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1.
Nitrogen uptake and denitrification in restored and unrestored streams in urban Maryland, USA 总被引:2,自引:0,他引:2
Carolyn A. Klocker Sujay S. Kaushal Peter M. Groffman Paul M. Mayer Raymond P. Morgan 《Aquatic Sciences - Research Across Boundaries》2009,71(4):411-424
There is growing interest in rates of nitrate uptake and denitrification in restored streams to better understand the effects
of restoration on nitrogen processing. This study quantified nitrate uptake in two restored and two unrestored streams in
Baltimore, Maryland, USA using nitrate additions, denitrification enzyme assays, and a 15N isotope tracer addition in one of the urban restored streams, Minebank Run. Restoration included either incorporation of
stormwater ponds below a storm drain and catch basins to attenuate flow or hydrologic “reconnection” of a stream channel to
its floodplain. Stream restoration was conducted for restoring aging sanitary and bridge infrastructure and introducing some
stormwater management in watersheds developed prior to current regulations. Denitrification potential in sediments was variable
across streams, whereas nitrate uptake length appeared to be significantly correlated to surface water velocity, which was
low in the restored streams during summer baseflow conditions. Uptake length of NO3
−–N in Minebank Run estimated by 15N tracer addition was 556 m. Whole stream denitrification rates in Minebank Run were 153 mg NO3
−–N m−2 day−1, and approximately 40% of the daily load of nitrate was estimated to be removed via denitrification over a distance of 220.5 m
in a stream reach designed to be hydrologically “connected” to its floodplain. Increased hydrologic residence time in Minebank
Run during baseflow likely influenced rates of whole stream denitrification, suggesting that hydrologic residence time may
be a key factor influencing N uptake and denitrification. Restoration approaches that increase hydrologic “connectivity” with
hyporheic sediments and increase hydrologic residence time may be useful for stimulating denitrification. More work is necessary,
however, to examine changes in denitrification rates in restored streams across different seasons, variable N loads, and in
response to the “flashy” hydrologic flow conditions during storms common in urban streams. 相似文献
2.
A critical factor controlling changes in the acidity of coastal waters is the alkalinity of the water. Concentrations of alkalinity
are determined by supply from rivers and by in situ processes such as biological production and denitrification. A 2-year
study based on 15 cruises in Liverpool Bay followed the seasonal cycles of changing concentrations of total alkalinity (TA)
and total dissolved inorganic carbon (DIC) in relation to changes caused by the annual cycle of biological production during
the mixing of river water into the Bay. Consistent annual cycles in concentrations of nutrients, TA and DIC were observed
in both years. At a salinity of 31.5, the locus of primary production during the spring bloom, concentrations of NO
x
decreased by 25 ± 4 μmol kg−1 and DIC by 106 ± 16 μmol kg−1. Observed changes in TA were consistent with the uptake of protons during primary biological production. Concentrations of
TA increased by 33 ± 8 μmol kg−1 (2009) and 33 ± 15 μmol kg−1 (2010). The impact of changes in organic matter on the measured TA appears likely to be small in this area. Thomas et al.
(2009) suggested that denitrification may enhance the CO2 uptake of the North Sea by 25%, in contrast we find that although denitrification is a significant process in itself, it
does not increase concentrations of TA relative to those of DIC and so does not increase buffer capacity and potential uptake
of CO2 into shelf seawaters. For Liverpool Bay historical data suggest that higher concentrations of TA during periods of low flow
are likely to contribute in part to the observed change in TA between winter and summer but the appropriate pattern cannot
be identified in recent low-frequency river data. On a wider scale, data for the rivers Mersey, Rhine, Elbe and Weser show
that patterns of seasonal change in concentrations of TA in river inputs differ between river systems. 相似文献
3.
