The Possible Production of Harmful Intermediates Is the “Dark Side” Of the Environmental Photochemistry of Contaminants (Potentially Adverse Effects, And Many Knowledge Gaps)

Reactivity of Chlorine Radicals (Cl• and Cl2•–) with Dissolved Organic Matter and the Formation of Chlorinated Byproducts

“…The formation mechanisms include the direct chlorine addition to DOM and the sequential formation from the nucleophilic reactions between the DOM intermediates (DOM •+ or DOM­(-H) • ) and Cl • , Cl 2 •– , or Cl – . Considering the numerous sources of DOM intermediates in the presence of AOPs and the ubiquitous Cl – in environmental-relevant waters (e.g., ∼10 –4 M in natural waters), , the contribution of nucleophilic reactions to the chlorinated byproduct formation may not be negligible and needs further evaluation in future research. Under typical Cl • (3 × 10 –15 – 3 × 10 –12 M·s) and Cl 2 •– exposure (3 × 10 –13 – 3 × 10 –10 M·s) in AOP processes (e.g., UV/H 2 O 2 , UV/persulfate, and UV/chlorine), it should be recognized that TOCl is an intermediate.…”

“…73 The formation mechanisms include the direct chlorine addition to DOM and the sequential formation from the nucleophilic reactions between the DOM intermediates (DOM •+ or DOM(-H) • ) and Cl • , Cl 2 •− , or Cl − . Considering the numerous sources of DOM intermediates in the presence of AOPs and the ubiquitous Cl − in environmental-relevant waters (e.g., ∼10 −4 M in natural waters), 74,75 •− exposure in typical AOPs, evolution profile of DOC and SUVA variations, formation of TCM, and time-resolved spectra and kinetic traces for the investigation of TOCl formation mechanism (PDF).…”

Prioritizing Direct Photolysis Products Predicted by the Chemical Transformation Simulator: Relative Reasoning and Absolute Ranking

“…Rate information in databases, metabolizer algorithm, rank levels, calculation methods for the standardization factor and the formation ratio, additional library evaluation results and other supplementary data (PDF) Whole documentation of the direct photolysis reaction library v1. 3…”

“…1,2 The structures of formed photoproducts and their formation rates are crucial for a comprehensive understanding of the human/ecosystem risks posed by contaminants. 3 However, standardized experiments conducted to determine the identity and formation rates of photoproducts lag far behind the ever-growing number of contaminants released into natural water bodies. To narrow this knowledge gap, we developed the first freely available reaction library to predict direct photolysis products in silico.…”

“…Direct photolysis occurs when a compound absorbs light and, as a result, undergoes transformation. It is an important natural attenuation process for environmental organic contaminants that absorb sunlight in aquatic systems. , The structures of formed photoproducts and their formation rates are crucial for a comprehensive understanding of the human/ecosystem risks posed by contaminants . However, standardized experiments conducted to determine the identity and formation rates of photoproducts lag far behind the ever-growing number of contaminants released into natural water bodies.…”