Search

Marine sediments constitute the world's most substantial long-term carbon repository. The microorganisms dwelling in these sediments mediate the transformation of fixed oceanic carbon, but their contribution to the carbon cycle is not fully understood. Previous culture-independent investigations into sedimentary microorganisms have underscored the significance of carbohydrates in the carbon cycle. In this study, we employ a metagenomic methodology to investigate the distribution and abundance of carbohydrate-active enzymes (CAZymes) in 37 marine sediments sites. These sediments exhibit varying oxygen availability and were isolated in diverse regions worldwide. Our comparative analysis is based on the metabolic potential for oxygen utilisation, derived from genes present in both oxic and anoxic environments. We found that extracellular CAZyme modules targeting the degradation of plant and algal detritus, necromass, and host glycans were abundant across all metagenomic samples. The analysis of these results indicates that the oxic/anoxic conditions not only influence the taxonomic composition of the microbial communities, but also affect the occurrence of CAZyme modules involved in the transformation of necromass, algae and plant detritus. To gain insight into the sediment microbial taxa, we reconstructed metagenome assembled genomes (MAG) and examined the presence of primary extracellular carbohydrate active enzyme (CAZyme) modules. Our findings reveal that the primary CAZyme modules and the CAZyme gene clusters discovered in our metagenomes were prevalent in the Bacteroidia, Gammaproteobacteria, and Alphaproteobacteria classes. We compared those MAGs to organisms from the same taxonomic classes found in soil, and we found that they were similar in its CAZyme repertoire, but the soil MAG contained a more abundant and diverse CAZyme content. Furthermore, the data indicate that abundant classes in our metagenomic samples, namely Alphaproteobacteria, Bacteroidia and Gammaproteobacteria, play a pivotal role in carbohydrate transformation within the initial few metres of the sediments. [ABSTRACT FROM AUTHOR]

X-Ray diffraction results for the study mine are mainly represented by two phases (phosphatic and non-phosphatic). First phase is represented by apatite (fluorapatite) which is the dominant. The second phase includes carbonate minerals; calcite, dolomite, evaporated mineral (gypsum), sulphide mineral (pyrite), in addition to quartz as a silicate mineral. These results are confirmed by the petrographic study. The detailed microscopic examinations indicate that the phosphorites at the study mine is essentially composed of phosphatic lithoclasts (mainly collophane), phosphatic bioclasts (bone fragments, spines and teeth of vertebrates such as shark fish as well as coprolites), opaques, and quartz embedded in a microcrystalline phosphatic matrix (contains some of dahllite) associated with a microcrystalline quartz according to their decreasing order of abundance. The paragenetic sequence of the studied phosphorites is as follows: fluorapatite, collophane then followed by dahllite. The redox-sensitive trace elements, its ratios, authigenic uranium as well as Fe/Ti can be signifying the redox conditions. Also, they revealed that the study rocks are deposited under the oxic to anoxic environment coupled with hydrothermal solution. The trace and rare earth elements are generally associated with phosphatic rocks. Thus, the phosphatic rocks of Um El-Huwtat mine, Quseir can be considered as sources of trace and rare earth elements. Also, pyrite can be considered as another possible source for REEs. The studied phosphatic rocks characterized by light REE (LREE = 69 ppm) enrichment than heavy REE (HREE = 25 ppm). All the recoded values of the heavy metals for the study mine are higher than those in Tunisia (400.3 ppm), Morocco (571.75 ppm) and Jordan (187 ppm). The post-depositional conditions are responsible for the enrichment of U and Th and/or intensive chemical weathering in Quseir area. Enrichment Factor (EF) indicated that the enrichment or deletion of the elements may be a function of that association and the origins of the various phosphate fractions. The studied phosphatic rocks are suitable for industrialized fertilizers according to the world guides. [ABSTRACT FROM AUTHOR]

A hybrid system of a sequential oxic-anoxic bioreactor and a fluidized immobilized cell carbon oxidation with Kaldnes K1 as supporting material and activated carbon were used to evaluate the removal efficiencies for biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) from domestic wastewater collected at the entrance of the biological reactor from a municipal wastewater treatment plant. The laboratory-scale hybrid biofilm treatment system was fabricated with 5 mm acrylic sheets, the effective volume of the system was 31.6 L. The operation of the treatment system was carried out with an optimal hydraulic retention time of 31.33 h and flow rate of 15 mL/min for 170 d at a mean temperature of 20°C, the pH of the wastewater was between 6.54 and 7.50, and a variable organic loading rate from 0.077 to 1.13 kg BOD5 /(m³d) depending on the daily influent wastewater to the wastewater treatment plant. The means removal efficiencies in the 170 d of operation achieved for BOD5, COD, TN, TP were between 84%–99%, 80%–97%, 24%–97% and 21%–94%, respectively. [ABSTRACT FROM AUTHOR]

