Table of Content

21 April 2015, Volume 29 Issue 2

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Engineering Geology and Environmental Geology

Characteristics and Their Causes of Surface Water-Groundwater Geochemistry in the Hetao Basin, Inner Mongolia

GUO Hua-ming, NI Ping, JIA Yong-feng, ZHANG Bo, ZHANG Yang

2015, 29(2):  229-237. 

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Surface water-groundwater interaction, which not only affects groundwater chemical evolution, but also controls spatial distribution of groundwater components, is one of the important issues in the groundwater field. Fifty-eight groundwater samples and thirty-two rainwater and surface water samples were taken from the Hetao basin, Inner Mongolia. Major components, trace elements and water isotopes were analyzed in those samples. Results showed that surface waters were affected by human activities and evaporation, which contained elevated concentrations of Na⁺, Ca²⁺, SO^2-₄, and NO^-₃. Shallow groundwater had the similar major components and isotopic characteristics with surface water, which indicated that shallow groundwater was affected by surface water. During the infiltration of surface water into the shallow aquifers, incongruent dissolution of silicate minerals, congruent dissolution of halite, barite precipitation, reduction of NO^-₃, Fe oxides and SO^2-₄possibly occurred. Reductive dissolution of Fe oxides was the major cause of high As concentration in shallow groundwater. Arsenic concentration was also affected by  SO^2-₄ reduction. Therefore, synthetical investigation of surface water and groundwater would help to reveal hydrogeochemical processes in aquifers.

Groundwater Hydro-geochemistry in Plain of Manasi River Basin，Xinjiang

LI Qiao, ZHOU Jin-long, GAO Ye-xin, DU Ming-liang，CHENG Fan, LI Feng-xi

2015, 29(2):  238-244. 

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Groundwater is main source of water supply in Manasi River Basin. In order to understand groundwater hydrology characteristics and main process of groundwater formed, hydro-geochemistry in Plain of Manasi River Basin is studied according to the analysis of constant chemistry component, Gibbs graph, ion ratio and isotopic characteristics of groundwater in typical profile using the method of Shukaliefu classification, mathematical statistics method, Gibbs graph and ion ratio. It is found that unconfined water and confined water have a close hydraulic relationship. The values of δ¹⁸O and δD are increase from upstream to downstream. Hydrolysis process occurring in groundwater systems which decided the chemical characteristics of research area, includes evaporation concentration, precipitation and lixiviation of carbonate rock and sulfate rock.

Study on Dispersion Test of Unconfined Aquifers in Riverside Forest Park of Guide County, Xining City

LUO Qi-bin, KANG Wei-dong, GUO Kang

2015, 29(2):  245-251. 

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The problem of groundwater pollution is growing, and the diffuse theory of solute transport is applied to real problems. Establishing the groundwater solute transport model,and correctly predicting the migration and the development trend of groundwater contaminants are the basis of protection of groundwater and pollution control.So determining the dispersion parameters is a critical step for the establishment of groundwater solute transport model and imposes a direct impact on the accuracy and precision of predicted results.In order to analyze the underwater migration rules of Guide County in Xining City,the authors carry on a dispersion test of unconfined aquifers with the theory of radial flow convergence hydrodynamic dispersion,and calculate the dispersion of the unconfined aquifer in test site, then get the longitudinal dispersivity (a_L) of 0.843-0.998 cm and the transverse dispersivity (a_T) experience inferred value of 0.17-0.20 cm, with which we can provide reference data for establishing the groundwater solute transport model, predict groundwater pollution trends and also evaluate the groundwater environmental quality of this region.

Stable Isotope Characteristics of Dissolved Organic Carbon and Inorganic  Carbon in High Arsenic Groundwater

ZHOU Yin-zhu, GUO Hua-ming, LU Hai

2015, 29(2):  252-259. 

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With improved technology for stable isotope analysis, stable carbon isotope has extensively been used in the field of geochemical study. Biogeochemical cycle of groundwater arsenic is one of the hot topics in environmental studies. This paper summarizes research status of stable carbon isotope in groundwater, and introduces pretreating methods and measuring technology of organic and inorganic carbon isotope. Representative groundwater samples with high As concentrations were collected from the Hetao basin, Inner Mongolia, and analyzed for redoxsensitive components, stable carbon isotope in dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC). Results indicate that As distribution is patchy with concentrations between 1.24 and 387 μg/L, and that DOC concentration is relatively high and positively correlated with DIC. In comparison with DOC, DIC is enriched in ¹³C. There is a positive correlation between δ¹³C_DIC-δ¹³C_DOC and δ¹³C_DIC. It indicates that groundwater with low  δ¹³C_DIC and low  δ¹³C_DIC-δ¹³C_DOC values has high contribution of DOC to DIC, which suggests that degradation of organic carbon results in depletion of ¹³C in DIC of groundwater. In addition, there is a negative correlation between  δ¹³C_DIC-δ¹³C_DOC and As. In groundwater with low  δ¹³C_DICand low  δ¹³C_DIC-δ¹³C_DOC values, high As concentrations are observed. High As groundwater experiences intensive biodegradation of organic carbon, and microbial degradation of organic matters plays a significant role in promoting the enrichment of As in groundwater. The increase in bioavailable organic carbon promotes microbial dissimilation, consumes dissolved oxygen, and leads to formation of reducing conditions favorable for As enrichment in groundwater.

