Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Nitrate depletion in the riparian zone of a small woodland stream (1988)
    Springer
    Hydrobiologia 157 (1988), S. 231-240 
    Details
    ISSN: 1573-5117
    Keywords: denitrification ; ground water ; nitrate ; organic soils ; riparian zone ; stream
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Field enrichments with nitrate in two spring-fed drainage lines within the riparian zone of a small woodland stream near Toronto, Ontario showed an absence of nitrate depletion. Laboratory experiments with riparian substrates overlain with nitrate enriched solutions revealed a loss of only 5–8% of the nitrate during 48 h incubation at 12°C. However, 22–24% of the initial nitrate was depleted between 24 and 48 h when a second set of substrate cores was incubated at 20°C. Short-term (3 h) incubations of fresh substrates amended with acetylene were used to estimate in situ denitrification potentials which varied from 0.05–3.19 μg N g−1 d−1 for organic and sandy sediments. Denitrification potentials were highly correlated with initial nitrate content of substrate samples implying that low nitrate levels in ground water and riparian substrates may be an important factor in controlling denitrification rates. The efficiency of nitrate removal in spring-fed drainage lines is also limited by short water residence times of 〈 1 h within the riparian zone. These data suggest that routes of ground water movement and substrate characteristics are important in determining nitrate depletion within stream riparian areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00004200
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Soil N mineralization and nitrification in relation to nitrogen solution chemistry in a small forested watershed (1989)
    Springer
    Biogeochemistry 8 (1989), S. 167-184 
    Details
    ISSN: 1573-515X
    Keywords: nitrogen mineralization ; nitrate ; nitrification ; soil water ; ground water ; streams
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Spatial variations in soil processes regulating mineral N losses to streams were studied in a small watershed near Toronto, Ontario. Annual net N mineralization in the 0–8 cm soil was measured in adjacent upland and riparian forest stands using in situ soil incubations from April 1985 to 1987. Mean annual rates of soil N mineralization and nitrification were higher in a maple soil (93.8 and 87.0 kg.ha−1) than in a pine soil (23.3 and 8.2 kg.ha−1 ). Very low mean rates of mineralization (3.3 kg.ha−1) and nitrification (3.4 kg.ha−1) were found in a riparian hemlock stand. Average NO3-N concentrations in soil solutions were 0.3–1.0 mg.L−1 in the maple stand and 〉0.06mg.L−1 in the pine stand. Concentrations of NO3−N in shallow ground water and stream water were 3–4× greater in a maple subwatershed than in a pine subwatershed. Rapid N uptake by vegetation was an important mechanism reducing solution losses of NO3−N in the maple stand. Low rates of nitrification were mainly responsible for negligible NO3−N solution losses in the pine stand.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00001319
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Ground water flow paths in relation to nitrogen chemistry in the near-stream zone (1990)
    Springer
    Hydrobiologia 206 (1990), S. 39-52 
    Details
    ISSN: 1573-5117
    Keywords: ammonium ; biogeochemistry ; denitrification ; ground water ; hydrologic flow paths ; nitrate ; riparian zone ; stream
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Interactions between ground water flow paths and water chemistry were studied in the riparian zone of a small headwater catchment near Toronto, Ontario. Significant variations in oxygen — 18 and chloride indicated the presence of distinct sources of water in the ground water flow system entering the near-stream zone. Shallow ground water at the upland perimeter of the riparian zone had nitrate-N, chloride and dissolved oxygen concentrations which ranged between 100–180 µg L−1, 1.2–1.8 mg L−1 and 4.6–9.1 mg L−1 respectively. Concentrations of nitrate — N in deep ground water flowing upward beneath the riparian wetland were 〈 10 µg L−1, whereas chloride and dissolved oxygen ranged between 0.6–0.9 mg L−1 and 0.4–2.2 mg L−1 respectively. Ammonium — N concentrations (20–60 µg L−1) were similar in shallow and deep ground water. Ground water was transported through the wetland to the stream by three hydrologic pathways. 1) Shallow ground water emerged as springs near the base of the hillslope producing surface rivulets which crossed the riparian zone to the stream. 2) Deep ground water flowed upward through organic soils and entered the rivulets within the wetland. 3) Deep ground water reached the stream as bed and bank seepage. Springs were higher in nitrate and chloride than rivulets entering the stream, whereas bank seeps had lower concentrations of nitrate and chloride and considerably higher ammonium concentrations than the rivulets. These contrasts in nitrate and chloride concentrations were related to initial differences in the ion chemistry of shallow and deep ground water rather than to element transformations within the riparian wetland. Differences in ammonium concentration between seeps and rivulets were caused by immobilization of ammonium in the substrates of aerobic rivulets, whereas little ammonium depletion probably occurred in deep ground water flowing upward through reduced subsurface organic soils around the stream perimeter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00018968
