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Geochemical and biomarker characteristics of representative crude oil samples from selected fields in southern Nigeria were evaluated to determine the organic matter input, origin of biological material, depositional environment, thermal maturity, and genetic relationship between the oils. Four crude oil samples were obtained from various oil producing fields from Delta, Bayelsa and Abia state in southern Nigeria and labeled Kwale (KW), Kolo creek (KLC), Owaza (OWA1 and OWA2). The crude oil samples were fractionated into saturates, aromatic hydrocarbons and polar compounds using column chromatography on silica gel thereafter, analyzed using Gas chromatography-mass spectrometry (GC–MS). The calculated ratios of normal alkanes, acyclic isoprenoids, carbon preference index (CPI), hopanes, and steranes showed the following results: Pr/Ph (0.34 to 0.89); C29/C27 (0.78 to 1.25); 20S/(20S + 20R)C29sterane (0.28 to 0.66); 22S/(22S + 22R)C32 homohopane (0.17 to 0.23); CPI (0.96 to 0.98); Ts/Ts + Tm (0.46 to 0.50); and sterane/hopane (0.16 to 0.87). The results obtained were used to correlate the crude oils with respect to depositional environment, thermal maturity, and organic matter source. The Pr/Ph ratios of KW and KLC were less than one, and the cross-plot of Pr/nC17 versus Ph/nC18 of KW and KLC suggested that the oils were deposited under anoxic environments, whereas OWA1 and OWA2 indicated oxic conditions with no biodegradation. From the calculated ratios of 22S (22S + 22R)C32 homohopane and CPI, the oils were mature and had entered the generating window. Sample OWA1 is the most mature, while KLC is the least mature. The calculated ratios also showed that the four oil samples were from a shale source rock with both terrestrial and marine inputs. [ABSTRACT FROM AUTHOR]

Abstract Geochemical and biomarker characteristics of representative crude oil samples from selected fields in southern Nigeria were evaluated to determine the organic matter input, origin of biological material, depositional environment, thermal maturity, and genetic relationship between the oils. Four crude oil samples were obtained from various oil producing fields from Delta, Bayelsa and Abia state in southern Nigeria and labeled Kwale (KW), Kolo creek (KLC), Owaza (OWA1 and OWA2). The crude oil samples were fractionated into saturates, aromatic hydrocarbons and polar compounds using column chromatography on silica gel thereafter, analyzed using Gas chromatography-mass spectrometry (GC–MS). The calculated ratios of normal alkanes, acyclic isoprenoids, carbon preference index (CPI), hopanes, and steranes showed the following results: Pr/Ph (0.34 to 0.89); C29/C27 (0.78 to 1.25); 20S/(20S + 20R)C29sterane (0.28 to 0.66); 22S/(22S + 22R)C32 homohopane (0.17 to 0.23); CPI (0.96 to 0.98); Ts/Ts + Tm (0.46 to 0.50); and sterane/hopane (0.16 to 0.87). The results obtained were used to correlate the crude oils with respect to depositional environment, thermal maturity, and organic matter source. The Pr/Ph ratios of KW and KLC were less than one, and the cross-plot of Pr/nC17 versus Ph/nC18 of KW and KLC suggested that the oils were deposited under anoxic environments, whereas OWA1 and OWA2 indicated oxic conditions with no biodegradation. From the calculated ratios of 22S (22S + 22R)C32 homohopane and CPI, the oils were mature and had entered the generating window. Sample OWA1 is the most mature, while KLC is the least mature. The calculated ratios also showed that the four oil samples were from a shale source rock with both terrestrial and marine inputs.

