Trace metals in Northern New England streams: Evaluating the role of road salt across broad spatial scales with synoptic snapshots.

Jessica F Wilhelm,Daniel J Bain,Kathleen F Bush,Mark B Green,William H Mcdowell,Fei Li

doi:10.1371/journal.pone.0212011

Abstract

Mobilization of trace metals from soils to surface waters can impact both human and ecosystem health. This study resamples a water sample archive to explore the spatial pattern of streamwater total concentrations of arsenic, cadmium, copper, lead, and zinc and their associations with biogeochemical controls in northern New England. Road deicing appears to result in elevated trace metal concentrations, as trace metal concentrations are strongly related to sodium concentrations and are most elevated when the sodium: chloride ratio is near 1.0 (~halite). Our results are consistent with previous laboratory and field studies that indicate cation exchange as a metal mobilization mechanism when road salt is applied to soils containing metals. This study also documents associations among sodium, chloride, dissolved organic carbon, iron, and metal concentrations, suggesting cation exchange mechanisms related to road deicing are not the only mechanisms that increase trace metal concentrations in surface waters. In addition to cation exchange, this study considers dissolved organic carbon complexation and oxidation-reduction conditions affecting metal mobility from soils in a salt-rich environment. These observations demonstrate that road deicing has the potential to increase streamwater trace metal concentrations across broad spatial scales and increase risks to human and ecosystem health.

Highlights

Salinization of surface waters occurs across seasonally snow-covered areas of the world through the practice of road-deicing [1], and has important consequences for water quality [2,3,4] and aquatic ecosystems [1,5,6]
Dissolved organic carbon was measured with a Shimadzu TOC analyzer, and major ions (Na, K, Mg, Ca, Cl) were measured on a Dionex X2 ion chromatograph at the University of New Hampshire in 2013
Direct comparison of preservation methods demonstrates that the metal concentrations measured in the archived samples are not precisely comparable to the filtered and acidified samples (Fig 5)

Summary

Introduction

Salinization of surface waters occurs across seasonally snow-covered areas of the world through the practice of road-deicing [1], and has important consequences for water quality [2,3,4] and aquatic ecosystems [1,5,6]. Chemical road deicers accumulate in groundwater [7,8], increasing the total concentration of major cations in groundwater throughout the year [9]. Trace metals in Northern New England streams. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Methods

Results

Conclusion