It is very important to reduce phosphorus flux from sediment as well as cutting down terrigenous loads in order to control eutrophication in semi-enclosed coastal seas. Hydrogen sulfide is also a noxious substance which is highly toxic and fatal to benthic organisms. The purpose of this study is to evaluate remediation efficiency of organically enriched sediments using granulated coal ash (GCA) in terms of reducing benthic phosphorus flux and hydrogen sulfide. A flow-through experimental system was used to simulate the semi-enclosed water bodies. The application of GCA decreased the concentration of PO4(3-) in the pore water effectively, and reduced phosphate releasing flux from the sediment into overlying water by 37-44% compared to the control. The hydrogen sulfide in the pore water was also decreased by 77-100%, due to adsorption onto the GCA and deactivation of sulfate-reducing bacteria due to increasing pH. Thus, GCA is a promising recycled material for reducing phosphate releasing flux from organically enriched sediment to alleviate eutrophication as well as reduce the concentration of hydrogen sulfide in pore water.

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Particle crushing tests were performed on single particles from six types of clinker ash, as well as a series of monotonic shear tests using effective confining pressures [Formula: see text] of 50, 100 and 200 kPa at an intended degree of compaction Dc  =  100%, in order to investigate the relationship between particle strength and monotonic shear strength. Samples with intended degrees of compaction Dc  =  85% and 90% were also tested at [Formula: see text]  =  50 and 100 kPa in order to investigate the effect of degree of compaction on the shear strength of clinker ash. It was found that clinker ash is a crushable material with weak particle strength when compared with natural sands, although it has higher shear strength especially at Dc ≥ 95%, where the shear resistance angle exceeds 45°. The average crushing stress σf of the particles shows a strong correlation with the residual secant friction angle φres, with φres increasing along with the average crushing stress σf. It was also found that σf can be used to calculate φres and, in turn, the peak secant friction angle φpeak of clinker ash.