Abstract
Intensified vehicular traffic causes increased heavy metal contamination of the environment. We investigated the heavy metal chemistry of soils located under silver fir stands in the vicinity of Poland’s S7 roadway. Three sampling sites were located in fir stands in central Poland. Fieldwork included soil sampling of the organic (O) horizon and mineral (A) topsoil. We analyzed the soil pH, carbon (C) and nitrogen (N) concentration, and the HCl-extractable forms of sodium (Na) and heavy metals: copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn). The stoichiometric ratios Cu:C, Ni:C, Pb:C, and Zn:C were also calculated. In all sites, a higher Na concentration was found in the 0–10 m from the forest edge. This zone was characterized by increased pH in the O horizon, increased Zn and Ni in the A horizon, and a decreased Pb in the O horizon. There was no clear pattern for the Cu concentration. The Ni:C and Zn:C ratios were correlated with pH, while Pb:C and Cu:C ratios were correlated with the clay minerals. HCl-extractable Ni and Zn concentrations in A horizon were greater near the roadway, revealing strong pH dependency. The roadway affects the geochemical background of the topsoil in the nearby fir stands. Mechanistically, we suggest that Na increases the soil pH and therefore enhances the ability of soil organic matter to bind Ni and Zn by releasing hydrogen from soil organic matter functional groups into the soil solution. A depleted Pb near the road was likely owing to the strong competition from Na.
Highlights
Progressive economic development led to an enlarged road network and intensified road transport
We suggest that Na increases the soil pH and enhances the ability of soil organic matter to bind Ni and Zn by releasing hydrogen from soil organic matter functional groups into the soil solution
Since roadways traverse a large area of forest soils, the aim of this study was to investigate an important effect of roadway vicinity on adsorption of metals, including selected heavy metals, to soil organic matter (SOM)
Summary
Progressive economic development led to an enlarged road network and intensified road transport. These increases have had a considerable impact on the natural environment, causing numerous ecological effects, e.g., loss of habitat, runoff emissions, and increased plant mortality (Spellberg, 1998). A severe consequence of the growing vehicular traffic is the increasing amount of heavy metal contamination in the environment. Heavy metals can enter the food chain, posing a real threat to humans, plants, and animals (Chrzan, 2013; Viard et al, 2004; Ward et al, 1974). Traffic is considered to be the main source of heavy metals in the atmosphere (Zereini et al, 2005).
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