首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
A thermotolerant bacterium, identified as Bacillus licheniformis, completely utilized 0.1% (w/v) NH4NO3 at 30 and 50°C under aerobic condition. The addition of 0.5 mM Fe2+ to the NH4NO3 medium markedly promoted the utilization of NH4+ and NO3. At 50°C, of total nitrogen originally provided, 24% was taken up into the cells and 20% remained in the culture supernatant. Residual nitrogen (56%) was probably removed into the atmosphere. The cell extracts contained enzymes involved in denitrification. GC-MS demonstrated that NH4 15NO3 had been converted to 15N2O. These results indicate that the strain has denitrification ability under aerobic condition.  相似文献   

2.
Nitrogen cycling in Louisiana Gulf Coast brackish marshes   总被引:1,自引:0,他引:1  
Nitrogen fixation and nitrogen accumulation were measured in a Louisiana Spartina patens brackish marsh. Using the acetylene reduction technique calibrated with direct 15N2 assimilation, an equivalent of 90.0 µ g N g–1 yr–1 was fixed. Fixation was greater in the summer months and in the upper portion of the soil profile. Extractable ammonium increased with depth and was negatively correlated with ethylene production. Average ammonium concentration in the sediment was 39 µg NH4 +-N g–1 sediment. Cesium-137 dating of the soil profile showed the marsh was vertically accreting at a rate of 0.60 cm yr–1. Calculations using vertical accretion rate, bulk density, and total nitrogen content of sediment indicate that the marshes are accumumating 7.2 g Nm–2 yr–1 thus serving as a major nitrogen sink. Measured nitrogen fluxes were incorporated with existing flux measurement in developing a nitrogen budget for the marsh.  相似文献   

3.
Providencia rettgeri strain YL was found to be efficient in heterotrophic nitrogen removal under aerobic conditions. Maximum removal of NH4 +–N occurred under the conditions of pH 7 and supplemented with glucose as the carbon source. Inorganic ions such as Mg2+, Mn2+, and Zn2+ largely influenced the growth and nitrogen removal efficiency. A quantitative detection of nitrogen gas by gas chromatography was conducted to evaluate the nitrogen removal by strain YL. From the nitrogen balance during heterotrophic growth with 180 mg/l of NH4 +–N, 44.5% of NH4 +–N was in the form of N2 and 49.7% was found in biomass, with only a trace amount of either nitrite or nitrate. The utilization of nitrite and nitrate during the ammonium removal process demonstrated that the nitrogen removal pathway by strain YL was heterotrophic nitrification-aerobic denitrification. A further enzyme assay of nitrate reductase and nitrite reductase activity under the aerobic condition confirmed this nitrogen removal pathway.  相似文献   

4.
Heterotrophic carbon utilizing microbes were acclimatized in the laboratory by inoculating sludge collected from the waste discharge pond of a small-scale rural abattoir in India in a nutrient solution intermittently fed with glucose and ammonium chloride. Cultures of 10 well-developed isolates were selected and grown in a basal medium containing glucose and ammonium chloride. Culture supernatants were periodically analyzed for ammonium nitrogen (NH4 +-N) and chemical oxygen demand (COD). Polyphasic taxonomic study of the most active nitrifier (S18) was done. Half saturation concentration (K s), maximum rate of substrate utilization (k), yield coefficient (Y) and decay coefficient (K d) were determined from the Lineweaver–Burk plot using the modified Monod equation. S18 was able to remove 97 ± 2% of (NH4 +-N) and 88 ± 3% of COD. Molecular phylogenetic study supported by physiological and biochemical characteristics assigned S18 as Achromobacter xylosoxidans. Nitrification activity of A. xylosoxidans was demonstrated for the first time, while interestingly, the distinctive anaerobic denitrification property was preserved in S18. K s values were determined as 232.13 ± 1.5 mg/l for COD reduction and 2.131 ± 1.9 mg/l for NH4 +-N utilization. Yield coefficients obtained were 0.4423 ± 0.1134 mg of MLVSS/mg of COD and 0.2461 ± 0.0793 mg of MLVSS/mg of NH4 +-N while the decay coefficients were 0.0627 ± 0.0013 per day and 0.0514 ± 0.0008 per day, respectively. After a contact period of 24 h, 650 ± 5 mg/l solids were produced when the initial concentration of COD and NH4 +-N were 1820 ± 10 mg/l and 120 ± 5.5 mg/l, respectively. This is the first report on the kinetic coefficients for carbon oxidation and nitrification by a single bacterium isolated from slaughterhouse wastewater.  相似文献   

