Endre søk
RefereraExporteraLink to record
Permanent link

Direct link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Seasonal turnover in groundwater
Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
2005 (engelsk)Licentiatavhandling, med artikler (Annet vitenskapelig)
Abstract [en]

This Licentiate Thesis presents a new approach of understanding leakage in agricultural land. Former studies concentrate on long term measurement of different pollutants in nearby watercourses and streams. The new approach is so far only numerically performed, but will soon be complemented by laboratory tests and field measurements. Our hypothesis is that nutrient leakage into groundwater is caused by thermally driven groundwater convection. The maximum density of water occurs at a temperature of near 4oC. Thus, a density increase of the groundwater occurs by heating from about 0oC in the north of Sweden (springtime) and by cooling from about 10oC in the south (autumn). The depth of the convection (leakage) depends on the size of the thermal gradient. This hypothesis consequently explains both why the nutrient leakage occurs during different seasons in the north and south of Sweden and also why the leakage reaches greater depths in the south. The numerical results show that convection is induced by a small horizontal groundwater flow. In the south of Sweden the lowest required permeability for convection to occur was K=6.7∙10-10m2. In this soil the convection cells reached to a maximum depth of 6 meters. The Rayleigh number (Ra) could be as low as 19 for convection to occur, the general critical Ra is 40 in porous media. In northern Sweden a permeability of K=6.1∙10-92 was required. In this soil and climate convection occurred to depths from 0.2 to 0.9 meters. Transient solutions showed that the required time for the convection pattern to fully develop was 22 days. The effect of frost lenses on the groundwater convection was also studied. Small lenses changed the convection rolls slightly, while large obstacles forced the convection rolls to change size and shape. The simulations showed that the required grain size for convection to occur was considerably greater than the grain size in typical agricultural soils. Still vertical groundwater movements exist. Other possible explanations to groundwater convection in agricultural soil in northern Sweden are to be investigated. Unstable groundwater convection or oscillating convection cells, infiltration of rain and melt water, pressure induced convection and the possibility that Coriolis force due to Earth´s rotation could cause secondary currents in groundwater flow.

sted, utgiver, år, opplag, sider
Luleå: Luleå tekniska universitet, 2005. , s. 31
Serie
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757 ; 2005:15
HSV kategori
Forskningsprogram
VA-teknik
Identifikatorer
URN: urn:nbn:se:ltu:diva-26664Lokal ID: f6495a10-9a38-11db-8975-000ea68e967bOAI: oai:DiVA.org:ltu-26664DiVA, id: diva2:999831
Merknad
Godkänd; 2005; 20070102 (haneit)Tilgjengelig fra: 2016-09-30 Laget: 2016-09-30 Sist oppdatert: 2017-11-24bibliografisk kontrollert

Open Access i DiVA

fulltekst(700 kB)53 nedlastinger
Filinformasjon
Fil FULLTEXT01.pdfFilstørrelse 700 kBChecksum SHA-512
686d0a91540db4b9437866c3dc9783ba57191e3296fa2390a25d9623697c10354f3aeecb7f5f37a827047d13bd599ad0d0f9fbbed109fb6dab83fd69d7cce47a
Type fulltextMimetype application/pdf

Personposter BETA

Engström, Maria

Søk i DiVA

Av forfatter/redaktør
Engström, Maria
Av organisasjonen

Søk utenfor DiVA

GoogleGoogle Scholar
Totalt: 53 nedlastinger
Antall nedlastinger er summen av alle nedlastinger av alle fulltekster. Det kan for eksempel være tidligere versjoner som er ikke lenger tilgjengelige

urn-nbn

Altmetric

urn-nbn
Totalt: 144 treff
RefereraExporteraLink to record
Permanent link

Direct link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf