High Plains Regional Climate Center


Date of this Version


Document Type



Transactions of the ASABE, Vol. 51(5): 1747-1752 (2008)


Used by permission.


Twisters, (poly)‐dimethylsiloxane‐coated magnetic stir bars, were used to measure compounds typical of swine manure malodor in air. In initial experiments, a time to achieve equilibrium was determined by preloading the stir bars with ten compounds with a range of volatilities and polarities and then monitoring their loss. The rate of loss was dependent on compound volatility, and the time for equilibrium to be attained varied widely, from 22 min for phenol to 210 min for skatole. To test whether the Twisters would respond linearly over a range of concentrations, the stir bars were placed in vented jars with solutions of compounds containing 100 to 4,000 μg each of five target malodorous compounds. Response was reasonably linear, with average coefficients of variations of 40% and coefficients of determination over 0.80 except for phenol, the most polar of the tested compounds. The Twisters were deployed on portable magnetic stir plates 0.5 and 1.5 m above the surface of a wastewater lagoon serving as the primary waste receptacle of a 2,000‐head farrowing operation. Two to three times as much of each compound was absorbed at 0.5 m than at 1.5 m. As the lagoon cooled, malodorous compounds accumulated in the lagoon, and as a consequence, greater amounts of malodors were retained on the samplers despite the cooler temperatures. These results indicate that Twisters can be used to sample malodorous compounds above air from swine waste lagoons.