In this work, the strong enhancements of three alpha hydroxy acid (AHA = citric, tartaric and malic acids, respectively) in benzoic acid (BA) degradation process by UV-A/Fe(II)/peroxymonosulfate (PMS) have been investigated under near-neutral pH, 10 mu M Fe(II), and UV-A irradiation (photon flux of 0.709 mu E s(-1)). The BA removal ratios reached to 81.7%, 70.1%, and 55.2% in the three UV-A/AHA/Fe(II)/PMS processes within 600 s. The removal ratios were higher than those in UV-A/EDTA/Fe(ID/PMS and UV-A/oxalic/Fe(II)/PMS (16.2% and 14.4%, respectively). The enhancement effect of oxidation was attributed to the continuous activation of PMS by the regeneration of Fe(II) from the photolysis of Fe(III)-AHA complexes. The degradation of BA was classified into two stages based on the degradation kinetics. In the first stage, 15.2%, 18.4% and 11.0% of BA was removed by HO center dot and SO4 center dot- generated from the reaction of PMS with the addition of Fe(II) in UV-A/citric/Fe(II)/PMS, UV-A/tartaric/Fe(II)/PMS, and UV-A/malic/Fe(II)/PMS, respectively. In the second stage, most of BA (44.2%66.5%) was oxidized by HO center dot and SO4 center dot- produced from the reaction between PMS and the regeneration of Fe(II) from the photolysis of Fe(III)-AHA complexes. Both steady-state concentrations and oxidation contributions of HO center dot and SO4 center dot- in the second stage were determined according to the degradation dynamics of BA and nitrobenzene. The degradation of BA in the three UV-A/AHA/Fe(II)/PMS processes was pH dependent at near neutral pH (pH(int) = 5.0-7.0). In the presence of anions, the BA removal ratios decreased with the order of bicarbonate > chloride > sulfate. In the presence of humic acid (HA), the oxidation capabilities of UV-A/AHA/Fe(II)/PMS decreased due to the inner filter effect on the photolysis of Fe(III)-AHA complexes. The acute toxicity assay indicated that the UV-A/AHA/Fe(II)/PMS processes efficiently eliminated the toxicity of BA degradation products. With the fast radicals generation at near-neutral pH and high oxidation capabilities at different environmental factors, the three UV-A/AHA/Fe(ID/PMS processes exhibit potential to be a strong peroxymonosulfate activation method.