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Nitrogen dynamics of storm runoff in the riparian zone of a forested watershed (1993)
    Springer
    Biogeochemistry 20 (1993), S. 19-44 
    Details
    ISSN: 1573-515X
    Keywords: ammonium ; nitrate ; riparian zone ; stream chemistry ; storm runoff ; swamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The influence of storm runoff processes on stream nitrogen dynamics was investigated in a headwater riparian swamp on the Oak Ridges moraine in southern Ontario. Hydrologic data were combined with analysis of an isotopic tracer (180) and nitrogen (NH 4 + , NO 3 − ) concentrations in saturation overland flow and stream discharge. Storm runoff was separated into its event and pre-event components using18O in order to examine the effect of water source on nitrogen chemistry. Laboratory experiments were also used to study nitrogen transformation associated with storm runoff-surface substrate interactions in the swamp. In most storms N03-N and NH4-N concentrations in the initial 3–4 mm throughfall increment were 10–20x and 20–100x higher respectively than stream base flow concentrations. Maximum stream N03-N concentrations were 〈 2x to 6x higher than base flow concentrations and preceded or coincided with peak stream discharge. Storm-to-storm variations in stream N03-N behaviour also occurred during the hydrograph recession phase. NH4-N concentrations attained an initial peak on the rising hydrograph limb, or at peak stream discharge. A second NH4-N increase occurred during the late recession phase 3–5 h after maximum stream discharge. Inorganic-N concentrations in surface runoff were similar to peak streamflow. The close agreement between observed N03-N concentrations and values predicted from a chemical mixing model indicate that stream N03-N variations were controlled mainly by the mixture of throughfall and groundwater in surface stormflow from the swamp. Laboratory experiments also indicated that N03-N in surface runoff behaved conservatively when mixed with swamp substrates. With the exception of the late hydrograph recession phase, observed stream NH4-N concentrations were much lower than concentrations predicted by the chemical mixing model. The rapid loss of NH4-N from mixtures of surface stormflow and swamp substrates in laboratory experiments and the absence of uptake in sterilized substrates indicated that NH4-N retention in surface storm runoff was due to biotic processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00002804
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Subsurface denitrification in a forest riparianzone: Interactions between hydrology and supplies ofnitrate and organic carbon (2000)
    Springer
    Biogeochemistry 51 (2000), S. 193-223 
    Details
    ISSN: 1573-515X
    Keywords: denitrification ; groundwater ; nitrate ; organic carbon ; riparian zone ; sand aquifer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The influence of hydrology andpatterns of supply of electron donors and acceptors onsubsurface denitrification was studied in a forestriparian zone along the Boyne River in southernOntario that received high nitrogen inputs from a sandaquifer. Two hypotheses were tested: (1) subsurfacedenitrification is restricted to localized zones ofhigh activity; (2) denitrification zones occur atsites where groundwater flow paths transportNO3 − to supplies of available organiccarbon. A plume of nitrate-rich groundwater withconcentrations of 10–30 mg N L−1 flowed laterallyat depths of 1.5–5 m in sands beneath peat for ahorizontal distance of 100–140 m across the riparianzone to within 30–50 m of the river. In situ acetyleneinjections to piezometers revealed that significantdenitrification was restricted to a narrow zone ofsteep NO3 − and N2O decline at theplume margins. The location of these denitrificationsites in areas with steep gradients of groundwater DOCincrease supported hypothesis 2. Many of thesedenitrification “hotspots” occurred near interfacesbetween sands and either peats or buried river channeldeposits. Field experiments involving in situadditions of either glucose or NO3 − topiezometers indicated that denitrification wasC-limited in a large subsurface area of the riparianzone, and became N-limited beyond the narrow zone ofNO3 − consumption. These data suggest thatdenitrification may not effectively removeNO3 − from groundwater transported at depththrough permeable riparian sediments unlessinteraction occurs with localized supplies of organicmatter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006476514038
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Hyporheic zone hydrology and nitrogen dynamics in relation to the streambed topography of a N-rich stream (1998)
    Springer
    Biogeochemistry 42 (1998), S. 285-310 
    Details
    ISSN: 1573-515X
    Keywords: ammonium ; groundwater ; hydrologic exchange ; hyporheic zone ; nitrate ; streams
