordinated, continuous and comprehensive in situ observations of the study region as well as integrative data analyses, hindering a comprehensive system analysis. The fast-changing environment and ecosystem changes driven by climate change, socio-economic activities like the China Silk Road Initiative, and the global trends like urbanization further complicate such analyses. We recognize new topics with an increasing importance in the near future, especially "the enhancing biological sequestration capacity of greenhouse gases into forests and soils to mitigate climate change" and the "socio-economic development to tackle air quality issues". [ABSTRACT FROM AUTHOR]

Surface litter layer strongly influences CO2, N2O, and CH4 fluxes (FCO2, FN2O, and FCH4) between the atmosphere and forest floor through litter decomposition (litter-internal, fL-L) or interactions between litter and mineral soil (litter-induced, fL-S). However, the relative contribution of fL-L or fL-S to these greenhouse gas (GHG) fluxes in forests at different succession stages remain unclear. We conducted a field experiment where surface litter was either removed (LR), left intact (CT), doubled (LD), or exchanged (LE) in a Masson pine forest (PF, early stage of succession) and an evergreen broadleaved forest (BF, climax of succession) at the Dinghushan Nature Reserve in southern China, and studied the responses of FCO2, FN2O, and FCH4 from August 2012 to July 2013. The results showed that both FCO2 and FN2O were increased by LD treatment with a greater increase in BF (41% for FCO2 and 30% for FN2O) and decreased by LR treatment with the greater decrease in PF (−61% for FCO2 and −58% for FN2O). LD treatment decreased FCH4 by 14% in PF and 6% in BF, and LR treatment increased FCH4 by 5% in PF and 18% in BF. fL-S contributed more to FCO2 (36%) and FN2O (45%) than fL-L in PF, whereas contributions of fL-L to FCO2 (41%) and FN2O (30%) were much bigger than fL-S in BF. The greater FCH4 in PF and BF resulted from the contributions of fL-L (−14%) and fL-S (−12%), respectively. Our results indicated that fL-L is the major source of GHG fluxes in BF, whereas fL-S dominates GHG fluxes in PF. The results provide a scientific reference for quantifying the contributions of fL-L and fL-S to GHG fluxes during the subtropical forest succession and should be considered in ecosystem models to predict global warming in the future. [ABSTRACT FROM AUTHOR]

As a land–atmosphere coupling "hot spot", the northern China climate transition zone has a sharp spatial gradient of hydrothermal conditions, which plays an essential role in shaping the spatial and temporal pattern of evapotranspiration-precipitation coupling, but whose mechanisms still remain unclear. This study analyzes the spatial and temporal variation in land–atmosphere coupling strength (CS) in the climate transitional zone of northern China and its relationship with soil moisture and air temperature. Results show that CS gradually transitions from strong positive in the northwest to negative in the southeast and northeast corners. The spatial distribution of CS is closely related to climatic hydrothermal conditions, where soil moisture plays a more dominant role: CS increases first, and then decreases with increasing soil moisture, with the threshold of soil moisture at 0.2; CS gradually transitions from positive to negative at soil moisture between 0.25 and 0.35; CS shows an exponential decreasing trend with increasing temperature. In terms of temporal variation, CS is strongest in spring and weakens sequentially in summer, autumn, and winter, and has significant interdecadal fluctuations. The trend in CS shifts gradually from significantly negative in the west to a non-significant positive in the east. Soil moisture variability dominates the intra-annual variability of CS in the study regions, and determines the interannual variation of CS in arid and semi-arid areas. Moreover, the main reason for the positive and negative spatial differences in CS in the study area is the different driving regime of evapotranspiration (ET). ET is energy-limited in the southern part of the study area, leading to a positive correlation between ET and lifting condensation level (LCL), while in most of the northern part, ET is water-limited and is negatively correlated with LCL; LCL has a negative correlation with P across the study area, thus leading to a negative ET-P coupling in the south and a positive coupling in the north. [ABSTRACT FROM AUTHOR]

