Projects / Programmes
Karst Carbon Cycle - Quantitative Physicogeographical Determination for the Various Climate-Relief Types of Slovenia
| Code |
Science |
Field |
Subfield |
| 6.12.01 |
Humanities |
Geography |
Physical geography |
| Code |
Science |
Field |
| P510 |
Natural sciences and mathematics |
Physical geography, geomorphology, pedology, cartography, climatology |
| Code |
Science |
Field |
| 5.07 |
Social Sciences |
Social and economic geography |
carbon cycle, karst, CO2, climate changes, Slovenia
Researchers (1)
| no. |
Code |
Name and surname |
Research area |
Role |
Period |
No. of publicationsNo. of publications |
| 1. |
25648 |
PhD Mitja Prelovšek |
Geography |
Head |
2013 - 2015 |
261 |
Organisations (1)
Abstract
Dissolution of carbonates is an important part of global carbon cycle since (a) it mobilizes long-term stored carbon in the form of carbonates (CaCO3 and CaMg(CO3)2) into the terrestrial hydrosphere, where carbon can be incorporated in the biospheric (biomass) or litospheric (fresh-water carbonates) part of global carbon cycle or is transported further into the oceans. On the other hand, (b) carbon from the atmosphere/pedosphere is included in the karstification as (nowadays problematic) CO2. Numerous karst phenomena (dissolutional microrelief forms, dissolution dolines, collapse dolines, karst caves, sinter, tufa) are, by the influence of other factors (tectonics, climate, soil and vegetation), therefore a result of global flow of carbon. From this point of view, role of karst is highly underestimated and seeks for more attention.
Although carbon cycle is closely related to karst, it was (a) only indirectly, (b) very rarely quantitatively and (c) never systematically researched from karst perspective in Slovenia. Even worldwide, comprehensive and quantified studies of carbon cycle on karst are rare since studies are usually too specific and related to only one scientific discipline or its branch (e.g. karst geomorphology, hydro(geo)logy, hydrochemistry, meteorology, speleology, environmental physics and chemistry, agronomy). From a geographical perspective, findings of the specific scientific field should be linked together to emphasize relations between them. Within this context, flow of carbon through karst massifs is an element that connects different scientific disciplines dealing with karst – and it is relatively simple according to the indestructibility of matter (carbon). Nowadays the conceptual understanding/models should be superimposed with quantified one. The latter is important locally (for karstology) and globally (for climatology). It enables numerical modeling even when the input parameters are changed (e.g. rise of atmospheric CO2 concentration, vegetation changes, modification of precipitation regimes).
The basic purpose of research project is determination and quantification of carbon flow on karst and their local/regional variability that are largely the result of different relief and climate situations. At the beginning, conceptual model for different Slovene relief-climate types will be established on the basis of Slovene and foreign literature review. Later on, this model will be quantitatively supplemented with findings of specific disciplines and on the basis of field work. Research work will be three-phase.
In the first phase karst massifs will be considered as black boxes, where research will be strictly focused on inputs and outputs of carbon depending on different relief-climate karst types. Field work will include physicochemical analyses of input and output waters since the water acts as a media for carbon flow. Generally speaking, especially dissolved carbon concentration and discharge will be measured on the field to calculate quantity of carbon that enters and leaves karst massifs. The result will be karst carbon balance for different relief-climate karst types.
Differences within each karst carbon balance will be considered within second phase. Already described methodology in previous paragraph will be supplemented by underground process measurements, which will provide us with momentary (use of WATEQ4F and PHREEQC computer programme) and cumulative (use of limestone tablets) direction and quantity of carbon flows through different sections of karst massifs, this is also the flow between hydrosphere, atmosphere and lithosphere.
Third phase will deal with conclusions of first and second one from the perspective of past and future changes of factors that influence karst carbon cycle. We will be interested especially in influence of climate change on carbon flow through karst that results in the form of karst phenomena.
