Yunnan Area Research Articles

Analysis of Different Height Correction Models for Tropospheric Delay Grid Products over the Yunnan Mountains

Accurate tropospheric delays are of great importance for both Global Navigation Satellite System (GNSS)-based positioning and precipitable water vapor monitoring. The gridded tropospheric delay products, including zenith hydrostatic delays (ZHD) and zenith wet delays (ZWD), are the most ideal method for accessing accurate tropospheric delays. The vertical adjustment method is critical for implementing the gridded tropospheric products. In this work, we consider the different models used for grid products and assess their performance over Yunnan mountains with complex topography. We summarize the main results as follows: (1) The products can provide accurate ZHD with mean biases of −2.6 mm and mean Standard Deviation (STD) of 1.5 mm while the ZWD results from grid products show a performance with biases of −0.4 mm and STD of 1.3 cm over the Yunnan area. (2) The Tv-based model shows a better performance than the T0-based model and IGPZWD in rugged areas with large height differences. The grid products can provide hourly ZHD with biases of 3 mm and wet delay with mean biases of within 2 cm and mean STD of below 3 cm in the Yunnan mountains, which exhibit a large height difference of around 1.5 km. (3) The radiosondes results confirm that the Tv-based model has an obvious advantage in calculating ZHD height corrections for differences within 2 km while the T0-model suffers from a loss in accuracy in the case of large height differences. If the site is located more than 1 km below the reference height, the IGPZWD model can provide a better ZWD with a mean bias of 1.5 cm and a mean STD of 1.7 cm. With vertical reduction models, the grid products can provide accurate ZHD and ZWD in real time, even if in complex area.

Distribution Pattern of Species Richness of Endemic Genera in Mountainous Areas of Southwest China and Its Influencing Factors

China’s southwest mountainous region is one of the hotspots of biodiversity in the world. However, the study on the pattern of species richness distribution of endemic plants in this region and its influencing factors is still in the exploration stage. A clear regional spatial distribution pattern of plants and its influencing factors are very important for the protection and management of plant diversity in southwest China. In this study, 511 county-level regions in the southwest mountainous region were taken as examples to establish a plant species resource bank in the southwest mountainous region, and the distribution pattern of the proportion and abundance of endemic plant families and genera was analyzed based on 19 climate and environmental factors and 8 human disturbance factors in the southwest mountainous region. The geographical weighted regression model (GWR) was used to reveal the main factors affecting the spatial distribution of species. The results showed that: (1) A total of 4688 species investigated in the southwest mountain belong to 19 families and 32 genera. (2) The endemic species richness in the southwest mountainous region showed a significant uneven spatial pattern, mainly concentrated in the Heng Duan Mountain area, southwest Sichuan and northern Yunnan area, and the Ruoergai-Hongyuan area of West Sichuan Plateau. (3) The results of the GWR model showed that the diurnal mean temperature range, precipitation seasonality and distance from the main road had significant effects on species richness. The study on the distribution of endemic genera and their influencing factors in the southwest mountainous region has important implications for the exploration of the evolutionary history and species conservation of the mountain flora.

Comparison and selection of ground motion prediction equations for the Sichuan–Yunnan area, southwest China

The Sichuan–Yunnan area is one of the most seismically active regions in China. As ground-motion models form a key component of seismic hazard analysis, it is important to select (or develop) appropriate models for this area. The increasing number of digital ground-motion records of earthquakes in this area has allowed the development of local ground motion prediction equations (GMPEs). This study compares and, later, recommends appropriate GMPEs for the Sichuan–Yunnan area. We first evaluate the inherent quality of local GMPEs, with respect to their underlying datasets, the variables used and their functional forms, to determine a set of candidate GMPEs. Then we investigate how well the predictions from the GMPEs match observations computed from strong-motion records of recent earthquakes in this area. The fit between predictions and observations varies significantly amongst the GMPEs. The results suggest that some recent local GMPEs would lead to biased ground-motion estimates due to limitations of their underlying datasets and functional forms. Based on both evaluations of inherent quality and compatibility with observations, only one local GMPE is recommended. A comparison of the predictions from three widely-used non-local GMPEs indicates that ground motions in the Sichuan–Yunnan area appear more variable than those in other regions but that predictions from these non-local GMPEs are generally unbiased. We recommend use of a mixture of robust local and non-local GMPEs within seismic hazard analyses to capture the epistemic uncertainty in ground-motion prediction for this area.

