Laboratory Characterization of Permeability and Its Anisotropy of Chelungpu Fault Rocks

In Taiwan an international project to drill into the Chelungpu fault (TCDP) was initiated after the M _w 7.6 Chi-Chi earthquake in 1999. At Takeng, two vertical holes (A and B) to depths of about 2 km have been drilled through the northern portion of the Chelungpu fault system. In this study, we conducted systematic hydromechanical tests on TCDP drillcores collected from Hole-A at various depths above and below the major slip zone of the Chelungpu fault. We focus on the measurements of permeability as function of pressure and the brittle failure behavior. Evolution of permeability as a function of pressure and porosity was measured using either steady-state flow or a pulse transient technique. When subjected to an effective pressure reaching 100 MPa, permeability values of shaly siltstone samples range from 10^?16 to 10^?19 m². In comparison, permeability values of porous sandstones are at least an order of magnitude higher, ranging from 10^?14 to 10^?18 m². To characterize permeability anisotropy associated with the bedding structure of the rocks of the Chelungpu fault, cylindrical samples were taken from the TCDP drillcores along three orthogonal directions, denoted X, Y and Z respectively. Direction Z is parallel to the TCDP core axis, and the other two directions are perpendicular to the core axis, with X (N105°E) perpendicular and Y (N15°E) parallel to the strike of the bedding. In shaly siltstones, permeability values of samples cored along the strike of bedding (direction Y) can be up to 1 order of magnitude higher than those cored perpendicular to the strike of bedding (direction X). These observations indicate that permeability anisotropy is controlled by the spatial distribution of bedding in Chelungpu fault host rocks. Permeability evolution of fault rocks plays an important role in dynamic weakening processes, which are particularly pertinent to large earthquakes such as the Chi-Chi earthquake. Our experimental data on permeability and its anisotropy of TCDP core samples provide necessary constraints on fault models and proposed weakening mechanisms.     

Potential use of mangroves as constructed wetland for municipal sewage treatment in Futian, Shenzhen, China

A pilot-scale mangrove wetland was constructed in Futian, Shenzhen for municipal sewage treatment. Three identical belts (length: 33m, width: 3m, depth: 0.5m) were filled with stone (bottom), gravel and mangrove sand (surface). Seedlings of two native mangrove species (Kandelia candel, Aegiceras corniculatum) and one exotic species (Sonneratia caseolaris) were transplanted to the belts with one species for each belt. The hydraulic loading was 5m(3)d(-1) and hydraulic retention time 3d. High levels of removal of COD, BOD(5), TN, TP and NH(3)-N were obtained. The treatment efficiency of S. caseolaris and A. corniculatum was higher than that of K. candel. Faster plant growth was obtained for S. caseolaris. The substrate in the S. caseolaris belt also showed higher enzyme activities including dehydrogenase, cellulase, phosphatase, urease and beta-glucosidase. The removal rates of organic matter and nutrients were positively correlated with plant growth. The results indicated that mangroves could be used in a constructed wetland for municipal sewage treatment, providing post-treatment to remove coliforms was also included.     

Effectiveness of bacterial inoculum and mangrove plants on remediation of sediment contaminated with polycyclic aromatic hydrocarbons

The remediation of mangrove sediment contaminated with mixed polycyclic aromatic hydrocarbons (PAHs) having 3-, 4- and 5-rings by natural attenuation, bioaugmentation, phytoremediation and its combination was compared by greenhouse microcosm studies. At Days 90 and 154, the decreases of PAHs in contaminated mangrove sediment by phytoremediation, planted with one-year old Aegiceras corniculatum, and bioaugmentation, the inoculation of PAH-degrading bacterial strains isolated from mangrove sediment, either SCSH (Mycobacterium parafortuitum) or SAFY (Sphingobium yanoikuyae), were not better than that by natural attenuation (the non-vegetated and un-inoculated microcosms). The populations of SCSH and SAFY in sediment could not be maintained even with repeated inoculation, suggesting that the two isolates were not able to compete with the indigenous microbes and had little enhancement effect. Although some PAHs were accumulated in roots, root uptake only accounted for <15% of the spiked PAHs and the effect of plants on remediation were also insignificant. At the end of the 154-day experiment, the mass balance calculation revealed that the overall losses of PAHs by phytoremediation were comparable to that by bioaugmentation but were lower than that by natural attenuation, especially for the high molecular weight PAHs. Under natural attenuation, around 90% fluorene, 80% phenanthrene, 70% fluoranthene, 68% pyrene and 32% benzo[a]pyrene in contaminated sediment were removed. These results demonstrated that the mangrove sediment itself had sufficient indigenous microorganisms capable of naturally remedying PAH contamination.     

Partitioning behavior of perfluorinated compounds between sediment and biota in the Pearl River Delta of South China

Surface sediment and biota were collected from 12 sampling sites – seven along the Pearl River Delta and five along the Hong Kong coastline. Perfluorinated compound (PFC) concentrations were detected using a high-performance-liquid-chromatogram–tandem-mass-spectrometry system. Analytical results indicated that the total PFC concentrations were in the range of 0.15–3.11 ng/g dry weight in sediments, while the total PFC concentrations in oyster and mussel samples were between 0.46–1.96 and 0.66–3.43 ng/g wet weight, respectively. The major types of PFCs detected in the sediment samples were perfluorooctanesulfonic acid (PFOS) and perfluorobutanoic acid (PFBA), with concentrations ranging from low limits of quantification to 0.86 ± 0.12 ng/g dry weight and 1.50 ± 0.26 ng/g dry weight, respectively. In bivalve samples, PFOS was the dominant contaminant with concentrations ranging from 0.25 ± 0.09 to 0.83 ± 0.12 ng/g wet weight in oysters and 0.41 ± 0.14 to 1.47 ± 0.25 ng/g wet weight in mussels. An increase in PFC concentration was found to be correlated with increased human population density in the study areas.     

Simulation of groundwater drainage into a tunnel in fractured rock and numerical analysis of leakage remediation, Romeriksporten tunnel, Norway

Standard geostatistical methods for simulation of heterogeneity were applied to the Romeriksporten tunnel in Norway, where water was leaking through high-permeable fracture zones into the tunnel while it was under construction, causing drainage problems on the surface. After the tunnel was completed, artificial infiltration of water into wells drilled from the tunnel was implemented to control the leakage. Synthetic heterogeneity was generated at a scale sufficiently small to simulate the effects of remedial actions that were proposed to control the leakage. The flow field depends on the variance of permeabilities and the covariance model used to generate the heterogeneity. Flow channeling is the most important flow mechanism if the variance of the permeability field is large compared to the expected value. This condition makes the tunnel leakage difficult to control. The main effects of permeability changes due to sealing injection are simulated by a simple perturbation of the log-normal probability density function of the permeability. If flow channeling is the major transport mechanism of water into the tunnel, implementation of artificial infiltration of water to control the leakage requires previous chemical-sealing injection to be successful. Electronic Publication     

Floods on Mars released from groundwater by impact

On Earth, large earthquakes commonly cause saturated soils to liquefy and streamflow to increase. We suggest that meteoritic impacts on Mars may have repeatedly caused similar liquefaction to enable violent eruption of groundwater. The amount of erupted water may be comparable to that required to produce catastrophic floods and to form outflow channels.     

海洋微生物对甲胺磷农药的降解作用

作者从沿岸海域分离了38株有机磷农药的耐药菌,用分批培养法进行富集培养,得到有机磷农药的降解菌,并着重研究了其中两株菌对甲胺磷农药的降解情况,其结果表明,在10d内,降解菌株1对甲胺磷的降解率为59．1％,降解菌株2的降解率为53．3％,在各自的安磷培养液中,降解菌株1的数量大于降解菌株2;在甲胺降解过程中,其毒性逐渐减弱,降解菌株1所引起的毒性下降幅度大于降解菌株2。     

Combined effects of land reclamation,channel dredging upon the bioavailable concentration of polycyclic aromatic hydrocarbons (PAHs) in Victoria Harbour sediment,Hong Kong

The up-to-date concentration of polycyclic aromatic hydrocarbons (PAHs) in sediment materials of Victoria Harbour was investigated so as to evaluate the pollution potential associated with the reclamation projects in Hong Kong. A total of 100 sediment samples were collected at 20 locations. Except the control point in reservoir, the PAHs concentrations were detectable levels all sites (131–628.3 ng/g, dw) and such values were higher than Dutch Target and Intervention Values (the New Dutch standard in 2016). The PAHs concentration indicating that construction waste and wastewater discharges were the main pollutant sources. Results of correlation in single cell gel electrophoresis assay (comet assay) studies also revealed that the PAHs concentration was highly correlated (< 0.01) with DNA migration (i.e. the length of tail moment of fish cells) in 5 mg/ml of PAHs. The above observation indicates that the PAHs present in the sediment may substantially effect the marine ecosystem. Although the dredged sediment can be a useful sea-filling material for land reclamation; however, the continuing leaching of PAHs and its impact on the aquatic environment need to be studied further.     

Distribution and origin of sediments on the northern Sunda Shelf, South China Sea

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