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1.
Hongyu Wang Yaping Ye Jinni Sai Dan Chen Kai Yang Jun Zhou 《Geomicrobiology journal》2016,33(6):505-512
Static experiments were conducted to investigate the effects of environmental factors on nitrate (NO3?-N)-removal efficiency, such as NO3?-N loading, pH value, C/N ratio and temperature in activated sludge using Fe (II) as electron donor. The results demonstrated that the average denitrification rate increased from 1.25 to 2.23 mg NO3?-N/(L·h) with NO3?-N loading increased from 30 to 60 mg/L. When pH increased from 7 to 8, the concentration of NO3?-N and nitrite (NO2?-N) in effluent were all maintained at quite low levels. C/N ratio had little impact on denitrification process, i.e., inorganic carbon (C) source could still be enough for denitrification process with C/N ratio as low as 5. Temperature had a significant effect on the denitrification efficiency, and NO3?-N removal efficiency of 92.03%, 96.77%, 97.67% and 98.23% could be obtained with temperature of 25°C, 30°C, 35°C and 40°C, respectively. SEM, XRD and XRF analysis was used to investigate microscopic surface morphology and chemical composition of the denitrifying activated sludge, and mechanism of the nitrate-dependent anaerobic ferrous oxidation (NAFO) bacterias could be explored with this research. 相似文献
2.
A pilot-scale, engineered poplar tree vadose zone system was utilized to determine effluent nitrate (NO3?) and ammonium concentrations resulting from intermittent dosing of a synthetic wastewater onto sandy soils at 4.5°C. The synthetic wastewater replicated that of an industrial food processor that irrigates onto sandy soils even during dormancy which can leave groundwater vulnerable to NO3? contamination. Data from a 21-day experiment was used to assess various Hydrus model parameterizations that simulated the impact of dormant roots. Bromide tracer data indicated that roots impacted the hydraulic properties of the packed sand by increasing effective dispersion, water content and residence time. The simulated effluent NO3? concentration on day 21 was 1.2 mg-N L?1 in the rooted treatments compared to a measured value of 1.0 ± 0.72 mg-N L?1. For the non-rooted treatment, the simulated NO3? concentration was 4.7 mg-N L?1 compared to 5.1 ± 3.5 mg-N L?1 measured on day 21. The model predicted a substantial “root benefit” toward protecting groundwater through increased denitrification in rooted treatments during a 21-day simulation with 8% of dosed nitrogen converted to N2 compared to 3.3% converted in the non-rooted test cells. Simulations at the 90-day timescale provided similar results, indicating increased denitrification in rooted treatments. 相似文献
3.
John Karl Böhlke Ronald C. Antweiler Judson W. Harvey Andrew E. Laursen Lesley K. Smith Richard L. Smith Mary A. Voytek 《Biogeochemistry》2009,93(1-2):117-141
Denitrification is an important net sink for NO3 ? in streams, but direct measurements are limited and in situ controlling factors are not well known. We measured denitrification at multiple scales over a range of flow conditions and NO3 ? concentrations in streams draining agricultural land in the upper Mississippi River basin. Comparisons of reach-scale measurements (in-stream mass transport and tracer tests) with local-scale in situ measurements (pore-water profiles, benthic chambers) and laboratory data (sediment core microcosms) gave evidence for heterogeneity in factors affecting benthic denitrification both temporally (e.g., seasonal variation in NO3 ? concentrations and loads, flood-related disruption and re-growth of benthic communities and organic deposits) and spatially (e.g., local stream morphology and sediment characteristics). When expressed as vertical denitrification flux per unit area of streambed (U denit, in μmol N m?2 h?1), results of different methods for a given set of conditions commonly were in agreement within a factor of 2–3. At approximately constant temperature (~20 ± 4°C) and with minimal benthic disturbance, our aggregated data indicated an overall positive relation between U denit (~0–4,000 μmol N m?2 h?1) and stream NO3 ? concentration (~20–1,100 μmol L?1) representing seasonal variation from spring high flow (high NO3 ?) to late summer low flow (low NO3 ?). The temporal dependence of U denit on NO3 ? was less than first-order and could be described about equally well with power-law or saturation equations (e.g., for the unweighted dataset, U denit ≈26 * [NO3 ?]0.44 or U denit ≈640 * [NO3 ?]/[180 + NO3 ?]; for a partially weighted dataset, U denit ≈14 * [NO3 ?]0.54 or U denit ≈700 * [NO3 ?]