Hazard assessment modeling and software development of earthquake-triggered landslides in the Sichuan–Yunnan area, China

Abstract. To enhance the timeliness and accuracy of spatial prediction of coseismic landslides, we propose an improved three-stage spatial prediction strategy and develop corresponding hazard assessment software named Mat.LShazard V1.0. Based on this software, we evaluate the applicability of this improved spatial prediction strategy in six earthquake events that have occurred near the Sichuan–Yunnan region, including the Wenchuan, Ludian, Lushan, Jiuzhaigou, Minxian, and Yushu earthquakes. The results indicate that in the first stage (immediately after the quake event), except for the 2013 Minxian earthquake, the area under the curve (AUC) values of the modeling performance are above 0.8. Among them, the AUC value of the Wenchuan earthquake is the highest, reaching 0.947. The prediction results in the first stage can meet the requirements of emergency rescue by immediately obtaining the overall predicted information of the possible coseismic landslide locations in the quake-affected area. In the second and third stages, with the improvement of landslide data quality, the prediction ability of the model based on the entire landslide database is gradually improved. Based on the entire landslide database, the AUC value of the six events exceeds 0.9, indicating a very high prediction accuracy. For the second and third stages, the predicted landslide area (Ap) is relatively consistent with the observed landslide area (Ao). However, based on the incomplete landslide data in the meizoseismal area, Ap is much smaller than Ao. When the prediction model based on complete landslide data is built, Ap is nearly identical to Ao. This study provides a new application tool for coseismic landslide disaster prevention and mitigation in different stages of emergency rescue, temporary resettlement, and late reconstruction after a major earthquake.

Leukemia Genotype Analysis of Children with Acute Lymphoblastic Leukemia in Yunnan Area

To analyze 43 leukemia genes in children with acute lymphoblastic leukemia (ALL) in Yunnan province, and provide the basis for the diagnosis and treatment of children with ALL in this area. The clinical data of 428 children with newly diagnosed ALL in Yunnan area from January 2015 to December 2020 were retrospectively analyzed. Multiple nested PCR technology was used to detect 43 common leukemia genes. Among the 428 children with ALL, 159 were positive for leukemia genes, with a positive rate of 37.15% (159/428), and a total of 15 leukemia genes were detected. Among the 159 leukemia gene-positive children, ETV6-RUNX1+ accounted for 25.79% (41/159), followed by E2A-PBX1+ and BCR-ABL+, accounting for 24.53% (39/159) and 23.27% (37/159) respectively. MLL+ accounted for 6.29% (10/159), WT1+ accounted for 4.40% (7/159), IKZF1 gene deletion and CRLF2+ accounted for 3.77% (6/159) respectively. The positive rate of MLL (46.15%) was the highest in ＜1-year old group, the positive rate of ETV6-RUNX1 (10.56%) was the highest in 1-10-year old group, and BCR-ABL+ rate (23.65%) was the highest in >10-year old group. The distribution of leukemia genes in different age groups was statistically significant (P <0.05). The most common fusion gene of children with ALL in Yunnan is ETV6-RUNX1, followed by E2A-PBX1 and BCR-ABL.

New Constraints on the Late Oligocene‐Miocene Thermo‐Tectonic Evolution of the Southeastern Tibetan Plateau From Low‐Temperature Thermochronology

AbstractThe southeastern (SE) Tibetan Plateau (Yunnan) is characterized by low‐relief uplands that were deeply incised by large rivers. The thermal history of basement rocks in this region remains poorly investigated, while this data is needed to elucidate the complex relationship between tectonics and climate in shaping the surface. To better understand its thermo‐tectonic evolution, we carried out apatite fission track thermochronology on 31 samples collected from a large area that covers different tectonic units, including a vertical profile in the middle Mekong River valley; additional zircon LA‐ICP‐MS U‐Pb dating was performed on four basement rocks. Our results confirm that a large portion of Mesozoic crystalline rocks constitute the basement of the SE Tibetan Plateau. Inverse thermal history modeling of fission track data reveal extensive late Oligocene to Miocene rapid basement cooling and exhumation episodes from both inside and outside the active zones (i.e., ductile shear zone and river valley). These thermal events were coincident with the activities of large‐scale strike‐slip faults that dominate the structural framework. Combined with the published data, we propose that widespread crustal shortening and thickening took place in the SE Tibetan Plateau during the Oligocene‐Miocene in the context of a compressive tectonic regime. Low‐temperature thermochronological data reveal that both tectonic forcing and climate‐driven erosion have played important roles in exhuming the basement rocks in the region. It is also deduced that the present‐day relatively low‐elevation landscape of the Yunnan area resulted from complex interaction between regional tectonic activity and surficial erosion since the late Oligocene.

