Abstract: The study with high-pressure mercury lamp illuminating showed that after illuminated for 15 min,NO₂^- and NO₃^- quenched the photolysis of mefenacet,and NO₃^- with a concentration ratio 10∶1 (mass) had the most obvious effect,its quenching rate being up to 53.3%.Halogen ions inhibited the photolysis of mefenacet by “weight atom effect”.When the concentration ratio of I^- was 10∶1,the quenching rate was 76.9% after illuminated for 15 min.Surfactants Nongru 500,Nongru 404,Nongru 601 and Nongru 603 had different effects on the photodegradation of mefenacet.At concentration ratios 1∶5 and 1∶1,only Nongru 404 showed a weak photosensitive effect,while in the other cases,all the four surfactants had photoquenching effects.Among the four herbicides benthiocarb,bensulfuron,alachlor and chlorsulfuron,only bensulfuron at low concentration ratio (1∶10) accelerated the photolysis of mefenacet,with a photosensitive proportion of 18.2% after illuminated for 25 min.Aerified N₂ could accelerate the photolysis of mefenacet,and the half-life was shortened from 7.14 min to 6.70 min without aerifying N₂.

Key words: Arthropod community, Functional group, Population dynamics, Vertical distribution