Identification and oxidation of chlorinated paraffins containing nitrate esters, aliphatic sulfates, and thioether...

Owing to the extensive production and widespread use of chlorinated paraffins (CPs), various CP structural analogs (CPSAs) have been detected in the environment, and these hydrophobic pollutants preferentially adsorb onto sludge during treatment. However, the species and sources of CPSAs in sludge and their subsequent fate during sludge oxidation treatments remain unclear. In this study, 320 nitrogen- or sulfur-containing CPs (205 CPs-N and 115 CPs-S) were detected in sludge through an analysis of Ph₄PCl-enhanced ionization coupled with ultra-performance liquid chromatography (UPLC)-orbitrap-mass spectrometry (MS). The intensities of the newly found CPSAs were approximately 3.9-4.1 times those of CPs. Among these CPSAs, 273 previously unknown compounds, namely, 184 CPs-NO₃, 63 CPs-SO₄H, and 26 CPs-SH, were identified based on the characteristic fragments of NO₃, SO₄H, and SH, respectively. MS/MS analysis showed that the identified CPs-NO₃ included 74 CPs-NO₃, 71 CPs-NO₃-NH₂, 23 CPs-NO₃-OH, and 16 CPs-NO₃-NH₂-OH; CPs-SO₄H included 40 CPs-SO₄H and 23 CPs-SO₄H-OH; and CPs-SH could be divided into 19 2-(methylthio)acetamide-, 6 2-(methylthio)acetamide-cysteine-, and 1 N-acetylcysteine- containing CPs. High abundances of CPs-NO₃ and CPs-SO₄H were found in both sludge and CP commercial mixtures, indicating that these CPSAs likely originated from the production or use of industrial products. CPs-SH, which were present only in the sludge, were potentially derived from the biotransformation of CPs with amino acids. The oxidation of sludge resulted in the removal of 20.4-60.7 % of the newly identified CPSAs. The oxidation of CPs-NO₃ and CPs-SO₄H involved both carbon chain decomposition and hydroxylation processes, whereas CPs-SH underwent oxidation through carbon chain decomposition.