Crustal structure and the seismogenic environment in Yunnan imaged by double-difference tomography

The large-scale faulting and earthquake activities that developed extensively in the Yunnan area are associated with the collision of India and Eurasia. The fine crustal structure can provide a better understanding of the crustal deformation, seismogenic environment, and rupture processes. We performed a new 3-dimensional (3D) P wave velocity structure and seismic relocation using double-difference tomography based on seismic observations. The tomography images show that large-scale low-velocity anomalies spread around the margin of the south Chuan–Dian Block, Xiaojiang fault (XJF), and the Lijiang–Xiaojinhe fault (LJ-XJHF) in the middle and lower crust. There is an obvious high-speed anomaly in the Emeishan large igneous province (ELIP). We infer that the low-velocity anomaly under the LJ-XJHF zone may be derived from the lower crustal flow extruded from the central Tibetan plateau and obstructed by the ELIP, while the velocity anomalies around the XJF might be caused by shear heating, which is associated with the large-deep strike–slip fault and the transmission of stress in the southeast direction. The inversion results also show that the Yangbi earthquake occurred at the NW–SE boundary of high and low velocity from the upper crust to the lower crust, which coincides well with the location of the Yangbi earthquake sequence and the Weixi–Qiaohou fault. Meanwhile, the earthquake relocations show that the aftershocks are mainly distributed at low velocities. All the aforementioned research results indicate that the Yangbi earthquake might be attributed to the intrusion of the soft material flow along the Weixi–Qiaohou fault in the NW–SE direction. These low-viscosity crustal materials would cause brittle fractures and result in NW–SE sinistral strike–slip faults.

Region-dependent site conditions in China: Evidence from borehole data statistics

Consideration of site effects is vital in modeling and predicting earthquake ground motions. However, site conditions can vary markedly between different localities. The regional dependency of site conditions in China has not yet been investigated systematically. In this study, profiles of 6,179 boreholes were collected from four regions in China, i.e., the Capital Metropolitan (CM), Xinjiang (XJ), Guangdong—Guangxi (GG), and Sichuan–Yunnan (SY) areas. Quantitative characteristic parameters including site category, equivalent shear wave velocity (Vse), and the thickness of the overlying soil layer (H) defined by the Chinese seismic code, and VS30 and the median shear wave profile were all analyzed to confirm the dependency on site conditions among the four regions. Investigation revealed that the majority of sites in most regions are classified as Class-II sites with no Class-IV sites, except in CM. In comparison with the other three regions, a larger number of GG sites are classified as Class-I. Sites in XJ are generally characterized by small H values (&amp;lt;20 m) and large Vse values (250 –450 m/s), while those in CM are characterized by large H values (average: ∼50 m) and small Vse values (150 –300 m/s). Generally, the Vse and H values are similar in GG and SY, i.e., the sites are covered by an overlying soil layer that is ∼20 m thick with an average Vse value of ∼250 m/s. A very thin (&amp;lt;5 m) overlying soil layer is observed at many more sites in GG than at sites in the other three regions. The VS30 values in CM, SY, and GG all approximately follow a lognormal distribution with various logarithmic means, i.e., 257.2, 299.6, and 360.9 m/s, respectively. However, the VS30 values of most sites in XJ broadly follow a uniform distribution with a range of 200 –550 m/s. We summarized the characteristics of the median VS profiles of each VS30-based category (C1, C2, and C3) for each region. The median VS profiles between any two regions are mainly manifested as parallel trends for sites in category C1, whereas they present trends of intersection for sites in categories C2 and C3. The findings of this study could serve as a basis for the establishment of a regional empirical model for site-dependent seismic response in China.