The flux calculation schemes (FCSs) and gas sampling schemes (GSSs) determine the accuracy and representativeness of non‐steady‐state chamber measurements. The study aimed to provide guidelines on FCSs and GSSs to improve cumulative flux estimations of the non‐steady‐state chamber method. Based on a dataset obtained from automated chamber measurements in a permafrost‐affected wetland in northeast China, we evaluated the effects of FCSs and GSSs on cumulative methane and nitrous oxide flux estimates at the field scale. The evolution of chamber headspace gas concentrations was classified into five patterns, presenting the measurement disturbance and variation of non‐steady‐state chamber method. Three FCSs, that is, the sole use of linear model and hybrid use of linear with empirical quadratic and theoretical exponential models, were established on the basis of evolution patterns of chamber headspace gas concentrations. The hybrid FCSs were more robust for cumulative flux estimates than the sole FCS of the linear model. The flux dataset with the high spatiotemporal resolution was subsampled to simulate datasets obtained with different GSSs. The subsampling of flux dataset proved optimization of GSSs by allocating limited measurement resources to preferentially promote the spatial representativeness of measurements (e.g., with more replicate chambers and stratified chamber placement according to microtopographies), characterize the small‐scale spatiotemporal variability of fluxes (e.g., diurnal variation and spatial heterogeneity due to microtopographies), and capture the evolution pattern of chamber headspace gas concentrations, could effectively improve cumulative flux estimates at the field scale. Our guidelines on FCSs and GSSs can serve to the improvement of non‐steady‐state chamber methodology. Plain Language Summary: Ecosystems may mitigate or intensify global warming depending on the ecosystem−atmosphere greenhouse gas exchanges. Quantification of greenhouse gas exchanges at a field scale involves a high degree of uncertainty due to the error of flux measurements and spatiotemporal variability of fluxes. The greenhouse gas fluxes are usually measured with the non‐steady‐state chamber method, that is, placing a bottomless chamber on an accessional base frame in soils and measuring the change rate of gas concentrations in the chamber headspace. Minimizing the bias and uncertainty of non‐steady‐state chamber measurements is crucial for assessing the role of ecosystems on global warming. This study evaluated the effects of non‐steady‐state chamber methodology on estimating cumulative methane and nitrous oxide emissions from a typical wetland in the permafrost region of northeast China. The optimization of measurement schemes, for example, flux calculation and gas sampling schemes, can effectively improve cumulative flux estimates at the field scale. The findings respond to the question of how to allocate the limited observation resources to minimize the bias and uncertainty of quantifying greenhouse gas exchanges over a field scale. Key Points: Optimized flux calculation schemes were established based on the evolution pattern of chamber headspace gas concentrationsOptimization of flux calculation and gas sampling schemes can effectively improve cumulative flux estimates at the field scaleCapturing small‐scale spatiotemporal variabilities of fluxes deserves the top priority in the allocation of the measurement resource [ABSTRACT FROM AUTHOR]

The Grain for Green Project (GGP) aims to protect and improve the ecological environment, end farming on sloping farmland, and plant trees and restore forest vegetation. China's GGP has been widely implemented, but its impact on the environment is rarely evaluated from farmers' perspectives. This study took place in Zhidan and Yanchang Counties, Shaanxi Province. Farmers' attitudes towards the GGP were investigated through semi-structured interviews to understand their perceptions of changes in ecosystem services and their level of ecological awareness, as well as analyzing which factors had the greatest impact on them. Our results indicate that some farmers are not satisfied with the GGP and are unwilling to participate in future GGPs, which is not only due to the dissatisfaction with subsidies offered but also because the needs of the farmers have been ignored. From the perspective of farmers, the GGP has greatly reduced soil erosion and air pollution but has had no effect on improving water quality and protecting biodiversity. More male farmers are willing to participate, and farmers with higher levels of education are more satisfied with the GGP. We also found that the level of understanding of ecological cognition affected farmers' attitudes, and farmers with different levels of knowledge differ in their willingness to participate. Our research found that many farmers were dissatisfied with the GGP. To improve this situation, it is necessary to improve the ecological awareness of farmers. At the same time, policy makers should also further understand the needs of farmers in order to make reasonable management strategies. [ABSTRACT FROM AUTHOR]

