Sulfate Oxygen Research Articles

Some Physical and Chemical Properties of Han Stream Spilled to Karakaya Dam Lake (Malatya, Turkey)

In this study, some physical and chemical properties of Han Stream (Malatya) in relation to water quality was investigated. For this purpose water samples were collected at monthly for eight months interval between December 2013-November 2014 (June- September is dry period). Water temperature, pH, electrical conductivity, dissolved oxygen and flow rate were measured directly in study area whilst chemical analysis such as sulfate, silica, nitrite, nitrate, total nitrogen, total phosphorus, acide capacity and chemical oxygen demand were carried out in water quality laboratory by means of cell test through a spectrophotometer. Total hardness, salinity and organic matter were determined in accordance with methods in APHA (1985). According to the Water Pollution Control Regulation for Inland Water Resources, study results showed that Han Stream should be classified as class I (high quality water) in terms of all parameters except that total phosphorus values (II/III class, less polluted).

Effects of phenol on sulfate reduction by mixed microbial culture: kinetics and bio-kinetics analysis.

Mixed microbial culture collected from the wastewater treatment plant of Indian Institute of Technology Guwahati (IITG) was further grown in anaerobic condition in presence of sulfate where lactate was added as a carbon source. Sulfate addition was increased stepwise up to 1,000 mg l-1 before phenol was added at increasing concentrations from 10 mg l-1 to 300 mg l-1. Kinetics of sulfate, phenol and chemical oxygen demand reduction were studied and experimental findings were analyzed using various bio-models to estimate the bio-kinetic coefficients. This is the first detailed report on kinetics and bio-kinetic studies of sulfate reduction in presence of phenol. Experimental results showed that there was no inhibition of sulfate reduction and microbial growth up to 100 mg l-1 phenol addition. However, inhibition to different degrees was observed at higher phenol addition. The experimental data of microbial growth and substrate consumption in presence of phenol fitted well to the Edward model (R2 = 0.85, root mean square error = 0.001011) with maximum specific growth rate = 0.052 h-1, substrate inhibition constant = 88.05 mg l-1 and half saturation constant = 58.22 mg l-1. The characteristics of the cultured microbes were determined through a series of analysis and microbial tests.

Sulfate-dependent anaerobic oxidation of methane at a highly dynamic bubbling site in the Eastern Sea of Marmara (Çinarcik Basin)

During the MARSITECruise expedition in November 2014 on board the RV Pourquoi Pas?, multidisciplinary sampling was carried out with the ROV Victor 6000 in order to investigate biogeochemical processes taking place at cold seep environments in the Sea of Marmara. Pore water, bottom water, sediment and authigenic carbonate samples were collected from two short push cores (MRS-DV5-PC04 − 8cm, MRS-DV5-PC01 − 12.5cm) at an active methane bubbling site in the southeastern part of the Çinarcik Basin. Sulfate sulfur and oxygen isotope data as well as sulfide isotope data indicate that sulfate-dependent anaerobic oxidation of methane is the dominant process in the sediments. This is confirmed by archaeal lipids diagnostic for anaerobic methane oxidizers detected with strong 13C-depletions. The available data even allows to distinguish the dominant AOM assemblages. Specific lipid patterns are consistent with a dominance of ANME-2 archaea within the microbial community. Abundant authigenic carbonates (mostly aragonite), found at all depths, show a narrow range in δ13C values between −27.69‰ and −33.40‰. The carbon isotopic composition of the dissolved inorganic carbon as well as strontium and calcium isotopes confirm that the current reaction zone (sulfate-methane transition zone) starts at the bottom of the core. All shallower carbonates are witnesses of paleo seepage activity. U-Th dating of four pure aragonite samples show the short time span that is preserved in core MRS-DV5-PC01 (235 ± 60yr B.P.). Two major earthquakes of 1766 CE and 1754 CE in the Çinarcik Basin might potentially have triggered the increased seepage of methane at this location.

