RESUMO
Sodium dodecyl sulfate (SDS) is a surfactant used and recommended by regulatory agencies as a reference substance in ecotoxicological analyzes. In this work, acute toxicity assays were performed with adults and embryos of the freshwater snail Biomphalaria glabrata, an endemic organism with environmental and public health importance, to evaluate the effects of the surfactant and establish a sensitivity control chart. The organisms were exposed to SDS for 24 h to a range of concentrations, as well as a control group. Six assays were performed to establish the control chart for adults (with a median LC50 of 36.87 mg L−1) and differential sensitivity was observed at each embryonic stage (EC50 = blastulae 33.03, gastrulae 35.03, trochophore 39.71 and veliger 72.55 mg L−1). The following behavioral responses were observed in exposed adult snails: release of hemolymph and mucus, body outside the shell, and penile overexposure. Embryos at the blastulae and gastrulae stages were more sensitive, and teratogenic effects were accentuated in the trochophore stage. The difference in results obtained between adults and embryos underscore the importance of carrying out analyzes at different developmental stages. The serial assays established with SDS for B. glabrata demonstrated efficiency and constancy conditions in the assays with good laboratory practice standards. The wide distribution of Biomphalaria species in several countries, their easy maintenance and cultivation in the laboratory, in addition to ecological importance, make them economical alternatives for ecotoxicological assays.
RESUMO
Two experimental cells with household solid waste and healthcare solid waste were monitored in order to evaluate the pollution potential, and its toxicity effects corresponding to the chemical substances present in the leachates generated, correlating the physico-chemical composition with the ecotoxicity results (organisms Aliivibrio fischeri and Danio rerio). From the statistical evaluation of the physico-chemical analysis results, leachate generated in the household solid waste cell presented greater or equal values than to the healthcare solid waste cell, except for the turbidity parameter. The ecotoxicity results showed the same behaviour as that obtained with the physico-chemical analysis. A significant positive correlation was verified between chemical oxygen demand, alkalinity and ammonia nitrogen parameters with the leachate toxicity. This study concluded that healthcare solid waste presented less or equal polluting potential compared with household solid waste, and the co-disposal can be considered a viable alternative in sanitary landfills.
Assuntos
Eliminação de Resíduos , Poluentes Químicos da Água , Amônia , Análise da Demanda Biológica de Oxigênio , Resíduos Sólidos , Instalações de Eliminação de ResíduosRESUMO
This paper reports the degradation of 10 mg L-1 Ametryn solution with different advanced oxidation processes and by ultraviolet (UV254) irradiation alone with the main objective of reducing acute toxicity and increase biodegradability. The investigated factors included Fe2+ and H2O2 concentrations. The effectiveness of the UV254 and UV254/H2O2 processes were investigated using a low-pressure mercury UV lamp (254 nm). Photo-Fenton process was explored using a blacklight blue lamp (BLB, λ = 365 nm). The UV254 irradiation process achieved complete degradation of Ametryn solution after 60 min. The degradation time of Ametryn was greatly improved by the addition of H2O2. It is worth pointing out that a high rate of Ametryn removal was attained even at low concentrations of H2O2. The kinetic constant of the reaction between Ametryn and HOâ for UV254/H2O2 was 3.53 × 108 L mol-1 s-1. The complete Ametryn degradation by the Fenton and photo-Fenton processes was observed following 10 min of reaction for various combinations of Fe2+ and H2O2 under investigation. Working with the highest concentration (150 mg L-1 H2O2 and 10 mg L-1 Fe2+), around 30 and 70% of TOC removal were reached within 120 min of treatment by Fenton and photo-Fenton processes, respectively. Although it did not obtain complete mineralization, the intermediates formed in the degradation processes were hydroxylated and did not promote acute toxicity of Vibrio fischeri. Furthermore, a substantial improvement of biodegradability was obtained for all studied processes.