Effect of dissolved soil organic matter on cesium adsorption by zeolite and illite.

In controlled landfill sites, soil layers are installed around radioactive waste to prevent the leaching of radioactive cesium (Cs). The Cs retention capacity of soil has been reported to be enhanced by mixing clay minerals. However, several studies have indicated that dissolved soil organic matter (DSOM) inhibits the Cs sorption by clay minerals. Therefore, this study assesses the effect of DSOM on the Cs sorption by zeolite and illite. Excitation emission matrix fluorescence spectroscopy was used for DSOM in the soil solution before and after contact with clay minerals. The results show that DSOM sorption onto clay minerals, particularly fulvic acid, inhibited Cs sorption. Batch sorption tests were conducted to obtain the sorption isotherms using two sample solutions, namely, soil and ionic solutions. Soil solution, which contained DSOM, was prepared by mixing soil and ultrapure water and filtration using a 0.3-µm glass fiver filter. Ionic solution was prepared by removing DSOM larger than 500 Da from the soil solution using dialysis. The amount of sorbed Cs in the soil solution was lower than that in the ionic solution. Comparing the Freundlich coefficients (KF) between the soil and ionic solutions, we found that the KF values of zeolite and illite for the ionic solution accounted for 6.4- and 4.4-fold higher than that for the soil solution, respectively.

Cesium and strontium loads into a combined sewer system from rainwater runoff.

In this study, combined sewage samples were taken with time in several rain events and sanitary sewage samples were taken with time in dry weather to calculate Cs and Sr loads to sewers from rainwater runoff. Cs and Sr in rainwater were present as particulate forms at first flush and the particulate Cs and Sr were mainly bound with inorganic suspended solids such as clay minerals in combined sewage samples. In addition, multiple linear regression analysis showed Cs and Sr loads from rainwater runoff could be estimated by the total amount of rainfall and antecedent dry weather days. The variation of the Sr load from rainwater to sewers was more sensitive to total amount of rainfall and antecedent dry weather days than that of the Cs load.

Tylosin degradation during manure composting and the effect of the degradation byproducts on the growth of green algae.

In this study, we investigate the tylosin degradation in sheep feces during composting. The sheep feces containing tylosin were composted using the laboratory-scale composting units. Tylosin was degraded during composting, and the half-life of tylosin degradation decreased with increasing temperature from 40 °C to 65 °C. The tylosin degradation in sheep feces can be attributed to the microorganisms in the feces and not to heating because tylosin did not degrade over a period of 48 h at temperatures of 0 °C-65 °C in sterilized water. The artificial rainwater solution extracted from the composted sample did not inhibit the growth of Raphidocelis subcapitata, a type of green alga. Our results indicate that composting the feces containing tylosin is effective in degrading tylosin, which may result in the preservation of agricultural fields as well as nearby aquatic environments.

Sorption behavior of selenium on humic acid under increasing selenium concentration or increasing solid/liquid ratio.

The sorption of selenium (Se) on humic acid (HA) was investigated in order to better understand the fate of stable and radioactive Se in soils and sediments. An ultrafiltration technique was used to determine size distributions of HA-sorbed-Se when increasing Se concentration and solid/liquid ratio. The results showed that the Se sorption onto HA followed the Freundlich isotherm. No solid/liquid ratio-dependence was observed especially when <3 kDa molecular size fraction was used from solid/liquid separation. The Freundlich isotherm parameters K(F) and n obtained using the <3 kDa molecular size fraction for solid/liquid separation were 3.7 x 10(2) and 0.82, respectively. In addition, since dissolved HA increased with decreased ionic strength in the HA suspension, ionic strength could promote aggregation of HA. The conformational change of HA could affect the sorption behavior of Se on HA.

Fate of stable strontium in the sewage treatment process as an analog for radiostrontium released by nuclear accidents.

Radionuclides were widely released into the environment due to the nuclear accident at the Fukushima Daiichi Nuclear Power Plant. Some of these radionuclides have flowed into municipal sewage treatment plants through sewer systems. We have observed the fate of stable Sr in the sewage treatment process as a means to predict the fate of radiostrontium. Concentrations of stable Sr were determined in sewage influent, effluent, dewatered sludge, and incinerated sewage sludge ash collected from a sewage treatment plant once a month from July to December 2011. In the mass balance of Sr in the sewage treatment plant, 76% of the Sr entering the plant was discharged to the receiving water on average. Additionally, 14% of the Sr flowing through the plant was transferred to the sewage sludge and then concentrated in the sludge ash without being released to the atmosphere. We also investigated Sr sorption by activated sludge in a batch experiment. Measurements at 3 and 6h after the contact showed Sr was sorbed in the activated sludge; however, the measurements indicated Sr desorption from activated sludge occurred 48 h after the contact.

Fate of radiocesium in sewage treatment process released by the nuclear accident at Fukushima.

The nuclear accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) which occurred after the Great East Japan Earthquake on March 11, 2011 resulted in releases of radionuclides such as (134)Cs (half-life:T1/2=2.06 yr), (137)Cs (T1/2=30.04 yr) and (131)I (T1/2=8.05 d) to the environment. For this paper, we observed the monthly variations of radiocesium ((134)Cs and (137)Cs) and stable Cs concentrations in influent, effluent, sewage sludge, and sludge ash collected from a sewage treatment plant 280 km north of the FDNPP from July to December, 2011. Using the stable Cs results, we concluded the mass balance of Cs in the sewage treatment plant showed that about 10% of the Cs entering the sewage treatment plant would be transferred to the sewage sludge, and then Cs in the sewage sludge was totally recovered in the sludge ash. The behavior of Cs was similar to that of Rb, but it was not similar to that of K in the sewage treatment process.