Mechanical model of deformation-seepage-erosion for Karst collapse column water inrush and its application

With the extension of coal mining in China, fault water inrush has become one of major disasters threatening the safety of coal mine production. Based on the research results related to the mining-induced fault water inrush, this paper proposes a conceptual model of water inrush caused by the erosion synergy of mining-induced rock mass damage rupture and fractured rock mass (fault), derives the permeability evolution equation of the two media, and systematically constructs the cooperative disaster causing mechanism model between mining failure and particle erosion inside faults. The numerical simulation is conducted to study the deformation and failure of rock mass, the particle transport in faults and the evolution characteristics of seepage channel, and systematically explain the temporal and spatial evolution mechanism of seepage catastrophe caused by mining-induced fault inrush. The results show that: ① With the continuous advancement of working face, the damage field of mine floor rock mass is connected with the fault erosion fracture, forming a seepage path of aquifer-fault-mining fracture-working face, and with the increase of erosion time, it finally develops into several dominant water diversion channels, resulting in a sharp increase in water inflow at the working face and a lagging water inrush. ② With the increase of seepage time, the water inflow and fracture opening degree inside faults all show three stages: slow change, sudden increase and stable, and the erosion particle concentration shows a trend of first increasing and then decreasing. ③ Under the geological conditions of the mining area studied in this paper, in order to prevent the occurrence of fault water inrush, the methods such as advanced grouting or leaving water prevention coal pillars can be adopted, and the advance grouting time should be before the bottom plate fracture zone connects faults, if grouting is not applied, the width of the reasonable water prevention coal pillar should not be less than 20 m

Eco-physiological response mechanism of Tamarix chinensis to soil water changes in coastal wetlands of the Yellow River Delta

Elucidating the effect of soil moisture on the adaptation of dominant plants in coastal wetlands is important for predicting the evolution of vegetation in the region. In this paper, Tamarix chinensis, a dominant species in the Yellow River Delta, was used as the object to study the changes of its growth and physiological parameters with increasing soil salinity under different moisture conditions (normal watering, persistent drought and persistent waterlogging). Different salt stress (2‰, 5‰, 8‰, 12‰, 16‰, and 20‰) using pot experiments was also used to reveal the mechanism of soil moisture on its salt tolerance. The results showed that the relative growth rate between 5‰-8‰ soil salinity was the largest, and growth was significantly inhibited above 20‰. Among different moisture conditions, the difference in relative growth rate under normal watering and persistent drought were nonsignificant, while both were significantly lower than those under persistent waterlogging. With increasing soil salinity, relative water content and total chlorophyll content significantly decreased, and cell membrane permeability (malondialdehyde), sodium ion, osmoregulatory substances (proline, soluble protein), and protective enzyme activity (SOD) significantly increased, while changes in non-structural carbohydrates (NSC) were not significant. Compared with normal watering and persistent waterlogging, persistent drought had the lowest leaf relative water content, total chlorophyll content, and sodium ions, and the highest cell membrane permeability, osmoregulatory substances and protective enzyme activity. With increasing treatment time, the relative leaf water content and total chlorophyll content significantly decreased, and cell membrane permeability, osmoregulatory substances and protective enzyme activity increased more significantly than normal watering and persistent waterlogging. NSC increased under normal watering and persistent waterlogging, while significantly decreased under persistent drought. Correlation analysis showed that the relationships between sodium ions, total chlorophyll content and malondialdehyde were various under different moisture conditions. Under persistent drough, malondialdehyde was significantly positively correlated with relative conductivity, superoxide dismutase, proline, soluble protein and soluble sugar. Total chlorophyll content was the key indicator reflecting the salt and waterlogging tolerance of T. chinensis under normal watering and persistent waterlogging, while cell membrane damage was under persistent drought. In summary, T. chinensis has strong salt and waterlogging tolerance, but persistent drought with salt stress can have serious impacts on its growth and survival

Effects of Solar Intrusion on the Calibration of the Metop-C Advanced Microwave Sounding Unit-A2 Channels

This study presents our first discovery about two abnormal problems in the blackbody calibration target associated with the antenna unit A2 in the Metop-C AMSU-A instrument. The problems include the anomalous patterns in both blackbody kinetic temperature Tw and radiative temperature (measured in warm count or Cw), and the time lag between orbital cycles of Tw and Cw. This study further determines solar intrusion as the root cause of the anomalous pattern problem. According to our analysis, solar illumination is constantly observed during each orbit near the satellite terminator, causing anomalous changes in Cw and Tw, characterized by sudden and abnormal increases typically for more than 16 min. The resultant maximum antenna temperature errors due to abnormal increases in Cw are approximately in the range from 0.15 K to 0.25 K, while the maximum errors due to the abnormal increase in Tw are in the range from 0.04 K to 0.07 K, varying with orbit, season, and channel. The time shift feature is characterized with a changeable time lag with the season in the Tw orbital cycle in comparison with the Cw cycle. The longest time lag up to about 18 min occurs in summer through early fall, while the time lag can be decreased down to about 9 min in winter through early spring. Hence, this study underscores the imperative need for future research to rectify radiance errors and reconstruct a more accurate long-term Metop-C AMSU-A radiance data set for channels 1 and 2, crucial for climate studies

