- Email: [email protected]
Revegetation of Landfill Soils
281
Chapter 26. REVEGETATION OF LANDFILL SOILS Enzymological research in the United Kingdom Wigfull et al (1987a, b) and Wigfull and Birch (1987) have studied the soils used as covers in the restoration of completed domestic refuse landfill areas at St. Osyth (Colchester,
160 h ^ UO JO.
> c5 120 > 5 G T 100 <
if)
<
z
LU O
aQ > X
o
o> c o
N 80 o £ 60
I ^0 Q.
C7»
20
1
5
6
9
TIME AFTER RESTORATION (YEARS)
Figure 18. Soil dehydrogenase activity against time after restoration of four completed landfill areas. Redrawn from: S.D. WigfiiU, J.A. Harris and P. Birch, Conference on "Reclamation and Restoration of Soils" (London, 1987), Graph 1. The bars indicate standard deviations.
282 Essex, England). For enzymological, microbiological, and chemical analyses, samples were taken, in April 1986, from the 0-30-cm layer of soils that had been placed on the completed landfill areas 1-9 years previously. After being used for covering the landfills, these soils were not fertilised and sown, but were sparsely or abundantly revegetated with grasses from their seed-bank. Figure 18 shows the results obtained in the determination of dehydrogenase activity in soils of four landfill areas under spontaneous revegetation for 1, 5, 6, and 9 years. The 1-yearold area was restored with poor-quality topsoil, whereas for the restoration of the older areas subsoils of different qualities were used. The vegetation cover was sparse on the 1- and 6year-old areas and well developed on the 5- and 9-year-old ones. One can deduce from Figure 18 that dehydrogenase activity increased with time after restoration, except for the sparsely vegetated 6-year-old area, the soil of which was less dehydrogenase-active than the soil of the 5-year-old area. It has also been established that, within the 0-30-cm soil layer, dehydrogenase activity decreased with increasing depth, except for the 9-year-old area, in which the activity was low in the 0-5-cm depth, and increased and became constant in the 5-30-cm depth. This particular behaviour of the 9-year-old area might be caused by the development of anaerobiosis within the higher zone of the soil profile due to surface pooling above compacted and drier lower zones. Dehydrogenase activity correlated significantly with total organic C and N contents (Table 36) as well as with microbial biomass (ATP content) in the soils of the four areas. Table 36 Correlation matrix concerning the age of restored landfill areas, soil physico-chemical properties and dehydrogenase activity (the figures denote correlation coefficients)
pH Total N content Total organic C content Moisture content Dehydrogenase activity C-to-N ratio
Age
pH
-0.357 0.596 0.657 -0.135 0.813 0.823
-0.440 -0.494 -0.474 -0.580 -0.621
Total N content
0.995* 0.682 0.957* 0.232
Total organic C content
0.640 0.966* 0.324
Moisture content
0.467 -0.282
Dehydrogenase activity
0.556
Reproduced from; S.D. Wigftill, J.A. Harris and P. Birch, Conference on "Reclamation and Restoration of Soils" (London, 1987), Table 3. * The asterisks indicate significance at >95%.
283 These soils, in comparison with native undisturbed soils, contained less ATP and their dehydrogenase activity was lower, although they contained similar numbers of viable microorganisms. Wigfull and co-workers drew the conclusion that the measurement of soil dehydrogenase activity could be useful in estimating the restoration potential of soils and as an index of the success of landfill and other restoration programmes.
Chapter 26. REVEGETATION OF LANDFILL SOILS Enzymological research in the United Kingdom Wigfull et al (1987a, b) and Wigfull and Birch (1987) have studied the soils used as covers in the restoration of completed domestic refuse landfill areas at St. Osyth (Colchester,
160 h ^ UO JO.
> c5 120 > 5 G T 100 <
if)
<
z
LU O
aQ > X
o
o> c o
N 80 o £ 60
I ^0 Q.
C7»
20
1
5
6
9
TIME AFTER RESTORATION (YEARS)
Figure 18. Soil dehydrogenase activity against time after restoration of four completed landfill areas. Redrawn from: S.D. WigfiiU, J.A. Harris and P. Birch, Conference on "Reclamation and Restoration of Soils" (London, 1987), Graph 1. The bars indicate standard deviations.
282 Essex, England). For enzymological, microbiological, and chemical analyses, samples were taken, in April 1986, from the 0-30-cm layer of soils that had been placed on the completed landfill areas 1-9 years previously. After being used for covering the landfills, these soils were not fertilised and sown, but were sparsely or abundantly revegetated with grasses from their seed-bank. Figure 18 shows the results obtained in the determination of dehydrogenase activity in soils of four landfill areas under spontaneous revegetation for 1, 5, 6, and 9 years. The 1-yearold area was restored with poor-quality topsoil, whereas for the restoration of the older areas subsoils of different qualities were used. The vegetation cover was sparse on the 1- and 6year-old areas and well developed on the 5- and 9-year-old ones. One can deduce from Figure 18 that dehydrogenase activity increased with time after restoration, except for the sparsely vegetated 6-year-old area, the soil of which was less dehydrogenase-active than the soil of the 5-year-old area. It has also been established that, within the 0-30-cm soil layer, dehydrogenase activity decreased with increasing depth, except for the 9-year-old area, in which the activity was low in the 0-5-cm depth, and increased and became constant in the 5-30-cm depth. This particular behaviour of the 9-year-old area might be caused by the development of anaerobiosis within the higher zone of the soil profile due to surface pooling above compacted and drier lower zones. Dehydrogenase activity correlated significantly with total organic C and N contents (Table 36) as well as with microbial biomass (ATP content) in the soils of the four areas. Table 36 Correlation matrix concerning the age of restored landfill areas, soil physico-chemical properties and dehydrogenase activity (the figures denote correlation coefficients)
pH Total N content Total organic C content Moisture content Dehydrogenase activity C-to-N ratio
Age
pH
-0.357 0.596 0.657 -0.135 0.813 0.823
-0.440 -0.494 -0.474 -0.580 -0.621
Total N content
0.995* 0.682 0.957* 0.232
Total organic C content
0.640 0.966* 0.324
Moisture content
0.467 -0.282
Dehydrogenase activity
0.556
Reproduced from; S.D. Wigftill, J.A. Harris and P. Birch, Conference on "Reclamation and Restoration of Soils" (London, 1987), Table 3. * The asterisks indicate significance at >95%.
283 These soils, in comparison with native undisturbed soils, contained less ATP and their dehydrogenase activity was lower, although they contained similar numbers of viable microorganisms. Wigfull and co-workers drew the conclusion that the measurement of soil dehydrogenase activity could be useful in estimating the restoration potential of soils and as an index of the success of landfill and other restoration programmes.