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]

Introduction: The Caspian Sea is the world's largest landlocked saline lake which lies between Europe and Asia. This region is particularly known for its large-scale oil reserves, pipelines, and drilling activities, which have contributed to the environmental decline of this lake. In addition to pollution from the petroleum industry, drainage from various river basins brings an influx of residential, industrial, and agricultural effluents that induce eutrophication and hypoxic conditions in deeper, colder waters, creating an oxygen gradient. The temperature and oxygen stratification in this environment has presented a unique opportunity to investigate the potential of the biodegradative processes carried out by the indigenous microbial community. We believe these indigenous microbes possess different metabolic capabilities to degrade oil as they adapted to declining oxygen concentrations and temperatures with increasing depths over a prolonged period. Hence, community structure and composition will vary with depth. Methods: Microcosms were set up to observe the indigenous microbial reaction after a 60 ppm native crude oil amendment over 115 days. Surface water microcosms were incubated at 28°C and aerated while deep water microcosms were incubated at 8°C under anaerobic conditions. These two environmental conditions represent the temperature and oxygen extremes along the gradient and were selected as we try to simulate the indigenous community's response to this oil contamination. DNA was extracted and amplified from these microcosms and sequenced. Bioinformatic analysis was performed to track changes in the abundance of taxa present and biodiversity over different time points to show the progression of community structure. Results: All microcosms showed the presence of hydrocarbon-degrading phyla, whose presence is consistent with other reports from oil-enriched environments. However, distinct communities were observed in oxic versus hypoxic microcosms. Conclusion: Orders of Bacteria related to sulfate and nitrogen cycling were found in hypoxic microcosms, indicating a possible mechanism for the anaerobic biodegradation of crude oil. GC-MS analysis of initial and final microcosms also provided evidence of degradation of hydrocarbon fractions in both warm, oxic and cold, hypoxic conditions. [ABSTRACT FROM AUTHOR]

A novel Mg-based bimetal reagent (Mg/Cu) was used as an enhanced reductive system to degrade insensitive munition 2,4-dinitroanisole (DNAN), a contaminant found in energetic-laden waste. Degradation of DNAN was significantly impacted by dissolved oxygen and studied in anoxic and oxic bimetal systems (i.e., purging with N 2 , air, or O 2 gas). Degradation occurred through sequential nitroreduction: first one nitro group was reduced (ortho or para) to form short-lived intermediates 2-amino-4-nitroanisole or 4-amino-2-nitroanisole (2-ANAN or 4-ANAN), and then subsequent reduction of the other nitro group formed 2,4-diaminoanisole (DAAN). The nitro-amino intermediates demonstrated regioselective reduction in the ortho position to 2-ANAN; Regioselectivity was also impacted by the anoxic/oxic environment. Under O 2 -purging DNAN degradation rate was slightly enhanced, but most notably O 2 significantly accelerated DAAN generation. DAAN also further degraded only in the oxygenated Mg/Cu system. Adsorption of DNAN byproducts to the reagent occurred regardless of anoxic/oxic condition, resulting in a partition of carbon mass between the adsorbed phase (27%-35%) and dissolved phase (59%-72%). Additional surface techniques were applied to investigate contaminant interaction with Cu. Density functional theory (DFT) calculations identified preferential adsorption structures for DNAN on Cu with binding through two O atoms of one or both nitro groups. X-ray absorption spectroscopy (XAS) measurements determined the oxidation state of catalytic metal Cu and formation of a Cu-O-N bond during treatment. Laser desorption ionization mass spectrometry (LDI-MS) measurements also identified intermediate 2-ANAN adsorbed to the bimetal surface. [ABSTRACT FROM AUTHOR]

Objective: The objective of the present work was to reduce the start-up time of aerobic granular sludge (AGS) formation using medium-strength sewage and to find the most effective anaerobic, aerobic (oxic), and anoxic (A/O/A) cyclic time distribution over the 6 h cycle time for the removal of nutrients. Methods: A rectangular sequencing batch reactor (SBR) operated systematically in A/O/A cycle was designed for AGS formation. In order to achieve complete nutrient removal, the anoxic phase (5% of the total cycle duration) was introduced in the SBR cycle. Results: Growth in the biomass profile was observed after 20 days of operation, and complete granulation was achieved within 35 days of operational studies. Regular-shaped, compact granules with visible outlines and clear boundaries predominate inside the system, with an average particle size of 220.19 µm. The A/O/A system achieved average removal efficiencies of 70.02±5.98%, 78.21±18.66%, 60.62±9.69%, and 53.49±8.14% for COD, NH4+-N, TN, and PO43--P, respectively. The reasons for poor COD and PO43--P removal performance were the short anaerobic phase (25% of total cycle duration of 6 h) and higher biomass concentration. However, the long aerobic phase (60% of total cycle duration of 6 h) with the anoxic phase achieved outstanding (100%) NH4+-N removal efficiency after the system reached a steady state. SEM results inferred that Rod-shaped bacteria, Cocci, and Filamentous fungi were the dominant microorganisms found within the cultivated granules. Conclusions: Sewage with a high COD loading rate accelerates AGS formation and development within an A/O/A cycle SBR reactor. The rapid granulation and simultaneous removal of organics and nutrients by the A/O/A mode SBR without any support materials provide an alternative for wastewater treatment. [ABSTRACT FROM AUTHOR]

