Shigeki Harada

Decrease of non-point zinc runoff using porous concrete.

The use of porous concrete columns to decrease the amount of zinc in stormwater runoff is examined. The concentration of zinc in a simulated stormwater fluid (zinc acetate solution), fed through concrete columns (slashed circle10x10cm) decreased by 50-81%, suggesting physical adsorption of zinc by the porous concrete. We propose the use of porous concrete columns (slashed circle50x10cm) as the base of sewage traps. Longer-term, high-zinc concentration monitoring revealed that porous concrete blocks adsorb 38.6mgcm(-3) of zinc. A period of no significant zinc runoff (with an acceptable concentration of zinc in runoff of 0.03mgL(-1), a zinc concentration equal to the Japanese Environmental Standard) is estimated for 41years using a 1-ha catchment area with 20 porous concrete sewage traps. Scanning electron microscopy of the porous concrete used in this study indicates that the needle-like particles formed by hydration action significantly increase zinc adsorption. Evidence suggests that the hydrant is ettringite and has an important role in zinc adsorption, the resulting immobilization of zinc and the subsequent effects on groundwater quality.

Annual changes in the Fukushima residents’ views on the safety of water and air environments and their associations with the perception of radiation risks

Abstract Fukushima residents’ negative views on the safety of water and air environments have been a concern since the Fukushima Dai-ichi Nuclear power plant (FDNPP) accident. The objective of this study was to clarify the factors determining these negative views and their association with radiation risk perception using the opinion poll conducted by Fukushima Prefecture from 2010 to 2015. In a model, in which the objective variables were the views on the safety of water and air environments, and the explanatory variables were the regions constituting Fukushima and the age and sex of the residents, the odds ratio (OR) of the views on the safety of the water and air environments (reference region: the least affected region) was significantly low at 0.11 [95% confidence interval (CI): 0.04–0.28] to 0.18 (0.07–0.46) in the Hamadori region including the evacuation order area, from the accident in 2011 to 2015, with the exception of 2014. In another model, in which the region was excluded from the explanatory variables and radiation risk perception, the distance from the FDNPP and the air dose rate were added to the previous model as an explanatory variable, the views on the safety of the water and air environments were strongly associated with low radiation risk perception (low anxiety) in 2012–2015 [OR: 7.73 (5.25–11.4) to 10.3 (6.71–15.8)], distance from FDNPP, and age, but not with air dose rate. This result suggests that the radiation risk perception, distance from FDNPP, and age were factors determining people’s views on the safety of the water and air environment.

Adsorption by and artificial release of zinc and lead from porous concrete for recycling of adsorbed zinc and lead and of porous concrete to reduce urban non-point heavy metal runoff

This report describes the use of porous concrete at the bottom of a sewage trap to prevent runoff of non-point heavy metals into receiving waters, and, secondarily, to reduce total runoff volume during heavy rains in urbanized areas while simultaneously increasing the recharge volume of heavy-metal-free water into underground aquifers. This idea has the advantage of preventing clogging, which is fundamentally very important when using pervious materials. During actual field experiments, two important parameters were identified: maximum adsorption weight of lead and zinc by the volume of porous concrete, and heavy metal recovery rate by artificial acidification after adsorption. To understand the effect of ambient heavy metal concentration, a simple mixing system was used to adjust the concentrations of lead and zinc solutions. The concrete blocks used had been prepared for a previous study by Harada & Komuro (2010). The results showed that maximum adsorption depended on the ambient concentration, expressed as the linear isothermal theory, and that recovery depended on the final pH value (0.5 or 0.0). The dependence on pH is very important for recycling the porous concrete. A pH of 0.5 is important for recycling both heavy metals, especially zinc, (8.0-22.1% of lead and 42-74% of zinc) and porous concrete because porous concrete has not been heavily damaged by acid. However, at a pH of 0.0, the heavy metals could be recovered: 30-60% of the lead and 75-125% of the zinc. At a higher pH, such as 2.0, no release of heavy metals occurred, indicating the safety to the environment of using porous concrete, because the lowest recorded pH of rainfall in Japan is. 4.0.