Hidrogeohemijska valorizacija esencijalnih mikroelemenata mineralnih voda Srbije

Abstract

Mineralne vode još od davnina privlače pažnju ljudi i to kako u pogledu istraživanja i proučavanja, tako i u pogledu njihovog iskorišćavanja. Naročito je važno poznavanje sadržaja mikroelemenata u njima, jer su to komponente njihovog hemijskog sastava koje ih odvajaju od tzv. „običnih“ malomineralizovanih voda. U ovom radu proučavani su odabrani esencijalni mikroelementi (fluor, bor, litijum, kalijum, stroncijum i silicijum), u mineralnim vodama Srbije, pri čemu je analizirano preko 130 uzoraka mineralnih voda iz različitih geoloških sredina, to jest hidrogeoloških rejona. Cilj ovog istraživanja bio je izdvajanje glavnih hidrogeohemijskih procesa, koji utiču na vodnu migraciju razmatrane grupe mikroelemenata i njihovu mobilizaciju iz stena. Pored toga, trebalo je definisati hidrogeohemijske uslove (u prvom redu, hemijski sastav voda i litološki sastav sredine) koji pogoduju pojavi povišenih koncentracija ovih elemenata u mineralnim vodama Srbije. U cilju rešavanja problema koji je predmet ove doktorske disertacije korišćena je savremena metodologija, kako prilikom terenskih merenja i laboratorijskih analiza, tako i prilikom sistematizacije i obrade podataka. Na rezultate ispitivanja fizičko-hemijskih karakteristika mineralnih voda (in situ merenja na sirovim uzorcima, skraćene hemijske analize i određivanje sadržaja mikroelemenata) primenjena je multivarijantna statistička analiza (faktorna analiza, Q-mod i R-mod klaster analiza), radi sveobuhvatnijeg sagledavanja raspoloživih informacija. Pored statističkih proračuna (softverski paketi IBM SPSS Statistics 19.0 i StatSoft STATISTICA 10.0), ispitivan je i prostorni raspored koncentracija mikroelemenata u mineralnim vodama na teritoriji Srbije (softverski paket Esri ArcGIS 9.3), a na određenom broju uzoraka mineralnih voda vršeno je i hidrohemijsko modeliranje (softverski paket USGS PHREEQC 2.18). Upotreba faktorne analize omogućila je grupisanje hidrohemijskih parametara koji su međusobno korelisani i koji se mogu dovesti u vezu sa određenim hidrogeohemijskim procesima. Primenom faktorne analize na matricu sačinjenu od 14 parametara hemijskog sastava, određivanih na 110 uzoraka mineralnih voda sa teritorije Srbije, izdvojena su tri faktora, koji zajedno objašnjavaju 67,4 % ukupne varijanse podataka. Jana S. Stojković Doktorska disertacija iv Interpretacija dobijenih faktora ukazala je na sledeće hidrogeohemijske procese: uticaj visokomineralizovanih, hidrohemijski zrelih voda; ugljokiselinsko razlaganje kristalastih škriljaca, granitoidnih intruzija i tercijarnih vulkanita; katjonsku izmenu; rastvaranje karbonatnih stena; dejstvo azotnih termalnih voda na minerale iz grupe kvarca, kao i silikatne minerale bogate fluorom i litijumom. Na odabranim primerima mineralnih voda ukazano je na delovanje izdvojenih procesa, uz analiziranje uslovljenosti ovih procesa litološko-mineraloškim sastavom izdani. Klaster analizom izvršeno je grupisanje uzoraka mineralnih voda, na osnovu sličnosti u fizičko-hemijskim karakteristikama. Tako su izdvojene četiri grupe (klastera) i osam podgrupa, koje predstavljaju različite hidrohemijske tipove mineralnih voda, dakle, koje se razlikuju po sadržaju razmatranih