Pergamon zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Applied Geochemisfry , Vol. 11, pp. 197-202. 1996 Copyright 0 1996 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0883-2927196 $15.00 + 0.00 O&%83-2927(95)00087-9 Variability of heavy metals content in bottom sediments of the Wilga River, a tributary of the Vistula River (Krak6w area, Poland) Marta Wardas, Leokadia Budek and Edeltrauda Helios Rybicka University of Mining and Metallurgy, al. Mickiewicza 30, 30-059 Cracow, Poland Abstract-The concentration of heavy metals in the sediments of the Wilga River has been studied. Comparison of a sample from the city border with that from the river outlet reveals increasing metal concentrations by factors ofca. 27 for Cr, 8 for Cu, 5 for Zn and Ni and 3 for Pb. Since 1989, for most metals. a decreasing trend in concentrations, at compared sampling sites, has been noted. Nevertheless, the amount of heavy metals is still rather high and ranges (in mg/kg) as follows: 185-715 Zn, 38-196 Pb, 27-195 Cu. 3-52 Cr, 3-98 Ni and 1-8 Cd. A strong variability of metal concentration along the river course has been found. Their elevated concentration results from some sources of pollution situated in the river valley, including: industrial plants, their settling ponds and busy roads. It is very probable that morphological features of the river, like river bends, cause the increase ofmetal contents. It has been found that the amount ofheavy metals contributed by grain fractions < 20 pm is most frequently comparable with or higher than the proportions of that fraction in the fine fraction of sediment ( < 63 pm). Copyright 0 1996 Elsevier Science Ltd INTRODUCTION The study of heavy metal concentrations in river sediments in Poland has a relatively short history and has been conducted by few authors. Pastemak (1974) investigated the influence of zinc and lead smelters on the contents of heavy metals in sediments of the Przemsza River (with tributaries). Klimek and Zawi- lifiska (1985) compared the amount of heavy metals in old (medieval) and recent alluvia of the Vistula River and estimated an impact of industrialisation on the degree of pollution. For the old alluvia the contents (in mg/kg) of Cd, Zn and Pb were 0.2X).8,22-90 and 0.2- 20 while for the youngest ones ranges were 61-200; 1960-4200 and 220-600, respectively. Kabata Pendias and Bolibrzuch (1979) found elevated concentrations of Cd and Pb in the Bystra River (SE Poland). Mining and processing activity, concentrated mainly in the southern part of Poland (Krakbw - Silesia Region), heavily affects the rivers in that region. Consequences of that influence are shown by Macklin and Klimek (1992) as a considerable increase of Cd, Pb and Zn in the Upper Vistula and Lower Przemsza River in the last 100-150 years. According to results obtained by Helios Rybicka (1983, 1986) and Helios Rybicka and Wardas (1989), who studied the content of heavy metals in the catchment of the Vistula River, the Wilga River belongs to the most polluted tributaries of the Vistula River within the Krak6w City area. Those results motivated a more detailed study of that river. The present paper comprises the results of two stages of investigation. The first stage was designed as a test study, the aim of which was to get rough information about heavy metals content in the sediment of the Wilga River and its possible changes with time (1982-1991). The aim of the second stage, carried out in 1994, was to concentrate on a short section of the river and to (i) estimate a variability of heavy metal content, (ii) identify possible sources of contamination, (iii) define factors influencing accu- mulation of heavy metals in bottom sediments of the heavily polluted Wilga River. MATERIALS AND METHODS In the first stage of investigation, 13 samples of river sediments were collected along the river course (distance ca. 12 km) from the city border (sample la) to its outlet (sample 28a). For some collecting sites (samples 26a, 27a and 28a) the sampling was repeated every 2-3a or more in order to estimate possible changes of heavy metal contents with the time. Sampling was done by pressing a sampling tube into sediment about 1 m from the river bank to a depth of 10 cm. No duplicate samples were collected at this stage. In the second stage, a short section of the river (ca. 700 m) was relatively densely sampled (22 samples with 10 duplicates collected ca. 3 m upstream of respective sampling sites). Within that area some potential sources of pollution (two bridges, one busy road, galvanic and leather plants were identified). Other sources of pollution include two ponds. being former settling ponds of the nearby plants (Fig. 1). Unexpectedly, it was found that those ponds drain into the Wilga River. Four samples were collected from each of the ponds to evaluate their possible role in the river pollution. For all the samples the grain fraction < 63 pm was wet separated and for selected samples fractions < 20 pm. The contents of Zn, Pb, Cu, Cr, Ni and Cd were determined in separated grain fractions. Metals were extracted from the solid with concentrated boiling HNO3 and their amounts determined by AAS. For each duplicate-sample of the second stage duplicated analyses were made. Sampling instruments and analytical procedure were the same in both stages of investigation. Detection limits (in mg/dm3) of the used AAS instrument (SP9 PYE UNICAM) were as follows: Zn - 0.050; Pb - 0.100; Cu - 0.050; Cr - 0,030; Ni - 0.030; Cd - 0.010. 197