Stable sulfur and oxygen isotopes as geochemical tracers of sulfate in karst waters

Karst water resources, which are extremely sensitive to mining activities, are critical for the support of human societies and ecological systems in many regions worldwide. In order to determine the sources and fate of dissolved sulfate in low-pH karst waters, hydrochemical variations of karst waters with and without acid mine drainage (AMD) impacts were investigated along with stable isotope dynamics. As expected, hydrochemical characteristics and isotopic compositions of the AMD and AMD-downstream water (ADW) were dramatically different from that of the non-AMD-impacted water (NAW). The sources of sulfur isotopes in sulfate were predominantly pyrite oxidation for the AMD and ADW, and atmospheric deposition for the NAW. Based on the general isotope-balance model, the relative proportions of sulfate oxygen derived from water and air were calculated. The mean proportion of sulfate oxygen derived from water in ADW was roughly double that of AMD. This suggests that the sulfate associated with AMD is predominantly influenced by aerobic pyrite oxidation, while that of ADW is likely affected by the dissolution of pyrite under anaerobic conditions in reservoir sediment. This observation was coincident with the noted variations of hydrochemical characteristics and was supported by principal component analysis. These results provide a better understanding of how stable isotopes of sulfate and water can be used to track mining contamination in karst aquifers, which could benefit remediation planning for these distinctive systems.

Two-step synthesis of ferrocenyl esters of vanillic acid

Successive reactions of vanillin with aromatic aldehydes at the phenol group and ferroceneboronic acid at the carbonyl group catalyzed with various N-heterocyclic carbenes afforded the corresponding ferrocenyl esters. In these reactions copper(II) sulfate, cinnamic aldehyde, and air oxygen act as oxidants. The resulting ferrocenyl esters of vanillic acid were tested for cytotoxicity.

Oxygen and sulfur isotopes in sulfate in modern euxinic systems with implications for evaluating the extent of euxinia in ancient oceans

Euxinic conditions, which are defined by the presence of sulfide in the water column, were common in ancient oceans. However, it is not clear how the presence of sulfide in the water column affects the balance between rates of sulfide oxidation and sulfate reduction, which plays a major role in regulating the net redox state of the ocean-atmosphere system. Euxinia could lead to higher rates of sulfide oxidation because sulfide may diffuse more rapidly into the oxic zone in solution than in sediment. Alternatively, sulfide oxidation could be inhibited by low overall availability of suitable oxidants in euxinic settings. Here, we constrain rates of sulfide oxidation versus sulfate reduction in four euxinic water columns in coastal ponds by modeling the evolution of the concentration and sulfur and oxygen isotope compositions of sulfate from post-hurricane, well-oxygenated conditions to modern, euxinic conditions. The results of the one-dimensional, depth-dependent models of water column sulfate geochemistry indicate that the fraction of sulfate reduced that is subsequently reoxidized is low (0.11–0.42) in euxinic systems relative to the modern well-oxygenated ocean (0.75–0.90). This implies that sulfide reoxidation rates are low in euxinic systems because of oxidant limitation and physical transport. Low fractional sulfide reoxidation in euxinic systems has important implications for exploring how oxygen levels in the ocean and atmosphere have changed through Earth history. We use a marine sulfate isotope box model to explore how low reoxidation rates in euxinic systems affect marine sulfate sulfur and oxygen isotope records. Model results indicate that marine sulfate sulfur and oxygen isotope compositions increase during the expansion of euxinia with patterns that are distinct from other isotopic changes to the marine sulfate reservoir. Thus, marine sulfate sulfur and oxygen isotope box models can be applied to ancient isotope records in order to evaluate the expansion of euxinia in ancient oceans because sulfide oxidation rates are low relative to sulfate reduction rates.