William D. Taylor 《Aquatic Sciences - Research Across Boundaries》2010,72(1):13-20
Techniques recently developed for measuring P regeneration, particulate P turnover, and PO4
3− concentration in lakewater assume that dissolved 32P (D32P) released by plankton is PO4
3−. To test this assumption, I obtained samples of D32P regenerated from whole plankton communities by labeling the communities with 32P-PO4
3− then blocking re-uptake and transformation of regenerated D32P with two competitive inhibitors, unlabeled 31P-PO4
3− and pyrophosphate. Under these conditions, regenerated D32P accumulated and could be examined by gel chromatography to discern how much of it was 32P-PO4
3− versus higher molecular weight P compounds. I estimated that most or all of the D32P released was 32P-PO4
3−. I also observed that the amount of DP observed on filtration of lakewater depended on the method employed to obtain the
filtrate. Therefore, I also separated particulate 32P from D32P with dialysis membrane (100,000 MW cutoff) without pressure. There was little DP larger than PO4
3− and no DP >5,000 MW in the dialysate, leading me to conclude that DP <100,000 MW was a minor component of both regenerated
and total P. I suggest that under P-limited conditions that most dissolved P observed in lakewater filtrates may be intact
viruses and cell constituents liberated in the filtration process. These results are mostly congruent with Lean’s (J Fish
Res Board Can 30:1525–1536, 1973) model of P-cycling in lake plankton, although the nature of “colloidal P” in Lean’s model should be further investigated. 相似文献
4.
Sediment resuspension in two adjacent shallow coastal lakes: controlling factors and consequences on phosphate dynamics 总被引:1,自引:0,他引:1
Inmaculada de Vicente Luis Cruz-Pizarro Francisco J. Rueda 《Aquatic Sciences - Research Across Boundaries》2010,72(1):21-31
A combination of field measurements, modelling and laboratory experiments was used to evaluate the potential impact of sediment
resuspension on phosphorus (P) dynamics. The study was carried out in two adjacent shallow coastal lakes (Lake Honda and Lake
Nueva) which, due to their geographic proximity (only 200 m apart), are subject to equal meteorological forcing and represent
ideal systems to study how morphometry and sediment properties relate to wind events. The focusing factors (a measure of the
fluxes of sediment into the water column through resuspension) estimated by comparing settling fluxes measured in surface
sediment traps with those measured in bottom traps, were significantly larger (approximately 34% larger) in Lake Honda (LH;
1.18) than in Lake Nueva (LN; 0.88). Our model estimates of resuspension fluxes (E) were also ca. 40% larger in LH than in LN, in agreement with the observed focusing factors. The larger resuspension fluxes
encountered in LH, in comparison with LN, can mainly be explained by differences in lake morphometry. Still, they could arise
from differences in grain size distribution or in benthic algae concentration encountered in the lake sediments. By means
of adsorption experiments in the laboratory, we show that resuspension events will have different effects on P-dynamics in
LH and LN. While the resuspended material from LH tends to adsorb phosphate (PO4
3−), removing it from the water column, in LN the resuspended sediments tend to increase the availability of PO4
3− in solution. These differences arise from (1) higher concentrations of PO4
3− in water in LH compared to LN; and (2) larger PO4
3−adsorption capacity of the LH sediments as a result of the more abundant iron oxyhydroxides and clay. 相似文献
5.
