I know I should go back to university with this one, I must have slept during phys chem lessons...

For assessment of hydrolysis of a compound, we record kinetics of degradation of a compound at three pH values and three temperatures for each pH according to the OECD 111 guideline ( ... 4069701-en).
So far so good, we have nice kinetics and nice half lives (ranging from 30 h at pH 9 at 323 K to 50 h for pH 7 at 283 K). Plots of ln k against 1/T for each pH are linear.
Now comes the interesing part: In section 36 (page 6) of the abovementioned guideline the k_obs parameter is calculated from k_acid + k_neutral + k_alkaline. These k_acid, k_neutral and k_alkaline describe the temperature dependency at each pH value. So two questions come up to me now:
1.) What temperature goes into the exponent of the Arrhenius equation?
2.) What does the resulting k_obs tell me?

Any pointers to enlightenment very welcome :)