Changes in fish mercury concentrations over 20 years in an acidified lake subject to experimental liming     

Martti Rask  Roger I. Jones  Marko Järvinen  Anna Paloheimo  Maiju Salonen  Jari Syväranta  Matti Verta 《Applied Geochemistry》2007

Lake Iso Valkjärvi (southern Finland, Europe) was divided in two with a plastic curtain in 1991. One half was neutralized with CaCO₃, and the other acted as a control. Mercury concentrations of perch (Perca fluviatilis) and northern pike (Esox lucius) in the limed and control side of the lake were studied both before and after the treatment. Average Hg concentrations of perch and pike were 0.40 and 1.2 μg g⁻¹ (ww) in the early 1980s and 0.25 and 0.72 μg g⁻¹ (ww) a decade later at the time of liming. Ten years after the liming the Hg concentrations of perch in the limed and control sides of the lake were 0.21 and 0.28 μg g⁻¹ (ww) and those of pike were 0.69 and 0.43 μg g⁻¹ (ww), respectively. Nitrogen isotope ratios (δ¹⁵N) for perch in the sampling period 2002–2004 showed wide variation suggesting variable trophic positions for individual fish. Pike formed two groups according to their δ¹⁵N-values, suggesting that zoobenthos dominated the diet of pike around 20 cm in length and fish that of the larger pikes. Because the δ¹⁵N-values of fish were at similar levels in the limed and control sides of L. Iso Valkjärvi, differences in food web structure cannot account for the different fish Hg concentrations. A more likely explanation is water quality induced differences in the dynamics and bioavailability of Hg, leading to decreased formation of methyl Hg.  相似文献   

Determining the extent of weathering of spilled fuel in contaminated soil using the diastereomers of pristane and phytane     

Cameron P. McIntyre  Paul McA. Harvey  Susan Ferguson  Anna M. Wressnig  Ian Snape  Simon C. George 《Organic Geochemistry》2007,38(12):2131-2134

A method is described for determining the relative extent of weathering in moderately biodegraded, hydrocarbon-contaminated soils from Antarctica. Plotting the pristane diastereomer ratio (PrDR) vs. pristane/phytane (Pr/Ph) allows the relative extent of weathering (primarily evaporation in this case) to be determined. PrDR is used to account for biodegradation as it is independent of evaporation. The method is straightforward and as robust as conventional ratios.  相似文献   

Characterisation of concentrates of heavy mineral sands by micro-Raman spectrometry and CC-SEM/EDX with HCA     

Anna Worobiec  E. Anna Stefaniak  Sanja Potgieter-Vermaak  Zbigniew Sawlowicz  Zoya Spolnik  René Van Grieken 《Applied Geochemistry》2007

The effectiveness of electrostatic separation of zircon and TiO₂ phases during the processing of heavy mineral concentrates derived from heavy mineral sands depends upon the chemical, physical and mineralogical characteristics of the concentrates. Here the authors’ demonstrate the use of combined micro-Raman spectrometry (MRS), scanning electron microscopy (SEM) and computer controlled scanning electron microscopy coupled with an energy-dispersive X-ray detector (CC-SEM/EDX), followed by hierarchical cluster analysis (HCA) to determining these characteristics on samples from the non-magnetic fraction of the Richards Bay (South Africa) heavy mineral concentrate. All samples were found to be predominately comprised a heterogeneous population of grains of zircon and rutile and other TiO₂ polymorphs with diverse physicochemical properties. Combined MRS and CC-SEM/EDX enabled the identification of textural characteristics which impacted on the efficiency of electrostatic separation of zircon and rutile concentrate streams.  相似文献   

Wavefield downward extrapolation for migration velocity analysis on Marmousi data-set     

Andrzej Kostecki  Anna Półchłopek 《Acta Geophysica》2007,55(2):209-221

The authors present a method for estimation of interval velocities using the downward continuation of the wavefield to perform layer-stripping migration velocity analysis. The generalized, phase-shift migration MG(F-K) in wavenumber-frequency domain was used for fulltime downward extrapolation of the wavefield. Such downward depth extrapolation accounts for strong changes of velocity in lateral and vertical directions and helps in correct positioning of the wavefield image in complex structures. Determination of velocity is the recursive process which means that the wavefield on depth level z _n−1 (n = 0, 1, ...) is an input data-set for determination of velocity on level z _n . The velocity ν [x, z _n − z _n−1] can be thus treated as interval velocity in Δz _n = z _n − z _n−1 step. This method was tested on synthetic Marmousi data-set and showed satisfactory results for complex, inhomogeneous media.  相似文献   

The role and significance of extracellular polymers in activated sludge. Part I: Literature review     

