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Junoy J Castellanos C Viéitez JM de la Huz MR Lastra M 《Marine pollution bulletin》2005,50(5):526-536
Eighteen sandy beaches were sampled along the 1659 km of the Galician coast (NW Spain) six months after the Prestige oil-spill to study the impact of the fuel and the clean-up activities on the macroinfauna community. A transect was extended at each beach, from above the drift line to below the swash line at five sampled levels; at each level six 0.05 m2 replicates were taken to a depth of 30 cm and sieved through a 1mm mesh, and the organisms collected and preserved. Results were compared with previous data obtained using the same procedures. The macroinfauna was numerically dominated by the amphipod Pontocrates arenarius, the isopod genus Eurydice, the polychaete Scolelepis squamata, and the amphipod Talitrus saltator. As a result of the Prestige oil-spill and the clean-up activities, beach populations were reduced, with Eurydice and S. squamata as the most affected taxa. 相似文献
3.
Annually large volumes of fresh water laden with sediment are washed down the Daintree River in North Queensland into the Great Barrier Reef lagoon. To investigate the effects of land runoff on bioerosion, samples of recently killed colonies of Porites were laid at 6 sites on a cross shelf transect from Snapper Island at the entrance to the river to Osprey Reef, approximately 328 km from the river mouth out in the Coral Sea. Rates and agents of bioerosion were determined over 4 years and inshore sites exhibited significantly lower rates of total bioerosion than the other sites. Offshore sites experienced high rates of bioerosion primarily due to grazing and internal bioerosion by macroborers such as sponges and bivalves was also important at some of these sites. Inshore sites were covered in heavy layers of silt which inhibited colonization and growth of microborers, primarily algae. This resulted in lower levels of grazing than at offshore sites. However the activity of macroborers (primarily sponges and bivalves) was often high at these sites. The macroboring communities differed between sites and over time and it is hypothesised that these site differences were due to different levels of terrestrial runoff. These results are compared with those from French Polynesia where contaminated terrestrial runoff greatly influenced rates and agents of bioerosion. However other factors such as overfishing may also play an important role in some locations. 相似文献
4.
The antifouling boosting agent Irgarol 1051 is a strong inhibitor of the photosystem II (PSII) with high efficiency/toxicity towards algae. However, because some phytoplankton species are more sensitive to Irgarol than others, its persistent release into the environment could result in adverse changes in the phytoplankton community structure at heavily impacted sites such as marinas. Continuous monitoring in the Florida Keys showed Irgarol concentrations of up to 635 ngL(-1) in the canal system leading to Key Largo Harbor Marina (KLH) with a sharp decrease in concentration at stations offshore from the mouth of the canal. Preliminary phytoplankton community assessments from surface water samples collected in KLH between February and August 2004 showed changes in several phytoplankton species in concordance with the increase of the herbicide concentrations. Typical responses include an increase in the abundance of eukaryotes and Cryptomonas sp. as Irgarol concentrations increase. 相似文献
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David C.W. Sanderson Paul Bishop Miriam Stark Sally Alexander Dan Penny 《Quaternary Geochronology》2007,2(1-4):322-329
Work to apply luminescence dating to archaeological sites in the Lower Mekong Delta has continued with a programme aimed at dating ancient canal sediments and brick monuments in the vicinity of ancient city of Angkor Borei. Following the successful application of OSL dating to the Paris 2 canal near Angkor Borei further fieldwork and analysis has been undertaken. The infill and substrate of the larger Paris 4 canal connecting Angkor Borei to Oc Eo, some 80 km to the south in Vietnam has been sampled and subjected to luminescence analysis. Field spectroscopy and underwater bleaching experiments were also conducted in the Baray and Angkor Borei in 2004. The results show that both illumination intensities and spectral distributions are severely altered by as little as 1.5 m of turbid water, and that OSL bleaching rates for both quartz and feldspars are reduced. Since quartz resetting is heavily dependant on the UV components in daylight, which have preferentially attenuated the effects of turbid water on OSL zeroing rates are especially marked. The new data from the Paris 4 canal, which has been dated by OSL to be between the first millenium BC and the late first millenium AD are significant to understanding the archaeological development of the Fu Nan state in the Lower Mekong Delta, and the sequence of development of the canal network linking inland agrarian sites and coastal trading centres. 相似文献
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《水文科学杂志》2013,58(5):1038-1050
