Assay of soil respiration also help to quantify the
effects of metals on the total biological activity of soils.
Addition of heavy metal salts to soils usually cause an
immediate decrease in respiration rates, but responses
are determined by the properties of both the metal and
the soil. According to Brookes (1995), high levels of
artificially added Pb may have no effect in clay soil but
may decrease respiration rates in a sandy soil. In this
work (Table 7) the respiration rates in the Cu and Cu:Zn
treated soils decreased significantly. This could be due
to the very high level of pollution as well as other
interactions involving metals in combined ionic states.
It can be seen,(Table 7) that the rate of inhibition of
soil respiration was highest in the Cu:Zn (0. 98