The increase in pH for the first few storms is likely due to leaching of
base cations (Ca, Mg, Na) from the compost mix. Fig. 2B shows the decreasing
trend of DOC within each individual storm for all storms.
Each new storm caused a new peak of DOC in the outflow. This renewed
release of DOC at the onset of each new storm was also observed by
Mullane et al. (2015). Maximum DOC concentrations at each new
storm gradually decreased, but DOC concentrations remained high.
The seventh storm still released about 230 mg/L DOC in the first outflow
sample. The concentrations of DOC in the leachates were one to three
orders of magnitude higher than the DOC concentration of the influent
stormwater (0.4 mg/L).