Distribution Pattern of Dioxins in Sediment Cores from the Xiangxi River, a Tributary of Three Gorges Reservoir, China

Abstract

Sediment cores were collected from the Xiangxi River, a tributary of the Three Gorges Reservoir, the deposition time in the longest sediment core (90 cm) was measured by radiometry (137Cs, 210Pb) activities and polychlorinated dibenzo-p-dioxins/furan (PCDD/F) concentrations in different depths of the sediment core were measured. The results indicated that the mean deposition rate was 1.01 cm/a. The total PCDD/F concentrations ranged from 19.28 to 70.07 pg/g d.w. with a mean of 35.06 pg/g d.w. PCDD/Fs in the 1960–1990s were higher than others, which were significantly different in the various layers and cores (p < 0.05). PCDD occupied 63.42–87.33% of PCDD/Fs, and octachlorianted debenzo-p-dioxin (OCDD) was the predominant congener. The ratio of PCDD to PCDF was 2.26–8.08. PCDD/Fs significantly correlated with total organic carbon (TOC) (p < 0.01). The toxic equivalent (TEQ) ranged from 0.15 to 0.98 pg/g d.w. No significant difference was found in TEQ (p > 0.05). It was concluded that the spatio-temporal heterogeneity determined by hydrodynamics and total organic carbon (TOC) was the distribution pattern of PCDD/Fs in the sediment cores of Xiangxi River, the concentrations of PCDD/Fs were low, with a low environmental pollution risk, and by-products of sodium pentachlorophenate might be the main source.

Historical sedimentary and evolutionary characteristics of POPs and EDCs in typical regions of the three Gorges reservoir, China

“…Zhou et al measured polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in sediment cores obtained from Xiangxi River, a tributary of the Three Gorges, using 137 Cs and 210 Pb radionuclides. They found higher concentrations of PCDDs and PCDFs in 1960–1990 compared with those in other years, confirming remarkable differences in each sediment layer [ 10 ]. Current studies primarily focus on dating sediment cores in shallow lakes and rivers and analysing the corresponding typical pollutant concentration and distribution.…”