Temporal pools of individual organic substances in soil

Two pools of plant-derived C³¹ n-alkane occurring respectively as free and humin-bound forms in the same soil have been distinguished by ¹³C/¹²C analyses. The results show that the humin-bound molecule is on the average 7 years older than the free molecule. These findings indicate that apolar organic substances can be trapped temporarily into the soil matrix by weak forces.