Ōsaka, Japan
Ōsaka, Japan

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Matsui N.,Kanso Technos Co. | Suekuni J.,Kanso Technos Co. | Nogami M.,Kansai Electric Power Co. | Havanond S.,Payatai | Salikul P.,Payatai
Wetlands Ecology and Management | Year: 2010

Hydraulic restoration by opening the shrimp pond banks facilitated the establishment of planted mangroves and colonisation by non-planted mangrove species and was shown to be an effective method of mangrove rehabilitation. Planted Rhizophora apiculata and Rhizophora mucronata had grown significantly in 6 years, to 300 and 350 cm, respectively. However, the growth rate of Bruguiera cylindrica was merely 150 cm in the same period despite vigorous growth in the initial stage. About 15 non-planted mangrove species had colonised within 6 years after reopening the banks, with the dominant species being Avicennia marina (46. 9%) followed by B. cylindrica (27. 0%) and Ceriops tagal (14. 9%). After the enhancement, soil organic carbon increased considerably from 110 to 160 tonC ha-1 in 2 years at the lower elevation, indicating that hydraulic restoration could stimulate carbon recovery through enhancement of mangrove growth. However, soil organic carbon decreased by almost half in the higher ground, suggesting that carbon decomposition was accelerated due to drying of soils. © 2010 Springer Science+Business Media B.V.


Naohiro M.,Kanso Technos Co. | Putth S.,Trang Coastal Aquaculture Station | Keiyo M.,Kansai Electric Power Co.
International Journal of Ecology | Year: 2012

The study site is currently retreating at a rate of 20my 1 due to severe coastal erosion and found to be highly polluted as revealed from the water, sediment and biological analysis. In an attempt to prevent coastal erosion, 14,000 Rhizophora mucronata (RM) trees were planted across a heavily eroded shoreline at Samut Sakhon, Thailand. The survival rate of RM was high at the landward area and decreased at the offshore area. The most landward plot showed the highest survival rate when measured 4 years after planting (63.5%), while only 26.7% of trees survived at the most offshore plot. NPK and coconut fiber were shown to be significantly effective to enhance initial tree growths in heavily eroded area. © 2012 Matsui Naohiro et al.


Hamasaki K.,Tokyo University of Marine Science and Technology | Matsui N.,Kanso Technos Co. | Nogami M.,Kansai Electric Power Co.
Fisheries Science | Year: 2011

Size at sexual maturity and body size composition of mud crabs Scylla spp. were examined as the basis for settling a minimum landing size as a fishing regulation in Don Sak, Bandon Bay, Gulf of Thailand, which has suffered serious mangrove habitat degradation. Mud crabs were caught using baited traps and gill nets. Hooked metal rods were also used to lever the crabs out of their burrows inside the mangroves. Two mud crab species, S. paramamosain and S. olivacea, occur in the bay; S. paramamosain is the dominant species, accounting for 87% of the samples. The size at which 50% of the S. paramamosain females reached maturity (SM 50) was estimated as an external carapace width (ECW) of 112.0 mm based on the morphology of the abdomen. Allometric changes in the crushing chelae height to ECW ratio suggested that the SM 50 of S. paramamosain males occurred at 106.4 mm ECW. The body size composition revealed that mainly immature mud crabs were exploited in Don Sak. To maintain a sustainable fishery for mud crabs, fishing regulations-including a minimum landing size based on the SM 50 estimates-are essential, as is habitat restoration. © 2010 The Japanese Society of Fisheries Science.


Matsui N.,Kanso Technos Co. | Morimune K.,Kansai Electric Power Co. | Meepol W.,Ranong Mangrove Forest Research Center | Chukwamdee J.,Wildlife and Plant Conservation
Forests | Year: 2012

Forest carbon stocks-both in terms of the standing biomass and the soil organic carbon (OC)-were monitored in the mangrove plantation reforested from an abandoned shrimp pond for the 10 years following land excavation. Excavation to a level of 25 cm below the existing ground level increased the inundation time of tidal water from 463 to 7,597 hours per year, resulting in a significant increase of survival/growth rates for planted mangrove species, Rhizophora mucronata (RM) and Bruguiera cylindrica (BC), and of carbon stocks as well. RM showed high rates of standing biomass accumulation with 98.7 ton/ha while 28.8 ton/ha for BC was measured over 10 years in the excavated area. In contrast, the unexcavated area showed low rates of biomass accumulation, 1.04 ton/ha for RM and 0.53 ton/ha for BC in the same period. The excavated area recorded a twofold increase of soil OC in the upper 5 cm of the surface soil from 71.8 to 154.8 ton/ha in 10 years, however it decreased to 68.3 ton/ha in the unexcavated area where soil OC is susceptible to decomposition. These results imply that the potential of carbon sinks in reforested land from abandoned areas cannot be developed unless hydraulic conditions are properly recovered. The fast growing species Avicennia marina (AM) grew quickly for the first two years after colonization but its growth slowed down afterwards, showing a limited ability of carbon capture. © 2012 by the authors.