This research was designed to investigate some molecular biomarker signatures of weathered crude oils and automotive gas oil as a means of distinguishing them. Three samples of crude oil were collected from two producing field in the Niger Delta Nigeria and labelled UG7, UG8, AZU. A sample of automotive gas oil was collected from a dispensing station and labelled AGO. The samples were subject to a laboratory oil-weathering technique by rotary evaporation and thereafter to Gas Chromatography Mass Spectroscopy. The biomarker fingerprints of the acyclic isoprenoids and hopanes were used in calculating some diagnostic biomarker ratios such as Pr/Ph, CPI, %Σ(nC15 + C17 + C19)/Total normal alkanes, Σ(C21 - C31)/Σ(C15 - C20), Pr + nC17, Ph + nC18, Pr + nC17/Ph + nC18, C29Ts/C30-H, Ts/Ts + Tm, C35HH/C34HH, HHI, Moretane Index, Oleanane Index, C31(S)/C31(R), C29ββ/(ββ + αα). These ratios distinguished the samples in terms of the organic matter source, thermal maturity, redox environment degree of weathering and waxiness. Statistical plots such as the ternary plot, (nC17 + nC18)/Pr + Ph vs Pr + nC17/Ph + nC18 obtained from computed ratios gave a clear segregation of the samples. Similarly a dendrogram plot delineated samples UG7, U 0.00% similarity between the crude oils and the AGO. [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]

The phenomenon of phosphate release in sediments into water bodies under oxic environment has been investigated using the Diffusive Gradient in Thin Film (DGT) technique. This research consists of several stages: polymer synthesis and DGT probe assembly, sediment sampling, DGT deployment in oxic conditions, and phosphate analysis from DGT adsorption results. Acrylamide polymer was successfully synthesized with a composition 15% acrylamide; N-N'-methylenebisacrylamide 0.1% and ferrihydrite as binding gels. DGT probes were assembly by placing a 16 x 3.2 cm polyacrylamide gel, binding gels and filter membranes on the DGT probes. The sediment sample was taken from the Bogor Botanical Gardens at the coordinates 6°36’00.6” S; 106°47’51.0” E. The DGT probe was placed in sediment samples for 1, 3 and 7 days in oxic conditions. After the prescribed time, the binding gel was removed and cut every 1 cm depth, then eluted using 0.25 M H2SO4 and the phosphate concentration was measured using spectrophotometry method. The results showed that the phosphate concentration tends to be higher with the increasing incubation time and depth. Maximum CDGT phosphate released on day 1, day 3 and day 7 were 1.00 µg/L at a depth of 14 cm, 6.61 µg/L at a depth of 14 cm, and 20.92 µg/L at a depth of 11 cm respectively. This ensures that the phosphate in water bodies comes from biogeochemical processes that occur in sediments and is successfully measured through DGT techniques.

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]

Bitumen samples collected from different locations in south-western Nigeria were analysed for trace metal constituents such as Fe, Pb, Cu, Cd, Ni, Mn and V using Atomic absorption spectroscopy. The concentration of Fe ranged from 38.00 to 1537.00 ppm, Pb ranged from 11.00 to 27.00 ppm, Cu ranged from 3.00 to 10.00 ppm, Cd ranged from 4.00 to 15.00 ppm, Ni ranged from 9.00 to 62.00 ppm, Mn varied between 3.00 and 6.00 ppm, V ranged 10.00–150.00 ppm. Some ratios of these trace metals such as V/Ni, V/(V + Ni) and Fe/V were calculated, and the results show V/Ni ranged from 0.24 to 16.67, V/(V + Ni) varied from 0.20 to 0.94 and Fe/V ranged from 3.8 to 15.37. The low values of V/Ni ratios of samples AB, OI and IL suggest high maturity, mixed marine and terrestrial source of bitumen while the calculated values of V/(V + Ni) suggest that the samples were formed under oxic condition. The results were correlated using Pearson’s correlation matrix. A high positive correlation among the four bitumen samples indicates that they are geologically and genetically related. [ABSTRACT FROM AUTHOR]