Net autotrophy in a fluvial lake: the relative role of phytoplankton and floating-leaved macrophytes
Monica Pinardi Marco Bartoli Daniele Longhi Pierluigi Viaroli 《Aquatic Sciences - Research Across Boundaries》2011,73(3):389-403
This study combined water- and sediment flux measurements with mass balances of dissolved gas and inorganic matter to determine
the importance of pelagic and benthic processes for whole-system metabolism in a eutrophic fluvial lake. Mass balances of
dissolved O2, inorganic carbon (DIC), nitrogen (DIN), phosphorous (SRP), particulate N (PN) and P (PP) and Chl a were calculated at a nearly monthly frequency by means of repeated sampling at the lake inlet and outlet. Simultaneously,
benthic fluxes of gas and nutrients, including denitrification rates, and the biomass of the dominant pleustophyte (Trapa natans) were measured, and fluxes of O2 and CO2 across the water–atmosphere interface were estimated from diel changes in outlet concentrations. On an annual scale, Middle
Lake exhibited CO2 supersaturation, averaging 313% (range 86–562%), but was autotrophic with a net O2 production (6.35 ± 2.05 mol m−2 y−1), DIC consumption (−31.18 ± 18.77 mol m−2 y−1) and net export of Chl a downstream (8.38 ± 0.95 mol C m−2 y−1). Phytoplankton was the main driver of Middle Lake metabolism, with a net primary production estimated at 33.24 mol O2 m−2 y−1, corresponding to a sequestration of 4.18 and 0.26 mol m−2 y−1 of N and P, respectively. At peak biomass, T. natans covered about 18% of Middle Lake’s surface and fixed 2.46, 0.17 and 0.02 mol m−2 of C, N and P, respectively. Surficial sediments were a sink for O2 (−14.47 ± 0.65 mol O2 m−2 y−1) and a source of DIC and NH4
+ (18.84 ± 2.80 mol DIC m−2 y−1 and 0.83 ± 0.16 mol NH4
+ m−2 y−1), and dissipated nitrate via denitrification (1.44 ± 0.11 mol NO3
− m−2 y−1). Overall, nutrient uptake by primary producers and regeneration from sediments were a minor fraction of external loads.
This work suggests that the creation of fluvial lakes can produce net autotrophic systems, with elevated rates of phytoplanktonic
primary production, largely sustained by allochtonous nutrient inputs. These hypereutrophic aquatic bodies are net C sinks,
although they simultaneously release CO2 to the atmosphere. 相似文献
6.
Detlev Ingendahl Dietrich Borchardt Nicole Saenger Peter Reichert 《Aquatic Sciences - Research Across Boundaries》2009,71(4):399-410
To quantify the contribution of hyporheic community respiration to whole running-water ecosystem respiration in a cultural
landscape setting, we studied the vertical hydraulic exchange in riffle–pool sequences of the River Lahn (Germany). We used
flow through curves from four tracer experiments to estimate flow velocities in the surface and subsurface water. Generally,
vertical exchange velocities were higher in riffle sections and a high temporal variability was observed (range of values
0.11–1.08 m day−1). We then used (1) the exchange velocities and (2) time series of dissolved oxygen concentration in surface and subsurface
water to calculate hyporheic respiration. Hyporheic respiration was estimated in a range of 10–50 mg O2 m−3 day−1 for the upper sediment layer (first 20 cm). It was much lower in the deeper sediment layer (20–40 cm), ranging from 0 to
10 mg O2 m−3 day−1 (volumes are volumes of interstitial water; the average porosity was 20%). We determined primary production and respiration
of the biofilm growing on the sediment by modelling dissolved oxygen concentration time series for a 2,450 m long stream reach
(dissolved oxygen concentrations with diurnal variations from 8 to 16 mg L−1). Modelled respiration rates ranged from 2 to 21 g O2 m2 day−1. All information was integrated in a system analysis with numerical simulations of respiration with and without sediments.
Results indicated that hyporheic respiration accounted for 6 to 14% of whole ecosystem respiration. These values are much
lower than in other whole system respiration studies on more oligotrophic river systems. 相似文献
7.
《Continental Shelf Research》1999,19(9):1113-1141
Relationships among primary production, chlorophyll, nutrients, irradiance and mixing processes were examined along the salinity gradient in the Mississippi River outflow region. A series of six cruises were conducted during 1988–1992 at various times of year and stages of river discharge. Maximum values of biomass and primary production were typically observed at intermediate salinities and coincided with non-conservative decreases in nutrients along the salinity gradient. Highest values of productivity (>10 gC m−2 d−1) and biomass (>30 mg chlorophyll a m−3) were observed in April 1988, July–August 1990 and April–May 1992; values were lower in March and September 1991. Rates of primary production were apparently constrained by low irradiance and mixing in the more turbid, low salinity regions of the plume, and by nutrient limitation outside the plume. Highest values of primary production occurred at stations where surface nutrient concentrations exhibited large deviations from conservative mixing relationships, indicating that depletion of nutrients was related to phytoplankton uptake. Mixing and advection were important in determining the location and magnitude of primary production maxima and nutrient depletion. In addition to growth within plume surface waters, enhanced growth and/or retention of biomass may have occurred in longer residence time waters at the plume edge and/or beneath the surface plume. Vertical structure of some plume stations revealed the presence of subsurface biomass maxima in intermediate salinity water that was depleted in nutrients presumably by uptake processes. Exchange between subsurface water and the surface plume apparently contributed to the reduction in nutrients at intermediate salinities in the surface layer. DIN (=nitrate+nitrite+ammonium) : PO4 (=phosphate) ratios in river water varied seasonally, with high values in winter and spring and low values in late summer and fall. Periods of high DIN : PO4 ratios in river nutrients coincided with cruises when surface nutrient concentrations and their ratios indicated a high probability for P limitation. N limitation was more likely to occur at high salinities and during late summer and fall. Evidence for Si limitation was also found, particularly in spring. 相似文献
8.
