Experimental investigation of internal erosion behaviours in inclined seepage flow

Internal erosion is one of the most common causes of failure in hydraulic engineering structures, such as embankments and levees. It also plays a vital role in the geohazards (such as landslides and sinkhole developments) and more importantly, the earth landscape evolution, which has a broad environmental and ecosystem impacts. The groundwater seepage is multi-directional, and its multi-dimensional nature could affect the initiation and the progression of internal erosion. With a newly developed apparatus, we carry out nine internal erosion experiments under five different seepage directions. The results reveal that the critical hydraulic gradient increases as the seepage direction varies from the horizontal to the vertical. After a global erosion is triggered, preferential erosion paths distribute randomly from the bottom to the top of the specimen. If the seepage direction is not vertical, small preferential erosion paths merge into a large erosion corridor, in which the loss of fine particles is significant but negligible outside. Results of experiments manifest that the erosion is heterogeneous and three-dimensional, even in the unidirectional seepage flow. The particles are rapidly eroded at the early stage of the erosion, indicating a high erosion rate. With the erosion time increasing, the particle loss slows down and even ceases if the time is long enough. The erosion rate increases if the seepage direction approaches a vertical direction. Overall, the erosion rate approximately decreases with erosion time exponentially. We proposed exponential equations to illustrate the variation of the erosion rate in the erosion process.     

Early development of Costaria costata (C. Agardh) Saunders and cultivation trials

Costaria costata (C. Agardh) Saunders is one of common kelps distributed in many coastal areas worldwide; however, in China, no reports have been made on cultivation of the genus. To investigate potential cultivation of the species in the northern part of China, trials on isolation and preservation of the gametophytes were conducted using C. costata from Korea; growth and development of the gametophytes were observed. We showed that at 10±1°C, 60 μmol m⁻²s⁻¹ and 12:12 h (L:D), freshly released zoospores settled down within 1 hour, and then developed into the primary cell during the following 2 days. After a vegetative growth phase lasting 6–8 days, female gametophytes became 3–4 times larger in diameter than that of the primary cell, but still remained at a unicellular stage, while male gametophytes divided into 4–10 cells with only a slight change in size. Fertilization occurred within 10 days after the zoospores were released from the sporangia, and the apical and basal tissues of the juvenile sporophyte divided and differentiated into the blade and stipe. Temperature and irradiance influenced gametophytic vegetative growth and developmental patterns. Generally, low irradiance (15 μmol m⁻²s⁻¹ and 30 μmol m⁻²s⁻¹) was unfavorable to the induction of fertility, but it enhanced female gametophyte division. The optimal conditions for vegetative growth were 15°C and 30 μmol m⁻²s⁻¹. After transplantation of the juvenile seedlings and after eight months cultivation, the harvested mature blade reached 194 cm in length and 32.7 cm in width. Our study proves that it is feasible to implement propagation and large scale cultivation of C. costata in northern China.     

Changes in nitrogen and phosphorus and their effects on phytoplankton in the Bohai Sea

Systematic studies of the changes in dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) and their effects on phytoplankton over the last 30 years in the Bohai Sea are presented. The amount of sewage disposal, use of fertilizer and the Huanghe River runoff were found to have a significant influence on the DIN or DIP concentrations in the Bohai Sea over the last 30 years. Moreover, the changes in DIN and DIP resulted in changes in the limiting nutrients of phytoplankton in the Bohai Sea from nitrogen in the early 1980s to nitrogen-phosphorus in the late 1980s, and then to phosphorus after the 1990s. In addition, changes in nitrogen and phosphorus had a significant effect on the phytoplankton community structure. The half saturation constant (K _s) was used to evaluate the effect of nutrients on the phytoplankton community structure in the Bohai Sea over the last 30 years. Cell abundance percentages of dominant phytoplankton species with high K _s values for phosphorus and low K _s values for nitrogen have decreased since the 1980s, while those of dominant phytoplankton species with low K _s values for phosphorus and high K _s values for nitrogen increased during this period.     

滇池盆地东缘白邑-横冲断裂南段的浅层地震勘探研究

本文用浅层地震反射波法对可能穿越昆明新城区东部第四系覆盖区的白邑-横冲断裂南段进行了探测,结果表明:采用浅层地震反射波法探测隐伏断层是有效的,在滇池盆地东缘,白邑-横冲断裂南段东支在隐伏区存在,断面接近直立,视倾角约80°,具有高倾角张性正断性质,基岩垂直错距为10—13m,断裂规模由北向南减小;同时,没有发现西支次级断层存在迹象。据土层测龄结果,东支断裂最新活动时代为第四纪中更新世晚期。     

用GPS数据研究汾渭盆地构造应力场变化

利用2004—2007年观测的GPS数据,采用格林函数法对汾渭盆地地壳15 km深处的最大主应力和剪应力进行了计算。结果表明：1）汾渭盆地的应力场变化分布具有高度不均匀性,山区和盆地的应力场变化性质相反:山区应力场以增加为主,盆地应力场以减小为主;2）宝鸡至咸阳一带的剪应力变化与汤浴至蒲城一带的剪应力变化存在相反的性质。     

