Toxins can be removed and pollutants can be trapped through planting rain gardens in urban areas, according to a recent study. The local water quality can also be improved as a result of this. The concept of rain gardens has been around for 10 to 15 years, but there has not been much research with regard to the subject. US researchers at the University of Connecticut planted two rain gardens and frequently monitored them over a two-year period to see how effectively they absorbed a range of pollutants.
They found that the gardens significantly reduced the concentration of fertilizers, oil and particulates reaching storm drains. The study appeared in the journal Environmental Science and Technology and says a shallow depression in a garden containing bark mulch and shrubs can remove up to 99% of toxins. Most of the rain that falls on cities lands on impervious surfaces, such as roads, where it absorbs pollutants before it finally drains away.
The US Environmental Protection Agency estimates that built-up urban areas generate nine times the amount of runoff water than woodlands of a similar size. As the percentage of the world's population living in cities continues to grow, the problems of flooding and pollution are set to increase. Michael Dietz, one of the researchers, hopes their findings will encourage town planners across the globe to consider using rain gardens.