Library

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
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Aqueous geochemical data from unconfined sand aquifers beneath two operating domestic septic systems are used to illustrate and evaluate a conceptual model of septic-system geochemistry. This model emphasizes the changing redox and alkalinity conditions in the septic system and the subsurface. The septic-tank effluents flow as distinct plumes downward through the unsaturated zones and then primarily laterally in the ground-water zones. The composition of the effluent was measured at several points in each system. At each site, the septic-tank effluent underwent aerobic oxidation in the unsaturated zone, which caused conversion of NH4+ to NO3−, organic C to CO2 and organic S to SCh42-. At the first site, calcium carbonate dissolution in the unsaturated zone buffered the acidity released by the redox reactions. In contrast, the second system was poorly buffered and the pH dropped from 6.7 to 4.9 as aerobic oxidation occurred. Below the water table a small amount of aerobic oxidation occurred at each site. Nitrate-N concentrations in the cores of both plumes were above 25 mg/1 as the plumes traveled from the septic systems. At the second site, the ground-water plume discharges to a river at the edge of the property. As the effluent flowed through the organic C-rich sediments of the river bed, NO3− disappeared and alkalinity increased, presumably due to denitrification. Differences in sediment composition at the two sites also led to different behaviors of Fe, Al, and possibly PO43-. The conceptual model offers an organized approach to interpreting the major geochemical trends observed in the two systems, which are determined mostly by the well-aerated unsaturated zones below the drain fields and the amount of buffering material present in the sediments.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 32 (1994), S. 0 
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: This paper presents a conceptual model, developed by synthesizing the results of many researchers, which describes the geochemical evolution of domestic waste water in conventional on-site septic systems as the result of the interactions of a few major constituents. As described by the model, the evolution of waste water is driven by the microbially catalyzed redox reactions involving organic C and N in waste water and occurs in as many as three different redox zones. Anaerobic digestion of organic matter and production of CO2, CH4, and NH4+ predominate in the first zone, which consists mainly of the septic tank. In the second zone, gaseous diffusion through the unsaturated sediments of the drain field supplies O2 for aerobic oxidation of organic C and NH4+ and a consequent decrease in waste-water alkalinity. The NO3− formed by NH4+ oxidation in this zone is the primary adverse impact of septic systems at most sites and is generally an unavoidable consequence of the proper functioning of conventional septic systems. If adequate O2 is not available in the drain field, aerobic digestion is incomplete, and the accumulation of organic matter may cause septic-system failure. In the third redox zone, NO3 is reduced to N2 by the anaerobic process of denitrification. However, this setting is rarely found below septic systems due to a lack of labile organic C in the natural setting. Consideration of the changing redox and pH conditions in each zone aids our understanding of the fate of other constituents in septic systems.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A method that accurately and precisely yields hydrogen-ion activity is needed for the following reasons: (1) Aquatic biota are sensitive to hydrogen-ion activity. Most laboratory bioassay experiments refer to changes in, for example, quantity, distribution and viability of a given species as a ...
