Fourier-transform Infrared Spectroscopy (FTIRS), a New Method to Infer Past Changes in Tree-line Position and TOC using Lake Sediment     

Peter Rosén  Per Persson 《Journal of Paleolimnology》2006,35(4):913-923

This study tests the hypothesis that Fourier-transform infrared spectroscopy (FTIRS) of lake sediments can be used to infer past changes in tree-line position and total organic carbon (TOC) content of lake water. A training set of 100 lakes from northern Sweden spanning a broad altitudinal and TOC gradient from 0.7 to 14.9 mg/l was used to assess whether vegetation zones and TOC can be modelled from FTIR spectra of surface sediments (0–1 cm) using principal component analysis (PCA) and partial least squares (PLS) regression. Preliminary results show that FTIRS of lake sediments can be used to reconstruct past changes in tree line and the TOC content of lake water, which is hardly surprising since FTIRS registers the properties of organic and minerogenic material derived from the water mass and the drainage area. The FTIRS model for TOC gives a root mean squared error (RMSECV) of calibration of 1.4 mg/l (10% of the gradient) assessed by internal cross-validation (CV) yielding an R_cv² of 0.64. This should be compared with a near-infrared spectroscopy (NIRS) and diatom transfer function for TOC from the same set of lakes, which have a R_cv² of 0.61 and 0.31, and RMSECV of 1.6 and 2.3 mg/l, respectively. The FTIRS-TOC model was applied to a Holocene sediment core from a tree-line lake and the results show similar trends as inferences from NIRS and pollen from the same core. Overall, the results indicate that changes in FTIR spectra from lake sediments reflect differences in catchment vegetation and TOC, and that FTIRS-models based on surface-sediment samples can be applied to sediment cores for retrospective analysis.  相似文献   

Performance of the In Situ Microcosm Technique for Measuring the Degradation of Organic Chemicals in Aquifers     

Per H. Nielsen  Thomas H. Christensen  Hans-Jørgen Albrechtsen  Robert W. Gillham 《Ground Water Monitoring & Remediation》1996,16(1):130-140

An in situ microcosm (ISM) consists of a stainless steel cylinder isolating about 2 L of the aquifer and is equipped with valves allowing for loading and sampling from the ground surface. During the last five years, this technique has been used frequently to study the degradation of organic chemicals in polluted and pristine aquifers representing different redox environments. The ISM technique has great potential for providing field-relevant degradation potentials and rate constants, but care must be taken in using the equipment and interpreting the results. This paper provides details concerning the installation and operation of an ISM and presents experiences concerning data interpretation and monitoring of redox conditions.  相似文献   

Time dependence of organic matter decay and mixing processes in Framvaren, a permanently anoxic fjord in South Norway     

David W. Dyrssen  Per O. J. Hall  Conny Haraldsson  Melissa Chierici  Jens M. Skei  H. Göte östlund 《Aquatic Geochemistry》1996,2(2):111-129

Three different layers have been identified in Framvaren, which has a maximum water depth of 184 m. One oxic layer above the redoxcline at 18–20 m. One anoxic layer from 20 to 100 m which is occasionally ventilated by a flow over the sill (which has a depth of 2.5 m), and finally a stagnant layer below 100 m. Using the release rate of silica from the bottom and measurements of the concentration of HTO it is possible to make some calculations on the annual volume of interleaving in the layers 25–50 m, 50–75 m, and 75–100 m together with the advective flows. Reliable values of the sulfide concentration were obtained by precipitating and weighing HgS together with careful protection of all anoxic water samples with argon. The light yellow color of the precipitate in the depth range 25 to 80 m indicates that the occasional ventilation will cause such reactions as 0.50₂ + H₂S S(colloidal) + H₂O. The elemental sulfur, being stabilized with HS^–, is set free upon the precipitation of HgS. The new data for the concentration of sulfide give an acceptable stoichiometry for the decay reaction of organic matter. This is not the case with the data of Yao and Millero. The mean values for the concentrations of ammonium and phosphate agree with the new data of Yao and Millero. The mol/mol C/N ratio of 10.1 found in trapped material by Naess and coworkers (1988) agrees with the stoichiometry of the dissolved constituents, i.e. C/N = 9.92 ± 0.45. A denitrification reaction is suggested to explain the high values of C/N. The vertical diffusion coefficient at 100 m calculated from the depth profile of silica was 0.92 × 10^–6 m² s^–1 which lies in the range of values given by Fröyland. Finally, the ¹⁴C age of the total dissolved inorganic carbon (Ct) in the water below 90 m was about 1600 years indicating a bioproduction in the period 8000 years B.P. to A.D. 1853 when a channel was opened between the fjord outside (Helvikfjord) and Framvaren.  相似文献   

Gold in the volcanogenic mercury-rich sulfide deposit Långsele,Skellefte ore district,northern Sweden     

Per Nysten 《Mineralium Deposita》1986,21(2):116-120

The mineralogy of gold from a volcanogenic sulfide deposit in northern Sweden (Långsele) was studied. The enrichment of gold and silver in massive ore occurs associated with an intrusive metadolerite vein which can be traced across the ore. The emplacement of this vein mobilized the precious metals together with galena and Pb-Sb sulfosalts into fractures and low pressure zones. A high mercury content at L»ngsele (average 250 ppm) has influenced the gold mineralogy. Thus, gold occurs as Au-Ag amalgam, native gold and rarely as aurostibite (AuSb₂). The results of microprobe analyses of amalgam cluster around Au_0.45Ag_0.45Hg_0.10. The composition of ternary amalgam is discussed in connection with the synthetic Au-Ag-Hg system. Furthermore, native gold was found myrmekitically integrown with stibnite which has been interpreted as a breakdown product of aurostibite at low temperature.  相似文献   

