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1.
Nitrification and denitrification response to varying periods of desiccation and inundation in a western Kansas stream 总被引:3,自引:0,他引:3
Changing environmental conditions and increased water consumption have transformed many historically perennial stream systems
into intermittent systems. Multiple drying and wetting events throughout the year might impact many stream processes including
nitrification and denitrification, key components of the nitrogen (N) cycle. During summer 2007, an experimental stream was
used to dry and then rewet stream sediments to determine the effects of desiccation and rewetting of stream sediment on nitrification
and denitrification potentials. Mean (±SE) nitrification and denitrification rates in sediment not dried (controls) were 0.431 ± 0.017 μg
NO3
−–N/cm2/h and 0.016 ± 0.002 μg N2O–N/cm2/h, respectively. As sediment samples dried, nitrification rates decreased. Rates in sediments dried less than 7 d recovered
to levels equal or greater than those in the controls within 1 d of being rewetted. Denitrification rates were not affected
by 1 d of drying, but samples dried greater than 1 d experienced reduced rates of denitrification. Denitrification in sediments
dried 7 d or less recovered by day seven of being rewetted. Nitrification and denitrification processes failed to fully recover
in sediments dried more than 7 d. These results demonstrate that alterations in stream’s hydrology can significantly affect
N-cycle processes. 相似文献
2.
OLAND is feasible to treat sewage-like nitrogen concentrations at low hydraulic residence times 总被引:6,自引:0,他引:6
De Clippeleir H Yan X Verstraete W Vlaeminck SE 《Applied microbiology and biotechnology》2011,90(4):1537-1545
Energy-positive sewage treatment can, in principle, be obtained by maximizing energy recovery from concentrated organics and
by minimizing energy consumption for concentration and residual nitrogen removal in the main stream. To test the feasibility
of the latter, sewage-like nitrogen influent concentrations were treated with oxygen-limited autotrophic nitrification/denitrification
(OLAND) in a lab-scale rotating biological contactor at 25°C. At influent ammonium concentrations of 66 and 29 mg N L−1 and a volumetric loading rate of 840 mg N L−1 day−1 yielding hydraulic residence times (HRT) of 2.0 and 1.0 h, respectively, relatively high nitrogen removal rates of 444 and
383 mg N L−1 day−1 were obtained, respectively. At low nitrogen levels, adapted nitritation and anammox communities were established. The decrease
in nitrogen removal was due to decreased anammox and increased nitratation, with Nitrospira representing 6% of the biofilm. The latter likely occurred given the absence of dissolved oxygen (DO) control, since decreasing
the DO concentration from 1.4 to 1.2 mg O2 L−1 decreased nitratation by 35% and increased anammox by 32%. Provided a sufficient suppression of nitratation, this study showed
the feasibility of OLAND to treat low nitrogen levels at low HRT, a prerequisite to energy-positive sewage treatment. 相似文献
3.
To clarify the relationship between denitrification activity and dry–wet levels in the littoral wetland sediments of Lake
Biwa, Japan, denitrification rates and their regulating parameters (degree of dryness, redox potential, nitrate concentration)
were measured on different moisture sediments. Redox potential in sediments was higher in the exposed region in contact with
atmosphere than the flooded region covered with water. The nitrate concentration in interstitial waters was undetectable in
the flooded region. On the other hand, concentration in the exposed region increased with increase in the degree of sediment
dryness. The denitrification rate ranged from <0.001 to 0.88 μg N cm−3 h−1 in the exposed region and increased with the increase in the degree of dryness. In the flooded region, on the other hand,
no detectable rate (<0.001 μg N cm−3 h−1) was observed. This indicates that the rates in the exposed region were mainly influenced by nitrate concentration in the
interstitial waters accumulated by desiccation of sediments, whereas rates in the flooded region were strongly limited by
no accumulation of nitrate in the anaerobic conditions. The potential denitrification rate, under the application condition
of nitrate, ranged from 0.13 to 0.26 μg N cm−3 h−1 in the flooded region and from 0.77 to 1.5 μg N cm−3 h−1 in the exposed region. The potential rates in the flooded region had a tendency to be lower than those in the exposed region,
implying that the number of denitrifying bacteria in the flooded region was low due to inactivation of aerobic respiration
and denitrification in the denitrifying bacteria community. Kinetic parameters, maximum rate (V
max) and half-saturation constant (K
s) for denitrification were calculated on the experimental procedures of the wetting–drying cycles of sediments. Both parameters
decreased by the wetting treatment and increased by the drying treatment. The fluctuation of V
max values with wetting–drying cycles indicated that the number of denitrifying bacteria was influenced by aerobic respiration
and denitrification in the denitrifying bacteria community similar to the potential rates, and denitrifying enzyme was induced
by the nitrate supplied by nitrification accelerated through the drying process. On the other hand, the fluctuation of K
s values implied that members of denitrifying bacteria were shifted to members of high nitrate affinity by wetting treatment
and of low nitrate affinity by drying treatment. 相似文献
4.