InSAR-derived present-day crustal movement of Daliangshan on the southeastern margin of the Qinghai–Tibetan Plateau

SUMMARY The Daliangshan area of Sichuan, China, is located on the southeastern margin of the Qinghai–Tibetan Plateau. It marks the central section of the left-lateral Xianshuihe–Xiaojiang Fault System (XXFS), which plays a crucial role in accommodating clockwise vertical-axis rotation of the expanding Qinghai–Tibetan Plateau relative to the South China Block. The area is seismically and tectonically active, and three major active faults—the Anninghe fault (ANHF), Zemuhe fault (ZMHF) and Daliangshan fault (DLSF)—together accommodate a significant amount of left-lateral strike-slip motion. Here, we present a geodetic study of the Daliangshan area mainly based on satellite interferometric synthetic aperture radar (InSAR). We processed Advanced Land Observing Satellite-2 (ALOS2) Phased-Array L-band Synthetic Aperture Radar-2 (PALSAR2) imagery to reconstruct the present-day interseismic deformation field. We developed an optimal atmospherics phase correction strategy to overcome the significant artefacts caused by ionospheric and tropospheric. By applying a multitemporal analysis on corrected interferograms, for the first time we generated a spatially continuous deformation rate field for the Daliangshan area. The satellite line-of-sight (LOS) rate field agrees with Global Positioning System (GPS) and levelling data to ∼2 mm yr–1, confirming that our processing approach is suitable for use in heavily vegetated areas. The InSAR rate map reveals displacements along the central and southern segments of the DLSF and ZMHF. By applying an inversion based on the Okada model, we quantitatively estimated the kinematic parameters of fault segments. Assuming a simple rectangular fault plane for each fault segment and constrained with the prior knowledge of the left-lateral slip, we determined that the ZMHF has a slip rate of 5.06$\pm 0.99{\rm{\ mm}}\,{\rm{yr}}^{-1}$ with a rake angle of ∼$38^\circ $ gently dipping to the SW. The southern section of the DLSF has a rake of $- 48^\circ \,\,{\rm to}\,\, - 41^\circ $ with the total slip rate of $4.93 \pm 0.4{\rm{\ mm}}\,{\rm{yr}}^{-1}$, dipping towards to the NE at $63.50^\circ \pm 2.31^\circ $. The modelled 3-D rate field has been validated with GPS and levelling measurements. Additionally, the inversion model and strain field suggest that the middle section of the DLSF undergoes strong deformation. We considered the implications of three factors—oblique convergence, gravity-driven movement, and the ELIP beneath the Sichuan–Yunnan area—for complex 3-D velocities in the transitional Daliangshan area.

Effect of Faults on Shale Pore Fracture and Shale Gas Preservation: A Case Study of the Wufeng-Longmaxi Formation in the Northeast Yunnan Area

Effect of Faults on Shale Pore Fracture and Shale Gas Preservation: A Case Study of the Wufeng-Longmaxi Formation in the Northeast Yunnan Area

Analyzing the Seasonal Deformation of the Sichuan–Yunnan Region Using GNSS, GRACE, and Precipitation Data

The Global Navigation Satellite System (GNSS) time series non-constructive deformation shows significant seasonal variations, and the study of its periodic term components and possible physical mechanisms has important theoretical significance and application value for the accurate use of the data and more in-depth analysis. In this paper, wavelet transform (WT) is used to extract the seasonal terms of 24 GNSS continuous station time series, Gravity Recovery and Climate Experiment (GRACE) displacement time series and precipitation data in the Sichuan–Yunnan area, and the three data sets are compared and analyzed in terms of amplitude, phase and cross-correlation coefficient (CC), and the results show that the seasonal deformation in the area is strongly related to the precipitation variation. GNSS and GRACE have good consistency in the vertical component, and the seasonal variation is mainly related to the hydrological load; the difference in the horizontal component is obvious, and the amplitude of the seasonal term of GNSS is larger than that of GRACE, indicating that the resolution of GRACE in the horizontal component is lower than that of the vertical component, and the overall estimation accuracy is lower than that of GNSS. There are significant seasonal terms of annual and semi-annual cycles for the three GNSS components, and the vertical component mainly shows the seasonal deformation of the annual cycle with the strongest seasonality; the horizontal component mainly shows the deformation of the semi-annual cycle, and the seasonality of the N component is stronger than that of the E component, and they are negatively correlated with a coefficient of −0.90.

Gene mutations in children with permanent congenital hypothyroidism in Yunnan, China.