Marine red beds (MRBs) as a special geological phenomenon have been considered relevant to specific palaeogeographic or paleoclimatic conditions. The Wuchiapingian Yundoutan Formation in Xikou, Shaanxi, Central China is characterized by a huge thick succession of red limestones, which is a unique deposition among marine strata of China during the Wuchiapingian. The lithology, mineralogy, and geochemistry features of the Yundoutan Formation MRBs were analyzed by using techniques of field measurement, polarized optical microscope, field emission scanning electron microscope (FESEM), diffuse absorbance spectroscopy (DAS), X-ray diffraction (XRD), and geochemical analysis, which were used to discuss their origin and palaeogeographic and paleoclimatic responses. The results show that the stain mineral for the MRBs is mainly weakly-crystalline hematite which can not be observed in the FESEM but was detected from the DAS first derivative spectra with featured peaks around 570 nm. The similar trend of Fe with refractory elements and the strong positive correlation between Fe and Al suggest Fe is mainly a terrestrial source. Limestones of the Yundoutan Formation contain different colors including red, light gray, and dark gray. Red limestones have comparable contents of Fe with dark gray limestones, which are larger than that of light gray limestones, but they are depleted in redox-sensitive elements (Cr, Ni, Cu, Zn, Mo, U) and riched in Fe(III) compared with dark gray limestones. Those indicate that the formation of red limestones needs both enough terrestrial Fe and strong oxic conditions. A mechanism proposed for the formation of red limestones was that Fe was transported from the highlands, which were then deposited under a strong oxic environment and transformed into hematite. We suggest the Wuchiapingian MRBs formed in Central China represent a unique paleogeography and palaeoclimate association. During that time, the study area attached to the northern margin of the United North China-Qinling Block received terrestrial materials from its northward highlands, which provided Fe under a warm climate. Meanwhile, the study area located between the South and North China blocks was on the narrow seaway connecting the Palaeotethys and Panthalassa, which produced relatively fast exchanging rates of seawater and thus a high content of oxygen that can easily transform terrestrial-sourced Fe into hematite. The gradual transition among color-different limestones may be driven by the changes in rainfall that influenced river transportation on terrestrial materials or sea-level changes that influenced the redox state of the water-sediment interface. • The pigment of the Wuchiapingian MRBs is mainly weakly-crystalline hematite. • Terrestrial Fe and high content of oxygen are the two key conditions for the Wuchiapingian MRBs. • The gradual transitions between red and light gray limestones may be controlled by variations of terrestrial input. • The Wuchiapingian MRBs may document that the South Qinling belt had already merged with North China Block before the Permian. [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]

Biodegradation of [A-ring 14C] Estrone (E1), 17 β-estradiol (E2), and 17 α-ethinylestradiol ( EE2) to 14 CO2 was investigated under light and dark conditions in microcosms containing epilithon or sediment collected from Boulder Creek, Colorado. Mineralization of the estrogen A-ring was observed in all sediment treatments, but not epilithon treatments. No difference in net mineralization between light and dark treatments was observed for 14C-E2. Net mineralization of 14C-E1 and 14C- EE2 was enhanced in light treatments. Extents of 14 CO2 accumulation and rates of mineralization were significantly greater for E2 than E1 under dark conditions, but were comparable under light conditions. These results indicate substantial differences in the uptake and metabolism of E1 and E2 in the environment and suggest biorecalcitrance of E1 relative to E2 in light-limited environments. The extent of 14 CO2 accumulation and rate of mineralization for EE2 in dark treatments were less than half of that observed for E2 and generally lower than for E1, consistent with previous reports of EE2 biorecalcitrance. However, 14 CO2 accumulation and rates of mineralization were comparable for EE2, E2, and E1 under light conditions. These results indicate photoactivation and/or phototransformation/photodegradation processes can substantially enhance heterotrophic biodegradation of estrogens in sunlit environments and may play an important role in estrogen transport and attenuation. [ABSTRACT FROM AUTHOR]

Microbial heterotrophic activity was investigated in oxic subseafloor sediments at North Pond, a sediment pond situated at 23°N on the western flank of the Mid-Atlantic Ridge. The North Pond sediments underlie the oligotrophic North Atlantic Gyre at 4580 m water depth and cover a 7-8 million year-old basaltic crust aquifer through which seawater flows. Discrete samples for experimentation were obtained from up to ~9 m-long gravity cores taken at 14 stations in the North Pond area. Potential respiration rates were determined in sediment slurries incubated under aerobic conditions with 14C-acetate. Microbial heterotrophic activity, as defined by oxidation of acetate to CO2 (with O2 as electron acceptor), was detected in all 14 stations and all depths sampled. Potential respiration rates were generally low (< 0.2 nmol of respired acetate cm-3 d-1) in the sediment, but indicate that microbial heterotrophic activity occurs in deep-sea, oxic, sub-seafloor sediments. Furthermore, discernable differences in activity existed between sites and within given depth profiles. At 7 stations, activity was increased by several orders of magnitude at depth (up to ~12 nmol of acetate respired cm-3 d-1). We attempted to correlate the measures of activity with high resolution color and element stratigraphy. Increased activities at certain depths may be correlated to variations in the sediment geology, i.e. to the presence of dark clay-rich layers, of sandy layers, or within clay-rich horizons presumably overlying basalts. This would suggest that the distribution of microbial heterotrophic activity in deeply buried sediments may be linked to specific lithologies. Nevertheless, high resolution microbial examination at the level currently enjoyed by sedimentologists will be required to fully explore this link.

The isotopic compositions of redox-sensitive elements such as uranium (U) and molybdenum (Mo) have been extensively used to track the evolution of redox conditions on Earth's surface. However, additional investigation of the behaviors of U and Mo in modern marine sediments—particularly in reducing sediments underlying oxic seawater—can bolster understanding and improve application of these systems as biogeochemical tracers. Here we present elemental and isotopic Mo and U data from reducing sediments from various sites in the Bering Sea where the extent of bioturbation is well characterized. Total Mo concentrations and total organic carbon contents (TOC) are positively correlated, as are authigenic Mo isotopic compositions and TOC, indicating the presence of authigenic Mo enrichments in these sediments. Similar to what has previously been observed in euxinic settings, we observe a positive correlation between authigenic U and Mo concentrations, and a negative correlation between the isotopic compositions of authigenic U and Mo (δ238U auth and δ98Mo auth). These patterns likely reflect close associations of U and Mo reduction to organic carbon degradation. Observed variation in δ98Mo auth values could reflect variations in Mo removal efficiency or Mo isotopic fractionation between particles and seawater related to porewater H 2 S levels. Conversely, we interpret variation in δ238U auth values in these Bering Sea samples to be related to varying extents of U reduction and removal, coupled with anaerobic carbon degradation. There is no significant correlation between the extent of bioturbation and Mo or U isotope values, suggesting that bioturbation would likely not have a significant influence on sedimentary Mo and U records. Further, the array of U and Mo isotopic data from these sediments is distinct from those observed in anoxic sediments below euxinic seawater—suggesting that a combination of U and Mo isotopic compositions could help to more accurately resolve the redox state of depositional environments from past intervals of Earth's history. [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]