The geochemical investigation of trace metals in crude oils from some producing oil fields in the Niger Delta, Nigeria, was carried out to ascertain the petroleum source rocks and organic matter deposits. The concentrations of trace metals in crude oil samples obtained from eight producing fields from Niger Delta, Nigeria, were analyzed using a 700 model Perkin Elmer atomic absorption spectrophotometer. The results showed the following ranges for the trace metals: Cu (0.01-0.04 mg/kg), Fe (0.05-5.90 mg/kg), Ni (0.09-0.72 mg/kg); and V (0.008-1.05 mg/kg). Pb and Zn were lower than 0.01 mg/kg. Trace metal ratios such as V/Ni, V/Fe, and (V/V + Ni) were used to unravel the genetic correlation among the oils. All the crude samples except the sample from Nembe South-2 have a V/N ratio lower than 1.0, indicating that the organic materials produced the petroleum source rock. A cross plot of V/Ni revealed two genetic families for the crude oils, derived from a terrestrial and marine origin, which was confirmed by the ternary plot of V, Ni, and Fe, discriminating the crude oils from the producing fields into two distinct groups. The V/(Ni + V) of smaller than 0.5 showed that most crude oils were deposited in an oxic environment. A cross-plot of V/(Ni + V) and V/Fe showed a weak correlation, suggesting that it could not substitute for the V/Ni ratio in determining the origin and depositional environment of crude oil samples. Therefore, an in-depth knowledge of the concentration of trace metals, especially vanadium and nickel, within an environment during oil exploration is essential in developing new oil locations. [ABSTRACT FROM AUTHOR]

The flux of soluble reactive phosphorus (SRP) was estimated under simulated oxic, anoxic and aerated conditions in sediment cores collected from two sites in a meso-eutrophic reservoir that differ in depth and limnological characteristics. Hypolimnetic accumulation and the concentration of P in various sediment fractions were also studied to determine the factors and processes influencing SRP flux at the sediment-water interface. The average release of SRP under anoxic incubation varied between 16 - 70 µmol/m2/day and 20 - 94 µmol/m2/day in shallow and deep-water sites respectively. On the other hand, SRP was almost entirely lost to the sediment during simulated oxic or aerated experiments. Temperature influence on P release from the sediment was significant and the increment is considerable at water temperature above 20oC. The reservoir sediment contained a large proportion of iron and aluminum bound P (Fe and Al-P). Fe and P ratio in the sediment exceeded 15 indicating high retention capacity of P by the sediment. Besides, the high amount of Fe and Al-P in the sediment reflects redox dependent P mobilization. Therefore, management needs targeting retention capacity of the sediment and alteration of anoxic condition in the hypolimnion during warmer months.

Abstract Background A key characteristic of eutrophication in coastal seas is the expansion of hypoxic bottom waters, often referred to as ‘dead zones’. One proposed remediation strategy for coastal dead zones in the Baltic Sea is to mix the water column using pump stations, circulating oxygenated water to the sea bottom. Although microbial metabolism in the sediment surface is recognized as key in regulating bulk chemical fluxes, it remains unknown how the microbial community and its metabolic processes are influenced by shifts in oxygen availability. Here, coastal Baltic Sea sediments sampled from oxic and anoxic sites, plus an intermediate area subjected to episodic oxygenation, were experimentally exposed to oxygen shifts. Chemical, 16S rRNA gene, metagenomic, and metatranscriptomic analyses were conducted to investigate changes in chemistry fluxes, microbial community structure, and metabolic functions in the sediment surface. Results Compared to anoxic controls, oxygenation of anoxic sediment resulted in a proliferation of bacterial populations in the facultative anaerobic genus Sulfurovum that are capable of oxidizing toxic sulfide. Furthermore, the oxygenated sediment had higher amounts of RNA transcripts annotated as sqr, fccB, and dsrA involved in sulfide oxidation. In addition, the importance of cryptic sulfur cycling was highlighted by the oxidative genes listed above as well as dsvA, ttrB, dmsA, and ddhAB that encode reductive processes being identified in anoxic and intermediate sediments turned oxic. In particular, the intermediate site sediments responded differently upon oxygenation compared to the anoxic and oxic site sediments. This included a microbial community composition with more habitat generalists, lower amounts of RNA transcripts attributed to methane oxidation, and a reduced rate of organic matter degradation. Conclusions These novel data emphasize that genetic expression analyses has the power to identify key molecular mechanisms that regulate microbial community responses upon oxygenation of dead zones. Moreover, these results highlight that microbial responses, and therefore ultimately remediation efforts, depend largely on the oxygenation history of sites. Furthermore, it was shown that re-oxygenation efforts to remediate dead zones could ultimately be facilitated by in situ microbial molecular mechanisms involved in removal of toxic H2S and the potent greenhouse gas methane.

Abstract Redox-sensitive elements (Mo, V, U, Re, Cd, Co, As, Sb, Tl, Ni, Cr, Mn, Fe, Pb, Cu, Zn, Se) and proxies for detrital clastic sedimentation (Al, Ti, Sc, Th) along with total organic carbon (TOC) and total sulfur (TS) were analysed to constrain the paleoredox conditions of the Middle-Upper Jurassic black shales in the Blue Nile (Abay) Basin, Ethiopia. These samples were collected from the deep marine Antalo Limestone (Oxfordian-Kimmeridgian), Gohatsion Formation (Bathonian) and glauconitic shale-mudstone unit (Aalenian-Toarcian). Significant variations in redox-sensitive elements concentration within and between these shales were evident for variable redox conditions. In general, the concentration of proxies for detrital clastic sedimentation increases from the Antalo Limestone to Gohatsion Formation and further to glauconitic shale-mudstone unit shales, respectively. The Antalo Limestone shales show slightly higher enrichment in redox-sensitive elements than the Gohatsion Formation and glauconitic shale-mudstone unit shales. The Antalo Limestones shales have higher TOC content than the glauconitic shale-mudstone unit shales and become very low in the Gohatsion Formation shales. The TS content in contrast, is relatively lower in the Antalo Limestone shales, intermediate in the Gohatsion Formation shales and becomes higher in the glauconitic shale-mudstone unit shales. The Antalo Limestone shales were deposited under anoxic-suboxic conditions whereas the Gohatsion Formation and glauconitic shale-mudstone unit shales were deposited under suboxic-oxic conditions. The TOC content and redox conditions of the Antalo Limestone shales implies favourable organic matter preservation and future source rock explorations in the basin should be targeted there. Highlights • Redox sensitive elements were used to examine the paleoredox conditions. • The Antalo Limestones shales have higher TOC content. • The Antalo Limestone shales show higher redox-sensitive elements enrichment. • The Antalo Limestone shales were deposited under suboxic to anoxic conditions. [ABSTRACT FROM AUTHOR]

