Physical and chemical aspects of water repellent soils affected by slashburning at Vancouver, British Columbia [summary]
Document Type: Journal Article
Author(s): G. Henderson
Publication Year: 1983

Cataloging Information

  • British Columbia
  • Canada
  • chemistry
  • coniferous forests
  • fire management
  • laboratory fires
  • slash
  • soils
  • water
  • water repellent soils
  • watersheds
Record Maintained By:
Record Last Modified: June 1, 2018
FRAMES Record Number: 35572
Tall Timbers Record Number: 9873
TTRS Location Status: In-file
TTRS Call Number: Abstract only
TTRS Abstract Status: Okay, Fair use, Reproduced by permission

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The persistence and severity of water repellency in soils as affected by slashburning was examined in the municipal watersheds of Vancouver by the water drop penetration time (WDPT) and contact angle methods, respectively. Also hydrophobic materials wre extracted from soil, spareated by column adsorption chromatogrtaphy, and analysed for functional groups by IR absorption. Slashburning increased soil water repellency, as indicated by the WDPT method. Precise responses of soil repellency to slashburning were not consistent, as many site specific factors are involved, but increased repellency was evident in soil up to six years following burning. The severity of increased soil repellency caused by slashburning could not be assessed because contact angle determinations using the capillary rise equation and Darcey's Law were not reliable. The WDPT method was more consistent, reliable and simpler than the contact angle method, hence the WDPT method was considered best to indicate the presence of soil water repellency. A combination of polar and non-polar organic solvents, methanol and benzene respectively, extracted hydrophobic compounds from soil. The extractant separated into three fractions, using benzene and incrasing proportions of acetone as eluting agents. Virtually all of the extract (90%) was recovered in fraction I, indicating that the extraction was premoninatly non-polar. Fractions II and III accounted for 4 and 6%, respectively, ofthe applied extractables. Material in all fractions induced repellency in wettable sand when 1mg or more was applied to 5g sand. Repellency was increased by heating the extracted materials in sand to 250°C for 10 min and was eliminated after heating to 300oC in inverse proportion to the mass applied. At 350°C, hydrophobic materials volatized and the sand regained wettability. Analysis by IR absorption of an extraction revealed that hydrophobic substances have hydrophilic and hydrophobic components. Absorption of hydrophobic materials to soil particles is therefore likely initially by the hydrophilic end leaving the hydrophobic end of the organic molecule to form the outer surface, thus preventing water from infiltrating. During slashburns, absorption of hydrophobic materials is probably enhanced by optimization of close range van der Waals and London forces.

Henderson, G. 1983. Physical and chemical aspects of water repellent soils affected by slashburning at Vancouver, British Columbia [summary]. Forestry Abstracts, v. 44, no. 3, p. 214.