The concentrations of multiple redox-sensitive elements such as Re, U, Mo, Cd, V, Sb, and Tl were determined in sediments from the southeastern Arabian Sea (9°21′N: 71°59′E) to understand the bottom water oxygenation history throughout the past 140ka. The enrichment of redox-sensitive elements (Re, U, Cd and Sb) above average crustal abundances suggests that the Last Glacial Maxima (17.48ka), stadials of Marine Isotope Stage (MIS)-5 (5b and 5d) and Glacial Termination (GT)-II (133ka) were associated with suboxic bottom water conditions. Sediments deposited during these suboxic conditions show the highest Re content (up to 54ppb normalized to a carbonate free basis) which is highly enriched over average continental crust (0.4ppb) and these sediments appear to be the major sink for the global mass balance estimation. Marine Isotope Stages 1, 3, 4 and interstadials of MIS-5 (5a, 5c & 5e) were all associated with near-oxic conditions. Overall, the lack of enrichment of Mo and V above crustal abundance, and a high Re/Mo (ppm/ppm) ratio (avg. 18.2×10−3) suggest that sediments of the southeastern Arabian Sea never contained free H2S during the last 140ka. These changes in the bottom water oxygen content can be related to the oceanic circulation pattern during this time and in part are reflected in relationships between the timing of redox changes and paleoproductivity proxies. [Copyright &y& Elsevier]

The exchange of phosphorus (P) during the resuspension of sediments into shallow (oxic) waters of deep stratified lakes is regulated by equilibrium dynamics. In this study, we compared the P-sorption characteristics of sediments from 17 shallow and deep littoral sites in an oligo-mesotrophic lake. Zero Equilibrium P Concentration (EPC0) ranged from 0.2 to 5μgPL−1. EPC0 did not vary with sediment characteristics, but increased with increasing sediment-to-water ratios (SWR). Buffering capacity also increased with increasing SWR up to 1gL−1, at which point P concentrations were buffered almost perfectly. Therefore, internal P loading in littoral areas may depend primarily on the intensity and duration of sediment resuspension instead of sediment composition, and is expected to be spatially and temporally patchy. Maximum P-sorption capacity (S max) varied with chemical composition of the sediments, but was generally low, indicating a limited capacity of littoral sediments to retain external inputs of P. [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]

Soluble reactive phosphorus (SRP) concentrations in wetland surface waters were measured during laboratory incubations in the presence of wetland soils and Typha leaf litter. Aerated water columns above intact soil cores increased in SRP concentration (up to 73 µg L1 over 28 days, whereas the water column in cores containing soil and a Typha litter layer showed no concentration increase (remained < 5 µg SRP L-1). In the absence of soil, phosphorus (P) uptake by leaf litter and associated microbial biomass occurred rapidly under oxic conditions (max. 24-hr. uptake, 524 ± 90 µg P g-1 dry litter d-1), but uptake was slower and less complete under hypoxic conditions. At the highest tested initial P concentration of 1 mg L-1, P uptake by litter under hypoxic conditions (< 0.5 mg O2 L-1) was 41% of the oxic rate, or 216 ± 42 µg P g-1 dry litter d-1. Differences between hypoxic and oxic P uptake rates, however, were not observed at initial SRP concentrations of 100 µg L-1 or less. Our results suggest that leaf litter may be important to mitigating soil P release. [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]

Samples were collected from an oil polluted site in Niger-delta, Nigeria. Gas chromatographic analyses carried out on the samples revealed an abundance of n-alkanes within the n-C8– n-C23 region. The pristane/phytane ratio of 5.70 obtained for the samples depicted a plant/terrestrial source input and a possible oxic depositional environment. The n-C17/pristane and n-C18/phytane ratios of 2.80 and 2.77, respectively, suggested that the spilled oil was only slightly weathered, as corroborated by the presence of peaks in the aromatic hydrocarbon fingerprints. The polycyclic aromatic hydrocarbon (PAH) fractions showed that the hydrocarbon fractions might have undergone combustion and/or that there was bush burning at the site prior to the oil spill incidence. This is supported by the abundance of high-molecular-weight PAHs which are pyrogenic in nature. High molecular weight PAHs are products of the combustion of petroleum or its products. The phenanthrene/anthracene ratio of 0.95, fluorathene/pyrene ratio of 2.23 and the ∑ (other three to six ringed PAHs)/∑ (five alkylated PAHs) ratio far greater than unity (4.10) also affirm this. On the other hand, the benzo (a) anthracene to chrysene ratio of 0.24 confirms the petrogenic origin of the spilled oil because chrysene which is highly abundant is a fossil PAH. [ABSTRACT FROM AUTHOR]