Impact of Dehydroepiandrosterone Sulfate on Newborn Leukocyte Telomere Length

The newborn setting of leukocyte telomere length (LTL) likely has important implications for telomere dynamics over the lifespan. However, its determinants are poorly understood. Hormones play an important role during pregnancy and delivery. We hypothesized that exposure to hormones may impact the fetal telomere biology system. To test this hypothesis, cortisol, estradiol, dehydroepiandrosterone sulfate (DHEAS) and reactive oxygen species (ROS) were measured in cord blood of 821 newborns from a prospective study. After accounting for the effects of potential determinants of newborn LTL, a 10-fold increase in DHEAS concentration was associated with a 0.021 increase in T/S ratio of newborn LTL (95% confidence interval: 0.009–0.034, P = 0.0008). For newborns who fell in the lowest quartile of DHEAS level, the mean newborn LTL was estimated to be approximately 2.0% shorter than the newborns in the highest DHEAS concentration quartile (P = 0.0014). However, no association was found between newborn LTL and cortisol or estradiol. As expected, newborns with higher ROS level (ROS > 260 mol/L) had lower LTL compared to that with lower ROS level (ROS ≤ 260 mol/L) (P = 0.007). There was also an inverse relationship between DHEAS and ROS (P < 1×10−4). Our findings suggest that exposure to DHEAS may exert a “programming” effect on the newborn telomere biology system.

Sulphated Zirconia Catalyst Prepared from Solid Sulphates by Non-aqueous Method

Non-crystallinesulphated zirconia catalysts were synthesised by a non-aqueous and non-conventional method. The effect of varying the molar ratio of sulphating agent to zirconium source was also investigated. The samples were characterized by X-ray diffraction, Energy Dispersive X-ray (EDX), Infra-red Spectroscopy (IR),X-ray Photoelectron Spectroscopy (XPS). The surface acidity was measured by the Pyridine-DRIFTS (Diffuse Reflectance Infrared Fourier Transform Spectroscopy) technique. The structural and textural properties of the sulphated zirconia were studied. The EDX and XPS profiles suggested that both sulphated zirconia catalysts have similar zirconia and sulphate structures; however, both catalysts were amorphous. Deconvolution of their XPS O 1s spectra showed that the samples contained both oxide oxygen of zirconium and sulphate oxygen, which sample I showed a higher amount of sulphate oxygen. Adsorption of pyridine into the samples indicated that the higher amounts of Bronsted acid sites are presented in sample I with lower amount of sulphate during preparation. This opens up the possibility of controlling the degree and type of active sites on a catalyst by the amount of sulphate used for preparation. Sulphated zirconia catalyst with higher activity properties was achieved via a non-aqueous, environmentalfriendly method. The zirconia catalyst has great contribution towards energy production which is used for preparation and trans-esterification of fatty acids for production of biodiesel.

Pyrosequencing reveals microbial community dynamics in integrated simultaneous desulfurization and denitrification process at different influent nitrate concentrations

Integrated simultaneous desulfurization and denitrification (ISDD) process has proven to be feasible for the coremoval of sulfate, nitrate, and chemical oxygen demand (COD). In this study, we aimed to reveal the microbial community dynamics in the ISDD process with different influent nitrate (NO3−) concentrations. For all tested scenarios, full denitrification was accomplished while sulfate removal efficiency decreased along with increased influent NO3− concentrations. The proportion of S0 to influent SO42− maintained a low level (5.6–17.0%) regardless of the increased influent NO3− concentrations. Microbial community analysis results showed that higher influent NO3− concentrations affected the microbial community structure greatly. Phyla Proteobacteria, Spirochaetae, Firmicutes, Synergistetes, and Chloroflexi dominated in all the community compositions, of which Proteobacteria exhibited a clear difference among eight microbial samples. Members of δ-Proteobacteria, with 16S rRNA gene sequences related to Desulfobulbus, were clearly decreased at influent NO3− = 3000 and 3500 mg/L, suggesting an inhibitory effect of NO3− on sulfate reduction. In contrast, as influent NO3− concentration increased, microbial community was notably enriched in γ-Proteobacteria and ε-Proteobacteria, which revealed the enrichment of 16S rRNA gene sequences related to Pseudomonas (γ-Proteobacteria), and Arcobacteria and Sulfurospirillum (ε-Proteobacteria).

