2007 Volume 61 Issue 1 Pages 54-65
To avoid a food crisis caused by the population explosion, preservation of resources and the environment aswell as an increase in biological production in shallow seas are essential in Japan, which is surrounded by water.
However, since resources and the environment have been harmed by the ocean dumping of fly ash (FA) and clinker ash (CL), gravel extraction for aggregate and industrial by-product, we developed waste use-concrete-blocks containing these wastes for seaweedbeds. Then we investigated the preservation of resources and the environment and the increase of biological production in shallow seas using these beds to solve these problems.
In the first experiment, the durability and the strength of five mortar test pieces were measured to form a seaweedbed. The five test pieces were Plain (normal mortar), FA&CL, FA&CL+zeolite, FA&CL+molding sand and FA&CL+zeolite+molding sand. In the second experiment, harmful materials, extracted from FA&CLmortar test pieces by elution test were investigated to examine their influence on the marine environment and marine life.
Furthermore, to investigate how well aquatic life can growon the mortar test pieces, the mortar test pieces wereimmersed in seawater, and then biomass of biofilm was measured the quantityof ATP, chlorophyll a, and FDA decomposition activity.
The results of the first experiment showed that recycled waste-use-concrete containing FA, CL, molding sand and zeolite had sufficient strength for seaweed beds. The results of the second experiment showed that the test pieces were also safe forseaweed beds since there was hardly any trace of heavy metals or organic phosphorus detected. The results of last experiment were: (1) The quantity of ATP of three types of zeolite-molding sand system pieces (FA&CL+zeolite, FA&CL+molding sand and FA&CL+zeolite+molding sand) was almost equal to the Plain or larger than the Plain.(2) The quantity of chlorophyll a was FA&CL+molding sand>FA&CL+zeolite>FA&CL+zeolite+molding sand=FA&CL>Plain.(3) FAD decomposition activity was roughly the same as that of the Plain.
Based on the above fundamental results, three types of large tes tconcrete-blocks were prepared: plain (normal concrete), FA&CL (concrete containing FA and CL as aggregate) and FA&CL+Zeolite+Fe including molding sand (concrete contained FA, CL, Zeolite and Fe including molding sand). Five blocks of each type formed each unit, and then, they were sunk in the test sea area at a depth of 5min two layers.After that, four diving surveys were conducted over a period of one year and nine months. In this investigation, the Quadrate Method was employed to measure the amount of seaweed and the Line Transect Method was used toobserve the swarm characteristics.
In the results, the amount of seaweed on FA&CL+Zeolite+Fe including molding sand was equality or greater than that on the other two types of blocks. This means that aquatic life was able to suitably adhere and grow on the blocks containing FA&CL+Zeolite+Fe including molding sand. Furthermore, the amount of seaweed on the seaweed-bed was greater than thaton the adjacent seaweed-beds made of natural stones. As a result, the blocks made of FA&CL+Zeolite+Fe including molding sandaccelerate the formation of seaweed-beds, and therefore provide a good substrate for seaweed-beds.