To investigate molecular and clinical characteristics of children with permanent congenital hypothyroidism (CH) in Yunnan, China. The clinical data of 40 children with CH diagnosed and treated in the First People's Hospital of Yunnan Province during January 2016 and January 2019 were retrospectively analyzed. All children were followed up to 3 years old, and Gesell intelligent score was evaluated at age of 1, 2 and 3 years, respectively. Developmental status and prognosis were evaluated. Next-generation sequencing (NGS) was used to screen all exons and exon-intron boundary sequences of the 27 known CH associated genes, and the relationship between genotypes and clinical phenotypes was analyzed. Among the 40 children, the thyroid related pathogenic gene mutations were detected in 23 cases with a rate of 57.5%, and a total of 32 mutations of 8 genes were detected. Mutations in DUOX2, TPO and TSHR genes were the most common ones with mutation frequencies of 65.9%(29/44), 11.4%(5/44) and 9.1%(4/44), respectively. DUOX2 gene mutations were detected in 17 children with CH, and a total of 17 mutation types were detected. p.K530* was the most common mutation in DUOX2 gene, accounting for 20.7%(6/29). There was no significant difference in physical development and intelligence assessment between children with DUOX2 heterozygous mutation and compound heterozygous mutations. None of patients could terminate medication at 3 years of the follow-up and all of them were provisionally assessed as permanent CH. The physical and mental development assessment of children with other gene mutations were also in the normal range. The detection rate of DUOX2, TPO and TSHR pathogenic mutations are high among children with permanent CH in Yunnan area, and no correlation is observed between gene mutation types and prognosis in children with CH.

Knockdown CYP2S1 inhibits lung cancer cells proliferation and migration.

The incidence of lung cancer in Yunnan area ranks firstly in the world and underlying molecular mechanisms of lung cancer in Yunnan region are still unclear. We screened a novel potential oncogene CYP2S1 used mRNA microassay and bioinformation database. The function of CYP2S1 in lung cancer has not been reported. To investigate the functions of CYP2S1 in lung cancer. Immunohistochemistry and Real-time PCR were used to verify the expression of CYP2S1. Colony formation and Transwell assays were used to determine cell proliferation, invasion and migration. Xenograft assays were used to detected cell growth in vivo. CYP2S1 is significantly up-regulated in lung cancer tissues and cells. Knockdown CYP2S1 in lung cancer cells resulted in decrease cell proliferation, invasion and migration in vitro. Animal experiments showed downregulation of CYP2S1 inhibited lung cancer cell growth in vivo. GSEA analysis suggested that CYP2S1 played functions by regulating E2F targets and G2M checkpoint pathway which involved in cell cycle. Kaplan-Meier analysis indicated that patients with high CYP2S1 had markedly shorter event overall survival (OS) time. Our data demonstrate that CYP2S1 exerts tumor suppressor function in lung cancer. The high expression of CYP2S1 is an unfavorable prognostic marker for patient survival.

A 406-year non-growing-season precipitation reconstruction in the southeastern Tibetan Plateau

Abstract. Trees record climatic conditions during their growth, and tree rings serve as proxy to reveal the features of the historical climate of a region. In this study, we collected tree-ring cores of hemlock forest (Tsuga forrestii) from the northwestern Yunnan area of the southeastern Tibetan Plateau (SETP) and created a residual tree-ring width (TRW) chronology. An analysis of the relationship between tree growth and climate revealed that precipitation during the non-growing season (NGS) (from November of the previous year to February of the current year) was the most important constraining factor on the radial tree growth of hemlock forests in this region. In addition, the influence of NGS precipitation on radial tree growth was relatively uniform over time (1956–2005). Accordingly, we reconstructed the NGS precipitation over the period spanning from 1600–2005. The reconstruction accounted for 28.5 % of the actual variance during the common period of 1956–2005. Based on the reconstruction, NGS was extremely dry during the years 1656, 1694, 1703, 1736, 1897, 1907, 1943, 1982 and 1999. In contrast, the NGS was extremely wet during the years 1627, 1638, 1654, 1832, 1834–1835 and 1992. Similar variations of the NGS precipitation reconstruction series and Palmer Drought Severity Index (PDSI) reconstructions of early growing season from surrounding regions indicated the reliability of the present reconstruction. A comparison of the reconstruction with Climate Research Unit (CRU) gridded data revealed that our reconstruction was representative of the NGS precipitation variability of a large region in the SETP. Our study provides the first historical NGS precipitation reconstruction in the SETP which enriches the understanding of the long-term climate variability of this region. The NGS precipitation showed slightly increasing trend during the last decade which might accelerate regional hemlock forest growth.

