Leaching potential of selenium and metals from an ununregulated waste of slag, ash and Raša coal (Štrmac, Istria)

U naselju Štrmac nalazi se nepropisno odloženi otpad šljake i pepela nastao tijekom četiri stoljeća eksploatacije i izgaranja ugljena. Ispitano je ispiranje elemenata iz uzoraka Raškog ugljena, otpadne šljake i okolnog tla. Ukupne koncentracije elemenata u pet uzoraka određene su u uzorcima nakon totalne digestije u mikrovalnoj pećnici. Za ekstrakciju, testirane su tri metode ekstrakcije, ASTM, EP i TCLP (pH 4.93 i 2.9). Multi-elementarna analiza razgrađenih uzoraka i ekstrakata izvršena je tehnikom spektrometrije masa visoke razlučivosti uz induktivno spregnutu plazmu (HR-ICP-MS). Svi su uzorci analizirani na 29 elemenata (Al, As, Ba, Be, Bi, Cd, Co, Cr, Cs, Cu, Fe, Li, Mn, Mo, Ni, P, Pb, Rb, S, Sb, Sc, Se, Sn, Sr, Ti, Tl, U, V, Zn). Ukupne koncentracije kretale su se za glavne elemente od 0.005-21.1%, a za elemente u tragovima od ispod granica detekcije do 1083 mg kg-1. Najviše ukupne koncentracije za većinu elemenata izmjerene su u uzorku tla. Koncentracije ekstrakata kretale su se od ispod granica detekcije do 507 mg L-1 i slijedile su redoslijed: ASTM < EP < TCLP < TCLP2, pri čemu su najviše koncentracije zabilježene u uzorcima otpada za većinu elemenata. V, S, U i Mn bili su iznad ograničenja u svim metodama. V, S i U su bili iznad u uzorcima brda, a Mn u uzorku tla. Relativna masa ispranih elemenata kretala se u rasponu od 0.00001% do 1.94% što je znatno manje u usporedbi sa sličnim istraživanjima. Najveći RML zabilježeni su u uzorcima brda za većinu elemenata. Na mobilnost elemenata utječu pH i mineralogija (karbonati i sulfati).Unregulated waste generated from four century long coal mining and combustion is still left in Croatian village situated on karstic area. Leaching of elements from Štrmac ash and slag heap, soil around heap and Raša coal was investigated. For total element analysis, five samples were subjected to total digestion in microwave oven. For extraction, three extraction procedures were tested, ASTM, EP and TCLP (pH 4.93 and 2.9). Multielemental analysis of bulk samples and extracts was performed by HR-ICP-MS. All samples were analysed for 29 elements (Al, As, Ba, Be, Bi, Cd, Co, Cr, Cs, Cu, Fe, Li, Mn, Mo, Ni, P, Pb, Rb, S, Sb, Sc, Se, Sn, Sr, Ti, Tl, U, V, Zn). Total concentrations ranged from 0.0046 to 21.1% for major oxides and from below the detection limit to 1083 mgkg-1 for trace elements. The highest total concentrations were measured in the soil sample for majority of elements. The extract concentrations ranged from below the detection limit to 506.97 mg L-1 and followed the order: ASTM < EP < TCLP < TCLP2. The highest extract concentrations were observed in hill samples. V, S, U and Mn were above the limit in all extraction procedures. V, S, U were above in hill samples, while Mn was above in soil sample. Relative Mass Leached of elements ranged from 0.00001% to 1.94% which is much lower compared to similar studies. Highest RML were observed in hill samples. Mobility of elements is controlled by pH and mineralogy (carbonates and sulphates)