Abstract Universal kriging is applied to the command area of a set of canal irrigation projects in north-western India to show its applicability for optimal contour mapping of groundwater levels. This command area faces the problem of a rising groundwater table and manifestation of waterlogging over the years at many places. With the use of measured elevations of the water table in September 1990 at 143 observation sites in an area of 4500 km2, an omni-directional experimental semivariogram was constructed. The concave upward shape of omni-directional experimental semivariogram indicated the non-stationarity of the data and so the need for universal kriging. Directional semivariograms were calculated to find out the direction along which there is least drift. This directional semivariogram was considered as the underlying semivariogram and various theoretical semivariogram models were fitted to it. The drift order was estimated from the cross-validation procedure. The model and drift order finally selected were used to estimate the groundwater levels and corresponding estimation variances at the nodes of a square grid of 2 km × 2 km, and to develop the corresponding contour map. 相似文献
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We evaluated the effects of fishway design and stream habitat on fish distribution and migrations within a 50 km section of the Enz River (108 km long, 16.7 m3 · s−1 mean annual discharge), a second order tributary of the Rhine River. On 12 different occasions between August 1994 and September 1995, we collected fish electrically upstream, downstream, and inside three different types of fish-passes: a concrete channel (site I), an artificial stream (site II), and a step and pool fishway (site III). During electrofishing, species identity and fish lengths were recorded separately for specific habitats or sections within the fishways, and traps were installed for 3–5 week long periods at the upstream outlets of the fishways. More than 3550 fish >5 cm and approximately 5800 young-of-year individuals of 28 species were captured. 772 fish marked by subcutaneous injection of alcian blue dye were released downstream of two fishways. Almost 1150 fish, including 5 marked individuals, were captured in the traps, providing direct evidence for migration through the fishway. The total number of species recorded decreased downstream from 21 at site I to 18 at site II, and 17 at site III. This shift in numbers and also in species composition between sites could be partially related to differences in the available habitat. There were pronounced changes in the abundance of most of the dominant species downstream and upstream of the fishway at site III, and, to a lesser degree at sites I and II, indicating species (and size) specific differences in the effectiveness of the three designs for fish passage. Furthermore, marked differences in relative fish abundance between downstream locations and inside the fishway itself, and in the relative numerical composition of the trap catch at sites I and II, clearly demonstrate that some species (Cottus gobio, Barbatula barbatula, Salmo trutta, Leuciscus cephalus) use these fishways as a habitat, whereas others (Phoxinus phoxinus, Gobio gobio) simply migrate through. Only inside the artificial stream did we find early life stages of seven species, suggesting that passage of the other fishways is restricted to older fish. Our results demonstrate that fishway design is crucial in providing continuous fish passage for all species and life-stages, and that a nature-like fishway is the most functional solution. 相似文献
8.
Maotian Li Zhongyuan Chen Daowei Yin Jing Chen Zhanghua Wang Qianli Sun 《地球表面变化过程与地形》2011,36(5):641-650
This paper examines the morphological development of the Yangtze River mouth, which has been diverting southeasterly (dextrally), according to historical (150 years) chart‐based digital evolution model and on‐site measured tidal flow data. We reveal a significantly narrowing of the northern river mouth branch from formerly >30 km wide to presently 10 km wide due to rapid siltation. Net siltation there, however, decreases gradually, which largely contrasts with the fact that the siltation has shifted to the southern river mouth area, as shown by many newly‐emerged estuarine islands, sandy shoals and bifurcated branches. Our data have further demonstrated that the ebb flow that dominates in the study area changes its direction gradually from east to southeast from the inner to outer river mouth area, and its duration is much longer than the flood flow in the inner river mouth area, but nearly equal at the river mouth area. Accordingly, the sediment transport pathway has been diverted from east to southeast. We examine whether the Coriolis Force could explain the dextral diversion of the ebb flow and the altered morphodynamical processes. Although too weak to strengthen the tidal flows, the Coriolis Force can drag the ebb flow southeasterly, and so influence sediment transport paths at the estuarine scale. The Coriolis Force is limited in the inner river mouth, but substantial at and in the outer river mouth area when gradually free of estuarine topographic constraints. The Coriolis Force causes an offset in propagation of in‐out flow directions at the river mouth area to form a slack water setting prone to estuarine siltation. Using the present approach also enables explanation of the morphological development of the Holocene Yangtze delta‐coast that extends to the southeast. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
9.
