Effect Of Redox Conditions Research Articles

Retention of selenium and caesium on crystalline rock: the effect of redox conditions and mineralogical composition

Isotopes of caesium and selenium belong among fission products, being present in spent nuclear fuel (SNF) and high level waste (HLW), and contribute significantly to the risk associated with SNF and HLW disposal in deep geological repositories. The present work is focused on sorption behaviour of Cs and Se species on two types of crystalline rock, granite from Melechov massif (Czech Republic) and Aspo diorite from the underground laboratory Aspo (Sweden). The aim was to compare sorption behaviour of Cs and Se on these rocks under aerobic and anaerobic conditions and determine the influence of redox conditions on their kinetic sorption properties.

Trace Element Solubility in a Multimetal-Contaminated Soil as Affected by Redox Conditions

Redox conditions play an outstanding role in controlling the behaviour of trace elements in soil environments. They are not only sensitive to water saturation but also to soil temperature because many redox reactions are mediated by microorganisms. In this study, we investigated the influence of oxidising (oxygen predominant), weakly reducing (MnIII,IV reduction) and moderately reducing (FeIII reduction) conditions at three temperature regimes (7, 15 and 25 °C) on the solubility of ten trace elements. Multimetal-contaminated topsoil (pH 5.8) from a floodplain in Germany was investigated with the following aqua regia-soluble concentrations: Zn 903, Cu 551, Cr 488, Pb 354, Ni 93.5, As 35.7, Co 22.4, Sb 20.5, Cd 8.3 and Mo 6.5 mg kg−1. Soil suspensions were held at fixed redox potential in microcosm experiments, sampled at every third day and analysed for trace elements. Time to achieve weakly and particularly moderately reducing conditions was temperature dependent and increased in the order 25 °C < 15 °C < 7 °C. Under oxidising conditions, the solubility of the trace elements was low. Reductive dissolution of Mn oxides under weakly reducing conditions was accompanied by a release of Co and Mo. Reductive dissolution of Fe oxides (and of remaining Mn oxides) under moderately reducing conditions additionally led to a release of As, Cd, Cr, Ni and Pb, whereas Cu and Zn were hardly affected. Antimony revealed a different behaviour because, after a first increase, a continuous decrease in its concentration was observed soon after the onset of weakly reducing conditions. We conclude that soil temperature should be considered as a master variable, to distinguish between weakly and moderately reducing soil conditions, and that it is necessary to keep element-specific behaviour in mind when dealing with the effects of redox conditions in soils on trace element solubility.

Effect of redox conditions on pharmaceutical loss during biological wastewater treatment using sequencing batch reactors

We lack a clear understanding of how wastewater treatment plant (WWTP) process parameters, such as redox environment, impact pharmaceutical fate. WWTPs increasingly install more advanced aeration control systems to save energy and achieve better nutrient removal performance. The impact of redox condition, and specifically the use of microaerobic (low dissolved oxygen) treatment, is poorly understood. In this study, the fate of a mixture of pharmaceuticals and several of their transformation products present in the primary effluent of a local WWTP was assessed in sequencing batch reactors operated under different redox conditions: fully aerobic, anoxic/aerobic, and microaerobic (DO concentration ≈0.3mg/L). Among the pharmaceuticals that were tracked during this study (atenolol, trimethoprim, sulfamethoxazole, desvenlafaxine, venlafaxine, and phenytoin), overall loss varied between them and between redox environments. Losses of atenolol and trimethoprim were highest in the aerobic reactor; sulfamethoxazole loss was highest in the microaerobic reactors; and phenytoin was recalcitrant in all reactors. Transformation products of sulfamethoxazole and desvenlafaxine resulted in the reformation of their parent compounds during treatment. The results suggest that transformation products must be accounted for when assessing removal efficiencies and that redox environment influences the degree of pharmaceutical loss.