Bioavailability Evaluation of Arsenic from Sediments in Shallow Aquifer in Datong Basin

OUYANG Guang-ming, XIE Zuo-ming, SUN Xiao-yan, YANG Dong, WANG Yan-xin

2015, 29(2):  260-264. 

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The aquifer sediment samples collected from the test site of high arsenic level groundwater in Datong Basin were used to investigate the content of bioavailable arsenic and interaction with environmental conditions. The results showed that the contents of Al and Fe were high in these alkaline sediments. Amorphous and poorly crystalline of As with Fe and Al oxides were dominant and followed by residual phase in these sediments. It was 53.54% of all arsenic speciation for Fe and Al oxides containing arsenic, only 14.33% for adsorbed arsenic. Therefore, content of bioavailable arsenic was low in the sediment samples, which was consistent with the result of vitro simulative assay. We also found from vitro simulative assay that the content of bioavailable arsenic was lower in intestine phase than in the stomach phase. The concentration difference of bioavailable arsenic is low between physiologically based extraction test (PBET) and vitro gastrointestinal method (IVG).

Application of High-density Resistivity Method and Induced Polarization Method to Determine a Good Well Location in Groundwater Prospecting

SU Yong-jun, MA Zhen, MENG Li-shan, LIANG Jian-gang, ZHANG Guo-li, LI Jian-guo,

2015, 29(2):  265-271. 

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Fengquan district in Xinxiang, Henan Province lacks of groundwater resources. To tackle this situation, by using the high-density resistivity method, the combination of highdensity resistivity method and induced polarization of symmetrical quadrupole, the authors prospected groundwater resources in complex hydrogeological condition of loose rock and bedrock regions, determined the well location based on hydrogeological data and well condition. The inferred results of high-density resistivity method and induced polarization of symmetrical quadrupole was verified by drilling results, and the success rate of determining well location was 100%, and tracing groundwater resources achieved remarkable results in Fengquan area, which solved the problem of water for people and livestock. Through this practical application and effect analysis of combined geophysical methods or single method in different hydrogeological conditions, the authors sumed up the choice of combination of high-density resistivity method and induced polarization method or high-density resistivity method for special hydrogeological condition in this area. The combination of geophysical methods improves accuracy and reliability of the geological interpretation, and it is popularized and applied in similar hydrogeological condition in groundwater prospecting. This application of combined mode provides the reliable and scientific basis for determining well location in process of groundwater prospecting, and it provides important function for success rate of well drilling.

Model for Groundwater Searching with Drilling in Karst Area near Deep Valley

PAN Xiao-dong, ZHANG Fa-wang, MENG Xiao-jun, ZENG Jie, CHEN Zhi-bing

2015, 29(2):  272-278. 

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Surface water rapidly infiltrates in karst area near deep river valley, and karst groundwater is deeply buried with concentrated runoff; therefore, water resources shortage near deep river valley is serious, which leads to the formation of arid areas. At the same time, in this area, influenced by groundwater discharge surface controlled by deep valleys, groundwater flow is mostly in quick pipe and fracture; storage space distribution and the connectivity of each other bring great difficulties to drill well for searching groundwater. The authors discovered that the underlying clastic rock, reverse fault and overlying clastic rock can cut off the relationship between karst groundwater and deep valley surface water, which lead this area to be local rich water and become the favorable target area for water drilling. Based on the 3 types, with the successful examples, it is classified into 3 water drilling models: the underlying clastic rock water model, inverse water resistance model, and overlying clastic rock water blocking model. These models will give some helps for water drilling in karst area near the deep valley.

Water Table Fluctuation Between Two Parallel Ditches Induced by Time-varying Recharge

XIA Qiang, XU Mo, DENG Ying-er, LI Xiao

2015, 29(2):  279-284. 

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Taking account of exponentially and periodically time-varying recharge, water table fluctuation between two parallel ditches was studied. The analytical solution was derived based on the first linearization method of Boussinesq equation, and Duhamel principle. This paper analyzed the characteristics of phreatic water movement by using three kinds of recharge rate functions including exponent-increase, exponent-decay, and sine function. In the first case, water table rises monotonously with the increasing recharge rate; and watershed between the two ditches moves from the higher level side towards the other sides, but will never cross the middle line of the aquifer. In the exponent-decay case, water table goes up at the beginning, then falls after reaching a peak value; watershed firstly moves towards the middle of the aquifer, then turns back to the higher level side due to the declining recharge rate. In the last case, water table periodically fluctuates corresponding to the sine function recharge; and there is a significant time lag between the stimulator and the respond; watershed sways back and forth between the higher level ditch and the middle of the aquifer. The results can be a clue to study the response of groundwater system to climate change, in addition to the transition rule between surface and ground water.

Suitability Evaluation for Groundwater Source Heat Pumps in Nanjing: Based on AHP and Entropy Weight Method

YANG Lu-mei, ZHU Ming-jun, E Jian, CHEN Ming-zhu, WEI Yong-yao

2015, 29(2):  285-290. 