5.
The present lab-scale research reveals the potential of implementation of an oxygen-limited autotrophic nitrification-denitrification (OLAND) system with normal nitrifying sludge as the biocatalyst for the removal of nitrogen from nitrogen-rich wastewater in one step. In a sequential batch reactor, synthetic wastewater containing 1 g of NH4+-N liter−1 and minerals was treated. Oxygen supply to the reactor was double-controlled with a pH controller and a timer. At a volumetric loading rate (Bv) of 0.13 g of NH4+-N liter−1 day−1, about 22% of the fed NH4+-N was converted to NO2-N or NO3-N, 38% remained as NH4+-N, and the other 40% was removed mainly as N2. The specific removal rate of nitrogen was on the order of 50 mg of N liter−1 day−1, corresponding to 16 mg of N g of volatile suspended solids−1 day−1. The microorganisms which catalyzed the OLAND process are assumed to be normal nitrifiers dominated by ammonium oxidizers. The loss of nitrogen in the OLAND system is presumed to occur via the oxidation of NH4+ to N2 with NO2 as the electron acceptor. Hydroxylamine stimulated the removal of NH4+ and NO2. Hydroxylamine oxidoreductase (HAO) or an HAO-related enzyme might be responsible for the loss of nitrogen.  相似文献   

6.
Nitrification and denitrification were studied in a millimeterscale microenvironment using a two-phase system with a liquid manure-saturated layer. Samples consisted of liquid cattle manure and air-dried soil stabilized with silica gel, placed between two aerobic soil phases with a water content near field capacity. A high potential for NH4 + oxidation developed within 0–2 mm distance from the interface, and NH4 + diffused only 10–20 mm into the soil. Some NH4 + was probably immobilized by microorganisms in the soil between 0 and 4 days, after which nitrification was the only sink for NH4 +. A potential for denitrification developed within the manure-saturated zone. Maximum rates of both potential and actual denitrification were recorded by Day 4, but denitrification continued for at least 2–3 weeks. The potential for nitrification peaked after 14 days. When the pH of the manure was adjusted to 5.5, nitrification was reduced close to the interface, and NH4 + penetrated further into the soil before it was oxidized. The pH adjustment had an inhibitory effect on denitrification: Both potential and actual rates of denitrification were almost eliminated for several days. The size of the manure-saturated layer strongly affected denitrification losses. With layers of 8 and 16 mm thickness, losses equivalent to 33 and 40% of the original NH4 + pool, respectively, were estimated. When manure corresponding to a 12 mm layer was homogeneously mixed with the soil, only 0.3% was lost.Offprint requests to: S. O. Petersen.  相似文献   

7.
Zhang J  Wu P  Hao B  Yu Z 《Bioresource technology》2011,102(21):9866-9869
A strain YZN-001 was isolated from swine manure effluent and was identified as Pseudomonas stutzeri. It can utilise not only nitrate and nitrite, but also ammonium. The strain had the capability to fully remove as much as 275.08 mg L−1 NO3–N and 171.40 mg L−1 NO2–N under aerobic conditions. Furthermore, At 30 °C, the utilization of ammonium is approximately 95% by 18 h with a similar level removed by 72 h and 2 weeks at 10 and 4 °C, respectively. Triplicate sets of tightly sealed serum bottles were used to test the heterotrophic nitrifying ability of P. stutzeri YZN-001. The results showing that 39% of removed NH4+–N was completely oxidised to nitrogen gas by 18 h. Indicating that the strain has heterotrophic nitrification and aerobic denitrification abilities, with the notable ability to remove ammonium at low temperatures, demonstrating a potential using the strain for future application in waste water treatment.  相似文献   

