Showing papers by "Sonja Lojen published in 2015"

Is global warming affecting cave temperatures? Experimental and model data from a paradigmatic case study

Abstract: This research focuses on the mechanisms that transfer the variations in surface atmospheric temperature into caves to evaluate whether they record the warming trend of recent decades. As a study case, we use the data from a hall in Postojna Cave (Slovenia), which was monitored from 2009 to 2013. The low-frequency thermal variability of this cave chamber is dominated by the conduction of heat from the surface through the bedrock. We implemented a thermal conduction model that reproduces low-frequency thermal gradients similar to those measured in the cave. At the 37 m depth of this chamber, the model confirms that the bedrock is already recording the local expression of global warming with a delay of 20–25 years, and predicts a cave warming during the coming decades with a mean rate of 0.015 ± 0.004 C year−1. However, because of the transfer of surface atmosphere thermal variability depends on the duration of the oscillations, the thermal anomalies with periods 7–15 years in duration have delay times <10 years at the studied hall. The inter-annual variability of the surface atmospheric temperature is recorded in this cave hall, although due to the different delay and amplitude attenuation that depends on the duration of the anomalies, the cave temperature signal differs significantly from that at the surface. As the depth of the cave is a major factor in thermal conduction, this is a principal control on whether or not a cave has already recorded the onset of global warming.

Use of stable isotope composition variability of particulate organic matter to assess the anthropogenic organic matter in coastal environment (Istra Peninsula, Northern Adriatic)

Abstract: Nitrogen and carbon stable isotope analysis of particulate organic matter (POM) was used to assess the impact of anthropogenically derived organic matter in coastal parts of the Istra Peninsula (Northern Adriatic). The investigation was conducted in areas potentially impacted and enriched with different amounts of organic matter. Elevated δ15N values in POM reflect enrichment of organic matter near the coast due to inadequate municipal infrastructure in cities and local septic systems as well as inputs from riverine terrestrial material. On the contrary, negative δ15N values reflect the depleting effect of purification plants. Significant differences in nitrogen stable isotope ratios were observed between western and southeastern coasts. The δ13C values show small depletion at sites with potentially greater anthropogenic impact. A weak temporal increase of δ15N from spring to late summer was observed. The results for nitrogen and carbon isotope ratios of POM and their comparisons with other areas suggest diverse amounts and sources of organic matter as well as differences in movement of floating POM within the water column. The δ15N and δ13C values reflect the ratios of marine and terrigenous organic matter, the latter being mainly anthropogenically influenced. The results finally suggest precaution in applicability of POM as tracers for detecting anthropogenic organic matter in marine coastal ecosystem.

Geochemical characterization and environmental status of Makirina Bay sediments (northern Dalmatia, Republic of Croatia)

Abstract: This research focuses on determination of the mineralogical composition, geochemical characteristics and evaluationof pollution status of the Makirina Bay sediments. Calculated enrichment factor (EF) values show no enrichment ( Cd > Pb > Ni > Zn > Cu > As. Principal component analysis (PCA) and correlation analysis confirmed the PTE distribution depends mainly on thegeogenic mineral components and anthropogenic activities in the areas surrounding the bay. Calculated transfer factor(TF) values from sediment to seagrass Cymodocea nodosa (C. nodosa) were < 1, showing that despite the results of thesequential extraction procedure, PTE transfer from sediment to roots was not effective.

The case of the carbonatite-like dyke of the Madenska River complex at the Kriva Lakavica section in the Republic of Macedonia: oxygen and carbon isotopic constraints

Abstract: The oxygen and carbon isotope compositions of carbonate samples from the carbonatite-like dyke of the Madenska River complex at the Kriva Lakavica section, samples of calcite skarns from the Damjan Fe-ore deposit and the Sasa Pb-Zn ore deposit, and samples of marbles from the Pohorje Mountains were analyzed to provide critical evidence in favor of the magmatic or sedimentary origin of this carbonatite-like dyke. We suggest that the carbonatite-like dyke is not a "normal" carbonatite, but instead represents melted carbonates, which can be associated with an unexposed, deep-seated, causative magmatic body. This dyke has a fluidal texture and carries xenoliths of ultramafic rocks that can be up to 35 cm in size. Its isotopic composition plots between primary unaltered carbonatites and marine carbonates, and ranges between 13.79? and 18.89? for Δ18OVSMOW and between -1.22? and 1.31? for Δ13CVPDB. These values are significantly lower than those observed in carbonatites analyzed during this study and range between 6.53? and 8.10? for δ18OVSMOW and between -5.82? and -4.32? for Δ13CVPDB, which is the primary isotope signature of most magmatic carbonatites. Similarly high δ18O and Δ13C values were found in skarns of the Damjan Fe deposit close to the Madanska River complex and in the Sasa Pb-Zn deposit, as well as in high-grade regional metamorphic calcitic marbles of the Pohorje massive. The emplacement levels of the carbonatite-like dyke, due to several tectonic processes, are uncertain. The type of country rocks (sedimentary carbonates, ultramafic, mafic, and granitic rocks), hydrothermal alternation, and metasomatic and regional metamorphic processes seem to be the most important parameters that affect the O and C isotopic patterns found in the Kriva Lakavica carbonatite-like dyke and in the investigated samples.