146
We also performed biodegradation tests for 350 days under aerobic conditions to
check the degree of SOC decomposition (Fig. 5.11). SOC was 2.1 mg C g-dry
−1
at
the start of the test and decreased to 1.2 mg C g-dry
−1
after 100 days, but it remained
unchanged at 350  days. These results confirmed that it is valid to estimate the
R-SOC based on 100-day biodegradation tests.
0
1
2
3
0
1 00
350
SOC
(mg C g-dry -1
)
Time (day)
Fig. 5.11 Changes in SOC
biodegradation over time.
(Modified from Nishio
et al. 2016)
0.0
1.0
2.0
3.0
4.0
5.0
Jun. Jul. Aug. Sep. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May. Jun. Jul. Aug.
Decomposed organic carbon
Residual orbanic carbon
0.0
1.0
2.0
3.0
4.0
5.0
Jun. Jul. Aug. Sep. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May. Jun. Jul. Aug.
Decomposed organic carbon
Residual orbanic carbon
N.D.
N.D.
N.D.
N.D.
(a)
SOC
(mg C g-dry -1
)
(b)
SOC
(mg C g-dry -1
)
Fig. 5.10 Concentration of decomposed organic carbon and residual organic carbon of the sediment in (a) the intertidal flat and (b) the subtidal flat. (Modified from Nishio et al. 2016)
T. Endo and S. Otani