Groundwater recharge in an arid grassland as indicated by soil chloride profile and multiple tracers

Previous studies have shown that shallow groundwater in arid regions is often not in equilibrium with near‐surface boundary conditions due to human activities and climate change. This is especially the case where the unsaturated zone is thick and recharge rate is limited. Under this nonequilibrium condition, the unsaturated zone solute profile plays an important role in estimating recent diffuse recharge in arid environments. This paper combines evaluation of the thick unsaturated zone with the saturated zone to investigate the groundwater recharge of a grassland in the arid western Ordos Basin, NW China, using the soil chloride profiles and multiple tracers (²H, ¹⁸O, ¹³C, ¹⁴C, and water chemistry) of groundwater. Whereas conventional water balance and Darcy flux measurements usually involve large errors in recharge estimations for arid areas, chloride mass balance has been widely and generally successfully used. The results show that the present diffuse recharge beneath the grassland is 0.11–0.32 mm/year, based on the chloride mass balance of seven soil profiles. The chloride accumulation age is approximately 2,500 years at a depth of 13 m in the unsaturated zone. The average Cl content in soil moisture in the upper 13 m of the unsaturated zone ranges from 2,842 to 7,856 mg/L, whereas the shallow groundwater Cl content ranges from 95 to 351 mg/L. The corrected ¹⁴C age of shallow groundwater ranges from 4,327 to 29,708 years. Stable isotopes show that the shallow groundwater is unrelated to modern precipitation. The shallow groundwater was recharged during the cold and wet phases of the Late Pleistocene and Holocene humid phase based on palaeoclimate, and consequently, the groundwater resources are nonrenewable. Due to the limited recharge rate and thick unsaturated zone, the present shallow groundwater has not been in hydraulic equilibrium with near‐surface boundary conditions in the past 2,500 years.     

Continuous measurement of whole‐tree water balance for studying urban tree transpiration

Street and garden trees in urban areas are often exposed to advection of strong vapour pressure deficit (VPD) air that can raise the whole‐tree transpiration rate (E_T), known as the oasis effect. However, urban trees tend to have small soil volume compared with natural conditions, and so they are believed to strongly regulate stomata. E_T characteristics of such urban trees have not been well understood because of a lack of reliable measurement methods. Therefore, we propose a novel weighing lysimeter method and investigate the whole‐tree water balance of an isolated container‐grown Zelkova serrata to examine (a) which biotic and abiotic factors determine E_T and (b) which spatial and temporal information is needed to predict E_T under urban conditions. Whole‐tree water balance and environmental conditions were measured from 2010 to 2012. Although leaf area substantially increased in the study period, daily E_T did not vary much. E_T increased with VPD almost linearly in 2010 but showed saturation in 2011 and 2012. Root water uptake lagged E_T by 40 min in 2012. These results suggest that the small planter box interfered with root growth and that hydraulic supply capacities did not increase sufficiently to support leaf area increase. From analysis of water balance, we believe that neglecting soil drought effects on street trees without irrigation in Japan will overestimate E_T over 4–5 sunny days at the longest. This is unlike previous studies of forest.     

Water–rock interaction during the process of steam stimulation exploitation of viscous crude oil in Liaohe Shuguang Oil Field, Liaoning, China

In the process of steam stimulation exploitation of viscous crude oil, the injected water, at high temperature and under high pressure, reacts intensively with the host rock. This kind of water–rock interaction in Liaohe Shuguang Oil Field was studied on the basis of analysis of water composition changes, laboratory experiments, mineral saturation indices analysis, and mass balance calculation. Compared with the injected water, the changes of the composition of discharged water are mainly the distinct decrease of pH, Na⁺, SiO₂ and Cl⁻, as well as the increase of K⁺, Ca²⁺, Mg²⁺, SO ₄ ²⁻ and HCO ₃ ⁻ . Laboratory experiments under field conditions showed: the dissolution sequence of minerals quantitatively is quartz>potassium feldspar>albite, and the main change of clay minerals is the conversion of kaolinite to analcime. Mass balance calculation indicated during the process of steam stimulation, large quantities of analcime are precipitated with the dissolution of large amounts of quartz, kaolinite, potassium feldspar, and CO₂. These results correlated very well with the experimental results. The calculated results of Liaohe Shuguang Oil Field showed that during the steam stimulation for viscous crude oil, the amounts of minerals dissolved (precipitated) are huge. To control the clogging of pore spaces of oil reservoirs, increased study of water–rock interaction is needed.     