/[320 + NO3 ?]). Similar parameters were derived from a recent spatial comparison of stream denitrification extending to lower NO3 ? concentrations (LINX2), and from the combined dataset from both studies over 3 orders of magnitude in NO3 ? concentration. Hypothetical models based on our results illustrate: (1) U denit was inversely related to denitrification rate constant (k1denit, in day?1) and vertical transfer velocity (v f,denit, in m day?1) at seasonal and possibly event time scales; (2) although k1denit was relatively large at low flow (low NO3 ?), its impact on annual loads was relatively small because higher concentrations and loads at high flow were not fully compensated by increases in U denit; and (3) although NO3 ? assimilation and denitrification were linked through production of organic reactants, rates of NO3 ? loss by these processes may have been partially decoupled by changes in flow and sediment transport. Whereas k1denit and v f,denit are linked implicitly with stream depth, NO3 ? concentration, and(or) NO3 ? load, estimates of U denit may be related more directly to field factors (including NO3 ? concentration) affecting denitrification rates in benthic sediments. Regional regressions and simulations of benthic denitrification in stream networks might be improved by including a non-linear relation between U denit and stream NO3 ? concentration and accounting for temporal variation. 相似文献
4.
Influence of bioturbation on denitrification and dissimilatory nitrate reduction to ammonium (DNRA) in freshwater sediments 总被引:2,自引:0,他引:2
Intensive agriculture leads to increased nitrogen fluxes (mostly as nitrate, NO3 ?) to aquatic ecosystems, which in turn creates ecological problems, including eutrophication and associated harmful algal blooms. These problems have focused scientific attention on understanding the controls on nitrate reduction processes such as denitrification and dissimilatory nitrate reduction to ammonium (DNRA). Our objective was to determine the effects of nutrient-tolerant bioturbating invertebrates (tubificid oligochaetes) on nitrogen cycling processes, specifically coupled nitrification–denitrification, net denitrification, DNRA, and biogeochemical fluxes (O2, NO3 ?, NH4 +, CO2, N2O, and CH4) in freshwater sediments. A mesocosm experiment determined how tubificid density and increasing NO3 ? concentrations (using N15 isotope tracing) interact to affect N cycling processes. At the lowest NO3 ? concentration and in the absence of bioturbation, the relative importance of denitrification to DNRA was similar (i.e., 49.6 and 50.4 ± 8.1 %, respectively). Increasing NO3 ? concentrations in the control cores (without fauna) stimulated denitrification, but did not enhance DNRA, which significantly altered the relative importance of denitrification compared to DNRA (94.6 vs. 5.4 ± 0.9 %, respectively). The presence of tubificid oligochaetes enhanced O2, NO3 ?, NH4 + fluxes, greenhouse gas production, and N cycling processes. The relative importance of denitrification to DNRA shifted towards favoring denitrification with both the increase in NO3 ? concentrations and the increase of bioturbation activity. Our study highlights that understanding the interactions between nutrient-tolerant bioturbating species and nitrate contamination is important for determining the nitrogen removal capacity of eutrophic freshwater ecosystems. 相似文献
5.
Enhanced biological denitrification of high concentration of nitrite with supplementary carbon source 总被引:3,自引:0,他引:3
Nitrite accumulates during biological denitrification processes when carbon sources are insufficient. Acetate, methanol, and ethanol were investigated as supplementary carbon sources in the nitrite denitrification process using biogranules. Without supplementary external electron donors (control), the biogranules degraded 200 mg l?1 nitrite at a rate of 0.27 mg NO2–N g?1?VSS h?1. Notably, 1,500 mg l?1 acetate and 700 mg l?1 methanol or ethanol enhanced denitrification rates for 200 mg l?1 nitrite at 2.07, 1.20, and 1.60 mg NO2–N g?1?VSS h?1, respectively; these rates were significantly higher than that of the control. The sodium dodecyl sulfate polyacrylamide gel electrophoresis of the nitrite reductase (NiR) enzyme identified three prominent bands with molecular weights of 37–41 kDa. A linear correlation existed between incremental denitrification rates and incremental activity of the NiR enzyme. The NiR enzyme activity was enhanced by the supplementary carbon sources, thereby increasing the nitrite denitrification rate. The capacity of supplementary carbon source on enhancing NiR enzyme activity follows: methanol?>?acetate?>?ethanol on molar basis or acetate?>?ethanol?>?methanol on an added weight basis. 相似文献
6.
