Effects of Land use Pattern on the Distribution of Phthalate Esters in Sediments of U-Tapao River Basin, southern Thailand

Abstract

Phthalate esters (PAEs), a group of anthropogenic organic pollutants have generated serious concern globally, due to their ubiquitous nature and hazardous effects in aquatic ecosystem. This study investigated the influence of land uses on the distribution of 6 PAEs species in sediment of U-Tapao River basin, southern Thailand. 6 PAEs species including DEHP, DBP, BBP, DiNP, DnOP and DIDP, sediments samples were collected from urban (UR), agricultural (AG), and natural field (NF) zones of the watershed and were analyzed by GC-MS. Of the 6 PAE congeners only DEHP, DBP and DINP were detected. The mean values of Ʃ3PAEs in the sediment samples collected from UR, AG and NF were 1993.33, 706.67 and 298.24 ng/g, respectively. The average concentration of PAEs in urban zones, was almost three times higher than those in Agricultural fields and 7 times higher than natural fields. Land use pattern significantly influenced the PAEs concentrations in the river basin sediments. The concentrations of PAEs indicated strong and significant positive correlations with sediment organic matter (OM), and a strong and significant negative relationship with sediment pH. The main sources of PAEs in the sediments were associated with industrial, residential, commercial and agricultural activities.  The estimated total PAEs inventory indicated 308.44 tons in period of 5 years (UR, 205.06; AG, 72.69; NR, 30.68 tons), suggesting that the contaminated sediments in the study area may be a potential source of PAEs in Songkla lake, the largest lake in Thailand. Thus, the necessity of including PAEs in the legislations and regulatory documents addressing the discharging of wastes containing hazardous pollutants into aquatic environments. Strategies for controlling PAEs pollution in the U-Tapao River basin was Proposed.