Polycyclic aromatic hydrocarbons in surface sediments of Pinghai Bay, a subtropical semi-enclosed embayment in China: Distribution, source apportionment, and ecological risk assessment.

Abstract

This study investigated the occurrence, spatial distribution, source apportionment, and ecological risk of 16 priority polycyclic aromatic hydrocarbons (PAHs) in surface sediments of Pinghai Bay, a typical subtropical semi-enclosed bay in Fujian, China, is increasingly subjected to anthropogenic pressures from intensive aquaculture, offshore wind farm activities, and coastal urban development. However, systematic data on the occurrence, sources, and ecological risks of PAHs in its surface sediments remain scarce, hampering effective environmental management. Twenty-five sediment samples were collected in November 2024 and analyzed using gas chromatography-mass spectrometry (GC-MS). Total PAH concentrations ranged from 20.6 to 206.2 ng/g dw (mean 70.4 ng/g dw), indicating a low overall contamination level. PAHs exhibited a distinct nearshore-high, offshore-low distribution pattern, with the high-concentration zone (stations P01-P06, > 100 ng/g dw) primarily associated with intensive coastal human activities including domestic coal combustion in coastal villages, small fishing vessel operations, and agricultural runoff from terrestrial streams flowing into the bay. Three-ring PAHs were the most abundant (45.58%), implying mixed sources from petroleum release and combustion processes. PAH concentrations were moderately and significantly positively correlated with TOC (R2 = 0.43, p < 0.01). Integrated ecological risk assessment based on Effects Range-Low/Effects Range-Median, Mean Effects Range-Median Quotient, Toxic Equivalents and Risk Quotient consistently indicated low ecological risk across the study area, with marginally elevated risk in nearshore zones. These results provide valuable baseline data for pollution control and environmental management of subtropical small- to medium-sized semi-enclosed bays.