Intrinsic biodegradation of toluene coupled to the microbial reduction of ferric iron: laboratory column experiments     

Zuoping Zheng  Per Aagaard  Gijs D. Breedveld 《Environmental Geology》2002,42(6):649-656

Intrinsic biodegradation of toluene coupled with the microbial reduction of ferric iron (Fe(III)) as the terminal electron acceptor was studied by using laboratory column experiments under continuous flow conditions. Columns were packed with contaminated aquifer sediment and N₂-purged groundwater taken from the western part of the Gardermoen aquifer. The columns were operated anaerobically at 8 °C (in-situ temperature). Chloride was initially used to characterize flow properties of the columns. Intrinsic biodegradation of toluene, including abiotic loss and biological loss, was estimated by comparing breakthrough curves of toluene for live columns and sterilized control columns based on mass balance in steady-state conditions. The column experiments were run at two different flow velocities. The estimated average intrinsic rate was -0.73 and -0.53 mM day^-1 for pore-water velocities of 1.75 and 2.68 cm h^-1, respectively, corresponding to -0.27 and -0.22 mM day^-1 in biological loss rate. The results indicate that intrinsic biodegradation of toluene could be used as an efficient remediation approach for contaminated groundwater at the Gardermoen fire-fighting training site.  相似文献   

Sorption and anaerobic biodegradation of soluble aromatic compounds during groundwater transport. 2. Computer modeling     

Zuoping Zheng  Per Aagaard  Gijs D. Breedveld 《Environmental Geology》2002,41(8):933-941

. The natural attenuation of a binary mixture of toluene and 1,2,4-trimethylbenzene, which was previously experimentally demonstrated in anaerobic column experiments, was simulated with the newly-developed PHREEQC model to reveal the biogeochemical processes involved. The processes considered in this model include advection, diffusion, sorption, redox reactions (e.g., oxidation of toluene and 1,2,4-trimethylbenzene coupled to the reduction of microbial ferric iron), precipitation of secondary minerals such as siderite and magnetite, and dissolution of hydrous ferric oxides, as well as other thermodynamic equilibrium reactions. The functions of advection and diffusion built into the PHREEQC were conventionally simulated. The sorption was kinetically simulated based on a bicontinuum model, whereas biodegradation was described using a multiple-term Monod model. The processes mentioned above were coupled with a geochemical equilibrium model. The consistency between the experimental and modeling results indicates that the processes defined and the controlling parameters chosen could describe the coupled interactions between transport and biogeochemical reactions for the studied system. The discrepancy between modeling and experimental observations, however, also revealed the limitation of the modeling approach. In general, the model approach, which incorporates simplified mathematical representations of the true physico-chemical dynamics of the sorption and biodegradation processes of toluene and 1,2,4-trimethylbenzene under anaerobic conditions is a very efficient and good predictive tool in management and remediation of contaminant groundwater aquifers.  相似文献   

Temporal correlations of atmospheric mapping function errors in GPS estimation     

Borys Stoew  Tobias Nilsson  Gunnar Elgered  Per O. J. Jarlemark 《Journal of Geodesy》2007,81(5):311-323

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Rating curve uncertainty and change detection in discharge time series: case study with 44‐year historic data from the Nyangores River,Kenya          下载免费PDF全文

John Juston  Per‐Erik Jansson  David Gustafsson 《水文研究》2014,28(4):2509-2523

The intersection of the developing topic of rating curve and discharge series uncertainty with the topic of hydrological change detection (e.g., in response to land cover or climatic change) has not yet been well studied. The work herein explores this intersection, with consideration of a long‐term discharge response (1964–2007) for a ~650‐km² headwater basin of the Mara River in west Kenya, starting with stream rating and daily gauge height data. A rating model was calibrated using Bayesian methods to quantify uncertainty intervals in model parameters and predictions. There was an unknown balance of random and systemic error in rating data scatter (a scenario not likely unique to this basin), which led to an unknown balance of noise and information in the calibrated statistical error model. This had implications on testing for hydrological change. Overall, indications were that shifts in basin's discharge response were rather subtle over the 44‐year period. A null hypothesis for change using flow duration curves (FDCs) from four different 8‐year data intervals could be either accepted or rejected over much of the net flow domain depending on different applications of the statistical error model (each with precedence in the literature). The only unambiguous indication of change in FDC comparisons appeared to be a reduction in lowest baseflow in recent years (flows with >98% exceedance probability). We defined a subjective uncertainty interval based on an intermediate balance of random and systematic error in the rating model that suggested a possibility of more prevalent impacts. These results have relevance to management in the Mara basin and to future studies that might establish linkages to historic land use and climatic factors. The concern about uncertain uncertainty intervals (uncertainty²) extends beyond the Mara and is relevant to testing change where non‐random rating errors may be important and subtle responses are investigated. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Reply to Comment on “The Keisarhjelmen detachment records Silurian–Devonian extensional collapse in Northern Svalbard”          下载免费PDF全文

Alvar Braathen  Per Terje Osmundsen  Harmon Maher  Morgan Ganerød 《地学学报》2018,30(4):322-324

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Modelling the potential impact of global warming on Ips typographus voltinism and reproductive diapause     

Anna Maria Jönsson  Susanne Harding  Paal Krokene  Holger Lange  Åke Lindelöw  Bjørn Økland  Hans Peter Ravn  Leif Martin Schroeder 《Climatic change》2011,109(3-4):695-718

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