Accumulation and ecological effects of soil heavy metals in conventional and organic greenhouse vegetable production systems in Nanjing,China

The spatial variability of soil heavy metals in conventional and organic greenhouse vegetable production (CGVP and OGVP) systems can reveal the influence of different farming activities on their accumulation and plant uptake. This provides important basic data for soil utilization and pollution risk assessment. Based on horizontal and vertical spatial analysis, this paper presents the spatial variability and accumulation of soil heavy metals. The effects on plant uptake and factors influencing heavy metal accumulation are presented using the two typical greenhouse vegetable sites in Nanjing City, China as examples. Results showed that different greenhouse vegetable production systems had their own dominant heavy metal accumulation, specifically, Hg and Pb in CGVP system and Cd in OGVP system. The spatial analysis showed that horizontally, distribution of soil properties and heavy metal concentrations in the two sites showed decreases from specific regions to the periphery for organic matter (OM), Cd, Cu, Hg, Pb, and Zn in CGVP and OM, As, Cd, Cu, Hg, Pb, and Zn in OGVP. Vertically, soil properties and heavy metals mainly vary in the topsoil. The key factor for the accumulation was excess fertilizer input. Variation of soil properties and the accumulation of soil heavy metals significantly influenced heavy metal uptake by plants. However, accumulation risk varied according to different heavy metals and different plant species. Environmental management of these two kinds of production systems should pay more attention to fertilizer application, plant selection, and soil properties.     

Experimental research on expansion characteristics of Mengzi expansive soil with water,salt and acid immersion

Swelling tests of Mengzi remolded expansive soil inundated with different types of wetting fluids (distilled water, saline water and acidic water) were carried out using advanced consolidometer. Swelling characteristics of expansive soil under different initial conditions were studied. The dose–response model was used to fit the rules of swelling time interval for expansive soil with water immersion. The quantitative relationships between the swelling deformation and initial conditions (initial water content, initial dry density and overburden pressure) were attained using 3D regression analyses. The differences in deformation rules of expansive soil with water immersion in each region are bigger for the differences of genetic types, mineral compositions, chemical characteristics of soils and sample preparation techniques and instrument error. The expansion deformation rules of soil immersed in salt and acid solution are the same as the rules of soaked soil. The important indices obtained can be provided to the engineering design, construction and stability evaluation of expansive soil slopes.     

Fluoride and arsenic hydrogeochemistry of groundwater at Yuncheng basin,Northern China

High fluoride and arsenic concentrations in groundwater have led to serious health problems to local inhabitants at Yuncheng basin, Northern China. In this study, groundwater with high fluoride and arsenic concentration at Yuncheng basin was investigated. A majority of the samples (over 60%) belong to HCO₃ type water. The predominant water type for the shallow groundwater collected from southern and eastern mountain areas was Ca/Mg-Ca-HCO₃ types. For the shallow groundwater from flow through and discharge area it is Na-HCO₃/SO₄-Cl/SO₄/Cl type. The predominant water type for the intermediate and deep groundwater is of Na/Ca/Mg-Ca-HCO₃ type. According to our field investigation, fluoride concentration in groundwater ranges between 0.31 and 14.2 mg/L, and arsenic concentration ranges between 0.243 and 153.7 μg/L. Out of seventy collected groundwater samples, there are 31 samples that exceed the World Health Organization (WHO) standard of 1.5 mg/L for fluoride, and 15 samples exceeds the WHO standard of 10 μg/L for arsenic. Over 40% of high fluoride and arsenic groundwater are related to the Na-HCO₃ type water, and the other fifty percent associated with Na-SO₄-Cl/HCO₃-SO₄-Cl type water; little relation was found in calcium bicarbonate type water. A moderate positive correlation between fluoride and arsenic with pH were found in this study. It is due to the pH-dependent adsorption characteristics of F and As onto the oxide surfaces in the sediments. The observed negative correlation between fluoride and calcium could stem from the dissolution equilibrium of fluorite. The high concentration of bicarbonate in groundwater can serve as a powerful competitor and lead to the enrichment of fluoride and arsenic in groundwater. Most of the groundwater with high fluoride or arsenic content has nitrate content about or over 10 mg/L which, together with the observed positive correlations between nitrate and fluoride/arsenic, are indicative of common source of manmade pollution and of prevailing condition of leaching in the study area.     