Sulfur and Oxygen Isotope Fractionation During Bacterial Sulfur Disproportionation Under Anaerobic Haloalkaline Conditions

ABSTRACTSulfur and oxygen isotope fractionation of elemental sulfur disproportionation at anaerobic haloalkaline conditions was evaluated for the first time. Isotope enrichment factors of the strains Desulfurivibrio alkaliphilus and Dethiobacter alkaliphilus growing at pH 9 or 10 were −0.9‰ to −1‰ for sulfide (34ϵ), +3.6‰ to +4.7‰ for sulfate (34ϵ), and +3.5‰ to +7.7‰ for oxygen in sulfate (18ϵ). These values are significantly smaller compared to previously published values of sulfur disproportionators at neutral pH. We propose that this discrepancy is caused by masking effects due to preferential formation of polysulfides at high pH leading to accelerated internal sulfur turnover rates, but cannot rule out distinct isotope effects due to specific enzymatic disproportionation reactions under haloalkaline conditions. The results imply that the microbial sulfur cycle in haloalkaline environments is characterized by specific stable sulfur and oxygen isotope patterns.

Assessment of sulfide production risk in soil during the infiltration of domestic wastewater treated by a sulfur-utilizing denitrification process.

This study aimed to determine the potential of sulfide generation during infiltration through soil of domestic wastewater treated by a sulfur-utilizing denitrification process. Three types of soil with different permeability rates (K s = 0.028, 0.0013, and 0.00015cm/s) were investigated to evaluate the potential risk of sulfur generation during the infiltration of domestic wastewater treated by a sulfur-utilizing denitrification system. These soils were thoroughly characterized and tested to assess their capacity to be used as drainages for wastewaters. Experiments were conducted under two operating modes (saturated and unsaturated). Sulfate, sulfide, and chemical oxygen demand (COD) levels were determined over a period of 100days. Despite the high concentration of sulfates (200mg/L) under anaerobic conditions (ORP = -297mV), no significant amount of sulfide was generated in the aqueous (<0.2mg/L) or gaseous (<0.15ppm) phases. Furthermore, the soil permeability did not have a noticeable effect on the infiltration of domestic wastewater treated by a sulfur-utilizing denitrification system due to low contents of organic matter (i.e., dissolved organic carbon, DOC). The autotrophic denitrification process used to treat the domestic wastewater allowed the reduction of the concentration of biochemical oxygen demand (BOD5) below 5mg/L, of DOC below 7mg/L, and of COD below 100mg/L.

Structural Basis for Nucleotide Hydrolysis by the Acid Sphingomyelinase-like Phosphodiesterase SMPDL3A

Sphingomyelin phosphodiesterase, acid-like 3A (SMPDL3A) is a member of a small family of proteins founded by the well characterized lysosomal enzyme, acid sphingomyelinase (ASMase). ASMase converts sphingomyelin into the signaling lipid, ceramide. It was recently discovered that, in contrast to ASMase, SMPDL3A is inactive against sphingomyelin and, surprisingly, can instead hydrolyze nucleoside diphosphates and triphosphates, which may play a role in purinergic signaling. As none of the ASMase-like proteins has been structurally characterized to date, the molecular basis for their substrate preferences is unknown. Here we report crystal structures of murine SMPDL3A, which represent the first structures of an ASMase-like protein. The catalytic domain consists of a central mixed β-sandwich surrounded by α-helices. Additionally, SMPDL3A possesses a unique C-terminal domain formed from a cluster of four α-helices that appears to distinguish this protein family from other phosphoesterases. We show that SMDPL3A is a di-zinc-dependent enzyme with an active site configuration that suggests a mechanism of phosphodiester hydrolysis by a metal-activated water molecule and protonation of the leaving group by a histidine residue. Co-crystal structures of SMPDL3A with AMP and α,β-methylene ADP (AMPCP) reveal that the substrate binding site accommodates nucleotides by establishing interactions with their base, sugar, and phosphate moieties, with the latter the major contributor to binding affinity. Our study provides the structural basis for SMPDL3A substrate specificity and sheds new light on the function of ASMase-like proteins.

