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981.
Xianghui Guo Wei-Jun Cai Weidong Zhai Minhan Dai Yongchen Wang Baoshan Chen 《Continental Shelf Research》2008
Seasonal variations in the inorganic carbon system in the Pearl River estuary are examined based on data from five surveys during the spring, summer, fall, and winter seasons. Both total dissolved inorganic carbon (DIC) and total alkalinity (TAlk) values in the freshwater end-members are high in the dry season (>2700 μmol kg−1 for DIC and >2400 μmol kg−1 for TAlk) and substantially lower in the wet season (DIC and TAlk were ∼1000 and 700 μmol kg−1, respectively). Riverine DIC flux and drainage basin weathering rates, however, are significantly higher in the wet season (611×109 mol yr−1 and 13.6×105 mol km−2 yr−1) than in the dry season (237×109 mol yr−1 and 5.3×105 mol km−2 yr−1). 相似文献
982.
河流相砂泥岩薄互层地震反射特征研究 总被引:10,自引:3,他引:7
A sedimentary geological model is established in order to study the seismic reflection characteristics of channel sand bodies. Synthetic seismic shot gathers are simulated using the acoustic wave equation and then are prestack time migrated. On the imaged data, the reflection characteristics and instantaneous attributes are analyzed and log-constrained impedance inversion is tested. Because of wave field interference, the experimental results show that seismic events do not definitely correspond to the channel sand bodies and that seismic modes of occurrence do not represent the actual ones. The seismic events formed by wave interference may lead to errors and pitfalls in sand body interpretation. The corresponding relations between instantaneous seismic attributes and sedimentary sands are not well established. Log-constrained impedance inversion improves the resolution of channel sands. However, if the inverted resolution is forced to be too high, artifacts related to the initial model may occur. 相似文献
983.
长江三峡工程水库蓄水后旅游景观变化预测 总被引:3,自引:0,他引:3
本文论述了长江三峡工程建成后库区旅游景观的淹没和“高峡出平湖”的新景观。据预测,水库蓄水后,受淹没影响的景点39处,峡区峡谷气势有所减弱,但雄姿犹存;水库正常高水位达175m 时,将新增湖泊11处、岛屿14处,支流上可提高旅游开发利用价值的峡谷37条、溶洞15个,许多世界级的自然奇观可望得到开发。届时,三峡工程库区将成为观光游乐、度假休闲、科考探险及从事水上运动的多功能旅游区。 相似文献
984.
阜新井水温于2015年8月出现破年变变化,至2016年3月水温出现加速下降现象,最大降幅达7.2‰℃,距水温井约16m处的体应变井辅助水位亦出现同步下降变化。通过对水温井观测系统、区域地质特征和周边环境等进行调查发现,水温井东北约1km处的新打深水井大量抽水可能是造成水温及水位下降变化的原因。将新井抽水时间与阜新井水温及其他前兆测项观测数据进行对比分析,结果显示水温、体应变和钻孔水位等数据的变化与新打井在成因、空间、时间和强度上都存在明显的相关性。故阜新井水温及辅助水位同步变化为附近新井抽水干扰所致,排除为地震前兆异常的可能。 相似文献
985.
小马村井动水位观测副管设计不合理导致固体潮汐不明显,为此进行固体潮汐观测实验,此后固体潮汐较为明显。因为该井有原油上漂,排水装置的排水口经常堵塞,清淤后需人工调节流量,所以动水位观测难以恢复原状。2017年12月改造排水装置后,结果比较理想。 相似文献
986.
基于Sato模型,采用2016年3月至2018年6月内蒙古东北部及临近地区发生的526次地震事件,挑选ML ≥ 2.0、记录清晰且信噪比较高的102次地震事件,拟合得到内蒙古东北部地区尾波Q值,得到QC(f)=(64.74 ±29.09)f(0.8925 ±0.0765);Q值与依赖指数η成反比,且该区北部Q值偏高,南部Q值偏低,可能与地质构造及地震活动性有关。 相似文献
987.
988.
