Top surface soil samples (1 in.) were collected every month from each location. The first samples were collected in October 2004 and the last samples were collected in May 2005. The samples were collected in precleaned glass jars by stainless steal spatula from each location and immediately brought to the laboratory for analysis. The soil samples were air dried on precleaned aluminum foils at room temperature (25–27๐C). The dried samples were then grinded using ceramic hand grinder. Each sample was sieved to obtain 5 gm of very fine particles (< 125 lm) before total organic matter extraction. The extraction was performed twice by adding a mixture of methylenechloride/methanol (3:1 v/v) to the sieved fine particles of each soil sample and then ultrasonicated twice for 20 min before solvent collection. Each sample was rinsed three times with the solvent mixture and passed through glass microfiber filters. Each total extract was reduced to approximately 2 ml by rotary evaporator, and then concentrated under nitrogen blow-down at room temperature to 500 ll. Aliquots of the total extracts were derivatized with BSTFA reagent before GC–MS analysis.