Dividing the six sampling points into three periods clarifies the
variation of odor concentrations during the course of a day in different
seasons (Table 4). Similar characterizations of odor pollution
on the working face could be found in spring and winter, in which
higher odor concentrations occurred at 2:00 am, 6:00 am, 2:00 pm
and 10:00 pm. Odor pollution tends to be more serious in daytime
during summer, while odor concentration increases steadily in a
day until it reaches the highest level at night in autumn.
According to Lu et al. (2009) who conducted similar experiments
in surrounding communities of the same landfill site in winter,
odor concentrations showed a day–night alternation at their monitoring
points. Low odor concentrations were generally found at
12:00 am, while peak odor concentrations were detected at
4:00 am. The results of their study were generally consistent with
the current study (in winter) despite the different peak times,
which could be attributed to the different sampling points with
the current study, more specifically caused by diffusion, dry/wet
subsidence, and chemical reactions of odorants that occur during
their migration from the working face to the surrounding
community.