Heavy metals

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The heavy metals noted as particularly harmful to aquatic ecosystems are:

  • Chromium(Cr),
  • Copper (Cu),
  • Lead (Pb), and
  • Zinc (Zn)[1]

Laboratory experiments on bioretention media have demonstrated that the organic matter significantly improves retention of lead (Pb), copper (Cu), and zinc (Zn) [2]. This research also found that extended detention of the stormwater in the cell did not improve this water quality benefit.

Cores of media were extracted from five 10 year old bioretention cells in Queensland, Auz and tested for a suite of heavy metals: “Although trace amounts of several heavy metals (most prominently Mn and Zn) were found in most of the basins, all heavy metal levels found in the soil were either below detectable limits, or within acceptable limits based on legislated health-based investigation levels.”[3]

  1. Feng W, Hatt BE, McCarthy DT, Fletcher TD, Deletic A. Biofilters for Stormwater Harvesting: Understanding the Treatment Performance of Key Metals That Pose a Risk for Water Use. Environ Sci Technol. 2012;46(9):5100-5108. doi:10.1021/es203396f.
  2. Gülbaz S, Kazezyilmaz-Alhan CM, Copty NK. Evaluation of Heavy Metal Removal Capacity of Bioretention Systems. Water Air Soil Pollut. 2015;226(11). doi:10.1007/s11270-015-2640-y.
  3. Lucke T, Nichols PWB. The pollution removal and stormwater reduction performance of street-side bioretention basins after ten years in operation. Sci Total Environ. 2015;536:784-792. doi:10.1016/j.scitotenv.2015.07.142.