Assimilation and Fractional Crystallization Controlled by Transport Process of Crustal Melt: Implications from an Alkali Basalt-Dacite Suite from Rishiri Volcano, Japan

Mechanisms of fractional crystallization with simultaneous crustalassimilation (AFC) are examined for the Kutsugata and Tanetomilavas, an alkali basalt–dacite suite erupted sequentiallyfrom Rishiri Volcano, northern Japan. The major element variationswithin the suite can be explained by boundary layer fractionation;that is, mixing of a magma in the main part of the magma bodywith a fractionated interstitial melt transported from the mushyboundary layer at the floor. Systematic variations in SiO₂ correlatewith variations in the Pb, Sr and Nd isotopic compositions ofthe lavas. The geochemical variations of the lavas are explainedby a constant and relatively low ratio of assimilated mass tocrystallized mass (‘r value’). In the magma chamberin which the Kutsugata and Tanetomi magmas evolved, a strongthermal gradient was present and it is suggested that the marginalpart of the reservoir was completely solidified. The assimilantwas transported by crack flow from the partially fused floorcrust to the partially crystallized floor mush zone throughfractures in the solidified margin, formed mainly by thermalstresses resulting from cooling of the solidified margin andheating of the crust. The crustal melt was then mixed with thefractionated interstitial melt in the mushy zone, and the mixedmelt was further transported by compositional convection tothe main magma, causing its geochemical evolution to be characteristicof AFC. The volume flux of the assimilant from the crust tothe magma chamber is suggested to have decreased progressivelywith time (proportional to t^–1/2), and was about 3 x 10^–2m/year at t = 10 years and 1 x 10^–2 m/year at t = 100years. It has been commonly considered that the heat balancebetween magmas and the surrounding crust controls the couplingof assimilation and fractional crystallization processes (i.e.absolute value of r). However, it is inferred from this studythat the ratio of assimilated mass to crystallized mass canbe controlled by the transport process of the assimilant fromthe crust to magma chambers. KEY WORDS: assimilation and fractional crystallization; mass balance model; magma chamber; melt transport; Pb isotope     

地下水环境平衡的理念在高水压隧道设计中的应用

将维持地下水环境平衡的设计理念应用于高水压隧道的设计中。对设计中防排水参数和抗水压衬砌计算方法进行了探讨。以梨树湾隧道为实例介绍了具体设计方法。该隧道施工结果表明：应用地下水环境平衡的理念设计高水压隧道,对于保护环境、降低隧道造价、加快施工速度都是合理、安全和有效的。     

巴尔喀什湖水量平衡研究

巴尔喀什-阿拉湖流域是中亚地区重要和独特的景观生态系统,巴尔喀什湖是该区域的核心,其水位变化作为巴尔喀什湖流域生态系统及其保护的主要指标,向来备受世人关注.研究巴尔喀什湖水量平衡,对合理确定巴尔喀什湖生态系统保护目标及保护措施,具有十分重要的理论与现实意义.在明晰巴尔喀什湖水系、水位影响因素的基础上,构建了巴尔喀什湖水...     

聊城市水资源可持续利用中存在的问题及对策浅析

聊城市属于资源性缺水地区,为实现以有限的水资源支持和保障经济社会的持续稳定发展,必须作好水资源可持续利用这篇大文章.本文分析了聊城市水资源特点及利用中存在的问题,并就实现水资源可持续利用应采取的工程与非工程措施进行了研究和探讨.     

基于MAPGIS的中国电信网络资源管理系统地址库建设

快速响应客户需求、节约企业成本、提高资源管理效率是电信企业当前保持核心竞争力的关键.为了在中国电信网络资源管理(CTNRMS-GIS) 系统中实时图形化展示用户业务所占用的资源状况, 需要业务支撑(business support system, BSS) 系统的用户地址数据及其业务与关联资源.在基于MAPGIS的中国电信网络资源管理系统的建设中, 将BSS系统地址数据(UNIX服务器, Oracle数据库) 借助FTP中间服务器按约定格式迁移到GIS系统, 建立与BSS保持准实时同步的GIS系统地址库(UNIX服务器, Sybase数据库), 实现了跨数据库平台的数据共享, 并对地址数据与各种资源的关联进行了分析, GIS系统地址库建设使电信企业后端运维建设部门增强了对前端营业部门的支撑能力.      

气候变化对新疆玛纳斯河流域水文水资源的影响

考虑积雪和降水不均等特点,对流域进行分带处理,提出和建立了包含积雪融雪结构的水文评价模型。利用该模型求得未来不同气候变化情况下的月均流量过程,分析气候变化对玛纳斯河流域水文水资源的影响。结果表明:若气温升高2℃,降水减少20%,则夏季径流减少52.59%,冬季径流减少1.77%,年均径流减少46.87%。     

韧性剪切带糜棱岩类质量平衡分析——以豫西秦岭群蛇尾剪切带为例

蛇尾剪切带中糜棱岩的质量平衡分析表明:(1)以Al_2O_3守恒为限制条件,该剪切带损失了10％土的质量和体积,糜棱岩类有Na_2O,Zr,Sr的获得;SiO_2,TiO_2,FeO,Fe_2O_3,MgO,MnO,CaO,K_2O及Co,Ni,V,Cr,Cu,Y则损失了;(2)从初糜棱岩-糜棱岩,初糜棱岩-超糜棱岩和糜棱岩-超糜棱岩得出的质量等比线显示,糜棱岩类之间没有明显的质量和体积损失。糜棱岩组分的得失主要发生在初糜棱岩阶段,同初糜棱岩相比,糜棱岩、超糜棱岩有CaO的获得,FeO,MgO,TiO_2,Cr,Co,V,Y微弱的获得,Na_2O则有轻微的损失。