Evolution Mechanism of Water-Conducting Channel of Collapse Column in Karst Mining Area of Southwest China

There are many karst collapse columns in coal seam roof in the southern coal field in China, which are different from those in coal seam floor in the northern coal field, due to the stratum characteristics. The karst collapse column in coal seam roof tends to reactivate and conduct water and induce the serious water inrush disaster, when the karst collapse column communicates with the overlying aquifer. In order to reveal the evolution mechanism of water-conducting channel of collapse column in karst mining area of southwest China, the aquifers and water inflow rule in 1908 working face in Qianjin coal mine are analyzed. Besides, the particle size distribution and mineral component of collapse column are researched by the X-ray diffraction test and the screening method, which are the basis for researching the water inrush mechanism in karst collapse column. On this basis, the water inrush of roof collapse column under the influence of mining is researched by establishing the numerical calculation model with the UDEC numerical software. The results show that the water flowing into the 1908 working face comes from the Changxing formation aquifer and Yulongshan formation aquifer above the coal seam, and the proportion of coarse particles and fine particles in collapse column is 89.86% and 10.14%, respectively. With the advance of working face, the water-conducting channel connected the working face with the aquifer, or the surface is formed by collapse pits, karst caves, and collapse column. The research results can be treated as an important basis for the water-preserved mining in southern coal field in China

Effects of Groundwater Mineralization and Groundwater Depth on Eco-Physiological Characteristics of Robinia pseudoacacia L. in the Yellow River Delta, China

Groundwater plays a significant role in influencing the growth and distribution of Robinia pseudoacacia L. plantations, with the largest planting area in the Yellow River Delta, by affecting the soil water–salt environment. This study aimed to clarify the mechanism of groundwater’s influence on the growth of R. pseudoacacia under different levels of groundwater mineralization (GWM) and groundwater depth (GWD). We simulated GWM of 0, 2 and 4 g L−1, and GWD of 0.8, 1.3 and 1.8 m. As GWM increased, soil relative water content (SRWC) and soil salt (dissolved salt) content (SSC) increased; sapling biomass (SB), stem mass (SM), leaf mass (LM), photosynthesis characteristics (maximum net photosynthetic rate (Pn), stomatal conductance (gs), intercellular CO2 concentration (Ci), transpiration rate (E) and water use efficiency (WUE)) decreased; root mass (RM), root mass ratio (RMR) and root–shoot ratio (RSR) first increased then decreased; stem mass ratio (SMR) first decreased then increased; and leaf mass ratio (LMR) increased. As GWD increased, SRWC decreased, but SSC first increased then decreased; SB, RM, RMR, RSR, and photosynthesis characteristics increased; SM and LM first increased then decreased; and SMR and LMR decreased. SRWC and SSC were negatively correlated with SB and photosynthesis characteristics. SRWC was negatively correlated with RMR and RSR, whereas it was positively correlated with LMR. SSC was negatively correlated with SMR, whereas it was positively correlated with LMR. The first principal component, including SB, RM, and photosynthesis characteristics, was related to sapling growth. The second principal component, including RMR, SMR, and RSR, was mainly related to biomass allocation. In conclusion, GWM and GWD affected the soil water and salt content, which were key factors influencing the photosynthesis and growth of R. pseudoacacia. Adjustments in biomass allocation and photosynthesis were the main adaptive strategies of R. pseudoacacia to salt, drought, and flooding stress

Effects of Seed Size and Sand Burial on Germination and Early Growth of Seedlings for Coastal <i>Pinus thunbergii</i> Parl. in the Northern Shandong Peninsula, China

This paper examines the effects of seed size and the depth of sand burial on seed germination and seedling development for Pinus thunbergii. Parl. Seeds from 20- to 30-year old trees grown in the coastal area of Yantai were divided into three size categories (large, medium, and small). The seeds were sown in pots with different depth of sand, and their germination and seedling growth during the first month were investigated. Results showed that large seeds possessed the highest 1000-seed weight and soluble sugar concentration. Large and medium seeds had a higher germination rate, germination index, vigor index, and seedling biomass than small seeds. With the increase in seed size, root mass ratio, root/shoot ratio, specific root length, and specific root area decreased, whereas leaf mass ratio increased. Sand burial depth significantly influenced seed germination and seedling growth, and the highest germination rate and seedling biomass were achieved with 2&#8211;3 cm sand burial. We also found that seedling biomass was positively related to germination rate, germination index, and vigor index, but was negatively related to mean germination time. Moreover, seedling biomass was negatively correlated with root mass ratio and root/shoot ratio, but positively correlated with leaf mass ratio, specific root length, and specific root area. The results suggest that seed size and sand burial depth are key factors in the regeneration of the coastal P. thunbergii forest