Effects of Urbanization,Soil Property and Vegetation Configuration on Soil Infiltration of Urban Forest in Changchun,Northeast China 总被引:2,自引:0,他引:2
Peijiang Wang Haifeng Zheng Zhibin Ren Dan Zhang Chang Zhai Zhixia Mao Ze Tang Xingyuan He 《中国地理科学(英文版)》2018,28(3):482-494
Urban forest soil infiltration, affected by various factors, is closely related with surface runoff. This paper studied the effect of urban forest types, vegetation configuration and soil properties on soil infiltration. In our study, 191 typical plots were sampled in Changchun City, China to investigate the soil infiltration characteristics of urban forest and its influencing factors. Our results showed that the steady infiltration rates of urban forest soil were highly variable. High variations in the final infiltration rates were observed for different vegetation patterns and compaction degrees. Trees with shrubs and grasses had the highest infiltration rate and trees with bare land had the lowest infiltration rate. In addition, our results showed that the soil infiltration rate decreased with an increase in the bulk density and with a reduction in the soil organic matter content and non-capillary porosity. The soil infiltration rate also had significantly positive relationships with the total porosity and saturated soil water content. Urban soil compaction contributed to low soil infiltration rates. To increase the infiltration rate and water storage volume of urban forest soil, proper techniques to minimize and mitigate soil compaction should be used. These findings can provide useful information for urban planners about how to maximize the water volume of urban forest soil and decrease urban instantaneous flooding. 相似文献
989.
Qiang Wang Derek A. Wyman Jifeng Xu Yanhui Dong Paulo M. Vasconcelos N. Pearson Yusheng Wan Han Dong Chaofeng Li Yuanshan Yu Tongxing Zhu Xintao Feng Qiyue Zhang Feng Zi Zhuyin Chu 《Earth and Planetary Science Letters》2008,272(1-2):158-171
Changes in oceanic O–Sr isotopic compositions and global cooling beginning in the Eocene are considered to have been caused by the uplift of the Tibetan Plateau. The specific timing and uplift mechanism, however, have long been subjects of debate. We investigated the Duogecuoren lavas of the central-western Qiangtang Block, which form the largest outcrops among Cenozoic lavas in northern-central Tibet and have widely been considered as shoshonitic. Our study demonstrates, however, that most of these lavas are high-K calc-alkaline andesites, dacites and rhyolites. Moreover, they are characterized by high Sr (367–2472 ppm) and Al2O3 (14.55–16.86 wt.%) and low Y (3.05–16.9 ppm) and Yb (0.31–1.48 ppm) contents and high La/Yb (27–100) and Sr/Y (48–240) ratios, similar to adakitic rocks derived by partial melting of an eclogitic source. They can be further classified as either peraluminous and metaluminous subtypes. The peraluminous rocks have relatively high SiO2 (> 66 wt.%) contents, and low MgO (< 1.0 wt.%), Cr (4.94–23.3 ppm) and Ni (2.33–17.0 ppm) contents and Mg# (20–50) values, while the metaluminous rocks exhibit relatively low SiO2 (55–69 wt.%) contents, and high MgO (1.41–6.34), Cr (25.7–383 ppm), Ni (14.13–183 ppm) and Mg# (46–69) values, similar to magnesian andesites. 40Ar/39Ar and SHRIMP zircon U–Pb dating reveal that both peraluminous and metaluminous adakitic rocks erupted in the Eocene (46–38 Ma). Paleocene–Early Miocene thrust faults and associated syn-contractional basin deposits in the Qiangtang Block suggest that this region was undergoing crustal shortening within a continent during the Eocene. The low εNd (− 2.81 to − 6.91) and high 87Sr/86Sr (0.7057–0.7097), Th (11.2–32.3 ppm) and Th/La (0.23–0.88) values in the Duogecuoren adakitic rocks further indicate that they were not derived by partial melting of subducted oceanic crust. Taking into account tectonic and geophysical data and the compositions of xenoliths in Cenozoic lava in northern-central Tibet, we suggest that the peraluminous adakitic rocks were most probably derived by partial melting of subducted sediment-dominated continent of the Songpan-Ganzi Block along the Jinsha suture to the north at a relatively shallow position (the hornblende + garnet stability field), but the metaluminous adakitic rocks likely originated from the interaction between peraluminous adakitic melts generated at greater depths (the garnet + rutile stability field) and mantle. Because the Duogecuoren adakitic rocks must have originated from a garnet-bearing (namely, eclogite facies) source, Eocene continental subduction along the Jinsha suture caused the thickening of the Qiangtang crust. Given that crustal thickening generally equates with elevation, the uplift of the Central Tibetan Plateau probably began as early as 45–38 Ma, which provides important evidence for tectonically driven models of oceanic O–Sr isotope evolution during global cooling and Asian continental aridification beginning in the Eocene. 相似文献
990.