8.
In short-term water culture experiments with different 15N labeled ammonium or nitrate concentrations, citrus seedlings absorbed NH4 + at a higher rate than NO3 . Maximum NO3 uptake by the whole plant occurred at 120 mg L–1 NO3 -N, whereas NH4 + absorption was saturated at 240 mg L–1 NH4 +-N. 15NH4 + accumulated in roots and to a lesser degree in both leaves and stems. However, 15NO3 was mostly partitioned between leaves and roots.Adding increasing amounts of unlabeled NH4 + (15–60 mg L–1 N) to nutrient solutions containing 120 mg L–1 N as 15N labeled nitrate reduced 15NO3 uptake. Maximum inhibition of 15NO3 uptake was about 55% at 2.14 mM NH4 + (30 mg L–1 NH4 +-N) and it did not increase any further at higher NH4 + proportions.In a long-term experiment, the effects of concentration and source of added N (NO3 or NH4 +) on nutrient concentrations in leaves from plants grown in sand were evaluated. Leaf concentration of N, P, Mg, Fe and Cu were increased by NH4 + versus NO3 nutrition, whereas the reverse was true for Ca, K, Zn and Mn.The effects of different NO3 -N:NH4 +-N ratios (100:0, 75:25, 50:50, 25:75 and 0:100) at 120 mg L–1 total N on leaf nutrient concentrations, fruit yield and fruit characteristics were investigated in another long-term experiment with plants grown in sand cultures. Nitrogen concentrations in leaves were highest when plants were provided with either NO3 or NH4 + as a sole source of N. Lowest N concentration in leaves was found with a 75:25 NO3 -N/NH4 +-N ratio. With increasing proportions of NH4 + in the N supply, leaf nutrients such as P, Mg, Fe and Cu increased, whereas Ca, K, Mn and Zn decreased. Yield in number of fruits per tree was increased significantly by supplying all N as NH4 +, although fruit weight was reduced. The number of fruits per tree was lowest with the 75:25 NO3 -N:NH4 +-N ratio, but in this treatment fruits reached their highest weight. Rind thickness, juice acidity, and colour index of fruits decreased with increasing NH4 + in the N supply, whereas the % pulp and maturity index increased. Percent of juice in fruits and total soluble solids were only slightly affected by NO3 :NH4 + ratio.  相似文献   

9.
To date, few studies are conducted to quantify the effects of reduced ammonium (NH4 +) and oxidized nitrate (NO3 ) on soil CH4 uptake and N2O emission in the subtropical forests. In this study, NH4Cl and NaNO3 fertilizers were applied at three rates: 0, 40 and 120 kg N ha−1 yr−1. Soil CH4 and N2O fluxes were determined twice a week using the static chamber technique and gas chromatography. Soil temperature and moisture were simultaneously measured. Soil dissolved N concentration in 0–20 cm depth was measured weekly to examine the regulation to soil CH4 and N2O fluxes. Our results showed that one year of N addition did not affect soil temperature, soil moisture, soil total dissolved N (TDN) and NH4 +-N concentrations, but high levels of applied NH4Cl and NaNO3 fertilizers significantly increased soil NO3 -N concentration by 124% and 157%, respectively. Nitrogen addition tended to inhibit soil CH4 uptake, but significantly promoted soil N2O emission by 403% to 762%. Furthermore, NH4 +-N fertilizer application had a stronger inhibition to soil CH4 uptake and a stronger promotion to soil N2O emission than NO3 -N application. Also, both soil CH4 and N2O fluxes were driven by soil temperature and moisture, but soil inorganic N availability was a key integrator of soil CH4 uptake and N2O emission. These results suggest that the subtropical plantation soil sensitively responses to atmospheric N deposition, and inorganic N rather than organic N is the regulator to soil CH4 uptake and N2O emission.  相似文献   

10.
Aerobic and anaerobic groundwater continuous-flow microcosms were designed to study nitrate reduction by the indigenous bacteria in intact saturated soil cores from a sandy aquifer with a concentration of 3.8 mg of NO3-N liter−1. Traces of 15NO3 were added to filter-sterilized groundwater by using a Darcy flux of 4 cm day−1. Both assimilatory and dissimilatory reduction rates were estimated from analyses of 15N2, 15N2O, 15NH4+, and 15N-labeled protein amino acids by capillary gas chromatography-mass spectrometry. N2 and N2O were separated on a megabore fused-silica column and quantified by electron impact-selected ion monitoring. NO3 and NH4+ were analyzed as pentafluorobenzoyl amides by multiple-ion monitoring and protein amino acids as their N-heptafluorobutyryl isobutyl ester derivatives by negative ion-chemical ionization. The numbers of bacteria and their [methyl-3H]thymidine incorporation rates were simultaneously measured. Nitrate was completely reduced in the microcosms at a rate of about 250 ng g−1 day−1. Of this nitrate, 80 to 90% was converted by aerobic denitrification to N2, whereas only 35% was denitrified in the anaerobic microcosm, where more than 50% of NO3 was reduced to NH4+. Assimilatory reduction was recorded only in the aerobic microcosm, where N appeared in alanine in the cells. The nitrate reduction rates estimated for the aquifer material were low in comparison with rates in eutrophic lakes and coastal sediments but sufficiently high to remove nitrate from an uncontaminated aquifer of the kind examined in less than 1 month.  相似文献   

