CHANGES IN THE HEAVY-METAL CONTENTS OF SOIL FROM THE PARK GRASS EXPERIMENT AT ROTHAMSTED EXPERIMENTAL STATION

The classical Rothamsted Experiments allow to contribute to current re search. The heavy metal content of soil and hay samples have been meas ured with ICP-AES from a control and a fertilized plot of the Park Gra ss Experiment. Today a difference of 1.2 can be observed in the pH lev els of the control and fertilized plots; the pH level of the control p lot has decreased about 1.0, that of the fertilized plot about 2.2 as a result of 150 years of acid deposition and fertilization. The change s in the pH levels has caused many changes in the heavy metal content of the top layer of the soil. Using different extraction methods (e.g. , ammonium acetate, EDTA, and sequential analysis), the heavy metal co ntent of different fractions have been estimated. In the control plot, the Zn, Cd and Pb content increased. In the fertilized plot, the Pb a nd Cd contents have also increased because of atmospheric deposition a nd small amounts of lead in the fertilizer. The available form of Cd a nd Pb increased in both the control and the fertilized plots.