Tree Species Distribution Change Study in Mount Tai Based on Landsat Remote Sensing Image Data

Located in the Mount Tai state-owned forest farm, this study adopted Landsat multispectral remote sensing data in 2000 and 2016 on the GEE (Google Earth Engine) platform and selected four phases of images each year according to the phenological period. By dealing with the current situation map of forestry resources in 2000 and the field survey data in 2016, the samples of tree species distribution in 2000 and 2016 were obtained. On the basis of topographic correction with the empirical rotation model, this study used the random forest (RF) classifier to classify tree species from remote sensing images in 2000 and 2016, achieving high classification accuracy. The results showed that, after 16 years of evolution, the percentage of pine species in the forest decreased from 55.69% to 50.22%, with a percentage decrease as high as 5.47%. The percentage of black locust (Robinia pseudoacacia) increased from 10.15% in 2000 to 13.75% in 2016, with an increase of 3.60%. Quercus also had a positive growth in the area. This result reflected the expansion of black locust

Comparison of C, N and P Stoichiometry in Different Organs of <i>Fraxinus velutina</i>

Velvet ash (Fraxinus velutina Torr.) is a dioecious tree species, which is widely used as a part of urban greeneries in saline land of North China. Female and male trees have different nutrient allocation trade-offs in dioecious species. As the fruit production consumes a lot of nutrients, female F. velutina plants grow slowly and are vulnerable to insects and diseases. Ecological stoichiometry can be used to study the physiological mechanism of the growth difference between female and male plants. The purpose of this study was to compare the seasonal patterns of C, N and P stoichiometry and their trade-offs in different organs of female and male F. velutina plants planted in urban green spaces. The fruit C, N and P contents of female F. velutina plants were all lower than those of leaves in the early growing season, but higher than those of leaves in the middle and late growing season. During most months, the leaf C and P contents of females were higher than those of males, while the leaf N content was lower than that of males, which was consistent with the sex-specific resource requirements for reproduction (i.e., high carbon requirements for ovules and high nitrogen demands for pollen). Compared to the females, there were more significant correlations between the stoichiometric indices (element contents and their ratios) of branches and leaves in male plants, and this difference may be related to the fact that the male plants were not involved in nutritional allocation for fruits. The leaf N/P of F. velutina was lower than 14 in the whole growing season, which indicated N limitation. The female and male plants of F. velutina had different sex-specific resource requirements for sex organ formation

Metop-C AMSU-A and AVHRR Sensor Data Recorder (SDR) Data Calibration/Validation (CalVal): Status & Prospective

European Meteorological Operational satellite program (Metop)-C was successfully launched into low Earth orbit at 00:47 UTC on November 7, 2018. METOP-C is the third and final spacecraft of the Metop. The Metop-C satellite carries a variety of instruments including three NOAA sensors: Advanced Microwave Sounding Unit-A (AMSU-A), Advanced Very High Resolution Radiometer (AVHRR), and the Space Environment Monitor (SEM). Both of AMSU-A and AVHRR will improve daily weather forecasts while continuing to monitor long-term changes in Earth’s climate. SEM provides measurements to determine the intensity of the Earth’s radiation belts and the flux of charged particles at satellite altitude. On November 12, 2018, the AVHRR onboard the METOP-C became the first instrument to acquire and disseminate its visible (0.64 µm) and near infrared (0.86 µm and 1.61 µm) data. Nine days after METOP-C was launched, the first day AMSU-A science data was received on November 15, 2018. The Center for Satellite Applications and Research (STAR) in NOAA A is leading a series of calibration and validations (CalVal) activities about AMSU-A and AVHRR Sensor Data Record (SDR) data. The Metop-C AMSU-A and AVHRR SDR CalVals have successfully reached to their beta maturity review on 15 February 2019. A briefing will be presented about status and prospective of Metop-C AMSU-A and AVHRR CalVal. In particular, we will introduce AMSU-A instrument noise performance, Lunar intrusion correction, antenna pattern correction, SDR data quality assessment for AMSU-A by using the JCSDA Community Radiative Model (CRTM), intersensor comparison and double difference methods. We will brief IR Noise Equivalent delta-Temperature (NEdT), Solar channels calibration and other CalVal results for AVHRR instrument and SDR data. Additionally, we will brief the STAR Integrated Calibration and Validation (ICVS) to provide near-real time monitoring for both AMSU-A and AVHRR instrument performance and SDR data quality