Polychlorinated diphenyl ethers (PCDEs) are a group of halogenated aromatic compounds and serious environmental pollutants. In the present study, sediment and water samples from eight sites in Nanjing section of the Yangtze River were characterized with 15 congeners of PCDEs. Concentrations and distributions of these PCDEs in water phase and sediments were analyzed by GC/MS. Results demonstrated that ∑PCDE concentrations were higher in the low water period (1.15–1.80 μg/L) than those in the high water period (0.73–1.30 μg/L) in water phase. Moreover, ∑PCDE concentrations were higher in the low water period (1.58–3.98 μg/kg) than those in the high water period (1.24–3.48 μg/kg) in sediments. A significant linear relationship existed between the ∑PCDE concentrations and TOC contents in sediments, but a poor linearity was found between ∑PCDE concentrations and DOC contents in water phase. Furthermore, the comparison of the percentage compositions in sediments and in water phase showed that CDE-30 (2,4,6-tri-CDE) was the predominant congener in the studied sites, and higher chlorinated congeners accounted for a larger proportion in sediments than those in water phase. In conclusion, the present study demonstrated the prevalent contamination by PCDEs in sediments and water from the Nanjing section of the Yangtze River.
He Qun,Qin Li,Zhang Xuesheng,Wang Liansheng,Sun Ping,Wang Zunyao
Sediment and water samples collected from 8 sites of the Yangtze River in Nanjing section were characterized with 31 congeners of polychlorodibenzothiophenes (PCDTs). Concentrations and percentage compositions of these PCDTs in water and sediments were analyzed by gas chromatography–mass spectrometry. Results showed that ∑PCDT concentrations in sediments were higher (0.86–1.75 μg/kg) than those in water (0.56–1.30 μg/L). A linear relationship existed between ∑PCDT concentrations and total organic carbon content in sediments, whereas there was a poor linearity between ∑PCDTs concentrations and dissolved organic carbon content in water phase. Moreover, percentage compositions showed that penta-chlorinated DTs were the predominant congeners both in sediments and water. Differences existed in the percentage compositions between water and sediments. Highly chlorinated DTs accounted for a larger proportion in sediments than those in water. In conclusion, the present study showed the prevalent contamination by PCDTs in sediments and water from the Nanjing section of the Yangtze River.
Organosulfates (OSs) derived from the oxidation of biogenic volatile organic compounds (BVOCs) in the presence of anthropogenic sulfate aerosols are the important tracers of secondary organic aerosols (SOAs). In order to better understand the concentration of pinene-nitrooxy organosulfates (pNOSs) in Nanjing, a sensitive high-performance liquid chromatography-electron spray ionization spectrum/mass spectrum (HPLC-ESI-MS/MS) to determine pNOSs in PM2.5 has been developed and validated in this study. Firstly, Hypersil Gold C18 (Thermo Scientific, San Jose, USA) was selected to separate pinene-derived nitrooxy organosulfates (pNOSs) based on their polarity. Three kinds of pNOSs were detected in the full scan mode (MS) with an ESI source under the negative mode. Secondly, three isomers of pNOSs with fragment ions m/z 220, 151, and 142 were identified based on the MS/MS maps. At least two pairs of transfer ions should be selected as identification and quantification ions according to the optimization results of target compounds. For example, to determine pNOSs, these transfer ions of m/z 294 → 247, m/z 294 → 231, m/z 294 → 220, m/z 294 → 142, m/z 294 → 151, m/z 294 → 96, m/z 294 → 80 were selected as quantification and identification ions. Finally, the influence of scan mode on pNOS detection was evaluated, and the results showed that pNOSs were most sensitive in the SRM (selected reaction monitor) scan mode. Therefore, the SRM scan mode was chosen to detect pNOSs. We applied this method to analyze year-round PM2.5 (PM2.5 is fine particulate matter, which refers to particulate matter in ambient air with an aerodynamic equivalent diameter of less than or equal to 2.5 microns) samples in Nanjing. The average concentration of all the three kinds of pNOSs was 69.95 ng m−3. The results showed that the average concentration of pNOSs was high in spring (92.94 ng m−3) and summer (90.57 ng m−3), and lowest in winter (30.03 ng m−3).
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