Effects of nitrate concentration on the denitrification potential of a calcic cambisol and its fractions of N2, N2O and NO 总被引:1,自引:0,他引:1
Rui Wang Qi Feng Tingting Liao Xunhua Zheng Klaus Butterbach-Bahl Wei Zhang Chunyi Jin 《Plant and Soil》2013,363(1-2):175-189
Background and aims
The direct measurement of denitrification dynamics and its product fractions is important for parameterizing process-oriented model(s) for nitrogen cycling in various soils. The aims of this study are to a) directly measure the denitrification potential and the fractions of nitrogenous gases as products of the process in laboratory, b) investigate the effects of the nitrate (NO 3 ? ) concentration on emissions of denitrification gases, and c) test the hypothesis that denitrification can be a major pathway of nitrous oxide (N2O) and nitric oxide (NO) production in calcic cambisols under conditions of simultaneously sufficient supplies of carbon and nitrogen substrates and anaerobiosis as to be found to occur commonly in agricultural lands.Methods
Using the helium atmosphere (with or without oxygen) gas-flow-soil-core technique in laboratory, we directly measured the denitrification potential of a silt clay calcic cambisol and the production of nitrogen gas (N2), N2O and NO during denitrification under the conditions of seven levels of NO 3 ? concentrations (ranging from 10 to 250 mg N kg?1 dry soil) and an almost constant initial dissolved organic carbon concentration (300 mg C kg?1 dry soil).Results
Almost all the soil NO 3 ? was consumed during anaerobic incubation, with 80–88 % of the consumed NO 3 ? recovered by measuring nitrogenous gases. The results showed that the increases in initial NO 3 ? concentrations significantly enhanced the denitrification potential and the emissions of N2 and N2O as products of this process. Despite the wide range of initial NO 3 ? concentrations, the ratios of N2, N2O and NO products to denitrification potential showed much narrower ranges of 51–78 % for N2, 14–36 % for N2O and 5–22 % for NO.Conclusions
These results well support the above hypothesis and provide some parameters for simulating effects of variable soil NO 3 ? concentrations on denitrification process as needed for biogeochemical models. 相似文献7.
Long-term elevated atmogenic deposition (~5 g m?2 year?1) of reactive nitrogen (N) causes N saturation in forests of subtropical China which may lead to high nitrous oxide (N2O) emissions. Recently, we found high N2O emission rates (up to 1,730 μg N2O–N m?2 h?1) during summer on well-drained acidic acrisols (pH = 4.0) along a hill slope in the forested Tieshanping catchment, Chongqing, southwest China. Here, we present results from an in situ 15N–NO3 ? labeling experiment to assess the contribution of nitrification and denitrification to N2O emissions in these soils. Two loads of 99 at.% K15NO3 (equivalent to 0.2 and 1.0 g N m?2) were applied as a single dose to replicated plots at two positions along the hill slope (at top and bottom, respectively) during monsoonal summer. During a 6-day period after label application, we found that 71–100 % of the emitted N2O was derived from the labeled NO3 ? pool irrespective of slope position. Based on this, we assume that denitrification is the dominant process of N2O formation in these forest soils. Within 6 days after label addition, the fraction of the added 15N–NO3 ? emitted as 15N–N2O was highest at the low-N addition plots (0.2 g N m?2), amounting to 1.3 % at the top position of the hill slope and to 3.2 % at the bottom position, respectively. Our data illustrate the large potential of acid forest soils in subtropical China to form N2O from excess NO3 ? most likely through denitrification. 相似文献
8.