Verified the rapid evaluation of the edible safety of wild porcini mushrooms, using deep learning and PLS-DA.

How to quickly identify poisonous mushrooms is a worldwide problem, because poisonous mushrooms and edible mushrooms have very similar appearances. Even some edible mushrooms must be processed further before they can be eaten. In addition, mushrooms from different geographical origins contain different levels of heavy metals. Eating frequent mushrooms with excessive heavy metal content can also cause food poisoning. This information is very important and needs to be informed to consumers in advance. Through the demand for the safety of porcini mushrooms in the Yunnan area we propose a hierarchical identification system based on Fourier-transform near-infrared (FT-NIR) spectroscopy to evaluate the edible safety of porcini species. We found that deep learning is the most effective means to identify the edible safety of porcini, and the recognition accuracy was 100%, by comparing two pattern recognition tools, deep learning and partial least square discriminant analysis (PLS-DA). Although the accuracy of the PLS-DA test set is 96.10%, the poisonous porcini is not allowed to be wrongly judged. In addition, the cadmium (Cd) content of Leccinum rugosiceps in the Midu area exceeded the standard. Deep learning can trace Le. rugosiceps geographic origin with an accuracy of 100%. The overall results show that deep learning methods based on FT-NIR can identify porcini that is at risk of being eaten. This has useful application prospects in food safety. © 2021 Society of Chemical Industry.

Fatigue Load Spectrum of Highway Bridge Vehicles in Plateau Mountainous Area Based on Wireless Sensing

In Yunnan and other plateau mountainous areas, hydropower and mineral resources are abundant, and there are relatively many vehicles used for the transportation of large hydropower facilities. The widespread phenomenon of vehicle overload causes severe fatigue among the drivers. However, there is no reference vehicle load spectrum for fatigue analysis in the existing research. The application of wireless sensing technology to bridge health monitoring is favorable for the entire monitoring system’s low-cost and intelligent development. In this study, wireless sensors are used to collect sensing data in the measured area and perform preliminary filtering processing. The data collected by the sensing layer is aggregated at the TD gateway layer to realize local short-term storage of monitoring data, and 3G wireless transmission is used for the effective processing of the data. The clustering method is used to classify the vehicle models based on investigating the most representative expressway traffic flow information in Yunnan Province. Moreover, the weighted probability distribution model of different vehicle models is established through statistical analysis, which simplifies the composition’s fatigue intensity spectrum model. The selection of five vehicles of the equivalent model followed by a six-axle vehicle has the most significant impact on bridge damage as the standard fatigue vehicle. The research results establish a basis for the fatigue design of highway bridges in plateau and mountainous areas and provide data to establish vehicle fatigue load spectra in national highway regions.

Response of Yunnan crustal structure to eastward growth of the Tibet Plateau and subduction of the India plate in Cenozoic

Most previous studies advocate that crustal weakening in the Yunnan area is predominantly the result of eastward growth of the Tibetan Plateau. Here we observe regional variations in the Yunnan crustal structure from the waveform characteristic variations of receiver functions at 342 seismic stations. Furthermore, receiver function imaging along three seismic sections reveals the response of crustal structure to different tectonic evolution. Our results show that northwestern Yunnan is characterized by 49–64 km-thick crust with multi-layer low-velocity materials and local lower crustal “doublet”. These low-velocity structures may reflect partial melting caused by crustal thickening associated with the eastward growth of the plateau. However, in southern and eastern parts of Yunnan, the topography of the Moho varies relatively gently with crustal thicknesses of 26–42 km, and widespread low-velocity zones are located above the crust-mantle boundary. We speculate that these features might favor the action of partial melting of crust triggered by asthenospheric upwelling related to the subduction of the India plate.

