Potential use of karanjin (3-methoxy furano-2′,3′,7,8-flavone) as a nitrification inhibitor in different soil types
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Karanjin, a furanoflavonoid (3-methoxy furano – 2 ′ , 3 ′ , 7, 8-flavone), is obtained from the seeds of karanja tree (Pongamia glabra Vent.), which is reported to have nitrification inhibitory properties but has been tested in few soil types. Efficiency of karanjin as a nitrification inhibitor in seven different soils of India was tested in a laboratory incubation study. The soils (800 g) were adjusted to field capacity moisture content, fertilized with urea and urea combined with karanjin at a rate of 20% of applied urea-N (100 mg kg − 1 soil) and incubated at 35°C for a period of 7 weeks, during which urea [CO(NH2)2], ammonium (NH4 + ), nitrite (NO2 − ) and nitrate (NO3 − ) content in the soils was measured periodically and nitrification inhibition at different stages was calculated. Urea hydrolysis was almost complete within 72 h of application in all the soils and was not affected by karanjin. Karanjin had conserved ammonium in all the soils at all stages and nitrate formation was effectively minimized. Nitrite in soils was short-lived and low. Nitrification inhibition by karanjin remained high for a period of approximately 6 weeks, decreased with time and ranged from 9 – 76% for all the soils. The study shows that this plant product can be an effective nitrification inhibitor in several types of soil.Keywords:
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Abstract Nitrification in Lima loam, pH 7.2, was not affected by continuous exposure of the soil to 0.5 ppm of SO 2 or to brief exposures to higher SO 2 levels. Such treatment did not increase the levels of soluble K, Mg, Ca, Mn, Fe, and Al. Intermittent exposure of Hudson silty clay loam, pH 5.0, to SO 2 reduced the rate of nitrate formation. Continuous fumigation of the acid soil with 10 ppm of SO 2 decreased the rate of nitrification, and continuous fumigation with as little as 1.0 ppm increased the quantity of soluble Mn and Fe. Continuous fumigation of Lima loam with 5 ppm NO 2 inhibited the rate of ammonium disappearance, led to greater rates of nitrate formation, and resulted in nitrite accumulation. Nitrite at a level of 30 µ g N/g of soil also reduced the rate of ammonium disappearance. The results demonstrate that nitrification in certain soils could be inhibited in areas acutely polluted with SO 2 and NO 2 .
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This thesis concerns nitrification in different environments. Nitrification is a biochemical reaction of ammonium into nitrite and further nitrate. In drinking water distribution systems (DWDSs), nitrite formed in nitrification can be problematic because it is potentially harmful to humans. On the other hand, in wastewater treatment plants (WWTPs), nitrification is utilized in biological ammonium removal from wastewater. This thesis concerns the spatial and seasonal inspection of nitrite formation in full-scale DWDSs. In DWDSs, nitrite is formed by an added disinfection chemical, monochloramine, or ammonium in the raw water. Furthermore, this thesis inspects nitrification in relation to organic matter, in both WWTPs and in laboratory-scale simulated distribution systems (SDSs). The spatial analysis of water quality revealed that nitrite was forming rapidly after leaving the water treatment plant (WTP) in the DWDSs. The nitrite concentrations tended to be low in stagnating water. The normal low dose of monochloramine (0.35–0.4 mgCl2 L-1) was not high enough to prevent nitrite formation; however, it limited the maximum nitrite concentrations. Nitrite concentrations exhibited seasonal peaks either in the warm season or cold season, or there was no observable seasonal peak. The key drivers causing seasonality were water temperature and water age. The nitrite peaks in the cold season were caused by the decelerated ammonium oxidation. The dominant reaction at low water ages was ammonium oxidation into nitrite; and at high water ages, it was nitrite oxidation into nitrate. These results emphasize comprehensive and year-round nitrite monitoring in the DWDSs. In wastewater treatment, ammonium removal via nitrification was unexpectedly enhanced when the soluble organic matter concentrations were increased with pre-fermentation, retrofitted in a previously used pre-sedimentation basin. However, upon closer inspection, it was revealed that the organic load into the nitrification basin was reduced in the pre-fermentation line by the preceding denitrification and biological phosphorus removal, compared to the pre-sedimentation line. In non-disinfected conditions of tap water, decreasing the natural organic matter (NOM) in the water (TOC 1.0 mg L-1) prevented nitrite formation in SDSs, compared to unreduced NOM (TOC 1.6 mg L-1). When the results were interpreted with a pseudo first order reaction rate model, it was observed that the decreased nitrite concentrations were a result of enhanced nitrite oxidation. The maximum nitrite concentrations were strongly dependent on the ratio of the ammonium and nitrite oxidation activities. This study supports enhanced removal of NOM at the WTPs to also decrease the potentially harmful nitrite concentrations. The results the thesis provide more possibilities to control nitrification in DWDSs and at WWTPs.; Tama vaitoskirja kasittelee nitrifikaatiota erilaisissa ymparistoissa. Nitrifikaatiossa ammoniumtyppi hapettuu biokemiallisesti nitriitiksi ja edelleen nitraatiksi. Talousveden…
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Nitrobacter
Nitrosomonas
Nitrosomonas europaea
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Nitrogen Cycle
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Abstract : Two soil samples from an on-going field study of land application of municipal wastewater were spiked with low levels of ammonium to determine the effect of temperature on nitrification kinetics. The concentrations of ammonium and nitrite-plus-nitrate, and the number of autotrophic ammonium and nitrite oxidizers were monitored periodically during the study. There was a lag period prior to nitrite-plus-nitrate production at all temperatures, and the length of this lag period was temperature-dependent, with the longest period occurring at the lowest temperature. The maximum rate of nitrification increased with temperature as expected. While nitrite-plus-nitrate production appeared logarithmic, suggesting a growing nitrifier population, the MPN counts of the nitrifiers did not exhibit logarithmic growth. To study the effect of soil pH on nitrification kinetics, soil samples from field plots having the same soil type but different pHs (4.5, 5.5, and 7.0) were spiked with low levels of ammonium and the rate of nitrite-plus-nitrate production was measured. The maximum rate of nitrification was greater at pH 5.5 than at 4.5. Unexpectedly rapid disappearance of ammonium, nitrite and nitrate, caused by immobilization, obscured the expected effects of pH on the nitrification rate at the highest pH.