The internal correlation of plant, litter and soil stoichiometric characteristics and their responses to the environment are helpful for revealing nutrient cycling mechanisms. However, few studies have assessed the nutrient relationship between plant, litter and soil and nutrient stock along elevational gradients, which limit the understanding of nutrient relationships in the ecosystem. To gain insight into the forces of nutrient stock and its stoichiometric ecological characteristics along the elevational gradients in forest ecosystem, we investigated the carbon (C), nitrogen (N) phosphorus (P) contents and stoichiometric ratios of dominant plants, litter and soil layers at different elevations (900–1600 m) in Daiyun Mountain. The results showed the following: (1) C, N and P contents showed an increasing order as plant > litter > soil in each elevation of Daiyun Mountain. Dominant plants were limited by N each elevation. C, N and P contents of plants at high elevation were higher than those at low elevation and significant correlations were found between plant and litter TN, TP and air and soil temperature (negative), which conforms to the Temperature-Plant Physiological Hypothesis (TPPH). (2) Significant correlations were found between plant C:N and litter C:N (positive); between litter C:P and soil N:P (positive); and between litter C:P and soil C:N (negative). (3) Elevation and slope were essential environmental factors to the stoichiometric ratio of plant and litter, and pH was the main factor that correlated negatively to soil stoichiometry ratio. Litter provided a link between plant and soil, and there was a coupling among plant, litter and soil nutrients. The results could provide a theoretical basis for understanding the nutrient cycling for the subtropical forest ecosystem of China. [ABSTRACT FROM AUTHOR]

After decades of development, the indoor environment in China has changed. A systematic review was conducted from peer‐reviewed scientific papers with field test data of indoor radon in China from 2000 to 2020 for three types of buildings. The mean concentrations of indoor radon for dwellings, school buildings, and office buildings are 54.6, 56.1, and 54.9 Bq/m3. The indoor radon concentration was related to seasons, climate regions, ventilation, decoration, and other factors such as soil and outdoor air. Colder seasons, especially in severe colder areas of China, newer decorated buildings, closed windows, and doors were all associated with higher indoor radon concentrations. Variables like climate region and ventilation showed statistical significance in the correlation analysis. Regarding the increasing trend of indoor radon concentration in China during the last two decades, further study of indoor radon is necessary especially for school buildings and office buildings, and will help access its environmental burden of disease in China more accurately. [ABSTRACT FROM AUTHOR]

The Anninghe fault (ANHF) and the Zemuhe fault (ZMHF), located in the southeast of the Tibetan Plateau, have a high level of seismic hazard and are among the most active faults in China. This study performed the first measurements of soil gas CO2 at three sites across the ANHF and the ZMHF. The fault locking (FL) depth and extent of different segments of the ANHF and the ZMHF were inverted using the negative dislocation model based on global positioning system velocity data acquired during 2009–2015. Results showed that the degassing intensity of CO2 in the ZMHF is substantially higher than in the ANHF, which is spatially consistent with the degree of inverted FL. The inversion results revealed that the level of coupling, including the locking depth and extent, along the southern segment of the ANHF is markedly greater than in the northern segment of the ZMHF. Soil gas CO2 geochemistry yielded different spatially anomalous features, indicating that the faults have different properties and permeability. The intensive locking of the ANHF and ZMHF segments has reduced permeability through self‐sealing processes, which has restricted the escape of gas from the deep crust. Correspondingly, a creeping fault with a low level of coupling could maintain high permeability, which would be favorable for CO2 migration. Plain Language Summary: Soil gas refers to the multicomponent gas enriched in surface soil, which usually shows higher concentrations near faults because of the enhanced permeability. The spatiotemporal distribution of soil gas CO2 on an active fault is sensitive to changes of crustal stress/strain related to seismic activity. Geodynamics can be studied in a variety of ways, such as GPS (global positioning system) and soil gas. In order to figure out the relationship between soil gas CO2 degassing and active fault motion that can be inverted by GPS, we performed the first measurements of soil gas CO2 at three sites across the active faults in southeastern Tibetan Plateau and inverted the spatial fault locking (i.e., a parameter that can reflect the fault motion state) along the faults. We find that the degassing intensity of CO2 is spatially consistent with the degree of inverted fault locking. The high locking degree of the fault constrains the migration of CO2, whereas the creeping fault with a low locking degree is more favorable for the discharge of gas from deeper layers up toward the surface. Key Points: Concentrations of soil gas CO2 from the active fault zones were determinedLocking degree of different segments of the active faults was invertedCO2 concentrations are correlated with the locking degree of the active faults [ABSTRACT FROM AUTHOR]