Nitrifying granules cultivation in a sequencing batch reactor at a low organics-to-total nitrogen ratio in wastewater 总被引:4,自引:0,他引:4
It is possible to cultivate aerobic granular sludge at a low organic loading rate and organics-to-total nitrogen (COD/N) ratio
in wastewater in the reactor with typical geometry (height/diameter = 2.1, superficial air velocity = 6 mm/s). The noted nitrification
efficiency was very high (99%). At the highest applied ammonia load (0.3 ± 0.002 mg NH4+–N g total suspended solids (TSS)−1 day−1, COD/N = 1), the dominating oxidized form of nitrogen was nitrite. Despite a constant aeration in the reactor, denitrification
occurred in the structure of granules. Applied molecular techniques allowed the changes in the ammonia-oxidizing bacteria
(AOB) community in granular sludge to be tracked. The major factor influencing AOB number and species composition was ammonia
load. At the ammonia load of 0.3 ± 0.002 mg NH4+–N g TSS−1 day−1, a highly diverse AOB community covering bacteria belonging to both the Nitrosospira and Nitrosomonas genera accounted for ca. 40% of the total bacteria in the biomass. 相似文献
5.
Membrane-aerated biofilms (MABs) are an effective means to achieve nitrification and denitrification of wastewater. In this
research, microsensors, fluorescence in situ hybridization (FISH), and modeling were used to assess the impact of bulk liquid
biological oxygen demand (BOD) concentrations on the activity and microbial community structure of nitrifying MABs. With 1 g
m−3 BOD in the bulk liquid, the nitrification rate was 1.3 g N m−2 day−1, slightly lower than the 1.5 g N m−2 day−1 reported for no bulk liquid BOD. With bulk liquid BOD concentrations of 3 and 10 g m−3, the rates decreased to 1 and 0.4 g N m−2 day−1, respectively. The percent denitrification increased from 20% to 100% when the BOD increased from 1 to 10 g m−3 BOD. FISH results indicated increasing abundance of heterotrophs with increasing bulk liquid BOD, consistent with the increased
denitrification rates. Modeling was used to assess the effect of BOD on nitrification rates and to compare an MAB to a conventional
biofilm. The model-predicted nitrification rates were consistent with the experimental results. Also, nitrification in the
MAB was much less sensitive to BOD inhibition than the conventional biofilm. The MAB achieved concurrent nitrification and
denitrification, whereas little denitrification occurred in the conventional biofilm. 相似文献
6.
Ecosystem restoration by rewetting of degraded fens led to the new formation of large-scale shallow lakes in the catchment
of the River Peene in NE Germany. We analyzed the biomass and the nutrient stock of the submersed (Ceratophyllum demersum) and the floating macrophytes (Lemna minor and Spirodela polyrhiza) in order to assess their influence on temporal nutrient storage in water bodies compared to other freshwater systems. Ceratophyllum demersum displayed a significantly higher biomass production (0.86–1.19 t DM = dry matter ha−1) than the Lemnaceae (0.64–0.71 t DM ha−1). The nutrient stock of submersed macrophytes ranged between 28–44 kg N ha−1 and 8–12 kg P ha−1 and that of floating macrophytes between 14–19 kg N ha−1 and 4–5 kg P ha−1 which is in the range of waste water treatment plants. We found the N and P stock in the biomass of aquatic macrophytes being
20–900 times and up to eight times higher compared to the nutrient amount of the open water body in the shallow lakes of rewetted
fens (average depth: 0.5 m). Thereafter, submersed and floating macrophytes accumulate substantial amounts of dissolved nutrients
released from highly decomposed surface peat layers, moderating the nutrient load of the shallow lakes during the growing
season from April to October. In addition, the risk of nutrient loss to adjacent surface waters becomes reduced during this
period. The removal of submersed macrophytes in rewetted fens to accelerate the restoration of the low nutrient status is
discussed. 相似文献
7.
