Addition Of Nitrate Research Articles

Microbial induced mineral precipitations caused by nitrate treatment for souring control during microbial enhanced oil recovery (MEOR)

Microbiologically active environments, like oil reservoirs, can suffer a range of problems due to the presence of sulfate-reducing microorganisms. These include, but are not limited to: H2S formation, souring and corrosion. To prevent biogenic sulfate reduction, nitrate can be used as an environmentally friendly alternative to biocides. However, side effects of nitrate injection are sometimes observed but not well understood. In our study, we used original water from an onshore reservoir, where a microbial enhanced oil recovery (MEOR) application is planned, and investigated the effects of nitrate addition on H2S generation, mineral precipitation and microbiology. We observed that nitrate did inhibit H2S formation in most, but not all cases. During nitrate reduction, iron and calcite minerals precipitated over short- and long-term (10 or 160 days) incubations. This was caused by a nitrate-reducing group of bacteria belonging to the family Deferribacteraceae. Using dynamic sandpack setups and numerical modeling approaches with the simulator TOUGHREACT, we observed significant reduction in permeabilities (∼44×) suggesting injectivity issues over time in case nitrate is continuously added to the reservoir. Our study shows that nitrate-dependent processes, which were described separately for pure-cultures before, are also valid for natural mixed communities present in oil fields and underlines the complex interplay of microbial metabolisms associated with those communities.

Nitrogen inputs are more important than denitrifier abundances in controlling denitrification-derived N2O emission from both urban and agricultural soils

Cities are increasingly being recognized as important contributors in global warming, for example by increasing atmospheric nitrous oxide (N2O). However, urban ecosystems remain poorly understood due to their functional complexity. Further, few studies have documented the microbial processes governing the N2O emissions from urban soils. Here, a field study was performed to assess in situ N2O emissions in an urban and agricultural soil located in Xiamen, China. The mechanisms underlying the difference in N2O emission patterns in both soils were further explored in an incubation experiment. Field investigations showed that N2O emission (3.5–19.0 μg N2O-N m−2 h−1) from the urban soil was significantly lower than that from the agricultural soil (25.4–18,502.3 μg N2O-N m−2 h−1). Incubation experiments showed that the urban soil initially emitted lower denitrification-derived N2O because of the lower nirS (encoding nitrite reductases) abundances, whereas overall N2O accumulation during the incubation was mainly controlled by the initial nitrate content in soil. Nitrate addition in a short period (5 days) did not change the total bacterial and denitrifier abundances or the soil bacterial community composition, but significantly altered the relative distribution of some key genera capable of denitrification. Although the urban soil exhibited lower N2O emission than its agricultural counterpart in this study, the expanding urban green areas should be taken into account when building N2O emission reduction targets.

Estuarine algal responses to increasing nitrate concentrations during closed mouth conditions of oligotrophic systems: a laboratory microcosm experiment

Abstract The increasing incidence of eutrophication has potentially detrimental socio-economic and ecological consequences. This study aimed to elucidate the temporal dynamics of algal communities in response to increasing initial concentrations of inorganic nitrogen (particularly nitrate) – central components of eutrophication. A contained microcosm experiment was designed to mimic the conditions of shallow oligotrophic estuaries with high water residence times. Phytoplankton, microphytobenthos and filamentous algal community dynamics were observed over a 28-day experimental period under different nitrate regimes. Key observations included (1) accelerated filamentous algal growth, (2) rapid loss of phytoplankton biomass and abundance, and (3) reduced benthic diatom species diversity and richness in the “1.0 μm Nitrate Addition” treatment. Additionally, model results highlighted the positive relationship between filamentous algal growth and increased water temperature. From a global change perspective, the decline in microalgal abundance and diversity at the onset of filamentous algal growth in warm, N-enriched environments suggests a potential uncoupling of trophic pathways. However, the “Control” and “0.5 μm Nitrate Addition” treatments were similar in their algal responses, highlighting the ability of ecosystems to absorb small disturbances. Thus, it is critical that estuarine resilience is preserved to ensure continued provision of invaluable ecosystem services.