mikroelemenata. Ispitan je i uticaj gore pomenutih hidrogeohemijskih procesa na svaki od klastera. Izradom karata distribucije koncentracija mikroelemenata u mineralnim vodama Srbije, kao i konstrukcijom odgovarajućih statističkih dijagrama, sagledane su zakonomernosti rasprostranjenja analiziranih mikroelemenata, kao i opseg varijacije njihovih koncentracija. Data je i ocena upotrebljivosti ispitivanih mineralnih voda za piće, upoređivanjem registrovanih koncentracija mikroelemenata sa limitima propisanim domaćim i stranim pravilnicima i smernicama, koji se odnose na pijaću vodu. Primenom hidrohemijskog modeliranja na odabrane uzorke mineralnih voda, proračunata je zastupljenost najverovatnijih jonskih oblika svakog od analiziranih mikroelemenata, čime je bliže definisano njihovo ponašanje u vodonosnoj sredini. Sistematizacijom rezultata ovog istraživanja izdvojene su sledeće zaključne konstatacije:  Udruženo delovanje sva tri izdvojena faktora ima za posledicu pojavu povišenih koncentracija svih analiziranih mikroelemenata. Ovo je slučaj kod termalnih ugljokiselih mineralnih voda, koje se javljaju u pukotinskoj izdani, formiranoj u paleozojskim ili proterozojskim metamorfitima. Pri tom su od presudnog značaja procesi savremene magmatske aktivnosti, to jest prisustvo tercijarnih intruziva ili vulkanita, granitoidnog sastava. Ovim je potvrđena pretpostavka o paragenezi razmatranih mikroelemenata.  Dominacija svakog od izdvojenih faktora uslovljena je položajem značajnijih geoloških struktura na teritoriji Srbije. Prvi faktor je dominantan kod pojava koje se vezuju za Panonski basen i manje neogene basene, kao i kod pojava lociranih u paleozojskim ili proterozojskim škriljcima, pri čemu je gotovo uvek prisutna bliska veza sa granitoidnim intruzivima ili vulkanitima. Drugi faktor je izražen kod pojava lociranih u karbonatnim stenama, po obodu ili u podini neogenih Jana S. Stojković Doktorska disertacija v basena. Dominacija trećeg faktora vezuje se za područja u čijoj geološkoj građi dominiraju vulkaniti i piroklastične stene.  Definisani su hidrogeohemijski uslovi koji pogoduju pojavi povišenih koncentracija svakog od šest ispitivanih mikroelemenata, i to uporednom analizom karata rasporeda (maksimalnih) faktorskih bodova i karata distribucije koncentracija mikroelemenata. Visoki sadržaji fluora vezuju se za dejstvo prvog i trećeg faktora, to jest za ugljokisele mineralne vode u oblastima mladog magmatizma i za azotne termomineralne vode. Visoke koncentracije bora vezuju se isključivo za dejstvo prvog faktora, bilo da se radi o mineralnim vodama dubljih horizonata neogenih basena ili o ugljokiselim mineralnim vodama u oblastima mladog magmatizma. Litijum i kalijum se odlikuju skoro podjednako dobrom migrativnom sposobnošću u različitim hidrogeohemijskim uslovima (dejstvo prvog, ali i drugog i trećeg faktora). Povišeni sadržaji stroncijuma posledica su dejstva prvog i drugog faktora, tačnije procesa ugljokiselinskog razlaganja alkalnih feldspata i plagioklasa, kao i kalcita i dolomita. Povišene koncentracije silicijuma u mineralnim vodama vezuju se za treći faktor, koji karakteriše dejstvo baznih termalnih voda na minerale iz grupe kvarca, sadržane u kiselim magmatskim stenama ili metamorfitima nastalim preobražajem granitoidnih stena.

