Freezing As An Effective Preservation Method for Stabilization of Dissolved Ammonia and Nitrite Plus Nitrate in Low Volume Aqueous Solutions.

Analysis and collection of nitrogen (N) in leachate is important in studying the fate of fertilizers after they are applied to turfgrass. Depending on environmental factors and turfgrass management, in-situ leachate samples collected from the field tend to vary in volume, and sample volumes are often less than 20 ml. In addition, water analysis is time consuming and is usually conducted after a large number of samples are accumulated. The objective of this project was to validate the proper methodology for N preservation in low volume leachate samples during long-term storage. Freezing has been validated as a scientifically valid method for preserving leachate for ammonia-nitrogen (NH3-N), and nitrite-nitrogen plus nitrate-nitrogen (NO2-N + NO3-N) analysis. An experiment was conducted in June 2007 and repeated in August 2008 to contrast results of freezing with other commonly used preservation techniques. Percolate samples were collected from ceramic cup samplers under a turfgrass experimental area at Clemson University's Pee Dee Research and Education Center in Florence, S.C. Storage at temperatures less than -4{degree sign}C was the only method that resulted in NH3 concentrations similar to NH3 concentrations measured in immediately analyzed aliquots. Furthermore, NO2 + NO3 concentrations were similar regardless of preservation technique. Freezing low volume leachate water samples for later N analysis is an adequate method of preservation.