Coal-fired power plants (CFPPs) are an important anthropogenic mercury (Hg) source in China, and it is crucial to understand the environmental impacts of this detrimental element emitted from this source. In the present study, field experiments were conducted for measuring Hg in ambient atmosphere and upland agricultural soils within a radius of 10 km surrounding a large scale coal-fired power plant (1550 MW) in Tangshan, Hebei province. Short-term (20 min) average of gaseous elemental mercury (GEM or Hg0) in ambient air varying from 1.5 to 9.0 ng/m3 and total Hg (THg) in surface agricultural soil (0–20 cm) varying from 9.2 to 43.5 μg/kg at different sites were observed. THg in two soil cores decreased with depth, with concentrations being 2–2.5 times higher in the surface layer than that in the deep layer (50–60 cm), indicating the possibility of the atmospheric input of Hg. Based on the information of the total atmospheric Hg emission since this CFPP's operation in 1970s and the increased THg in nearby soils, it was estimated that about 3.9% discharged Hg has accumulated in the nearby agricultural soils. The low retention rate of the total emitted Hg by soils is a result of high proportion of Hg0 (79.5%) in stack gas emission and potential loss of Hg from soil surface reemission. The positive shifting (~ 0.5‰) of Hg isotopic signature (δ202Hg) from deep soil to surface soil reflected Hg deposition from nearby CFPP emissions that are featured with much heavier Hg isotopic signatures inherited from feed coal (δ202Hg: –0.50‰) and different combustion products (δ202Hg: –0.95 to 3.71‰) compared with that in deep soil layer (δ202Hg: ca –1.50‰). Overall, this study demonstrated that this CFPP has a slight but distinguishable effect on the elevation of ambient GEM and agricultural soil THg in the local environment. [ABSTRACT FROM AUTHOR]

Radon (222Rn) is a radioactive gas that occurs naturally in the soil and is harmful to the environment and health. However, the measuring the amount of radon flowing is challenging. This study reveals the mechanism responsible for radon transportation and concentration variation, the main driving forces acting, and the key factors operating in the vadose zone. In this study, two separate holes were used to monitor the amount of earth-air and radon flowing in and out of the soil in the extremely arid region in China where the Mogao Grottoes are located. Using a closed-system model, the quantity, characteristics, and regularity of the flow of earth-air and radon were thus determined on daily and yearly timescales. The same patterns of variation in earth-air flow and radon concentration were found at the two sites, both depending on the variation in the atmospheric pressure (AP). When the AP decreases, earth-air flows out from the soil with a high radon concentration. Conversely, when the AP increases, earth-air enters into the soil with a low radon concentration. Thus, radon is continuously emitted from the soil. The concentration of radon in the earth-air is proportional to the rate of flow of earth-air and therefore increases as the AP decreases. The radon emission also varies with the seasonal variation in temperature and AP, which is high in summer and low in winter. On a daily timescale, the radon varies in a bimodal manner. Therefore, the net amount of radon emitted from the soil is positively correlated with the amplitude of the AP fluctuation, temperature, soil porosity, and thickness of the vadose zone. The atmospheric pumping is the main driving force responsible for the radon emission. However, the surface closure, landform, cracks, faults, grain size, pore structure, soil adsorption, basal uranium/radium, salts, wind, lunar cycle, latitude and altitude have important effects on the number of radon emission. As such, it provides a scientific basis for the effective utilization of radon and prevention of its emission from soil. [Display omitted] • This study used a new measurement method to monitor the amount of Rn emitted. • The characteristics of radon flow was revealed by monitoring. • Rn in the vadose zone undergoes piston-like movement. • The key factors influencing the vertical transport of Rn were revealed. [ABSTRACT FROM AUTHOR]

