Investigation of correlations between magnetic susceptibility and elemental content in the Kupa River sediments (Croatia)

<p>The Kupa River basin occupies the west-central part of Croatia and is shared by two neighboring countries (Slovenia, Bosnia and Herzegovina). It is the tributary of the Sava River and meets the latter at Sisak after traversing a distance of 294 km. The Sava River belongs to the Danube River watershed and enters the Danube River at Belgrade (Serbia).      </p><p>An extreme barium anomaly in sediments of Kupica and Kupa rivers was discovered during 2003 (Frančišković-Bilinski, 2006). It is result of un-careful mine waste disposal. Therefore this river has a big potential to be used as a “natural laboratory” in the future to study sediment transport processes in rivers, so we repeated sampling on most important locations in 2018, to see which processes happened during that time frame. In the current study, we aim to investigate correlations between magnetic susceptibility (MS) and elemental content of 26 studied elements in the fine sediment fraction (<63 µm) of samples from 2018. MS method is a fast and cheap method, which can give indication of contamination with some metals, so we aimed to test its suitability on Kupa River sediments. Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) was used to determine the concentration of the studied elements, after sequential extraction procedure (Sakan et al., 2016). Total concentrations of each element were determined as the sum of concentrations determined in each fraction. The same method was applied recently for determination of Ba concentrations in Kupa River sediments by Frančišković-Bilinski et al. (2019).</p><p>Correlation analysis was performed to reveal statistical correlations between MS and 26 elements analyzed by ICP-OES. Ten of them showed negative correlation (As, B, Ba, Fe, K, Li, Mg, Na, P, S), while other elements showed positive. Chromium showed excellent correlation with MS (0.91) and is element with the highest correlation to MS. All other elements show much weaker correlation with MS. Element with strongest correlation to MS after Cr is vanadium (0.62), followed by Mn (0.52), Al (0.52) and Cd (0.50). All other elements have rather weak correlation with MS, among which highest are those of Sr (0.45), Zn (0.35), Be (0.28), Co (0.27), Pb (0.27) and Ti (0.26). Rest of elements has very low correlation.</p><p>Our research confirmed that MS is not suitable to study barium contamination in sediments, as they have low negative correlation (-0.18). Low negative correlation of MS with Fe (-0.12) indicates that MS is not caused by iron minerals in Kupa River sediments. MS values show extreme value at the same location as does Cr, which is bound to residual fraction of yet not known mineral composition.</p><p>Earlier data of Frančišković-Bilinski (2007) show that SiO<sub>2 </sub>group of minerals predominate in Kupa sediment at Pokupsko, where MS and Cr have highest values.</p><p>Rererences:</p><p>Frančišković-Bilinski, S. (2006). J.Geochem.Explor. 88, 1-3, 106-109.</p><p>Frančišković-Bilinski, S. (2007). Fresenius Env.Bull. 16, 5, 561-575.</p><p>Frančišković-Bilinski S., Bilinski, H., Sakan, S., Đorđević, D., Popović, A. (2019). SGEM Conference proceedings, 19, 3.1., 73-80.</p><p>Sakan, S., Popović, A., Anđelković, I., Ðorđević, D. (2016). Env.Geochem.Health 38, 855–867.</p>