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Shallow geothermal energy is a kind of green and renewable energy sources. Groundwater source heat pumps are often used to exploit the new energy. It is well known that AHP can take full advantage of subjective views of experts, but it is also accompanied by the bias caused by human factors. On the contrary, entropy weight method, which is an objective evaluation method, does not reflect preferences of decision makers. Based on AHP and entropy weight method, a new method is put forward, which is the linear weighted summation method. According to the geological and hydrogeological conditions, the groundwater temperature field, the groundwater chemistry conditions etc., the suitability of groundwater source heat pumps in Nanjing is evaluated with the linear weighted summation method. The distribution areas of suitable region, sub-suitable region and unsuitable region are attained. The results provide scientific advice for rational and appropriate application of groundwater source heat pumps.

Sedimentary Record of Climate Change During the Past 25.5 ka  of Laohetou Profile from Baiyangdian,Hebei Province

YANG Hui-jun, WANG Yong, CHI Zhen-qing, YAO Pei-yi, DONG Jin, TIAN Ming-z

2015, 29(2):  291-298. 

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Laohetou profile is located in the west of Baiyangdian depression. A 610 centimeter-deep sediment profile was studied in this paper. The AMS ¹⁴C measured data revealed that the sediment profile deposited since 25.5 cal ka BP. Combined with chronological data, grain size characteristics, susceptibility and sedimentary characteristics, the evolutionary process and environment features during the past 25.5cal ka BP were reconstructed. Results showed that there were seven stages as following. 25.5-20.9 cal ka BP(610-515 cm) is a fluvial facies and wind accumulation period; in 20.9-10.7 cal ka BP (515-388 cm), fluvial action is weakened, and wind accumulation may be strengthened; in 10.7-8.6 cal ka BP (388-335 cm), precipitation increases and  water accumulates, lakes expanding during this stage; 8.6-7.2 cal ka BP (335-299 cm) is a wind accumulation period; 7.2-3.2 cal ka BP(299-200 cm) is a lacustrine facies period; 3.2-1.3 cal ka BP(200-110 cm)is a fluvial facies period; from 1.3 cal ka BP to now(110-0 cm)，the precipitation decreases, but fluvial function is still obvious.

Temporal and Spatial Changing Features of Climate in North China Plain

WANG Jin-cui, ZHANG Ying, WEN Ji-li, SUN Ji-chao

2015, 29(2):  299-306. 

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Groundwater is the main water supply source in North China Plain (NCP), and atmospheric precipitation infiltration recharge is the main supply source of the groundwater in this area. Therefore, the studies on temporal and spatial changing features of climate in NCP are of great significance to further analyze the influences of climatic changes on groundwater resources. Based on 18 ground climatological stations in NCP in terms of daily climate observation data from 1951 to 2011, this paper analyzed the spatial-temporal evolution features of climate in NCP. The results showed that the minimum temperature of NCP in recent 60 years increases significantly; the maximum temperature is basically stable; and the mean temperature presents an obviously increasing trend. In the spatial distribution, it gradually decreases from southwest to northeast on the whole and gradually tends to increase from the coastal to inland. The precipitation owns a trend of overall gradual decrease and a trend of being weaker at first and then stronger from piedmont plain to coastal plain. Precipitation distribution characteristics are compared and analyzed in the typical lightest and heaviest rainfall years. The spatial distribution presents significant difference in these different rainfall years. Water surface evaporation shows a declining trend overall and it is more in south and north than in central region. NCP has a warming and drying development trend on the whole. Abrupt change mainly occurred in the middle of 1960s and the beginning of 1970s. The climatic change and human activities are two influential factors of groundwater resources. Effects of precipitation on groundwater will be further intensified in extreme climate condition. Measuring and distinguishing of the influences of climatic change and human activities on groundwater remain to be further explored.

A Chemical Site’s Pollution Risk Prediction to the Proposed Reservoir Based on Solute Transport Simulation

WANG Ping, HUANG Shuang-bing, HAN Zhan-tao, MA Li-sha, ZHANG Wei

2015, 29(2):  307-315. 

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Solute transport simulation is one of the most reliable approaches for groundwater pollution risk assessment. In this paper, to understand the effect to the reservoir from an organic contaminated site as the source of pollution, a precise flow simulation and a solute transport model of organic pollutant leaked from the chemical plant were built based on accurate measurement of flow field in the study area to estimate and analyze the change of groundwater flow and pollution migration after the reservoir built. The simulation results showed that, after the reservoir and two seepage intercepting ditches which had different water levels were built, groundwater flow would change to two kinds of groundwater flow fields, in one condition of which the reservoir would discharge to ditches and the ditches would discharge to vicinity area, while in the other condition the reservoir and vicinity area would both discharge to the ditches. In the two cases, some contaminant plume diffusion were farther than normal condition, but all the diffusion lengths in the direction of reservoir were less than 300 m, so it indicated that the contaminated site will pose no pollution risk to the water quality of reservoir.

Groundwater Vulnerability to Ammonia and Nitrate Based on Modeling  Simulation Method: A Case Study in Changping District of Beijing

JIA Yong-feng ,GUO Hua-ming , WEI Liang

2015, 29(2):  316-323. 