Denitrification activity and oxygen dynamics in Arctic sea ice 总被引:1,自引:0,他引:1
Søren Rysgaard Ronnie N. Glud Mikael K. Sejr Martin E. Blicher Henrik J. Stahl 《Polar Biology》2008,31(5):527-537
Denitrification and oxygen dynamics were investigated in the sea ice of Franklin Bay (70°N), Canada. These investigations
were complemented with measurements of denitrification rates in sea ice from different parts of the Arctic (69°N–85°N). Potential
for bacterial denitrification activity (5–194 μmol N m−2 day−1) and anammox activity (3–5 μmol N m−2 day−1) in melt water from both first-year and multi-year sea ice was found. These values correspond to 27 and 7%, respectively,
of the benthic denitrification and anammox activities in Arctic sediments. Although we report only potential denitrification
and anammox rates, we present several indications that active denitrification in sea ice may occur in Franklin Bay (and elsewhere):
(1) despite sea ice-algal primary production in the lower sea ice layers, heterotrophic activity resulted in net oxygen consumption
in the sea ice of 1–3 μmol l−1 sea ice per day at in situ light conditions, suggesting that O2 depletion may occur prior to the spring bloom. (2) The ample organic carbon (DOC) and NO3
− present in sea ice may support an active denitrification population. (3) Measurements of O2 conditions in melted sea ice cores showed very low bulk concentrations, and in some cases anoxic conditions prevailed. (4)
Laboratory studies using planar optodes for measuring the high-resolution two-dimensional O2 distributions in sea ice confirmed the very dynamic and heterogeneous O2 distribution in sea ice, displaying a mosaic of microsites of high and low O2 concentrations. Brine enclosures and channels were strongly O2 depleted in actively melting sea ice, and anoxic conditions in parts of the brine system would favour anaerobic processes. 相似文献
8.
We examined the hydrologic controls on nitrogen biogeochemistry in the hyporheic zone of the Tanana River, a glacially-fed
river, in interior Alaska. We measured hyporheic solute concentrations, gas partial pressures, water table height, and flow
rates along subsurface flowpaths on two islands for three summers. Denitrification was quantified using an in situ 15NO3− push–pull technique. Hyporheic water level responded rapidly to change in river stage, with the sites flooding periodically
in mid−July to early−August. Nitrate concentration was nearly 3-fold greater in river (ca. 100 μg NO3−–N l−1) than hyporheic water (ca. 38 μg NO3−–N l−1), but approximately 60–80% of river nitrate was removed during the first 50 m of hyporheic flowpath. Denitrification during
high river stage ranged from 1.9 to 29.4 mg N kg sediment−1 day−1. Hotspots of methane partial pressure, averaging 50,000 ppmv, occurred in densely vegetated sites in conjunction with mean
oxygen concentration below 0.5 mgO2 l−1. Hyporheic flow was an important mechanism of nitrogen supply to microbes and plant roots, transporting on average 0.41 gNO3−–N m−2 day−1, 0.22 g NH4+–N m−2 day−1, and 3.6 g DON m−2 day−1 through surface sediment (top 2 m). Our results suggest that denitrification can be a major sink for river nitrate in boreal
forest floodplain soils, particularly at the river-sediment interface. The stability of the river hydrograph and the resulting
duration of soil saturation are key factors regulating the redox environment and anaerobic metabolism in the hyporheic zone. 相似文献
9.