Light carbon isotope events of foraminifera attributed to methane release from gas hydrates on the continental slope,northeastern South China Sea

In 2013, the China Geological Survey and Guangzhou Marine Geological Survey conducted the second Chinese gas hydrate expedition in the northern South China Sea(SCS) and successfully obtained visible gas hydrate samples. Five of the thirteen drilling sites were cored for further research. In this work, Site GMGS2-08 is selected for the stable isotopic analysis of foraminifera present in the boreholes in order to reveal the carbon isotopic characteristics of the foraminifera and their response to methane release in the gas hydrate geological system. Our results show that the methane content at Site GMGS2-08 is extremely high, with headspace methane concentrations up to 39300 μmol L~(-1). The hydrocarbon δ~(13)C values, ranging from-69.4‰ to-72.3‰ PDB, distinctly indicate biogenic generation. Based on the δD analytical results(~(-1)83‰ to~(-1)85‰ SMOW), headspace methane is further discriminated to be microbial gas, derived from CO_2 reduction. By isotopic measurement, five light δ~(13)C events are found in the boreholes from Site GMGS2-08, with foraminiferal δ~(13)C values being apparently lower than the normal variation range found in the glacial-interglacial cycles of the SCS. The δ~(13)C values of benthic Uvigerina peregrina are extremely depleted(as low as~(-1)5.85‰ PDB), while those of planktonic Globigerinoides ruber reach-5.68‰ PDB. Scanning electron micrograph(SEM) studies show that foraminiferal tests have experienced post-depositional alteration, infilled with authigenic carbonate, and the diagenetic mineralization is unlikely to be related to the burial depths. The correlation calculation suggests that the anaerobic oxidation of organic matter has only weak influences on the δ~(13)C composition of benthic foraminifera. This means that the anomalous δ~(13)C depletions are predominantly attributed to the overprinting of secondary carbonates derived from the anaerobic oxidation of methane(AOM). Furthermore, the negative δ~(13)C anomalies, coupled with the positive δ18O anomalies observed at Site GMGS2-08, are most likely the critical pieces of evidence for gas hydrate dissociation in the geological history of the study area.     

柴达木盆地北缘侏罗系大煤沟组7段油页岩低放射性控制因素

以探讨柴达木盆地北缘侏罗系大煤沟组7段(J2d7)油页岩低放射性的控制因素为目的,选取鱼卡地区典型井目的层段的油页岩和暗色页岩为研究对象,结合测井资料及含油率、有机地球化学、X射线衍射、元素地球化学等岩心测试分析资料,对二者的组构、水体介质条件、放射性物质供给特征及其与岩石放射性的关系进行详细对比分析。结果表明：与暗色页岩段相比,油页岩整体具有低的自然GR值,具有高的含油率、有机质丰度及沉积期还原性较强水体介质条件,具有较低的黏土矿物含量及沉积期母岩区较弱的风化程度。初步分析得出,有机质富集及贫氧水体介质条件对于区内油页岩的低放射性无明显影响,而古气候条件由温湿到逐步干热,导致陆源黏土矿物及放射性物质输入有限是油页岩低放射性形成的关键。     

中国公众CO2减排的支付意愿：来自4个省市的案例

利用非市场价值评估的方法——条件价值法,通过估算公众对CO₂减排政策的支付意愿,评估中国减缓气候变化政策的价值。利用从北京、上海、山东、福建4个省市收集的1653份有效调查问卷,建立支付意愿模型。结果表明,绝大部分参与者对CO₂减排政策持明显的支持态度,平均每人每年愿意支付201.86元人民币以支持减排行动。其中,北京地区的参与者CO₂减排的支付意愿最高,其次为福建和山东,上海参与者的支付意愿最低。模型显示,年轻、男性和中共党员参与者愿意支付较高的额度支持CO₂减排行动,收入水平高、对目前的生活状况满意、对气候变化问题有较好理解的参与者支付意愿也高。这一研究的政策启示是：中国低碳发展需要将公众对气候政策的支持意愿转化为切实的低碳行动,在设计碳税等减排机制时还要关注不同地区和收入群体在支付意愿和能力上的差异。     

燃气管道地震紧急处置装置设计和示范应用

震后火灾是破坏性地震发生后城市面对的主要危害之一。对于城市中燃气管网,建立地震紧急处置系统尤为重要。在日本、美国和我国的台湾地区,均因城市天然气管网建立了紧急处置系统而取得了减轻地震次生火灾的实效。我国是多地震的国家,随着管道燃气的日益普及,地震紧急处置设施非常重要。本文采用美国Northridge2000小型地震燃气阀,结合所设计的一种燃气管道地震紧急处置装置,在昆明市区,分别用于4户民居小管径燃气管道和一个大管径燃气管道,开展燃气管道的地震紧急处置示范应用。进行的人工触发试验显示,紧急处置装置响应与预期的一致,但还需实际地震的检验。本文介绍了燃气管道地震紧急处置的设计和示范应用情况,并对我国开展相关工作需要解决的问题进行了讨论。