The distribution of iron oxidation states in a constructed wetland as an indicator of its redox properties

Wastewater-treatment processes taking place inside constructed wetlands are closely connected with chemical properties of these systems. The aeration of a wetland via the roots of the vegetation (and a subsequent formation of redox-potential gradients) strongly influences the wastewater treatment efficiency, and thus it represents one of the most important characteristics of the wetland. The concentration ratios of individual iron oxidation states (Fe(II) and Fe(III)) were determined as the indicator of the redox properties of the constructed wetland reed bed during this study. Interstitial water from the wetland was sampled eleven times throughout the year 2005. The spectrophotometric method using 1,10-phenanthroline was properly optimized (limits of detection and quantification, sensitivity, linear dynamic range, repeatability, and accuracy values were assessed) and applied for iron determination. Most of iron, ca. 98%, is reduced to the Fe(II) form in raw wastewater and water from the inflow zone of the constructed wetland, however, at the outflow and in the vegetation bed both iron oxidation states are usually detected. The presence of Fe(III) in the reed bed (ca. 10-30% for some samples) demonstrates the aeration of the wetland by the vegetation (Phragmites australis) resulting in a re-oxidation of Fe(II).     

Removal of Anionic Surfactants from Wastewater Using a Constructed Wetland

Removal of anionic surfactants from municipal wastewater using a constructed wetland with a horizontal subsurface flow was studied in 2007 and 2008. Extraction spectrophotometry with methylene blue served to determine the analyte concentrations in individual samples. The anionic surfactant‐removal efficiency depended on actual conditions, mostly the treated water flow intensity, its temperature, and a redox‐potential gradient in the longitudinal profile of the wetland bed. It increased with decreasing inflow and increasing temperature. The average efficiency was 83.7% in 2007 and 81.7% in 2008; however, values higher than 85% were often determined during the summer period. On the other hand, the efficiencies were usually lower than 80% in winter, especially in periods with intensive precipitation and inflows. The average concentration of anionic surfactants in water taken at the outflow was lower than 0.65 mg/l (expressed as sodium dodecyl sulfate). The most significant fraction of anionic surfactants (almost 50%) was degraded at the beginning (1 m from the inflow zone) of the wetland bed. The rhizosphere aeration via the vegetation roots strongly supported the anionic‐surfactant removal.     

Removal of nonionic surfactants from wastewater using a constructed wetland

Removal of nonionic surfactants from municipal wastewater using a constructed wetland with a horizontal subsurface flow was studied in 2009 and 2010. Extraction spectrophotometry with 3′,3″,5′,5″‐tetrabromophenolphthalein ethyl ester and KCl served to determine the analyte concentrations. Triton^® X‐100 was used as a standard to express the nonionic‐surfactant concentrations. Anionic and cationic surfactants were shown not to interfere during the determination. Nonionic surfactants were degraded (to products undeterminable by the method) with a high average efficiency that reached 98.1% in 2009 and 99.1% in 2010, respectively. The average concentration of nonionic surfactants at the inflow was 0.978 mg/l, while it was close to the limit of quantification at the outflow (0.014 mg/l). A significant fraction of nonionic surfactants (38.7%) was already degraded during the pretreatment, and only 14.0% of the nonionic surfactants remained in the interstitial H₂O taken in the vegetation bed at a distance of 1 m from the inflow zone at a 50‐cm depth. Nonionic surfactants were degraded both under aerobic and anaerobic conditions.     

The effect of manganese nanoparticles on performance,redox reactions and epigenetic changes in turkey tissues