Bu çalışmada Bolu ili Göynük ilçesi Hatıldağ sahasında yer alan Kabalar formasyonu bitümlü kayaçlarındaki (bitümlü şeyl, bitümlü kiltaşı ve bitümlü marn) element zenginleşmelerinin belirlenmesi ve ekonomik açıdan maden yatağı olabilirliği araştırılmıştır. Element Analizleri ICP-ES (ICP emission spectrometry) ve ICP-MS (ICP mass spectrometry) teknikleri ile yapılmıştır. Kayaçlardaki organik karbon miktarları ise Rock-Eval VI cihazı ile analiz edilmiştir. Formasyondan ölçülen Kayalık Dere ÖSK’sından alınan 28 adet bitümlü kayaç- da yapılan piroliz analizlerinde Corg minumum 0.40 %wt, maksimum 8.25 %wt olup, Corg ortalaması 3,6 %wt’dır. Tespit edilen ana ve iz elementler dünya çapında anoksik koşullarda depolandığı bilinen Peru Kıyısal Şelfi Sedimanları, Namibya Kıyısal Şelfi Sedimanları, Kaliforniya Körfezi Sedimanları, Akdeniz Sapropelleri, Karadeniz Sapropelleri, Senomaniyen/ Turoniyen (C/T) Demerara Yükselimi Anoksik Sedimanları ve C/T Gubbio Anoksik Sedimanlarına ait ana ve iz element değerleri ile kıyaslanmıştır. İncelenen örneklerde ana ve iz element konsantrasyonlarının ortalama şeyle göre zenginleşmeleri belirlenmiştir. Kayalık Dere ÖSK’sında ana elementlerden Fe, Mg, Ca ve K, iz elementlerden ise As, Ba, Co, Cu, Ni, Rb, Sr, V, Zn ve Zr’nun kıyaslanan havzalara göre daha fazla zenginleştiği görülmüştür. Örneklerimizdeki Ca, Mg ve Ba gibi elemetlerin diğer ortamlardan yüksek çıkması depolanma ortamımızın daha karbonatlı ve suboksik olduğunu göstermektedir.

In this study, a lab scale different activated sludge configurations methods were used to treat a municipal wastewater from effluent of; primary sedimentation tank of Al-Rustamiya wastewater treatment plant located near Baghdad city to remove organic load, nitrogen and phosphorus from the period of 15 July 2012 to 22 May 2013.Biological treatment systems were conventional activated sludge (CAS) , extended aeration , anaerobic-anoxic-aerobic( A2O) , anoxic-aerobic (MLE) and anaerobic –oxic(A/O). During the operation periods, the average removal efficiency of BOD5, COD and TSS is 81.9, 77.7 and 85.8 respectively regardless of the fluctuation in influent quality. In addition the results show removal efficiency of ammonia, nitrate, nitrite and phosphorus with ranges (61-85.8), (34-81.7) , (35-81.4) (32.3-85.54) % respectively. The biological treatment systems produced high quality effluent which can achieve the Iraqi limitations of rivers maintenance for all measured parameters.

The objective of this study is the evaluation of the operation of two reactors by sequential batches (SBR), the first using suspended biomass and the second using granular biomass, both for the elimination of organic matter and nitrogen from the effluent of the same tannery. To evaluate the operation of both reactors in the removal of organic matter and nutrients in the effluent, the following stages were carried out: a) information collection, b) data processing and c) obtaining results. It is concluded that the rate of removal of COD in an SBR for cycle lengths of 6, 12 and 24 hours using biomass suspended under aerobic conditions was smaller than the rate of removal of the granular biomass. The NH4 + -N is removed with an efficiency varying between 90 and 97% for a cycle time of 12 hours achieving the total removal of NH4+ -N for cycle times estimated between 12.39 and 13.25 hours. [ABSTRACT FROM AUTHOR]

Wastewater streams containing hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) are subject to regulatory discharge regulations that require processing through industrial waste treatment. Thus, the development of easy-to-apply technologies for the treatment of RDX-laden wastewater streams is imperative. In the present study, the reduction of RDX by granular zero valent iron (GZVI) in batch and column experiments was investigated. Preliminary batch tests conducted under both oxic and anoxic conditions showed that after 3.0 h of reaction with GZVI, RDX was mainly converted to formaldehyde (CH2O), nitrate (NO3−), and ammonium (NH4+). Column filtration tests showed that pretreatment of the GZVI media with acid wash and low influent pH (4.0 ± 0.1) achieved 99% removal of RDX up to 5000 bed volume. BOD tests carried out on the post-treatment streams showed increased biodegradability of the treated wastewater, leading to a lower environmental impact for the final waste. [ABSTRACT FROM AUTHOR]