Heterotrophic nitrification and aerobic denitrification by a novel Halomonas campisalis 总被引:1,自引:0,他引:1
Yan Guo Xuemei Zhou Yuguang Li Ke Li Caixia Wang Jianfei Liu Daojiang Yan Yilan Liu Dehui Yang Jianmin Xing 《Biotechnology letters》2013,35(12):2045-2049
A novel halophilic strain that could carry out heterotrophic nitrification and aerobic denitrification was isolated and named as Halomonas campisalis ha3. It removed inorganic nitrogen compounds (e.g. NO3 ?, NO2 ? and NH4 +) simultaneously, and grew well in the medium containing up to 20 % (w/v) NaCl. PCR revealed four genes in the genome of ha3 related to aerobic denitrification: napA, nirS, norB and nosZ. The optimal conditions for aerobic denitrification were pH 9.0, at 37 °C, with 4 % (w/v) NaCl and sodium succinate as carbon source. The nitrogen removal rate was 87.5 mg NO3 ?–N l?1 h?1. Therefore, this strain is a potential aerobic denitrifier for the treatment of saline wastewater. 相似文献
9.
Julie N. Weitzman Kenneth J. Forshay Jason P. Kaye Paul M. Mayer Jason C. Koval Robert C. Walter 《Biogeochemistry》2014,120(1-3):337-357
Recent identification of the widespread distribution of legacy sediments deposited in historic mill ponds has increased concern regarding their role in controlling land–water nutrient transfers in the mid-Atlantic region of the US. At Big Spring Run in Lancaster, Pennsylvania, legacy sediments now overlay a buried relict hydric soil (a former wetland soil). We compared C and N processing in legacy sediment to upland soils to identify soil zones that may be sources or sinks for N transported toward streams. We hypothesized that legacy sediments would have high nitrification rates (due to recent agricultural N inputs), while relict hydric soils buried beneath the legacy sediments would be N sinks revealed via negative net nitrification and/or positive denitrification (because the buried former wetland soils are C rich but low in O2). Potential net nitrification ranged from 9.2 to 77.9 g m?2 year?1 and potential C mineralization ranged from 223 to 1,737 g m?2 year?1, with the highest rates in surface soils for both legacy sediments and uplands. Potential denitrification ranged from 0.37 to 21.72 g m?2 year?1, with the buried relict hydric soils denitrifying an average of 6.2 g m?2 year?1. Contrary to our hypothesis, relict hydric layers did not have negative potential nitrification or high positive potential denitrification rates, in part because microbial activity was low relative to surface soils, as indicated by low nitrifier population activity, low substrate induced respiration, and low exoenzyme activity. Despite high soil C concentrations, buried relict hydric soils do not provide the ecological services expected from a wetland soil. Thus, legacy sediments may dampen N removal pathways in buried relict hydric soils, while also acting as substantial sources of NO3 ? to waterways. 相似文献
10.
Denitrification and nitrous oxide effluxes in boreal, eutrophic river sediments under increasing nitrate load: a laboratory microcosm study 总被引:1,自引:0,他引:1
Hanna Silvennoinen Anu Liikanen Jouni Torssonen C. Florian Stange Pertti J. Martikainen 《Biogeochemistry》2008,91(2-3):105-116
Intact sediment cores from rivers of the Bothnian Bay (Baltic Sea) were studied for denitrification based on benthic fluxes of molecular nitrogen (N2) and nitrous oxide (N2O) in a temperature controlled continuous water flow laboratory microcosm under 10, 30, 100, and 300 μM of 15N enriched nitrate (NO3 ?, ~98 at. %). Effluxes of both N2 and N2O from sediment to the overlying water increased with increasing NO3 ? load. Although the ratio of N2O to N2 increased with increasing NO3 ? load, it remained below 0.04, N2 always being the main product. At the NO3 ? concentrations most frequently found in the studied river water (10–100 μM), up to 8% of the NO3 ? was removed in denitrification, whereas with the highest concentration (300 μM), the removal by denitrification was less than 2%. However, overall up to 42% of the NO3 ? was removed by mechanisms other than denitrification. As the microbial activity was simultaneously enhanced by the NO3 ? load, shown as increased oxygen consumption and dissolved inorganic carbom efflux, it is likely that a majority of the NO3 ? was assimilated by microbes during their growth. The 15N content in ammonium (NH4 +) in the efflux was low, suggesting that reduction of NO3 ? to NH4 + was not the reason for the NO3 ? removal. This study provides the first published information on denitrification and N2O fluxes and their regulation by NO3 ? load in eutrophic high latitude rivers. 相似文献
11.
