Factors affecting formation of deethyl and deisopropyl products from atrazine degradation in UV/H2O2 and UV/PDS

In this study, the formation of deethyl products (DEPs) ( i.e. , atrazine amide (Atra-imine) and deethylatrazine (DEA)) and deisopropyl product ( i.e. , deisopropylatrazine (DIA)) from parent atrazine (ATZ) degraded in UV/H 2 O 2 and UV/PDS processes under various conditions was monitored. It was found that SO 4 &z.rad; − displayed a more distinctive preference to the ethyl function group of ATZ than HO&z.rad;, leading to the higher ratio of DEPs/DIA in UV/PDS system than that in UV/H 2 O 2 system in pure water. The effects of water matrices ( i.e. , natural organic matter (NOM), carbonate/bicarbonate (HCO 3 − /CO 3 2− ), and chloride ions (Cl − )) on ATZ degradation as well as formation of DEPs and DIA were evaluated in detail. The degradation of ATZ by UV/PDS was significantly inhibited in the presence of NOM, HCO 3 − /CO 3 2− or Cl − , because these components could competitively react with SO 4 &z.rad; − and/or HO&z.rad; to generate lower reactive secondary radicals ( i.e. , organic radicals, carbonate radicals (CO 3 &z.rad; − ) or reactive chlorine radicals (RCs)). The yields of these DEPs and DIA products from ATZ degradation were not impacted by NOM or HCO 3 − /CO 3 2− , possibly due to the low reactivity of organic radicals and CO 3 &z.rad; − toward the side groups of ATZ. Howbeit, the increase of DIA yield companied with the decrease of DEPs yield was interestingly observed in the presence of Cl − , which was attributed to the promotion of Cl − at moderate concentration (mM range) for the conversion of SO 4 &z.rad; − into HO&z.rad;. Comparatively, in the UV/H 2 O 2 process, NOM and HCO 3 − /CO 3 2− exhibited a similar inhibitory effect on ATZ degradation, while the influence of Cl − was negligible. Differing from UV/PDS system, all these factors did not change DEPs and DIA yields in UV/H 2 O 2 process. Moreover, it was confirmed that RCs had a greater selectivity but a lower reactivity on attacking the ethyl function group than that of SO 4 &z.rad; − . These findings were also confirmed by monitoring the degradation of ATZ as well as the formation of DEPs and DIA in three natural waters. Formation of deethyl products (DEPs) ( i.e. , atrazine amide and deethylatrazine) and deisopropyl product ( i.e. , deisopropylatrazine (DIA)) from parent atrazine (ATZ) degraded in UV/H 2 O 2 and UV/PDS processes under various conditions was monitored.