The occurrence and spatial distribution of phthalate esters (PAEs) in the Lanzhou section of the Yellow River.

The occurrence and spatial distribution of 22 congener phthalate esters (PAEs) in the Lanzhou section of the Yellow River were investigated using water and sediment samples collected from 12 stations along the river in August 2016 to March 2017. PAEs were determined by liquid-liquid extraction and gas chromatography-mass spectrometry. The average concentrations of PAE in the water samples during the dry and wet periods were 3236.0 ng/L and 2300.0 ng/L, and the average dry and wet periods of the PAEs in the sediments were 4238.9 ng/g and 3959.9 ng/g, respectively. PAEs were detected in all sampling sites. The six PAEs controlled by the United States Environmental Protection Agency (U.S. EPA), namely dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), di-2-ethylhexyl phthalate (DEHP), di-n-octyl phthalate (DNOP), and butyl benzyl phthalate(BBP), were detected. DMP, DEP, DBP, and DEHP accounted for more than 70% of all PAEs. In view of time distribution, PAEs concentration in the water samples of the dry season were greater than those of the wet season, but the sediments did not differ remarkably across the different periods. As for spatial distribution, the PAEs initially exhibited low concentrations in the upper reaches, high concentrations in the middle part, and low concentrations in the downstream; a health risk assessment of the six PAEs controlled by the U.S. EPA was carried out according to priority. Results showed that the carcinogenic risk value was less than 10-6, and the values of the non-carcinogenic compound risk index were less than 1, indicating the absence of carcinogenic damage to organisms or humans.