Journal of Environmental Conservation Engineering

This study examines countermeasures against asbestos by predicting air concentrations of asbestos in order to reduce health risk of asbestos from demolishing buildings and other processes. A comparative study was conducted on three cases as follows; Case 1 was "No action", Case 2 was "Demolishing by hand", and Case 3 was "Vitrification treatment". The result showed that the health risk from Case 2 is 20% less risky than Case 1, if Case 2 is accomplished perfectly. More desirably, the health risk from Case 3 is 30% less risky than Case 1. In addition, " No action " takes the longest time to achieve risk reduction. However, Case 2 and Case 3 can greatly reduce the time needed. Therefore, this study indicates that "Demolishing by hand" should be conducted first. If it is not possible to conduct perfectly, "Vitrification" can be applied even though the cost is high.

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Largemouth bass and Bluegill, major invasive alien fish species in Japan, have been extending their habitat ranges over not only Lake Biwa and the lagoons but also surrounding waters connected to them through small rivers and canals. Their increasing number is bringing about the reduction in the number of native fish species. To prevent the spread of these alien species through small rivers and canals during breeding season of the native fish (crucian carp), this study experimentally examined the effect of a submerged weir on controlling upstream migration of the alien species and the native fish. As a result of the experiment, the ratio of the alien species migrating upstream decreased as the weir height rose, whereas the ratio did not show the same trend in the case of the native fish. The ratio of the alien species also decreased as the overflow velocity over the weir rose. On the other hand, the ratio of the native fish increased as the overflow velocity rose up to 1.0m/s and decreased thereafter. These results suggest that the submerged weir may control upstream migration of the alien species to surrounding waters through small rivers and canals without interfering with the reproductive migration of the native fish.

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