11.
Methane (CH4) and nitrous oxide (N2O) dynamics were studied in a boreal Sphagnum fuscum pine bog receiving annually (from 1991 to 1996) 30 or 100 kg NH4NO3-N ha–1. The gas emissions were measured during the last three growing seasons of the experiment. Nitrogen treatment did not affect the CH4 fluxes in the microsites where S. fuscum and S. angustifolium dominated. However, addition of 100 kg NH4NO3-N ha–1 yr–1 increased the CH4 emission from those microsites dominated by S. fuscum. This increase was associated with the increase in coverage of cotton grass (Eriophorum vaginatum) induced by the nitrogen treatment. The differences in the CH4 emissions were not related to the CH4 oxidation and production potentials in the peat profiles. The N2O fluxes were negligible from all microsites. Only minor short-term increases occurred after the nitrogen addition.  相似文献   

12.
A laboratory scale upflow biological aerated filter (BAF) packed with a porous expanded polyurethane medium was developed to nitrify ammonium to nitrite selectively. Greater than 95% removal of ammonium was achieved up to 2 kg NH4 +-N m–3 d. NO2 -N was accumulated up to 60% of the total (NO2 + NO3 )-N when oxygen was limited.  相似文献   

13.
汪庆兵  张建锋  陈光才  孙慧  吴灏  张颖  杨泉泉  王丽 《生态学报》2015,35(16):5364-5373
采用水培法,研究了旱柳苗在外源添加不同氮水平(贫氮、中氮、富氮、过氮)的铵态氮(NH+4-N)和硝态氮(NO-3-N)的生长、氮吸收、分配和生理响应。结果表明:一定范围氮浓度的增加能够促进旱柳苗的生长,但过量氮会抑制其生长,且NH+4-N的抑制作用大于NO-3-N;两种氮处理下,旱柳表现出对NH+4-N的吸收偏好,在同一氮水平时,旱柳各部位氮原子百分含量Atom%15N(AT%)、15N吸收量和来自氮源的N%(Ndff%)均为NH+4-N处理大于NO-3-N处理,且随着氮浓度的增加,差异增大,且在旱柳各部位的分布为根﹥茎﹥叶;2种氮素过量和不足均会对旱柳根和叶生理指标产生不同的影响,其中在过氮水平时,NH+4-N和NO-3-N处理下根系活力比对照减少了50.61%和增加了19.53%;在过氮水平时,NH+4-N处理柳树苗根总长、根表面积、根平均直径、根体积和侧根数分别对照下降了30.92%、29.48%、19.44%、27.01%和36.41%,NO-3-N处理柳树苗相应的根系形态指标分别对对照下降了1.66%、5.65%、1.49%、5.06%和25.72%。可见,高浓度NH+4-N对旱柳苗的胁迫影响大于NO-3-N,在应用于水体氮污染修复时可通过改变水体无机氮的比例,削弱其对旱柳的影响,从而提高旱柳对水体氮污染的修复效果。  相似文献   

14.
When the alkalinity/NH4 +ratio increased from 4.1 to 9.4, the ammonium removal rate increased from 45 to 90 mg NOx-N l–1 h–1. An increase in alkalinity/NH4 +ratio was a major reason for higher pH and free ammonia (FA) concentration in the reactor. The high concentration of FA showed a selective inhibition for Nitrobacter, which caused enhanced nitrite build-up in a biofilm reactor.  相似文献   

15.
To investigate the role of ammonium-assimilating enzyme in heterocyst differentiation, pattern formation and nitrogen fixation, MSX-resistant and GS-impaired mutants of Anabaena 7120 were isolated using transposon (Tn5-1063) mutagenesis. Mutant Gs1 and Gs2 (impaired in GS activity) exhibited a similar rate of nitrogenase activity compared to that of the wild type under dinitrogen aerobic conditions in the presence and absence of MSX. Filaments of Gs1 and Gs2 produced heterocysts with an evenly spaced pattern in N2-grown conditions, while addition of MSX altered the interheterocyst spacing pattern in wild type as well as in mutant strains. The wild type showed complete repression of heterocyst development and nitrogen fixation in the presence of NO3 or NH4 +, whereas the mutants Gs1 and Gs2 formed heterocysts and fixed nitrogen in the presence of NO3 and NH4 +. Addition of MSX caused complete inhibition of glutamine synthetase activity in wild type but Gs1 and Gs2 remained unaffected. These results suggest that glutamine but not ammonium is directly involved in regulation of heterocyst differentiation, interheterocyst spacing pattern and nitrogen fixation in Anabaena.  相似文献   

16.
Biochar produced by pyrolysis of biomass can be used to counter nitrogen (N) pollution. The present study investigated the effects of feedstock and temperature on characteristics of biochars and their adsorption ability for ammonium N (NH4 +-N) and nitrate N (NO3 -N). Twelve biochars were produced from wheat-straw (W-BC), corn-straw (C-BC) and peanut-shell (P-BC) at pyrolysis temperatures of 400, 500, 600 and 700°C. Biochar physical and chemical properties were determined and the biochars were used for N sorption experiments. The results showed that biochar yield and contents of N, hydrogen and oxygen decreased as pyrolysis temperature increased from 400°C to 700°C, whereas contents of ash, pH and carbon increased with greater pyrolysis temperature. All biochars could sorb substantial amounts of NH4 +-N, and the sorption characteristics were well fitted to the Freundlich isotherm model. The ability of biochars to adsorb NH4 +-N followed: C-BC>P-BC>W-BC, and the adsorption amount decreased with higher pyrolysis temperature. The ability of C-BC to sorb NH4 +-N was the highest because it had the largest cation exchange capacity (CEC) among all biochars (e.g., C-BC400 with a CEC of 38.3 cmol kg−1 adsorbed 2.3 mg NH4 +-N g−1 in solutions with 50 mg NH4 + L−1). Compared with NH4 +-N, none of NO3 -N was adsorbed to biochars at different NO3 concentrations. Instead, some NO3 -N was even released from the biochar materials. We conclude that biochars can be used under conditions where NH4 +-N (or NH3) pollution is a concern, but further research is needed in terms of applying biochars to reduce NO3 -N pollution.  相似文献   

17.
18.
Moawad  H.  Badr El-Din  S. M. S.  Khalafallah  M. A. 《Plant and Soil》1988,112(1):137-141
The nitrogen contribution from the shoot and root system of symbiotically grown leucaena was evaluated in a field experiment on an Alfisol at IITA in Southern Nigeria. Maize in plots that received prunings from inoculated leucaena contained more N and grain yield was increased by 1.9 t.ha.–1. Large quantities of nitrogen were harvested with leucaena prunings (300 kg N ha–1 in six months) but the efficiency of utilization of this nitrogen by maize was low compared to inorganic N fertilizer (ammonium sulphate) at 80 kg N ha–1. Maize yield data indicated that nitrogen in leucaena prunigs was 34 and 45% as efficient as 80 kg N ha–1 of (NH4)2SO4 for uninoculated and inoculated plants with Rhizobium IRc 1045, respectively. In plots where the prunings were removed, the leaf litter and decaying roots and nodules contributed N equivalent of 32 kg ha–1. Twenty-five kg ha–1 was the inorganic N equivalent from nitrogen fixed symbiotically by leucaena when inoculated with Rhizobium strain IRc 1045. Application of prunings from inoculated leucaena resulted in higher soil ogranic C, total N, pH and available NO3.  相似文献   

19.
Enhanced nitrogen (N) availability is one of the main drivers of biodiversity loss and degradation of ecosystem functions. However, in very nutrient-poor ecosystems, enhanced N input can, in the short-term, promote diversity. Mediterranean Basin ecosystems are nutrient-limited biodiversity hotspots, but no information is available on their medium- or long-term responses to enhanced N input. Since 2007, we have been manipulating the form and dose of available N in a Mediterranean Basin maquis in south-western Europe that has low ambient N deposition (<4 kg N ha−1 yr−1) and low soil N content (0.1%). N availability was modified by the addition of 40 kg N ha−1 yr−1 as a 1∶1 NH4Cl to (NH4)2SO4 mixture, and 40 and 80 kg N ha−1 yr−1 as NH4NO3. Over the following 5 years, the impacts on plant composition and diversity (richness and evenness) and some ecosystem characteristics (soil extractable N and organic matter, aboveground biomass and % of bare soil) were assessed. Plant species richness increased with enhanced N input and was more related to ammonium than to nitrate. Exposure to 40 kg NH4 +-N ha−1 yr−1 (alone and with nitrate) enhanced plant richness, but did not increase aboveground biomass; soil extractable N even increased under 80 kg NH4NO3-N ha−1 yr−1 and the % of bare soil increased under 40 kg NH4 +-N ha−1 yr−1. The treatment containing less ammonium, 40 kg NH4NO3-N ha−1 yr−1, did not enhance plant diversity but promoted aboveground biomass and reduced the % of bare soil. Data suggest that enhanced NHy availability affects the structure of the maquis, which may promote soil erosion and N leakage, whereas enhanced NOx availability leads to biomass accumulation which may increase the fire risk. These observations are relevant for land use management in biodiverse and fragmented ecosystems such as the maquis, especially in conservation areas.  相似文献   

20.
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   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号