The hypothesis of the research was the assumption, that manganese nanoparticles can affect the body in the same way as macromolecules. Their smaller size and greater biological reactivity will potentially allow the Mn addition to the diet to be reduced and, consequently, less excretion of this element into the environment. The aim of the study was to determine whether the use of Mn nanoparticles would make it possible to reduce the level of this micronutrient added to turkey diets without adversely affecting redox reactions in cells and epigenetic changes. The experiment was conducted on six groups with 10 replications, in a two-factor design with three dosages of manganese: 100, 50 and 10 mg/kg, and two sources: manganese oxide (MnO) and manganese nanoparticles (NP-Mn₂O₃). Markers of oxidative stress determined in the blood, that is, the concentration of lipid hydroperoxides, malondialdehyde, protein carbonyl derivatives, 3-nitrotyrosine, 8-hydroxydeoxyguanosine, total glutathione, superoxide dismutase, glutathione peroxidase, catalase, ceruloplasmin, total antioxidant status, albumin and vitamin C content. The level of epigenetic changes in the blood was determined by analysing global DNA methylation. In the experiment, in which the diet of turkeys was supplemented with two forms of Mn (MnO or NP-Mn₂O₃) at three dosages: 100, 50 and 10 mg/kg, the 10 mg/kg dose, especially in the form of NP-Mn₂O₃, induced lipid oxidation reactions to the greatest extent. Irrespective of the dosage of Mn in the turkey diet, Mn in the form of NP-Mn₂O₃ was found to reduce protein nitration more than Mn in the form of MnO. Reducing the Mn dosage in the diet from 100 to 50 mg/kg and then to 10 mg/kg is unfavourable because proportionally increases protein and DNA oxidation in cells, decreases the activity of antioxidant enzymes, and increases the level of glutathione. Reducing the dosage from 100 to 10 mg/kg increases global DNA methylation. The reduction of the Mn level, regardless of the form used, is disadvantageous, because it weakens the defense of the antioxidant system, which consequently can induce oxidative processes in the cells. Although Mn in the form of NP-Mn₂O₃ reduce protein nitration better than in MnO form, the use of manganese nanoparticles in turkey feeding (even in lower doses) requires further study.     

Influence of Substrate and Tissue Manganese on the IAA-Oxidase System in Cotton

Tissue manganese was found to influence the indoleacetic acid (IAA) system of cotton over a wide range of concentrations. The cofactor and inhibitor activities of the IAA-oxidase system were affected as the concentration of manganese in the tissue was varied. Maximum inhibitor activity was found in leaf extracts from the plants grown in 0.5 mg/l manganese (Hoagland's level). The inhibitor activity decreased in the leaf extracts of plants grown at concentrations of manganese either higher or lower than 0.5 mg/l. Abnormally high IAA-oxidase activity was found in the leaves of plants grown in deficient levels of manganese (<0.0005, 0.005 mg/l) and the extracts from plants in the <0.0005 mg/l Mn treatment showed IAA-oxidase cofactor activity.     

Effect of magnesium concentration in the culture medium on the trace element requirement of yeasts]

The effect of different magnesium concentrations in the culture liquid (ranging from 2=6 to 220 mg/l) on the accumulation of Mg and Mn ions in the yeast Candida guilliermondii was studied during their continuous cultivation on purified liquid paraffins. A reverse correlation between the accumulation of magnesium and manganese in the yeast biomass was established. The magnesium content in the biomass increased with an increase of its concentration in the nutrient medium. The biomass yield was optimal at a concentration of magnesium ions in the nutrient medium of 10=25 mg/l. Under these conditions the content of magnesium ions was 0.4 mg % and that of manganese ions (upon their concentration in the nutrient medium of 1=2 mg/l) was 20 mg%.     

Nutrient status and retention in pristine and disturbed wetlands in Uganda: management implications