Robert G. Björk Leif Klemedtsson Ulf Molau Jan Harndorf Anja Ödman Reiner Giesler 《Plant and Soil》2007,294(1-2):247-261
The spatial distribution of organic soil nitrogen (N) in alpine tundra was studied along a natural environmental gradient,
covering five plant communities, at the Latnjajaure Field Station, northern Swedish Lapland. The five communities (mesic meadow,
meadow snowbed, dry heath, mesic heath, and heath snowbed) are the dominant types in this region and are differentiated by
soil pH. Net N mineralization, net ammonification, and net nitrification were measured using 40-day laboratory incubations
based on extractable NH4+ and NO3−. Nitrification enzyme activity (NEA), denitrification enzyme activity (DEA), amino acid concentrations, and microbial respiration
were measured for soils from each plant community. The results show that net N mineralization rates were more than three times
higher in the meadow ecosystems (mesic meadow 0.7 μg N g−1 OM day−1 and meadow snowbed 0.6 μg N g−1 OM day−1) than the heath ecosystems (dry heath 0.2 μg N g−1 OM day−1, mesic heath 0.1 μg N g−1 OM day−1 and heath snowbed 0.2 μg N g−1 OM day−1). The net N mineralization rates were negatively correlated to organic soil C/N ratio (r = −0.652, P < 0.001) and positively correlated to soil pH (r = 0.701, P < 0.001). Net nitrification, inorganic N concentrations, and NEA rates also differed between plant communities; the values
for the mesic meadow were at least four times higher than the other plant communities, and the snowbeds formed an intermediate
group. Moreover, the results show a different pattern of distribution for individual amino acids across the plant communities,
with snowbeds tending to have the highest amino acid N concentrations. The differences between plant communities along this
natural gradient also illustrate variations between the dominant mycorrhizal associations in facilitating N capture by the
characteristic functional groups of plants.
Responsible Editor: Bernard Nicolardot 相似文献
10.
Nitrogen Transformations in Flowpaths Leading from Soils to Streams in Amazon Forest and Pasture 总被引:1,自引:0,他引:1
Joaquín Chaves Christopher Neill Sonja Germer Sergio Gouveia Neto Alex V. Krusche Adriana Castellanos Bonilla Helmut Elsenbeer 《Ecosystems》2009,12(6):961-972
The modification of large areas of tropical forest to agricultural uses has consequences for the movement of inorganic nitrogen
(N) from land to water. Various biogeochemical pathways in soils and riparian zones can influence the movement and retention
of N within watersheds and affect the quantity exported in streams. We used the concentrations of NO3
− and NH4
+ in different hydrological flowpaths leading from upland soils to streams to investigate inorganic N transformations in adjacent
watersheds containing tropical forest and established cattle pasture in the southwestern Brazilian Amazon Basin. High NO3
− concentrations in forest soil solution relative to groundwater indicated a large removal of N mostly as NO3
− in flowpaths leading from soil to groundwater. Forest groundwater NO3
− concentrations were lower than in other Amazon sites where riparian zones have been implicated as important N sinks. Based
on water budgets for these watersheds, we estimated that 7.3–10.3 kg N ha−1 y−1 was removed from flowpaths between 20 and 100 cm, and 7.1–10.2 kg N ha−1 y−1 was removed below 100 cm and the top of the groundwater. N removal from vertical flowpaths in forest exceeded previously
measured N2O emissions of 3.0 kg N ha−1 y−1 and estimated emissions of NO of 1.4 kg N ha−1 y−1. Potential fates for this large amount of nitrate removal in forest soils include plant uptake, denitrification, and abiotic
N retention. Conversion to pasture shifted the system from dominance by processes producing and consuming NO3
− to one dominated by NH4
+, presumably the product of lower rates of net N mineralization and net nitrification in pasture compared with forest. In
pasture, no hydrological flowpaths contained substantial amounts of NO3
− and estimated N removal from soil vertical flowpaths was 0.2 kg N ha−1 y−1 below the depth of 100 cm. This contrasts with the extent to which agricultural sources dominate N inputs to groundwater
and stream water in many temperate regions. This could change, however, if pasture agriculture in the tropics shifts toward
intensive crop cultivation. 相似文献
11.
