Currently, nitrogen dioxide NO₂ has been the subject material caused heat island effect and global warming. In this study, we researched the more effective way of removing NO₂ by using Hedera helix L. and Hedera helix cv. Glacier that added photocatalytic coating, titanium dioxide (TiO₂) and tungsten trioxide (WO₃). Furthermore, we set the two light sources for the fluorescent lamp and ultraviolet fluorescent lamp. As the result, NO₂ removal (μg/m²•h) of each plant was not influenced by the condition of light, and NO₂ removal (μg/m²•h) was increased in order from the top, WO₃ plots, TiO₂ plots and non-plant (control) plots. In addition, the photocatalytic retention rate (%) was 16.9 to 41.7% in TiO₂ plots and 1.8 to 4.0% in WO₃ plots. However, photocatalytic retention rate (%) of WO₃ plots was very few. So, we suppose to expect higher effect of NO₂ removal by improving the photocatalytic retention rate of WO₃.

To reduce costs associated with levee management, a new zoysiagrass net-planting technique was employed to stabilize a narrow levee with steep slopes. Cotton nets containing ‘Asagake’ Zoysia sprigs were spread on the levee before top dressing with 2 cm of soil, which contained varying proportions of brown earth with weed seeds from fields or decomposed granite soil (DGS) with no weed seeds from mountains. The effect of weeding, fertilizer application, and sprig size on Z. japonica coverage was also examined in the first growing season (May to September) in plastic boxes. Compared to brown earth or 50% DGS, hand weeding in July increased Z. japonica coverage in DGS containing no weed seeds. However, total plant coverage did not increase in unmixed DGS plots. In fields containing 80–90% decomposed granite, Z. japonica and total plant coverage were similar to that in 100% DGS containing no weed seeds. Fertilizer application and sprig size had little effect on increasing Z. japonica coverage. Thus, although DGS (80, 90 and 100%) promotes Z. japonica coverage better than either brown earth or 50% DGS, mixing DGS with brown earth did not appear to promote the coverage of Z. japonica and overall plant coverage in parallel.