Wetlands in Uganda experience different forms of human pressure ranging from drainage for agriculture and industrial development to over harvesting of wetland products. In order to develop sustainable management tools for wetland ecosystems in Uganda and the Lake Victoria Region, water quality analyses were carried out in a rural undisturbed (pristine) wetland (Nabugabo wetland in Masaka) and two urban wetlands that are experiencing human and urban development pressure (the Nakivubo wetland in Kampala and Kirinya wetland in Jinja). The former wetland forms the main inflow into Lake Nabugabo while the other two border the northern shore of Lake Victoria, Uganda. Nabugabo wetland buffers Lake Nabugabo against surface runoff from the catchment, while Nakivubo and Kirinya wetlands provides a water treatment function for wastewater from Kampala City and Jinja town respectively, in addition to buffering Lake Victoria against surface runoff. Water quality was assessed in all the wetland sites, and in addition nutrient content and storage was investigated in the main plant species (papyrus, Phragmites, Miscanthidium and cocoyam) in Nakivubo and Kirinya wetlands. A pilot experiment was also carried out to assess the wastewater treatment potential of both the papyrus vegetation and an important agricultural crop Colocasia esculenta (cocoyam). Low electrical conductivity, ammonium–nitrogen and ortho-phosphate concentrations were recorded at the inflow into Nabugabo wetland (41.5 μS/cm; 0.91 mg/l and 0.42 mg/l respectively) compared to the Nakivubo and Kirinya wetlands (335 μS/cm; 31.68 mg/l and 2.83 mg/l and 502 μS/cm; 10 mg/l and 1.87 mg/l respectively). The papyrus vegetation had higher biomass in Nakivubo and Kirinya wetlands (6.7 kg DW m⁻²; 7.2 kg DW m⁻² respectively), followed by Phragmites (6.5, 6.7), cocoyams (6.4, 6.6) and Miscanthidium (4.0, 4.2). The papyrus vegetation also exhibited a higher wastewater treatment potential than the agricultural crop (cocoyam) during the pilot experiment (maximum removal degree of ammonium–nitrogen being 95% and 67% for papyrus and yams). It was concluded that urbanisation pressure reduces natural wetland functioning either through the discharge of wastewater effluent or the degradation of natural wetland vegetation. It is recommended that wetland vegetation be restored to enhance wetland ecosystem functioning and for wetlands that are not yet under agricultural pressure, efforts should be made to halt any future encroachment.     

Accumulation and precipitation of Mn2+ by the cells of Oscillatoria terebriformis

The cyanobacterium Oscillatoria terebriformis was shown to exhibit resistance to high manganese concentrations, remaining viable at 2.5 mM MnCl₂ in the medium. Cyanobacterial cells were capable of considerable manganese consumption from the medium. The dynamics of Mn sorption by the cells were the same in all experimental variants, independent of the manganese concentration. Manganese concentration in the biomass peaked after 2–3 days and depended on Mn²⁺ concentration in the medium and on the amount of biomass introduced. In the case of O. terebriformis, manganese removed from the medium may be subdivided into Mn absorbed by the cell, Mn bound to the cell wall, Mn absorbed by the glycocalix, and chemically precipitated Mn. Of the total 21.25 ± 1.0 mg of consumed manganese, biological absorption and chemical precipitation were responsible for 11.78 ± 0.98 and 9.2 ± 0.8 mg, respectively. In the presence of cyanobacteria, Mn removal from the medium was 2.28 times higher than in the control. This process depended considerably on Mn sorption by exopolysaccharides. At 1.3 mM Mn²⁺, a lamellar mat was formed with interlayers of manganese carbonate.     

Deep placement of manganese fertiliser improves sustainability of lucerne growing on bauxite residue: A glasshouse study

Successful revegetation of bauxite residue sand (BRS) requires large inputs of nutrients such as manganese (Mn), yet Mn deficiency is still encountered, raising doubts about sustainable revegetation of BRS disposal areas. The application of deep placement of Mn, a measure common in agriculture, was examined as a method for improving productivity and sustainability when lucerne (Medicago sativa L.) is used as a species for BRS revegetation. In pots containing BRS, Mn was banded at 2.5-, 10- and 20-cm depths at rates of 10, 20 and 50 g g^–1 BRS. Two lucerne genotypes used were Salado, a Mn-deficiency-tolerant variety, and Sirosal, a Mn-deficiency-sensitive variety. Banding at 10-cm depth produced the best shoot growth of Sirosal at each Mn rate. Greatest shoot growth in Salado was found at 2.5-, 10- and 20-cm depths for 10, 20 and 50 g Mn g^–1 BRS, respectively. Deep banding 20 g Mn g^–1 BRS at 10-cm depth significantly increased lucerne growth compared with mixing through the profile. Banding at 20 cm produced Mn deficiency symptoms in lucerne during early growth, but symptoms were alleviated when sufficient amounts of roots proliferated in the banding zone. Dissolution and movement of Mn away from the fertiliser band were also investigated. In pots without plants, water throughput from watering twice weekly to 110% field capacity had no effect on the amount of extractable Mn at distances more than 1 cm away from the original Mn band position. Whilst not only providing a more effective supply of Mn for BRS revegetation over one growth period, deep-banding of adequate rates of Mn may also result in a longer residual value, reducing the need for frequent broadcast applications.     