Kiel Ⅳ-IRMS双路在线分析微量碳酸盐的碳氧同位素

石笋能重建百年、十年的气候事件,为达到空间高分辨率,对微量碳酸盐的检测提出了更高要求,传统磷酸酸解法的样品用量大(约10 mg)已经无法满足微量样品的分析,而激光探针质谱分析方法需对检测结果进行校正。本文采用KielⅣ-IRMS双路在线分析技术对微量碳酸盐样品的碳、氧同位素进行检测研究其可行性,并以GBW 04405和NBS 19为例研究了不同样品量的碳酸盐标准样品在不同反应时间对同位素分馏的影响。结果表明,由于标准样品所需的反应时间不同,从而导致同位素分馏值的差异。对样品量为4~85μg的标准样品GBW 04405进行检测,δ13C、δ18O测量值分别为0.574‰±0.027‰、-8.519‰±0.065‰,与推荐值0.57‰±0.03‰、-8.49‰±0.14‰基本一致,表明该方法能够满足微量碳酸盐测试的要求。将KielⅣ-IRMS双路在线分析技术与GasbenchⅡ-IRMS检测方法进行对比,对于标准样品GBW 04405,KielⅣ-IRMS所用样品量约为50μg,δ13C、δ18O测量值分别为0.576‰±0.012‰、-8.501‰±0.050‰,GasbenchⅡ-IRMS所用样品量约为140μg,δ13C、δ18O测量值分别为0.569‰±0.034‰、-8.590‰±0.099‰。表明KielⅣ-IRMS方法相比于GasbenchⅡ-IRMS方法所需样品量少,精度高,结果重现性好,该方法在碳酸盐样品的应用上能达到空间高分辨率。     

新疆库车盆地钾盐科探1井含盐系地球化学特征及找钾指示

在盐湖沉积演化过程中,钾盐矿物在盐类沉积的中晚期阶段才开始析出。因此,研究含盐系盐类的沉积地球化学特征,不仅可以从侧面获取岩盐的沉积物源和成盐古卤水蒸发浓缩程度等地球化学信息,而且更能揭示古盐湖钾盐富集趋势。文章通过对库车盆地钾盐科探1井钻取的岩芯样品进行高精度采样测试,得出岩盐中Mg×103/Cl、K×103/Cl、Li×103/Cl与K+、Mg2+、Li+、Ca2+、Cl-含量的垂向变化规律。并与库车盆地其他钻孔中的岩盐含钾性进行对比,同时,依据钻井剖面岩性特征,与潜江凹陷和大汶口凹陷含盐系剖面进行对比,论述研究区成盐的地球化学特征,对其钾盐成矿前景进行分析和评价。     

蒙古国满都拉探矿区地质特征及流体包裹体研究

满都拉探矿区位于蒙古国南戈壁省满都拉苏木。矿区地表中元古界白云岩中出露大面积含孔雀石、蓝铜矿和辉铜矿的硅化蚀变带,含铜矿物与石英脉在空间上紧密共生,石英中的流体包裹体可能保留了原生成矿流体特征。为确定其成矿地质体和成因类型,指导后续找矿工作,本文对硅化蚀变带中的石英进行了流体包裹体研究。根据石英中包裹体的产状可将包裹体分为早晚两个阶段,早阶段富含CO2(C型)和水溶液(W型)包裹体,偶见含子矿物(S型)包裹体,流体均一温度为195~384℃,盐度为2.77%~21.37%Na Cl.eqv,反映了原生成矿流体的特征。晚阶段仅出现水溶液(W型)包裹体,流体均一温度集中在95~213℃,盐度为1.27%~12.63%Na Cl.eqv。流体由早阶段的中高温、中盐度、富CO2流体向晚阶段低温、低盐度、贫CO2流体演化。据此推测成矿流体可能为岩浆流体,流体形成深度大约在5.7 km以上。     

中国地热研究的进展与展望(1995～2014)

