Abstract
The biodegradability of certain biofuels was studied in the case of forest soils using the manometric respirometric technique, which was proved to be very suitable for untreated, fertilized as well as pH adjusted soils. Experiments carried out in infertile sandy forest soil gave a BOD/ThOD value of 45.1% for a typical model substance, that is, sodium benzoate after a period of 30 days and mineral addition improved the BOD/ThOD value to a value of 76.2%. Rapeseed oil-based chain oil almost did not biodegrade at all in 30 days in nonprocessed soil, and when pH was adjusted to 8.0, the BOD/ThOD value increased slightly to a value of 7.4%. Mineral addition improved the BOD/ThOD value on average to 43.2% after 30 days. The combined mineral addition and pH adjustment together increased the BOD/ThOD value to 75.8% in 30 days. The observations were similar with a rapeseed oil-based lubricating oil: after 30 days, the BOD/ThOD value increased from 5.9% to an average value of 51.9%, when the pH and mineral concentrations of the soil were optimized. The mineral addition and pH adjustment also improved the precision of the measurements significantly.
Highlights
In 2004, (Finland’s environmental administration, Helsinki, Finland) was aware of more than 20,000 sites, in which the soil could be contaminated
When mineral solution was added after the pH adjustment, a soil sample with high amounts of basic nutrients was obtained
The degree of biodegradation was 35.6% in the Lubricating oil Chain oil Lubricating oil + mineral solution Chain oil + mineral solution precision test, whereas the corresponding value in Figure 2 was 50.8%. It seems that soil 1 is not as homogeneous as soil 3s, in which replication tests of both this chain oil and tall oil fatty acid (TOFA) produced significantly more precise results in a 14-day measurement period [8] than observed in this case
Summary
In 2004, (Finland’s environmental administration, Helsinki, Finland) was aware of more than 20,000 sites, in which the soil could be contaminated. Around 10,000 sites were located at less than 100 metres away from residential, groundwater, or surface water areas; or less than 200 metres away from a source of water supply, and were potentially contaminated. The suitability of this method in terms of biodegradation measurements of oils in water was evaluated using forestry hydraulic oils as model oils [5] This method seems to be accurate and precise for determining biodegradation abilities of oil products. The study presented in [8] still raises questions: “How could the soils used be modified to make the effective biodegradation of oil products possible, and could this be done accurately and precisely?”; “Is an automatic respirometric method such as the BOD OxiTop method suitable for such studies?” The present article is a direct continuation for our previous studies and sets out to find out answers for the posed questions. The effect of the soil type and other environmental parameters on the biodegradation of chemicals in soils has been studied intensively by other researchers during recent years [9,10,11,12]
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