Enhanced permeation performance with incorporation of silver nitrate onto polymeric membrane

Enhancing membrane permeation is usually an important parameter in the membrane development for filtration. In this study, polysulfone membrane equipped with different concentration of silver nitrate (0.5-2.0 wt%) were fabricated by phase inversion and later be known as composite membrane (CM) followed by letter (A till F) to indicate membrane composition. This study will investigate the effect of silver nitrate concentration to membrane permeation. Membrane morphology was investigated via scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Based on SEM examination, all composite membrane exhibits sponge-like structure otherwise FTIR for composite membrane with silver nitrate (CM B till CM E) shows additional peak at 1149.57 and 1294.24 indicating silver nitrate presence. In permeability test, composite membrane (CM C) with 1.0wt% silver nitrate achieved 22.25 L/m2.h of flux, the highest among all the composite membrane configuration. Thus, the result implied the addition of silver nitrate can increase permeation performance though excessive content may reduce the performance up to 50% of flux reduction. This work provides a better understanding of silver nitrate implication toward membrane permeability therefore provide an insight to any application of silver nitrate in membrane composition.

Nitrogen deposition increases N2O emission from an N-saturated subtropical forest in southwest China

Nitrous oxide (N2O) is a major greenhouse gas, with elevated emission being reported from subtropical forests that receive high nitrogen (N) deposition. After 10 years of monthly addition of ammonium nitrate (NH4NO3) or sodium nitrate (NaNO3) to a Mason pine forest at Tieshanping, near Chongqing city in Southwest China, the simulated N deposition was stopped in October 2014. The results of soil N2O emissions monitoring in different seasons during the nitrogen application period showed that nitrogen addition significantly increased soil N2O emission. In general, the N2O emission fluxes were positively correlated to nitrate (NO3−) concentrations in soil solution, supporting the important role of denitrification in N2O production, which was also modified by environmental factors such as soil temperature and moisture. After stopping the application of nitrogen, the soil N2O emissions from the treatment plots were no longer significantly higher than those from the reference plots, implying that a decrease in nitrogen deposition in the future would cause a decrease in N2O emission. Although the major forms of N deposition, NH4+ and NO3−, had not shown significantly different effects on soil N2O emission, the reduction in NH4+ deposition may decrease the NO3− concentrations in soil solution faster than the reduction in NO3− deposition, and thus be more effective in reducing N2O emission from N-saturated forest soil in the future.

Influence of strong bases on the synthesis of silver nanoparticles (AgNPs) using the ligninolytic fungi Trametes trogii.

Silver nanoparticles (AgNPs) were biosynthesized using fungal extract of Trametes trogii, a white rot basidiomycete involved in wood decay worldwide, which produces several ligninolytic enzymes. According to previous studies using fungi, enzymes are involved in nanoparticles synthesis, through the so-called green synthesis process, acting as reducing and capping agents. Understanding which factors could modify nanoparticles’ shape, size and production efficiency is relevant. The results showed that under the protocol used in this work, this strain of Trametes trogii is able to synthesize silver nanoparticles with the addition of silver nitrate (AgNO3) to the fungal extract obtained with an optimal incubation time of 72 h and pH 13, using NaOH to adjust pH. The progress of the reaction was monitored using UV–visible spectroscopy and synthesized AgNPs was characterized by scanning electron microscope (SEM), through in-lens and QBDS detectors, and energy-dispersive X-ray spectroscopy (EDX). Additionally, SPR absorption was modeled using Mie theory and simple nanoparticles and core-shell configurations were studied, to understand the morphology and environment of the nanoparticles. This protocol represents a simple and cheap synthesis in the absence of toxic reagents and under an environmentally friendly condition.

Nitrate reduced arsenic redox transformation and transfer in flooded paddy soil-rice system