Federico Von Giovanoli André Lambert 《Aquatic Sciences - Research Across Boundaries》1985,47(2):159-178
Results obtained by means of an ultrasonic current meter in the plume of the Rhone river are summarized as follows:
- Currents of Rhone river water entering the lake were clearly discernible up to a distance of about 1 km from the river mouth. The interflow was observed at depth of 10 to 30 m.
- Interflow velocities decreased with increasing distance from the river mouth: from 40cm/s at a distance of 350 m to about 15 cm/s at 1 km.
- Short-term variations of current velocities and directions documented the highly turbulent nature of the interflow.
- The entering river water (inflow direction to the NNW) interfered with a persisting northeastward current of the lake water. At a distance of 1–2 km from the mouth the interflow gradually assumed the same direction, possibly due to deflection by Coriolis forces.
- Current velocities showed considerable variations within a time scale in the order of hours at the same measuring position. The reasons for these fluctuations remain unclear. Possible causes may be lateral oscillations of the entering river water or its deviation by river mouth bars during periods of reduced river discharge. Variations of the discharge alone cannot explain these current fluctuations.
10.
Long-term changes in cladoceran assemblages in the Danube floodplain area (Slovak–Hungarian stretch)
In this paper, the distribution of Cladocera species in the different sampling sites: the main channel/old river bed, parapotamal type side arms and plesiopotamal side arms, is described. The structure of cladoceran assemblages in the by-passed Danube section and in the adjacent floodplain water bodies has changed since the Gabčíkovo hydropower plant was put into operation. Great changes have been observed in the previous parapotamal side arm situated between river km 1840 and 1820, artificially fed with water from the head-race canal. The dominance of tychoplanktonic (benthic and phytophilous) species has increased, while the typical euplanktonic species have disappeared. Three characteristic groups of cladoceran assemblages were recorded when a different type of habitat was taken into consideration. Euplanktonic cladocerans prevailed on all sampling sites before damming. In periods after damming, littoral species, and later also a euplanktonic forms, dominated on the main channel sampling sites. In parapotamal and plesiopotamal side arms with rich littoral macrovegetation during periods after damming, phytophilous cladoceran species were the ones with the highest occurrence. The samplings from the first time period were rather homogenous. The samplings from the second and third period were more similar when considering the sample site than regarding the time period. In total, 64 cladoceran species were recorded in the course of 13 years (from 1991 to 2004). The increase in number of Cladocera species from 1991 to 2004 was significant. Chydorus sphaericus was found to be the most widely distributed species in the study area. The finding of Disparalona hamata is the first faunistic record from the central part of the Danubian watersheds. 相似文献
11.
Variation of stream temperature among mesoscale habitats within stream reaches: southern Appalachians 
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下载免费PDF全文 Stream mesoscale habitats have systematic topographic relationships to hyporheic flow patterns, which may create predictable temperature variation between mesoscale habitat types. We investigated whether systematic differences in temperature metrics occurred between mesoscale habitats within reaches of small streams tributary to the upper Little Tennessee River, southern Appalachians. Surface water temperature was recorded over three or four mid‐summer days in four mesoscale habitat types: riffle, main riffle, pool and alcove in 44 stream segments (sites). Temperature metrics were calculated for each mesoscale habitat relative to the mean value of the metric over the stream: Δ maximum temperature, Δ average maximum temperature and Δ maximum daily variation and also for each site: standard deviation of the maximum temperature and average diurnal variation (ADV). Sites were categorized as fully or partially forested. Pool tailouts had statistically significantly lower Δ maximum temperature and Δ average maximum temperature than riffle tailouts in partially forested sites, although differences were small. This was the opposite of what was expected in the presence of hyporheic exchange, indicating hyporheic exchange is not a dominant driver of mesoscale habitat temperatures at these sites. Temperature differences between mesoscale habitat units were small and unlikely to have ecological significance. We also evaluated relationships between stream temperature and riparian condition, watershed % impervious surfaces, watershed % non‐forested and elevation. ADV and standard deviation of the maximum temperature were significantly higher in partially forested sites, indicating that partially forested sites have greater temperature ranges and spatial variation of maximum temperatures. ADV decreased with elevation and increased with % impervious surfaces. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
12.
