Monticchio Lakes

Risultato della ricerca: Conference contribution

Abstract

The crater lakes are a natural hazard for the population living near them because they cangenerate liminic explosions, like as the disaster of Nyos lake (Cameroon 1986), in which 1476people and thousands of animals died. Crater lakes are able to store magmatic and hydrothermalgases and solubilising them into the water. An overpressure of the dissolved gases can generatea limnic eruption. Italy is characterised by an intense volcanic and seismic activity. Evidences ofthis past volcanism are the numerous crater lakes in Lazio and Campania. The most famous areBolsena lakes, Vico, Bracciano, Monticchio lakes, Mezzano, Martignano, Albano, Nemi, Averno.The Monticchio lakes (Piccolo Lake (LPM) and the Grande Lake (LGM)) have formed in two maarslocalized in the Mt Vulture (Basilicata), a Quaternary, not active volcano, characterized byanomalous high flows of CO2 emitted by soils. They are separated by an isthmus of about 200m. The two lakes have different morphological characteristics: LPM has an area of 160.000 m2,a steep floor and a maximum depth of 38 m. The LGM has an area of 380.000 m2, and themaximum depth of 36 m in its northern part. The two lakes solubilise high level of gases. Thehigh CO2 tenors and the high values of He3/He4 isotope ratios are ascribable to a deep magmaticdegassing.In this study we investigate the physicalchemicalparameters (electrical conductivity, temperature,Eh and pH) and the chemical composition of major and traces elements along two bathymetricprofiles. Monticchio Lakes were sampled in June 2018. The samples, taken in different depth, are20 in total: ten from LMP and ten from LMG. The physicalchemicalparameters were measuredat different depth by a multiparametric probe. The major and trace elements are analyzed in thelaboratory of INGV (Istituto Nazionale di Geofisica e Vulcanologia) in Palermo.The physicalchemicalparameters show the different layers in Monticchio Lakes. In both lakesthe range of temperature is 5.6 °C and 20 °C. Lakes show different range of pH being between6.5 and 8.6 in LMP and between 6 and 7.6 in LMG. The range of Eh is between 152and 258mV and between 144mV and 141 mV. in LMG and LMP respectively, being the negative valuesin depth due to anoxia phenomenon. The two lakes have a similar thermocline layer, around 6m.In summer, the both lakes are mostly layer because the sun energy warming the surfacelayer of lake. This phenomenon makes the hot layer upper the cold layer. In LMG, the range ofelectrical conductivity varies little with depth (411 526microS/cm). Instead, in LMP, the rangeof electrical conductivity is greater ranging from 339 to 1456 microS/cm. For this reason, thehalocline is different in both lakes, In LMP, the salt concentration increases with the depth.LMP and LMG waters in LangelierLudwingclassificative plot have both bicarbonate earthalkalinecompositions. On the contrary, traces elements (Li, Be, B, Al, Ti, V, Cr, Mn, Fe, Co, Ni,Cu, Zn, As, Se, Rb, Sr, Mo, Cd, Sn, Sb, Te, Cs, Ba, Pb, Bi and U) have different characteristics. InLMP, B, V, Mn, Zn, Sr, Cr, Fe and Mn show higher concentrations respect the other traceelements. Instead in LMG, the more concentrated trace elements are Li, Ti, Cs, Rb, Ba, Fe andMn. In Both lakes’ Fe and Mn increase with the depth.
Lingua originaleEnglish
Titolo della pubblicazione ospiteAbstract Volume 4a Conferenza A. Rittmann Catania, 12-14 Febbraio 2020
Numero di pagine1
Stato di pubblicazionePublished - 2020

Serie di pubblicazioni

NomeMISCELLANEA INGV

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