Análise dos efeitos fitotoxicos de sais na germinação do algodão (Gossypium herbaceum) e feijão-caupi (Vigna unguiculata) para avaliação da toxicidade aguda de um efluente têxtil fototratado

Abstract

Water bodies may contain ions, salts, hydrocarbons and other inorganic compounds that can interfere with their toxicity. One way to evaluate the toxicity of aqueous matrices is through ecotoxicological tests, among these, phytotoxicity, which consists of using seeds as test organisms to evaluate toxicity, using as parameters seed germination, root growth, among others. In this work, cotton (Gossypium herbaceum) and cowpea (Vigna unguiculata) seeds were used, germinated in petri dishes using filter paper as substrate and 4 ml of solution. The best germination conditions were defined through pilot tests and, subsequently, the sensitivity to concentrations of 0.12 M, 0.14 M, 0.16 M, 018 M of sodium chloride and 0.02 M, 0. 04 M, 0.06 M, 0.08 M and 0.10 M sodium sulfate. After this, phytotoxicity tests were carried out with real raw and phototreated textile effluent, in different dilutions, aiming to investigate its acute toxicity for the selected seeds, aiming to develop a standard protocol. Tests with salts returned EC50 values equal to 0.07 M and 0.10 M, for cotton and beans, respectively, with NaCl and values of 0.02 M and 0.05 M with Na2SO. At the concentrations mentioned above, the salts were phytotoxic to cotton and cowpea seeds, with Sodium Sulfate being more phytotoxic to the seeds. In tests with textile effluent, the raw effluent and some concentrations of the phototreated effluent enhanced the germination of cotton seeds. The raw textile effluent increased the germination rate by values above 200%, indicating the presence of ions and nutrients that favor seedling growth. In the case of bean seeds, the raw effluent interfered negatively, returning a Germination Index below 100%. As for the phototreated effluent without dilution and for dilutions of 10%, 20%, 30%, the material enhances the germination and growth of plant roots. Future studies should be carried out to evaluate its chronic phytotoxicity, with the aim of determining whether such interferences have repercussions in the medium and long term. Overall, the tests allowed us to have a general idea of the behavior of these seeds with the textile effluent and selected salts.