What is the advantage of time-integrative versus instantaneous sampling?
Time-integrative sampling is, per se, better – and more expensive – than instantaneous sampling. The question is, whether the additional expense fully translates into better data. In most cases instantaneous sampling is sufficient as the deep soil has long gas retention / gas residence times: Seep gases from seep pulses do not disappear over night but remain in the soil for weeks. CTI’s Brassey oil field stationary field experiment data demonstrate this fact (Education). The advantage of time-integrative data collection is mostly exaggerated. Seep gases accumulating in the deep soil form a dynamic equilibrium: the snap shot sampling is representative for this sample site. Furthermore, most common time-integrative methods sample from very shallow depth – because of access problems at typical free gas sampling depth. Any sampling at very shallow depth just a few inches in the soil is problematic. There is an exponential increase of noise and erratic nature of data with decreasing sample
