ABSTRACT
With the growing development of modern agriculture and industry, groundwater is facing more and more complex contaminants. One such contaminant is per- and polyfluoroalkyl substances (PFASs), which pose a potential risk to human health, particularly for those who rely on groundwater as their primary source of drinking water. In this study, we conducted a comprehensive investigation on the occurrence, spatial distribution, and source apportionment of PFASs in shallow (<60 m) and deep (>80 m) groundwater samples from a reclaimed water irrigation area in Beijing's suburbs. Our results showed that the average total PFAS concentration (∑10PFAS) for all samples was 10.55 ± 7.77 ng/L, ranging from 1.05 to 34.28 ng/L. The dominant congeners were PFBA, PFOA, and PFBS. No significant linear relationship was observed between PFAS concentrations and the well depth. However, the averaged ΣPFASs in groundwater were highest in the uppermost layer and declined sharply to a few ng/L in the deep aquifer below 80 m. PFASs showed elevated concentration in shallow aquifers in 9 out of 11 paired wells, indicating an overall descending trend of PFASs with increasing aquifer depth. The spatial distribution of PFASs was highly heterogeneous and showed different patterns in shallow and deep groundwater, which may be related to the complicated attenuation behavior of PFAS compounds when they transport and diffuse through overlapping aquifer layers. The influence of the landfill on groundwater PFASs was most pronounced within a 5 km radius. Source apportionment results indicated that reclaimed water irrigation is the main non-point source of PFASs in shallow groundwater. In contrast, deep groundwater is primarily subject to point sources and lateral recharge flow. This investigation of PFASs in shallow and deep wells provides a foundation for further exploration of PFASs transportation and risk prevention in regions where groundwater is a major water resource for domestic and industrial development.
ABSTRACT
An enantioselective method was developed for the separation and determination of three chiral hexabromocyclododecanes ( HBCDs ) including α-HBCD, β-HBCD, γ-HBCD in soil and earthworm by HPLC-ID-MS/MS. d18-HBCDs used as internal standards were added to the samples before extraction. HBCDs enantiomers were extracted from soil by accelerated solvent extraction ( ASE ) with n-hexane/DCM (1:1,V/V) at 100℃ and 10 MPa for 5 min, and further cleaned up using silica column. HBCDs enantiomers were extracted from earthworm by vortex turbulence with ethyl acetate. The extracts were orderly sulphonated by sulfuric acid, and purified by silica column. For all HBCDs enantiomers, good linearities were obtained in the concentration range of 0. 25-50 ng/mL. Limits of detection ( LOD) and limits of quantification ( LOQ) were 0. 00544-0. 00766 ng/g and 0. 0173-0. 0244 ng/g, respectively in soil. The recoveries of spiked samples at 0. 05 and 2. 5 ng/g levels were 80. 0%-95. 9% with relative standard deviations ( RSD, %) of 5. 7%-11. 9% in soil. Limits of detection (LOD) and limits of quantification (LOQ) were 0. 0103-0. 0148 ng/g and 0. 0328-0. 0471 ng/g, respectively in earthworm. The recoveries of spiked samples at 0. 1 and 5 ng/g levels were 78. 0% -94. 4% with relative standard deviations ( RSD, %) of 6. 1% -12. 2% in earthworm. This method can meet the requirements of determination of trace HBCDs in soil and earthworm.
