1. HEAVY METAL SOLUBILITY AND MOBILITY IN HUMUS LAYERS IMPACTED BY COPPER INDUSTRY IN SOUTH - WEST POLAND
Agnieszka Medyńska-Juraszek, Cezary Kabała
Institute of Soil Sciences and Environmental Protection,
Wroclaw University of Environmental and Life Sciences, Poland
Tabel 1. Average total concentration of the copper, lead, zinc and arsenic and their soluble forms.
INTRODUCTION
Almost 60 years of copper mining and smelting in the south-west part of Poland caused a serious heavy metal pollution of soils in the nearest surrounding. To minimize risk coming from mining and smelting emission protection zones were established in late 70. Trees planted in the nearest surrounding of copper industry objects play a significant role in air cleaning, but the knowledge about the faith of metallurgic dust in this ecosystems is scarce.
The aim of the study was to determine total concentration of heavy metals and arsenic, it’s potential solubility and mobility in humus layers impacted by dusting from a copper smelter and copper ore tailings facility.
METHODOLOGY
The investigation was carried on two study areas. The first was located in former protective zone of copper ore tailings facility, the second in protective zone of copper smelter. On each study site, 3 plots were located. The plots near tailings impoundment were located at the same distance from impoundment, on similar soils (Brunic Arenosols), but under pine stands varying in age, 50 (1 ZM), 18 (2 ZM), 11 (3 ZM) years old. The plots at the Cu smelter were established along increasing distances from the smelter (1 HML), 0.8 (2 HML) and 2.1 km (3 HML) in the poplar stands of the same age. Bulk litter samples was collected during spring/summer/fall season 2009/2010 from four sites, using a steel cylinder (d = 23 cm). In collected samples pH in distilled water and total concentration of copper, lead, zinc and arsenic were analyzed on AAS and ICP MS after digestion in perchloric acid (1:10). Soluble forms of the elements were analyzed after extraction with distilled water and 0,11 M acetic acid (1:40) with AAS and ICP MS technique. Quality of determination has been monitored using soil reference materials (NIST-1515, IAEA-V-10) with certified total concentration of trace elements being analyzed.
*nd – concentration under detection level
RESULTS
Figure 1. Percent of the soluble forms in the total content of the element.
All forest litters under examination have astonishingly high pH values, in a range of alkaline reaction in distilled water and very high total concentrations of calcium and magnesium, up to 3,5 % and 0,9 % of dry litter mass. Such properties of litters are evidences for pollution with alkaline dust emitted by smelter and copper ore tailings impoundment these days or in the recent past. Significant differences in total concentrations of studied elements were found between the sites. Humus layers in a vicinity of copper ore tailings facility were much less polluted with heavy metals than in the surrounding of copper smelter. The highest total concentration of all studied elements were found at the distance of 0,3 km from the smelter (Tab.1). The concentration of studied heavy metals decreased rapidly with a distance from the smelter. Extraction of water extractable forms showed very low solubility of the studied elements. Zinc was the most soluble and mobile element in studied humus layers (Fig.1). The use of 0,11 M acetic acid in extraction caused extreme increase of solubility of all studied metals. The highest solubility and mobility was found for arsenic (Fig 1).
CONCLUSIONS
Forest humus layers plays significant role in heavy metal retention. The solubility of heavy metals and arsenic differ between litter types and depend on level of contamination. The highest solubility and mobility of all studied elements was found under the youngest pine stands. Also very high water solubility of Cu was found in heavily polluted humus layers at the distance of 0,3 km from the smelter, what can be an evidence that this humus layers have no longer ability for copper retention. Litter acidification or lost of retention properties can cause rapid release of heavy metals and arsenic into the deeper soil layers and ground waters.
Acknowledgments: Project was supported from EU funds, Human Capital Programme. Project „Enterprising Ph.D. student - the investment in innovative region” leaded by Lower Silesia Voivoidship.