Mineral waters have attracted people’s attention since old times, they were researched and studied for their exploitation and consumption. It is especially important to know their microelements content, because these components separate mineral waters from regular low mineralized tap water. The chosen essential microelements (fluorine, boron, lithium, potassium, strontium and silicon) in mineral waters of Serbia have been studied in this work. Over 130 mineral water samples from different types of aquifers and from different hydrogeological units, have been analyzed. The aim of this research was to point out the main hydrochemical processes which effect water migration of these microelements and their mobilization from the rocks. Besides that, hydrochemical conditions (especially chemical composition of groundwater and lithological composition of the aquifer) causing high concentrations of these elements in mineral waters of Serbia have been defined. In order to solve the problem which is the topic of this doctoral dissertation, modern methodology has been used during the field measurements and laboratory analysis, as well as for systematization and data analysis. Multivariate statistical analysis (factor analysis, Q-mode cluster analysis and R-mode cluster analysis) has been applied on the research results of physical and chemical characteristics of mineral waters (in situ measurements on raw samples, short chemical analyses and analyses of the content of microelements) for better understanding of gathered information. Besides statistical calculations (software packages IBM SPSS Statistics 19.0 and StatSoft STATISTICA 10.0), spatial distribution of microelements in mineral waters of Serbia has been studied (software package Esri ArcGIS 9.3), and hydrochemical modeling has been applied on a certain number of mineral water samples (software package USGS PHREEQC 2.18). The use of factor analysis allowed grouping of hydrochemical variables correlating to each other, which can be connected to certain hydrogeochemical processes. Applying factor analysis to a dataset that consists of 14 chemical parameters measured on 110 mineral water samples from Serbia, three factors were extracted, which explain 67.4 % of the total variance in the analyzed dataset. The interpretation of obtained factors has Jana S. Stojković Doktorska disertacija vii indicated several hydrogeochemical processes: the influence of highly mineralized, hydrochemically mature groundwaters; carbonic acid weathering of schists, granitoid intrusions and Tertiary volcanic rocks; cation exchange; dissolution of carbonate rocks; the effect of nitrogen thermal waters on silica minerals and also on silicate minerals rich in fluorine and lithium. The mechanism of these processes has been studied on the chosen mineral water samples, in addition to analyzing how these processes are influenced by lithological and mineralogical structure of aquifer. Using the cluster analysis the sample grouping of mineral waters has been done, on the basis of similarity of their physical and chemical characteristics. In this way four groups (clusters) and eight subgroups have been distinguished, representing different hydrochemical types of mineral waters, regarding the differences in their microelements content. The effect of above mentioned hydrogeochemical processes on each cluster has also been examined. By making distribution maps of microelements concentration in mineral waters of Serbia, as well as by constructing statistical diagrams, pattern of spatial distribution of analyzed microelements have been perceived, as well as the extent of variation of their concentrations. The possibility of everyday human consumption of the researched mineral waters has been assessed by comparing detected microelements concentrations to the limits recommended by domestic and foreign drinking water regulations and guidelines. Applying hydrochemical modeling on chosen mineral water samples the presence of the most probable ion species of the analyzed microelements has been calculated, closely defining their aqueous hydrogeochemistry. By systematizing the results of this research the following conclusions have been drawn:  The joined effect of all three extracted factors results in appearance of higher concentration of all analyzed microelements. This is the case in thermal carbonated mineral waters appearing in fracture aquifers formed in Paleozoic or Proterozoic metamorphic rocks. Young magmatism is of the crucial importance referring to the presence of Tertiary granite plutonic or volcanic rocks. The assumption about paragenesis of the considered microelements has been confirmed by this fact.  The domination of each of the extracted factors has been caused by the position of the important geological structures on the Serbian territory. The first factor is dominant at mineral water occurrences in the Pannonian Basin and smaller Neogene basins and also at the mineral water occurrences in the Paleozoic or Jana S. Stojković Doktorska disertacija viii Proterozoic schists, while the close relation to granite plutonic or volcanic rocks is always present. The second factor is present at the mineral water occurrences located in carbonate rocks at the edge of Neogene basins or in underlying carbonate rocks. The domination of the third factor is connected to the areas where volcanic and pyroclastic rocks dominate in geological structures.  The hydrogeochemical conditions which cause the appearance of high concentrations of each of six considered microelements have been defined by comparing analysis of distribution maps of (maximum) factor scores to distribution maps of microelements concentrations. The high content of fluorine is connected to the activity of the first and the third factor, referring to carbonated mineral waters in the regions of young magmatism and to nitrogen thermal mineral waters. The high concentrations of boron are connected only to the influence of the first factor, both in mineral waters from deeper horizons in Neogene basins and carbonated mineral waters in the regions of young magmatism. Lithium and potassium are almost equally capable of migrating in different hydrogeochemical conditions (the effect of the first, but also of the second and the third factor). The higher content of strontium is the result of the first and the second factor effect, namely the processes of carbonic acid dissolution of alkali feldspars and plagioclase feldspars and also of calcite and dolomite. The higher concentrations of silicon in mineral waters are linked to the third factor, which is characterized by the effect of base thermal waters on silica minerals of the acid igneous rocks and in the metamorphic rocks originated from granitic rocks.