Redox Dynamics of Arsenic Species in the Root‐Near Environment of Juncus effusus Investigated in a Macro‐Gradient‐Free Rooted Gravel Bed Reactor

In the framework of investigating the dynamics of As species within the planted soil beds of treatment wetlands, the redox dynamics of As species particularly in the root‐near environment of the rhizosphere were investigated. For this purpose, long‐term experiments were carried out using a specially designed macro‐gradient‐free rooted gravel bed reactor, planted with Juncus effusus to treat an artificial wastewater containing As (200 μg As/L). The exceptional quality of the biofilm processes at the helophyte root‐surfaces in treatment wetlands were of special importance in this investigation. The results showed that under C‐deficient conditions, a highly efficient As immobilization (> 85 %), obviously due to adsorption and/or co‐precipitation, was attained. The addition of organic carbon immediately caused an elevated As concentration and enrichment of As(III) (nearly 80 % of total As) in the reactor. Increasing the SO₄^2– concentration in the artificial wastewater inflow facilitated a high As immobilization (> 82 %) under sulfate reducing condition. In principle, a highly efficient microbial dissimilatory sulfate reduction contributed to S^2– formation and a greater As immobilization (most likely as As₂S₃) under C surplus and reducing conditions. Significant differences in As immobilization were observed by varying the inflow of the SO₄^2– concentration (0.2, 5, 10, 25 S/L) under C surplus conditions. More As(III) precipitates (15 % less in the outflow) when the inflow of the SO₄^2– concentration was decreased from 25 mg S/L to 10 mg S/L. Immobilized As showed greater instability by releasing As(V) (up to 85 % of total As) due to changes in the dynamic redox conditions inside the reactor. Re‐oxidation of reduced sulfur into other S species (e.g. S⁰, SO₄^2–) due to plant‐root mediated O₂ release probably caused an oxidative dissolution of already precipitated insoluble As (e.g. As₂S₃) and as a consequent As remobilization. The findings of this study highlighted the significance of SO₄^2– in relation to organic C supply in planted soil beds treating As‐contaminated wastewater under constructed wetland conditions.     

Coliform concentration reduction and related performance evaluation of a down-flow anaerobic fixed bed reactor treating low-strength saline wastewater

Low-strength saline wastewater may be generated by tourist facilities, industries and communities located in coastal areas. Sea salts, mostly chlorides, when present in wastewaters at high concentrations, can cause inhibition on biological treatment processes. In this study, a laboratory down-flow anaerobic fixed bed reactor (DFAFBR) was used for treating saline wastewater. This wastewater was simulated by dilution of piggery manure in a synthetic saline water to obtain a final total COD concentration in the range of 1100-2900 mg/l and a salt concentration of 15 g/l. The DFAFBR was operated at hydraulic retention times (HRT) of 96, 48, 24 and 12 h. The results showed that at sea salts concentrations in the range from 5 to 15 g/l, total coliform concentration reduction efficiencies higher than 97% were achieved. A decrease in the total and faecal coliform concentration reduction efficiencies from 99.5% to 90.5% and 92.5%, respectively, was observed when the HRT decreased from 96 to 12 h. Enumeration of coliform bacteria isolated from the biofilm in different zones of the reactor showed that more than 94% of the total amount was removed in the upper zone. A HRT of 24 h was required to obtain total COD, organic-N, total-P and faecal coliform concentration reduction efficiencies higher than 72%, 51%, 39% and 98%, respectively. A concentration of 8.4 g/l for chlorides, 1.25 g/l for sulphates and 4.6 g/l for sodium did not affect the process performance.     