Kyung Won Seo Su Jin Heo Yowhan Son Nam Jin Noh Sue Kyoung Lee Chun Gyeong Yoon 《Landscape and Ecological Engineering》2011,7(1):93-99
This study was conducted to examine the influences of soil-moisture conditions on soil nitrogen (N) dynamics, including in
situ soil N mineralization, N availability, and denitrification in a pure Alnus japonica forest located in Seoul, central Korea. The soil N mineralization, N availability, and denitrification were determined using
the buried bag incubation method, ion exchange resin bag method, and acetylene block method, respectively. The annual net
N mineralization rate (kg N ha−1 year−1) and annual N availability (mg N bag−1) were 40.26 and 80.65 in the relatively dry site, −5.43 and 45.39 in the moist site, and 7.09 and 39.17 in the wet site,
respectively. The annual net N mineralization rate and annual N availability in the dry site were significantly higher than
those in the moist and wet sites, whereas there was no significant difference between the moist and wet sites. The annual
mean denitrification rate (kg N ha−1 year−1) in the dry, moist, and wet sites was 2.37, 2.76, and 1.59, respectively. However, there was no significant difference among
sites due to the high spatial and temporal variations. Our results indicate that soil-moisture condition influenced the in
situ N mineralization and resin bag N availability in an A. japonica forest, and treatments of proper drainage for poorly drained sites would increase soil N mineralization and N availability
and consequently be useful to conserve and manage the A. japonica forest. 相似文献
12.
This study evaluated the sources, sinks, and factors controlling net export of nitrogen (N) from watersheds on the west coast
of the US. We calculated input of new N to 22 watersheds for 1992 and 2002. 1992 inputs ranged from 541 to 11,644 kg N km−2 year−1, with an overall area-weighted average of 1,870 kg N km−2 year−1. In 2002, the range of inputs was 490–10,875 kg N km−2 year−1, averaging 2,158 kg N km−2 year−1. Fertilizer was the most important source of new N, averaging 956 (1992) and 1,073 kg N km−2 year−1 (2002). Atmospheric deposition was the next most important input, averaging 833 (1992) and 717 kg N km−2 year−1 (2002), followed by biological N fixation in agricultural lands. Riverine N export, calculated based on measurements taken
at the furthest downstream USGS water quality monitoring station, averaged 165 (1992) and 196 kg N km−2 year−1 (2002), although data were available for only 7 watersheds at the latter time point. Downstream riverine N export was correlated
with variations in streamflow (export = 0.94 × streamflow − 5.65, R
2 = 0.66), with N inputs explaining an additional 16% of the variance (export = 1.06 × streamflow + 0.06 × input − 227.78,
R
2 = 0.82). The percentage of N input that is exported averaged 12%. Percent export was also related to streamflow (%export = 0.05 × streamflow − 2.61,
R
2 = 0.60). The correlations with streamflow are likely a result of its large dynamic range in these systems. However, the processes
that control watershed N export are not yet completely understood. 相似文献
13.
R. Thomas James Wayne S. Gardner Mark J. McCarthy Stephen A. Carini 《Hydrobiologia》2011,669(1):199-212
Total nitrogen (TN) in Lake Okeechobee, a large, shallow, turbid lake in south Florida, has averaged between 90 and 150 μM
on an annual basis since 1983. No TN trends are evident, despite major storm events, droughts, and nutrient management changes
in the watershed. To understand the relative stability of TN, this study evaluates nitrogen (N) dynamics at three temporal/spatial
levels: (1) annual whole lake N budgets, (2) monthly in-lake water quality measurements in offshore and nearshore areas, and
(3) isotope addition experiments lasting 3 days and using 15N-ammonium (15NH4
+) and 15N-nitrate (15NO3
−) at two offshore locations. Budgets indicate that the lake is a net sink for N. TN concentrations were less variable than
net N loads, suggesting that in-lake processes moderate these net loads. Monthly NO3
− concentrations were higher in the offshore area and higher in winter for both offshore and nearshore areas. Negative relationships
between the percentage of samples classified as algal blooms (defined as chlorophyll a > 40 μg l−1) and inorganic N concentrations suggest N-limitation. Continuous-flow experiments over intact sediment cores measured net
fluxes (μmol N m−2 h−1) between 0 and 25 released from sediments for NH4
+, 0–60 removed by sediments for NO3
−, and 63–68 transformed by denitrification. Uptake rates in the water column (μmol N m−2 h−1) determined by isotope dilution experiments and normalized for water depth were 1,090–1,970 for NH4
+ and 59–119 for NO3
−. These fluxes are similar to previously reported results. Our work suggests that external N inputs are balanced in Lake Okeechobee
by denitrification. 相似文献
14.
