Occurrence of pentachlorophenol in surface water from the upper to lower reaches of the Yangtze River and treated water in Wuhan, China

Abstract

Pentachlorophenol (PCP), a persistent organic pollutant, has been banned in many countries, but it is still used in China as a wood preservative, molluscicide, or reagent for fish-pond cleaning, which may pose risks to the ecosystem and humans. However, data on the occurrence of PCP in the environment are scarce in the recent decade. The Yangtze River was regarded as a priority area of PCP pollution according to previous documents. This study aimed to examine the spatial distribution of PCP in the Yangtze River water, the differences in dry and wet seasons, the ecological risk for aquatic organisms, and its removal efficiency in tap water treatment plants. The river water samples (n = 144) were collected from the upper, middle, and lower reaches across ten provinces (or municipalities) in December 2020 and June 2021, respectively. PCP was detected in 88.9% of all the samples, ranging from <MDL to 9.97 ng/L. Spatial distribution differences among the involved provinces were observed, with the highest PCP concentration in the Chongqing section (median: 1.61 ng/L), followed by Hubei (median: 0.23 ng/L), Jiangxi (median: 0.23 ng/L), Shanghai (median: 0.21 ng/L), and other provinces (<0.20 ng/L). The surface water from Qinghai had the lowest concentrations (median: <0.01 ng/L). PCP levels in the Yangtze River water were much lower than those reported in water samples worldwide a decade ago. PCP concentrations in the dry season were higher than in the wet season (p < 0.001). Ecological risk assessment suggested a low risk (RQ_Max: 0.02) to aquatic organisms posed by PCP in the river. In addition, 100% removal of PCP in tap water treatment plants was observed, while the transformation products of PCP need further studies. The risk of human exposure to PCP through water ingestion only was negligible. However, human exposure risks of PCP in highly contaminated areas still require attention, considering its bioaccumulation and biomagnification in the environment.

Keywords: Pentachlorophenol; Removal; Seasonal difference; Spatial variations; Surface water; Yangtze River.