Accumulation of deicing salts in soils in an urban environment

Abstract

Examining rates of deicing salt accumulation and leaching in urban soils is important for understanding the distribution and movement of salt in the environment. We examined autumn concentrations of deicing salts in soils in a moderately dense urban landscape in eastern New York State. The study area contrasted to the isolated, rural highways examined in previous studies. While NaCl was the most abundantly applied salt, Mg 2+ (apparently from MgCl 2 , a secondary deicing salt) was the most abundant salt cation in soils. Moderate Na + levels, and equivalent concentrations at depth and in surface samples, indicate that leaching of Na + is rapid in this system. Leaching may ameliorate toxicity for land plants but accelerate inputs to aquatic systems. In contrast to rural highway studies, where salt levels declined rapidly with distance to pavement, Na + remained elevated at the maximum distance measured. Airborne salt dispersal and dense networks of pavement likely contribute to widespread elevated salt levels. This semi-urban setting had salt levels high enough to be toxic to terrestrial plants and soil protozoa. Even moderate levels of development can have dramatic effects on salt inputs into soils and aquatic systems.

The influence of chloride deicers on mineral nutrition and the health status of roadside trees in the city of Kielce, Poland

“…Similarly, low concentrations of this element were also recorded in roadside soils by other authors, for example, 0.03% (Cunningham et al 2008), 0.007-0.035% (Kayama et al 2003), <0.001% (Czerniewska-Kusza et al 2004). Although low concentrations of TOC are typical for urban soils, the decreased contents of organic compounds in the soils studied are a concern.…”

“…The salt transport is the most intensive at a distance of about 10-20 m from the road (McBean and AlNassri 1987;Blomqvist and Johansson 1999). In other studies, on the influence of chemical deicers on urban soils and groundwaters, a downward migration of salts through the soil profile to bedrock has also been confirmed (e.g., Thunqvist 2004;Cunningham et al 2008).…”

“…A long-term use of sodium chloride for winter road maintenance leads to accumulation of sodium and chloride especially in the urban environment (Godwin et al 2003;Ramakrishna and Viraraghavan 2005;Green et al 2008;Cunningham et al 2008). It should be stressed that all the chemical deicers, regardless of their composition, influence the chemistry of waters, soils, and vegetation.…”

“…If these absorbed cations substitute for important plant nutrients, such as Zn, Cu, K, and Mn, this exchange can have a potentially detrimental effect to plant physiology. High concentrations of sodium in soil cause dispersion of soil colloids, leading to reduction in soil permeability and increased erosion rate (Cunningham et al 2008). Accumulation of deicing salts in urban soils may lead to changes in ecological structure of soil organism communities (Green et al 2008) with an increasing population density of salt-tolerant (halophilic) species.…”

“…This complexity is highlighted by indirect (or secondary) effects of pollution on geochemical processes, especially on increasing mobility of heavy metals in soils (Bäckström et al 2004;Norrström and Jacks 1998;Norrström 2005;Rasa et al 2006), selective retention of Na, Ca, and Mg combined with high mobility of chloride ions in soils (Cunningham et al 2008), or disturbance of nitrogen transformations in soils (Green et al 2008). Although the results of comprehensive studies on the influence of road deicers on the environment have been published (e.g., Cekstere et al 2008;Czerniewska-Kusza et al 2004), still little is known on the geochemical behavior of salt constituents in snow-soil-plant systems.…”