Guillaume Vilain Josette Garnier Gaëlle Tallec Julien Tournebize 《Biogeochemistry》2012,111(1-3):253-271
Production and accumulation of nitrous oxide (N2O), a major greenhouse gas, in shallow groundwater might contribute to indirect N2O emissions to the atmosphere (e.g., when groundwater flows into a stream or a river). The Intergovernmental Panel on Climate Change (IPCC) has attributed an emission factor (EF5g) for N2O, associated with nitrate leaching in groundwater and drainage ditches—0.0025 (corresponding to 0.25% of N leached which is emitted as N2O)—although this is the subject of considerable uncertainty. We investigated and quantified the transport and fate of nitrate (NO3 ?) and dissolved nitrous oxide from crop fields to groundwater and surface water over a 2-year period (monitoring from April 2008 to April 2010) in a transect from a plateau to the river with three piezometers. In groundwater, nitrate concentrations ranged from 1.0 to 22.7 mg NO3 ?–N l?1 (from 2.8 to 37.5 mg NO3 ?–N l?1 in the river) and dissolved N2O from 0.2 to 101.0 μg N2O–N l?1 (and from 0.2 to 2.9 μg N2O–N l?1 in the river). From these measurements, we estimated an emission factor of EF5g = 0.0026 (similar to the value currently used by the IPCC) and an annual indirect N2O flux from groundwater of 0.035 kg N2O–N ha?1 year?1, i.e., 1.8% of the previously measured direct N2O flux from agricultural soils. 相似文献
12.
Benthic biogeochemistry and macrofauna were investigated six times over 1 year in a shallow sub-tropical embayment. Benthic fluxes of oxygen (annual mean ?918 μmol O2 m?2 h?1), ammonium (NH4 +), nitrate (NO3 ?), dissolved organic nitrogen, dinitrogen gas (N2), and dissolved inorganic phosphorus were positively related to OM supply (N mineralisation) and inversely related to benthic light (N assimilation). Ammonium (NH4 +), NO3 ? and N2 fluxes (annual means +14.6, +15.9 and 44.6 μmol N m?2 h?1) accounted for 14, 16 and 53 % of the annual benthic N remineralisation respectively. Denitrification was dominated by coupled nitrification–denitrification throughout the study. Potential assimilation of nitrogen by benthic microalgae (BMA) accounted for between 1 and 30 % of remineralised N, and was greatest during winter when bottom light was higher. Macrofauna biomass tended to be highest at intermediate benthic respiration rates (?1,000 μmol O2 m?2 h?1), and appeared to become limited as respiration increased above this point. While bioturbation did not significantly affect net fluxes, macrofauna biomass was correlated with increased light rates of NH4 + flux which may have masked reductions in NH4 + flux associated with BMA assimilation during the light. Peaks in net N2 fluxes at intermediate respiration rates are suggested to be associated with the stimulation of potential denitrification sites due to bioturbation by burrowing macrofauna. NO3 ? fluxes suggest that nitrification was not significantly limited within respiration range measured during this study, however comparisons with other parts of Moreton Bay suggest that limitation of coupled nitrification–denitrification may occur in sub-tropical systems at respiration rates exceeding ?1,500 μmol O2 m?2 h?1. 相似文献
13.
Louis A. Schipper Will D. Robertson Arthur J. Gold Dan B. Jaynes Stewart C. Cameron 《Ecological Engineering》2010,36(11):1532-1543
Low-cost and simple technologies are needed to reduce watershed export of excess nitrogen to sensitive aquatic ecosystems. Denitrifying bioreactors are an approach where solid carbon substrates are added into the flow path of contaminated water. These carbon (C) substrates (often fragmented wood-products) act as a C and energy source to support denitrification; the conversion of nitrate (NO3?) to nitrogen gases. Here, we summarize the different designs of denitrifying bioreactors that use a solid C substrate, their hydrological connections, effectiveness, and factors that limit their performance. The main denitrifying bioreactors are: denitrification walls (intercepting shallow groundwater), denitrifying beds (intercepting concentrated discharges) and denitrifying layers (intercepting soil leachate). Both denitrifcation walls and beds have proven successful in appropriate field settings with NO3? removal rates generally ranging from 0.01 to 3.6 g N m?3 day?1 for walls and 2–22 g N m?3 day?1 for beds, with the lower rates often associated with nitrate-limitations. Nitrate removal is also limited by the rate of C supply from degrading substrate and removal is operationally zero-order with respect to NO3? concentration primarily because the inputs of NO3? into studied bioreactors have been generally high. In bioreactors where NO3? is not fully depleted, removal rates generally increase with increasing temperature. Nitrate removal has been supported for up to 15 years without further maintenance or C supplementation because wood chips degrade sufficiently slowly under anoxic conditions. There have been few field-based comparisons of alternative C substrates to increase NO3? removal rates but laboratory trials suggest that some alternatives could support greater rates of NO3? removal (e.g., corn cobs and wheat straw). Denitrifying bioreactors may have a number of adverse effects, such as production of nitrous oxide and leaching of dissolved organic matter (usually only for the first few months after construction and start-up). The relatively small amount of field data suggests that these problems can be adequately managed or minimized. An initial cost/benefit analysis demonstrates that denitrifying bioreactors are cost effective and complementary to other agricultural management practices aimed at decreasing nitrogen loads to surface waters. We conclude with recommendations for further research to enhance performance of denitrifying bioreactors. 相似文献
14.