The flux of soluble reactive phosphorus (SRP) was estimated under simulated oxic, anoxic and aerated conditions in sediment cores collected from two sites in a meso-eutrophic reservoir that differ in depth and limnological characteristics. Hypolimnetic accumulation and the concentration of P in various sediment fractions were also studied to determine the factors and processes influencing SRP flux at the sediment-water interface. The average release of SRP under anoxic incubation varied between 16 - 70 µmol/m2/day and 20 - 94 µmol/m2/day in shallow and deep-water sites respectively. On the other hand, SRP was almost entirely lost to the sediment during simulated oxic or aerated experiments. Temperature influence on P release from the sediment was significant and the increment is considerable at water temperature above 20°C. The reservoir sediment contained a large proportion of iron and aluminum bound P (Fe and Al-P). Fe and P ratio in the sediment exceeded 15 indicating high retention capacity of P by the sediment. Besides, the high amount of Fe and Al-P in the sediment reflects redox dependent P mobilization. Therefore, management needs targeting retention capacity of the sediment and alteration of anoxic condition in the hypolimnion during warmer months. [ABSTRACT FROM AUTHOR]

This paper presents the characteristics of sediment from core BS-36 (6°55.85’ S and 96°7.48’ E, 1147.1 m water depth) that was acquired in the Mergui Basin, Andaman Sea. The analyses involved megascopic description, core scanning by multi-sensor core logger, and carbonate content measurement. The purpose of this study is to determine the physical and chemical characteristics of sediment to infer the depositional environment. The results show that this core can be divided into 5 lithologic units that represent various environmental conditions. The sedimentation of the bottom part, Units V and IV were inferred to be deposited in suboxic to anoxic bottom condition combined with high productivity and low precipitation. Unit III was deposited during high precipitation and oxic condition due to ocean ventilation. In the upper part, Units II and I occurred during higher precipitation, higher carbonate production and suboxic to anoxic condition. Keywords: sediment characteristics, Mergui Basin, Andaman Sea, suboxic, anoxic, oxic, carbonate content

The Baltic Sea has undergone severe eutrophication during the last century, resulting in increased algal blooms and the development of hypoxic bottom waters. In this study, we sampled oxygen deficient sediment cores from a Baltic Sea coastal bay and exposed the bottom water including the sediment surface to oxygen shifts via artificial addition of air during laboratory incubation. Surface sediment (top 1 cm) from the replicate cores were sliced in the field as well as throughout the laboratory incubations and chemical parameters were analyzed along with high throughput sequencing of community DNA and RNA. After oxygenation, dissolved iron decreased in the water overlying the sediment while inorganic sulfur compounds (thiosulfate and tetrathionate) increased when the water was kept anoxic. Oxygenation of the sediment also maintained RNA transcripts attributed to sulfide and sulfur oxidation as well as nitrogen fixation in the sediment surface. Based on 16S rRNA gene and metatranscriptomic analyses it was found that oxygenation of the sediment surface caused a bloom of the Epsilonproteobacteria genus Arcobacter. In addition, the formation of a thick white film was observed that was likely filamentous zero-valent sulfur produced by the Arcobacter spp. Based on these results, sulfur cycling and nitrogen fixation that were evident in the field samples were ongoing during re-oxygenation of the sediment. These processes potentially added organic nitrogen to the system and facilitated the re-establishment of micro- and macroorganism communities in the benthic zone.

The application of an anoxic/oxic sequencing batch reactor (SBR) system for treatment of synthetic textile wastewater containing Direct Blue 15 (STWW + DB15) was carried out to observe the DB15 biodegradation mechanism and its intermediates. The effect of various NaCl concentrations on the system removal efficiency was also investigated. The results showed that NaCl had a more repressive effect on the growth and activity of heterotrophic carbonaceous compound removal bacteria than on nitrogenous compound removal bacteria (both nitrifying and denitrifying bacteria). The highest biochemical oxygen demand (BOD5 ), chemical oxygen demand (COD), DB15, total nitrogen (TN) and total Kjeldahl nitrogen (TKN) removal efficiencies of 96.29% ± 0.74%, 95.81% ± 0.30%, 90.61% ± 0.82%, 87.9% ± 0.24% and 85.03% ± 0.20%, respectively, were detected for STWW + DB15 at hydraulic retention time of 3 d and mixed liquor suspended solids of 2,000 mg/L. The lowest BOD5, COD, DB15, TN and TKN removal efficiencies of 30.01% ± 3.48%, 33.26% ± 0.92%, 26.93% ± 1.42%, 51.49% ± 0.31% and 49.77% ± 0.87%, respectively, were detected for STWW + DB15 containing 14% NaCl (w/v). Moreover, NaCl had a stronger repressive effect on nitrifying bacteria than on denitrifying bacteria. Observation of the biodegradation mechanism of DB15 in the anoxic/oxic SBR system revealed that the azo bond of DB15 was first degraded to 1-amino-8-naphthol-3,6-disulfonic acid and 2-ethoxy-4-methylaniline at the anoxic period of the reaction step, and then 1-amino-8-naphthol-3,6-disulfonic acid was further degraded to 2-naphthol at the oxic period of the reaction step. [ABSTRACT FROM AUTHOR]