Anna Raszka  Monika Chorvatova  Jiri Wanner 《洁净——土壤、空气、水》2006,34(5):411-424

In biological wastewater treatment, bacteria tend to aggregate by forming flocs, biofilms and even granules. A large part of the floc structure in activated sludge is composed of extracellular polymers. The extracellular polymeric substances (EPS) are mainly responsible for the structural and functional integrity of biofilms/flocs and they are considered to be important for the physico‐chemical properties of activated sludge. This review considers the composition of EPS and proportion between the constituents. Moreover it includes the relationship between the EPS constituents and sludge properties such as sludge retention time, hydrophobicity and surface charge.  相似文献   

Method for correction of the prestack migration amplitude of converted waves     

Andrzej Kostecki  Anna Półchłopek 《Acta Geophysica》2006,54(2):113-125

The paper presents a method for correction of amplitude of prestack migration using the reflectivity function. The solution of wave equations for heterogeneous media expressed in the form of Neumann series for converted waves was used to find the reflectivity function. The performance of the proposed method was verified using synthetic models of wavefields. The synthetic models of wavefields were also used to compare amplitude correction levels required by the presented method and the standard amplitude correction methods, i.e., the methods using the spherical divergence and extention factor.  相似文献   

Aqueous volatiles in hydrothermal fluids from the Main Endeavour Field, northern Juan de Fuca Ridge: temporal variability following earthquake activity     

Jeffrey Seewald  Anna Cruse 《Earth and Planetary Science Letters》2003,216(4):575-590

The Main Endeavour Field, northern Juan de Fuca Ridge, experienced intense seismic activity in June 1999. Hydrothermal vent fluids were collected from sulfide structures in September 1999 and July 2000 and analyzed for the abundance of H₂, H₂S, CH₄, CO₂, NH₃, Mg and Cl to document temporal and spatial changes following the earthquakes. Dissolved concentrations of CO₂, H₂, and H₂S increased dramatically in the September 1999 samples relative to pre-earthquake abundances, and subsequently decreased during the following year. In contrast, dissolved NH₃ and CH₄ concentrations in 1999 and 2000 were similar to or less than pre-earthquake values. Aqueous Cl abundances showed large decreases immediately following the earthquakes followed by increases to near pre-earthquake values. The abundances of volatile species at the Main Endeavour Field were characterized by strong inverse correlations with chlorinity. Phase separation can account for 20-50% enrichments of CO₂, CH₄, and NH₃ in low-chlorinity fluids, while temperature- and pressure-dependent fluid-mineral equilibria at near-critical conditions are responsible for order of magnitude greater enrichments in dissolved H₂S and H₂. The systematic variation of dissolved gas concentrations with chlorinity likely reflects mixing of a low-chlorinity volatile-enriched vapor generated by supercritical phase separation with a cooler gas-poor hydrothermal fluid of seawater chlorinity. Decreased abundances of sediment-derived NH₃ and CH₄ in 1999 indicate an earthquake-induced change in subsurface hydrology. Elevated CO₂ abundances in vent fluids collected in September 1999 provide evidence that supports a magmatic origin for the earthquakes. Temperature-salinity relationships are consistent with intrusion of a shallow dike and suggest that the earthquakes were associated with movement of magma beneath the ridge crest. These data demonstrate the large and rapid response of chemical fluxes at mid-ocean ridges to magmatic activity and associated changes in subsurface temperature and pressure.  相似文献   

Neotectonic evolution of the Anaximander Mountains at the junction of the Hellenic and Cyprus arcs     

Johan H. ten Veen  John M. Woodside  Tiphaine A.C. Zitter  Jean F. Dumont  Jean Mascle  Anna Volkonskaia 《Tectonophysics》2004,391(1-4):35

  相似文献   

Transport of Temperature and Humidity Variance and Covariance in the Marine Surface Layer   总被引：3，自引：3，他引：0  

Anna M. Sempreviva  Jørgen Højstrup 《Boundary-Layer Meteorology》1998,87(2):233-253

In this paper we address the budget of potential temperature T and moisture mixing ratio q variances as well as the q-T covariance budget. We focus on the vertical transport and study the quantities contained in these terms. Estimates of transport terms are rare and to the best of our knowledge they have never been shown together in the literature. For this purpose an extensive set of humidity and temperature turbulence data from two heights in a marine environment has been analysed. We discuss and compare our results with results from earlier studies for a range of stability from near-neutral to unstable. Similarity and differences between T and q behaviour in the surface layer over water are presented.  相似文献   

地磁场总强度空间线性相关在预报武定,丽江强震中的应用及机理   总被引：1，自引：0，他引：1  

杜安娜 《地震》1998,18(3):308-312

介绍了地磁场空间线性相关的计算方法。详细阐述了利用此方法在预报武定地震 (1 995年 1 0月 2 4日 ,MS6.5)及丽江地震 (1 996年 2月 3日 MS7.0 )中的应用。笔者对此方法进行了理论推导 ,结果表明相关参量与台站经纬度的选择有关 ,而地磁场的空间线性相关的规律与台站的经纬度选择无关。该结果对台组的选择起到了指导作用  相似文献