9.
10.
Abiotic effects of UV on planktonic P kinetics 总被引:1,自引:0,他引:1
Jeff M. Sereda Jeff J. Hudson William D. Taylor 《Aquatic Sciences - Research Across Boundaries》2009,71(2):127-134
11.
Dev K. Niyogi Janet M. Bandeff Cem Selman Drew E. Menke 《Aquatic Sciences - Research Across Boundaries》2010,72(2):203-212
We examined nutrient flux, uptake, and transformation along a spring-fed stream in the Ozark region of Missouri, USA, over
the year 2006. Water in Mill Creek originates from several springs, with a single spring contributing over 90% of the stream
discharge during much of the year of study. Soluble reactive phosphate concentrations were usually low (<10 μg L−1) along Mill Creek, but peaked during high discharge. Concentrations of dissolved inorganic nitrogen (DIN) were relatively
high in the spring water, mainly as nitrate, but usually declined across a small pond and the 10-km length of Mill Creek.
During low flows in summer and early autumn, the stream removed over 300 μg L−1 of DIN over its 10-km length, or about 80% of the initial amount. DIN retention along the stream, as a percentage of the
DIN upstream, was related mainly to discharge, with higher flows having much higher DIN concentrations. The net uptake rate
of DIN uptake was 0.91 μg m−2 s−1 in the stream during summer baseflow. The uptake rate declined downstream for different reaches and was closely related to
DIN concentration. In experimental channels, uptake by epilithic algae was one significant sink for nitrate-N in Mill Creek.
In 2006, inorganic nutrient export during a single day after a spring storm was similar to export during 40–100 days of low
flow conditions in summer and early autumn. Our results suggest that significant nutrient retention can occur during baseflow
periods via biological uptake, whereas substantial export occurs during high flow conditions. 相似文献
12.
过氧化钙在处理厌氧底泥中的应用初探 总被引:1,自引:0,他引:1
为改善河道厌氧底质及内源氮、磷等营养盐释放问题,考察对沉水植被恢复的影响,研发可同步解决沉积物供氧和削减内源氮、磷释放的氧缓释材料.实验通过向沉积物-水界面处散点注射不同剂量的过氧化钙(Ca O2),研究界面处溶解氧的动态变化特征及表层沉积物与底层水体之间溶解态氮、磷的交换过程.结果表明:添加Ca O2显著提高了界面处底层上覆水溶解氧浓度,随着Ca O2浓度的增加溶解氧浓度增加,不同处理组之间具有显著差异;Ca O2对沉积物中PO3-4-P释放具有明显的抑制作用,且随Ca O2浓度的增加抑制效果愈加明显,上覆水中可溶性活性磷浓度最大可削减98%.实验开始时,磷释放速率可降至-241.916±22.501 mg/(m2·d),降幅最高可达到144%;Ca O2对沉积物NH+4-N释放的抑制效果不佳,上覆水中NH+4-N浓度随着时间的变化波动性较大,且有逐渐增大的趋势.另外,添加Ca O2会显著提高底层上覆水p H值,不同处理组之间差异显著,但当Ca O2投加量小于0.529 kg/m2时,不会对苦草种子的萌发生长有显著影响,p H值波动在可接受范围内(7.62~10.87).因此,结合污染沉积物的状况,适当地投加Ca O2有望同步解决底质厌氧、内源磷释放及后期沉水植被定植底质生境改善的问题,可推荐为一种黑臭污染底泥治理技术在实际的河道生态工程中应用,其适宜浓度为0.176 kg/m2左右. 相似文献
13.