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Assessment of groundwater vulnerability is a prerequisite to protect groundwater resources. It can provide a reference to city planning and construction and has a strong practical significance. The DRASTIC, which is a commonly used for groundwater vulnerability assessment model, had an extensive application in various countries since it is simple and easy to operate. However, the model just gives an overall consideration of general pollutants, and does not take into account biochemical processes of specific pollutants occurring in the vadose zone. It gets the score based on expert experience, which has a certain shortage. The LPI assessment model, which includes adsorption and biodegradation processes of ammonia and nitrate in the vadose zone, is selected to assess groundwater vulnerability to ammonia and nitrate in Changping area of Beijing. Results show that groundwater vulnerability to ammonia and nitrate has a good distribution trend in this area. From the alluvial fans to the flat plain, groundwater vulnerability enhances gradually. The vulnerability to ammonia is greater than nitrate. Besides, the decrease in groundwater table caused by exploitation lowers groundwater vulnerability. The groundwater vulnerability in 2005 is lower compared with 2009 due to the consistent groundwater exploitation. The assessment result is well consistent with groundwater quality data, indicating that the LPI model can be used for groundwater vulnerability assessment.

Environment Characteristics of Polycyclic Aromatic Hydrocarbons in Multimedia in Underground Rivers of Guangxi Karst Areas

LU Li, WANG Zhe, PEI Jian-guo

2015, 29(2):  324-330. 

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In order to understand the contamination characteristics of PAHs in different environmental media of karst underground river, the authors choose the underground river of Guangxi as a study object. Based on the data of air, groundwater, sediment and soil samples gathered during the same term from 2013 to 2014, contrastive analysis is done in light of the concentration, composition and distribution characteristics of 16 kinds of PAHs. The results show that PAHs with 2 to 3 rings are dominated in the air and underground river water, which accounts for 71.66% and 54.84% of the total PAHs. And PAHs with 4 to 6 rings are dominated in the soil and sediment of the underground river, which accounts for 54.26% and 65.06% of the total PAHs. The distribution of PAHs in environmental media along the underground river indicates that the mean concentration PAHs in upstream area is less than that of midstream, and that of midstream is less than that of downstream, because of pollution discharge and absorption. The percentage of variation of PAHs with 2 to 3 rings indicates that the percentage of the underground river is more than that of sediment which is more than that of soil, but the percentage of variation of PAHs with 4 to 6 rings is opposite.

Migration Simulation Research on Hydro-fracturing Fluid in Coal Bed

HOU Hong-bing, CHEN Li, GUO Xiao-jing, MA Lin-na

2015, 29(2):  331-336. 

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To provide scientific foundation for the protection of groundwater environment in Sanjiao block of Lin County in Shanxi Province, the groundwater numerical simulation was conducted to predict the migration of hydro-fracturing fluid in coal bed. A hydrogeological conceptual model was set up based on the analysis of geological structure. The 3^# group coal bed within Shanxi Formation was conceptualized as  a confined aquifer, overlaid by Permian sandstone and mudstone and underlaid by interbeds of mudstone and sandstone functioning as quitards. In addition, groundwater boundary conditions were confirmed. Migration of hydro-fracturing fluid in coal bed of the study area was modeled and predicted. Results indicate that the migration range of hydro-fracturing fluid in the coal bed is within coal hydro-fracturing impact limits, about 300 meters around fractured well.

Saltwater Intrusion Measurement in Laizhou Bay Southern Area Based on Hydro-chemical and Geophysical Methods

LIU Hong-wei, MA Zhen, CHEN She-ming, GUO Xu, SU Yong-jun, DU Dong, HU Yun-zhuan

2015, 29(2):  337-343. 

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Saltwater intrusion interface was measured according to 109 water samples and 31 geophysical profiles based on lithology and well logging data. The results show that: it reached a good effect on saltwater intrusion measurement with hydro-chemical and geophysical methods; the present intrusion interface was located along a line around Taitou-Tianliu-Houzhen-Gudi-Liutuan towns; saltwater and freshwater bodies were better showed on the combined pre-3D profiles through high-density method which provided a good idea on further study.

Water Chemical Changes with Seawater Intrusion (Upstream) in Changle City, Fujian Province

LI Liang，XING Huai-xue，CHANG Xiao-jun，GE Wei-ya，LI Yun-feng，TIAN Fu-jin

2015, 29(2):  344-350. 

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Seawater intrusion is a major environmental geological problem in coastal areas, and the analysis of chemical characteristics of coastal groundwater and river water is significant to delineate the scope of seawater intrusion and to determine the degree of influence.The purpose of the study was to analyze the changes of water chemistry in the process of seawater intrusion. To confirm the correlation, twenty three water samples were collected from aquifers of seawater intrusion of Changle and upstream movement area of Minjiang, which the conventional ion were tested at laboratory. By analyzing the relative changes between major ions and Cl ions with seawater dilution line, and comparing the ionic concentration difference between the actual and the ideal, the water chemical changes with seawater intrusion are investigated. The results were as follows: Types of water chemistry were followed by Na-Cl—Na-Cl·HCO₃—Na·Ca-HCO₃·Cl—Ca-HCO₃ as seawater mixed with freshwater; Increase of Na⁺，Cl^- was the main factor to affect the type of water chemistry and TDS; Content ofCa²⁺，Mg²⁺was higher than ideal concentration line and seawater dilution line，but Na⁺, K⁺ waved. The ratio curve ofBr^-/Cl^- was good agreement with seawater dilution line and can be used as one decisive factor to seawater intrusion.

Chemical Characteristics and Remediation of High Arsenic Groundwater  in Typical Inland Basins of North China

ZHAO Kai, GUO Hua-ming, GAO Cun-rong

2015, 29(2):  351-360. 

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High As concentrations have widely been found in potable groundwater in China, which can cause acute and chronic health effects on humans. It is nessesary to develop economic, efficient and eco-friendly technologies for As removal from As-contaminated groundwater. Chemical characteristics of high As groundwater in arid-semiarid inland basins in Northern China (including the Datong basin, the Hubao basin, the Hetao basin and the Yinchuan basin) were thoroughly reviewed and summarized. High As groundwater was typically characterized by high pH, high concentration of coexisting anions (such as(HCO^-3, SO^2-₄, and Cl^-), and high concentrations of dissolved organic carbon. Furthermore, effects of solution pH, co-existing anions and cations, dissolved organic matter on As adsorption onto activated natural siderite were investigated according to the chemical characteristics of the typical high As groundwater. Results showed that the activated natural siderite had high capacity for buffering solution pH. Arsenic removal was independent on solution pH, coexisting anions, Ca²⁺ and Mg²⁺, and humic acid. It indicated that activated natural siderite had good adsorption selectivity for As under any conditions. In addition, the removal efficiency of activated natural siderite for As(Ⅲ) was slightly higher than that for As(V). Therefore, the activated natural siderite, as an economic, efficient and eco-friendly reaction material, appears to be a promising adsorbent for remediation of As(Ⅲ)-dominated high arsenic groundwater.

Removal of Arsenic in Yangzonghai Lake by Ferric Salt Coagulation  Method and the Stability of Its Precipitate in Sediment

WANG Shi-xiong, JIANG Feng-zhi, CHEN Jing

2015, 29(2):  361-369. 

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Yangzonghai Lake in Kunming was heavily polluted by arsenic with concentration up to 0.134 mg/L. Through taking full account of the large water storage capacity and the low arsenic concentration, a facile generic strategy of removal of arsenic by ferric salt was proposed. The strategy was of great advantage for high efficiency, low cost and ecological safety. Experiments in the laboratory scale demonstrated that FeCl₃ coagulation can remove both As(Ⅲ) and As(Ⅴ) efficiently. Meanwhile, pH value of the water was kept constant after the coagulation process. Therefore, the pretreatment operations of pre-oxidation and adjusting pH value, which were widely employed in literature, were omitted in the treatment engineering for arsenic contamination of Yangzonghai Lake. Solid of FeCl₃·6H₂O was dissolved and diluted to prepare FeCl₃ solution with concentration of 1% FeCl₃, which was sprayed into the lake. Colloid of Fe(OH)₃ formed in the FeCl3 hydrolysis process would co-precipitate with ions of AsO^3-₄and AsO^-₂ in the lake and the stable precipitate was fixed in the sediment of the lake. During the treatment engineering for arsenic contamination of Yangzonghai Lake, the arsenic concentration was decreased from 0.117 mg/L to 0.021 mg/L in the period of November 2009 to September 2010. The concentration of arsenic could be kept below the national standard of category Ⅱ-Ⅲ (<0.05 mg/L) and the removal ratio of arsenic was up to 82.05%. Residual fraction was the overwhelming arsenic form in the lake sediment and its ecological risk was quite low due to its high stability.

Effect of Redox Conditions on the Stabilization Process of Arsenate in Soils

JING Ji-hong，HUANG Guan-xing，CHEN Zong-yu，SUN Ji-chao，LIU Fan， ZHANG Ying

2015, 29(2):  370-376. 

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Effect of redox conditions on the stabilization process of arsenate in soils has been investigated. The results show that the changes of arsenic fractions with increasing contact time are basically consistent after exogenous arsenate entering into soils under different redox conditions. After 180 days, with increasing contact time, water soluble and exchangeable arsenic were down to 2.4%-4.7% and 2.8%-3.2%, respectively, due to the diffusion of arsenic into micropores. Arsenic bound to carbonate is mainly controlled by the pH and the process of surface precipitation. The redistribution phenomenon of arsenic bound to organic matter occurs, and the highest values were up to 48.8%-50.1%, respectively. During the later period of incubation, arsenic bound to organic matter decreases with increasing contact time, while arsenic bound to Fe-Mn oxides and the residual fraction of arsenic increase with increasing contact time. The stabilization process of arsenate in soils will be strengthened when the redox condition is from anoxic condition to oxic condition. In contrast, the stabilization process of arsenate in soils will be inhibited when the redox condition is from oxic condition to anoxic condition. The stabilization process of arsenate in soils is obviously characterized by phases under different redox conditions. There are three phases for the stabilization process of arsenate in soils under the anoxic and transition conditions, while four phases occur under the oxic condition.

Adsorption Analysis of Oxytetracycline on Fluvo-aquic Soils in Beijing

LI Guo-ao, CHEN Zhen-he, LIU Zhi-fu, LI Ye

2015, 29(2):  377-382. 

