Characterizing the Organohalogen Iceberg: Extractable, multi-halogen mass balance determination in municipal wastewater treatment plant sludge

Abstract

The large number and diversity of organohalogen compounds (OHCs) occurring in the environment poses a grand challenge to analytical chemists. Since no single targeted method can identify and quantify all OHCs, the size of the OHC iceberg may be underestimated. We sought to address this problem in municipal wastewater treatment plant (WWTP) sludge by quantifying the unidentified fraction of the OHC iceberg using targeted analyses of major OHCs together with measurements of total- and extractable (organo)halogen (TX and EOX, respectively; where X=F, Cl, or Br). In addition to extensive method validation via spike/recovery and combustion efficiency experiments, TX and/or EOX were determined in reference materials (BCR-461 and NIST SRMs 2585 and 2781) for the first time. Application of the method to WWTP sludge revealed that chlorinated paraffins (CPs) accounted for most (~92%) of the EOCl, while brominated flame retardants and per- and polyfluoroalkyl substances (PFAS) accounted for only 54% of the EOBr and 2% of the EOF, respectively. Moreover, unidentified EOF in non-polar CP extracts points to the existence of organofluorine(s) with physical-chemical properties unlike those of target PFAS. This study represents the first multi-halogen mass balance in WWTP sludge, and offers a novel approach to prioritization of sample extracts for follow-up investigation.

Pharmaceuticals Account for a Significant Proportion of the Extractable Organic Fluorine in Municipal Wastewater Treatment Plant Sludge

“…Our initial targeted analysis reported six out of 16 target perfluoroalkyl acids (PFOS, PFDA, PFUnDA, PFDoDA, PFTrDA, PFTeDA; ∑ 16 PFAS = 12.5 ng/g) which together accounted for ∼2% of the EOF. Suspect screening in the present study revealed an additional seven “conventional” PFAS: 5:3 FTCA (CL1), 6:2 diPAP (CL1), EtFOSAA (CL1), MeFOSAA (CL1), and H-PFOS (CL4), which occurred at concentrations ranging from 0.07 to 11.9 ng/g dw, and 8:2 diPAP and 6:2/8:2 diPAP (both CL1), which were detectable but below quantification limits (Table ; Figure ).…”

“…Closing the Organofluorine Mass Balance in Municipal WWTP Sludge. While suspect screening together with (semi)quantification increased the percentage of known EOF from ∼2% 22 to ∼27% in Henriksdal WWTP sludge, a large proportion (∼73%) of the EOF remains unidentified. The source of the remaining unidentified organofluorine is unclear, but may include additional pharmaceuticals, pesticides and TPs not captured by our workflow.…”

“… a Selected MS2 fragments are presented here; extracted ion chromatograms and MS2 spectra are available in the SI. b Quantification method: Q = quantification with authentic standard (non-IS corrected), semiQ = semiquantification with parent compound standard, Q+IS = quantification with authentic standard (IS-corrected), semiQ+IS = semiquantification with structurally similar compound (IS-corrected). c CE – collision energy. d CL – confidence level according to Schymanski et al e From MassBank library. f From Tovar-y-Romo et al and Kim et al g From Danielak et al h No fragments at 35 CE; fragments derived using stepped collision energies: 10–35–60–90–120–150. i Although no MS2 spectrum was acquired, CL1 was assigned after confirmation of retention time and exact mass using standard, along with prior experience detecting these substances in WWTP sludge (where MS2 data were collected). All EICs and MS2 spectra are presented in the SI. j Target PFAS reported in our previous organofluorine mass balance study …”

“…10,11 Large quantities of unidentified organofluorine have already been observed in various samples, including consumer products, 12−15 human blood, 10,16−18 biota, 19,20 and sewage sludge. 21,22 Fluorine-containing pharmaceuticals and pesticides used throughout society may represent an important source of unidentified organofluorine, in particular, in wastewater treatment plant (WWTP) samples. It is estimated that between 18% and 25% of all approved pharmaceuticals since 1991, and ∼16% of registered pesticides, contain at least one fluorine atom.…”

“…The total number of PFAS is estimated to be between 4730 and 6.2 million substances, depending on definition and commercial relevance. − Considering the size of this chemical class, there are growing concerns that the environmental burden of PFAS may be underestimated. Fluorine mass balance experiments seek to address this uncertainty by quantifying the fraction of unidentified extractable organofluorine (EOF) in samples, using a combination of target analyses and total fluorine measurements. , Large quantities of unidentified organofluorine have already been observed in various samples, including consumer products, − human blood, ,− biota, , and sewage sludge. , …”