Correction: Effect of Redox Conditions on Bacterial Community Structure in Baltic Sea Sediments with Contrasting Phosphorus Fluxes

Correction: Effect of Redox Conditions on Bacterial Community Structure in Baltic Sea Sediments with Contrasting Phosphorus Fluxes

Thermodynamic and mass balance constraints on iron‐bearing phyllosilicate formation and alteration pathways on early Mars

Widespread occurrences of phyllosilicates, predominantly nontronite and Mg saponite, in the Noachian‐aged crust of Mars place constraints on water availability and surface conditions. However, the Noachian atmosphere likely lacked oxidants capable of forming nontronite from the basaltic crust and its origins are thus uncertain. In this study, scenarios for the formation of iron‐bearing phyllosilicates from the weathering and hydrothermal alteration of Martian basalt were investigated using geochemical modeling to establish plausible pathways of nontronite generation and the effect of redox conditions on associated secondary phases. Hydrothermal alteration produced FeII and Mg saponite, serpentine, and zeolites at 100°C and chlorite, prehnite, and talc at 250°C, consistent with phases observed in crater deposits on Mars. Anoxic weathering produced primarily FeII and Mg saponite. High water‐rock ratios produced Al‐clays and amorphous silica and high pCO2 conditions inhibited smectite formation because of carbonate precipitation. Oxic weathering produced primarily nontronite and Mg saponite. Later oxidation of anoxic weathering products also formed nontronite‐Mg saponite assemblages; oxidation products of hydrothermal assemblages included nontronite, Mg saponite, and either Al smectites or residual zeolites or prehnite. These calculations demonstrate that there are multiple plausible routes to form Fe/Mg smectites on early Mars and that an oxidizing atmosphere need not have existed in the Noachian. Decoupling iron oxidation from initial clay formation raises the possibilities that Mars transitioned to conditions favoring widespread iron oxidation after phyllosilicate formation ceased and that residual, unoxidized ferrous iron phyllosilicates still exist today in the Martian subsurface.

The effect of redox conditions on sphagnum acid thermochemolysis product distributions in a northern peatland

Thermally assisted hydrolysis and methylation (THM) in the presence of tetramethylammonium hydroxide (TMAH) of a range of layers in eight peat cores from the Ryggmossen peatland (central Sweden) was carried out. This yielded a complex mixture including components I (methylated 4-isopropenylphenol (IUPAC name: 1-methoxy-4-(prop-1-en-2-yl)benzene)), IIa/b (methylated cis/trans 3-(4′-hydroxyphen-1-yl)but-2-enoic acid (IUPAC names: (E/Z)-methyl 3-(4-methoxyphenyl)but-2-enoate)) and III (methylated 3-(4′-hydroxyphen-1-yl)but-3-enoic acid (IUPAC name: methyl 3-(4-methoxyphenyl)but-3-enoate)) which have been assigned as products from “bound” sphagnum acid. The proportion of the individual sphagnum acid products relative to total Sphagnum yield revealed the simultaneous degradation of all four components in the unsaturated layer (which is characterised by oxic conditions) concomitant with the decrease of the total Sphagnum yield. Following their degradation in the surficial oxic layer, the total amounts of the sphagnum acid thermochemolysis products stabilise in the deeper seasonally saturated peat. With a further increase in burial depth, in the permanently saturated anoxic peat, the distribution of thermochemolysis products becomes dominated by I. The increase of σI% relative to σ(IIa/b and III)% indicates that the mode of binding of sphagnum acid into the peat changes as a function of burial depth and hence position relative to the water table. Therefore the relative amounts of the four sphagnum acid THM products show some promise as indicators of redox conditions in young surficial peats.

Effect of Redox Conditions on the Fission Products Release from Irradiated Oxide Fuel

An in-house designed system for inductive vaporization (InVap) enables the investigation of the fission product (FP) release from irradiated fuel at temperatures up to 2300°C and under different redox conditions. Via the direct connection of the InVap device to an inductively coupled plasma mass spectrometer (ICP-MS) the on-line monitoring of the FP release is possible. Theoretically modeled and data experimentally determined on thermal treatment of irradiated fuel and release of volatile FPs (Cs, I), semi-volatile FPs (Sr, Ba, Tc, Mo, Ru) and actinides (U, Pu or Am) are discussed regarding to the nuclear fuel reprocessing technology.