Kinetics of Indigenous Nitrate Reducing Sulfide Oxidizing Activity in Microaerophilic Wastewater Biofilms

Nitrate decreases sulfide release in wastewater treatment plants (WWTP), but little is known on how it affects the microzonation and kinetics of related microbial processes within the biofilm. The effect of nitrate addition on these properties for sulfate reduction, sulfide oxidation, and oxygen respiration were studied with the use of microelectrodes in microaerophilic wastewater biofilms. Mass balance calaculations and community composition analysis were also performed. At basal WWTP conditions, the biofilm presented a double-layer system. The upper microaerophilic layer (~300 μm) showed low sulfide production (0.31 μmol cm-3 h-1) and oxygen consumption rates (0.01 μmol cm-3 h-1). The anoxic lower layer showed high sulfide production (2.7 μmol cm-3 h-1). Nitrate addition decreased net sulfide production rates, caused by an increase in sulfide oxidation rates (SOR) in the upper layer, rather than an inhibition of sulfate reducing bacteria (SRB). This suggests that the indigenous nitrate reducing-sulfide oxidizing bacteria (NR-SOB) were immediately activated by nitrate. The functional vertical structure of the biofilm changed to a triple-layer system, where the previously upper sulfide-producing layer in the absence of nitrate split into two new layers: 1) an upper sulfide-consuming layer, whose thickness is probably determined by the nitrate penetration depth within the biofilm, and 2) a middle layer producing sulfide at an even higher rate than in the absence of nitrate in some cases. Below these layers, the lower net sulfide-producing layer remained unaffected. Net SOR varied from 0.05 to 0.72 μmol cm-3 h-1 depending on nitrate and sulfate availability. Addition of low nitrate concentrations likely increased sulfate availability within the biofilm and resulted in an increase of both net sulfate reduction and net sulfide oxidation by overcoming sulfate diffusional limitation from the water phase and the strong coupling between SRB and NR-SOB syntrophic relationship.

Heavy metal removal from multicomponent system by sulfate reducing bacteria: Mechanism and cell surface characterization

This study evaluated the combined effect of Cd(II), Cu(II), Ni(II), Fe(III), Pb(II) and Zn(II) on each other removal by anaerobic biomass under sulfate reducing condition. Statistically valid Plackett–Burman design of experiments was employed to carry out this mixture study. The results obtained showed a maximum removal of Cu(II) (98.9%), followed by Ni(II) (97%), Cd(II) (94.8%), Zn(II) (94.6%), Pb(II) (94.4%) and Fe(III) (93.9%). Analysis of variance (ANOVA) of the sulfate and chemical oxygen demand (COD) reduction revealed that the effect due to copper was highly significant (P value<0.05) on sulfate and COD removal. To establish the role of sulfate reducing bacteria (SRB) in the metal removal process, surface morphology and composition of the metal loaded biomass were analyzed by transmission electron microscopy (TEM) equipped with energy dispersive spectroscopy (EDS) and by field emission scanning electron microscopy (FESEM) integrated with energy dispersive X-ray spectroscopy (EDX). The results obtained revealed that the metal precipitates are associated with the outer and inner cell surface of the SRB as a result of the sulfide generated by SRB.

