Identification of geological characteristics from construction parameters during shield tunnelling

Acta Geotechnica - This paper proposes a framework to identify geological characteristics (GC) based on borehole data and operational data during shield tunnelling using a fuzzy C-means...     

Mesoscale model simulation of low level equatorial winds over Borneo during the haze episode of September 1997

The large-scale vegetation fires instigated by the local farmers during the dry period of the major El Niño event in 1997 can be considered as one of the worst environmental disasters that have occurred in southeast Asia in recent history. This study investigated the local meteorology characteristics of an equatorial environment within a domain that includes the northwestern part of Borneo from the 17 to 27 September 1997 during the height of the haze episode by utilizing a limited area three-dimensional meteorological and dispersion model, The Air Pollution Model (TAPM).Daily land and sea breeze conditions near the northwestern coast of Borneo in the state of Sarawak, Malaysia were predicted with moderate success by the index of agreement of less than one between the observed and simulated values for wind speed and a slight overprediction of 2.3 of the skill indicator that evaluates the standard deviation to the observed values. The innermost domain of study comprises an area of 24,193 km², from approximately 109°E to 111°E, and from 1°N to 2.3°N, which includes a part of the South China Sea. Tracer analysis of air particles that were sourced in the state of Sarawak on the island of Borneo verified the existence of the landward and shoreward movements of the air during the simulation of the low level wind field. Polluted air particles were transported seawards during night-time, and landwards during daytime, highlighting the recirculation features of aged and newer air particles during the length of eleven days throughout the model simulation. Near calm conditions at low levels were simulated by the trajectory analysis from midnight to mid-day on the 22 of September 1997. Low-level turbulence within the planetary boundary layer in terms of the total kinetic energy was weak, congruent with the weak strength of low level winds that reduced the ability of the air to transport the pollutants.Statistical evaluation showed that parameters such as the systematic RMSE and unsystematic RMSE between the observed and simulated values indicated the modest skill of the model in simulating the low level winds. Otherwise, the equatorial meteorological parameters such as wind speed and temperature were successfully simulated by the model with comparatively high correlation coefficients, lower RMSEs and moderately high indices of agreement with observed values.     

Sensitivity of MM5 and WRF mesoscale model predictions of surface winds in a typhoon to planetary boundary layer parameterizations

Sea surface winds and coastal winds, which have a significant influence on the ocean environment, are very difficult to predict. Although most planetary boundary layer (PBL) parameterizations have demonstrated the capability to represent many meteorological phenomena, little attention has been paid to the precise prediction of winds at the lowest PBL level. In this study, the ability to simulate sea winds of two widely used mesoscale models, fifth-generation mesoscale model (MM5) and weather research and forecasting model (WRF), were compared. In addition, PBL sensitivity experiments were performed using Medium-Range Forecasts (MRF), Eta, Blackadar, Yonsei University (YSU), and Mellor–Yamada–Janjic (MYJ) during Typhoon Ewiniar in 2006 to investigate the optimal PBL parameterizations for predicting sea winds accurately. The horizontal distributions of winds were analyzed to discover the spatial features. The time-series analysis of wind speed from five sensitivity experimental cases was compared by correlation analysis with surface observations. For the verification of sea surface winds, QuikSCAT satellite 10-m daily mean wind data were used in root-mean-square error (RMSE) and bias error (BE) analysis. The MRF PBL using MM5 produced relatively smaller wind speeds, whereas YSU and MYJ using WRF produced relatively greater wind speeds. The hourly surface observations revealed increasingly strong winds after 0300 UTC, July 10, with most of the experiments reproducing observations reliably. YSU and MYJ using WRF showed the best agreements with observations. However, MRF using MM5 demonstrated underestimated winds. The conclusions from the correlation analysis and the RMSE and BE analysis were compatible with the above-mentioned results. However, some shortcomings were identified in the improvements of wind prediction. The data assimilation of topographical data and asynoptic observations along coast lines and satellite data in sparsely observed ocean areas should make it possible to improve the accuracy of sea surface wind predictions.     

