1. Environmental Science and Technology Center, Campus Caçapava do Sul, Federal University of Pampa, 96570-000, Caçapava do Sul, RS, Brazil
2. Franciscan University, 97010-032, Santa Maria, RS, Brazil
3. School of Sciences, Pontifical Catholic University of Rio Grande do Sul, 90619-900, Porto Alegre, RS, Brazil
4. Department of Physics, Institute of Physics and Mathematics, Federal University of Pelotas, 96050-500, Capão do Leão, RS, Brazil