Phase distribution of hydrocarbons in the water column after a pelagic deep ocean oil spill     

Saioa Elordui-Zapatarietxe  Núria Moraleda  Joan Albaigés 《Marine pollution bulletin》2010,60(10):1667-1673

Spills from wrecks are a potential major source of pollution in the deep ocean. However, not much is known about the fate of a spill at several kilometers depth, beyond the oceans continental shelves. Here, we report the phase distribution of hydrocarbons released from the wrecks of the Prestige tanker, several years after it sank in November 2002 to depths between 3500 and 3800 m. The released oil reached the surface waters above the wrecks without any signs of weathering and leaving an homogenous signature throughout the water column. At depths of several kilometers below the sea surface, the occurrence and spread of the deep sea oil spill could be evaluated better by quantifying and characterizing the dissolved hydrocarbon signature, rather than just the investigation of hydrocarbons in the suspended particulate matter.  相似文献   

Spatial distribution and content of soil organic matter in an agricultural field in eastern Canada,as estimated from geostatistical tools     

Lionel Mabit  Claude Bernard 《地球表面变化过程与地形》2010,35(3):278-283

Soil erosion induces soil redistribution within the landscape and thus contributes to the spatial variability of soil quality. This study complements a previous experimentation initiated by the authors focusing on soil redistribution as a result of soil erosion, as indicated by caesium‐137 (¹³⁷Cs) measurements, in a small agricultural field in Canada. The spatial variability of soil organic matter (SOM) was characterized using geostatistics, which consider the randomized and structured nature of spatial variables and the spatial distribution of the samples. The spatial correlation of SOM (in percentages) patterns in the topsoil was established taking into account the spatial structure present in the data. A significant autocorrelation and reliable variograms were found with a R² ≥ 0·9, thus demonstrating a strong spatial dependence. Ordinary Kriging (OK) interpolation provided the best cross validation (r² = 0·35). OK and inverse distance weighting power two (IDW2) interpolation approaches produced similar estimates of the total SOM content of the topsoil (0–20 cm) of the experimental field, i.e. 211 and 213 tonnes, respectively. However, the two approaches produced differences in the spatial distribution patterns and the relative magnitude of some SOM content classes. The spatialization of SOM and soil redistribution variability – as evidenced by ¹³⁷Cs measurements – is a first step towards the assessment of the impact of soil erosion on SOM losses to recommend conservation measures. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Distribution of petroleum hydrocarbons and organochlorinated contaminants in marine biota and coastal sediments from the ROPME Sea Area during 2005   总被引：3，自引：0，他引：3  

de Mora S  Tolosa I  Fowler SW  Villeneuve JP  Cassi R  Cattini C 《Marine pollution bulletin》2010,60(12):2323-2349

The composition and spatial distribution of various petroleum hydrocarbons (PHs), comprising both aliphatic and polycyclic aromatic hydrocarbons (PAHs), and selected chlorinated pesticides and PCBs were measured in biota and coastal sediments from seven countries in the Persian Gulf and the Gulf of Oman (Bahrain, Iran, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates). Evidence of extensive marine contamination with respect to organochlorinated compounds and PHs was not observed. Only one site, namely the BAPCO oil refinery in Bahrain, was considered to be chronically contaminated. Comparison of the results from this survey for Σ DDTs and Σ PCBs in rock oysters from the Gulf of Oman with similar measurements made at the same locations over the past two decades indicates a temporal trend of overall decreasing Σ PCB concentrations in oysters, whereas Σ DDTs levels have little changed during that period.  相似文献   

Paleoclimatic interpretation of the past 30 ka from isotopic studies of the deep confined aquifer of the North China plain     

《Applied Geochemistry》2003,18(7):997-1009

The δ¹⁸O and δD values in the deep confined aquifer beneath the North China Plain which is located at 112°30′E–119°30′E and 34°46′N–40°25′N, reflect differences in paleoclimatic conditions between the Holocene and the late Pleistocene. Groundwater samples whose ¹⁴C ages are between 12 and 25 ka B.P have ranges of −9.4 to −11.7‰ for δ¹⁸O and −76‰ to −85‰ for δD values. These very negative δ¹⁸O and δD values reflect the cold and arid climate in the last glacial period. The temperature estimated in this period is 6–9 °C cooler than that of the present. The entire ranges of δ¹⁸O and δD values for samples with ¹⁴C dating from 7 ka B.P to present are −7.7‰ to −10.2‰ and −63‰ to −73‰, respectively. The greater δ¹⁸O and δD enrichments of these samples indicate a period of relatively humid and warm climate in the Holocene. However, the wide ranges of δ¹⁸O (−9.0‰ to −11.1‰) and δD (−66‰ to −80‰) values for samples with ¹⁴C age ranging from 12 to 7 ka B.P. imply an unstable climatic condition of rapidly increasing temperature, which marks the transition from the Pleistocene to the Holocene.  相似文献   