Changes of microbial characteristics in a full-scale submerged membrane bioreactor system (capacity, 60,000 m3 day−1) treating sewage were monitored over the start-up period (96 days). Fluorescence in situ hybridization analysis showed that
the percentages of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (nitrobacter-related population) in total
bacteria counted with DAPI staining increased significantly from 1.9% and 0.9% to 4.5% and 2.8%, corresponding to an increase
of the specific ammonium oxidizing rate (from 0.06 to 0.12 kg N kg−1 mixed liquor suspended solids (MLSS) per day) and the specific nitrate forming rate (from 0.05 to 0.10 kg N kg−1 MLSS day−1). Both the denaturing gradient gel electrophoresis of polymerase chain reaction and clone library results showed that the
AOB was dominated by the genus Nitrosomonas, the diversity of which increased markedly with operational time. Most of the day 2 clones were closely related with the
uncultured Nitrosomonas sp. clone Ninesprings-49S amoA gene (AY356450.1) originated from activated sludge, while the day 96 clone library showed a more diverse distribution characterized
by the appearance of the oligotrophic nitrifiers like the Nitrosomonas oligotropha- and Nitrosomonas ureae-like bacteria, perhaps due to the interception by membrane and the low food-to-microorganisms ratio environment. The above
results show that the membrane bioreactor system was characterized by the increased diversity and percentage of nitrifiers,
which made it possible to achieve a stable and high efficient nitrification. Ammonia-oxidizing archaea with the changing population
structures were also detected, but their roles for ammonia oxidation in the system need further studies. 相似文献
15.
Nitrification in fixed-bed reactors treating saline wastewater 总被引:2,自引:0,他引:2
Utomo Sudarno Stephan Bathe Josef Winter Claudia Gallert 《Applied microbiology and biotechnology》2010,85(6):2017-2030
Halophilic nitrifiers belonging to the genus Nitrosomonas and Nitrospira were enriched from seawater and marine sediment samples of the North Sea. The maximal ammonia oxidation rate (AOR) in batch
enrichments with seawater was 15.1 mg N L−1 day−1. An intermediate nitrite accumulation was observed. Two fixed-bed reactors for continuous nitrification with either polyethylene/clay
sinter lamellas (FBR A) or porous ceramic rings (FBR B) were run at two different ammonia concentrations, three different
ammonia loading rates (ALRs), ± pH adjustment, and at an increased upflow velocity. A better overall nitrification without
nitrite accumulation was observed in FBR B. However, FBR A revealed a higher AOR and nitrite oxidation rate of 6 and 7 mg N L−1 h−1, compared to FBR B with 5 and 5.9 mg N L−1 h−1, respectively. AORs in the FBRs were at least ten times higher than in suspended enrichment cultures. Whereas a shift within
the ammonia-oxidizing population in the genus Nitrosomonas at the subspecies level occurred in FBR B with synthetic seawater at an increasing ALR and a decreasing pH, the nitrite oxidizing
Nitrospira population apparently did not change. 相似文献
16.