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Accurate assessments of exposure to nitrate in drinking water is a crucial part of epidemiological studies investigating long-term adverse human health effects. However, since drinking water nitrate measurements are usually collected for regulatory purposes, assumptions on (1) the intra-distribution system variability and (2) short-term (seasonal) concentration variability have to be made. We assess concentration variability in the distribution system of nitrate, nitrite, and ammonium, and seasonal variability in all Danish public waterworks from 2007 to 2016. Nitrate concentrations at the exit of the waterworks are highly correlated with nitrate concentrations within the distribution net or at the consumers’ taps, while nitrite and ammonium concentrations are generally lower within the net compared with the exit of the waterworks due to nitrification. However, nitrification of nitrite and ammonium in the distribution systems only results in a relatively small increase in nitrate concentrations. No seasonal variation for nitrate, nitrite, or ammonium was observed. We conclude that nitrate measurements taken at the exit of the waterworks are suitable to calculate exposures for all consumers connected to that waterworks and that sampling frequencies in the national monitoring programme are sufficient to describe temporal variations in longitudinal studies.
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For economic and efficient nitrogen removal from wastewater treatment plants via simultaneous nitrification and denitrification the nitrification process should stop at the level of nitrite such that nitrite rather than nitrate becomes the substrate for denitrification. This study aims to contribute to the understanding of the conditions that are necessary to improve nitrite reduction over nitrite oxidation. Laboratory sequencing batch reactors (SBRs) were operated with synthetic wastewater containing acetate as COD and ammonium as the nitrogen source. Computer controlled operation of the reactors allowed reproducible simultaneous nitrification and denitrification (SND). The oxygen supply was kept precisely at a low level of 0.5 mgL(-1) and bacterial PHB was the only electron donor available for denitrification. During SND little nitrite or nitrate accumulated (< 20% total N), indicating that the reducing processes were almost as fast as the production of nitrite and nitrate from nitrification. Nitrite spiking tests were performed to investigate the fate of nitrite under different oxidation (0.1-1.5 mgL(-1) of dissolved oxygen) and reduction conditions. High levels of reducing power were provided by allowing the cells to build up to 2.5 mM of PHB. Nitrite added was preferentially oxidised to nitrate rather than reduced even when dissolved oxygen was low and reducing power (PHB) was excessively high. However, the presence of ammonium enabled significant reduction of nitrite under low oxygen conditions. This is consistent with previous observations in SBR where aerobic nitrite and nitrate reduction occurred only as long as ammonium was present. As soon as ammonium was depleted, the rate of denitrification decreased significantly. The significance of the observed strongly stimulating effect of ammonium on nitrite reduction under SND conditions is discussed and potential consequences for SBR operation are suggested.
Aerobic denitrification
Sequencing batch reactor
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Concentrations of ammonium plus nitrite in Lake Ontario were highly correlated with ammonium regeneration from zooplankton excretion (r = 0.966), inferring that elevated nitrite concentrations result from nitrification. Nitrapyrin-sensitive dark 14 C-labeled bicarbonate assays confirmed high rates of nitrification by chemoautotrophic bacteria. 15 N-labeled nitrate experiments showed that nitrate, not ammonium, was the principal form of N used for total microbial protein synthesis. Size fractionation experiments also suggested that small cells were responsible for most of the ammonium uptake, while large cells used mostly nitrate. Nitrate depletion in the surface waters during summer stratification resulted from movement to particulate N, nitrite, and ammonium as well as losses in particulate N due to sedimentation. At least one third, however, was unaccounted for (i.e. 30 mg N∙m −2 ∙d −1 ) and may have been converted to protein which would move up the food chain to larger organisms (e.g. fish) not sampled during conventional water chemistry. Nitrous oxide profiles showed that nitrate losses through denitrification are unlikely to occur. Consequently, unless nitrate loading to Lake Ontario is reduced, nitrate concentrations should be expected to continue to increase.
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In order to understand the mechanism of nitrification in limy soil for different exogenous nitrogen sources,the study was conducted to investigate the effects of different additive amounts and nitrogen sources on the nitrification in fresh Cal-Ustic Isohumasols by using the plot experiment,and the corresponding model was obtained.The results show that the curve between the ammonium nitrate consumption rate and nitrogen nitrate increasing rate can be described as an S shape,and the ammonium nitrate consumption rate is higher than the nitrogen nitrate increasing rate.The ammonium nitrate consumption rate and nitrogen nitrate increasing rate are positively correlated with the nitrogen addition.Except the nitrifying bacteria,other organisms' absorptions of ammonium nitrate and nitrogen nitrate are positively related to the addition of nitrogen nitrate.Applications of different nitrogen amounts have great influences on the nitrification in soils.When the nitrogen addition is N 75 mg/kg soil,the nitrification is more completely.SO2-4 can hasten the nitrification rate and can also improve the bio-availabilities of ammonium nitrate and nitrogen nitrate for other organisms.
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Dietary Nitrate
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