Inhibition of reductive transformation of arsenic (As) in flooded paddy soils is of fundamental importance for mitigating As transfer into food chain. Anaerobic arsenite (As(III)) oxidizers maintain As in less mobile fraction under nitrate-reducing conditions. In this study, we explored the dynamic profile of As speciation in porewater and As distribution among the pools of differential bioavailability in soil solid phase with and without nitrate treatment. In parallel, the abundance and diversity of As(III) oxidase gene (aioA) in flooded paddy soil with nitrate amendment was examined by quantitative PCR and aioA gene clone library. Furthermore, the impact of nitrate on As accumulation and speciation in rice seedlings was unraveled. With nitrate addition (25 mmol NO3− kg−1 soil), porewater As(III) was maintained at a consistently negligible concentration in the flooded paddy soil and the reductive dissolution of As-bearing Fe oxides/hydroxides was significantly restrained. Specifically, nitrate amendment kept 81% of total soil As in the nonlabile fraction with arsenate (As(V)) dominating after 30 days of flooding, compared to only 61% in the unamended control. Nitrate treatment induced 4-fold higher abundance of aioA gene, which belonged to domains of bacteria and archaea under the classes α-Proteobacteria (6%), ß-Proteobacteria (90%), ɣ-Proteobacteria (2%), and Thermoprotei (2%). By nitrate addition, As accumulation in rice seedlings was decreased by 85% with simultaneously elevated As(V) ratio in rice plant relative to control after 22 days of growth under flooded conditions. These results highlight that nitrate application can serve an efficient method to inhibit reductive dissolution of As in flooded paddy soils, and hence diminish As uptake by rice under anaerobic growing conditions.

Inhibitory Effect of Biologically Synthesized Silver Nanoparticle on Growth and Virulence of E. coli

Background: The production of novel antibiotics inhibiting virulence factors of pathogenic bacteria has emerged as a promising approach to combat the emergence of resistant strains. Acknowledging the harmful effect and considerable spread of pathogenic strains of Escherichia coli, this research aimed at investigating the inhibitory effects of biologically synthesized silver nanoparticles on the growth of E. coli and its negative impact on capsule formation as the virulence factor of the pathogen. Methods: Silver nanoparticles were synthesized by the addition of silver nitrate to a fresh culture of Shewanella oneidensis. The inhibitory effect of the nanoparticles on E. coli growth was investigated by serial microdilution method. The expression of alpha-hemolysin (hly) under nanoparticle treatment was quantitatively evaluated using a real-time PCR. The growth rate of E. coli under nanoparticles treatment was monitored at a 12-hour interval. Results: It was revealed that monodisperse spherical silver nanoparticles were produced to significantly inhibit the bacterial growth at a concentration of 50 μg/mL (MIC = 50 μg/mL). Furthermore, the expression of alpha-hemolysin (hly) was downregulated by the nanoparticles even at concentrations below the MIC value. Conclusions: In general, the research findings revealed that silver nanoparticles produced by green approach could be used as appropriate candidates for the development of new antibacterial medicines.

Fermentative production of soluble phosphorus fertilizer using paddy straw: an alternate to biomass burning

To mitigate environmental impacts caused by illegal burning of paddy straw or stubble in the open fields, an alternate and economical technology for microbial degradation of lignocellulosic biomass and production of soluble phosphorus fertilizer was explored. Low-grade Mussoorie rock phosphate and Udaipur rock phosphate supplemented paddy straw was exploited as solid-state fermentation medium for the fungal-mediated release of soluble phosphorus by phosphate dissolving and cellulase producing strains of Aspergillus niger (ITCC 6719) and Aspergillus awamori (F18). Optimization of process parameters revealed that elemental composition of rock phosphate and its dose are important to affect the per cent yield of soluble phosphorus. Addition of ammonium sulphate or ammonium nitrate or urea to rock phosphate supplemented paddy straw inhibited the release of soluble phosphorus. Contrarily, adding 10% wheat bran (w/w) into paddy straw-rock phosphate mixture and its subsequent fungal inoculation at 10% (v/w) resulted in maximum solubilization (37–38%) of rock phosphate on 21st day of incubation. The fermented extract of this mixture also recorded the highest cellulase activity titre (76.32 IU ml−1) after 3 weeks of fermentation. Soil–plant interaction studies with wheat crop revealed that application of this fermented mixture to soil not only improved the plant biomass but also increased the soil available phosphorus content by ~ twofold, compared to treatments receiving recommended chemical phosphorus. Bio-processing of rock phosphate using wheat bran-amended paddy straw as fermentation substrate can provide an economical and alternate soluble fertilizer for enhanced crop phosphorus nutrition.