The 1679 Garnì earthquake was one ofthe most destructive seismic events inArmenia, and one of the most widelydocumented directly by Armenian sources,considering this is an area where historical documentation is, on the whole,rather scarce. Moreover, this earthquakeappears in the literature as the result ofvarious interpretative and research models,so there are contradictory assessments ofits impact and its parameters: itsmagnitude oscillated between 5.5 and 7, andepicentral intensity between VIII and Xdegree. Even its location varied by over40 km. This contribution aims to enhancethe acquired knowledge of this earthquakeby applying a methodology of analysis tothe available information that has alreadygiven positive results in historicalseismology in Europe. On the grounds of thenew sources and with a critical review ofpreviously known ones, the authors canprovide new and more accurate data on theearthquake, along with a detailed outlineof the characteristics of the buildingsaffected and the historical and demographicconditions under which the earthquakeoccurred. Moreover, the data has beensupplemented with a direct observationof the monuments still standing, thusrevealing some of the earthquake'spreviously unassessed damaging effects. Theauthors have clearly arranged the use ofdata pertaining to different typologies,maintaining the evidence of suchdiversities even in the evaluation of themacroseismic intensity. This methodologicalapproach has been adopted in order toevaluate the seismic effects in an areawith a low density of historicaldocumentation. As a result, the effects ofthis earthquake could be estimated at 34sites (of which 20 documented from coevalsources and 14 on the grounds of directobservations). For this event there isalso a good geological database regardingthe active fault of Garnì. Hence, thisstudy has also represented a test forcomparing the results of the historicalresearch with the known geological data. 相似文献
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１９９６年１１月９日长江口以东海域发生ＭＳ６．１地震,震前距震中２９０ｋｍ的湖州地倾斜台观测到中期异常和短临异常,距震中２４０ｋｍ的宁波地倾斜台也观测到短临异常．这里简单介绍了地倾斜异常的演化过程以及地震三要素的预测．震前我们进行了中短期预报,取得较好效果,但没有提交短临预报意见,这主要是由于短临异常出现较晚和台站资料报送不及时所致． 相似文献
15.
The measurements of variations in the total electron content of the Earth’s ionosphere along the GPS satellite signal propagation path are described. The signal parameters were measured at a network of receivers at three distant sites: Sura (Vasilsursk), Zelenodolsk, and Kazan. They are arranged along the geomagnetic latitude of the Sura Facility under short-wave radio irradiation of the ionosphere. One feature of the experiment is the crossing of a disturbed region by the radio path between a GPS satellite and Vasilsursk. This resulted from the angular sizes of the Sura array pattern; the radio paths between a GPS satellite and Zelenodolsk and a GPS satellite and Kazan did not cross. Variations in the total electron content of up to 0.15?0.3 TECU were revealed at all three sites during four experimental campaigns (March 2010, March 2013, May 2013, and November 2013). The lateral scale of an ionospheric disturbance stimulated by a high-power radio wave and the velocity of its west-to-east propagation along the geomagnetic latitude were 30–60 km and 270–350 m/s, respectively. A decrease in the total electron content (down to 0.55 TECU) was recorded along the Kazan–Zelenodolsk–Vasilsurks line, which is connected with the solar terminator transit; the lateral scale of the related ionospheric inhomogeneities was ~65–80 km. 相似文献
16.
密云水库东西库区的水质与浮游藻类分析 总被引：3，自引：1，他引：2
湖泊生态工程因其净化效果好、投资小、运行简单等优点,近十多年来在我国受到了广泛关注,并得到了越来越多的应用.本文介绍了云南洱海污染治理的工程技术之一--桃溪河口净化工程的设计思路.该工程基于暴雨径流输送污染物的特征,将水力工程、土石工程与生物工程有效结合,通过在桃溪河口建立溢流堰,将桃溪正常来水导截入由桃溪河口9个废弃鱼塘改造而成的净化池进行净化.工程运行的水质监测表明,该工程已发挥一定的净化效果,对TN的去除率达55.2%-86.9%,其中对NO3-N和NH4 -N的去除率都较高,对P的去除率达76.4%-88.2%,对悬浮物的去除率达29.4%-49.5%. 相似文献
17.
