1. Monitoring of Malodorous Compounds from a Swine Waste Lagoon by an Equilibrium Technique Monitoring of Malodorous Compounds from a Swine Waste Lagoon by an Equilibrium Technique John Loughrin 1, Nanh Lovanh 1, Arturo Quintanar 2 and Rezaul Mahmood 2 1 USDA-ARS, Bowling Green KY, 2 Dept. of Geology and Geography, Western Kentucky Univ., Bowling Green, KY Diagrammatic representation of a side view of apparatus used to stir sampler in waste lagoons. The ability to accurately track malodorous compounds in the vapor phase is an urgent need. This is usually done using Tedlar bags or adsorbent tubes as a concentration step prior to gas chromatography. There are a number of difficulties associated with these techniques however. Much of this is due to the compounds’ relatively high polarity. Most adsorbents developed for use in thermal desorption applications are non-polar, which reduces chromatographic problems associated with the co-collection of water vapor, but may cause relatively low affinity for polar volatiles. In addition to problems associated with the desorption of water vapor onto a gas chromatograph, adsorption of water may displace analytes. Moreover, polar analytes are strongly adsorbed onto the surfaces of Tedlar bags. Recently, we developed an equilibrium sampler for the measurement of malodorous compounds in water. These samplers consisted of submersible stir plates which used Gerstel Twister® stir bars to absorb volatile compounds which were subsequently analyzed by GC. With these samplers, it was possible to track changes in the concentrations of malodorous volatile compounds in a swine waste lagoon for an extended period of time. A more urgent need is the ability to accurately and reliably track the concentrations of trace malodors in the vapor phase. The purpose of this investigation, therefore, was to determine if these samplers could be used to monitor trace levels of malodorous organic compounds in the air and, if so, get estimates on detection limits and compare the results for equilibrium sampling with a more standard method, that is, entrainment of volatiles on Tenax TA with subsequent thermal desorption onto a gas chromatograph. Determination of equilibration time. Ten compounds were dissolved in CH 2 Cl 2. Two μL of this solution, containing 500 ng of each compound, was spiked onto Twisters placed into 2 mL autosampler vials. The vials were closed and placed on stir plates at room temperature and the stir bars spun for 1 hr at 300 rpm to allow adsorption. The Twisters were removed from the vials and placed in glass Petri plates. The Petri plates were then either placed on top of a stir plate and the Twisters spun at 300 rpm or without stirring and compounds were desorbed from the Twisters for 15, 30, 60, 120, 180, 240, or 300 min. At the end of each time period compounds were thermally desorbed and analyzed. The amount of compound remaining after each desorption period was expressed as a percentage of the amount present at t=0. Laboratory Comparison of Tenax Entrainment and SBSE. A standard solution containing 20 mg per mL each of phenol, p-cresol, p-ethylphenol, indole, and skatole, was prepared in methanol. Different amounts of this solution was placed in 200 mL deionized water over a 5 cm-tall bed of clean sand in a 1.8 L jar placed on the top of a magnetic stir plate in order to give final amounts of each compound ranging from 0.1 to 4 mg. Three 50 mL Erlenmeyer flasks containing a Twister stir bar were placed in the jar and three thermal desorption tubes containing 5 cm long beds of Tenax TA that had been conditioned under a stream of N 2 at 240 ºC for two h were inserted into the jar via holes in the metal lid of the jar. The lid of the jar had six holes in it to accommodate the thermal desorption tubes and allow for ventilation into the jar. Odor compounds were collected for four h and analyzed as described below. This experiment was performed twice to obtain mean values for each method of volatile compound capture. Collection of Volatile Compounds above Lagoon Surface. Portable magnetic stir plates were positioned 0.5 m and 1.5 m above a lagoon surface by mounting them on PVC floats. The floats were pulled to a position near the center of the lagoon for 4 h. After deployment, the Twisters were retrieved and placed in 2 mL vials and kept at 4 ºC until analyzed. During collection, water temperature as well as wind speed, temperature and humidity at 50 and 150 cm above the lagoon surface were recorded. Anemometers and hygrometers/temperature sensors deployed on lagoon surface Twisters and stir plates deployed 0.5 and 5 m above lagoon surface Twisters obtained equilibrium more quickly when stirred than when not so that all field analyses and laboratory Tenax-Twister comparisons were conducted using stirring. Equilibrium times ranged from 22 min for phenol to 210 min for skatole. In laboratory comparisons, the reproducibility of Tenax analyses was poor, and we were unable to obtain an estimate for the volume of air ‘sensed’ by the Twister stir bars. We therefore simply deployed the Twisters 0.5 and 1.5 m above the middle of a swine waste lagoon to obtain a relative measure of the volatilization of malodors. Plans are to continue measuring the amounts of malodorous compounds retained on the Twisters and use this to determine the relative emission from the lagoon as affected by season, weather and management practices. As part of this project, we are also measuring wind speed, temperature and humidity at two heights above the lagoon surface as well as rainfall and insolation at a weather station located near the lagoon. Plans are to continue measuring the amounts of malodorous compounds retained on the Twisters and use this to determine the relative emission from the lagoon as affected by season, weather and management practices. As part of this project, we are also measuring wind speed, temperature and humidity at two heights above the lagoon surface as well as rainfall and insolation at a weather station located near the lagoon. After subtracting background levels of malodors obtained upwind of the lagoon and swine housing, clear differences were seen between the two heights, with 2-3 fold more malodorous compounds sorbed at 1.5 m than at 1.5 m above the lagoon surface. Greater amounts of compounds were sorbed at both heights on calm days than on windier ones.