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https://nap.nationalacademies.org/catalog/27432/critical-issues-in-transportation-for-2024-and-beyond

EFFECTS OF DE-ICING SALTS ON ROADSIDE SOILS AND VEGETATION

THE PURPOSE OF THIS INVESTIGATION IS TO DETERMINE THE DISTRIBUTION AND MOVEMENT OF DEICING SALT IONS IN SOIL BORDERING THE HIGHWAY AT A SITE 5 MILES SOUTH OF SHELBURNE, VERMONT, ON US-7, AND TO DETERMINE THE POSSIBLE ROLE OF THESE SALTS IN CAUSING AN EXTENSIVE SILVER MAPLE DECLINE. THE STUDY INDICATES THAT HIGHWAY SALTING PRACTICES HAVE INCREASED THE SODIUM AND CHLORINE CONCENTRATIONS AND THE SPECIFIC CONDUCTANCE IN THE SOIL. THIS IS MANIFESTED IN AN EXTENSIVE SILVER MAPLE DECLINE ON THE EAST SIDE OF THE ROAD, WHILE HEALTHY TREES GROW ON THE WEST SIDE OF THE ROAD WHERE, DUE TO THE SLOPE, HIGHWAY DRAINAGE IS LIMITED. THE MAXIMUM CONCENTRATIONS OF SODIUM AND CHLORIDE ARE FOUND AT THE SOIL SURFACE AND NEAREST THE HIGHWAY PAVEMENT. SALT CONCENTRATIONS IN THE SOIL INCREASE DURING THE WINTER AND DECREASES DURING SUMMER AND FALL. SODIUM AND CHLORIDE IONS ENTER THE SOIL PROFILE DURING THE WINTER AND PENETRATE INTO DEEPER HORIZONS AS TIME PROGRESSES. HIGHER THAN NORMAL SODIUM AND CHLORIDE CONCENTRATIONS ARE FOUND TO DEPTHS OF 18 IN. AND DISTANCE OF 75 FT FROM THE PAVEMENT. AS THE YEARS PASS THE QUANTITY OF SODIUM AND CHLORIDE INCREASES THROUGHOUT THE ENTIRE SOIL PROFILE. THE PASSAGE OF SALT THROUGH SOIL PROFILES IS SUSPECTED TO CAUSE A DETERIORATION OF THE SOIL'S PHYSICAL PROPERTIES, THEREBY CAUSING A DECREASE IN SOIL PERMEABILITY. THE INCREASE IN SODIUM AND CHLORIDE CONTENT OF THE SOIL SOLUTION IS MANIFESTED THROUGH INCREASED UPTAKE OF THESE IONS INTO THE LEAVES AND STEMS OF THE DAMAGED TREES. DETERIORATION OF THE SILVER MAPLES RESULTED FROM CHLORIDE TOXICITY RATHER THAN FROM OSMOTIC EFFECT OF THE SALTS IN SOIL SOLUTION. NO DAMAGE IS OBSERVED WHEN THE CHLORIDE CONCENTRATION IS LESS THAN 0.18 PERCENT. A CHLORIDE CONCENTRATION OF 0.20 PERCENT PRODUCES LEAF SCORCH, AND ABOVE 0.50 PERCENT PRODUCES MODERATE LEAF SCORCH, DEFOLIATION, AND ULTIMATELY DEATH OF THE TREE. THE SODIUM CONCENTRATION IS MUCH HIGHER IN THE DAMAGED THAN IN THE HEALTHY TREES AND MAY BE A REASON FOR THE OVER-ALL DETERIORATION. HOWEVER, IT IS NOT TOTALLY RESPONSIBLE, AS HIGH CONCENTRATIONS OF SODIUM ARE SOMETIMES RECOVERED IN TREES EXHIBITING NO SALT DAMAGE WHEN DEATH OCCURS. CHLORIDE AND SODIUM ARE LOST FROM THE WOODY TISSUE. THEREFORE, TISSUE ANALYSIS OF A DEAD OR DYING TREE MAY FAIL TO REVEAL LARGE QUANTITIES OF THESE IONS. THE EFFECT OF SALT SPRAY APPEARS NEGLIGIBLE. THOUGH DEICING SALTS ARE DETRIMENTAL TO ROADSIDE VEGETATION, PUBLIC SAFETY DEMANDS THEIR USE, THEREFORE IT IS RECOMMENDED THAT WOODY VEGETATION BE LOCATED AS FAR FROM THE HIGHWAY AS PRACTICABLE WITH PAVEMENT DRAINAGE DIRECTED AWAY FROM THE TREES; ALSO THE SPECIES SHOULD BE CHOSEN ON THE BASIS OF SALT TOLERANCE.

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  • Supplemental Notes:
    • Paper sponsored by Committee on Roadside Development and presented at the 49th Annual Meeting. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved.
  • Authors:
    • Zelazny, L W
    • Hanes, R E
    • Blaser, R E
  • Publication Date: 1970

Media Info

  • Media Type: Digital/other
  • Features: Tables;
  • Pagination: pp 9-12
  • Monograph Title: Roadside development and maintenance
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00218739
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Jun 1 1971 12:00AM