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Nearly 25% of the total area in Beijing is fluvo-aquic soils, whose adsorption characteristics of tetracycline antibiotics have not been investigated. This research, with the help of OECD Guideline 106, investigated the absorption characteristics of oxytetracycline in the fluvo-aquic soils in Beijing. Our research found that the adsorption kinetics of oxytetracycline in the fluvo-aquic soils is correspond to Elovich equation. The initial concentration of oxytetracycline will affect the adsorption rate. Absorption rate reaches the maximum when the concentration is 2 mg/L and the minimum when 10 mg/L. For absorption percentage, as initial concentration increases, the adsorption percentage first increases and then decreases. The relationship between temperature and average absorption rate is negatively correlated. In our experimental context, the adsorption isotherm is consistent with both linear adsorption isotherm equation and Freundlich isotherm equation. The adsorption is a spontaneous endothermic reaction. Fluvo-aquic soils adsorption capacity of oxytetracycline has a positive relation with the content of silt and clay. Adsorption of oxytetracycline on fluvo-aquic soils was affected by initial concentration, temperature, and soil properties. It is helpful to control pollution of oxytetracycline and protect soils if the mechanisms are understood deeply.

The Assessment of Aquifer Natural Attenuation(BTEX)Capacity  in a Petrochemical Contaminated Site

CAI Jing-yi, CHEN Zong-yu, CAI Wu-tian, GAO Zong-jun, ZHANG Min

2015, 29(2):  383-389. 

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Groundwater pollution is one of the important environmental issues concerned in China. Monitoring and assessing natural attenuation capacity of an aquifer is not only a basic means for preventing and treating groundwater pollution, but also a hot topic in groundwater remediation technology research in abroad. In this paper, authors, taking a petrochemical site in North China Plain as a case study, estimate the aquifer natural attenuation amount of BTEX per year using microbial hydrogeological and chemical method, based on investigation of hydrogeological condition and pollution status in soil and groundwater as well as monitoring of BTEX concentration and some related chemical parameters in groundwater. This research result provides an empirical and basic data for assessment of natural attenuation capacity of petroleum contaminated sites in China.

Optimization of Soil Heavy Metal Sequential Extraction Procedures

LIU Dan-dan，LIU Fei ，MIAO De-ren

2015, 29(2):  390-396. 

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The environmental risks of heavy metals depend on its speciation distribution in contaminated soils. The chemical speciation analysis was one of the hot topics in environmental sciences. In recent years, the most popular sequential extraction procedures were Tessier and BCR. Nethier Tessier nor BCR sequential extraction methods considered the characteristics of soil samples. Although Toxicity Characteristic Leaching Procedure (TCLP) used two different extraction regent is based on the pH values of soil samples, it is a single step extraction method. In this paper, compared with Tessier, BCR and TCLP extraction techniques, the speciation extraction method was optimized in order to adapt soils with different pH values. The heavy metals in the soils were divided into active fraction, secondary carbonate fraction, secondary steady fraction and steady fraction. The results show that the optimized sequential extraction method is more stable, the recovery rate is 85% to 115% which could satisfy the soil speciation evaluation requirements. And the optimized sequential extraction method is suitable for soils with different pH values.

Research Status and Prospect of Loess Collapsibility Mechanism

XIE Wan-li, WANG Yan-shou, MA Zhong-hao, GE Rui-hua, WANG Jia-ding

2015, 29(2):  397-407. 

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This paper summarizes the development of the loess collapsibility mechanism on the basis of memorizing the early results, discusses the research status of loess collapsibility mechanism from the aspect of microscopic structure, mathematical analysis methods, soil mechanics and constitutive model, and provides some problems in current growth of the loess collapsibility mechanism research combining the project instance and outlines the development trend of the research. A viewpoint is constructed that the research of loess collapsibility mechanism should be improved by constructing the constitutive relation of loess collapsibility under various stress paths from the aspect of unsaturated soil mechanics using discrete element analysis and considering the soluble salt, combining the advanced instruments and analysis software on the basis of the study of losses microstructure. It has an significant theory and introduction meaning to understand the loess collapsibility mechanism correctly and make a deep research.

Effect on Slope Stability due to Groundwater Rising Caused by Irrigation: A Case Study of Heifang Platform in Gansu, China

GU Tian-feng, ZHU Li-feng, HU Wei, WANG Jia-ding, LIU Ya-ming, FENG Li

2015, 29(2):  408-413. 

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Irrigation-induced loess landslides are common geological disasters in the Loess Plateau region, and its essence is the groundwater rising which caused loess matric suction falling and intensity decreasing, eventually leading to the instability process of loess slope. In this paper, taking Heifang platform typical slope for example, we studied the variation of seepage field internal the loess slope which caused by the groundwater level rising, and investigated the affect that the groundwater level changes on slope stability, which both based on the characteristics test of unsaturated soil and the saturated-unsaturated seepage analysis. The results show that the groundwater level rises which has an obvious effect on pore pressure distribution internal slope and results in the saturation region increasing and matric suction reducing in unsaturated zone. There is a linear relationship between decreasing of matric suction internal slope and groundwater level. We made unsaturated limit equilibrium analysis in the typical slope, based on seepage analysis. The results show that there is approximate linear relationship between groundwater level rising and stability coefficient decreasing. Slope instability occurs, while groundwater level in loess layer of about 21 m, 100 m from the top of the hill.

Index System of Risk Assessment on Karst Tunnel Water Inrush  Disasters and Value of Quantitative Method

YANG Yan-na, CAO Hua-ping, XU Mo

2015, 29(2):  414-420. 

