Abstract
The microbial activities in samples of water and sediment of the Nagara River were discussed on the basis of the first-order rate constant (K) estimated through biodegradation tests, for which glucose and 17β-estradiol (E2) were used as the substrates. For the water samples, a correlation was observed between K and bacterial concentration. However, for the sediment samples, no correlation was observed. The K values of both substrates in the water samples from the downstream of the Nagara River were higher than those in the water samples from the upper and middle reaches. In the case of the K values of both substrates in the sediment samples, a different trend was observed. As for the range of the K values per unit bacterial concentration, for the water samples, glucose was 4.5×10-7- 1.8×10-3 h-1·cell·L and E2 was 2.7×10-7- 7.0×10-4 h-1·cell-1·L; for the sediment samples, glucose was 6.0×10-8- 1.7×10-5 h-1·cell-1·L and E2 was 1.3×10-7- 1.9×10-5 h-1·cell-1·L. From the comparison of the K values of both substrates, it was shown that glucose is more easily biodegraded by microorganisms suspended in water than E2.
