Variability and relationships between Pb, Cu, and Zn concentrations in soil solutions and forest floor leachates at heavily polluted sites

Abstract

AbstractSeasonal variability of Cu, Pb, and Zn concentrations in litter leachates and soil solutions was examined in an afforested zone surrounding a copper smelter in SW Poland. Litter leachates (with zero‐tension lysimeters) and soil solutions (with MacroRhizon suction‐cup samplers, installed at a depth of 25–30 cm) were collected monthly at three sites differing in contamination levels in the years 2009 and 2010 (total Cu: 2380, 439, and 200 mg kg–1, respectively). Concentrations of Cu in the litter leachate were correlated with dissolved organic C (DOC), whereas Zn and Pb were mainly related to leachate pH. Metal concentrations in the soil solution were weakly influenced by their total content in soils and the monthly fluctuations reached 300, 600, and 700% for Cu, Pb, and Zn, respectively. Metal concentrations in soil solutions (Cu 110–460 μg L–1; Zn 20–1190 μg L–1; Pb 0.5–36 μg L–1) were correlated with their contents in the litter leachates. Chemical speciation, using Visual Minteq 3.0, proved organically‐complexed forms even though the correlations between metal concentrations and soil solution pH and DOC were statistically insignificant. The flux of organically‐complexed metals from contaminated forest floors is believed to be a direct and crucial factor affecting the actual heavy metal concentrations and their forms in the soil solutions of the upper mineral soil horizons.