This study proposed deethylatrazine (DEA) as the (OH)-O-center dot probe compound during ozonation and compared with the widely used p-chlorobenzoic acid (pCBA) for the first time. Results showed the ozone decay was not affected by DEA, but largely accelerated by pCBA as compared to the control. The DEA degradation was exclusively attributed to (OH)-O-center dot formation from ozonation of the tested waters, while pCBA was partially degraded by (OH)-O-center dot formation from the pCBA-derived propagation reactions. In synthetic waters with different (OH)-O-center dot scavenging capacities, the ozone decay rates with DEA were almost consistent with the control. The ozone decay rates with pCBA remained consistent with the control only in the synthetic waters with high (OH)-O-center dot scavenging capacities. For the synthetic waters with low (OH)-O-center dot scavenging capacities, pCBA led to higher ozone decay rates and (OH)-O-center dot exposures, and thus gave overestimated R-ct values. The two (OH)-O-center dot probe compounds were also investigated in four authentic waters with different (OH)-O-center dot scavenging capacities. DEA exhibited no detectable effect on the ozone decay in all four authentic waters as compared to the control. The enhancing effects of pCBA on the ozone decay and (OH)-O-center dot formation were observed in the tap and reservoir water, which led to an overestimation of R-ct as compared to the presence of DEA. In the ground water and wastewater, similar values were observed in ozone decay rates and R-ct for the presence of pCBA and DEA. Thus, the use of pCBA as the (OH)-O-center dot probe compound should be carefully examined or avoided to prevent its interrupts in determining the R-ct during ozonation of waters with different (OH)-O-center dot scavenging capacities. DEA is a more appropriate (OH)-O-center dot probe compound during ozonation. (C) 2016 Elsevier B.V. All rights reserved.