Koyama T.,Kyoto University | Katayama T.,KANSO Technos Co. | Tanaka T.,Obayashi Corporation | Kuzuha Y.,Japan Atomic Energy Agency | Ohnishi Y.,Kyoto University
Geosystem Engineering | Year: 2013

Grouting is commonly used to decrease the hydraulic conductivity of fractured rock masses and control the groundwater inflow. Since underground facilities are constructed in various geological conditions, different types of grout material and mixing/injection methods have been developed for effective and economical grout injection. It is also important to evaluate the grout arrival distance and the range of the altered hydraulic conductivity field after grout injection. However, the mechanism of the grout injection process has not yet been clarified sufficiently due to complex chemical and physical processes during grout injection. In this study, to simulate the grout injection process, a three-dimensional numerical model based on an equivalent continuum approach was developed and applied to the in situ grout injection tests at the Grimsel test site, Switzerland. In the simulations, the injection pressure and/or the injection rate was given as a boundary condition and the total amount of injected grout (silica sol) was calculated. The breakthrough curves (grout arrival time and the time evolution of grout density) at the observation boreholes and the distribution of the altered hydraulic conductivity field were also investigated. The simulation results were also compared with the ones obtained from in situ measurements/monitoring, which showed qualitatively good agreement. © 2013 Copyright Taylor and Francis Group, LLC.


Matsui N.,Kanso Technos Co. | Songsangjinda P.,Marine Shrimp Culture Research and Development Institute | Wodehouse D.,Bangor University
Wetlands Ecology and Management | Year: 2014

A silvofishery system (SFS) of 5.2 ha, simultaneously combining aquaculture (shrimp, crab, and fish) and forestry, was studied to understand how the water/sediment qualities had remained viable for 30 years. The long life of this SFS pond contrasts sharply with a short life of many conventional, intensively managed shrimp ponds (5 years on average). Total ammonia nitrogen in the SFS water (0.06 mg l-1) was much lower than the Thai environmental safety standard for shrimp ponds (1.0 mg l-1) and approximately 0.05 % of an average conventional, intensively managed shrimp pond. Total organic nitrogen of the pond sediment was 1.47 mg g-1 which was almost half of conventional, intensively managed shrimp ponds. The flux study revealed that NH4-N was the dominant form of nitrogen, with lesser amounts of NO2-N and NO3-N, and that NH4-N was being released from the sediment into the water. Nitrogen loss from the pond, which was regarded as the denitrification rate, was estimated to be 71.5 mgN m-2 d-1, corresponded to 55 % of the total nitrogen input. As the average denitrification rate in a conventional, intensively managed shrimp pond is 13.4 %, the SFS was shown to be relatively efficient in removing accumulated nitrogen from the pond. Assuming accepted feed conversion rates, 3,340 kg of feed would have been necessary for the amount of fishery production recorded during 5 May 2005 and 22 March 2006. However, only 380 kg of trash fish was added, representing a saving of 2,960 kg of feed. Such a saving could be attributed to detritus from the mangrove trees that have been growing within the pond and algae encouraged to bloom by the shallow water depth. Therefore, it is suggested that the efficient nitrogen removal due to the high denitrification rate as well as the reduced feed input from mangrove detritus substitution, have contributed to maintaining favourable water and sediment qualities, resulting in the longevity of SFS pond. © 2014 Springer Science+Business Media Dordrecht.


Koyama T.,Kyoto University | Ohnishi Y.,Kyoto University | Takahashi K.,Suimon Gijyutu Consultant Co. | Kobayashi A.,KANSO Technos Co. | Katayama T.,KANSO Technos Co.
Harmonising Rock Engineering and the Environment - Proceedings of the 12th ISRM International Congress on Rock Mechanics | Year: 2012

Recently, underground facilities have been built under various geological conditions with limited budget, and for grouting system, more effective and economical injection method has been required. For grout injection, so far the injection method which changes the water/cement mixing ratio stepwise from high to low has been commonly used in order to inject cement into the fractured rock masses effectively. Unlike this conventional method, in the newly developed method, the water/cement mixing ratio is changed from high to low continuously. This method is more effective injection method and starts being applied to the construction of various underground facilities. In this study, to investigate the grout injection mechanism and processes, the numerical simulations were carried out considering the time-dependent grout properties. In the numerical simulations, two different grout injection methods mentioned above were simulated using the in-situ grout injection data including the change of the grout injection pressure and grout density, and the simulation results were compared with the ones obtained from the in-situ grout injection tests. The simulation results clearly showed that the change of the grout viscosity in time played important roles for the grout injection mechanism and the newly developed injection method was more effective and was able to inject more cement in shorter time comparing with the conventional injection method. The simulation results also agreed well with the ones obtained from the in-situ grout injection tests. © 2012 Taylor & Francis Group, London.

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