Environmental hazard assessment of mercury-contaminated soil of the Idrija district - monitoring of pH, electrical conductivity and total leached mercury concentration : bachelor thesis

Rudnik Idrija u Sloveniji bio je drugi najveći rudnik žive na svijetu i značajan antropogeni izvor žive. Tlo u okolici rudnika još uvijek sadrži od 10 do čak 10 000 mg Hg/kg na drevnim mjestima pečenja rude. Budući da je Idrija krško područje postoji opasnost od infiltracije žive oborinskim vodama u dublje slojeve tla te u konačnici i u podzemne vode. Kako bi se procijenio utjecaj žive na okoliš u području rudnika Idrija i šire, potrebno je ispitati njeno potencijalno ispiranje iz tla. Eksperimenti ispiranja žive iz onečišćenog tla sa sadržajem žive od 1347 mg Hg/kg provedeni su standardnom šaržnom metodom prema normi DIN 38414 S4 u ultračistoj vodi različitih početnih pH o vrijednosti u rasponu od 3,00 do 11,46 tijekom 24 h. Ukupna koncentracija izlučene žive nakon 24 h bila je vrlo niska i iznosila od 0,33 do 17,43 µg/L, što ukazuje na vrlo visoki afinitet žive prema organskim i anorganskim tvarima u tlu. Međutim, gotovo sve izmjerene koncentracije bile su iznad maksimalno dopuštene koncentracije za vode za ljudsku potrošnju prema hrvatskim i slovenskim zakonima, kao i prema Direktivi Vijeća Europske zajednice. Praćenjem ukupne koncentracije otopljene žive u odabranim vremenskim intervalima tijekom 24 h dobivene su značajno veće koncentracije ukupno izlučene žive od 102,86 do čak 488,02 µg/L, i to nakon 2,5 do 7,0 sati od početka eksperimenta. Dobiveni rezultati ukazuju na nužnost daljnjeg praćenja kakvoće tla na drevnim mjestima pečenja rude u okolici Idrije, detaljnijeg istraživanja izlučivanja žive u prvih nekoliko sati ispiranja tla te određivanja oblika u kojemu se živa nalazi u tlu i vodi.The Idrija mine in Slovenia was the second largest mercury mine in the world and significant anthropogenic source of mercury. The soil in surrounding the mine still contains from 10 to even 10.000 mg Hg/kg at ancient roasting sites. Since Idrija is karst area there is dangerous of mercury infiltration by rain water into deeper soil layers and thus into groundwater. In order to assess the impact of mercury onto environment in Idrija district and beyond, it is necessary to examine its potentially leaching from the soil. Leaching experiments of mercury contaminated soil with 1347 mg Hg/kg were performed by standard batch method according to DIN 38414 S4 in ultrapure water of different initial pH o values in the range of 3.00 to 11.46 for 24 h. The total leached mercury concentration after 24 h was very low and ranged from 0.33 to 17.43 µg/L, indicating very high affinity of mercury toward organic and inorganic substances in the soil. However, almost all measured concentrations were above the maximum permissible levels for waters for human consumption according to Croatian and Slovenian legislations as well as to the Directive of the European Community Council. By monitoring the total leached mercury concentration in time intervals within 24 h, the concentrations were significantly higher, and after 2.5 to 7.0 hours from the beginning of the experiment ranged from 102.86 to even 488.02 µg/L. The obtained results indicate the need for further monitoring of the soil quality at ancient roasting sites of the Idrija district. A more detail study of mercury leaching in the first few hours of the experiment is necessary with determination of the form in which the mercury is present in the soil and the water