Effect of redox conditions on the synthesis and phosphorylation of β-subunit of mitochondrial F0F1-ATPase of maize (Zea mays)

Effect of redox conditions on the synthesis and phosphorylation of β-subunit of mitochondrial F0F1-ATPase of maize (Zea mays)

Effects of redox conditions and zinc(II) ions on metallothionein aggregation revealed by chip capillary electrophoresis

Metallothioneins (MTs) belong to cysteine-rich proteins with unique higher structure. One of the most known MT's functions is metals detoxification and maintaining their homeostasis in a cell. Structure of MT with naturally occurred zinc(II) ions can be affected by concentration of metal ions as well as redox milieu inside a cell, however the exact explanation and biochemical effects of the structural changes are still missing. In this study we used capillary electrophoresis on chip coupled with fluorescence detection to determine structural changes of MT with increasing concentration of zinc(II) ions and under various redox conditions. To investigate the structural-dependent effects, reduced and/or oxidized apo-MT (MT without natural occurred metal ion) was prepared. Zinc binding into reduced and/or oxidized apo-MT was compared. MT was incubated with 0, 5, 15, 25, 50 and 100 μM ZnCl 2 for 1 h in 37 °C. Formation of MT aggregates with increasing zinc concentration was observed by spectrophotometry, chip capillary electrophoresis, and SDS-PAGE. We found out that reduced MT forms aggregates more readily compared to oxidized MT. Using the chip capillary electrophoresis allowed us relative quantification of MT aggregation as a decrease in the area of the signal corresponding to the monomer form of MT (Mw 15 kDa, migration time 26.5 s) and its ratio to total signal (sum of all signals measured by the electrophoresis). The dependences had an exponential character with equation y = 2.4 × e −0.01 x , R 2 = 0.945 for 15 kDa peak area and y = 0.11 × e −0.01 x , R 2 = 0.938 for decrease of 15 kDa peak area ratio to the total signal. Zn–MT interaction was 30% faster during the first 15 min and 50% faster during the whole experiment for reduced MT. It can be concluded that formation of MT aggregates is dependent on redox state and Zn(II) concentration.

Effect of redox conditions on bacterial and fungal biomass and carbon dioxide production in Louisiana coastal swamp forest sediment

Fungal and bacterial carbon dioxide (CO 2) production/emission was determined under a range of redox conditions in sediment from a Louisiana swamp forest used for wastewater treatment. Sediment was incubated in microcosms at 6 Eh levels (–200, –100, 0, + 100, + 250 and + 400 mV) covering the anaerobic range found in wetland soil and sediment. Carbon dioxide production was determined by the substrate-induced respiration (SIR) inhibition method. Cycloheximide (C 15H 23NO 4) was used as the fungal inhibitor and streptomycin (C 21H 39N 7O 12) as the bacterial inhibitor. Under moderately reducing conditions (Eh > + 250 mV), fungi contributed more than bacteria to the CO 2 production. Under highly reducing conditions (Eh ≤ 0 mV), bacteria contributed more than fungi to the total CO 2 production. The fungi/bacteria (F/B) ratios varied between 0.71–1.16 for microbial biomass C, and 0.54–0.94 for microbial biomass N. Under moderately reducing conditions (Eh ≥ + 100 mV), the F/B ratios for microbial biomass C and N were higher than that for highly reducing conditions (Eh ≤ 0 mV). In moderately reducing conditions (Eh ≥ + 100 mV), the C/N microbial biomass ratio for fungi (C/N: 13.54–14.26) was slightly higher than for bacteria (C/N: 9.61–12.07). Under highly reducing redox conditions (Eh ≤ 0 mV), the C/N microbial biomass ratio for fungi (C/N: 10.79–12.41) was higher than for bacteria (C/N: 8.21–9.14). For bacteria and fungi, the C/N microbial biomass ratios under moderately reducing conditions were higher than that in highly reducing conditions. Fungal CO 2 production from swamp forest could be of greater ecological significance under moderately reducing sediment conditions contributing to the greenhouse effect (GHE) and the global warming potential (GWP). However, increases in coastal submergence associated with global sea level rise and resultant decrease in sediment redox potential from increased flooding would likely shift CO 2 production to bacteria rather than fungi.

Effects of Primary Substrate Concentration on NDMA Transport during Simulated Aquifer Recharge