Glycosylated tris-bipyridine ferrous complexes for probing a mechanism behind carbohydrate-carbohydrate interactions: Spatial carbohydrate packing of glycoclusters changes on additions of salts in carbohydrate- and anion-dependent manners

2,2′-Bipyridines containing two β-maltoside, β-lactoside, or β-isomaltoside appendages were prepared and successively complexed with ferrous ion to afford hexavalent glycoclusters having tris-bipyridine ferrous complex cores. Each of these metalloglycoclusters showed unique UV–vis and CD spectral changes upon addition of chloride, nitrate, and sulfate salts in carbohydrate- and anion-dependent manners. The results indicate that spatial carbohydrate packing of the metalloglycoclusters changes upon addition of these anions and that different anions stabilize different carbohydrate packings. Furthermore, the sulfates specifically enhance the rheological properties of aqueous solutions containing the metalloglycocluster containing β-lactoside appendages.

Pectin-graft-poly(2-acrylamido-2-methyl-1-propane sulfonic acid) silver nanocomposite hydrogel beads: evaluation as matrix material for sustained release formulations of ketoprofen and antibacterial assay

Pectin-graft-poly(2-acrylamido-2-methyl-1-propane sulfonic acid) (Pec-g-PAMPS) gel was made in the form of beads by subjecting the solution containing pectin (Pec), 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) and ammonium peroxodisulphate to microwave irradiation followed by ionic crosslinking in CaCl2 solution. Gel beads containing silver nanoparticles were also prepared by the same method but with the addition of silver nitrate and trisodium citrate solution prior to microwave irradiation. The synthesized Pec-g-PAMPS and its silver nanocomposite (Pec-g-PAMPS-Ag) gel beads were characterized using FTIR, TGA, XRD, SEM, EDS and TEM techniques. The effect of incorporation of Ag NPs on the biological activity of Pec-g-PAMPS was studied by zone inhibition method considering two bacterial strains namely E. coli and B. subtilis. The nanocomposite gel exhibited higher antibacterial activity compared to the parent gel, which was comparable with the standard drug, Streptomycin. The in vitro drug release profiles of the parent gel and its composite were analyzed using Ketoprofen (KF) to study the effect of incorporation of Ag NPs on the drug release behavior of the Pec-g-PAMPS. The presence of silver nanoparticles enhanced both swelling of the gel beads and the extent of drug release significantly.

Mechanistic Study of the NO + NH4NO3 Reaction on H- and Fe/H-BEA Zeolites Using 15N and 18O Labeled Species

Reduction of NO by NH3 over metal-promoted zeolites represents the principal reaction in the selective catalytic reduction (SCR) technology for NOx removal from Diesel engine exhausts. It has been established that addition of ammonium nitrate (AN) to the reaction mixture substantially enhances the rate of this reaction, decreasing the temperature necessary for an efficient deNOx process. Nevertheless, the nature of this effect has not been completely elucidated. To investigate the NO + AN reaction mechanism, we have used individual reactants labeled with either 15N or 18O (or both isotopes), thus obtaining an experimental background for proposing the route of the SCR accelerated by AN addition. For this study, we have used as the catalysts H-BEA and Fe/H-BEA zeolites with various Si/Al ratios and various amounts and states of the iron species.

Index for nitrate dosage calculation on sediment odor control using nitrate-dependent ferrous and sulfide oxidation interactions