Interferences between root plaque formation and phosphorus availability for isoetids in sediments of oligotrophic lakes

Freshwater isoetids exchanges a high proportion of the photosynthetically produced oxygen over the extensive root system and, therefore, they influence the redox potential (E_h) and phosphorus (P) availability in their sediments. Because isoetids rely on the sediment for P uptake, P may be a key element in controlling the distribution of isoetids. We investigated biomass and P availability to isoetids (Littorella uniflora and Isoetes lacustris) in a transect of five stations across the littoral zone in oligotrophic Lake Kalgaard, Denmark. At the two shallowest stations (0.6 and 1.0 m depth) the redox potential in the low organic rhizosphere sediment was high (>300 mV) and low concentrations of reduced exchangeable iron (Fe) and manganese (Mn) compounds in the sediment and of precipitated Fe and Mn oxides on isoetid roots (plaques) were found. The concentration of sediment P pools was low and so was isoetid P content and isoetid biomass. At intermediate water depth (1.8 m) sediment E_h was high (300 mV) and isoetids showed low root plaque concentrations. However, higher concentration of P pools in the rhizosphere was found at 1.8 m and isoetids showed the highest P content and biomass. At deeper stations (2.8 and 4.6 m depth) E_h was low (<100 mV) in the high organic rhizosphere and high concentrations of plaques were found. The P content in the sediment was high, however, isoetids showed low biomass and low P content. We suggest that the low P content in isoetids growing on P rich organic sediments is partly due to inhibition of the P uptake because of adsorption of P to the oxidized Fe and Mn plaques. However, ratios between oxidized Fe and Fe-bound P, 150 for plaques and 40 for sediment, suggest the isoetids are able to access some of the P that is bound in the plaques. The pools of dissolved P in the porewater were 25–1100 times lower than the estimated annual P requirement for net growth of isoetids while solid fraction P pools were 20–260 times higher than the estimated annual P requirement. Clearly, the oxygen release from isoetid roots decreases the availability of P either by keeping the entire rhizosphere oxidized (low organic sediments) or by the formation of root plaques (high organic sediments).     

Color removal ability of <Emphasis Type="Italic">Phanerochaete chrysosporium</Emphasis> in relation to lignin peroxidase and manganese peroxidase produced in molasses wastewater

Decolorization of molasses wastewater (MWW) from an ethanolic fermentation plant by Phanerochaete chrysosporium was studied. By diluting MWW properly (10%v/v) and incubating it with an appropriate concentration of the spores (2.5 × 10⁶/ml), extensive decolorization occurred (75%) on day 5 of the incubation. The colour removal ability was found to be correlated to the activity of ligninolytic enzyme system: lignin peroxidase (LiP) activity was 185 U/l while manganese peroxidase (MnP) activity equaled 25 U/l. Effects of some selected operating variables were studied: manganese(II), veratryl alcohol (VA), glucose as a carbon source and urea and ammonium nitrate, each as a source of nitrogen. Results showed that the colour reduction and LiP activity were highest (76% and 186 U/l, respectively) either when no Mn(II) was added or added at the lowest level tested (0.16 mg/l to provide 0.3 mg/l). Activity of MnP was highest (25 U/l) when Mn(II) added to the diluted MWW at the highest level (100 ppm) while activity of LiP was lowest (7.1 U/l) at this level of added Mn(II). The colour reduction in the presence of the added VA was shown to be little less than in its absence (70 vs. 75%). When urea as an organic source of nitrogen for the fungus, was added to the MWW, the decolorizing activity of P. chrysosporium decreased significantly (15 vs. 75%) and no activities were detected for LiP and MnP. Use of ammonium nitrate as an inorganic source of nitrogen did not show such a decelerating effects, although no improvements in the metabolic behavior of the fungus (i.e., LiP and MnP activities) deaccelerating was observed. Effects of addition of glucose was also discussed.     

