The respiration rate of each sample was measured by
trapping CO2 in 5 mL 0.2 M NaOH in airtight glass jars.
After 6 h incubation of the soil samples in the tightly
closed jars, 2 mL BaCl2 was added to the NaOH solution,
and the excess of sodium hydroxide was titrated with
0.1 M HCl in the presence of phenolphthalein as coloured
indicator. The blanks were empty jars randomly distributed
among the others. The respiration rate for each sample is
expressed as mM CO2 per kg organic matter per 24 h.
Multifactor ANOVA was applied to test the significance
of the effects of soil type (P, UP), copper contamination