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Water bursting hazard had taken a significant safety challenge to the deep buried tunnel engineering in the karst area of southwest China，and its prediction and risk assessment were still at the exploratory research stage. It was put forward that the most important issue in prevention and control of water inrush disasters was how to improve the accuracy of prediction and forecast in advance in deep buried tunnel construction.Based on the study of statistics and disaster formation conditions and control factors, five evaluation factors were selected, which were soluble rocks, geological structure condition and the surface catchment condition, the strength of groundwater cycles, the relationship between embedded depth of tunnel and underground water level. The index system of risk assessment on karst tunnel water inrush disasters was established, and quantitative methods of the evaluation indexes were discussed and studied. The study had provided deep buried karst tunnel construction with scientific and effective advanced geological forecast methods.

Analysis on Variation Characteristics of Karst Groundwater Systems  under Tunnel Engineering Conditions in Southwest China

ZHANG Wan-ting, QI Ji-hong, XU Mo

2015, 29(2):  421-427. 

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The construction of tunnels have an impact on the intrinsic characteristics of karst groundwater system, such as the fall of the water table or the loss of surface springs. In this paper, the variation characteristics of karst groundwater system in southwest  China under tunnel engineering conditions is summarized and is divided into three categories according to the types(covered, uncovered and buried)of the aquifers, structural features, supply characteristics, the runoff ways of karst water and the engineering characteristics of tunnel construction. The paper also presents typical examples (Jinzhi river groundwater system)illustrating the analysis process that different tunnel plans produce different effects on karst groundwater system, and compares the results with available tunnel seepage volume. As a result, the study can be used as a reference for the geological disaster prevention of tunnel water-bursting.

Assessment Methods for Rock Mass Quality Classification in Tunnel  under High Water Pressure at Great Depth in Jinping Ⅱ Hydropower Station,Sichuan

JI Feng，ZHENG Luo-bing，ZHOU Chun-hong

2015, 29(2):  428-433. 

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Jinping Ⅱ hydropower station, located in Yalong river, will generate electricity by employing low gate interception and long-distance diversion,with tunnel length of 17 km, the maximum depth of 2,525 m, the maximum geostress of 70 MPa and water pressure of 10.2 MPa. Therefore, the surrounding rock classification methods are beyond the present specification standard. Based on the engineering geological background,the key factors influencing the rock classification are extracted,including rock strength,rock structure,integrity,geostress, and high water pressure. Then, in combination with the field statistical data, a rapid assessment method is established for Jinping Ⅱ hydropower station under the high geostress and high water pressure. Field application shows that its prediction accuracy is more than 88%,which can provide a reliable basis for the further reinforcement of tunnel geological disasters.

Experimental Study on Testing the Antipermeability Strength of Clay Seepage Failure：A Case from the Engineering Field of  Tieshan Industrial Park in Guilin, China

JIANG Fu-wei,LEI Ming-tang,QIN You-qiang,DAI Jian-ling

2015, 29(2):  434-441. 

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A lot of geological hazards and geotechnical engineering failure cases including slope, dam, construct foundation, et al, are caused by soil seepage deformation. However, it is seldom to study the critical condition of clay seepage failure. This paper represents the microprocess of clay failure caused by additional driving pressure, and takes the antipermeability strength as the critical condition for judging clay seepage failure. Firstly, the equipment and method which stimulate the process of clay failure were designed to test the strength. Secondly, 32 undisturbed samples of clay were tested with different thickness, which are from the engineering field of Tieshan industrial park in Guilin, China. With the testing values of 32 samples, it is concluded that the two factors of seepage ways and sample size influence the anti-permeability strength, and the test results are made by statistical analysis of ArcGis. The average value of 15 samples of 2.5 cm thicknesses, 40.8 kPa, is the anti-permeability strength of the engineering field. Finally, by comparing the strength with the seepage water pressure in field, the probability of clay seepage failure to form soil-cave collapse is assessed. Results indicate that there is a low susceptibility to the formation of subsidence sinkholes under current conditions, as the seepage water pressure is less than the anti-permeability strength in field. By the field investigation, the assessment result is consistent with the truth.

Characteristics of Yungang Grottoes Sandstone and Weathering Simulation Tests

YAN Shao-jun, CHEN Jia-qi, DOU Yan, SUN Peng

2015, 29(2):  442-447. 

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The relics carrier of Yungang Grottoes is a huge sandstone lens deposited by river in Jurassic period and the sandstones are weathering rapidly and seriously in present conditions. Based on the field investigation, there are close connections between the damages with the deposition surrounding and structure of every subdivide layer. Furthermore, a standard has been presented for evaluating the weathering degree depended on tests of rock samples to different deteriorated degrees. It has been shown from the tests of the sandstones that the erosion of the cements and alteration of feldspar are the main chemical weathering reasons and the mechanical weathering, crystallization of the secondary salts and cycle of freeze and thaws should be paid attention to. Conclusions have been drawn from the weathering simulation tests that an inside to outside damage can be induced by the secondary soluble salts which come from the erosion of the acid on the grottoes rock surface directly and that the resistance for freeze-thaw cycle of the sandstone is good because of very low porosity, permeability and strong cementation. The suggestions has been presented for the relics protection that water controls such as the decrease of the surface flow on the cliff, the seepage from fracture inside caves and capillary water from the clay base of cliff are major ways to alleviate the weathering.

Characteristics and Disaster Causes of Wulipo Landslide in Dujiangyan City

WEN Ming-sheng, FANG Zhi-wei, WANG Yang-gu

2015, 29(2):  448-453. 

