Distribution and ecological risk assessment of phthalic acid esters in surface sediments of three rivers in Northern Vietnam

Pollution status and distribution characteristics of ten typical phthalic acid esters (PAEs) were investigated in 36 sediment samples collected from three rivers in Northern Vietnam from June to October 2020. The total concentrations of PAEs in sediment samples collected from the To Lich River (n = 9), the Nhue River (n = 12), and the Day River (n = 15) were in ranges of 11,000–125,000 ng/g-dwt (mean/median: 50,000/42,200 ng/g-dwt), 2140–89,900 ng/g-dwt (mean/median: 29,300/20,700 ng/g-dwt), and 1140–43,100 ng/g-dwt (mean/median: 13,800/10,400 ng/g-dwt), respectively. Among ten PAEs studied, di-(2-ethylhexyl) phthalate (DEHP) was found at the highest levels in all samples meanwhile dimethyl phthalate (DMP), diethyl phthalate (DEP), and dipropyl phthalate (DPP) were detected at low frequency and concentration. Significant correlations have existed between the median-chain (C4–C7) PAE pairs in sediment samples. Due to the high accumulation in the sediments, the median-chain PAEs had a higher ecological risk than the short-chain (C1–C3) PAEs. These contaminants may present a longstanding influence on organisms and ecosystems.