Environmental isotopes as indicators for ground water recharge to fractured granite

To assess the contribution of accumulated winter precipitation and glacial meltwater to the recharge of deep ground water flow systems in fracture crystalline rocks, measurements of environmental isotope ratios, hydrochemical composition, and in situ parameters of ground water were performed in a deep tunnel. The measurements demonstrate the significance of these ground water recharge components for deep ground water flow systems in fractured granites of a high alpine catchment in the Central Alps, Switzerland. Hydrochemical and in situ parameters, as well as delta(18)O in ground water samples collected in the tunnel, show only small temporal variations. The precipitation record of delta(18)O shows seasonal variations of approximately 14% and a decrease of 0.23% +/- 0.03% per 100 m elevation gain. delta(2)H and delta(18)O in precipitation are well correlated and plot close to the meteoric water line, as well as delta(2)H and delta(18)O in ground water samples, reflecting the meteoric origin of the latter. The depletion of 18O in ground water compared to 18O content in precipitation during the ground water recharge period indicates significant contributions from accumulated depleted winter precipitation to ground water recharge. The hydrochemical composition of the encountered ground water, Na-Ca-HCO3-SO4(-F), reflects an evolution of the ground water along the flowpath through the granite body. Observed tritium concentrations in ground water range from 2.6 to 16.6 TU, with the lowest values associated with a local negative temperature anomaly and anomalous depleted 18O in ground water. This demonstrates the effect of local ground water recharge from meltwater of submodern glacial ice. Such localized recharge from glaciated areas occurs along preferential flowpaths within the granite body that are mainly controlled by observed hydraulic active shear fractures and cataclastic faults.     

Effects of oil spill on seawater infiltration and macrobenthic community in tidal flats

Tidal flat ecosystem simulators are used to clarify the effects of stranded fuel oil on tidal flat ecosystems. Results show that oil spills increase the periphyton on sediment by decreasing the predation stress caused by deposit feeders. About a month after an oil spill, the total population density of the macrobenthos recovered. The oxidation-reduction potential in the surface sediment drops to a negative value after the oil spill, and the anaerobic condition throughout the sediment seems to be responsible for the decrease in the population density of the macrobenthos. The infiltration volume of seawater into the oil-stranded sediment decreases to a third of that without the oil spill. The recovery of infiltration volume after about a month coincides with the recovery of the population density of the macrobenthos. This result suggests that the macrobenthic population is highly dependent on the infiltration of seawater.     

青藏高原东部及周边现时地壳运动

通过1991—2001年期间在青藏高原东部及周边地区的GPS测量,获得该地区不同参考框架下的地壳运动速度场,其测量的速度精度高于2mm／yr。印度板块与华北地块之间的地壳形变分为喜马拉雅及高原南部、高原中部(拉萨—格尔木)和高原北部(格尔木—金塔)三部分,它们分别吸收了印度板块与欧亚板块汇聚速率的43％、24％和32％。在欧亚框架下和相对于成都,印度板块和华南地块之间存在着以东喜马拉雅构造结为轴心的顺时针巨型涡旋构造——滇藏涡旋构造,运动速度分别为26～6mm／yr和24～7mm／yr,总体上从北东方向转变为南东和南西方向,有别于青藏高原中部的北东方向。滇藏涡旋和东喜马拉雅构造结的形成与南迦巴瓦—阿萨姆“犄角”的楔入作用有关。     

Localization of saturated karst aquifer with magnetic resonance sounding and resistivity imagery

To answer one of the main questions of hydrogeologists implementing boreholes or working on pollution questions in a karst environment--i.e., where is the ground water?--numerous tools including geophysics are used. However, the contribution of geophysics differs from one method to the other. The magnetic resonance sounding (MRS) method has the advantage of direct detection of ground water over other geophysical methods. Eight MRSs were implemented over a known karst conduit explored and mapped by speleologists to estimate the MRS ability to localize ground water. Two direct current resistivity imageries (DC-2D imagery) were also implemented to check their capability to map a known cave. We found that the MRS is a useful tool to locate ground water in karst as soon as the quantity of water is enough to be detected. The threshold quantity is a function of depth and it was estimated by forward modeling to propose a support graph to hydrogeologists. The measured MRS's signals could be used to calculate transmissivity and permeability estimators. These estimators were used to map and to draw a cross section of the case study site, which underline accurately the known karst conduit location and depth. We also found that the DC-2D imagery could underline the karst structures: It was able to detect the known cave through its associated faults. We prepared a computer simulation to check the depth of such a cave to induce resistivity anomaly which could be measured in similar conditions.     

