We collected a sediment core from the 6th (6J) Triglav Lake, a remote mountain lake in NW Slovenia, and analysed it for 25 elements, using
k
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-instrumental neutron activation analysis (
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-INAA). ...For Hg, we used cold vapour atomic absorption spectrometry (CVAAS). Data were analysed using Principal Component Analysis (PCA). PCA indicated several distinct groups of elements and sediment core samples. Ca distribution was entirely different from all other sediment components. Ba, Br, Hg, Sb and Zn were associated with organic matter (OM), with Hg showing the strongest affinity to OM. As, Cr, Fe and U formed a group of redox-sensitive elements. Two events that occurred ca. 1915 and in the 1940s/1950s, were identified in the core. They were associated with increased inputs of allochthonous material into the lake, and significantly affected the stratigraphic distributions of all elements. Some trace elements, such as As, Hg and Zn, are probably effectively retained in the catchment, whereas Cr tends to be readily exported from the catchment. Atmospheric deposition affected not only elements of anthropogenic origin (As, Ba, Br, Hg, Sb, Zn and Cr) that started to increase after the 1970s, but also those of terrestrial origin (Ca, Fe, Na). Introduction of fish into the lake in 1991 and the subsequent increase in primary production, affected the distribution of Ca and elements that are redox-sensitive and/or associated with OM (As, Ba, Fe, Sb, U, Zn). Fe minerals in uppermost 6J sediments have a strong influence on the distribution of several trace elements. As and Zn closely tracked Fe, whereas Sb was likely released after oxidation. Climate change could also have enhanced inputs of elements from the catchment, but such changes were likely overwhelmed by the effects of increased eutrophication.
Increased eutrophication was recently observed in the 5th (5J) and 6th (6J) Triglav Lakes, two remote Slovenian mountain lakes. Sediment phosphorus (P) pools were analysed and potential external P ...sources affecting the lakes (atmospheric deposition, terrestrial export and nearby hut) evaluated, to assess the effects of internal and external changes on the lakes. A sequential extraction procedure was used to quantify five P fractions from the sediments: adsorbed (NH
4
Cl–P), redox-sensitive (BD–P), aluminium- (NaOH–P) and calcium- (HCl–P) bound, and refractory organic (Res–P) P. Total phosphorus (TP) contents in surface sediment of 5J and 6J were 1430 and 641 µg P g
−1
dry weight sediment (dw), respectively. TP varied with depth in 5J sediments, but displayed no discernible pattern, whereas it decreased steadily downcore in 6J. Contents of all P forms were distinctly higher in 5J than 6J, but their rank order and relative abundances were similar in the two lakes. Res–P was the most abundant P fraction, followed by HCl–P. Together, the two P forms accounted for nearly 80 and 90% of TP in 5J and 6J sediments, respectively. BD–P and NaOH–P were less abundant, with each fraction accounting for 3 to 9% of TP, whereas NH
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Cl–P was least abundant. Atmospheric deposition and terrestrial export were substantial sources of P for the lakes. Delivery of the former was estimated to be at least 7.5 mg P m
−2
yr
−1
and the latter around 20 mg P m
−2
yr
−1
. We concluded that P was not retained in the catchment effectively, likely because of only slightly acidic soil pH (5.9), relatively low aluminium content and high organic matter content (53%) in soils, resulting in higher vulnerability of the studied lakes to eutrophication. The mountain hut could also be a significant source of P for the lakes. Each year, it could potentially contribute ~12 kg of soluble P to the environment, but the true impact of the hut on lake trophic status remains unclear.
Several geological and geochemical parameters were determined in the sediments of the 5th (5 J) and 6th (6 J) Triglav Lakes, Julian Alps (NW Slovenia), in order to study the impact of natural ...catchment characteristics and anthropogenic activity. Fish were introduced into both lakes in 1991 and a mountain hut lies on the shore of 5 J. Sedimentary grain size (GS) was distinctly coarser in 5 J than 6 J, with arithmetic means ranging between 46 and 60 and 23–36 μm, respectively. In contrast, the mineralogical composition of the two sediments was similar. Calcite predominated strongly, comprising more than 77 % of total minerals, while dolomite and quartz were rare. Organic carbon (OC) and total nitrogen (TN) concentrations were highest in surficial sediments, with levels of 14.4 and 1.8 %, and 19.3 and 2.4 % observed in 5 J and 6 J, respectively. C/N ratios (atomic) were lowest in the same surface sediments, with the two lakes characterized by similar values (9.6 vs. 9.4, respectively), suggesting a predominance of autochthonous organic matter (OM) in both lakes. Contemporary δ¹³C values were lower in 5 J (−21.0 ‰) than 6 J (−18.5 ‰) sediments. Considerable changes in these four parameters were observed in recently deposited material, reflecting a shift in the trophic status of both lakes that was likely induced by the introduction of fish. In addition, the smaller and shallower 6 J seemed to respond to changes faster than the larger and deeper 5 J, indicating the higher sensitivity of the former. δ¹⁵N values in surface sediments of 5 J and 6 J were −2.9 and −4.4 ‰, respectively, with levels increasing gradually with depth to approximately +1.0 ‰ in deeper sediments. The observed changes could most likely be attributed to the atmospheric deposition of reactive nitrogen. The mountain hut has seemingly not had a significant enough impact on the lakes to be recorded in their sediments.
