Identification of key parameters controlling dissolved oxygen migration and attenuation in fractured crystalline rocks

In the crystalline rocks of the Canadian Shield, geochemical conditions are currently reducing at depths of 500-1000 m. However, during future glacial periods, altered hydrologic conditions could potentially result in enhanced recharge of glacial melt water containing a relatively high concentration of dissolved oxygen (O2). It is therefore of interest to investigate the physical and geochemical processes, including naturally-occurring redox reactions, that may control O2 ingress. In this study, the reactive transport code MIN3P is used in combination with 2k factorial analyses to identify the most important parameters controlling oxygen migration and attenuation in fractured crystalline rocks. Scenarios considered are based on simplified conceptual models that include a single vertical fracture, or a fracture zone, contained within a rock matrix that extends from the ground surface to a depth of 500 m. Consistent with field observations, Fe(II)-bearing minerals are present in the fractures (i.e. chlorite) and the rock matrix (biotite and small quantities of pyrite). For the parameter ranges investigated, results indicate that for the single fracture case, the most influential factors controlling dissolved O2 ingress are flow velocity in the fracture, fracture aperture, and the biotite reaction rate in the rock matrix. The most important parameters for the fracture zone simulations are flow velocity in the individual fractures, pO2 in the recharge water, biotite reaction rate, and to a lesser degree the abundance and reactivity of chlorite in the fracture zone, and the fracture zone width. These parameters should therefore receive increased consideration during site characterization, and in the formulation of site-specific models intended to predict O2 behavior in crystalline rocks.     

珠穆朗玛峰北坡绒布冰川区水体的化学特征

１９９７－０５在珠峰地区绒布冰川采集的４类水样的实测资料表明,本区各类水体都呈碱性,ＰＨ值的大小顺序为：湖水〉湖水〉表层雪。河水和湖水的阴离子以ＳＯ＾２－４为最大,而表层雪样品以Ｃｌ－最大;     

达索普冰芯中现代环境信息记录

１９９６－０７－０８,中美联合考察队成功地考察了希夏邦马地区达索普冰川,并提出了一支２０ｍ长的冰芯,这支冰芯是迄今为止世界上海拔最高的冰芯。对资料分析发现离子含量变经显示强烈的周期性变化,反映了季节变化的特征。离子浓度高低变化将指示气候的冷暖变化,并与δ＾１８Ｏ存在着对应关系,     

中亚则克台黄土剖面记录的末次冰期以来的环境演变

选取位于中亚伊犁盆地中东部的则克台（ZKT）黄土剖面作为研究对象,基于13 个光释 光年代构建了ZKT 剖面的年代框架,利用黄土沉积速率、粒度以及总有机碳含量重建了伊犁地区 末次冰期以来的环境演变记录。结果表明：（1）伊犁地区末次冰期以来的气候演化阶段可划分为 寒冷期（74.5~60 ka）、温湿期（60~30 ka）、寒冷期（30~11.5 ka）以及11.5 ka 以来的暖湿期, 该气候演化特征与深海氧同位素不同阶段气候特征较为一致;（2）MIS4 至MIS1 阶段则克台剖 面沉积速率呈递减趋势,分别为49 cm·ka^-1、32 cm·ka^-1、13 cm·ka^-1 和8 cm·ka^-1;（3）ZKT 剖面 代表的伊利地区环境演变特征可与格陵兰冰芯进行良好对比,北大西洋地区的快速气候波动信号 在伊犁地区气候记录相对清晰,在时间上呈同步变化。     

末次盛冰期南京长江四桥附近长江古流量估算

利用南京长江四桥的39个地质工程钻孔资料及其它现有资料,已知长江四桥附近约-65～-90m的深槽为末次盛冰期时的长江河槽。根据古河槽断面、形态参数、底部沉积物颗粒级配等,运用河相关系法、泥沙粒径水力学法、地貌水力学法,计算了末次盛冰期时的断面面积、断面平均流速。计算得到末次盛冰期南京长江四桥附近长江古流量约为22000～27000m3/s。初步根据宽深比、悬移质含量、弯曲率等参数值判断末次盛冰期长江四桥附近长江古河型为曲流。     

临沂九曲沂河大桥附近沂河古河槽特征

选择临沂九曲沂河大桥附近沂河断面作为研究剖面.根据九曲沂河大桥的地质勘探钻孔资料,绘制了沂河古河槽地质剖面示意图.沿勘探钻孔进行了浅层地震影像法物探.在下游的G327沂河大桥附近河槽底部和上游约3 km枋河右岸的埋藏阶地上采集了年代样品,获得了1个光释光年代、2个14 C年代.结论认为:沂河古河槽底部断裂带、裂隙发育;九曲沂河大桥附近约53～55 m以下河槽为末次盛冰期时沂河、祊河的古河槽,当时枋河在九曲沂河大桥的下游汇入沂河;约54 m以上为晚冰期以来沂河河槽,晚冰期以后,枋河约在现在入沂河的位置注入沂河.由于河槽宽浅,流量季节变化大,形成分汉-辫状河特征.     

希夏邦马峰北坡达索普冰川区冰、雪、河水的化学特征

１９９７－０９～１９９７－１０间在希峰地区达索普冰川采集的４类水样（表层雪、冰塔冰、冰面河水和河水）的实测资料表明,本区各类水体ｐＨ值的大小顺序为：河水＞冰面河水＞冰塔冰＞表层雪．表层雪和冰面河水所测的阴离子中以ＮＯ－３为最大,而冰塔冰样品以Ｃｌ－最大;阳离子含量基本上以Ｃａ２＋为主．ＳＯ２－４、Ｃａ２＋、Ｍｇ２＋、电导率和ｐＨ值都与所测的阴、阳离子总量有较好的相关关系,随所测的阴、阳离子总量升高而增大．表层雪的电导率、Ｎａ＋、Ｃｌ－、所测的阴、阳离子总量和ＳＯ２－４与海拔高度都有较好的相关关系,随着海拔高度上升而上升．     

Landscape–seascape dynamics in the isthmus between S?rkapp Land and the rest of Spitsbergen: Will a new big Arctic island form?

Transformation of the glaciated isthmus between Sørkapp Land and the rest of Spitsbergen since 1900 is described. The landscape–seascape dynamics depends on the glacial recession determined by climate warming after the Little Ice Age (i.e., since the beginning of the twentieth century, and especially since the 1980s). The isthmus has been narrowed from 28 km in 1899–1900 to 6.2 km in 2013, and lowered by 60–200 m from 1936 to 2005. Two isthmus’ glaciers will have melted, given the current thermic conditions, by 2030–2035. It cannot be ruled out that Sørkapp Land will become an island after that period, because the altitude of the glaciers’ bedrock is close to the sea level. The disappearance of this huge ice mass, even without origin of a sound and island, will lead to a great transformation of the landscape and the ecosystem.