Longfei Yu Jan Mulder Jing Zhu Xiaoshan Zhang Zhangwei Wang Peter Drsch 《Global Change Biology》2019,25(5):1765-1778
Increasing nitrogen (N) deposition in subtropical forests in south China causes N saturation, associated with significant nitrate (NO3?) leaching. Strong N attenuation may occur in groundwater discharge zones hydrologically connected to well‐drained hillslopes, as has been shown for the subtropical headwater catchment “TieShanPing”, where dual NO3? isotopes indicated that groundwater discharge zones act as an important N sink and hotspot for denitrification. Here, we present a regional study reporting inorganic N fluxes over two years together with dual NO3? isotope signatures obtained in two summer campaigns from seven forested catchments in China, representing a gradient in climate and atmospheric N input. In all catchments, fluxes of dissolved inorganic N indicated efficient conversion of NH4+ to NO3? on well‐drained hillslopes, and subsequent interflow of NO3? over the argic B‐horizons to groundwater discharge zones. Depletion of 15N‐ and 18O–NO3? on hillslopes suggested nitrification as the main source of NO3?. In all catchments, except one of the northern sites, which had low N deposition rates, NO3? attenuation by denitrification occurred in groundwater discharge zones, as indicated by simultaneous 15N and 18O enrichment in residual NO3?. By contrast to the southern sites, the northern catchments lack continuous and well‐developed groundwater discharge zones, explaining less efficient N removal. Using a model based on 15NO3? signatures, we estimated denitrification fluxes from 2.4 to 21.7 kg N ha?1 year?1 for the southern sites, accounting for more than half of the observed N removal. Across the southern catchments, estimated denitrification scaled proportionally with N deposition. Together, this indicates that N removal by denitrification is an important component of the N budget of southern Chinese forests and that natural NO3? attenuation may increase with increasing N input, thus partly counteracting further aggravation of N contamination of surface waters in the region. 相似文献
15.
Kottekkatu Padinchati Krishnan Rupesh Kumar Sinha Sivaramakrishnan Rajan 《Annals of microbiology》2014,64(1):365-376
This study addresses factors governing nitrification and denitrification rates, along with the abundance of the bacterial groups likely involved in these activities, in Kongsfjorden, an Arctic fjord at Ny-Ålesund, Svalbard. The fjord was sampled three times during the month of March 2008 as day length and direct solar radiation increased. Although initially well mixed, cooler and more saline, the fjord became stratified, warmer and less saline during late March. The concentrations of NH4 + (4.4?±?1.6 to 6?±?1.6 μM) and NO2 ? (1?±?0.3 to 1.2?±?0.4 μM) increased progressively with the decrease in NO3 ? (6.1?±?1.3 to 3.8?±?1.5 μM), reflecting the onset of primary productivity. Nitrification rates and the culturable population of nitrifiers decreased significantly from 1.6?±?0.9 to 0.4?±?0.1 ng at NH4 +-N l?1 h?1 and 5.1?±?0.3?×?102 to 29?±?14 cells l?1, respectively. In contrast, denitrification rates increased (2.4?±?0.5 to 4.6?±?1.3 ng-at NO3 ?-N l?1 h?1), although the abundance of culturable denitrifiers did not vary significantly. A significant correlation of nitrifiers with NO3 ? during early March (p?<?0.01, r?=?0.51) indicated that nitrifiers may play an important role in regulating the NO3 ? pool and thereby in controlling the abundance of denitrifiers. However, the contribution of nitrification to the total NO3 ? pool decreased with time. Experimental simulations were also set up to understand the impact of change in duration of light and progressive increase in temperature on these processes. The application of 24 h light inhibited nitrification, suggesting that during peak Arctic summer the contribution of nitrification to the nitrate pool is minimal. It was also observed that a brief exposure to light (≤6 h) was enough to hamper nitrification rates. Experimental simulations suggested that a gradual increase in temperature in the fjord may enhance the magnitude of nitrification and denitrification in the fjord. 相似文献
16.
Microorganism with simultaneous nitrification and denitrification ability plays a significant role in nitrogen removal process, especially in the eutrophic waters with excessive nitrogen loads. The nitrogen removal capacity of microorganism may suffer from low temperature or nitrite nitrogen source. In this study, a hypothermia aerobic nitrite-denitrifying bacterium, Pseudomonas tolaasii strain Y-11, was selected to determine the simultaneous nitrification and denitrification ability with mixed nitrogen source at 15 °C. The sole nitrogen removal efficiencies of strain Y-11 in simulated wastewater were obtained. After 24 h of incubation at 15 °C, the ammonium nitrogen fell below the detection limit from an initial value of 10.99 mg/L. Approximately 88.0 ± 0.33% of nitrate nitrogen was removed with the initial concentration of 11.78 mg/L and the nitrite nitrogen was not detected with the initial concentration of 10.75 mg/L after 48 h of incubation at 15 °C. Additionally, the simultaneous nitrification and denitrification nitrogen removal ability of P. tolaasii strain Y-11 was evaluated using low concentration of mixed NH4+-N and NO3?–N/NO2?–N (about 5 mg/L-N each) and high concentration of mixed NH4+–N and NO3?–N/NO2?–N (about 100 mg/L-N each). There was no nitrite nitrogen accumulation at the time of evaluation. The results demonstrated that P. tolaasii strain Y-11 had higher simultaneous nitrification and denitrification capacity with low concentration of mixed inorganic nitrogen sources and may be applied in low temperature wastewater treatment. 相似文献
17.
Richard L. Smith John Karl Böhlke Deborah A. Repert Charles P. Hart 《Biogeochemistry》2009,96(1-3):189-208
The extent to which in-stream processes alter or remove nutrient loads in agriculturally impacted streams is critically important to watershed function and the delivery of those loads to coastal waters. In this study, patch-scale rates of in-stream benthic processes were determined using large volume, open-bottom benthic incubation chambers in a nitrate-rich, first to third order stream draining an area dominated by tile-drained row-crop fields. The chambers were fitted with sampling/mixing ports, a volume compensation bladder, and porewater samplers. Incubations were conducted with added tracers (NaBr and either 15N[NO3 ?], 15N[NO2 ?], or 15N[NH4 +]) for 24–44 h intervals and reaction rates were determined from changes in concentrations and isotopic compositions of nitrate, nitrite, ammonium and nitrogen gas. Overall, nitrate loss rates (220–3,560 μmol N m?2 h?1) greatly exceeded corresponding denitrification rates (34–212 μmol N m?2 h?1) and both of these rates were correlated with nitrate concentrations (90–1,330 μM), which could be readily manipulated with addition experiments. Chamber estimates closely matched whole-stream rates of denitrification and nitrate loss using 15N. Chamber incubations with acetylene indicated that coupled nitrification/denitrification was not a major source of N2 production at ambient nitrate concentrations (175 μM), but acetylene was not effective for assessing denitrification at higher nitrate concentrations (1,330 μM). Ammonium uptake rates greatly exceeded nitrification rates, which were relatively low even with added ammonium (3.5 μmol N m?2 h?1), though incubations with nitrite demonstrated that oxidation to nitrate exceeded reduction to nitrogen gas in the surface sediments by fivefold to tenfold. The chamber results confirmed earlier studies that denitrification was a substantial nitrate sink in this stream, but they also indicated that dissolved inorganic nitrogen (DIN) turnover rates greatly exceeded the rates of permanent nitrogen removal via denitrification. 相似文献
18.