The efficiency and bacterial diversity of bio-sludge in oxic-sequencing batch reactor (SBR) and anoxic/oxic-SBR systems with synthetic industrial estate wastewater without heavy metals (SIWW) and SIWW containing 3.0 mg/L of Cr3+ or Ni2+ (SIWW + Cr3+ or SIWW + Ni2+) at a mixed liquor suspended solids of 2,000 mg/L and a hydraulic retention time of 1.5 d were investigated. The highest Ni2+ and Cr3+ removal efficiencies of 93.1% ± 0.9% and 95.4% ± 0.2%, respectively, were detected in anoxic/oxic-SBR systems with SIWW + Cr3+ and SIWW + Ni2+, respectively. The average Cr3+ and Ni2+ adsorption abilities of bio-sludge from the anoxic/oxic-SBR system were 24.0 ± 5.0 mg Ni2+/g bio-sludge and 20.0 ± 4.0 mg Cr3+/g bio-sludge, respectively. In addition, 3.0 mg/L of Cr3+ or Ni2+ had a strong repressive effect on the growth and activity of heterotrophic carbonaceous biochemical oxygen demand removal bacteria. However, the addition of an anoxic period in the reaction step increased heavy metal removal efficiency as a result of denitrifying bacteria. The other advantage of the anoxic/oxic-SBR system was that it showed high nitrogenous compound removal yields. To observe bacterial diversity in the anoxic/oxic-SBR system during operation, rDNA analysis technique was applied. It was found that the addition of 3.0 mg/L of Cr3+ or Ni2+ did not show significant negative effects on nitrifying and denitrifying bacteria, but some species disappeared from the system, particularly nitrifying bacteria, under anoxic conditions. [ABSTRACT FROM AUTHOR]

The effects of mixed liquor suspended solids (MLSS), hydraulic retention time (HRT) and anoxic:oxic ratio on the sequencing batch reactor (SBR) system efficiency with synthetic textile industrial wastewater (STIW) containing direct dyes were investigated. The results showed that the system had the highest removal efficiency at MLSS of up to 2,500 mg/L. Moreover, its efficiency was increased with the increase of HRT or decrease of organic loading rate. To increase the nitrogenous compounds removal efficiencies, the reaction step of SBR operation should be modified by adding the anoxic period. The optimal operation conditions of the SBR system for highest nitrogen and textile dye removal efficiencies were MLSS of 2,500 mg/L, HRT of 7.5 d (organic loading rate of 0.11 kg BOD5/m3-d) and anoxic:oxic ratio of 15:4. The system showed the highest direct red 23 and direct blue 15 removal efficiencies of 90.61% ± 2.14% and 83.82% ± 2.60%, respectively, resulting from the activity of denitrifying bacteria. [ABSTRACT FROM AUTHOR]

Abstract: This study characterizes the effect of oxygen in the abiotic transformation of estrogens when they are contacted with a surrogate of the vegetable wastes found in sewage. 17β-Estradiol (E2) and 17β-14C4-estradiol (14C-E2) were utilized as model compounds. Batch experiments were run under both oxic and anoxic conditions. In order to accomplish an accurate mass balance of the target estrogen, two analyses were performed simultaneously: first, radioactivity counting, and second, quantitation of E2 and 14C-E2, as well as their transformation product estrone and 14C4-estrone, by Liquid Chromatography tandem Mass Spectrometry. Under oxic conditions, the total concentration of 14C-E2 was found to decrease by 78% in 72h (15% and 7% remained in the liquid and solid phases, respectively). Conversely, when the estrogens were contacted with the synthetic influent under anoxic conditions, E2 was quantitatively recovered after 72h (70% and 22% in aqueous and solid matrices, correspondingly). These results suggest that when the concentration of dissolved oxygen is null or limited, catalysis through an oxidative coupling mechanism is halted. Moreover, it was confirmed that the catalytic reaction occurred solely in the presence of the solid phase of the model vegetable matter. [Copyright &y& Elsevier]

In this study, a cascade of anoxic and oxic fluidized bed biofilm reactors system was carried out to treat synthetic municipal wastewater. The parameters of the influent flow rates and C/N ratios were discussed. System performance was acceptable for chemical oxygen demand (COD), ammonia, and total nitrogen removal. A decrease of ammonia and total nitrogen removal efficiencies, however, was observed when the influent flow rates increased to 5.04 and 6.12 1 h-1. Total nitrogen removal decreased at the influent C/N ratio of 3:1. The measured ratios of COD reduction in the anoxic column to nitrogen removal through nitrification-denitrification were 3.7, 3.5, 3.3, and 3.1 g COD/g-1 N on average when the influent C/N ratios changed from 6:1 to 3:1. The observed sludge yield (Yobs) was 0.169 g VSS g COD-1 because of perfect denitrification in the anoxic column and the relatively long solids retention time. [ABSTRACT FROM AUTHOR]

