THE EFFECTS OF DEICING SALTS ON WATER CHEMISTRY AND VEGETATION IN PINHOOK BOG, INDIANA
Abstract
An uncovered NaCl road-salt storage pile was established adjacent to Interstate 80/90 in 1963, on an embankment above Pinhook Bog, LaPorte Co., Indiana. Following construction of a protective dome over the pile in 1972, salt-laden runoff from the highway continued to be diverted into the bog watershed. The input of NaCl into the bog was accompanied by alterations of the vegetation in a 2 ha area, including death of native species and invasion of non-native species. A study was conducted in 1979-81 to identify the effects of the salt intrusion on water chemistry and vegetation in the bog, and to determine the fate of the salt and any resulting yearly changes in water chemistry or vegetation patterns. Stratigraphic mapping of portions of Pinhook Bog identified a clay-lined basin that could serve to isolate the bog waters from the influence of regional groundwater. Water chemistry determinations from unimpacted portions of the bog also indicated the presence of ombrotrophic conditions. The impacted area showed salt concentrations as high as 468 mg/l and 1215 mg/l Cl within the plant root zone of the peat mat. The pattern of elevated salt concentrations corresponded to the pattern of altered vegetation. The salt concentrations in the root zone decreased significantly each year from 1979 to 1981 throughout the impacted area. Analysis of salt movements suggested that the salt was transported vertically downward by water movement through the peat mat following snow-melt and heavy precipitation events each spring. Vegetation surveys in 1980 showed an absence of numerous native species such as Sphagnum spp. and Larix laricina in the salt-impacted area; they were replaced by invading species such as Typha angustifolia. By 1981, many extirpated species had become reestablished in the impacted area following declines in salt concentrations. The most significant vegetation change was the reappearance of Sphagnum throughout much of the impacted area. Salt tolerance studies on Sphagnum recurvum showed reduced growth in length at NaCl concentrations found in the bog. Encrustation of salt on plant tips through evapotranspirational processes was shown to be a possible mechanism for salt-induced Sphagnum mortality.
Degree
Ph.D.
Subject Area
Ecology
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