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Water quality and presence of pesticides in a tropical coastal wetland in southern Mexico 总被引：6，自引：0，他引：6
Hernández-Romero AH Tovilla-Hernández C Malo EA Bello-Mendoza R 《Marine pollution bulletin》2004,48(11-12):1130-1141
The water quality of the Pozuelos-Murillo lagoon system in southern Mexico was evaluated during three periods between March and October 2002, with particular emphasis on the detection of organochlorine and organophosphorous pesticide residues in water and sediments. Physicochemical and microbiological parameters of water were also measured and integrated in a water quality index (WQI). Multivariate analysis was used to regionalise the lagoon system as a function of the behaviour of all measured parameters. Solid phase micro-extraction followed by gas chromatography (SPME-GC) was used for pesticide analysis. The concentration of phosphorous was found to be higher than that of nitrogenous compounds. This, besides a deficiency in dissolved oxygen and a high organic matter concentration (as COD), reflects eutrophication processes in some areas of the system. Measured levels of faecal coliforms and oils and greases were above the limits established by Mexican law and comparable to the concentrations reported for other highly polluted systems in Mexico. Residues of DDD (2.0 microg L(-1)) in water and DDE (247 ng g(-1)) and endosulfan I (814 ng g(-1)) sediments were detected by SPME-GC. The spatial distribution of these contaminants implies major potential risks because the most polluted sites were found to be those with the highest fishing activity. Although in general the WQI is on acceptable levels (65-80%), some contamination problems are evident. 相似文献
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A series of 112 earthquakes was recorded between October 2005 and August 2007 during the excavation of the MFS Faido, the southernmost access point of the new Gotthard Base Tunnel. Earthquakes were recorded at a dense network of 11 stations, including 2 stations in the tunnel. Local magnitudes computed from Wood?CAnderson-filtered horizontal component seismograms ranged from ?1.0 to 2.4; the largest earthquake was strongly felt at the surface and caused considerable damage in the tunnel. Hypocenter locations obtained routinely using a regional 3-D P-wave velocity model and a constant Vp/Vs ratio 1.71 were about 2?km below the tunnel. The use of seismic velocities calibrated from a shot in the tunnel revealed that routinely obtained hypocenter locations were systematically biased to greater depth and are now relocated to be on the tunnel level. Relocation of the shot using these calibrated velocities yields a location accuracy of 25?m in longitude, 70?m in latitude, and 250?m in focal depth. Double-difference relative relocations of two clusters with highly similar waveforms showed a NW?CSE striking trend that is consistent with the strike of mapped faults in the MFS Faido. Source dimensions computed using the quasidynamic model of Madariaga (Bull Seismo Soc Am 66(3):639?C666, 1976) range from 50 to 170?m. Overlapping source dimensions for earthquakes within the two main clusters suggests that the same fault patch was ruptured repeatedly. The observed seismicity was likely caused by stress redistribution due to the excavation work in the MFS Faido. 相似文献
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Following the Yogyakarta earthquake on May 27th, 2006, the subsequent eruption of a mud volcano has been closely observed and analyzed by the geological community. The mud volcano, known as LUSI, began erupting near the Banjarpanji-1 exploration well in Sidoarjo, East Java, Indonesia. LUSI offers a unique opportunity to study the genesis and development of a mud volcano. 相似文献
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Igor Bogunovic Darija Bilandzija Zeljko Andabaka Domagoj Stupic Jesús Rodrigo Comino Marija Cacic Luka Brezinscak Edi Maletic Paulo Pereira 《Arabian Journal of Geosciences》2017,10(15):340
The use of machinery in vineyards is increasing soil compaction and erosion. However, there is a lack of information about the impacts of different management practices on soil conditions of vineyards. Therefore, the aim of this study was to assess soil compaction in Croatian vineyards under four different management systems: no-tillage (NT) system, conventional tillage (CT), yearly inversed grass covered (INV-GC) and tillage managed (INV-T) treatments. Four key top-soil (0–20 cm) parameters were assessed in the different land uses: bulk density (BD), penetration resistance (PR), soil water content (SWC) and carbon dioxide (CO2) fluxes. Tractor traffic increased the BD and PR in all treatments, with exception of CT treatment, as consequence of tillage. SWC showed higher values in INV-GC treatment during the dry period; meanwhile, it was similar during the wet season in every management type. Lower CO2 fluxes were found in INV-GC and NT than in the CT and INV-T treatments. 相似文献
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Local and regional minimum 1D models for earthquake location and data quality assessment in complex tectonic regions: application to Switzerland 总被引：1，自引：0，他引：1
One-dimensional (1D) velocity models are still widely used for computing earthquake locations at seismological centers or
in regions where three-dimensional (3D) velocity models are not available due to the lack of data of sufficiently high quality.
The concept of the minimum 1D model with appropriate station corrections provides a framework to compute initial hypocenter
locations and seismic velocities for local earthquake tomography. Since a minimum 1D model represents a solution to the coupled
hypocenter-velocity problem it also represents a suitable velocity model for earthquake location and data quality assessment,
such as evaluating the consistency in assigning pre-defined weighting classes and average picking error. Nevertheless, the
use of a simple 1D velocity structure in combination with station delays raises the question of how appropriate the minimum
1D model concept is when applied to complex tectonic regions with significant three-dimensional (3D) variations in seismic
velocities. In this study we compute one regional minimum 1D model and three local minimum 1D models for selected subregions
of the Swiss Alpine region, which exhibits a strongly varying Moho topography. We compare the regional and local minimum 1D
models in terms of earthquake locations and data quality assessment to measure their performance. Our results show that the
local minimum 1D models provide more realistic hypocenter locations and better data fits than a single model for the Alpine
region. We attribute this to the fact that in a local minimum 1D model local and regional effects of the velocity structure
can be better separated. Consequently, in tectonically complex regions, minimum 1D models should be computed in sub-regions
defined by similar structure, if they are used for earthquake location and data quality assessment. 相似文献
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A series of 112 earthquakes was recorded between October 2005 and August 2007 during the excavation of the MFS Faido, the
southernmost access point of the new Gotthard Base Tunnel. Earthquakes were recorded at a dense network of 11 stations, including
2 stations in the tunnel. Local magnitudes computed from Wood–Anderson-filtered horizontal component seismograms ranged from
−1.0 to 2.4; the largest earthquake was strongly felt at the surface and caused considerable damage in the tunnel. Hypocenter
locations obtained routinely using a regional 3-D P-wave velocity model and a constant Vp/Vs ratio 1.71 were about 2 km below
the tunnel. The use of seismic velocities calibrated from a shot in the tunnel revealed that routinely obtained hypocenter
locations were systematically biased to greater depth and are now relocated to be on the tunnel level. Relocation of the shot
using these calibrated velocities yields a location accuracy of 25 m in longitude, 70 m in latitude, and 250 m in focal depth.
Double-difference relative relocations of two clusters with highly similar waveforms showed a NW–SE striking trend that is
consistent with the strike of mapped faults in the MFS Faido. Source dimensions computed using the quasidynamic model of Madariaga
(Bull Seismo Soc Am 66(3):639–666, 1976) range from 50 to 170 m. Overlapping source dimensions for earthquakes within the two main clusters suggests that the same
fault patch was ruptured repeatedly. The observed seismicity was likely caused by stress redistribution due to the excavation
work in the MFS Faido. 相似文献
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