天津中心城区河网氮磷污染与富营养化特征 总被引:1,自引:0,他引:1
2013年底天津中心城区河道全部连通,形成中心城区河网.为了掌握河网形成后的水质状况,于2014年3月-2015年2月进行了为期1年的定点水质监测,并对其水体氮、磷时空分布及富营养化特征进行分析.结果表明,河网水体氮污染严重,以铵态氮(NH+4-N)为主;磷污染程度较轻,主要形态为磷酸盐(PO3-4-P);河网水体中氮、磷浓度顺水流方向均呈上游高、下游低的空间分布特征;氮、磷各项指标浓度时间变化趋势基本一致,3月均最高,10月均最低,冬季处于相对较低水平;与河网形成前相比,海河干流NH+4-N、总磷(TP)和PO3-4-P浓度年平均值分别下降6.5%、14.7%和16.4%,津河总氮、NH+4-N、硝态氮、TP和PO3-4-P浓度年平均值分别降低18.6%、34.5%、12.9%、31.6%和32.5%,表明河网形成后氮、磷污染程度较之前有所改善,其中津河改善较为明显;河网水体全年处于中度富营养状态,主要为磷限制性状态;河网富营养化防治应遵循以控制营养盐为主的控源、截污、水环境增容和生态补水策略. 相似文献
14.
Agnes Mazot Dmitri Rouwet Yuri Taran Salvatore Inguaggiato Nick Varley 《Bulletin of Volcanology》2011,73(4):423-441
During 2007–2008, three CO2 flux surveys were performed on El Chichón volcanic lake, Chiapas, Mexico, with an additional survey in April 2008 covering
the entire crater floor (including the lake). The mean CO2 flux calculated by sequential Gaussian simulation from the lake was 1,190 (March 2007), 730 (December 2007) and 1,134 g m−2 day−1 (April 2008) with total emission rates of 164 ± 9.5 (March 2007), 59 ± 2.5 (December 2007) and 109 ± 6.6 t day−1 (April 2008). The mean CO2 flux estimated from the entire crater floor area was 1,102 g m−2 day−1 for April 2008 with a total emission rate of 144 ± 5.9 t day−1. Significant change in CO2 flux was not detected during the period of survey, and the mapping of the CO2 flux highlighted lineaments reflecting the main local and regional tectonic patterns. The 3He/4He ratio (as high as 8.1 R
A) for gases in the El Chichón crater is generally higher than those observed at the neighbouring Transmexican Volcanic Belt
and the Central American Volcanic Arc. The CO2/3He ratios for the high 3He/4He gases tend to have the MORB-like values (1.41 × 109), and the CO2/3He ratios for the lower 3He/4He gases fall within the range for the arc-type gases. The high 3He/4He ratios, the MORB-like CO2/3He ratios for the high 3He/4He gases and high proportion of MORB-CO2 (M = 25 ±15%) at El Chichón indicate a greater depth for the generation of magma when compared to typical arc volcanoes. 相似文献
15.
Estimates of population size and biomass of net plankton were made in two tropical fish ponds in relation to the ecological
data over a period of one year. There was a wide spatial and seasonal variation of population size and biomass of net plankton
in two ponds studied. Always predominant over zooplankton, phytoplankton demonstrated three distinct annual peaks in the pond
N-1 while a single peak was obtained in the pond N-2. A variable result was found in two ponds in the values of Shannon index
of general diversity for phyto- and zooplankton. The seasonal changes of phytoplankton number in these ponds showed an inverse
characteristic either with absolute concentration or with the rate of concentration changes of bicarbonate in the water, while
the former and concentration of dissolved oxygen was positively correlated. In the multiple correlation analysis, the greatest
importance of the concentration of PO4 was indicated on the phytoplankton population as HCO
3
−
and dissolved oxygen were not considered to be included in the final regression formula in both the ponds studied but the
rate of changes of HCO
3
−
, PO4 and dissolved oxygen were influential on phytoplankton in the pond N-1. 相似文献
16.