Spatial distributions and homolog profiles of chlorinated nonane paraffins, and short and medium chain chlorinated paraffins in soils from Yunnan, China

To preliminarily investigate the occurrence, spatial distributions, homolog compositions, and ecological risks of chlorinated paraffins (CPs) in Yunnan, China, 110 soil samples were collected from an area part of Yunnan, representative of the whole Yunnan area, where had similar characteristics to most parts of Yunnan and 22 pooled soil samples were analyzed for 50 CP congener groups (C9–17Cl5–10). The chlorinated nonane paraffin (C9-CP), short chain (SCCP), and medium chain chlorinated paraffin (MCCP) concentrations in soil samples were 8–109 ng/g (average 39 ng/g), 79–948 ng/g (average 348 ng/g), and 20–1206 ng/g (average 229 ng/g), respectively. The C9-CP homologs contributed 5%–16% of the C9–13-CP concentrations in soils. No significant correlation was found between CP concentrations and the total organic carbon content (P > 0.05). The CP levels in soils from Yunnan were at a medium level compared with those in other areas worldwide. Human activity and atmosphere deposition would influence the levels and spatial distributions of CPs in this area. The concentrations of CPs in east area were higher than those in west area. C10Cl6–7 were the major SCCP congeners and C14Cl6–7 were the major MCCP congeners. Principal component analysis indicated that SCCPs and MCCPs came from different sources. A preliminary risk assessment indicated that these concentrations of CPs in soil from Yunnan do not pose a significant ecological risk for soil organisms.

The oxygen and sulfur isotopic compositions of soluble sulfate in the needles of Pinus massoniana Lamb.: Source discrimination and contribution estimation

In order to identify the sources of sulfate in plant leaves, needles of Pinus massoniana Lamb. were collected from Guiyang (an area seriously affected by acid rain) and Yunnan areas (where acid rain barely occurred) in southwestern China to measure the isotopic compositions of the water-soluble sulfate (δ34SSO4 and δ18OSO4) and leaf water (δ18OH2O). Compared to atmospheric sulfate, all needle samples were quite depleted in 18O, indicating that sulfate in needles was rarely derived from atmospheric sulfate. The δ18OSO4 values in the needles (−5.3‰) were similar to those in the soil (−5.2‰) in the uncontaminated mountain area of Jinning, suggesting that sulfate in needles originated mainly from soil sulfate in barely SO2 pollution areas. However, the δ18OSO4 values in the needles were significantly more negative than that of soil in most areas with relatively severe SO2 pollution, and the δ18OSO4 values in the needles were positively correlated with the δ18OH2O values of leaf water, indicating that a substantial part of the sulfate in the needles might be derived from atmospheric SO2 oxidation in polluted areas. The estimated contributions of atmospheric SO2 oxidation to the sulfate in the needles increased significantly with increasing atmospheric SO2 and needle sulfate concentration. When the atmospheric SO2 concentrations were >30 μg m−3, the contributions of SO2 to needle sulfate were >50%. The δ18OSO4 values in needles decreased obviously with the increase of the distance from both the Steel Plant and the Power Plant, implying that part of needle sulfate likely to be derived from primary sulfate which generated in the industrial plant flues and secondary sulfate which generated in atmosphere.

Pressure–dependent fracture permeability of marine shales in the Northeast Yunnan area, Southern China

A series of pressure–dependent permeability experiments were conducted on the Lower Silurian Longmaxi organic–rich shales in northeast Yunnan area, southern China, to investigate the effects of sedimentary bedding, fracture surface roughness, fracture offset, fracture aperture and effective pressure on shale permeability. The results demonstrate that the sedimentary bedding of shale only has a slight influence on matrix permeability, while the fractures can enhance shale permeability dramatically. Even at a maximum effective pressure of 48 MPa, the permeabilities of aligned fractures (without fracture offset) can increase by about one order of magnitude over the permeabilities of the shale matrix. A power–law relation appears to better describe the pressure–dependency of permeability for the tested shale samples than the exponential relationship. The smoother the fracture surface is, the higher the permeability of aligned fractures will be. The fracture offset can improve fracture permeability distinctly. However, the increasing degree of offset fracture permeability is not proportional to the extent of fracture offset. There is a lower pressure sensitivity for offset fracture than aligned fracture. Fracture aperture is the fundamental factor in controlling the fracture permeability, which shows a positive relationship with the cube of fracture aperture. The pressure–dependence of aligned fractures in shale obeys the Walsh permeability model, but the pressure–dependence of offset fractures in shale does not fit well with this model. By combining the experimental results with the geological characteristics of different types of natural fractures, we conclude that the denser vertical intra–formational tension fractures connect with the bed–parallel slip fractures are favorable for step–like migration and enrichment of shale gas in structural highs. The large–scaled high–angle shear fractures likely damage the preservation conditions of shale gas, which is harmful to shale gas enrichment.