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The persistent heavy rain triggered Wulipo landslides in Sanxi Village, Dujiangyan, Sichuan Province in July 10, 2013. The features of landslide include big difference of elevation, fast speed of sliding, long run-out distance, large volume, heavy casualties and so on. Landslide overall shows an inverted “J” shape; and it can be divided into the upper slide source region, central slipstream and lower accumulation area. The upper stratum of landslide is Cretaceous Guankou Formation red siltstone and mudstone; the lower is massive conglomerate including mudstone weak surface; the landslide’s ramp structure is forward slope. Fragile geological environment including terrain steep ness, rock crushing, earthquake, with human engineering activities and continued heavy rainfall together, led to the major geological disasters; continuous 48 h of 544 mm rainfall is the direct cause of Wulipo landslide. The disaster mode is earthquake crack→bedrock collapse and slide→loading and instability→slipstream and pushing→accumulation and stopped-flow.

Study on Risk Assessment of Debris Flow Based on Factor-Clustering  Analysis：A Case Study from Beibei District in Chongqing

WANG Bin, CHEN Lin-ce, ZHAO Pei-zhe

2015, 29(2):  454-460. 

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Beibei district in Chongqing City is the primary area where debris flow hazard always occurred, and the outbreaks of debris flows are controlled by the rainfall, material source conditions, geographical conditions，geological structure, valley characteristics, vegetation and other internal or external factors. In this paper, in order to evaluate effectively the outbreak risk of debris flows in Beibei district, according to many factors of debris flows outbreak, and based on the method of factor analysis，massive data of 30 typical debris flows was analyzed, and the three main factors of debris flow were classified, which contains topography and material source conditions, vegetation coverage, maximum rainfall. And then, the clustering analysis about main factors score was carried out by the fast clustering method. Meanwhile, the outbreaks danger degree of debris flow hazard was determined. The evaluation results were consistent with the actual occurrence of these debris flows in Beibei district of Chongqing City, which show that one debris flow is extremely risk, three debris flows are high risk, twenty-one debris flows are moderate risk, and five debris flows are low risk.

Evaluation of Underground Goaf Stability Based on T-S  Fuzzy Neural Network Model

ZHANG Lian-jie，WU Xiong，XIE Yong，WU Chen-liang

2015, 29(2):  461-465. 

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The stability of underground goaf is affected by many factors, especially the conditions of mining and geology. These factors always have different influences, and some of them are interconnected. The above features bring great difficulty to evaluate the ground collapse risk quantitatively. In order to appropriately evaluate the stability of underground goaf, the T-S fuzzy neural network model was introduced in this paper. According to the ground collapse information of Xishan mining area of Beijing, eight factors influencing the stability of underground goaf were selected as the evaluation indexes at first, and then the grading standards were also built up. These factors include the complexity of geological structure, the type of overburden layer, thickness of quaternary cover, the strength of overlying strata, the dip angle of coal seam, the ratio of mining depth and thickness, the depth of underground goaf and the number of underground goaf in space. Based on the training samples which were generated by means of linear interpolation algorithm, the T-S fuzzy neural network model was constructed. Finally eight new samples of Xishan mining area in Beijing were evaluated by the trained T-S fuzzy neural network model. The results were Ⅰ,Ⅱ,Ⅲ,Ⅱ,Ⅲ,Ⅱ,Ⅲ and Ⅱ, respectively. The results coincided with the actual situation. The study shows that it is feasible to evaluate the stability of underground goaf by using the T-S fuzzy neural network model.

Development and Trends of Foreign Urban Geological Work and Its Enlightenment to China

Lv Dun-yu, YU Chu, HOU Hong-bing, LIU Chang-li, ZHANG Yun

2015, 29(2):  466-473. 

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Urbanization is a common trend for all the countries in their development, and is a mark of human civilization and progress. The trend of urbanization in China is consistent with the total trend of the world. So it is of great significance to find out the work progress of urban geological work in foreign countries. In this paper, the definition, connotation, task and work content are summarized and expounded. Then the main urban geological work of foreign countries is reviewed and summarized, in order to provide reference of the related work. On this basis, the development trend of urban geology is analyzed from nine aspects, including theory research, information system, working depth, working focus, mechanism construction, and so on. Finally, combining with the present situation of geological work in our country, the focus, content, research level of urban geology in China are discussed in order to offer reference to urban geological work in China.

Formation Characteristics and Stability Assessment of Geological Hazards in Yajiang City, Sichuan Province

NI Hua-yong, WANG De-wei, CHEN Xu-yu, TANG Ye-qi

2015, 29(2):  474-480. 

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Based on RS interpretation and field surveying, both investigation and assessment on geological hazards in Yajiang city have been carried out. Four conclusions are drawn as follows. Seven geological hazards have been checked out in Yajiang city, including 1 debris flow, 3 landslides, 2 potential unstable slopes and 1 dangerous rockmass. The safety of residents from 83 families and operation of G318 national highway and Yajiang middle school are threatened by these geo-hazards. Stability assessment indicates that all geo-hazards are at unstable condition. Landslide and rock collapse consist of the main hazard source in Yajiang city. As far as the principle of geo-hazard prevention in Yajiang city, priority should be given to engineering control and professional monitoring measures. Finally, corresponding prevention suggestions were brought forward in detail for every geological hazard. The study can provide geological reference both for geo-hazard prevention and for the construction and development of Yajiang city.