A revised seawater sulfate oxygen isotope record for the last 4 Myr

Using a new method to purify barium sulfate from marine barite, we produce a highly resolved seawater sulfate oxygen isotope data set for the past 4million years. We show that the overall magnitude of the δ18O shift is smaller than previously thought (1–1.5‰ vs 6 ‰).Expanding on previous work, we explore the effects of Quaternary sea level variations on the global sulfur cycle. Our modeling results confirm the earlier hypothesis that the increased duration and amplitude of sea level lowstands during the Quaternary favors direct sulfide oxidation over microbial disproportionation.We show that oxygen isotope ratios of core top barite are up to 2.5‰ lower than the seawater sulfate δ18O value. We hypothesize that this offset is caused by incorporation of sulfate from oxidized organic sulfur compounds during precipitation of barite. Our results provide another puzzle piece in the attempt to understand the origin of marine barite.

Large Carbonate Associated Sulfate isotopic variability between brachiopods, micrite, and other sedimentary components in Late Ordovician strata

Carbonate Associated Sulfate (CAS) is trace sulfate incorporated into carbonate minerals during their precipitation. Its sulfur isotopic composition is often assumed to track that of seawater sulfate and inform global carbon and oxygen budgets through Earth's history. However, many CAS sulfur isotope records based on bulk-rock samples are noisy. To determine the source of bulk-rock CAS variability, we extracted CAS from different internal sedimentary components micro-drilled from well-preserved Late Ordovician and early Silurian-age limestones from Anticosti Island, Quebec, Canada. Mixtures of these components, whose sulfur isotopic compositions vary by nearly 25‰, can explain the bulk-rock CAS range. Large isotopic variability of sedimentary micrite CAS (34S-depleted from seawater by up to 15‰) is consistent with pore fluid sulfide oxidation during early diagenesis. Specimens recrystallized during burial diagenesis have CAS 34S-enriched by up to 9‰ from Hirnantian seawater, consistent with microbial sulfate reduction in a confined aquifer. In contrast to the other variable components, brachiopods with well-preserved secondary-layer fibrous calcite—a phase independently known to be the best-preserved sedimentary component in these strata—have a more homogeneous isotopic composition. These specimens indicate that seawater sulfate remained close to about 25‰ (V-CDT) through Hirnantian (end-Ordovician) events, including glaciation, mass extinction, carbon isotope excursion, and pyrite-sulfur isotope excursion. The textural relationships between our samples and their CAS isotope ratios highlight the role of diagenetic biogeochemical processes in setting the isotopic composition of CAS.

Flourishing ocean drives the end-Permian marine mass extinction

The end-Permian mass extinction, the most severe biotic crisis in the Phanerozoic, was accompanied by climate change and expansion of oceanic anoxic zones. The partitioning of sulfur among different exogenic reservoirs by biological and physical processes was of importance for this biodiversity crisis, but the exact role of bioessential sulfur in the mass extinction is still unclear. Here we show that globally increased production of organic matter affected the seawater sulfate sulfur and oxygen isotope signature that has been recorded in carbonate rock spanning the Permian-Triassic boundary. A bifurcating temporal trend is observed for the strata spanning the marine mass extinction with carbonate-associated sulfate sulfur and oxygen isotope excursions toward decreased and increased values, respectively. By coupling these results to a box model, we show that increased marine productivity and successive enhanced microbial sulfate reduction is the most likely scenario to explain these temporal trends. The new data demonstrate that worldwide expansion of euxinic and anoxic zones are symptoms of increased biological carbon recycling in the marine realm initiated by global warming. The spatial distribution of sulfidic water column conditions in shallow seafloor environments is dictated by the severity and geographic patterns of nutrient fluxes and serves as an adequate model to explain the scale of the marine biodiversity crisis. Our results provide evidence that the major biodiversity crises in Earth's history do not necessarily implicate an ocean stripped of (most) life but rather the demise of certain eukaryotic organisms, leading to a decline in species richness.

