The occurrence, composition and partitioning of phthalate esters (PAEs) in the water-suspended particulate matter (SPM) system of Lake Chaohu, China

Highlights: • Σ₆ PAEs in water and SPM phases exhibited different seasonal trend. • The occurrence of PAEs exists significant spatial difference between lake and estuary. • DIBP and DBP were the abundant PAEs in Lake Chaohu. • DIBP should attract more attention in the future. • The Kow model may be inappropriate to predict the partitioning of PAEs in natural large lakes. -- Abstract: The occurrence, composition, and partitioning of six phthalate esters (PAEs) (dimethyl phthalate (DMP), diethyl phthalate (DEP), diisobutyl phthalate (DIBP), dibutyl phthalate (DBP), butyl benzyl phthalate (BBP) and di(2-ethylhexyl) phthalate (DEHP)) in the water-suspended particulate matter (SPM) system of Lake Chaohu were investigated in this study. Our results showed that PAEs were ubiquitous contaminants in Lake Chaohu. The concentration of the Σ₆ PAEs in dissolved and particulate phases ranged from 0.370 to 13.2 μg·L⁻¹ and from 14.4 to 7129 μg·L⁻¹, respectively. The Σ₆ PAEs in water and SPM phases exhibited different seasonal trends. PAEs with different degrees of hydrophobicity demonstrated different temporal distributions in the dissolved phase. In particulate phase, all PAEs exhibited the same temporal distribution. Regarding the occurrence of PAEs, significant spatial differences exist between lake and estuary. However, there were no specific differences in PAEs across lake zones and river types of Lake Chaohu. River input should be considered an important source of PAEs in Lake Chaohu. DIBP and DBP were the most abundant PAEs in Lake Chaohu, and DIBP should attract more attention in the future. The organic carbon normalized partitioning coefficient (logKoc) ranged from an average of 2.38 ± 0.86 L·g⁻¹ for BBP to 3.98 ± 0.66 L·g⁻¹ for DEHP, and approximately 2 to 3 unit variations of logKoc existed for the individual PAEs. It was difficult to ascertain whether the partitioning of PAEs was in, near or far from the equilibrium. No linear relationship was found between logKoc and the octanol-water partitioning coefficient (logKow) for PAEs. Koc might not be suitable for describing the partitioning of PAEs in the water-SPM system. The hydrophobicity of PAEs may have little impact on their partitioning in the complex environmental system, and the Kow model may be inappropriate to predict the partitioning of PAEs in natural large lakes.