Background and aims: Graminoid-dominated wetlands have been subjected to widespread shrub encroachment, yet the effect of this shift in species composition on litter decomposition remains unclear, especially in the standing-dead stage. Methods: We collected labile (Deyeuxia angustifolia) and recalcitrant (Carex schmidtii) graminoid leaf litter from a freshwater wetland in northeast China, and used the litterbag method to characterize litter ash-free dry mass (AFDM) loss and nitrogen (N) release in the air and on the soil surface in open wetlands and two shrub islands (Salix floderusii producing phenol-poor litter and Betula fruticosa producing phenol-rich litter) over 360 days of decomposition. Results: Litter decomposition in the air and on the soil surface responded differentially to shrub expansion. In the air, AFDM loss and N release for both labile and recalcitrant litter were often lower in shrub islands than in open wetlands. On the soil surface, labile litter decomposition was decelerated in the presence of shrubs with phenol-rich litter, but accelerated in the presence of shrubs with phenol-poor litter. Despite the absence of significant differences in N release, recalcitrant litter AFDM loss was lower in shrub islands than in open wetlands after 360 days of decomposition on the soil surface. Conclusions: Shrub encroachment retards litter decomposition in the air, but the effects on litter decomposition on the soil surface vary with shrub type and litter degradability in graminoid-dominated wetlands. Moreover, these findings emphasize that standing litter decomposition should be considered to enhance our understanding of shrub encroachment effects on litter decomposition in these wetlands. [ABSTRACT FROM AUTHOR]

Based on the radionuclide distributions in sedimentary coal-bearing strata, this study analyzed the microrelease mechanisms of radon in coal-bearing strata. It was found that the microrelease process includes three stages: emanation, migration, and exhalation. Based on this, an experimental apparatus was independently designed for monitoring radon during compression of coal/rock samples from coal-bearing strata, whose major components include an electrohydraulic servocontrolled rock mechanics testing system, an airtight container, coal/rock samples, radon output device, and a continuous emanometer. The developed apparatus was preliminarily utilized for uniaxial compression tests on mudstone samples taken from the #21105 coalface of the Fourth Coal Mine in Yili Coalfield, China. The test results show that before sample failure under the uniaxial compressive load (UCL), the radon concentration is negatively correlated with the applied UCL and the magnitude of imposed elastic deformation. Increasing the applied load shortens the period of stable deformation, gradually decreasing the porosity of the rock, and as a result of declining the concentration of radon emanation from the rock. Finally, suggestions for future research are proposed, including mathematical equations to express the correlations between different experimental parameters and fractal characteristics of radon release from porous media. [ABSTRACT FROM AUTHOR]

Xu, Y.; Liao, B.; Jiang, Z.; Xin, K.; Xiong, Y., and Guan, W., 2021. Emission of greenhouse gases (CH4 and CO2) into the atmosphere from restored mangrove soil in South China. Journal of Coastal Research, 37(1), 52–58. Coconut Creek (Florida), ISSN 0749-0208. Mangroves are a special ecosystem in tropical and subtropical coastal areas. Currently, it is not adequately understood whether soils in restored mangroves are a substantial source of greenhouse gases. The objectives of this study were to determine whether restored mangrove soils are a substantial source of carbon dioxide (CO2) and methane (CH4) and to identify environmental factors affecting soil CO2 and CH4 fluxes in mangrove sites. From August 2019 to January 2020, CO2 and CH4 flux surveys were conducted in soils at four planted mangrove sites, dominated by Excoecaria agallocha, Kandelia obovata, Bruguiera gymnorrhiza, and Hymenocallis littoralis, respectively, in a mangrove reserve in southern China. The results showed that the CO2 and CH4 flux ranges of the four mangrove sites were 0.9432–1.7892 mmol m–2 h–1 and –0.104 to 0.845 µmol m–2 h–1, respectively. Soil CO2 flux was strongly positively (p < 0.01) correlated with soil organic carbon content and positively correlated (p < 0.05) with soil total N content, temperature, and redox potential. CH4 flux was positively correlated with soil temperature. The results confirm that these restored mangrove soils are only a small greenhouse gases source to the atmosphere. [ABSTRACT FROM AUTHOR]

