Characterizing chemical transformation of organophosphorus compounds by ~(13)C and ~2H stable isotope analysis

摘要

AbstractContinuous and excessive use of organophosphorus compounds (OPs) has led to environmental contaminations which raise public concerns. This study investigates the isotope fractionation patterns of OPs in the aquatic environment dependence upon hydrolysis, photolysis and radical oxidation processes. The hydrolysis of parathion (EP) and methyl parathion (MP) resulted in significant carbon fractionation at lower pH (pH2–7, εC=−6.9~−6.0‰ for EP, −10.5~−9.9‰ for MP) but no detectable carbon fractionation at higher pH (pH12). Hydrogen fractionation was not observed during any of the hydrolysis experiments. These results indicate that compound specific isotope analysis (CSIA) allows distinction of two different pH-dependent pathways of hydrolysis. Carbon and hydrogen isotope fractionation were determined during UV/H2O2photolysis of EP and tris(2-chloroethyl) phosphate (TCEP). The constant δ2H values determined during the OH radical reaction of EP suggested that the rate-limiting step proceeded through oxidative attack by OH radical on the PS bond. The significant H isotope enrichment suggested that OH radical oxidation of TCEP was caused by an H-abstraction during the UV/H2O2processes (εH=−56±3‰). Fenton reaction was conducted to validate the H isotope enrichment of TCEP associated with radical oxidation, which yielded εHof −34±5‰. Transformation products of OPs during photodegradation were identified using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS). This study highlights that the carbon and hydrogen fractionation patterns have the potential to elucidate the transformation of OPs in the environment.Graphical abstractDisplay OmittedHighlights•Concept using C and H isotope fractionation to analyze degradation of OPs is developed.•Isotope fractionation patterns upon hydrolysis and radical oxidation are comparison.•Dependence of isotope fractionation patterns on the chemical structure of OPs.•Isotope fractionation pattern has potential to study the OPs in the environment.