N. Degli Innocenti

Non-equilibrium properties of fluid interfaces - Aperiodic diffusion-controlled regime. 1. Theory

Abstract Surface relaxation processes of liquid solutions, under not-far-from-equilibrium conditions, are interpreted from a phenomenological point of view by application of the theory of distributed systems. In the case of diffusion-controlled adsorption, exact analytical expressions describe the transient responses of bulk concentration and dynamic surface tension, consequent to trapezoidal pulses of relative surface area. The mathematical treatment shows that surface responses have a definite physical significance, as they manifest a constitutive property of the system, i.e. the surface dilational modulus.

Non-equilibrium surface thermodynamics. Measurement of transient dynamic surface tension for fluid—fluid interfaces by the trapezoidal pulse technique

Abstract The trapezoidal pulse perturbation is shown to be an attractive procedure for the measurement of dynamic properties of fluid—fluid interfaces. The surface response characterizes the surface relaxation behavior well. Theoretically, this procedure has foundations within the framework of linear non-equilibrium thermodynamics. From the experimental point of view, the procedure offers the possibility of checking the experimental reliability and exhibits practical aspects due to the short duration of the surface response. Benefits are also evident in data processing.

Air-Sea Exchange: Sea Salt and Organic Microcomponents in Antarctic Snow

Abstract A characterization of surface active fluorescent organic matter (SAFOM) in Antarctic snow is carried out. Its Fulvic Acids (FA) nature is confirmed. Its enrichment in the smallest aerosol particles is shown. A tentative explanation of the presence of both natural and man-made organic microcomponents (SAFOM-interacting) is given in terms of marine aerosol transport. Their enrichment ratio appears of the same order as that of SAFOM, and their presence in the atmospheric particulate of marine origin supports the hypothesis on the transport of microcomponents in Antarctica “via marine aerosol”.

Nonequilibrium properties of fluid interfaces: aperiodic diffusion-controlled regime 2. Experiments

Abstract We have investigated the surface dilational properties of a submicellar aqueous solution of n -dodecyldimethyl-phosphine oxide. We compared (a) the steady-state responses of dynamic surface tension, induced by small-amplitude harmonic disturbances of surface equilibrium (at different frequencies), and (b) the transient response induced on the same sample by a single trapezoidal-pulse disturbance. Using the equations for a diffusive model, we determined the fit parameters from the observed response values both in the frequency and in the time domains. The results enabled us to predict satisfactorily the harmonic dynamic behaviour of the surface, from the relaxation data. The prediction-bservation agreement supports the theoretical treatment and, in particular, the assertion that the viscoelastic link, between surface excitation and response, is a constitutive property of a liquid solution. The experiments also show the existence of a linearity range and the repeatability of measurements.

Spectrofluorimetric Evidence of the Transport of Marine Organic Matter in Antarctic Snow Via Air-Sea Interaction

Abstract This paper considers the importance of marine aerosol in the atmosphere. As a consequence of its peculiar generation mechanism, it is also considered as a possible contributor to the transport of man-made microcomponents via air-sea interaction, especially in remote sites. In view of future marine aerosol studies, the dominant presence of marine aerosol components in coastal Antarctic snow is discussed the presence of fluorescent marine organic matter in Antarctic snow is shown. Its “marum” nature is evidenced. We give a tentative interpretation of the experimental data, and make a hypothesis concerning the variations in marine aerosol composition in correspondence to various altitudes.

Detergents as a condition of pollution from coastal marine aerosol

Abstract Experimental evidence of damage of a Pinus pinea foliage by detergent surfactants in aerosol from marine water solutions is shown. Typical natural non-detergent surfactants from the coastal marine environment, such as humic acids, do not cause per se damage although they could become a vehicle of polluting agents in marine aerosols. Taking into account that the damage mechanism due to the detergents can be generalized to all type of coastal vegetation, this damage is suggested in a first instance as an indication of marine pollution.

Humic Compounds in Seawater and Marine Sediments from Antarctica

Abstract This paper reports the results of various types of analysis and physico-chemical characterization of several samples of humic compounds extracted from Antarctic seawater and marine sediments. Several features of Antarctic humic compounds are evidenced. In seawater only fulvic acids are present. Fluorescence spectra of filtered seawater are similar to those of aquatic fulvics extracted from the same location. In sediments, only humic acids are present; they are characterized by a high aliphatic fraction and large quantities of aminoacids, as shown by NMR and IR. The particulate is a mixture of inorganic and organic matter, the latter consisting of proteinaceous material, carbohydrates and lipids.

A simple model for K and Ca enrichment interpretation in Antarctic snow

Abstract The presence of surface active fluorescent organic matter (SAFOM) in Antarctic snow, similar to the marine matter, suggests that micro components present at the sea surface, capable of interacting with SAFOM, may be transported via marine aerosol. Experimental evidence is given by the enrichment of SAFOM in the smallest marine aerosol particles and by the interaction of K and Ca with SAFOM. The surfactant concentration at the sea surface during large whitecaps coverage is also studied. A hypothesis for the K and Ca excess, evidenced in Antarctic snow at high altitudes is proposed by means of a spray drop adsorption layer model (SDALM). This model is the result of an improved analysis of the breaking wave process, and of additional experimental findings. It seems to justify the excess concentration of K and Ca with respect to that expected for marine water compositions in high altitude snow in Antarctica. It may also constitute a more general basis for the interpretation of the fine fraction aeros...

Study of Humic Fractions from Water of an Antarctic Lake

Soluble humic compounds isolated from water of an Antarctic lake have been characterized by IR, NMR spectrophotometry and fluorimetric measurements. Gel chromatography on Sephadex G resins of fulvic acids, present in the water in high concentration, has evidenced that a great fraction of them consists of compounds having molecular weight greater than 50,000 dalton. The high level of humics and the presence in soluble form of compounds having high molecular weight and similar structure to the humic acids of lake sediments may be due to the high pH value of the water examined.