A two-exponential model to describe the vanishing trend of 2,3,7,8-tetrachlorodibenzodioxin (TCDD) in the soil at Seveso, northern Italy

A linear combination of two exponentials associated with fast- and slow-vanishing dynamics is used to describe TCDD persistence pattern in the soil at Seveso. Slow dynamics (long-term coordinates; t ⪢ 1.50 y) were considered in an earlier investigation. This paper considers the pre-requisites for fitting the fast exponential term. In the absence of enough direct experimental data, a four-data set (short-term coordinates; t ≤ 1.50 y) was made up from mathematical calculations. The amount of TCDD in Seveso's most contaminated area (Zone A) is tentatively estimated to be ≥ 34 kg (from regression equation lower edge); TCDD fast dynamics half-life is shown to be 23 days (mean value).