Han Gil Choi Ki Hoon Lee Hyun Il Yoo Pil Jun Kang Young Sik Kim Ki Wan Nam 《Journal of applied phycology》2008,20(5):729-735
The effects of temperature, irradiance, and daylength on Sargassum horneri growth were examined at the germling and adult stages to discern their physiological differences. Temperature–irradiance
(10, 15, 20, 25, 30°C × 20, 40, 80 μmol photons m−2s−1) and daylength (8, 12, 16, 24 h) experiments were carried out. The germlings and blades of S. horneri grew over a wide range of temperatures (10–25°C), irradiances (20–80 μmol photons m−2s−1), and daylengths (8–24 h). At the optimal growth conditions, the relative growth rates (RGR) of the germlings were 21% day−1 (25°C, 20 μmol photons m−2s−1) and 13% day−1 (8 h daylength). In contrast, the RGRs of the blade weights were 4% day−1 (15°C, 20 μmol photons m−2s−1) and 5% day−1 (12 h daylength). Negative growth rates were found at 20 μmol photons m−2s−1 of 20°C and 25°C treatments after 12 days. This phenomenon coincides with the necrosis of S. horneri blades in field populations. In conclusion, we found physiological differences between S. horneri germlings and adults with respect to daylength and temperature optima. The growth of S. horneri germlings could be enhanced at 25°C, 20 μmol photons m−2s−1, and 8 h daylength for construction of Sargassum beds and restoration of barren areas. 相似文献
17.
The present study was undertaken to assess the benefit and compare the functioning of AM fungi on wheat grown conventionally
and on beds. Ten treatment combinations were used, treatments 1 and 2: no fertilizers with and without arbuscular mycorrhizal
(AM) fungi (In vitro produced Glomus intraradices); 3:100% of recommended NPK: (120 kg ha−1 N; 60 kg ha−1 P; 50 kg ha−1 K), and 4 and 5: 75% of recommended NPK dose with and without AM inoculation in a 5 × 2 split-plot design on wheat using
conventional/flat system and elevated/raised bed system. The maximum grain yield (3.84 t ha−1) was obtained in AM fungi inoculated plots of raised bed system applied with 75% NPK and was found higher (although non-
significant) than the conventional (3.73 t ha−1) system. The AM inoculation at 75% fertilizer application can save 8.47, 5.38 kg P and 16.95, 10.75 kg N ha−1, respectively, in bed and conventional system. While comparing the yield response with 100% fertilizer application alone,
AM inoculation was found to save 20.30, 15.79 kg P and 40.60, 31.59 kg N ha−1, respectively, in beds and conventional system. Mycorrhizal inoculation at 75% NPK application particularly in raised bed
system seems to be more efficient in saving fertilizer inputs and utilizing P for producing higher yield and growth unlike
non-mycorrhizal plants of 100% P. Besides the yield, mycorrhizal plants grown on beds had higher AM root colonization, soil
dehydrogenases activity, and P-uptake. The present study indicates that the inoculation of AM fungi to wheat under raised
beds is better response (although non-significantly higher) to conventional system and could be adopted for achieving higher
yield of wheat at reduced fertilizer inputs after field validation. 相似文献
18.
Simultaneous nutrients and carbon removal during pretreated swine slurry degradation in a tubular biofilm photobioreactor 总被引:1,自引:0,他引:1
Ignacio de Godos Cristina González Eloy Becares Pedro A. García-Encina Raúl Muñoz 《Applied microbiology and biotechnology》2009,82(1):187-194
The biodegradation potential of an innovative enclosed tubular biofilm photobioreactor inoculated with a Chlorella sorokiniana strain and an acclimated activated sludge consortium was evaluated under continuous illumination and increasing pretreated
(centrifuged) swine slurry loading rates. This photobioreactor configuration provided simultaneous and efficient carbon, nitrogen,
and phosphorous treatment in a single-stage process at sustained nitrogen and phosphorous removals efficiencies ranging from
94% to 100% and 70–90%, respectively. Maximum total organic carbon (TOC), NH4
+, and PO4
3− removal rates of 80 ± 5 g C mr
−3 day−1, 89 ± 5 g N mr
−3 day−1, and 13 ± 3 g P mr
−3 day−1, respectively, were recorded at the highest swine slurry loadings (TOC of 1,247 ± 62 mg L−1, N–NH4
+ of 656 ± 37 mg L−1, P–PO4
3+ of 117 ± 19 mg L−1, and 7 days of hydraulic retention time). The unusual substrates diffusional pathways established within the phototrophic
biofilm (photosynthetic O2 and TOC/NH4
+ diffusing from opposite sides of the biofilm) allowed both the occurrence of a simultaneous denitrification/nitrification
process at the highest swine slurry loading rate and the protection of microalgae from any potential inhibitory effect mediated
by the combination of high pH and high NH3 concentrations. In addition, this biofilm-based photobioreactor supported efficient biomass retention (>92% of the biomass
generated during the pretreated swine slurry biodegradation). 相似文献
19.
