to managing heavy metals in bioretention is understanding their
fate in these facilities. Metals are captured by the soil
and other media during runoff treatment events. The metals
may be taken into the vegetation in the time between
events. Four heavy metals, copper, cadmium, lead,
and zinc are investigated, with three different grass species,
and using a bioretention media consisting of 30% soil, 20% mulch
and 50% sand. Two heavy metal loadings were investigated.
results show average removals of metals exceed 90% by the
bioretention media at both low and high loadings.
The metal contents in the shoots and roots of the three
plants vary greatly in different growing phases and the metal
concentrations in the shoots decrease from bottom to top.
The results of mass balance calculations show the fates
of input metals are 87.5-96.9% captured in soil media, 0.5-3.3%
accumulated in plants and 2.0-11.6% not captured by bioretention
media. The total metals captured by plants are relatively low
due to the lower biomass yields. Based on field biomass yields and laboratory metal
concentrations in plants, it appears possible and practical to
achieve metal removals of up to 25% of input by grasses.
If 20% of input metals is accumulated by plants, the lifetime of
bioretention cell will be extended by 1.25 times, which show
that plants have an important role in prolonging the lifetime of