Formula for the resuspension factor and estimation of the date of surface contamination

We propose a theoretical formula of the time dependence of the resuspension factor, a quantity which indicates the degree of ground-surface contamination. The formula, K(t) t−4/3, agrees well with the empirical law of the resuspension factor, and conforms to the data of short periods such as 0.1 s in wind-tunnel experiments, as well as very long period, such as field observations in Chernobyl over years. We use the formula to estimate the date when pollutants were deposited on the ground. The estimated date is close to the date when the site was actually contaminated. Using this formula, the date when a pollution occurred can be estimated even if the actual date is unknown.