地热是主要地球物理场之一,地热能是地球的本土能源。李四光在20世纪60年代开创了我国地热科学。到90年代,学科体系基本建立。在过去20年里,我国地热研究得到了进一步深化和拓展。本文从大地热流、岩石圈热结构、地热系统、油气盆地地热、矿山地热、天然气水合物以及气候变化等方面回顾地热研究代表性的创新进展,并对深层地热、海洋地热、环境地热等研究方向作了展望。本文认为,过去20年我国地热研究成果丰硕,国际影响力得到提高,未来发展势头强劲。在经历了由浅入深,从今到古的成长之后,地热研究还将不断拓展领域,为我国地球科学,特别是能源与环境安全做出更大贡献。     

Comparison of Blast-Induced Damage Between Presplit and Smooth Blasting of High Rock Slope

This paper focuses on the comparison of damage induced by smooth blasting and presplit blasting based on the excavation of high rock slope. The whole damage process of the smooth blasting and presplit blasting excavation method is studied by using a cumulative blasting damage numerical simulation technology based on the secondary development of the dynamic finite element code LS-DYNA. The results demonstrate that, in the case of contour blasting with the method of smooth blasting, the total damage of rock slope is a result of cumulated damage induced by the production hole, buffering hole, and smooth hole. Among the total damage, the blasting of the production hole is the main resource, followed by the smooth and buffering holes. For the presplit blasting, the final damage of rock slope is mainly induced by presplit blasting itself. The spatial distribution characteristics of the final damage zone of two methods are compared. Two classes of damage zone could be found in smooth blasting excavation; one of them is the columnar high-degree damage zone around the slope surface and the other is the low-degree damage zone located in the middle of the slope. But in the case of presplit blasting, there is only the columnar high-degree damage zone around the slope surface. Finally, a damage control suggestion for two blasting excavation methods is proposed and verified based on the excavation of the temporary shiplock slopes of the Three Gorges Project in China.     

Micromechanical Modeling of Anisotropic Damage-Induced Permeability Variation in Crystalline Rocks

This paper presents a study on the initiation and progress of anisotropic damage and its impact on the permeability variation of crystalline rocks of low porosity. This work was based on an existing micromechanical model considering the frictional sliding and dilatancy behaviors of microcracks and the recovery of degraded stiffness when the microcracks are closed. By virtue of an analytical ellipsoidal inclusion solution, lower bound estimates were formulated through a rigorous homogenization procedure for the damage-induced effective permeability of the microcracks-matrix system, and their predictive limitations were discussed with superconducting penny-shaped microcracks, in which the greatest lower bounds were obtained for each homogenization scheme. On this basis, an empirical upper bound estimation model was suggested to account for the influences of anisotropic damage growth, connectivity, frictional sliding, dilatancy, and normal stiffness recovery of closed microcracks, as well as tensile stress-induced microcrack opening on the permeability variation, with a small number of material parameters. The developed model was calibrated and validated by a series of existing laboratory triaxial compression tests with permeability measurements on crystalline rocks, and applied for characterizing the excavation-induced damage zone and permeability variation in the surrounding granitic rock of the TSX tunnel at the Atomic Energy of Canada Limited’s (AECL) Underground Research Laboratory (URL) in Canada, with an acceptable agreement between the predicted and measured data.     

Time-Varying Multifractal Characteristics and Formation Mechanism of Loaded Coal Electromagnetic Radiation

Dynamic collapses of deeply mined coal rocks are severe threats to miners. To predict the collapses more accurately using electromagnetic radiation (EMR), we investigate the time-varying multifractal characteristics and formation mechanism of EMR induced by underground coal mining. A series of uniaxial compression and multi-stage loading experiments with coal samples of different mechanical properties were carried out. The EMR signals during their damage evolution were monitored in real-time; the inherent law of EMR time series was analyzed by fractal theory. The results show that the time-varying multifractal characteristics of EMR are determined by damage evolutions process, the dissipated energy caused by damage evolutions such as crack propagation, fractal sliding and shearing can be regard as the fingerprint of various EMR micro-mechanics. Based on the Irreversible thermodynamics and damage mechanics, we introduced the damage internal variable, constructed the dissipative potential function and established the coupled model of the EMR and the dissipative energy, which revealed the nature of dynamic nonlinear characteristics of EMR. Dynamic multifractal spectrum is the objective response of EMR signals, thus it can be used to evaluate the coal deformation and fracture process.