D. Nie et al., THE DESIGN ARID TESTING OF A RELAXED EDDY ACCUMULATION SYSTEM, JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 100(D6), 1995, pp. 11415-11423
A flux measuring system has been developed based on relaxed eddy accum
ulation (REA, or conditional sampling) methodology. The system uses sa
mpling tubes packed with solid substrates to collect air samples for d
etermining the average concentration of compounds of interest. It has
been designed for measuring fluxes of various trace gas species by usi
ng appropriate. solid substrates in the tubes. The chief advantages to
this design are the following: (1) the placement of pump and flow con
trol apparatus are located downstream of the sampling tubes to elimina
te Sample heating and reduce contamination of the sample stream; (2) t
he addition of a zero gas channel available to the sampling tubes impr
oves the flow stability without diluting the sample; (3) the design pe
rmits the use of multiple sample tube magazines to allow sequential ru
ns without interruption; and (4) the; use of compact, easily transport
able sampling tubes permits analyses to be conducted gt an off-site la
boratory where analytical conditions a;re better controlled. The REA s
ystem was tested by measuring water vapor flux under held conditions;a
nd the resulting measurements are compared with those ma;de using a Bo
wen ratio system. The two methods gave similar results with fluxes val
ues that agreed within 12%, although the measurements from the REA sys
tem were generally higher than those from the Bowen ratio method.