N-nitrosodimethylamine (NDMA) is known to be highly carcinogenic and is present in drinking water, wastewater, and a variety of foods. Because of its presence in chloraminated water at nanogram per liter concentrations, NDMA has become an emerging issue for reclaimed water which may be used for aquifer recharge or irrigation. This research investigated the fate of NDMA in two soil column systems used to simulate subsurface transport. One column system was operated under aerobic conditions with increasing primary substrate concentration where the biodegradable organic carbon (BDOC) in reclaimed water was used as the primary substrate. The reclaimed water content in the influent was increased from 0 to 25% in the column to increase the BDOC concentration. Negligible NDMA removal was observed at 0% reclaimed water and increasing the primary substrate in the influent resulted in NDMA removal suggesting that biodegradation of NDMA might be a cometabolic process. The effects of redox conditions on NDMA fate was studied by operating a second column system with 100% reclaimed water under anoxic conditions and then changing the conditions to aerobic. It was observed that NDMA removal was similar under both aerobic and anoxic condition, however, much lower effluent concentrations were observed under aerobic conditions. Under anoxic condition, a normalized mass removal rate of 254 ng NDMA/mg DOC was observed which increased to 273-ng NDMA/mg DOC under aerobic conditions. The majority of NDMA and substrate removal occurred in the first of three columns in series column under both aerobic and anoxic conditions. Normalized mass removal rates of NDMA after the first, second, and third columns were 372, 30, and 20 ng NDMA/mg DOC, respectively. Since the majority of dissolved organic carbon was also removed in the first column, NDMA biodegradation was consistent with cometabolic activity. Batch tests verified the biodegradation removal potential of NDMA. Addition of a methylotrophic substrate, methanol and an aromatic substrate, toluene, did not increase NDMA removal.

Effect of redox conditions on phosphate exchangeability and iron forms in a soil amended with ferrous iron

SummaryApplication of iron (Fe) ‐rich amendments to soils has been proposed as a means of decreasing phosphorus (P) losses from soils. However, anoxic conditions following soil saturation are known to increase Fe and P solubility in soils, thus cancelling out the potential benefits. Our aim was to evaluate the effects of continuous oxic, continuous anoxic and alternating anoxic/oxic conditions on P exchangeability and Fe forms in soil amended with Ca(OH)2 and FeSO4. We incubated amended and unamended soils under these conditions for 8 weeks and measured Fe forms and P exchangeability. Under oxic conditions, addition of Ca(OH)2 and FeSO4 resulted in a strong decrease in P exchangeability and an increase in oxalate‐extractable Fe. Mössbauer analyses suggested that an unidentified Fe oxide (D1oxide) with a strong sorbing capacity for P was precipitated. Under continuously anoxic conditions, P exchangeability and oxalate‐extractable Fe increased with or without the amendments. Mössbauer analyses suggested that there was a partial dissolution of the D1oxide phase, precipitation of another unidentified Fe oxide (S3) and a reduction of structural Fe3+ in phyllosilicate, thereby increasing soil negative charge. These transformations resulted in a strong increase in rapidly exchangeable P. Alternating anoxic and oxic periods induced the dissolution and precipitation of iron oxides and the increase and decrease in P exchangeability. Implications of the results for limiting P losses from grassland soils are discussed.

Effect of redox conditions on the evaporation of oxide melts in the CaO-MgO-FeO-Al2O3-SiO2 system

Physicochemical studies of cosmic substance provide a basis for fundamental concepts of the origin, composition, and structure of planets and meteorites. Of great importance in this context is the experimental study of the properties of oxides and melts in the CaO – MgO – FeO – Al 2 O 3 – SiO 2 system, which is the basic system of meteoritic substance and, in particular, the hightemperature substance of white inclusions (CAI). There is extensive evidence for the significant influence of changes in temperature and pressure on this substance during its formation and evolution. The investigation of its evaporation and condensation is of special interest because of the combination of high-temperature and cooling stages during its evolution. Data on CAI evaporation and condensation, which are required for calculations, can be obtained experimentally. The most efficient approach is a combination of the Knudsen effusion technique with the mass-spectrometric analysis of evaporation products [1‐3]. This study is aimed at determining the influence of redox conditions on oxide melt evaporation by the example of melts in the CaO – MgO – FeO – Al 2 O 3 – SiO 2 system. Note that the evaporation of such multicomponent oxide melts is dominated by the evaporation reactions of simple oxides, because the content of complex gaseous oxide compounds in the vapor is insignificant [3]. Therefore, the evaporation of these melts can be described to a first approximation by the evaporation tendencies of simple oxides.

