Ash leachates from some recent eruptions of Mount Etna (Italy) and Popocatépetl (Mexico) volcanoes and their impact on amphibian living freshwater organisms

Abstract

Leaching experiments were carried out on fresh ash samples from Popocatépetl 2012, Etna 2011, and Etna 2012 eruptions, in order to investigate the release of compounds in both double-deionized and lake (Lake Ohrid, FYR of Macedonia) waters. The experiments were carried out using different grain sizes and variable stirring times (from 30 min to 7 days). Results were discussed in the light of changing pH and release of compounds for the different leachates. In particular, Etna samples induced alkalinization, and Popocatépetl samples induced acidification of the corresponding leachates. The release of different elements does not show correlation with the stirring time, with the measured maximum concentrations reached in the first hours of washing. General inverse correlation with grain size was observed only for Na+, K+, Cl-, Ca2+, Mg2+, SO2-4 , and Mn2+, while the other analysed elements show a complex, scattering relationship with grain size. Geochemical modelling highlights leachates' saturation only for F and Si, with Popocatépetl samples sometimes showing saturation in Fe. The analysed leachates are classified as undrinkable for humans on the basis of European laws, due to excess in F-, Mn2+, Fe, and SO2-4 (the latter only for Popocatépetl samples). Finally, the Etna 2012 and Popocatépetl leachates were used for toxicity experiments on living biota (Xenopus laevis). They are mildly toxic, and no significant differences exist between the toxic profiles of the two leachates. In particular, no significant embryo mortality was observed; while even at high dilutions, the leachates produced more than 20% of malformed larvae

Sedimentological processes and environmental variability at Lake Ohrid (Macedonia, Albania) between 637 ka and the present

“…The high TOC / TN ratios are therefore most likely a result of early digenetic selective loss of N (cf. Cohen, 2003). The aquatic origin of the OM in the sediments of the deep basin of Lake Ohrid is also in agreement with the results of Rock Eval pyrolysis from the nearby LINI drill site (Lacey et al, 2015a; see Fig.…”

“…Mixing also leads to oxidation of OM at the sediment surface and, thus, to lower TOC contents. TOC preservation in the sediments can also be modified by lake-level fluctuations, as oxidation of OM starts in the water column during settling (Cohen, 2003;Stockhecke et al, 2014b). However, distinct climate-induced lake-level fluctuations such as, for example, described for the Younger Dryas at Lake Van in Turkey (Wick et al, 2003;Stockhecke et al, 2014b, and references therein) have not been observed at Lake Ohrid in previous studies covering the last glacial-interglacial cycle (cf.…”

“…3). The TOC content can be used as an indicator of the amount of finely dispersed organic matter (OM) in lacustrine deposits (e.g., Cohen, 2003;Stockhecke et al, 2014b). In the sediments of lithotype 1, bright colors (greenish grey) are commonly correlated with massive layers and are indicative of high calcite and low OM contents.…”

The environmental and evolutionary history of Lake Ohrid (FYROM/Albania): interim results from the SCOPSCO deep drilling project

“…High-resolution studies of diatoms in both lake sediment records indicate little evidence for a response of the diatom community related to the H4 event, but they do show a clear and rapid change following tephra deposition . This strong change is likely due to fertilisation and the availability of nutrients, particularly silica, such as it was shown in laboratory studies and leaching experiments of tephra with Lake Ohrid water (D'Addabbo et al, 2015). After the initial response, diatom community compositions in lakes Ohrid and Prespa returned to their quasi pre-disturbance state.…”

“…Cvijić, 1911;Aliaj et al, 2001;Dumurdzanov et al, 2004;Reicherter et al, 2011;Lindhorst et al, 2015). There is little consensus on the limnological origin of the lake itself, however.…”