| Abstract | U posljednjih tridesetak godina (1990. - 2020.), u okviru programa monitoringa okoliša, provodi se mjerenje koncentracije žive u gujavicama i tlu na četiri lokacije u blizini centralne plinske stanice Molve sa svrhom određivanja učinkovitosti sustava za uklanjanje žive. Naime, sastav prirodnog plina sadrži elementarnu živu, koja se mora ukloniti prije puštanja plina prema konačnim potrošačima. U prošlosti se većina žive ispuštala u okoliš, no razvojem svijesti o štetnosti žive ugrađen je 1993. godine adsorber žive kojim se uređajem nastoji smanjiti štetni utjecaj čovjeka na okoliš. Živa je dobro poznati toksični metal koji se tijekom prošlosti široko upotrebljavao, a čija se upotreba danas sve više ograničava zbog njezine toksičnosti i sposobnosti biomagnifikacije duž hranidbenog lanca. Gujavice se smatraju idealnim organizmima za ispitivanje toksičnosti tla i za procjenu bioraspoloživosti brojnih kontaminanata u tlu. One imaju najveću biomasu među beskralješnjacima tla i predstavljaju hranu za mnoge životinje. Zbog toga, ako se u njihovom tkivu pronađe živa, mogu izravno utjecati na zdravlje životinja koje se nalaze na višem stupnju hranidbenog lanca. Gujavice su skupljane jednom godišnje, a uzorci tala dva puta godišnje, u proljeće i jesen, te su korištenjem standardiziranih protokola analizirani na ukupni sadržaj žive. Vrijednosti koncentracija žive u gujavicama bile su u rasponu 0,119 - 0,466; 0,045 - 1,292; 0,018 - 1,236 i 0,031 - 0,779 μg/g suhe mase uzorka, za lokacije Molve 9, Molve 10, Molve 11 i Molve 12. Koncentracije ukupne žive u različitim tipovima tala na istim lokacijama bile su 0,008 - 0,350; 0,035 - 0,250; 0,020 - 0,240 i 0,071 - 0,515 μg Hg/g uzorka tla. Na temelju tih podataka, izračunat je faktor bioakumulacije koji je bio u rasponu od 0,3 do 17,5. Na lokacijama Molve 9, 10, 11 i 12 nije pronađena statistički značajna korelacija između vrijednosti žive u tlu i gujavicama kroz period od 30 godina. Sve srednje vrijednosti koncentracija žive u tlu, s izuzetkom 2016. godine na lokaciji Molve 12 (0,515 μg/g), bile su ispod propisanih MDK za poljoprivredna tla s obzirom na njihove fizikalne i kemijske karakteristike (0,5 μg/g). Raspon vrijednosti faktora bioakumulacije bio je u skladu s navodima iz literature. Zbog toga se može zaključiti da je sustav za odstranjivanje žive iz plina učinkovit i da je područje u blizini plinsko - bušotinskog sustava Podravina karakterizirano niskim sadržajem žive i zbog toga predstavlja nizak rizik za zdravlje životinja i ljudi. |
| Abstract (english) | In the last thirty years (1990 – 2020), as part of the environmental monitoring program, mercury concentrations in earthworms and soil were measured at four locations near the Molve central gas station to determine the effectiveness of the mercury removal system. Namely, the composition of natural gas contains elemental mercury, which must be removed, before distributing the gas to final consumers. In the past, mercury was released into the environment, but with the worldwide recognition of mercury toxicity, a mercury absorber was installed in 1993. Such device is used to reduce the harmful effects of man on the environment. Mercury is a well - known toxic metal, that has been widely used in the past, and its use is being increasingly reduced today due to its toxicity and biomagnification ability along the food chain. Earthworms are the standard soil toxicity test organism and are ideally suited for assessing the bioavailability of many chemicals in soil. They have the highest biomass among soil invertebrates and are consumed by many other animals. Therefore, if organic mercury is found in their tissue, it can affect the health of other animals that are higher on the food chain. Earthworms were collected once a year, and soil samples twice a year, in spring and autumn, and were analyzed for total mercury content using standardized protocols. Mercury concentrations in earthworms were in range 0.119 - 0.466; 0.045 - 1.292; 0.018 - 1.236 i 0.031 - 0.779 μg/g dry weight for locations Molve 9, Molve 10, Molve 11 and Molve 12, respectively. Total mercury concentrations in different soil types on the same locations were 0.008 - 0.35; 0.0350 - 0.250; 0.020 - 0.240 and 0.071 - 0.515 μg Hg/g of soil sample. Based on these data, a bioaccumulation factor ranging from 0.3 to 17.5 was calculated. At locations Molve 9, 10, 11 and 12, no statistically significant correlation was found between mercury values in soil and earthworms over a period of 30 years. All mean mercury concentrations in soil, with the exception of 2016 at Molve 12 (0.515 μg/g), were below the prescribed MAC (maximal acceptable content) for agricultural soils considering their properties (0.5 μg/g). The range of bioaccumulation factor values was consistent with the literature. Therefore, it can be concluded that the mercury removal system is efficient and that the area near the gas - well system Podravina is characterized by low mercury content, and consequently presents a low risk to wildlife and human health. |