Influence of co-substrate on textile wastewater treatment and microbial community changes in the anaerobic biological sulfate reduction process

This study investigated the anaerobic treatment of sulfate-rich synthetic textile wastewater in three sulfidogenic sequential batch reactors (SBRs). The experimental protocol was designed to examine the effect of three different co-substrates (lactate, glucose, and ethanol) and their concentrations on wastewater treatment performance. Sulfate reduction and dye degradation were improved when lactate and ethanol were used as electron donors, as compared with glucose. Moreover, under co-substrate limited concentrations, color, sulfate, and chemical oxygen demand (COD) removal efficiencies were declined. By reducing co-substrate COD gradually from 3000 to 500mg/L, color removal efficiencies were decreased from 98.23% to 78.46%, 63.37%, and 69.10%, whereas, sulfate removal efficiencies were decreased from 98.42%, 82.35%, and 87.0%, to 30.27%, 21.50%, and 10.13%, for lactate, glucose, and ethanol fed reactors, respectively. Fourier transform infrared spectroscopy (FTIR) and total aromatic amine analysis revealed lactate to be a potential co-substrate for further biodegradation of intermediate metabolites formed after dye degradation. Pyrosequencing analysis showed that microbial community structure was significantly affected by the co-substrate. The reactor with lactate as co-substrate showed the highest relative abundance of sulfate reducing bacteria (SRBs), followed by ethanol, whereas the glucose-fed reactor showed the lowest relative abundance of SRB.

Synthesis, Crystal Structure, Physical Properties and Theoretical Calculations of a New One-Dimensional Ni(II) Coordination Polymer Constructed by 1,10-Phenanthroline Derivative Ligand and Sulfate

A new Ni(II) coordination polymer constructed by 1,10-phenanthroline derivative 2-(2-chloro-6-fluorophenyl)-1H-imidazo[4,5-f][1, 10]phenanthroline (L) and inorganic sulfate anion, namely, [Ni(L)(SO4)(H2O)2]n (1), has been successfully synthesized under hydrothermal condition. In compound 1, each sulfate functions in bidentate bridging coordination mode and links two Ni(II) atoms to generate a one-dimensional chain structure. The adjacent chains are joined together by aromatic π–π interactions between L ligands to yield a two-dimensional supramolecular layer. The O–H···O and N–H···O hydrogen bonding interactions between sulfate oxygen atoms, coordination water molecules and nitrogen atoms of L ligands further stabilize the two-dimensional supramolecular architecture of 1. Moreover, the magnetic property of 1 was investigated. In addition, natural bond orbital analysis was performed by the B3LYP/LANL2DZ method in Gaussian 09 Program. The calculation results show the obvious covalent interaction between the coordinated atoms and Ni(II) ion.

English

Physicochemical and potentially toxic metals statuses of surface water samples collected around the Yauri abattoir were examined. Health risk assessment of the toxicant via ingestion was interpreted by calculating the hazard quotient (HQ). The mean concentration values for total dissolved solid (TDS), total suspended solid (TSS), dissolved oxygen (DO), phosphate, and biochemical oxygen demand (BOD) were 1026.78, 565.22, 5.0, 8.89 and 484.64 mg/L respectively. The values are above those obtained for the control water sample as well as those of international safe limits for water. The values of pH (6.6), sulphate (86.91 mg/L), nitrate (41.45 mg/L) and chemical oxygen demand (COD) (903.30 mg/L) fell within world health organization maximum permissible limits for drinking water. The mean concentrations of Co (6.93 mg/L), Cu (14.45 mg/L), Fe (64.16 mg/L), and Zn (37.14 mg/L) were above both the control and WHO, EU and EPA safe limits for metals in water. On the other hand Cd (11.47 mg/L), Ni (35.49 mg/L), and Pb (41.94 mg/L) had a mean concentration values which are higher than the international standard limits and control water sample. The calculated values of HQ show that Cd, Co, Cu and Ni were of high risk, Fe with a medium and Pb and Zn are of low risk. Correlation coefficients revealed general positive and significant correlations between the pairs of metals in water. The results of this study showed some levels of pollution of the stream water indicating that the activities at the abattoir were contributing to the pollution load of water in the area. Key words: Yauri, abattoir, toxic metals, physicochemical.