15:45 〜 16:00
[ACG37-08] 砂質土壌における生分解性プラスチックの分解
キーワード：生分解性プラスチック、砂質土壌、二酸化炭素、重量減少
Plastics have highly improved the living level of human, but a lot of use of plastics causes environmental problems as marine microplastics at the same time. Biodegradable plastics (BP) are under development as a solution to this problem and began to be used as agricultural mulch sheets and plastic bags. There have been several studies on the decomposition of BP in soil, but most of them are conducted in temperate agricultural lands. The rate of BP decomposition in the natural environment is an important parameter, as BP becomes more widespread outside of agricultural lands in the future. However, to the best of our knowledge, there are no reports on the decomposition rate of BP in places where BP decomposition is expected to be slow, for example, as in cold region and sandy soils. The aim of this study was therefore to determine the potential rate of BP decomposition in the sandy soils.
We chose two study sites, bare ground soil and pine forest soil, in the coastal dunes, Tottori Prefecture (35°32' 26" N, 134°12'31"E). We carried out two kinds of experiments to investigate BP decomposition: a field experiment using the mesh back method and an incubation experiment using CO2 as a tracer (in a laboratory). In the field experiment, biodegradable agricultural mulch sheet K (BPK) was cut into 5 cm squares, placed in mesh bags, and installed at a depth of 30 cm (n=3). We collected samples after 162 days to assess weight loss. In the incubation experiment in a laboratory, BPK 0.5g was added to 10 g of dry soil (n=3), and the CO2 concentration in the vials was measured with a LI-6262 or LI-7200 (LI-COR Co.) at intervals of approximately two weeks. The water condition was adjusted 30% and 60% to maximum water holding capacity (WHC).
BPK decomposition during 162 days in sandy soils was detected. Weight loss in the field experiment was 1.4% in bare ground soil and 1.0% in pine forest soil. In the incubation experiments, the difference in CO2 emission between soil without BPK and soil with BPK was attributable to the decomposition of added BPK (Fig.1). These results indicate that even sandy soils has the potential to decompose BP.
We chose two study sites, bare ground soil and pine forest soil, in the coastal dunes, Tottori Prefecture (35°32' 26" N, 134°12'31"E). We carried out two kinds of experiments to investigate BP decomposition: a field experiment using the mesh back method and an incubation experiment using CO2 as a tracer (in a laboratory). In the field experiment, biodegradable agricultural mulch sheet K (BPK) was cut into 5 cm squares, placed in mesh bags, and installed at a depth of 30 cm (n=3). We collected samples after 162 days to assess weight loss. In the incubation experiment in a laboratory, BPK 0.5g was added to 10 g of dry soil (n=3), and the CO2 concentration in the vials was measured with a LI-6262 or LI-7200 (LI-COR Co.) at intervals of approximately two weeks. The water condition was adjusted 30% and 60% to maximum water holding capacity (WHC).
BPK decomposition during 162 days in sandy soils was detected. Weight loss in the field experiment was 1.4% in bare ground soil and 1.0% in pine forest soil. In the incubation experiments, the difference in CO2 emission between soil without BPK and soil with BPK was attributable to the decomposition of added BPK (Fig.1). These results indicate that even sandy soils has the potential to decompose BP.