Remediation of TCE-contaminated groundwater using zero valent iron and direct current: experimental results and electron competition model

The objectives of this study are to design an optimal electro-enhanced permeable reactive barrier (E2PRB) system for the remediation of trichloroethylene (TCE)-contaminated water using zero valent iron (ZVI) and direct current (DC) and to investigate the mechanisms responsible for TCE degradation in different ZVI-DC configurations. A series of column experiments was conducted to evaluate the effect of different arrangements of electrodes and ZVI barriers in the column on the TCE removal capacity (RC). In twelve different combinations of ZVI and/or DC application in the test columns, the rate of reductive dechlorination of TCE was improved up to six times with simultaneous application of ZVI and DC compared to that using ZVI only. The most effective arrangement of electrode and ZVI for TCE removal was the column set with ZVI and a cathode installed at the down gradient. Based on the electrokinetic study for the column systems with only DC input, single acid front movement could explain different RCs. An enhanced dechlorination rate of TCE using E2PRB systems, compared to a conventional PRB system, was observed, and is considered to be attributed to more electron sources: (1) external DC, (2) electrolysis of water, (3) oxidation of ZVI, (4) oxidation of dissolved Fe²⁺, (5) oxidation of molecular hydrogen at the cathode, and (6) oxidation of Fe²⁺ in mineral precipitates. Each of these electron sources was evaluated for their potential influencing the TCE RC through the electron competition model and energy consumption. A strong correlation between the quantity of electrons generated, RC, and the energy-effectiveness was found.     

Mathematical Model of the Geothermal Water Resources in the South Hot Spring System in Chongqing

INTRODUCTION Southhotspring,smallhotspringandQiaokou barepresent,betweenthem,thegeothermalwaters ofthesouthhotspringsysteminthesouthhotspring anticlineinChongqing.Thesouthhotspringanti clineisageothermalwaterstoragesystem.Itex tendsfromnorthtosouthinthecentralpartof Chongqing.Itis45kmlongfromsouthtonorthand2kmwide.Thesouthhotspringandsmallhot spring,inthemiddleoftheanticline,arewell known touristattractionsfortheirgeothermalwaters.Ex cessiveexploitationledtoagradualdeclineinthewa terlev…     

近场地震学中3个术语译名的商榷

asperity，barrier和fling step是近场地震学中3个重要的术语。但到目前为止，这3个术语还没有贴切、统一的中文译名。为了便于学术交流和读者对近场地震学的学习和理解，有必要规范统一它们的中文译名。本文基于3个术语产生的物理背景及其意义，建议这3个术语的中文译名分别为：asperity——高强体，barrier——止裂体，fling step——滑冲。     

Variation in noble gas isotopic composition of gas samples from the Aegean arc, Greece

In contrast to most other arcs with oceanic plate subduction, the Aegean arc is characterized by continent–continent subduction. Noble gas abundances and isotopic compositions of 45 gas samples have been determined from 6 volcanoes along the arc, 2 islands in the back-arc region and 7 sites in the surrounding areas. The ³He/⁴He ratios of the samples ranged from 0.027R_A to 6.2R_A (R_A denotes the atmospheric ³He/⁴He ratio of 1.4×10⁻⁶), demonstrating that even the maximum ³He/⁴He ratio in the region is significantly lower than the maximum ratios of most oceanic subduction systems, which are equal to the MORB value of 8±1 R_A. Regional variations in the ³He/⁴He ratio were observed both along and across the arc. The maximum ³He/⁴He ratio was obtained from Nisyros volcano located in the eastern end of the arc, and the ratio decreased westward possibly reflecting the difference in potential degree of crustal assimilation or the present magmatic activity in each volcano. Across the volcanic arc, the ³He/⁴He ratio decreased with an increasing distance from the arc front, reaching a low ratio of 0.063R_A in Macedonia, which suggested a major contribution of radiogenic helium derived from the continental crust. At Nisyros, a temporal increase in ³He/⁴He ratio due to ascending subsurface magma was observed after the seismic crisis of 1995–1998 and mantle neon was possibly detected. The maximum ³He/⁴He ratio (6.2R_A) in the Aegean region, which is significantly lower than the MORB value, is not probably due to crustal assimilation at shallow depth or addition of slab-derived helium to MORB-like mantle wedge, but inherent characteristics of the subcontinental lithospheric mantle (SCLM) beneath the Aegean arc.     