Significance for science
Present-day intensive climate change that, according to general scientific consensus, is mostly the result of increased atmospheric CO2 levels is still one of the global hot topics. Despite several attempts of some scientists to argue karst as important carbon sink, role of karst on global carbon cycle remains marginal. Our results confirm role of karst as a buffer for atmospheric CO2 rise that is phenomena similar to role of oceans. However, more dissolved CO2 in the water and dissolution of carbonated contribute to some negative environmental consequences, like ocean acidification. Our research results proves that higher temperature regardless to amount of precipitation leads to higher soil pCO2 pressure, higher CO2 uptake and dissolution and more efficient transport through the karst massif. Relative importance of CO2 uptake by increased dissolution is difficult to define on the basis of this postdoc project due to limited spatial extent of research and lack of some important parameters, such as volume of groundwater bodies. Nevertheless, important quantitative data on inorganic carbon content related to water temperature were collected to make more specific calculations in the near future and to say that portion of “missing carbon sink” can be found within karst massifs and aquifers. Equilibrium CO2 concentration calculated for measured SICal or before CO2 outgassing (SICal=0) that were measured during postdoc project to calculate flux of inorganic carbon through karst are usually neglected in hydrogeological and geochemical studies on karst due to weak knowledge on carbonate geochemistry, role of involved processes or lack of accurate pH measurements, which still present challenge for modern instruments. However, similarly as water temperature and oxygen isotope ratio, equilibrium pCO2 at SICal=0 in case of authigenic recharge and SICal(0.5 (general limit for calcite precipitation) more or less reflects climatic conditions in watershed. In case of equal height of watershed, oxygen isotope ratio is the same in case of authigenic (percolation water) and allogenic recharge (sinking streams) which makes differentiation of water source impossible; however, this is not the case for equilibrium pCO2 concentration that is substantially higher in case of authigenic recharge. This has high applicable value since differentiation between authigenic and allogenic recharge at underground stream or spring is possible; applicability was successfully tested in practice. Research done on present-day dissolution in stream caves using microerodimeter and limestone tablets indicated very low values, long-term growth of big stream caves and negligible mobilization of inorganic carbon from the limestone or dolomite cave walls. During postdoc project, hydrochemical characteristics confirms inability of analyzed waters to efficiently dissolve limestone in the underground in case caves are fed by allogenic waters at least partly draining karst areas. Independent conclusions done by some other researchers indicate big discrepancy between cave growth calculated with process-based models and field observations. It is clear that boundary conditions, namely poorly adjusted underground CO2 levels, should be more properly defined in speleogenetic models that will be possible using our results from the caves and using our calculated data from drip water chemistry. However, our results indicate that big stream caves are the result of dissolution lasting hundreds of thousands or millions of years. On the contrary, dissolution in surface streams on carbonate rocks can be much more intensive due to biodissolution; the latter was probably for the first time measured in freshwater environment and explains formation of gorges in karst where bed load is missing and water is generally oversaturated with respect to calcite, e.g. at karst poljes. It is possible that plays an important role during formation of antecedent valleys on karst.
Significance for the country
Karstology is one of the most important interdisciplinary field where Slovenian researchers play, partly from historical reasons, leading and appreciated role in global science. However, instead of enjoying past achievements, introduction of novel research approach bringing new perspective and data is the only proper way to continue successful past development in developing science. Despite the fact that competition with research centers rich in infrastructure and research groups in developed world, as well as in intensively karstified China where work in karstological issues is in great rise in last decade, is inevitably hard, Slovene karstology can be recognizable worldwide with innovative and interdisciplinary approach and small but comprehensive research projects. During implementation of this PostDoc project we did not focus on traditional limits of each scientific discipline dealing with karst but rather introduce cycling of carbon on karst as a basic common denominator for basic processes on karst. During implementation of project research infrastructure owned by Karst Research Institute ZRC SAZU was very effectively used. Additional value of PostDoc is also successful collaboration with Chinese and Croatian karstologists where dissemination of knowledge and practice was very fruitful. Slovenia hosts some past and present-day milestones related to show caves: Vilenica is recognized as the first show cave at least in Europe, Postojna Cave is along with Mammoth Caves the most visited cave in the world, Škocjan Caves are Europe’s most impressive karst phenomenon at the contact karst recognized as UNESCO world heritage, while some other caves (e.g., Križna Cave, Planinska Cave) are recognized as important natural values at national level. Touristic development of some caves is now approaching third or fourth hundred years and experiencing positive trend of visitoring in the last decades. Despite the fact that PostDoc was focused on basic research, findings related to processes with low intensity where anthropogenic factors become very important (which results in high vulnerability of caves) have applicable value. Taking into consideration rate and other characters of natural processes that were subject of PostDoc, like water-atmosphere interaction (e.g., outgassing of CO2 from the water) and rock-water interaction (dissolution and sinter deposition) in the underground, management of show caves can be more easily directed toward sustainable way. In addition, it is easier and more effective to influence decisions that are taken by show cave management in proper way with objective and quantitative data that prove negative impacts and skip general measures where they are proved to be ineffective. In such way, anthropogenic impact of visiting, where amount of CO2 is directionally connected with number of visitors, was presented to Postojna Cave management and its group of tourist guides. Taking into account that circulation and role of carbon or CO2 on karst is researched by several scientific disciplines where flux of carbon from soil to water, from rock to water, from water to air and rock creates several (methodological) limitations of single discipline, consideration of carbon (or CO2) as “research discipline free” substance incredibly simplify view on carbon circulation in karst. As such quantitatively supported conceptual cycling of carbon can be effectively used for graduate and postgraduate education. Research outputs were already used in postgraduate study of interdisciplinary Karstology at University of Nova Gorica and will be continually used even more in the near future, e.g at Geographical department at University of Primorska. Dissemination of results among other universities and research centers was already and will be achieved during participation on coming congresses (e.g., at CBDGC meeting that will be held in September 2016 in Postojna) and other scientific meetings.
Most important scientific results
Annual report
2013,
2014,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Annual report
2013,
2014,
final report,
complete report on dLib.si