Application of enterococci antibiotic resistance patterns for contamination source identification at Huntington Beach,California

Huntington Beach, California, one of the most popular surfing spots in the world, is plagued by sporadic, elevated levels of fecal bacteria. To assist with pollution source identification, we analyzed antibiotic resistance patterns (ARPs) of enterococci from four known sources (bird feces, urban runoff, coastal marsh sediment and sewage effluent from local sanitation district) and one unknown source (seawater) using seven antibiotics at four concentrations each. Of 2491 enterococci tested, all were resistant to at least one antibiotic at some level. Discriminant analysis indicated that the average correct classification rates for bird feces and urban runoff sources were above 80%. Sewage effluent contained mixed fecal sources. Sixty-four percent of the sewage isolates classified with the sewage category, while the other 35% of isolates were assigned evenly across the other three categories. When enterococci isolated from the seawater were classified using the known ARP database, it was evident that bird feces were the source of surf zone contamination on some days while the coastal salt marsh and sewage plume may have impacted the surf zone water quality to various degrees during other times.     

Anti-plane deformations around arbitrary-shaped canyons on a wedge-shape half-space: moment method solutions

The wave propagation behavior in an elastic wedge-shaped medium with an arbitrary shaped cylindrical canyon at its vertex has been studied. Nunerical computation of the wave displacement field is carried out on and near the canyon surfaces using weighted-residuals (moment method). The wave displacement fields are computed by the residual mcthod for the cases of elliptic, circular, rounded-rectangular and flat-elliptic canyons. The analysis demonstrates that thc resulting surface displacemcnt depends, as in similar previous analyses, on several factors including, but not limited, to the angle of thc wedge, thc geometry of thc vertex, the frcquencies of thc incident waves, the angles of incidence, and the material properties of the media. The analysis provides intriguing results that help to explain geophysical observations regarding the amplification of seismic energy as a function of site conditions.     

A series solution for surface motion amplification due to underground twin tunnels: incident SV waves

A series solution of displacement response of the ground surface in the presence of underground twin tunnels subjectcd to excitation of incident plane SV waves is derived by using Fourier-Bessel series expansion method. The numerical parametric study shows that underground twin tunnels significantly amplify the nearby surface ground motion. It is suggested that the effect of subways on ground motion should be considered when the subways are planned and designed.     

地下开采块状硫化物矿的一种简化经济滤波器

隐伏矿产资源评价和勘查早期，以及计划阶段，需要建立预可行成本模式。勘查过程中，区分经济与非经济矿床的这些成本模式有助于勘查企业集中在能获益的靶区勘查。资源评价过程中，这些模式用来排除那些即便发现但没有经济价值的矿床。美国矿业局（USBM）先前建立的简化成本模式就是为了解决这一问题的（Camm，1991）。这些成本模式采用矿床储量、品位和埋深参数评估运行成本和固定成本，也是USBM预可行分析软件的一部分（Smith，1991）。     

ASTER遥感影像数据在土壤盐渍化评价中的应用

本文通过运用ASTER遥感影像数据，对不同地物进行光谱分析，根据不同地物在不同波段的光谱特征曲线，分别提取植被和水体信息，然后进行非监督分类。并结合物探试验和土样分析结果，进行聚类分析，定性和定量的评价了焉耆盆地内土壤盐渍化程度分布状况。评价结果为：在焉耆盆地的平原区内，非盐渍化土壤，457．65km^2；轻度盐渍化土壤，335．61km^2；中度-重度盐渍化土壤，580．93km^2；盐土，41．11km^2。根据野外实际调查，评价结果的精度达到了85％以上。