Surface lead pollution of roadside crops in relation to the distance from an emitting line source

The asymptotic decrease in lead concentration c in roadside crops according to the distance d from the edge of an isolated straight road can be described empirically by means of the three‐parameter exponential function c=A+B exp (‐Cd). Least‐squares non‐linear regression allows the estimation of the parameters A, B and C. The validity of the function was tested by fitting it to a few sets of observations on unwashed wine grape and leaf samples. An analysis of residuals was performed, considering in particular the extent of the normality of their distribution. The function was also applied to a few sets of data of low sample size to examine the effect of washing on the parameters of the function.