Nitrate-driven sulfide and ferrous oxidation have received great concern in researches on sediments odor control with calcium nitrate addition. However, interrelations among sulfide oxidation, ferrous oxidation and their associated microbes during the nitrate reduction process are rarely reported. In this work, a nNO3/n(S+Fe) ratio (mole ratio of NO3− concentration to S2− and Fe2+ concentration) was first introduced as an index for calcium nitrate dosage calculation. Then certain amount of calcium nitrate was added to four sediment systems with various sulfide and ferrous initial concentration to create four gradients of nNO3/n(S+Fe) ratio (0.6, 0.9, 1.5 and 2.0) for treatment. Furthermore, the significant variations of sulfide and ferrous oxidation, microbial diversity and community structure were observed. The results revealed that at low nNO3/n(S+Fe) ratio (0.6 and 0.9) systems, sulfide seemed prior to ferrous to be oxidized and no obvious ferrous oxidation occurred. Meanwhile, sulfide oxidizing associated genus Sulfurimonas sp. became dominant in these systems. In contrast, sulfide and ferrous oxidation rate increased when nNO3/n(S+Fe) ratio reached 1.5 and 2.0 (two and three times of theoretically required amount for sulfide and ferrous oxidation), which made Thiobacillus sp. more dominant than Sulfurimonas sp. Hence, when nNO3/n(S+Fe) ratio of 1.5 and 2.0 were used, sulfide and ferrous could be simultaneously oxidized and no sulfide regeneration appeared in two months. These results demonstrated that for sulfide- and ferrous-rich sediment treatment, the nitrate consumed by ferrous oxidation should be taken into account when calculating the nitrate injecting dosage. Moreover, nNO3/n(S+Fe) ratio was feasible as a key parameter to control the oxidation process and as an index for calcium nitrate dosage calculation.

Overexpression of a High-Affinity Nitrate Transporter OsNRT2.1 Increases Yield and Manganese Accumulation in Rice Under Alternating Wet and Dry Condition.

Nitrate and manganese (Mn) are necessary elements for the growth and development of rice in paddy soil. Under physiological conditions, we previously reported that the uptake of Mn in roots can be improved by the addition of external nitrate but not ammonium. To investigate the mechanism(s) of this phenotype, we produced plant lines overexpressing OsNRT2.1 and assessed Mn uptake under alternating wet and dry (AWD) and waterlogged (WL) conditions. Under AWD condition, we observed a 31% reduction in grain yields of wild type (WT) plants compared to WL condition. Interestingly, the overexpression of OsNRT2.1 could recover this loss, as OsNRT2.1 transgenic lines displayed higher grain yields than WT plants. We also observed 60% higher grain Mn in the transgenic lines in AWD condition and approximately 30% higher Mn in the grain of transgenic lines in WL condition. We further found that the overexpression of OsNRT2.1 did not alter Mg and Fe in the seeds in either growth condition. The reasons for the increased Mn content in OsNRT2.1 transgenic seeds in AWD condition could be explained by the elevated expression of OsNRAMP family genes including OsNRAMP3, OsNRAMP5, and OsNRAMP6 in node I, the panicle-neck, and the flag leaves. The mechanism(s) underpinning the upregulation of these genes requires further investigation. Taken together, our results provide a new function of OsNRT2.1 in improving rice yields and grain Mn accumulation during water-saving cultivation patterns. This represents a new strategy for maintaining yield and improving food quality in a sustainable agricultural system.

Effect of dietary nitrate on enteric methane emissions, production performance and rumen fermentation of dairy cows grazing kikuyu-dominant pasture during summer

Dietary nitrate supplementation is an effective methane (CH4) mitigation strategy in total mixed ration based diets fed to ruminants. To date, limited information is available on the effect of dietary nitrate on CH4 production from grazing dairy cows. Fifty-four multiparous Jersey cows were subjected to a randomised complete block design (blocked according to milk yield, days in milk and parity) to evaluate the effect of three dietary nitrate levels on enteric CH4 emissions and cow production performance. Additionally, six rumen-cannulated cows in a replicated 3 × 3 Latin square design were used in a rumen study. Dietary treatments consisted of concentrate fed at 5.4 kg of DM/cow per day containing one of three levels of dietary nitrate: 0 g (control), 11 g (low nitrate), and 23 g of nitrate/kg of dry matter (DM; high nitrate). Cows grazed late-summer pasture containing approximately 3 g of nitrate/kg of DM. Concentrates were formulated to be isonitrogenous, by substituting urea, and isoenergetic. Cows were gradually adapted to concentrates over a 3-wk period before the onset of a 57-d experimental period. Enteric CH4 emissions and total dry matter intake (DMI) from 11 cows per treatment were measured during one 6-d measurement period using the sulphur hexafluoride tracer gas technique. Individual pasture DMI was determined using TiO2 and indigestible neutral detergent fibre (NDF). Milk yield decreased by approximately 12% when feeding the high nitrate diet compared with the control and low nitrate diets. Although total DMI was unaffected by treatment, concentrate DMI decreased linearly (5.5–3.7 kg/d) while pasture DMI increased linearly (9.1–11.4 kg/d) with increasing dietary nitrate addition. Methane production (313–280 g/d), CH4 yield (21.8–18.7 g/kg of DMI) and CH4 energy per gross energy intake (6.9–5.9%) tended to decrease linearly with increasing dietary nitrate addition. Diurnal ruminal pH of the high nitrate group was greater, for selective periods after concentrate feeding, than the control and low nitrate groups. Spot sample ruminal pH (6.2–6.3) tended to increase while total volatile fatty acid (VFA) concentration (99.9–104 mM/L) increased quadratically with increasing dietary nitrate addition. Individual VFA concentrations were unaffected by treatment. Rate of NDF disappearance (2.4–2.8%/h) after 18 h of ruminal incubation tended to increase quadratically with increasing dietary nitrate addition. Dietary nitrate fed to grazing dairy cows tended to decrease CH4 emissions while improving the fibrolytic environment of the rumen. However, when feeding high levels of dietary nitrate a decrease in milk yield could be expected due to a decrease in concentrate DMI.