Abstract: We analyzed the chemical composition of suspended matter from the Black Sea for a complete suite of elements used as tracers for various sources and processes. Samples of suspended matter were collected at four stations from the Bosporus to the center of the western gyre during a R/V Bilim cruise in September 2000. Sample depths were from the oxic surface layer, the suboxic zone and the upper part of the anoxic (sulfidic) layer. All samples were analyzed for Al, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Mo, Ag, Cd, Ba, Pb, U and P using ICP-MS, AAS, and spectrophotometer. The main objective of this study was to determine the processes that influence the distributions of particulate trace metals in the water column under various redox environments. The composition of the particulate matter was influenced by lithogenic input from surrounding rivers, biological production in the surface layer, biogeochemical (e.g. redox) processes and anthropogenic inputs. Almost all elemental concentrations decreased from the coastal to the offshore stations to the center of the western gyre. Metal/Al ratios were compared with the ratios of average crust and Danube and Turkish rivers. Deviations from these lithogenic sources were used to examine the anomalies due to geochemical, biological and anthropogenic processes. In general, the largest metal enrichments relative to crust were observed inthe surface samples away from coastal sources. Metal/P ratios were used to compare data for some of the elements with previous data from the open ocean. The Me/P ratios for Cu, Zn, Mo and Ni were much higher than open ocean studies, while the ratios for Cd and Co were comparable. The high Me/P (and Me/Al) for several elements suggest anthropogenic input may contribute to these high surface concentrations. The composition of particulate matter from the suboxic zone showed that some elements were strongly enriched. Enrichments of Mn and Fe in the suboxic zone were observed, as expected. Mn and Fe oxides play an important role in scavenging processes. The redox dependent processes in the suboxic - anoxic interface influence the vertical distribution of U, V, Ni, Co, Cu, Zn, Ba and possibly Mo, Cr. Elements influenced by sulfide formation in the anoxic layer were Fe, Cr, Ni, Co, Mo, and Ag. [Copyright &y& Elsevier]

Abstract: This work describes a laboratory experiment designed to unravel mercury species reactivity in superficial coastal sediments oscillating between oxic and anoxic conditions. The experimental set-up has been applied to a sediment slurry from the Arcachon Bay (France) to follow the evolution of both naturally occurring (i.e. endogenous) and isotopically enriched added mercury species (i.e. exogenous, 199IHg and 201MMHg) at environmental levels. The transformation and partition between the different phases (aqueous, solid and gaseous) of the endogenous and exogenous mercury species (inorganic Hg (IHg), monomethyl Hg (MMHg), elemental Hg (Hg°) and dimethyl Hg (DMHg)) have been investigated by isotopic speciation methods throughout the experiment. The results demonstrate that the experimental approach is able to promote sediment redox oscillations and to simultaneously follow the biogeochemical fate of naturally occurring or added mercury species. Experimentally driven redox transition events were found to significantly enhance the aqueous Hg species concentrations, while the MMHg burden is not greatly affected. Indeed, during the anoxic-oxic transition, while aqueous endogenous IHg and MMHg exhibited a two-fold increase, aqueous exogenous IHg and MMHg increased 7 and 4 times, respectively. Transient increases of the net IHg methylation were recorded during the redox transitions with the largest increase of the MMHg contents (factor 1.8) observed during the oxic-anoxic transition. High resolution in situ redox experiments have not been performed up to now, therefore the developed experimental set-up provides novel insights in both the influence of redox conditions on Hg methylation/demethylation and adsorption/desorption processes and kinetics in superficial sediments. [ABSTRACT FROM AUTHOR]

Abstract: While soil water composition has long been recognised as being related to soil type (characteristics of the horizons), the influence of structures resulting from agricultural activities (hedges, ditches, wheel ruts, etc) is still under discussion. This work was undertaken to show that a snapshot of spatial variability of the geochemical characteristics of soil water at the scale of a plot can improve our understanding of soil geochemistry in a farmland setting. We selected a 3hectare hedged plot located on a hillside, limited by a stream and used as pasture where soils have developed in weathered gneiss. The water depth, electrical conductivity, major ions, temperature, pH, dissolved organic carbon (DOC) content, dissolved oxygen content, fluorescence, alkalinity, Fe2+, Mn2+, NO2 −, Fe(III) and F− contents were measured in 62 auger holes randomly drilled on the site. Four sectors were identified in order to describe the distribution of the main geochemical parameters. Electrical conductivity and some major ions, especially sulphate, had larger concentrations near hedges where oxic conditions prevailed. These features were attributed to the impact of the linear anthropogenic network on the circulation of subsurface soil waters and evapo-transpiration and represent sector I. Dissolved Mn was an indicator of well channelled runoff subsurfaces facilitating the circulation of more highly reducing water (sector III), while DOC probably marked areas drained less well, with a prolonged contact time between soil solutions and organic topsoil horizons (sector II). The presence of dissolved Mn and Fe(II) indicates bottomland anoxic conditions (sector IV). It is concluded that a survey of the chemical composition of soil water may be a direct approach to show the influence of permanent structures on current soil properties and dynamics. [Copyright &y& Elsevier]

In this study a simulated DEPHANOX process was used, including anaerobic/anoxic and oxic phases. An upflow anaerobic sludge blanket reactor (UASB), an anoxic sludge blanket reactor (UANSB) and a completely stirred tank reactor (CSTR) were used, sequentially. The atrazine, chemical oxygen demand (COD) removal efficiencies, methane and nitrogen (N2) gas productions and volatile fatty acid (VFA) concentrations were monitored to assess the stability and the performance of anaerobic/anoxic and oxic reactors. The produced intermetabolites were Diaminochloroatrazine(DACT), Desethylatrazine(DEA), Deisopropylatrazine(DIA) urea, ammonia, aromatic amines, Cl- 1 and NO3-N. For maximum atrazine and COD removal efficiencies (86% and 82%, respectively) the optimum atrazine concentrations were between 30-80 mg L- 1. The methane gas percentage varied between 40 and 68% while no N2 production was observed in the anaerobic UASB reactor; 6-10 mg L- 1 of urea, 4-21 mg L- 1 of ammonia, 8-10 mg L- 1 of aromatic amine and 4-6 mg L of Cl- 1 were detected during anaerobic atrazine degradation. 25-45% N2 gas production was observed in the anoxic reactor while the methane gas production was 1-5%. In the aerobic phase COD and atrazine were removed with removal efficiencies of 98% and 99% for initial atrazine concentrations of 0.3 mg L- 1 and 2.5 mg L- 1, respectively. [ABSTRACT FROM AUTHOR]

