Effect of Sample Preparation on the Sorption of Organic Pollutants to Turfgrass Thatch.

The impact of drying and grinding on the sorption of organic molecules to relatively coarse organic media is not well understood. This study was conducted to determine the effect three sample preparation procedures on the sorption of 1-naphthol and naphthalene to Kentucky bluegrass (Poa pratensis L.) and zoysiagrass (Zoysia japonica Steud.) thatch. Thatch was either passed through a 4 mm sieve in a field moisten state, or was dried at 60°C prior to being passed through a 4 mm sieve. A third sample preparation procedure consisted of taking a portion of the thatch dried at 60°C and passing it through a 2 mm sieve. Sorption isotherms for all three sample preparation procedures were determined using ¹⁴C-labeled molecules and standard batch suspension methods. Sorption was most affected by the moisture status at the time of screening. Naphthalene sorption was 32 % greater for dried thatch passed through a 4 mm sieve than for field moist thatch passed through a 4 mm sieve. The effect of thatch particle size on sorption was not clear. Comparison of passing dry thatch through 2 and 4 mm sieve produced opposite results for naphthalene and 1-naphthol. Sorption differences could not be attributed to alterations in thatch organic matter content arising from the different preparation procedures. These results stress the need to develop a standard protocol for preparing thatch in sorption investigations.