Effects of Deicing‐Salts on Heavy Metal Mobility Zum Einfluß von Streusalzen auf die Beweglichkeit von Schwermetallen

Abstract

Heavy metal input into roadside soils and effects of deicing salts are often discussed as separate environmental problems. However, a relationship between salt input and heavy metal mobility has already been detected in laboratory tests. During a 2-year field study, the soil solution of a roadside soil was continuously sampled. The results of soil solution analysis not only showed a strong rise in deicing-salt related sodium, calcium and chloride concentrations, but also high zinc and cadmium values in winter and spring. Additional laboratory tests confirmed the mobilizing effects of salt solution which contained NaCl and CaC12. Cation exchange and the formation of chlorocomplexes are discussed as the responsible mechanisms. ~~~~ ~ Schlagworter: StraBenrandboden, Streusalze, Schwermetalle, Mobilisierung, Bodenlosung, Cadmium, Zink Zusammenfassung: Bisher galten Streusalzbelastung und Schwermetalleintrag in StraBenrandboden als voneinander unabhangige Arten der Umweltbelastung. Jedoch konnten bereits in Laborversuchen Zusammenhange zwischen Salzeintrag und Schwermetallmobilisierung festgestellt werden. Im Rahmen einer etwa zweijahrigen Untersuchung wurde kontinuierlich die Bodenlosung am Rande einer Autobahn untersucht. Die Ergebnisse zeigten im Winter und Friihjahr nicht nur eine starke, streusalzbedingte Zunahme der Natrium-, Calcium-und Chloridkonzentrationen, sondern auch einen deutlichen Anstieg der Cadmium-und Zinkgehalte in der Bodenlosung. Erganzende Laborversuche bestatigten die mobilisierende Wirkung einer aus NaCl und CaC12 zusammengesetzten Streusalzlosung. Als verantwortlicher bodenchemischer Mechanismus wird Kationenaustausch und Chlorokomplexbildung diskutiert. ~ ~~ Acta hydrochun. hydrobiol. 21 (1993) 1, m-m 0 VCH Verlagsgesellschaft mbH, D-6940 Weinhem 1993 0323-4320/93/0104-0038 $ 05.00+.25/0 m Ada hydrochim. hydrobiol. 21 (1993) 1 -11, Technisch-Inhondelijk Deel-Afl.4.-'s-Gravenhage: Sdu uitgeverij. Netherlands, 1988.

Simultaneous Adsorption of Heavy Metals from Roadway Stormwater Runoff Using Different Filter Media in Column Studies

“…In column study, Norrström [28] demonstrated that a large part of Pb, Cd and Zn in highway roadside soils are vulnerable to leaching when exposed to a high NaCl (5.84 g/L) concentration. From field studies, Bauske and Goetz [29] also found a strong effect of NaCl solution on Cd and Zn. Additionally, studies have been conducted to examine the remobilization of heavy metals adsorbed onto filter materials used for stormwater treatment [6,25].…”

“…Increased mobility of heavy metals coincident with road salt applications have been observed in road side soils and filter media used in stormwater filtration systems by various mechanisms, including the competition of salt derived cations with positively charged heavy metal species for sorption sites on the solid phase (ion exchange), lowered pH, formation of chlorocomplexes and possible colloid dispersion [27][28][29]32]. The mobility of heavy metals induced by NaCl application might not behave in the same way.…”

“…Results of both laboratory [6,27,28] and field experiments [29] have demonstrated de-icing road salt indeed has the potential to increase metal mobility of heavy metals previously adsorbed by soil and individual (single) filter media. We hypothesised that application of de-icing road salt (NaCl) can mobilize major parts of heavy metals previously adsorbed by mixed mineral based filter media.…”

Evaluating the Variation of Dissolved Metals on a Highway Roadside Using a Generalized Additive Mixed Model (GAMM)

“…The presence of high Cl concentrations leads to a strong decrease in the adsorption of Cd ions in soils (Doner, 1978;Boekhold et al, 1993;Lumsdon et al, 1995). The strong influence of salt concentration on the mobilization of metals has already been observed by many other authors dealing with the topic of road runoff and roadside soils (e.g., Bauske & Goetz, 1993;Strong, 1990, Amrhein et al, 1992;Bäckström et al, 2004, Ramakrishna andViraraghavan, 2005). Li et al (2015) determined an extensive mobilization of Cd soil leachate by salts, accounting for about 21% of the total Cd in the soil.…”

“…Li et al (2015) determined an extensive mobilization of Cd soil leachate by salts, accounting for about 21% of the total Cd in the soil. Bauske & Goetz (1993) examined concentrations of Cd and Zn that had increased by a factor of 20 in highway soil solutions during the utilization of de-icing salts in winter. Salimi et al (2015) found that the Cl-ion formed complex ions with Cd to CdCl+, CdCl3-, and CaCl4-.…”