Dynamic changes in hydrogeochemical conditions caused by tunnel excavation at the Aspo Hard Rock Laboratory (HRL), Sweden     

《Applied Geochemistry》2001,16(3):291-315

Hydraulic changes caused by tunneling at the Aspo Hard Rock Laboratory (HRL) in Sweden have been investigated over a period of 2a using different hydrochemical approaches, i.e. noble gas content, isotopic measurements and major ion concentrations. The dissolved noble gases (⁴He and Ne contents, and the ratio of ³He/⁴He, ⁴⁰Ar/³⁶Ar), stable isotopes, chemical concentrations of major ions, and ³⁶Cl/Cl ratios, were determined in groundwater samples collected in the tunnel from borehole sections isolated by inflated packers. Groundwater was categorized into 3 groups based on ⁴He and Cl⁻ contents: undisturbed groundwater (i.e. prior to tunnel construction) with high ⁴He and Cl⁻ contents, groundwater that has been gradually changed by mixing with Baltic seawater and whose ⁴He and Cl⁻ contents have gradually increased with increasing depth, and groundwater that has been totally changed due to a rapid mixing of Baltic seawater and/or shallow groundwater and whose ⁴He and Cl⁻ contents are extremely low compared with other samples collected at the same surrounding depth. The oldest groundwater with a high salinity of more than 14,000 mg l⁻¹ of Cl⁻ is estimated to be more than 1.8 Ma old. The groundwater residence time ranges from 0.9 to 900 Ka in the mixing-zone. Groundwater in the disturbed zone where rapid mixing has occurred is hard to date reliably and its primary hydrochemical character has already been lost.  相似文献   

Isotopic evidence for widespread cold‐season‐biased groundwater recharge and young streamflow across central Canada          下载免费PDF全文

Scott Jasechko  Leonard I. Wassenaar  Bernhard Mayer 《水文研究》2017,31(12):2196-2209

Transformations of precipitation into groundwater and streamflow are fundamental hydrological processes, critical to irrigated agriculture, hydroelectric power generation, and ecosystem health. Our understanding of the timing of groundwater recharge and streamflow generation remains incomplete, limiting our ability to predict fresh water, nutrient, and contaminant fluxes, especially in large basins. Here, we analyze thousands of rain, snow, groundwater, and streamflow δ¹⁸O and δ²H values in the Nelson River basin, which covers 1.2 million km² of central Canada. We show that the fraction of precipitation that recharges aquifers is ~1.3–5 times higher for precipitation falling during cold months with subzero mean monthly temperatures than for precipitation falling during warmer months. The near‐ubiquity of cold‐season‐biased groundwater recharge implies that changes to winter water balances may have disproportionate impacts on annual groundwater recharge rates. We also show that young streamflow—defined as precipitation that enters a river in less than ~2.3 months—comprises ~27% of annual streamflow but varies widely among tributaries in the Nelson River basin (1–59%). Young streamflow fractions are lower in steep catchments and higher in flatter catchments such as the transboundary Red River basin. Our findings imply that flat, lower permeability, heavily tiled landscapes favor more rapid transmission of precipitation into rivers, possibly mobilizing excess soluble fertilizers and exacerbating eutrophication events in Lake Winnipeg.  相似文献   

Impacts of ocean acidification on marine fauna and ecosystem processes   总被引：22，自引：1，他引：21  

Fabry  Victoria J.; Seibel  Brad A.; Feely  Richard A.; Orr  James C. 《ICES Journal of Marine Science》2008,65(3):414-432

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Time-series measurements of Th in water column and sediment trap samples from the northwestern Mediterranean Sea     

J. Kirk Cochran  Juan Carlos Miquel  Robert Armstrong  Scott W. Fowler  Pere Masqu  Beat Gasser  David Hirschberg  Jennifer Szlosek  Alessia M. Rodriguez y Baena  Elisabet Verdeny  Gillian M. Stewart 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(18):1487-1501

