Water Quality of Two Glacial Alpine Italian Lakes

Abstract

The purpose of this study was to characterize, in a period of one year, two glacial lakes, Alice and Meugliano, located in an alpine reservoir on the basis of physical and chemical features. The two lakes show two periods of mixing: one in the spring and one in the autumn, so can be classified as dimictic lakes. They are characterized by pH, alkalinity, low conductivity and and quite dilute ionic concentrations. With regard to nutrients, most nitrogen occurred in the nitric form in the superficial layers. During the period of thermal stratification, in the anoxic layer NO3- decreases and NH4+ increases, confirming the activity of the anaerobic denitrificant bacteria. Total and soluble phosphorus levels show homogeneity during the cold period at different depths, while with stratification concentrations increase in the hypolimnium and metalimnium. In both lakes there is an inverse correlation between transparency and chlorophyll a. To evaluate the trophic state the conventional criteria of Nurnberg 2 and four lake trophic indices (TSIs) are used. Both evaluations suggest that the two lakes are eutrophic, with worse conditions in Alice. Deviations of the trophic states, based on the relation between TSIs, indicate that factors other than phosphorous limit the algal biomass, and that non-algal particles influence light attenuation

Multivariate analysis for spatial distribution of dissolved organic matters in a large river-type dam reservoir

“…The pH values were slightly alkaline, ranging from 7.0 to 8.0. The ascended pH at the surface layer may be explained by the algal photosynthetic activities (Zelano et al 2005). As expected, the values of DO were relatively high at the surface layers and they tend to decrease with increasing depth for the sites of S1 and S3.…”

Seasonal and Water Column Trends of the Relative Role of Nitrate and Nitrite as *OH Sources in Surface Waters

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] Nitrate and nitrite, together with DOM, are important photochemical sources of • OH radicals in surface waters. 1,14 As far as their relative role is concerned, the lower concentration values of nitrite compared to nitrate that are usually observed in surface waters [15][16][17][18] are compensated by the higher photochemical activity and sunlight absorption of nitrite. [19][20][21][22][23][24] Actually, on an equimolar basis, the combination of higher photolysis quantum yield and higher molar absorbivity in the environmental UV range of nitrite compared to nitrate makes the former around two orders of magnitude more reactive under summertime irradiation conditions.…”