Nitrogen fixation, along with photosynthesis is the basis of all life on earth. Current understanding suggests that no plant fixes its own nitrogen. Some plants (mainly legumes) fix nitrogen via symbiotic anaerobic microorganisms (mainly rhizobia). The nature of biological nitrogen fixation is that the dinitrogenase catalyzes the reaction-splitting triple-bond inert atmospheric nitrogen (N2) into organic ammonia molecule (NH3). All known nitrogenases are found to be prokaryotic, multi-complex and normally oxygen liable. Not surprisingly, the engineering of autonomous nitrogen-fixing plants would be a long-term effort because it requires the assembly of a complex enzyme and provision of anaerobic conditions. However, in the light of evolving protein catalysts, the anaerobic enzyme has almost certainly been replaced in many reactions by the more efficient and irreversible aerobic version that uses O2. On the other hand, nature has shown numerous examples of evolutionary convergence where an enzyme catalyzing a highly specific, O2-requiring reaction has an oxygen-independent counterpart, able to carry out the same reaction under anoxic conditions. In this review, I attempt to take the reader on a simplified journey from conventional nitrogenase complex to a possible simplified version of a yet to be discovered light-utilizing nitrogenase. [ABSTRACT FROM AUTHOR]

Adsorption of seven phenolic compounds, namely phenol, 2-methylphenol, 2-ethylphenol, 2-chlorophenol, 2-nitrophenol, 4-chlorophenol, and 4-nitrophenol on granular activated carbon (GAC) F400 and two activated carbon fibers (ACFs), ACC-10 and ACC-15 were conducted to study the impact of functional groups on oligomerization. Single solute adsorption and binary solute adsorption were conducted under anoxic (absence of molecular oxygen) and oxic (presence of molecular oxygen) conditions at 23±1°C. For F400, the critical oxidation potential (COP), influenced by substitution of functional group, was found to be a limiting factor in oligomerization of adsorbates. For ACC-10, which has narrow pore size distribution (PSD) and small critical pore diameter (8.0Å), only phenol and 2-methylphenol showed occurrence of oligomerization under oxic conditions. The degree of oligomerization under oxic conditions was related to the PSD of the adsorbent. The micro-pore diameter of the ACFs effectively reduced the oligomerization process. The oxic and anoxic binary adsorption isotherms of phenol/2-ethylphenol and 2-methylphenol/2-nitrophenol on ACC-10 overlapped indicating hampering of oligomerization by the limited micro-pore diameter of ACFs. The Ideal Adsorbed Solution Theory (IAST), using the Myers equation for correlating the single-solute anoxic isotherms, well predicted both anoxic and oxic binary isotherms. [Copyright &y& Elsevier]

Microbially catalyzed cleavage of the imadazole ring of caffeine was observed in stream sediments collected upstream and downstream of municipal wastewater treatment plants (WWTP) in three geographically separate stream systems. Microbial demethylation of the N-methyl component of cotinine and its metabolic precursor, nicotine, also was observed in these sediments. These findings indicate that stream sediment microorganisms are able to substantially alter the chemical structure and thus the analytical signatures of these candidate waste indicator compounds. The potential for in situ biotransformation must be considered if these compounds are employed as markers to identify the sources and track the fate of wastewater compounds in surface-water systems. [ABSTRACT FROM AUTHOR]

A divided cell bioelectrochemical reactor comprised of two upflow submerged columns packed with Celite biocarrier was operated to generate oxic and anoxic compartments where the nitrified effluent from the first column was denitrified in the second for sequential nitrification-denitrification of a simulated wastewater. The experiments were carried out at current intensities of 0.5 mA/cm2 and 1.0 mA/cm2 over six phases. The wastewater pH decreased after contacting the oxic (nitrifying) compartment due to the acid equivalents produced electrolytically and during biological nitrification. The wastewater pH subsequently increased after contacting the anoxic (denitrifying) compartment due to the base equivalents produced electrolytically and the acid equivalents consumed during denitrification. At a current intensity of 0.5 mA/cm2, up to 56% of the influent nitrogen was removed on average during Phases I to III prior to operating at a higher current density. The nitrogen removal efficiency dropped to 15% at a current density of 1.0 mA/cm2 because of the pH inhibition and excess gases produced in the nitrification column. The reactor system did not recover from the inhibition. [ABSTRACT FROM AUTHOR]

The oxidative dissolution of pyrite (FeS2 ) is difficult to study because of redox transformations of the iron and sulfur, and adsorptive and precipitative loss of products from solution. Quantitative measurement of pyrite dissolution can perhaps be done most accurately with electrochemical techniques, but monitoring of dissolution products is of interest for interpretation of water-quality data at mine drainage and other field sites where pyrite dissolution is occurring. This l aboratory study was undertaken to assess the usefulness of the sum of sulfate, sulfite, and thiosulfate in solution as a reaction progress variable, or RPV, for abiotic pyrite dissolution. Sulfate was the only sulfur species detected in solution, and thus was chosen as the RPV. Previous investigators have demonstrated that ferrous iron is not reliable as an RPV because of adsorption to the pyrite surface. Results indicated that sulfate is also not a highly accurate RPV. There was a sulfate loss from s olution, perhaps by adsorption, with the extent of loss varying with solution conditions. While not a highly accurate RPV for kinetics modeling, the sulfate concentration provided a measure by which relative rates of abiotic pyrite dissolution could be assessed for pH 3 and 6, and with oxygen and ferric iron as oxidants. Sulfate production was greatest at pH 6 in the presence of oxygen, but no sulfate was produced under anoxic conditions (Fe3+ added as oxidant) at the same pH. The s ulfate release under oxic conditions at this circumneutral pH was an order of magnitude greater than the release at pH 3 under both oxic and anoxic conditions. [ABSTRACT FROM AUTHOR]