Double trouble: subsidence and CO<Subscript>2</Subscript> respiration due to 1,000 years of Dutch coastal peatlands cultivation

Coastal plains are amongst the most densely populated areas in the world. Many coastal peatlands are drained to create arable land. This is not without consequences; physical compaction of peat and its degradation by oxidation lead to subsidence, and oxidation also leads to emissions of carbon dioxide (CO₂). This study complements existing studies by quantifying total land subsidence and associated CO₂ respiration over the past millennium in the Dutch coastal peatlands, to gain insight into the consequences of cultivating coastal peatlands over longer timescales. Results show that the peat volume loss was 19.8 km³, which lowered the Dutch coastal plain by 1.9 m on average, bringing most of it below sea level. At least 66 % of the volume reduction is the result of drainage, and 34 % was caused by the excavation and subsequent combustion of peat. The associated CO₂ respiration is equivalent to a global atmospheric CO₂ concentration increase of ~0.39 ppmv. Cultivation of coastal peatlands can turn a carbon sink into a carbon source. If the path taken by the Dutch would be followed worldwide, there will be double trouble: globally significant carbon emissions and increased flood risk in a globally important human habitat. The effects would be larger than the historic ones because most of the cumulative Dutch subsidence and peat loss was accomplished with much less efficient techniques than those available now.     

同位素填图与深部物质探测(Ⅱ)：揭示地壳三维架构与区域成矿规律

地球深部是大规模成矿作用的“驱动机”、“供应源”和“传输带”。深入揭示深部物质组成与分布、物质循环与能量转换、三维架构与动力过程,对理解成矿作用至关重要。岩浆岩“探针”及区域同位素(如全岩Nd、锆石Hf)填图是探索深部物质组成与演化过程的主要手段,可以探测地壳深部物质组成的三维架构,揭示新生地壳/古老地壳/再造地壳的空间分布与时空演变,从而为提升区域成矿规律认识提供深部物质制约证据,有助于成矿潜力的定量半定量评价及其区域成矿预测。文章重点总结和探讨了岩浆岩全岩Nd同位素和锆石Hf同位素区域填图在解决地壳三维架构与成矿规律方面的应用成果,深入探讨了巨量岩浆岩发育的深部驱动机制及其成矿制约,对比总结了不同类型造山带(如中亚增生造山带、青藏高原碰撞造山带、秦岭复合造山带等)和不同克拉通的地壳深部组成结构与成矿制约特色。研究显示：不论是什么造山带和克拉通,深部年轻地壳分布区制约了铜金、铜镍等矿床的形成分布;古老地壳控制了大型钼矿、铅锌矿、稀有金属等矿产;两者过渡地带常常发育铁矿等。这些研究不仅揭示了区域成矿规律,而且对成矿预测与成矿潜力评价有潜在的应用价值,有可能成为成矿规律研究特别是深部物质探测及成矿背景研究的新方向。     

西南天山木扎尔特群长英质岩地球化学特征及U-Pb年龄的地学意义

西南天山南缘的木扎尔特群长英质岩原岩为英云闪长岩、花岗闪长岩、奥长花岗岩、石英二长岩.岩石地球化学特征表明:物源来自于下地壳,形成环境为大陆边缘.应用锆石LA-ICP-MSU-Pb定年法,在二云母二长片麻岩中获得3个年龄值.(1909±100)Ma代表片麻岩形成年龄,这是屹今为止,该地质体内发现的最古老同位素年龄;(617±30)Ma代表木扎尔特群形成后遭受第一期构造、变质和岩浆活动热事件的主体年龄,这一热事件持续约317Ma,在新疆称为塔里木运动;(281±31)Ma代表第二期构造、变质和岩浆活动热事件,与早二叠世末地壳深部调整,导致地幔热流上升,形成弥散型大陆热伸展构造有关.研究结果不仅确定了木扎尔特群可作为塔里木中央地块古元古代基底的代表,也为进一步研究塔里木盆地北缘地质演化问题提供了基础资料.     

埋藏岩溶洞穴垮塌深度定量图版及其在碳酸盐岩缝洞型储层地质评价预测中的意义

通过对岩溶洞穴垮塌的岩石力学原理及塔里木盆地奥陶系实钻资料的分析,基本明确了洞穴埋藏垮塌的控制因素是岩石抗弯强度、洞穴尺度、洞穴距风化暴露面的距离等,并得到了洞穴垮塌深度的定量图版。该图版对于钻前预测现今埋藏于地下的碳酸盐岩洞穴是否已经垮塌、洞穴埋藏演化史精确恢复以及对裂缝—洞穴型储层的评价预测具有较强的实践意义。     

Adsorption of phenanthrene on Al (oxy)hydroxides formed under the influence of tannic acid

