Emerging indirect and long‐term road salt effects on ecosystems

Abstract

Widespread use of salts as deicing agents on roads has been perceived as a significant source of environmental and economic damage. Early studies focused on near-road and short-term effects where concentrations can exceed several grams per liter. Evidence is accumulating that the use of salts has significant effects over broader areas, longer time frames, and is affecting a range of ecological processes. Concentrations of NaCl can be elevated throughout an ecosystem to >100 mg Cl(-) /L, which may have nonlethal and possibly subtle effects on sensitive life stages of several organisms. NaCl seems subject to retention within terrestrial and aquatic ecosystems, thus prolonging the actual duration of exposure and leading to elevated warm-season concentrations when reproduction may be occurring or other sensitive life stages are present. Many of the alternatives to NaCl reduce some of these negative effects, although are currently cost prohibitive for large-scale use. Some techniques for managing application rates are improvements in technology, while others involve novel mixtures of organic compounds that may have new environmental consequences. The increasing evidence of these widespread and persistent environmental consequences must be brought into decisions on deicing procedures.

Anthropogenic changes in sodium affect neural and muscle development in butterflies

“…However, sodium availability is limited in most ecosystems (17)(18)(19), which is thought to have led to the evolution of sodium cravings (20,21) and specific foraging behavior to acquire sodium (22)(23)(24)(25). Humans are increasing sodium availability, particularly through the application of road salt (26)(27)(28)(29) but also, through agricultural activity (30). In the metropolitan area of Minneapolis and St. Paul, Minnesota, ∼300,000 tons of sodium chloride are applied to roads each winter (31).…”

Salinization alters fluxes of bioreactive elements from stream ecosystems across land use

“…Relative to the proteinaceous materials, humic substances are larger hydrophobic molecules occurring in the colloidal size range (e.g., Aiken et al, 1985). This DOC fraction is readily subjected to flocculation (e.g., Sholkovit, 1976), sorption to mineral surfaces (Fox, 1991;Hedges and Keil, 1999), and pH suppression (Kipton et al, 1992;Li et al, 2007Li et al, , 2013) with increasing ionic strength or salinization. The potential instability of the humic-like DOC fraction upon salinization was further supported by our present results and previous studies (e.g., Li et al, 2013), which showed that salinization consistently decreased SUVA of DOC released from soils and sediments (Figs.…”

“…Salt concentrations in freshwaters are rapidly increasing at a regional scale in the USA and worldwide (e.g., Nielsen et al, 2003;Kaushal et al, 2005Kaushal et al, , 2014aRengasamy, 2006;Findlay and Kelly, 2011;Steele and Aitkenhead-Peterson, 2011;Corsi et al, 2015). Most of the increased salinization can typically be attributed to road salt deicers and other industrial uses, wastewater discharges, groundwater irrigation, saltwater inundation caused by sea-level rise, and human-accelerated weathering (e.g., Findlay and Kelly, 2011;Aitkenhead-Peterson et al, 2009;Ardón et al, 2013;Kaushal et al, 2013).…”

“…Evidence is accumulating that increased salinization is an important process during the urban evolution of geochemical cycles in watersheds globally from decades to centuries (Kaushal et al, , 2015. Furthermore, salinization has significant ecosystem effects over broader spatial and temporal scales (e.g., Findlay and Kelly, 2011;Kaushal and Belt, 2012;Corsi et al, 2015).…”

“…Most of the increased salinization can typically be attributed to road salt deicers and other industrial uses, wastewater discharges, groundwater irrigation, saltwater inundation caused by sea-level rise, and human-accelerated weathering (e.g., Findlay and Kelly, 2011;Aitkenhead-Peterson et al, 2009;Ardón et al, 2013;Kaushal et al, 2013). Increased salinization can have important environmental consequences for drinking water supplies, freshwater biodiversity, degradation of soils and groundwater, degradation of vehicles and infrastructure, and mobilization of inorganic and organic contaminants (Nielson et al, 2003;Kaushal et al, 2005;Findlay and Kelly, 2011;Corsi et al, 2015). Moreover, salinization is difficult if not impossible to reverse and, thus, remediation is unlikely.…”