Shannon KE Saleh-Lakha S Burton DL Zebarth BJ Goyer C Trevors JT 《Antonie van Leeuwenhoek》2011,100(2):183-195
The effect of glucose addition (0 and 500 μg C g−1 soil) and nitrate (NO3) addition (0, 10, 50 and 500 μg NO3–N g−1 soil) on nitric oxide reductase (cnorB) gene abundance and mRNA levels, and cumulative denitrification were quantified over 48 h in anoxic soils inoculated with
Pseudomonas mandelii. Addition of glucose-C significantly increased cnorB
p
(P. mandelii and related species) mRNA levels and abundance compared with soil with no glucose added, averaged over time and NO3 addition treatments. Without glucose addition, cnorB
p
mRNA levels were higher when 500 μg NO3–N g−1 soil was added compared with other NO3 additions. In treatments with glucose added, addition of 50 μg NO3–N g−1 soil resulted in higher cnorB
p
mRNA levels than soil without NO3 but was not different from the 10 and 500 μg NO3–N g−1 treatments. cnorB
p
abundance in soils without glucose addition was significantly higher in soils with 500 μg NO3–N g−1 soil compared to lower N-treated soils. Conversely, addition of 500 μg NO3–N g−1 soil resulted in lower cnorB
p
abundance compared with soil without N-addition. Over 48 h, cumulative denitrification in soils with 500 μg glucose-C g−1 soil, and 50 or 500 μg NO3–N g−1 was higher than all other treatments. There was a positive correlation between cnorB
p
abundance and cumulative denitrification, but only in soils without glucose addition. Glucose-treated soils generally had
higher cnorB
p
abundance and mRNA levels than soils without glucose added, however response of cnorB
p
abundance and mRNA levels to NO3 supply depended on carbon availability. 相似文献
20.
Denitrification Potential in Lake Sediment Increases Across a Gradient of Catchment Agriculture 总被引:1,自引:0,他引:1
Intensification of catchment agriculture has increased nutrient loads and accelerated eutrophication in some lakes, often
resulting in episodic harmful algal blooms or prolonged periods of anoxia. The influence of catchment agriculture on lake
sediment denitrification capacity as a nitrogen (N) removal mechanism in lakes is largely unknown, particularly in contrast
to research on denitrification in agricultural streams and rivers. We measured denitrification enzyme activity (DEA) to assess
sediment denitrification potential in seven monomictic and three polymictic lakes that range in the proportion of agriculture
in the catchment from 3 to 96% to determine if there is a link between agricultural land use in the lake catchment and sediment
denitrification potential. We collected sediment cores for DEA measurements over 3 weeks in austral spring 2008 (October–November).
Lake Okaro, with 96% catchment agriculture, had approximately 15 times higher DEA than Lake Tikitapu, with 3% catchment agriculture
(232.2 ± 55.9 vs. 15.9 ± 4.5 μg N gAFDM−1 h−1, respectively). Additionally, sediment denitrification potential increased with the proportion of catchment in agriculture
(R
2 = 0.85, P < 0.001). Our data suggest that lakes retain a high capacity to remove excess N via denitrification under increasing N loads
from higher proportions of catchment agriculture. However, evidence from the literature suggests that despite a high capacity
for denitrification and longer water residence times, lakes with high N loads will still remove a smaller proportion of their
N load. Lakes have a denitrification potential that reflects the condition of the lake catchment, but more measurements of
in situ denitrification rates across lake catchments is necessary to determine if this capacity translates to high N removal
rates. 相似文献