17.
The main objective in this study was to compare the physico-chemical characteristics and biota of a river (Mukuvisi) passing through an urban area to that of a non-urbanised river (Gwebi). Five sites in the Mukuvisi River and five sites in the Gwebi River were sampled for water physico-chemical parameters (pH, conductivity, DO, BOD, TDS, ammonia, Cl, SO42−, PO42−, NO33−, F−, Pb, Cu, Fe, Mn, Zn and Cr) once every month between August, 2012–August, 2013. Cluster analysis based on the physico-chemical parameters grouped the sites into two groups. Mukuvisi River sites formed their own grouping except for one site which was grouped with Gwebi River sites. Principal Component Analysis (PCA) was used to extract the physico-chemical parameters that account for most variations in water quality in the Mukuvisi and Gwebi Rivers. PCA identified sulphate, chloride, fluoride, iron, manganese and zinc as the major factors contributing to the variability of Mukuvisi River water quality. In the Gwebi river, sulphate, nitrate, fluoride and copper accounted for most of the variation in water quality. Canonical Correspondence Analysis (CCA) was used to explore the relationship between physico-chemical parameters and macroinvertebrate communities. CCA plots in both Mukuvisi and Gwebi Rivers showed significant relationships between macroinvertebrate communities and water quality variables. Phosphate, ammonia and nitrates were correlated with Chironomidae and Simulidae. Gwebi River had higher (P < 0.05, ANOVA) macroinvertebrates and fish diversity than Mukuvisi River. Clarias gariepinus from the Mukuvisi River had high liver histological lesions and low AChE activity and this led to lower growth rates in this river. 相似文献
18.
Materials of long-term studies of the concentration and distribution of N forms (NH4+, NO3−, NO2−, Norg) in precipitation, surface water and groundwater are generalized. Precipitation was found to be the main source of N compounds
input into these waters. The effect of anthropogenic factors is local and does not influence the concentration and distribution
of N forms in most water bodies that serve as wastewater recipients. The N forms dominating in precipitation are NO3− and N H4+; Norg dominates in most surface water bodies, and NO3− dominates in groundwater. The median concentrations of Ntot in clear surface and subsurface waters are similar. The obtained characteristics of the concentrations and distribution of
N forms in natural waters of Karelia can be used for other water bodies in the humid zone. 相似文献
19.
20.
Sabine Roedelsperger Michael Kuhn Oleg Makarynskyy Carl Gerstenecker 《Pure and Applied Geophysics》2008,165(6):1131-1151
It is sometimes assumed that steric sea-level variations do not produce a gravity signal as no net mass change, thus no change
of ocean bottom pressure is associated with it. Analyzing the output of two CO2 emission scenarios over a period of 2000 years in terms of steric sea-level changes, we try to quantify the gravitational
effect of steric sea-level variations. The first scenario, computed with version 2.6 of the Earth System Climate Model developed
at the University of Victoria, Canada (UVic ESCM), is implemented with a linear CO2 increase of 1% of the initial concentration of 365 ppm and shows a globally averaged steric effect of 5.2 m after 2000 years.
In the second scenario, computed with UVic ESCM version 2.7, the CO2 concentration increases quasi-exponentially to a level of 3011 ppm and is hold fixed afterwards. The corresponding globally
averaged steric effect in the first 2000 years is 2.3 m. We show, due to the (vertical) redistribution of ocean water masses
(expansion or contraction), the steric effect results also in a small change in the Earth’s gravity field compared to usually
larger changes associated with net mass changes. Maximum effects for computation points located on the initial ocean surface
can be found in scenario 1, with the effect on gravitational attraction and potential ranging from 0.0 to −0.7·10−5 m s−2 and −3·10−3 to 6·10−3 m2 s−2, respectively. As expected, the effect is not zero but negligible for practical applications. 相似文献