Knowledge of the fate of deposited N in the possibly N-limited, highly biodiverse north Andean forests is important because of the possible effects of N inputs on plant performance and species composition. We analyzed concentrations and fluxes of NO3 ??CN, NH4 +?CN and dissolved organic N (DON) in rainfall, throughfall, litter leachate, mineral soil solutions (0.15?C0.30 m depths) and stream water in a montane forest in Ecuador during four consecutive quarters and used the natural 15N abundance in NO3 ? during the passage of rain water through the ecosystem and bulk ??15N values in soil to detect N transformations. Depletion of 15N in NO3 ? and increased NO3 ??CN fluxes during the passage through the canopy and the organic layer indicated nitrification in these compartments. During leaching from the organic layer to mineral soil and stream, NO3 ? concentrations progressively decreased and were enriched in 15N but did not reach the ??15N values of solid phase organic matter (??15N = 5.6?C6.7??). This suggested a combination of nitrification and denitrification in mineral soil. In the wettest quarter, the ??15N value of NO3 ? in litter leachate was smaller (??15N = ?1.58??) than in the other quarters (??15N = ?9.38 ± SE 0.46??) probably because of reduced mineralization and associated fractionation against 15N. Nitrogen isotope fractionation of NO3 ? between litter leachate and stream water was smaller in the wettest period than in the other periods probably because of a higher rate of denitrification and continuous dilution by isotopically lighter NO3 ??CN from throughfall and nitrification in the organic layer during the wettest period. The stable N isotope composition of NO3 ? gave valuable indications of N transformations during the passage of water through the forest ecosystem from rainfall to the stream. 相似文献
19.
Myrto Tsiknia Vasileios A. Tzanakakis Dimitris Oikonomidis Nikolaos V. Paranychianakis Nikolaos P. Nikolaidis 《Applied microbiology and biotechnology》2014,98(6):2739-2749
This study investigated the cycling of C and N following application of olive mill wastewater (OMW) at various rates (0, 42, 84, and 168 m3/ha). OMW stimulated respiration rate throughout the study period, but an increase in soil organic matter was observed only at the highest rate. Soil phenol content decreased rapidly within 2 weeks following application but neither phenol oxidase and peroxidase activity nor laccase gene copies could explain this response. Soil NH4 +-N content increased in response to OMW application rate, while an opposite trend observed for NO3 ?-N, which attributed to immobilization. This decrease was in accordance with amoA gene copies of archaeal and bacterial ammonia oxidizers in the first days following OMW application. Afterwards, although amoA gene copies and potential nitrification rates recovered to values similar to or higher than those in the non-treated soils, NO3 ?-N content did not change among the treatments. A corresponding increase in denitrifying gene copies (nirK, nirS, nosZ) during that period indicates that denitrification, stimulated by OMW application rate, was responsible for this effect; a hypothesis consistent with the decrease in total Kjeldahl nitrogen content late in the season. The findings suggest that land application of OMW is a promising practice for OMW management, even at rates approaching the soil water holding capacity. 相似文献
20.
Robert S. Stelzer Damion R. Drover Susan L. Eggert Maureen A. Muldoon 《Biogeochemistry》2011,103(1-3):91-107
We measured net nitrate retention by mass balance in a 700-m upwelling reach of a third-order sand plains stream, Emmons Creek, from January 2007 to November 2008. Surface water and groundwater fluxes of nitrate were determined from continuous records of discharge and from nitrate concentrations based on weekly and biweekly sampling at three surface water stations and in 23 in-stream piezometers, respectively. Surface water nitrate concentration in Emmons Creek was relatively high (mean of 2.25 mg NO3?CN l?1) and exhibited strong seasonal variation. Net nitrate retention averaged 429 mg NO3?CN m?2 d?1 and about 2% of nitrate inputs to the reach. Net nitrate retention was highest during the spring and autumn when groundwater discharge was elevated. Groundwater discharge explained 57?C65% of the variation in areal net nitrate retention. Specific discharge and groundwater nitrate concentration varied spatially. Weighting groundwater solute concentrations by specific discharge improved the water balance and resulted in higher estimates of nitrate retention. Our results suggest that groundwater inputs of nitrate can drive nitrate retention in streams with high groundwater discharge. 相似文献