Although there has been substantial research done on adsorption of metals/metalloids by Al (oxy)hydroxides, little is known regarding the adsorption of polyaromatic hydrocarbons (PAHs) on Al (oxy)hydroxides, especially those formed in the presence of organic acid. This paper investigated the adsorption of phenanthrene on Al (oxy)hydroxides formed with initial tannate/Al molar ratios (MRs) 0, 0.001, 0.01, and 0.1 (referred to MR0, MR0.001, MR0.01, and MR0.1, respectively) through batch adsorption experiments and FTIR study. The results showed that Al (oxy)hydroxides were important sorbents for phenanthrene. The adsorption kinetic data were fitted well with the pseudo-second-order equation. According to a modified Freundlich model, the adsorption capacities of Al (oxy)hydroxides followed a descending order of MR0.1 > MR0 ≥ MR0.01 > MR0.001, which was inconsistent with the organic carbon content in the Al (oxy)hydroxides. Adsorption capacity correlated with the specific surface area, micropore area, and micropore diameter of Al (oxy)hydroxides, yet the relationships were not statistically significant (P > 0.05). FTIR results showed that physical interaction was essential in phenanthrene adsorption onto the Al (oxy)hydroxides, which could be explained by an entropy-driven process. Surface hydrophobicity of Al (oxy)hydroxides played a key role in phenanthrene adsorption. Additional π–π electron donor–acceptor interaction of phenanthrene (acting as electron donor) with aromatic ring of tannic acid (electron acceptor) could be also important in phenanthrene adsorption by high MR Al (oxy)hydroxides, yet it needs further study. The findings obtained in the present study are of fundamental significance in understanding the mechanism of immobilization of PAHs in low organic matter but oxide-rich soils.     

Sulfate Reduction and Sulfur Cycles at Two Seagrass Beds Inhabited by Cold Affinity <Emphasis Type="Italic">Zostera marina</Emphasis> and Warm Affinity <Emphasis Type="Italic">Halophila nipponica</Emphasis> in Temperate Coastal Waters

To evaluate the impact of invading seagrass on biogeochemical processes associated with sulfur cycles, we investigated the geochemical properties and sulfate reduction rates (SRRs) in sediments inhabited by invasive warm affinity Halophila nipponica and indigenous cold affinity Zostera marina. A more positive relationship between SRR and below-ground biomass (BGB) was observed at the H. nipponica bed (SRR = 0.6809 × BGB ? 4.3162, r ² = 0.9878, p = 0.0006) than at the Z. marina bed (SRR = 0.3470 × BGB ? 4.0341, r ² = 0.7082, p = 0.0357). These results suggested that SR was more stimulated by the dissolved organic carbon (DOC) exuded from the roots of H. nipponica than by the DOC released from the roots of Z. marina. Despite the enhanced SR in spring-summer, the relatively lower proportion (average, 20%) of acid-volatile sulfur (AVS) in total reduced sulfur and the strong correlation between total oxalate-extractable Fe (Fe_(oxal)) and chromium-reducible sulfur (CRS = 0.2321 × total Fe_(oxal) + 1.8180, r ² = 0.3344, p = 0.0076) in the sediments suggested the rapid re-oxidation of sulfide and precipitation of sulfide with Fe. The turnover rate of the AVS at the H. nipponica bed (0.13 day^?1) was 2.5 times lower than that at the Z. marina bed (0.33 day^?1). Together with lower AVS turnover, the stronger correlation of SRR to BGB in the H. nipponica bed suggests that the extension of H. nipponica resulting from the warming of seawater might provoke more sulfide accumulation in coastal sediments.     

基于生物可利用性与宽浓度范围的Hakanson潜在生态风险指数法的创建——以小秦岭金矿区农田土壤为例

Hakanson潜在生态风险指数法是土壤重金属潜在生态风险评价的一种常用方法,研究与实践证明其有效性的同时,也发现了其不足之处:忽略了土壤重金属不同形态之间潜在生态风险的差异,且只重视重金属含量高于参考值时的生态风险,而对低于参考值时的情况没有给予考虑,以致特定情况下的评价结果不能很好地反映实际生态风险,因而有必要创建适用性更广的Hakanson潜在生态风险指数法。为此,基于全过程控制优化的思想,引入了生物可利用性毒性系数,并将修正浓度与参考值差值引入计算公式,创建了基于生物可利用性与宽浓度范围的Hakanson潜在生态风险指数法,实现了对重金属不同形态风险贡献的差异及重金属浓度低于参考值情况下潜在生态风险的准确把握。以小秦岭金矿区为典型区域,辅以对采集土样重金属总量及5种形态含量的分析,开展案例研究。结果表明,基于生物可利用性与宽浓度范围的Hakanson潜在生态风险指数法能客观地揭示土壤重金属的潜在生态风险,具有更大的适应性,是一种有效的潜在生态风险评价方法。