Evolution of a bacteriophytochrome from light to redox sensor

Bacteriophytochromes are red/far-red photoreceptors that bacteria use to mediate sensory responses to their light environment. Here, we show that the photosynthetic bacterium Rhodopseudomonas palustris has two distinct types of bacteriophytochrome-related protein (RpBphP4) depending upon the strain considered. The first type binds the chromophore biliverdin and acts as a light-sensitive kinase, thus behaving as a bona fide bacteriophytochrome. However, in most strains, RpBphP4 does not to bind this chromophore. This loss of light sensing is replaced by a redox-sensing ability coupled to kinase activity. Phylogenetic analysis is consistent with an evolutionary scenario, where a bacteriophytochrome ancestor has adapted from light to redox sensing. Both types of RpBphP4 regulate the synthesis of light harvesting (LH2) complexes according to the light or redox conditions, respectively. They modulate the affinity of a transcription factor binding to the promoter regions of LH2 complex genes by controlling its phosphorylation status. This is the first complete description of a bacteriophytochrome signal transduction pathway involving a two-component system.

Techniques for the Stabilization and Assessment of Treated Copper-, Chromium-, and Arsenic-contaminated Soil

Remediation mainly based on excavation and burial of the contaminated soil is impractical with regard to the large numbers of sites identified as being in need of remediation. Therefore, alternative methods are needed for brownfield remediation. This study was conducted to assess a chemical stabilization procedure of CCA-contaminated soil using iron (Fe)-containing blaster sand (BS) or oxygen-scarfing granulate (OSG). The stabilization technique was assessed with regard to the feasibility of mixing ameliorants at an industrial scale and the efficiency of the stabilization under different redox conditions. The stability was investigated under natural conditions in 1-m3 lysimeters in a field experiment, and the effect of redox conditions was assessed in a laboratory experiment (10 L). The treatments with high additions of ameliorant (8% and 17%) were more successful in both the laboratory and field experiments, even though there was enough Fe on a stochiometric basis even at the lowest addition rates (0.1% and 1%). The particle size of the Fe and the mixing influenced the stabilization efficiency. The development of anaerobic conditions, simulated by water saturation, increases the fraction of arsenic (AsIII) and, consequently, As mobility. The use of high concentrations of OSG under aerobic conditions increased the concentrations of nickel (Ni) and copper (Cu) in the pore water. However, under anaerobic conditions, it decreased the As leaching compared with the untreated soil, and Ni and Cu leaching was not critical. The final destination of the treated soil should govern the amendment choice, that is, an OSG concentration of approximately 10% may be suitable if the soil is to be landfilled under anaerobic conditions. Alternatively, the soil mixed with 1% BS could be kept under aerobic conditions in a landfill cover or in situ at a brownfield site. In addition, the treatment with BS appeared to produce better effects in the long term than treatment with OSG.

Biological and chemical interactions with U(VI) during anaerobic enrichment in the presence of iron oxide coated quartz

Microcosm experiments were performed to understand chemical and biological interactions with hexavalent uranium (U(VI)) in the presence of iron oxide bearing minerals and trichloroethylene (TCE) as a co-contaminant. Interactions of U(VI) and hydrous iron oxide moieties on the mineral oxide surfaces were studied during enrichments for dissimilatory iron reducing (DIRB) and sulfate reducing bacteria (SRB). Microbes enriched from groundwater taken from the Test Area North (TAN) site at the Idaho National Laboratory (INL) were able to reduce the U(VI) in the adsorption medium as well as the iron on quartz surfaces. Early in the experiment disappearance of U(VI) from solution was a function of chemical interactions since no microbial activity was evident. Abiotic removal of U(VI) was enhanced in the presence of carbonate. As the experiment proceeded, further removal of U(VI) from solution was associated with the fermentation of lactate to propionate and acetate. During later phases of the experiment when lactate was depleted from the growth medium in the microcosm containing the DIRB enrichments, U(VI) concentrations in the solution phase increased until additional lactate was added. When additional lactate was added and fermentation proceeded, U(VI) concentrations in the liquid phase again returned to near zero. Similar results were shown for the SRB enrichment but lower uranium concentrations were seen in the liquid phase, while in the enrichment with carbonate a similar increase in uranium concentration was not seen. Chemical and biological interactions appear to be important on the mobilization/immobilization of U(VI) in an iron oxide system when TCE is present as a co-contaminant. Interestingly, TCE present in the microcosm experiments was not dechlorinated which was probably an effect of redox conditions that were unsuitable for reductive dechlorination by the microbial culture tested.