Microbial community structure in deep natural gas-bearing aquifers subjected to sulfate-containing fluid injection

In the natural gas field located in central Japan, high concentrations of natural gases and iodide ions are dissolved in formation water and commercially produced in deep aquifers. In the iodine recovery process, the produced formation water is amended with sulfate, and this fluid is injected into gas-bearing aquifers, which may lead to infrastructure corrosion by hydrogen sulfide. In this study, we examined the microbial community in aquifers subjected to sulfate-containing fluid injection. Formation water samples were collected from production wells located at different distances from the injection wells. The chemical analysis showed that the injection fluid contained oxygen, nitrate, nitrite and sulfate, in contrast to the formation water, which had previously been shown to be depleted in these components. Sulfur isotopic analysis indicated that sulfate derived from the injection fluid was present in the sample collected from near the injection wells. Quantitative and sequencing analysis of dissimilatory sulfite reductase and 16S rRNA genes revealed that sulfate-reducing bacteria (SRB), sulfur-oxidizing bacteria, and anaerobic methanotrophic archaea (ANME) in the wells located near injection wells were more abundant than those in wells located far from the injection wells, suggesting that fluid injection stimulated these microorganisms through the addition of oxygen, nitrate, nitrite and sulfate to the methane-rich aquifers. The predominant taxa were assigned to the ANME-2 group, its sulfate-reducing partner SEEP-SRB1 cluster and sulfur-oxidizing Epsilonproteobacteria. These results provide important insights for future studies to support the development of natural gas and iodine resources in Japan.

Acetate Additions Stimulate CO2 and CH4 Production from Urban Wetland Soils

Core Ideas Carbon additions to three varied wetland soils enhanced both carbon dioxide and methane production. Methane production was negatively correlated to salinity with and without carbon additions. Microbial community representation was associated with salinity not treatment. Wetlands in close proximity to urban centers receive significant inputs of dissolved organic carbon (C) and nitrogen (N) from runoff, sewage overflow, and treated wastewater. Additions of C and N may impact greenhouse gas (GHG) production rates from temperate wetland ecosystems, which are considered a large sink for atmospheric carbon dioxide (CO2). We hypothesized that microbial activity in these anaerobic ecosystems was limited by the availability of labile C which provides electron donors to support microbial metabolism. To test this hypothesis, CO2 and methane (CH4) production rates were quantified with a series of soil incubations from three wetland sites located across a salinity gradient in the Hudson River Estuary (HRE). Acetate additions to soils enhanced CO2 (2×) and CH4 (>125×) production rates from soil slurries among all wetland soils vs. no amendment controls. Enhanced CH4 production was also inversely correlated (r2 = 0.81) to the salinity of sampled soils. In contrast, neither nitrate (NO3–) nor ammonium (NH4+) additions had a significant effect on CO2 or CH4 production rates when added alone or with acetate. Greater CO2 and CH4 production from soils with added acetate were associated with lower redox potential, increased pH, and increased hydrogen sulfide concentrations. The wetland sites had dissimilar methanogenic and sulfate reducing communities, which likely contributed to differences in CO2 and CH4 production among wetland sites. These data suggest that C loadings in wetland soils enhance both CO2 and CH4 efflux and potentially limit the capacity of wetlands impacted by anthropogenic pollution to act as C sinks.