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1573-1480
    Keywords: wetlands ; forested catchments ; dissolved organic carbon ; carbon cycling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Most Precambrian Shield forested catchments have some wetland component. Even small riparian wetlands are important modifiers of stream chemistry. Dissolved organic matter (DOM) is one of the most important products exported by wetlands in streams. Stratigraphic control of hydraulic conductivity generally leads to decreasing conductivity with depth. Thus important flowpaths occur in the uppermost organic rich layers and are reflected in chemical profiles of dissolved organic carbon (DOC). Accumulation of DOC in peat porewaters is the net effect of production, consumption and transport. DOC profiles vary with degree of interaction with the surrounding upland catchment and distance from the edge of the wetland as well as internal processes within the wetland. In wetlands, DOM production is offset by flushing resulting in decreasing DOC concentrations with increasing flows. Despite old carbon (2,000 to 3,000 years) at relatively shallow depths, 14C activity in DOC exported from wetlands is mostly modern (recent carbon), consistent with shallow flowpaths and export of DOM from shallow organic rich horizons. In contrast, the source area for DOM in upland catchments with developed B horizon soils increases with antecedent soil moisture conditions resulting in increasing DOC concentrations with higher stream flows. Activity of 14C in stream DOC from upland catchments span a range from low activities (older carbon) similar to B horizon soil water during dry moisture conditions to values slightly less than modern (more recent carbon) during high moisture conditions. The more modern carbon activities reflect the increased contribution of the organic rich litter and A horizon soil layers in the area immediately bordering the stream under wet antecedent moisture conditions. Reduced hydrologic export or loss of wetlands under drier climatic conditions may result in in larger fluctuations in stream DOC concentrations and reduced DOM loads to lakes.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1435-0629
    Keywords: Key words: Boreal forest; nitrogen saturation; whole-catchment manipulation; nitrogen export.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: ABSTRACT Boreal Shield rocky ridges at the Experimental Lakes Area, northwestern Ontario, contain two plant/soil communities with contrasting N cycles. Picea mariana–Pinus banksiana”forest islands” are N limited whereas the lichen, moss, and grass community (or “lichen patches”) on the surrounding bedrock outcrops appear intrinsically N saturated. The potential for this landscape to retain a N input of eightfold ambient levels was tested with a 2-y addition of 40 kg N ha-1 y-1 as NaNO3 to one small catchment (0.40 ha). The elevated N input was poorly retained by the whole catchment during snowmelt. However, during the growing season, N retention in the treated catchment remained as efficient as in references. Forest islands and bedrock surfaces responded in opposite fashions to the elevated N input. By the second year of N addition, bedrock surfaces no longer retained additional N inputs. In contrast, N-amended and reference forest islands retained a similar proportion of N inputs, indicating that forest islands did not become N saturated. The response of the whole catchment to N addition was more similar to forest islands than bedrock surfaces. Even if forest islands only cover a small proportion of catchment area, they can have a strong impact on whole catchment element export because most of the water must move through at least one island before leaving the system. Because the different components of the boreal shield landscape are hydrologically connected, N saturation may occur as a cascading effect in this ecosystem. Monitoring boreal shield landscapes by using outlets at the lower end of the hydrological cascade can fail to detect the impacts of perturbations such as increased N deposition on upper components.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1573-515X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The chemical relationships among particulate and colloidal organicmaterial and dissolved fulvic acid were examined in an alpine andsubalpine lake and two streams in Loch Vale Watershed, Rocky MountainNational Park. The alpine lake, Sky Pond, had the lowest dissolved organiccarbon (DOC) (0.37 mgC/L), the highest particulate carbon (POC) (0.13mgC/L), and high algal biomass. The watershed of Sky Pond is primarilytalus slope, and DOC and POC may be autochthonous. Both Andrews Creekand Icy Brook gain DOC as they flow through wet sedge meadows. Thesubalpine lake, The Loch, receives additional organic material from thesurrounding forest and had a higher DOC (0.66 mgC/L). Elemental analysis,stable carbon isotopic compositon, and 13C-NMR characterizationshowed that: 1) particulate material had relatively high inorganic contentsand was heterogeneous in compositon, 2) colloidal material was primarilycarbohydrate material with a low inorganic content at all sites; and 3)dissolved fulvic acid varied in compositon among sites. The lowconcentration and carbohydrate-rich character of the colloidal materialsuggests that this fraction is labile to microbial degradation and may beturning over more rapidly than particulate fractions or dissolved fulvic acid.Fulvic acid from Andrews Creek had the lowest N content and aromaticity,whereas Sky Pond fulvic acid had a higher N content and lower aromaticitythan fulvic acid from The Loch. The UV-visible spectra of the fulvic acidsdemonstrate that variation in characteristics with sources of organic carboncan explain to some extent the observed non-linear relationship betweenUV-B extinction coefficients and DOC concentrations in lakes.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...