[ Objective) This paper aimed to the quantification of the detailed ranges and dynamics of the environmental factors of the light, temperature, air and moisture in morel cultivation. ( Methods ] Environmental factors in greenhouses for Morchella importuna cultivation were collected in Chengdu plain area using Internet of Things (IoT) technologies. Illumination intensity, air temperature, air relative humidity, oxygen percentage in the air, carbon dioxide concentration in the air, soil temperature and soil water content were recorded every ten mi nutes, in greenhouses with different layers of sunshade-net. Fluctuation models in 24-hour cycle were established for the environmental fac tors at different stages. [ Results] The sunlight in the greenhouses showed a dynamic that indirectly regulated the fluctuating features of the ox Oxygen percentage, relative humidity and temperature in the air, while the average illumination intensity in the greenhouse with the highest mo rel yield were about 2500 - 3500 ks at the noon of sunny days. Sunshade-net effectively prevented over-heating during daytime and over-chill ing during night., diminishing the occurrence of extreme values of air temperature and soil temperature, whereas the cumulative temperatures of the air and the soil, as well as the cumulative values of the relative humidity. oxygen percentage and carbon dioxide concentration in the air, and the soil water content, showed no significant difference between the regimes of different sunshade net layers. The effects of the sunshade-net layers were attenus ting the fluctuations of the environmental factors, The air tem perature was either higher than or similar to the soil temperature during the fruiting stage. (Conclusion) Field conditions ideal for morel cultivation were summarized from the analytical results of the environmental factors, for the reference of field management of morel cul tivation in plain area of southwestern China, which further provided some inspirations for the engineers hoping to develop factory-mode tech nologies of morel production. [ABSTRACT FROM AUTHOR]

Carbonates in soils may act as a potential source of CO2 efflux from calcareous soils to the atmosphere. However, its seasonal dynamics and relationships with soil temperature or soil moisture are not well‐understood. A 5‐yr warming experiment was performed to evaluate the effects of symmetric (all season) and asymmetric (seasonal) warming on soil organic fraction (SOC)‐derived efflux and carbonate‐derived CO2 efflux (partitioned by δ13C signature) from a calcareous soil in the karst region of southwest China. In region where precipitation mostly falls during summer, an average of 2.0°C warming under both symmetric and asymmetric warming scenarios produced 6–34% and 11–14% increases in the SOC‐derived efflux and carbonate‐derived efflux, respectively. The SOC‐derived efflux in the symmetric warming scenario was 1.6 times that of the asymmetric warming scenarios, but no changes were found for the carbonate‐derived efflux. The SOC‐derived efflux was positively correlated with both soil temperature and soil moisture, suggesting an entailment with biotic processes. In contrast, the carbonate‐derived efflux was positively correlated with soil temperature, but was poorly correlated with soil moisture. Thus, the seasonal dynamics of the carbonate‐derived efflux in calcareous soils were likely driven by abiotic processes. [ABSTRACT FROM AUTHOR]

Soil air permeability (ka) is an important parameter to characterize gas transport and exchange in soil. In-situ air permeability tests of loess at different depths in three sites (Xi'an, Yan'an and Heifangtai) were carried out with a vacuum attenuation air permeometer in this study. Two sizes of sleeve probes (φ 8 × 4 cm and φ 6.18 × 4 cm) were tested in the laboratory on undisturbed loess samples to assess the dependence of air permeability on sample size. Results showed that the permeability of the three sites tested in-situ decreased when depth increased. Xi'an loess has the best air permeability, and Heifangtai has the worst. The influence of the initial state on in-situ air permeability was analyzed. Laboratory tests showed that the air permeability values of the two sizes are essentially the same, and the scale effect is small. In-situ and in-lab air permeability were compared, and results of the two probes have a good 1:1 relationship. We also evaluated the validity of the YO model for the determination of the permeability of undisturbed loess in the laboratory. The vacuum attenuation air permeameter can be used to measure the permeability of loess quickly and portable. [ABSTRACT FROM AUTHOR]