Long-term performance of bioreactors cleaning mercury-contaminated wastewater and their response to temperature and mercury stress and mechanical perturbation

The long-term performance of bioreactors retaining mercury from contaminated industrial wastewater was analyzed at the laboratory scale, and its response to mechanical perturbations (gas bubbles and shaking) as well as to physical (increased temperature and hydraulic load) and chemical stresses (increased mercury concentration) likely to occur during on site operation was studied. Two packed-bed bioreactors with 80-cm(3) lava chips as biofilm carrier were inoculated with nine Hg(II)-resistant natural isolates of alpha- and gamma-proteobacteria. Chloralkali wastewater containing ionic mercury (3.0 to 9.7 mg/L Hg(2+)), amended with sucrose and yeast extract, flowed through the bioreactors at 160 mL/h. During the 16-month investigation the bioreactors showed no sign of depleted performance in terms of mercury-retaining capacity. After 16 months, both bioreactors still retained 96% of the mercury load. The performance of the bioreactors was sensitive to mechanical perturbations (e.g., sheer forces of gas bubbles). Shifts to higher Hg(2+) inflow concentrations initially decreased the mercury retention efficacy slightly. However, the bioreactors could adapt to Hg(2+) concentrations of up to 7.6 mg/L within several days. Old biofilms were less affected than the younger ones. The performance of the bioreactors was not affected by an increase in temperature up to 41 degrees C and an increased volumetric load (up to 240 mL/h). The bioreactors regained activity spontaneously after the stress had stopped. Recovery could be accelerated by increased nutrient concentration, although this may lead to blocking of the packed bed.     

Determination of the oxidation states of manganese in brain, liver, and heart mitochondria

Excess brain manganese can produce toxicity with symptoms that resemble those of Parkinsonism and causes that remain elusive. Manganese accumulates in mitochondria, a major source of superoxide, which can oxidize Mn2+ to the powerful oxidizing agent Mn3+. Oxidation of important cell components by Mn3+ has been suggested as a cause of the toxic effects of manganese. Determining the oxidation states of intramitochondrial manganese could help to identify the dominant mechanism of manganese toxicity. Using X-ray absorbance near edge structure (XANES) spectroscopy, we have characterized the oxidation state of manganese in mitochondria isolated from brain, liver, and heart over concentrations ranging from physiological to pathological. Results showed that (i) spectra from different model manganese complexes of the same oxidation state were similar to each other and different from those of other oxidation states and that the position of the absorption edge increases with oxidation state; (ii) spectra from intramitochondrial manganese in isolated brain, heart and liver mitochondria were virtually identical; and (iii) under these conditions intramitochondrial manganese exists primarily as a combination of Mn2+ complexes. No evidence for Mn3+ was detected in samples containing more than endogenous manganese levels, even after incubation under conditions promoting reactive oxygen species (ROS) production. While the presence of Mn3+ complexes cannot be proven in the spectrum of endogenous mitochondrial manganese, the shape of this spectrum could suggest the presence of Mn3+ near the limit of detection, probably as MnSOD.     

Metal biosorption in lignocellulosic biofuel biorefinery effluent: an initial step towards sustainability of water resources

Biosorption of metals by microorganisms is a promising technology to remove accumulated non-process elements in highly recycled biorefinery process water. Removal of these elements would enable greater water reuse and reduce the environmental impact of effluent discharge. A model lignocellulosic ethanol biorefinery wastewater was created based on pulp mill effluent. This generated a wastewater with an environmentally realistic high loading of dissolved natural organic matter (900?mg/l), a potentially important factor influencing metal biosorption. Analysis of feedstock and pulp mill effluent indicated that Mn and Zn are likely to be problematic in highly recycled lignocellulosic ethanol biorefinery process water. Therefore, the growth of several bacteria and fungi from existing collections, and some isolated from pulp mill effluent were tested in the model wastewater spiked with Mn and Zn (0.2?mM). Wastewater isolates grew the best in the wastewater. Metal uptake varied by species and was much greater for Zn than Mn. A bacterium, Novosphingobium nitrogenifigens Y88(T), removed the most metal per unit biomass, 35 and 17?mg?Mn/g. No other organism tested decreased the Mn concentration. A yeast, Candida tropicalis, produced the most biomass and removed the most total metal (38?% of Zn), while uptake per unit biomass was 24?mg?Zn/g. These results indicate that microorganisms can remove significant amounts of metals in wastewater with high concentrations of dissolved natural organic matter. Metal sorption by autochthonous microorganisms in an anaerobic bioreactor may be able to extend water reuse and therefore lower the water consumption of future biorefineries.     