The strong ground motion produced by the 17 October, 1989 Loma Prieta earthquake in northern California was recorded at over 100 stations. Accelerograms were generated at sites with significantly different geology, including land fill and soft sedimentary soil sites. In this study, the attenuation characteristics of the peak vertical and horizontal ground accelerations are studied for freefield recording conditions within 100 km of the source by the application of a non-linear multi-regression procedure. Two sets of attenuation models for weighted and unweighted observations are compared with those reported by other investigators for this earthquake and for regional and worldwide data. The peak ground acceleration (PGA) observations for this earthquake exceed previous predictions of standard attenuation models, particularly beyond 30 km (approximately 60 percent at 50 km). Higher attenuation of the vertical component compared to the horizontal is confirmed. The regression considers site geology as an independent parameter. Soil sites display as much as 23 per cent amplification relative to rock sites for horizontal PGA and as much as 40 per cent for vertical PGA. Amplification of the ground motion at sites characterized by soft soil geology is examined by comparing the recorded PGA with the corresponding prediction at sites underlain by stiff soil. Eight of ten of the soft soil sites display significant amplification relative to stiff soil sites (as much as 300 per cent for horizontal and 200 per cent for vertical components). Particular attention is paid to the so-called anomalous observations at distances beyond 50 km. The anomalous observations between 50 and 80 km may be attributed to various factors such as geology, basic geometry, azimuthal dependence, source mechanism and normal scatter of observations. 相似文献
18.
M. R. Ghayamghamian 《Journal of Seismology》2007,11(1):39-57
The Changureh–Avaj earthquake (M = 6.4) occurred 220 km northwest of Tehran on June 22, 2002. According to the official report, 226 people were killed, 1300
injured and 33,000 houses were seriously damaged or collapsed. Two villages located in the near-fault region with a population
more than 200 people were completely destroyed. The damage survey was conducted within 30 km of the epicenter. During damage
investigation, an observable pattern of damage in toppled masonry and concrete block fences was recognized. The data of damaged
fences were documented and analyzed to study the effect of direction and distance from the epicenter. From the 109 fences,
85 fences were built within 15° of either north or east, providing an opportunity to study the effect of orientation. The
results of analysis revealed that the east–west oriented fences toppled 2.6 times more than those oriented north–south. More
than 70% of toppled fences were oriented in east–west direction, with more falling towards the north than to the south. This
preferred direction of damage for toppled fences was observed in all four quadrants about the epicenter and at distance up
to 15 km. In the northern quadrants almost all toppled fences were oriented east–west. Two possibilities, namely, near-fault
effect and 2D or 3D site response, are examined to find an explanation for the observed damage pattern at the sites. Since
the preferred direction of damage inferred from toppled fences within 15 km of epicenter was found to be parallel to the direction
of rupture propagation, the near-fault forwarded rupture directivity was investigated as the most possible reason for the
observed phenomenon at the sites. However, there were no records of strong motions available in near-fault zone. Thus, the
near-fault ground motions were theoretically simulated by using developed local source parameters and heterogeneous slip model.
Next, the principal axes were calculated by using eigenvector analysis of simulated horizontal motions. The preferred direction
of damage in over 90% of the sites is well predicted by the directional dependence of near-fault ground motion. Nevertheless,
the preferred direction of damage in Avaj station, where the main shock was recorded, demonstrates totally different result
from the one predicted by the source. The shear-wave polarization is investigated as an alternative reason at the sites. The
polarization of motion is found to be the greatest at frequencies with peaks in maximized and H/V spectra, suggesting that
directional motion is associated with local site and geologic conditions. The dominant direction of motion due to source mechanism
and local site conditions was identified and compared with the preferred direction of damage observed at the sites. It is
found that the near-fault source effects can strongly control the motion directionality and even dictate its dominant direction
to the one caused by local geologic or site conditions. Finally, the outcome provides field evidence of directional damage
due to near-fault effects and local site conditions. This may aid in predicting the directions of damaging earthquake motions,
and serve as an important factor in the design of critical facilities. 相似文献
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《Limnologica》2015
The freshwater pearl mussel (Margaritifera margaritifera) is declining throughout its entire range. On the river Rede, North-East England, the population has been equally declining and shows no apparent recruitment. The study presented here aimed at characterizing water quality and habitat conditions for pearl mussels to identify possible indicators of pressures on the population and inform a restoration and conservation strategy. Water quality monitoring revealed levels of turbidity and suspended sediments to be above the limit set for functional pearl mussel rivers. Substrate sampling revealed silt was present at all sites. A loss of redox potential between the water column and the substrate occurred at all sites, indicating non suitable conditions for juvenile pearl mussels. These investigations suggest that fine sediment input in the river could be one of the factors preventing the development and survival of juvenile mussels while adults face water quality largely affected by high turbidity and high phosphate load. Restoration strategy for the Rede pearl mussel population should focus mainly on limiting sediment and nutrient input in the river throughout the catchment in order to improve habitat for juvenile pearl mussels. This work highlights the need for a catchment-based approach in order to succeed in the conservation of a fragile species. 相似文献