Meteorological Variables Associated with Population Density of Culturable Atmospheric Bacteria at a Summer Site in the Mid-Willamette River Valley, Oregon

Abstract : Six of 20 environmental parameters were statistically selected as significant conservative, dependent parameters in statistical tests that would determine the parameter's ability to account for the variability of the dependant variable, culturable atmospheric bacteria (CAB), in 1st, 2nd, or 3rd degree linear models. The six parameters were (1) wind direction 10 m above ground level (AGL), (2) air temperature difference between 2.3 and 6.3 mm AGL, (3) wind speed 1.7 m AGL, (4) air temperature, (5) relative humidity 2.3 m AGL, and (6) time of day. Using the foregoing parameters, the models went from relatively poor (i.e., Adj. R(exp 2)=0.37) to moderately good (i.e., Adj. R(sub 2)=0.59). With these parameters, high CAB values were associated with morning convective air due to solar heating of the earth. This resulted in high air temperatures and consequent low relative humidity air masses that traversed the agriculturally, very active, Willamette River Valley, OR, with winds from the ENE. Thus, the atmospheric bacterial sources in these winds were probably from plant/soil surfaces and farming operations.