Leaching of Np and Tc From Doped Nuclear Waste Glasses in Clay Media: The Effects of Redox Conditions

ABSTRACTBoom Clay is the candidate geologic formation in Belgium for disposal of vitrified high level waste. In the waste glass, 237Np and 99Tc are some of the principal radionuclides. The leaching behaviour of these nuclides has been studied in dissolution tests involving glass doped with 237Np and 99Tc and was found to depend strongly on the redox conditions of the media contacting the glass. Static tests with the reference R7T7 glass and the reference PAMELA SM539 glass were performed in two clay media that may interact with the glass during the geological disposal. The first test medium consisted of FoCa-clay (Fourges-Cahaignes-clay), which is an oxidised clay. The second test medium was a mixture of backfill material, consisting mainly of FoCa-Clay, with metal corrosion products and Boom Clay. Lower Np and Tc concentrations were found in Boom Clay compared to FoCa-clay. In FoCaclay, Np and Tc were predominately in their oxidised form. Although Tc is mostly present in the soluble pertechnetate form, the Np concentrations are lower than expected for the chemistry of Np(V) in the medium. The concentrations of the radionuclides are steady-state concentrations rather than thermodynamic concentrations. Different mechanisms can be invoked to explain these Np concentrations. In Boom Clay, the measured Np concentrations are close to the solubility limit whereas the Tc concentrations are slightly higher than those calculated in Boom Clay at thermodynamic equilibrium. The initial specific activity of the radionuclide in the glass was found to influence the soluble concentration. Np and Tc were not found to be retained in the glass reaction layer for both media.

Effect of Redox Conditions on the Sorption of Plutonium onto Geological Materials

ABSTRACTThis paper presents the latest results from a programme of generic sorption studies undertaken to increase confidence in data underpinning the performance assessment for a potential high-level radioactive waste repository in Japan. The sorption of plutonium onto basalt and sandstone was studied as a function of redox conditions that ranged from strongly reducing to oxidising. Geochemical modelling was used to aid experimental design and the interpretation of results.

Effect of redox conditions on MTBE biodegradation in surface water sediments.

Microbial degradation of methyl tert-butyl ether (MTBE) was observed in surface water-sediment microcosms under anaerobic conditions. The efficiency and products of anaerobic MTBE biodegradation were dependent on the predominant terminal electron-accepting conditions. In the presence of substantial methanogenic activity, MTBE biodegradation was nominal and involved reduction of MTBE to the toxic product, tert-butyl alcohol (TBA). In the absence of significant methanogenic activity, accumulation of [14C]TBA generally decreased, and mineralization of [U-14C]MTBE to 14CO2 generally increased as the oxidative potential of the predominant terminal electron acceptor increased in the order of SO4, Fe(III), Mn(IV) < NO3 < O2. Microbial mineralization of MTBE to CO2 under Mn(IV)-or SO4-reducing conditions has not been reported previously. The results of this study indicate that microorganisms inhabiting the sediments of streams and lakes can degrade MTBE effectively under a range of anaerobic terminal electron-accepting conditions. Thus, anaerobic bed sediment microbial processes may provide a significant environmental sink for MTBE in surface water systems throughout the United States.

Effects of Redox Conditions and Flow Processes on the Mobility of Dissolved Organic Carbon and Nitrogen in a Forest Soil

AbstractIn forest ecosystems, organic solutes play prominent roles in pollutant and nutrient transport. This study, conducted in subalpine forested Humaquepts in Switzerland, investigated the influence of redox conditions and flow processes on dissolved organic carbon (DOC) and dissolved organic nitrogen (DON). In the mineral soil, concentrations of DOC were higher under reduced than under oxidized conditions. They averaged 1.2 mmol DOC L−1 in the reduced mineral soil at a 100‐cm depth. A close correlation between DOC and dissolved Fe concentrations (r2 = 0.83; p &lt; 0.001) suggests that reductive dissolution of Fe‐oxides was the major reason for the low retention. However, during aerobic sampling of soil solution from the reduced mineral soil, DOC coprecipitated with Fe. This suggests that the DOC input from reduced mineral soils to aerobic stream water is lower than expected from the high DOC concentrations in the soil. Organic N was the major form of total dissolved N at all soil depths. In the reduced subsoil, dissolved N was completely organically bound. This was probably due to both an immobilization of inorganic N and a low retention of DON. During storms, DOC concentrations increased rapidly with increasing discharge in the subsurface flow. At peak flow, DOC concentrations were doubled, compared with base flow. The molar UV absorptivity of DOC in the subsurface flow corresponded closely to that of the topsoil. These findings suggest that DOC concentrations and properties are sensitive to flow velocities, and that DOC is preferentially transported to the subsoil at high discharge.