The objective of this study was to (1) measure the concentration of four anions (Cl-, F-, NO and SO ) and nine other elements (Al, Ba, Ca, K, Mg, Mn, Fe, Ni, and Si) in two nontraditional biopolymeric chemical stabilizers (EBCS1 and EBCS2), (2) investigate consequent environmental toxicity risk implications, and (3) create awareness regarding environmental health issues associated with metal concentration levels in enzyme-based chemical stabilizers that are now gaining widespread application in road construction and other concrete materials. Potential ecotoxicity impacts were studied on aqueous extracts of EBCS1 and EBCS2 using two thermodynamic properties models: the Pitzer–Mayorga model (calculation of the electrolyte activity coefficients) and the Millero–Pitzer model (calculation of the ionic activity coefficients). Results showed not only high concentrations of a variety of metal ions and inorganic anions, but also a significant variation between two chemical stabilizing mixtures. The mixture (EBCS2) with the lower pH value was richer in all the cationic and anionic species than (EBCS1). Sulfate ( ) concentrations were found to be higher in EBCS2 than in EBCS1. There was no correlation between electrolyte activity and presence of the ionic species, which may be linked to a possible high ionic environmental activity. The concentrations of trace metals found (Mn, Fe, and Ni) were low compared to those of earth metals (Ba, Ca, K, and Mg). The metal concentrations were higher in EBCS1 than in EBCS2. Data suggest that specific studies are needed to establish “zero” permissible metal ecotoxicity values for elements and anions in any such strong polyelectrolytic enzyme-based chemical stabilizers.

Orientador: Geraldo de Freitas Maciel / Resumo: Esta pesquisa tem como principal objetivo verificar experimentalmente a presença de instabilidades na superfície livre de escoamentos lamosos, em canal com 10 metros de comprimento. Estes escoamentos, quando em condições favoráveis de vazão e inclinação, podem constituir um domínio favorável à geração de roll waves, instabilidades que evoluem adquirindo característica periódica e que se propagam com amplitudes, comprimentos e velocidade de propagação bem definidas. O fluido teste utilizado nos ensaios foi uma mistura de água+argila caulinítica (representativo do material lamoso em desastres naturais), confeccionada com uma concentração em volume de 25% e caracterizada reologicamente pelo modelo de Herschel Bulkley. Foram testados dois surfactantes (estabilizantes químicos), Tween 80 e goma xantana, para estabilizar os parâmetros reológicos da mistura, tendo a goma xantana garantido maior tempo de estabilização. A aferição da superfície livre foi realizada por meio de sistema não-intrusivo (transdutor ultrassônico), que se mostrou eficiente para aferição de ondas íngremes e de pequenas amplitudes. Os resultados de ensaios experimentais exploratórios foram confrontados com o modelo matemático 1D desenvolvido pelo grupo de pesquisa. / Abstract: This project has as main objective to experimentally verify the presence of instabilities in the free surface of muddy flows in a ten meter long channel. These flows, when situated under favorable flow and slope conditions may constitute a favorable domain for the generation of roll waves, instabilities that evolve acquiring periodic characteristics and propagate itself with well-defined amplitudes, lengths and velocity. The test fluid used in the experiment was a mixture between water + kaolinitic clay (representative of the muddy material in natural disasters), made with a 25% volume concentration and rheologically characterized by the Herschel Bulkley model. Two surfactants (chemical stabilizers), Tween 80 and xanthan gum, were tested to stabilize the rheological parameters of the mixture, with the xanthan gum ensuring longer stabilization time. The free surface measurement was performed using a non-intrusive system (ultrasonic transducer), which proved to be efficient for the measurement of steep waves with small amplitudes. The results of exploratory experimental tests were compared with the 1D mathematical model developed by the research group. / Mestre