Nitrate addition inhibited methanogenesis in paddy soils under long-term managements

Rice fields are a major source of atmospheric methane (CH<sub>4</sub>). Nitrate has been approved to inhibit CH<sub>4</sub> production from paddy soils, while fertilization as well as water management can also affect the methanogenesis. It is unknown whether nitrate addition might result in shifts in the methanogenesis and methanogens in paddy soils influenced by different practices. Six paddy soils of different fertilizer types and groundwater tables were collected from a long-term experiment site. CH<sub>4</sub> production rate and methanogenic archaeal abundance were determined with and without nitrate addition in the microcosm incubation. The structure of methanogenic archaeal community was analysed using the PCR-DGGE (polymerase chain reaction denaturing gradient gel electrophoresis) and pyrosequencing. The results showed that nitrate addition significantly decreased the CH<sub>4</sub> production rate and methanogenic archaeal abundance in all six paddy soils by 70–100% and 54–88%, respectively. The quantity, position and relative intensity of DGGE bands exhibited differences when nitrate was added. Nitrate suppressed the growth of methanogenic archaeal species affiliated to Methanosaetaceae, unidentified Euryarchaeota, Thaumarchaeota and Methanosarinaceae. The universal inhibition of nitrate addition on the methanogenesis and methanogens can be adopted as a practice of mitigating CH<sub>4</sub> emission in paddy soils under different fertilization and water managements.

Effect of accelerators with waste material on the propertiesof cement paste and mortar

Accelerators are used to speed up the construction by accelerating the setting time which helps in early removal of formwork thus leading to faster construction rate. Admixtures are used in mortar and concrete during or after mixing to improve certain properties of material which cannot be achieved in conventional cement mortar and concrete. The various industrial by products make nuisance and are hazardous to ecosystem as well. These wastes can be used in the construction industries to reduce the consumption of cement/aggregates, cost; and save the energy and environment by utilising waste and eliminate their disposal problem as well. The effect of calcium nitrate and triethanolamine (TEA) as accelerators and marble powder (MP) as waste material on the various properties of cement paste and mortar has been studied in the present work. The replacement ratio of MP was 0-10% @ 2.5% by weight of cement. The addition of calcium nitrate was 0% and 1%; and variation of addition of TEA was 0-0.1@ 0.025% and 0.1-1.0@ 0.1% by weight of cement. On the basis of setting time, some mix proportions were selected and further investigated. Setting time and soundness of cement paste; compressive strength and microstructure of mortar mix of selected mix proportions were studied experimentally at 3, 7 and 28 days aging. Results showed that use of MP, calcium nitrate, TEA and their combination reduced setting time of cement paste for all the mixes. Addition of calcium nitrate increased the compressive strength at all curing ages while MP and TEA decreased the compressive strength. The mechanism of additives was discussed through scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis of the specimens.

Effects of nitrate supplementation and forage level on gas production, nitrogen balance and dry-matter degradation in sheep

The present study was conducted to evaluate the effect of nitrate supplementation on dry-matter (DM) degradation and ruminal fermentation parameters by using in vitro gas production and in situ technique. In vitro gas production and in situ DM degradation in the presence or absence of nitrate were recorded at all incubation times. At all incubation times, diets incubated with nitrate gave a significantly lower gas production than did the other diets, except at 2-h incubation. Ruminal DM degradation did not differ among the experimental treatments. Furthermore, at most incubation times, total volatile fatty acids in diets containing nitrate were lower than those in the other treatments. Nitrate supplementation considerably increased gas production from the insoluble fraction, whereas it decreased gas production from the quickly soluble fraction, and potential gas production. Moreover, in all incubations, there were significant correlations between gas production and in situ DM-degradation parameters. The control diet had the greatest retained nitrogen content, but the diets containing nitrate had the greatest faecal nitrogen. The results showed that nitrate addition resulted in a lower gas production and volatile fatty acid production in in vitro assay. It was concluded that considering the strong posetive relationship between the two methodologies, the degradability parameters can be predicted from obtained gas production.