Distribution of phthalate esters in alluvial sediment: a case study at JiangHan Plain, Central China.

This study aimed to investigate the sources and distribution of phthalate esters (PAEs) in alluvial sediment of humid climate regions where water cycle is very active in order to reveal their behavior of transport from topsoil and/or surface water to deep sediment and groundwater. Topsoil and deeper sediment samples were collected from nine and seventeen sites in July 2007, and January 2008, respectively, from the eastern part of JiangHan Plain, Central China. On each site, samples were collected at every 20-40cm depth within the sediment profiles. Contents of 16 PAEs were detected for each sample. summation operator(16)PAEs contents in the topsoil ranged from 252.6 to 2515.7ngg(-1), with an average value of 926.8ngg(-1). Di(2-ethylhexyl) phthalate (DEHP), di-isobutyl phthalate (DiBP), di-n-butyl phthalate (DnBP), and diethyl phthalate (DEP) were the dominant PAE species. The horizontal distribution of PAEs was related to time (season), cultivation type, distance and exact position from surface water. DEP existed only on the upper layer of soil due to its rapid degradation. However, DEHP, DnBP, and DiBP could be transported downward into deep sediment even though large amount of them were lost due to biodegradation and adsorption. On the other hand, DEHP, DnBP, and DiBP could be transported into deep sediment along with the horizontal flow of shallow groundwater from surface water, such as Yangtze River, Hanjiang River, and Honghu Lake.