TOXICITY OF AZO DYES CONGO RED AND ALIZARINE YELLOW R ON PLANT AND AQUATIC ORGANISMS

PADILLA CLAUDIA; MAGALLANES NOGUERA CYNTHIA; KURINA SANZ MARCELA; GIANNINI, FERNANDO A.; BONILLA JOSE

Congreso; XL Reunión Científica Anual de la Sociedad de Biología de Cuyo; 2022

The textile industry is the second most polluting and generates wastewater that contains a wide variety of chemical contaminants and large quantities of dyes. Because of photolytic and thermal stability, along with resistance to biodegradation, textile dyes remain in the environment for a long time. Among them, azo dyes are the largest and most versatile group, accounting for 80% of all dyes used in textile industries. Bioremediation is a sustainable and eco-friendly technology to treat this type of pollution. The knowledge of the toxic effects of dyes is a key requirement to propose future strategies for environmental sanitation. For these reasons, the objective of this work is toevaluate the toxicity of the azo dyes Congo Red (C32H22N6Na2O6S2, 696.66 g mol-1) and Alizarine Yellow R (C13H8N3NaO5, 309.21 g mol-1) toward different model species that represent relevant ecological functions. The phytotoxicity of the azo dye aqueous solutions (25, 50, 75 and 100 µg mL-1) was evaluated using Lactuca sativa L. seeds after 120 h exposure by analyzing the Absolute Germination (GA) and the Germination Index (GI), which also takes into account the length of the radicle and hypocotyl. Likewise, we determined the average growth-inhibition of roots in Allium cepa after 72 h. Additionally, the toxicity of the azo dyes was evaluated on Danio rerio fertilized eggsafter 96 h. The arithmetic means were evaluated through ANOVA, p=0.05 (IBM SPSS Statistics v24). Although Congo Red did not significantly inhibit germination or radicle and hypocotyl elongation of L. sativa L. at all concentrations tested, it inhibited around 50% the roots length in A. cepa from 50 µg mL-1 onwards. The dye caused 100 % mortality of D. rerio fertilized eggs from 75 µg mL-1 onwards at 96 h. On the other hand, Alizarine Yellow R inhibited between 20-30 % the germination of L. sativa L. seeds from 75 µg mL-1 onwards and was moderately toxic in terms of radicle and hypocotyl elongation (GI ~ 75 %). This dye inhibited 50 % the roots elongation in A. cepa when present at 100 µg mL-1, while it caused total mortality of D. rerio eggs at 50, 75 and 100 µg mL-1 after 96 h. These results position both textile azo dyes as targets for the development of removal and biodegradation processes with competent organisms to minimize risks for human health and the environment.