The effect of dietary protein source on manganese bioavailability to the rat

Rats were fed diets containing 20% protein from casein, beef, chicken, tuna, or soybean. All diets contained 15% fat and were supplemented with limiting amino acids as necessary to meet National Research Council requirements. In Experiment 1, the manganese content of all diets was the same; manganese content was 5 mg/kg. In Experiment 2, a basal (adequate) level of minerals was provided in each diet but total mineral content varied depending on the contribution of the protein source; manganese was added to achieve a concentration of 5 mg/kg. In both experiments, 54Mn absorption was greatest from tuna (8.54% and 7.71%) and least from beef (4.57% and 4.14%) (P less than 0.0001). In both experiments, biologic half-life of 54Mn was longest in rats fed beef (18.5 and 26.9 days) and shortest in rats fed soy (14.5 and 16.2 days) (P less than 0.0002). Except for beef, biologic half-life was similar for dietary groups between the two experiments. In Experiment 1, only kidney manganese concentration was significantly affected by diet and was highest in soy-fed animals. In Experiment 2, plasma, kidney, and liver manganese were all significantly affected by diet and were highest in soy-fed animals and lowest in beef-fed animals.     

Regulation of Mn-SOD activity in the mouse heart: glucose effect

Intraperitoneal injection of glucose was found to cause a dose and time dependent suppression of superoxide dismutase activity in mouse heart. Manganese superoxide dismutase was more sensitive to glucose suppression than Cu-Zn superoxide dismutase. While glucose suppressed the Mn form of the enzyme at the concentration of 1.5 mg/kg, it did not have a significant effect on Cu-Zn superoxide dismutase activity at this concentration. The maximum suppression for both forms of superoxide dismutase activity occurred at 4.5 mg/kg. Glucose also suppressed manganese superoxide dismutase activity in mouse heart for a longer period of time compared to Cu-Zn superoxide dismutase. Glucose suppression also occurred in mouse brain. The glucose suppression effect on manganese superoxide dismutase activity in the heart was partially alleviated by X-irradiation.     

Origin and composition of settling iron aggregates in oligotrophic Sombre Lake, Signy Island, Antarctica

Sediment traps were deployed in an oligotrophic, seasonally anoxic maritime Antarctic lake for 15 months. Immediately after the onset of the inflow in spring many iron oxyhydroxide aggregates were collected in the traps. Image analysis, scanning electron microscopy and energy dispersive X-ray analysis were used to examine the aggregates.The aggregates consisted of primary particles that persisted in the aggregates. The mean diameter of the aggregates was constant with depth. The aggregates consisted predominantly of iron, phosphorus and oxygen but calcium was also an important constituent. Significant concentrations of manganese and sodium were also detected. The molar ratio Fe:P remained constant at 4:1 as did the ratio Fe:Ca at 52:1. The concentration of iron, phosphorus and calcium in the aggregates increased with depth, whilst the concentration of manganese decreased with depth in parallel with a gradient of increasing anoxia.The stable water column formed under ice cover and the temporal and spatial data provide evidence that the Fe:P and Fe:Ca ratios are constant and characteristic of the aggregates, whilst the overall composition of the aggregates is more dynamic and dependant on redox conditions and water chemistry.     

硫酸盐还原一甲烷化两相厌氧消化系统运行工艺条件的研究

以合成废水为基质,研究了采用硫酸盐还原-甲烷化两相厌氧新型工艺处理含高浓度硫酸盐有机废水的系统运行工艺条件.结果表明,酸化-硫酸盐还原反应器的适宜pH为6.5-7.0;500mg/l的S~(2-)使SRB的硫酸盐还原活性下降;208mg/l的[H_2S]_L抑制MPB活性的95.4%;推导出估算气提塔出水回流比R的模型;以得到的工艺条件为依据处理了含19200mg/1的SO_4~(2-)和29400mg/l COD的味精废水.