EFFECT OF LEAD ON SOIL RESPIRATION AND DEHYDROGENASE-ACTIVITY

The effect of added Pb on the respiration and dehydrogenase activity of two sandy soils, a clay soil and a peat soil, (all with different physico-chemical properties), was studied. A concentration of 375 μg Pb· g- inhibited the respiration of the sandy soil by ca. 15%, 1500 μg Pb· g- ca. 50%. In the clay soil 1500 μg Pb· g- caused a 15% reduction in respiration. The inhibition of respiration in the sandy soil was still ca. 30% 40 months after the addition of Pb. Respiration of the peat soil was not affected by even 7500 μg Pb· g-. Dehydrogenase activity was affected by Pb in a similar way to soil respiration. In the sandy soil a considerable reduction occurred, while in the clay and peat soils dehydrogenase activity was not reduced. It was concluded, that a relationship exists between the inhibitory effects of Pb and the buffering capacity of the soil as expressed by its cation-exchange capacity. Because of these different effects of the same Pb concentration on the various soil types, no single value for the permitted concentration of lead pollution in soil could be established. © 1979.