2.2 Soil enzyme activities and soil microorganisms
Soil dehydrogenase activities (DH) ranged between 0.41 and 1.83 μg TPF/(g dry soil·hr) in all the treatments (Fig. 1). In the case of CK3, a higher value was observed due to the inoculation of PAHs-degrading bacteria. At the same time, DH activities were significantly stimulated by organic waste addition in the plant-microbe system. How- ever, with increasing amounts of amendments, changing patterns were observed between SS and CM treatments; DH activities were relative stable in treatments with SS, while a decline of DH activity was observed in treatments with CM.
As shown in Fig. 2, the number of PAHs-degrading microorganisms in soil ranged from 1.14×106 to 16.6×106 MPN/g dry soil, respectively. As we can see, the gen- eral trends of changes in the number of microbes were similar to that of DH activity. When inoculated with PAH- degrading microorganisms in the present of alfalfa, the number of PAHs degrading microorganisms in CK3 was about 1.28 times higher than that in CK1. Application of SS and CM significantly increased the number of PAH-degrading microorganisms by about one order of magnitude higher than that of CK3.