Partitioning of Zn, Pb and Cd in river sediments from a lead and zinc mining area using the BCR three-step sequential extraction procedure

This study investigates the extent of pollution in sediments collected along the river Mezˇa and its tributaries within the lead and zinc mining area of the Mezˇica valley in Slovenia. The objective is to evaluate the burden of heavy metals, specifically Zn, Pb, and Cd, utilizing a slightly modified BCR three-step sequential extraction procedure to determine the total concentrations of these metals and their partitioning between easily and sparingly soluble sediment fractions. Total metal concentrations were validated against Certified Reference Material CRM 601, demonstrating good agreement. Normalization to Al was conducted to differentiate between natural and anthropogenic sources of these metals. Results indicate that Zn predominantly occupies the most sparingly soluble fraction, associated mainly with organic matter and sulfides, while Pb shows a similar distribution, and Cd is largely found in the sparingly soluble fraction. Notably, the sediment of the Helena rivulet exhibited the highest total concentrations of these metals, reflecting previous mining activities. Despite a relatively low presence of easily soluble metal fractions, the concentrations remain high due to overall elevated total metal levels, indicating significant pollution affecting both terrestrial and aquatic environments.