Rain gardens are multifunctional green infrastructure for urban stormwater management. It can reduce runoff and nonpoint pollutants, as well as provide other ecosystem services such as wildlife habitat, groundwater recharge, and aesthetic values. However, despite the varied positive functions of rain gardens, the fate and behavior of the pollutants in the system are not clearly understood. Therefore, experiments were conducted to investigate changes in the concentrations and distribution of pollutants in soil, vegetation, and effluent water in the rain gardens. Artificial rainwater containing heavy metals (Cd, Cu, Pb, Ni) and nutrients (N, P) at two rainfall intensities of 2.5 mm/hr and 5.0 mm/hr was applied to four types of rain garden mesocosms (Rhododendron lateritium, Zoysia japonica, mixed plants, and control). All planted mesocosms showed better contaminant removal performance than control. The mixed plants with R.lateritium and Z. japonica showed the highest removal performance as well as the highest water retention capacity. As rainfall intensity increase, pollutant removal efficiency decreased but peak flow reduction increased. The concentrations of heavy metals and nitrogen in soils and plants increased after 30 days of experiments but phosphorous concentration did not change significantly. The concentrations of most heavy metals were higher in the herbaceous plant (Z. japonica) than in the shrub (R. lateritium) but also higher in the belowground root than in the aboveground leaves. The results showed that the mixed vegetation system is more efficient at reducing pollution and peak flows in urban stormwater runoff. Considering concentration removal performance of the study, the effluent water can be used for non-portable water and be environmentally safe, but careful site management should be considered to manage health and ecosystem risk as the pollutant concentration increase in the system.

Distribution of heavy metals and nutrients in soil, plant, and effluent water in a rain garden

2019 Fall National Meeting

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