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The influence of riffle-pool units on hyporheic zone hydrology and nitrogen dynamics was investigated in Brougham Creek, a N-rich agricultural stream in Ontario, Canada. Subsurface hydraulic gradients, differences in background stream and groundwater concentrations of conservative ions, and the movement of a bromide tracer indicated the downwelling of stream water at the head of riffles and upwelling in riffle-pool transitions under base flow conditions. Channel water also flowed laterally into the floodplain at the upstream end of riffles and followed a subsurface concentric flow path for distances of up to 20 m before returning to the stream at the transition from riffles to pools. Differences in observed vs predicted concentrations based on background chloride patterns indicated that the hyporheic zone was a sink for nitrate and a source for ammonium. The removal of nitrate in the streambed was confirmed by the loss of nitrate in relation to co-injected bromide in areas of downwelling stream water in two riffles. Average stream water nitrate-N concentrations of 1.0 mg/L were often depleted to 〈0.005 mg/L near the sediment-water interface. Consequently, an extensive volume of the hyporheic zone in the streambed and floodplain had a large unused potential for nitrate removal. Conceptual models based mainly on studies of streams with low nutrient concentrations have emphasized the extent of surface-subsurface exchanges and water residence times in the hyporheic zone as important controls on stream nutrient retention. In contrast, we suggest that nitrate retention in N-rich streams is influenced more by the size of surface water storage zones which increase the residence time of channel water in contact with the major sites of rapid nitrate depletion adjacent to the sediment-water interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005932528748
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    A cleanup technique for samples containing high-level interferences prior to ion chromatographic analysis (1983)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 6 (1983), S. 275-277 
    Details
    ISSN: 0935-6304
    Keywords: Ion chromatography ; Low level ions detectable in highly caustic solutions ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240060511
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Halogenated compound response in an oxygen doped ion mobility detector for capillary gas chromatography (1983)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 6 (1983), S. 4-10 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Ion mobility detector ; Plasma chromatography ; Selective detection ; Quantitative analysis ; Halogenated compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An ion mobility detector that has been specifically developed for interfacing with capillary gas chromatography is investigated in the negative ion mode. Like the electron capture detector, to which this instrument is closely related, the ion mobility detector shows an enhanced response to low molecular weight halogenated compounds when a small quantity of oxygen is doped into the make-up gas flow. Under O2 doping conditions, the device can operate in a reactant ion monitoring mode responding universally to compounds capable of capturing thermal electrons and in a tunable selective product ion mode providing increased selectivity over that achieved by the ECD. At an oxygen concentration of 0.5%, minimum detectable amounts as low as 600 femtograms have been realized for carbon tetrachloride. Selectivity of chloro- versus bromo- compounds is demonstrated using a mixture of p-dichlorobenzene and p-dibromobenzene.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240060102
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Ion mobility detection after supercritical fluid chromatography (1986)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 154-160 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography ; Ion mobility detection ; Tunable, selective detection ; Fourier transform-ion mobility spectrometry ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a unidirectional flow ion mobility detector, non-selective detection, tunable selective detection, and complete Fourier transformed ion mobility spectra were successfully obtained after supercritical fluid chromatography on compounds with higher molecular weights than have been previously investigated. In the most selective mode, single oligomers from polymeric material could be independently detected. Using the Fourier transform capabilities of this instrument, complete ion mobility spectra for each oligomer could be obtained in a single chromatographic separation. The collection of individual ion mobility spectra of the components of polymeric material has not been possible prior to the technique described in this paper. Only complex ion mobility spectra of polymeric mixtures are available in the literature. The spectra obtained in this study are all simple, uncomplicated spectra consisting of only one or two product ion peaks. Ko values reported in this work range from 0.633 to 1.61, which are some of the lowest values ever reported in ion mobility spectrometry.With the unidirectional flow design of the detector, the supercritical fluid mobile phase, carbon dioxide, was efficiently eliminated from the detector so that the ion mobility spectrometer could be operated in its normal manner. The fact that CO2 did not interfere with normal ion mobility operation indicates that other supercritical fluids may also be compatible with this sensitive and versatile detection method.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240090305
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    A rapid isocratic HPLC procedure for the determination of urinary porphyrins (1980)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 3 (1980), S. 588-588 
    Details
    ISSN: 0935-6304
    Keywords: Urinary porphyrins ; Isocratic ; HPLC ; Fluorescence ; Riboflavin ; μBondapak Phenyl ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240031110
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...