The underground plant parts of reed (Phragmites australis) growing in anoxic soil of the littoral zone of lakes are provided with oxygen via an aerenchyma. Some of this oxygen is released into the rhizosphere, which creates a potential microhabitat for aerobic fungi. Although fungal endophytes of reed have been shown to occur also in roots of flooded habitats, it is not known whether or how fungi can infect roots growing in anoxic or hypoxic soil. To study fungal infection of reed roots in the laboratory, we developed an incubation chamber to expose reed roots to conidia of Microdochium bolleyi in an anoxic agar medium and to observe fungal infection in vivo. Germination rates of conidia were high close to living roots, but decreased to zero in anoxic areas of the chamber. Conidial germ tubes located up to 200 μm from the roots grew preferentially towards the living roots. Conidia also germinated close to air-filled Teflon tubes and exhibited germ-tube tropism, but not as distinctly as on living reed roots. Conidia did not germinate in the neighbourhood of dead roots in anoxic agar. However, in the aerated margin of the incubation chamber most conidia germinated and exhibited tropic growth towards dead roots. Penetration of M. bolleyi through several cell layers of living roots was observed in cryo-microtome sections. Penetration was significantly deeper with illuminated plants than with plants kept in the dark; in some cases even the stele was reached. This is the first observation of oxygen released from roots to support growth of an aerobic fungus and of fungal penetration into root tissue in an anoxic environment. [Copyright &y& Elsevier]

• Soil water repellency (SWR) best measured by vacuum drying under anoxic conditions. • Similar soil water contents occurred for 20 °C vacuum and 105 °C oven-dried soil. • No difference in SWR between samples vacuum-dried anoxically at 20 °C or 105 °C. • Drying at 105 °C decreased SWR compared to 20 °C under oxic conditions at 101 kPa. Monitoring land degradation due to soil water repellency (SWR) through space and time is often complicated by different soil drying temperatures and drying times that generate artefacts causing inconsistent SWR results. This study aimed to develop a reproducible soil drying method at room temperature for the severity of potential SWR determination. We compared conventional 105 °C oven drying under oxic conditions (101.3 kPa) and vacuum drying under anoxic conditions (20 °C and low air pressure 1.3 kPa)—both drying methods removed the same amount of water from soil. We then investigated the effect of aeration condition (anoxic or oxic), temperature (20 °C or 105 °C) and air pressure (1.3 kPa or 101.3 kPa) on SWR and residual soil water content after drying using a complete factorial design. We hypothesised that 1) SWR will decrease with low air pressure under both oxic and anoxic conditions, 2) SWR will remain unchanged with temperature under anoxic conditions, and 3) conventional air drying treatments will have the highest residual soil water content. We used sieved, air-dried soil (<2 mm) that had been collected from a cropping field. Soil water repellency, determined by the molarity of ethanol droplet (MED) test, did not change following drying under anoxic conditions, relative to soil that was air-dried at 20 °C and 101.3 kPa under an oxic condition but decreased significantly under oxic conditions at high temperature (MED from ~1.58 to 1.34 mol L−1) or low air pressure (from ~1.58 to 1.42 mol L−1). We recommend vacuum drying water-repellent sandy soil under anoxic conditions at 20 °C and 1.3 kPa when assessing SWR. [ABSTRACT FROM AUTHOR]

• Surface layer of the mid-late Mesoproterozoic hydrosphere was oxic. • Primary productivity was dominant in the terrestrial hydrosphere. • The terrestrial hydrosphere offered best condition for complex eukaryotic evolution. This study performed a redox sensitive trace element (RSTE) and organic carbon isotope investigation on the shallow section of ~1.2 Ga Bijaigarh Shale, Kaimur Group, Vindhyan Supergroup. The results demonstrate that unlike the coeval deeper section, in which Mo and Ni concentrations are several-folds higher compared to the upper continental crust (UCC), the shallow section contains Mo and Ni equivalent to the upper continental crust (UCC). This spatially heterogeneous burial of Mo and Ni is very similar to the modern stratified basins i.e., Black Sea and Cariaco Basin, where Ni and Mo composition of the sediments underlying a shallow oxic water column is comparable to the UCC however, the deeper sediments underlying the anoxic/euxinic contains several folds-higher Mo and Ni compared to the UCC. Bulk precipitation of Mo in a hydrosphere is mainly controlled by sulphide present in the anoxic/euxinic layers of the water column, on the other hand, Ni precipitation is generally controlled by oxygenic primary productivity. Though the shallow section of the Bijaigarh Shale is depleted in Ni, a significant correlation between Ni and TOC is still relevant and indicates an oxygen-rich surface water layer for the respective palaeohydrosphere. Furthermore, δ13C-org values (between −32.0 and −30.4‰) from the shallow section suggests that the organic carbon exported into the sediments during the Bijaigarh Shale deposition was primarily derived from oxygenic photosynthesis in the concurrent surface water layers. [ABSTRACT FROM AUTHOR]