Abstract
The Lake Mir represents a small, isolated, and shallow marine lake situated in the south-eastern part of the Dugi otok Island, in a karstic landscape of the eastern Adriatic coast. The surrounding karstic background, with occasional occurrences of red soil, characterizes the sediments in the lake as coarse grained and carbonate rich. Previous studies suggested the prevailing influence of the lake bathymetry, that is, the proportion of carbonates and grain size characteristics of the sediments, on the variability of the element composition of the lake sediments. To confirm previous assumptions and obtain a better understanding of the factors influencing sediment composition of this marine lake, the distribution of rare earth elements in sediments of the Lake Mir and the nearby Telašćica Bay, as well as surrounding soils, was investigated. In the lake sediments, the sum of rare earth elements, including Y (hereinafter referred as ΣREY), ranged from 10.6 mg kg−1 to 25.3 mg kg−1; in the Telašćica Bay sediments, ΣREY were higher compared to the lake and ranged from 56.4 mg kg−1 to 85.2 mg kg−1, while the highest ΣREY, from 83.3 mg kg−1 to 227 mg kg−1, were observed in soils surrounding the lake. Despite the difference in the levels of the rare earth elements, the REY normalized patterns and associated fractionation parameters (ΣLREE/ΣHREE, (La/Yb)N, and (Nd/Yb)N) showed similarities between the lake sediments and the surrounding soils, confirming a significant influence of local lithology on the lake composition. The results of the statistical analysis, on the other hand, suggest the contribution of both the carbonate (e.g., calcite) and non-carbonate minerals (i.e., alumosilicates and Al–Fe-hydroxides) on the total REY content in the lake sediments.
Highlights
Karst regions make up around 12% of the world’s surface, and Dinaric karst, which includes the study area, is one of the biggest in Europe, extending from Slovenia to Albania
This study provides an insight into the influence of local soils on the distribution of REY in sediments of the nearby water body and suggests the possibility of differentiation between external influence and substrate, which is the main premise when determining the external source of the REY in the environment
They were found to be comparable to the average rare earth elements concentrations in terra rossa and other soils from the drainage area of the Zrmanja River estuary [15], situated in the karstic area of the eastern Adriatic coast
Summary
Karst regions make up around 12% of the world’s surface (excluding the Antarctic, Greenland, and Iceland), and Dinaric karst, which includes the study area, is one of the biggest in Europe, extending from Slovenia to Albania. Karst marine lakes represent unique and rare marine systems, formed by intrusion of sea into such karst landscape. Approximately 200 marine lakes have been documented worldwide [1,2,3,4,5,6,7,8,9]. Their uniqueness entails poor knowledge of them and understanding of ongoing geochemical processes in them, and existing literature mainly deals with biological aspects of marine lakes
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