Options
Effects of different artificial topsoils on some ornamental plants
Author
Tan, Lay Pheng
Supervisor
He, Jie
Lee, Sing Kong
Abstract
This project was designed to study the effects of different artificial topsoils produced from mixing incinerator flyash, sewage sludge, biochips and subsoil (from granite origin) on the physiology of some local popular ornamental plants. These artificial topsoils contained various levels of heavy metals such as Cd, Cr, Cu, Fe, Pb and Zn which affected the physiology of plants when they exceeded certain threshold levels. The plants used were Bougainvillea spectabilis, Ixora coccinea, Heliconia psithacorum x H. spathocircinata cv. Golden Torch, Heliconia rostrata and Heliconia psithacorum cv. Tay. They are hereby simply referred to as Bougainvillea, Ixora, Golden Torch, Rostrata and Tay respectively. The physiological responses of these plants were determined by chlorophyll fluorescence Fv / Fm ratios, photosynthetic light responses; and analyses of their chorophyll, nitrogen and soluble protein contents. Their morphology and toxicity symptoms were also recorded. After six weeks of growth in the artificial topsoils, the plants were analysesd for the heavy metal content in their tissue. Finally, one of the optimal artificial topsoil mixture with 2% flyash was used to conduct leachate test to study the feasibility of using such artificial topsoil in open areas subjected to rainfall.
The results of the physiological tests indicated that Bougainvillea was the most tolerant of the high heavy metal content in the artificial topsoils. It could tolerate up to 4% flyash in the artificial topsoil (P<0.05). On the other hand, Ixora was the least tolerant as it could only grow well in mixture with 1% and 2% flyash (P<0.05). Golden Torch, Rostrata and Tay had intermediate tolerance and they could tolerate up to 3% flyash in the artificial topsoil (P<0.05). It was found that all the ornamental plants grown in the four mixtures of artificial topsoil could accumulate more Cd, Cu, Pb and Zn than the control plants (P<0.05). The latter were plants of the same age grown in soil fertilised weekly using a chemical fertiliser with a NPK ratio of 15:15:15. Although all the test plants could grow well in artificial topsoil with up to 2% flyash, some of the heavy metals such as Cd, Pb and Zn in the leachate exceeded the Singapore Standard for Trade Effluent Discharge into controlled watercourse (STED) based on 1996 Pollution Control Report. This project also looked into how the heavy metals effect their toxicity; other possible applications of the formulated artificial topsoils; and future research areas.
The results of the physiological tests indicated that Bougainvillea was the most tolerant of the high heavy metal content in the artificial topsoils. It could tolerate up to 4% flyash in the artificial topsoil (P<0.05). On the other hand, Ixora was the least tolerant as it could only grow well in mixture with 1% and 2% flyash (P<0.05). Golden Torch, Rostrata and Tay had intermediate tolerance and they could tolerate up to 3% flyash in the artificial topsoil (P<0.05). It was found that all the ornamental plants grown in the four mixtures of artificial topsoil could accumulate more Cd, Cu, Pb and Zn than the control plants (P<0.05). The latter were plants of the same age grown in soil fertilised weekly using a chemical fertiliser with a NPK ratio of 15:15:15. Although all the test plants could grow well in artificial topsoil with up to 2% flyash, some of the heavy metals such as Cd, Pb and Zn in the leachate exceeded the Singapore Standard for Trade Effluent Discharge into controlled watercourse (STED) based on 1996 Pollution Control Report. This project also looked into how the heavy metals effect their toxicity; other possible applications of the formulated artificial topsoils; and future research areas.
Date Issued
1998
Call Number
S591 Tan
Date Submitted
1998