Disequilibrium between ²³⁴Th and ²³⁸U in water column profiles has been used to estimate the settling flux of Th (and, by proxy, of particulate organic carbon); yet potentially major non-steady-state influences on ²³⁴Th profiles are often not able to be considered in estimations of flux. We have compared temporal series of ²³⁴Th distributions in the upper water column at both coastal and deep-water sites in the northwestern Mediterranean Sea to coeval sediment trap records at the same sites. We have used sediment trap records of ²³⁴Th fluxes to predict temporal changes in water column ²³⁴Th deficits and have compared the predicted deficits to those measured to determine whether the time-evolution of the two coincide. At the coastal site (327 m water depth), trends in the two estimates of water column ²³⁴Th deficits are in fairly close agreement over the 1-month deployment during the spring bloom in 1999. In contrast, the pattern of water column ²³⁴Th deficits is poorly predicted by sediment trap records at the deep-water site (DYFAMED, 2300 m water depth) in both 2003 and 2005. In particular, the transition from a mesotrophic to an oligotrophic system, clearly seen in trap fluxes, is not evident in water column ²³⁴Th profiles, which show high-frequency variability. Allowing trapping efficiencies to vary from 100% does not reconcile the differences between trap and water column deficit observations; we conclude that substantial lateral and vertical advective influences must be invoked to account for the differences.Advective influences are potentially greater on ²³⁴Th fluxes derived from water column deficits relative to those obtained from traps because the calculation of deficits in open-ocean settings is dominated by the magnitude of the “dissolved” ²³⁴Th fraction. For observed current velocities of 5–20 cm s⁻¹, in one radioactive mean-life of ²³⁴Th, the water column at the DYFAMED site can reflect ²³⁴Th scavenging produced tens to hundreds of kilometers away. In contrast, most of the ²³⁴Th flux collected in shallow sediment traps at the DFYFAMED site was in the fraction settling >200 m d⁻¹; in effect the sediment trap can integrate the ²³⁴Th flux over distances 40-fold less than water column ²³⁴Th distributions. In some sense, sediment trap and water column sampling for ²³⁴Th provide complementary pictures of ²³⁴Th export. However, because the two methods can be dominated by different processes and are subject to different biases, their comparison must be treated with caution.  相似文献   

Further investigations on why POC concentrations differ in samples collected by Niskin bottle and in situ pump     

Zhanfei Liu  J. Kirk Cochran  Cindy Lee  Beat Gasser  Juan Carlos Miquel  Stuart G. Wakeham 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(18):1558-1567

Particulate organic carbon (POC) concentrations measured in bottles are often higher than those measured by in situ pumps when samples are taken concurrently. In previous work, we suggested that differential collection of zooplankton might explain this systematic discrepancy in POC between these small volume (bottle) and large volume (in situ pump) techniques. We have now further quantified the carbon contributed by zooplankton collected in the >70-μm particulate fractions from both bottles and pumps at sites in the Mediterranean Sea and Long Island Sound. Our results show that zooplankton abundance and lipid concentrations from zooplankton are one order of magnitude higher in the bottles than in the pumps, supporting the idea that part of the pump–bottle difference is due to collection of more zooplankton by the bottles. Particle washout off the 70-μm mesh used in the in situ pump may cause loss of some particles as well. However, zooplankton in the >70-μm fraction from the bottles contributed only about 1–2 μM POC, which cannot explain the up to 20 μM POC differences observed in this study. Thus, the mechanisms leading to such a large POC difference are still unclear and need to be further investigated. POC concentrations measured using microquartz filters were similar to those using glass fiber filters, suggesting that filter types cannot explain the higher POC observed in bottles, where glass fiber filters are normally used. Furthermore, we investigated several different pump inlet designs to determine how these might affect the ability of pumps to collect and retain large (>70 μm) particles, including zooplankton. The comparison among different pump inlets suggests that inlet design affects the efficiency and retention of large particles and that a sealed filter holder with a narrow right-angle tubular opening is the most efficient at catching/retaining zooplankton.  相似文献   

New data on the concentration of plutonium isotopes in the sediments of the Barents Sea     

Matishov  G. G.  Kasatkina  N. E.  Leppanen  A. -P.  Matishov  D. G.  Solatie  D. 《Doklady Earth Sciences》2011,440(2):1445-1448

Doklady Earth Sciences -  相似文献