• reaeration-rate coefficient;
  • reaeration;
  • tracer;
  • dissolved oxygen


The modified tracer gas technique is used to determine the reaeration coefficient in six different water bodies of the Itajaí River basin, three with rural land use and three in urban areas. Propane was used as the tracer gas and Rhodamine WT as the conservative tracer, providing information on dilution, mixing and dispersion. Liquefied petroleum gas was used instead of high purity propane, aimed at reducing the costs associated with the field trials. Reaeration-rate coefficients observed in the field ranged from 25.8 to 367.7 d−1. Two data sets could be observed where smaller streams had substantially larger coefficients of between 133.1 and 367.7 d−1, while the larger streams had values ​​ranging from 25.8 to 54.5 d−1. Five empirical equations were evaluated by comparing the values ​​obtained in the field. The equations proposed by Tsivolgou and Wallace and Tsivoglou and Neal showed greater adherence to the values ​​determined in the tests. Reaeration-rate coefficients obtained in the field were correlated with the hydrodynamic characteristics of the watercourses, thus establishing a mathematical function through which to obtain estimates for future evaluations. The R2 value obtained using this equation was 0.959, indicating a high correlation between the calculated values ​​and those estimated in the field. Copyright © 2012 John Wiley & Sons, Ltd.