The structure features of stick-slip mechanism of the strike-slip earthquake generating structure in the interior of the Chinese mainland

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太原4.3级和灵石4.4级地震前后的重力场变化

研究了１９９３年６月２６日和１９９４年４月２６日相继在太原和灵石发生的Ｍｓ４．３和Ｍｓ４．４地震前后的重力场变化。指出，这２次地震前后，晋中南地区重力场均有明显的趋势性异常，并结合该区地壳深浅构造等资料分析，认为今后一个时期，晋中南地区具有发生中强地震的可能。     

Hydro-thermal performance of unsaturated bentonite-sand buffer material

Several series of one-dimensional heat and moisture flow tests were performed to examine the moisture and temperature distributions in the buffer material compacted to a dry density of 1.67 Mg m⁻³ and water content of 17.7%. In all tests, water was allowed to infiltrate into a horizontal soil column from one end under a constant hydrostatic head of 276 kPa. Also the specimens were heated from the other end by the heater to a constant temperature.

It is experimentally demonstrated that the moisture moves from both ends toward the mid part of the soil column due to both thermal gradient from one end and hydraulic gradient from the other end. It was observed that, in spite of no overall volume change, local volume change occurs in the system. The measured temperatures along the length of the specimen indicate that temperature distributions stabilize within a short period of time. The time required for the temperature to stabilize decreases as the heater skin temperature increases.

The diffusivity parameters are calculated using the measured moisture and temperature profiles combined with the finite difference method. Powell's optimization algorithm was used to determine the material parameters. Good agreements between experimentally measured and calibrated volumetric water content shows that the diffusion parameters can be expressed in a linear function of the volumetric water content and temperature.     

Analysis of the maximum discharge of karst springs

Analyses are presented of the conditions that limit the discharge of some karst springs. The large number of springs studied show that, under conditions of extremely intense precipitation, a maximum value exists for the discharge of the main springs in a catchment, independent of catchment size and the amount of precipitation. Outflow modelling of karst-spring discharge is not easily generalized and schematized due to numerous specific characteristics of karst-flow systems. A detailed examination of the published data on four karst springs identified the possible reasons for the limitation on the maximum flow rate: (1) limited size of the karst conduit; (2) pressure flow; (3) intercatchment overflow; (4) overflow from the main spring-flow system to intermittent springs within the same catchment; (5) water storage in the zone above the karst aquifer or epikarstic zone of the catchment; and (6) factors such as climate, soil and vegetation cover, and altitude and geology of the catchment area. The phenomenon of limited maximum-discharge capacity of karst springs is not included in rainfall-runoff process modelling, which is probably one of the main reasons for the present poor quality of karst hydrological modelling. Electronic Publication     

重庆市统景地震后的地质环境变化与对策

1989年11月20日重庆市统景发生了近千年来最大的地震,造成房屋倒塌、公路中断、桥梁拉裂,死亡3人,伤150余人,经济损失巨大。由于地震引起了滑坡、崩塌,并涌出了许多温泉,使统景的地质环境发生了显著变化。本文以实地调查资料为依据,论述重庆市统景地震后的地质环境变化与对策。     

The Hot—Spring Genesis of the Shimen Realgar Deposit,Northwest Hunan

The Shimen realgar deposit is characterized by the pipi-shaped orebody and the development of silica sinter and hydrothermal explosive breccia which are typical of hot spring activity.Very similar trace-element associations are noticed between the silica cap and the breccia and modern hot spring waters in the area.The chemistr of ore-forming solutions is also well comparable with that of modern hot spring.,The spring system that gave rise to the mineralization was charged by ground waters heated through thermal conducting systems in the deep crust and,to a lesser extent,by geothermal gradient.ΔD,δ^18O,δ^13CCH4andδ^13CH4andδ^13CCO2values and ^40Ar/^36Ar and 3^He/^4He ratios indicate that the spring system is of crustal derivation.The ore-forming metals were supplied by surrounding strata,particularly those underlying the ore deposits.The mechanim of ore deposition is thought to be hydrothermal explosion and accompanying boiling and abrupt changes in pH and Eh.Located in northwest Hunan,the Shimen realgar deposit is the leading arsenic producer in the country,However,regardless of its long mining history,the genesis of this deposit has long been a puzzle.It was considered to be postmagmatic epithermal in the leading arsenic producer in the puzzle.It Was considered to be postmagmatic epithermal in origin,but this is trongly challenged by filling(metasomatism)in karst environment proposed later by Zhou Zhiquan(1986)also encounters a number of difficulties.For example,why can the pipi-shaped orebody vertically extend up to several hundreds meters without any compatible development in the lateral dimension? A hot spring genesis is suggested in the present paper based on geological observations and laboratory studies conducted by the authors in recent years.