Case Studies > Haddam Demonstration Site > Rain Garden > Results > Plants, Mulch & Soil

Plants, Mulch & Soil

Over the entire study period, TN, TP, Cu, Pb and Zn concentrations increased on the mulch in the gardens, and decreased in the garden soils. These results indicate that although the mulch was a sink for both TN and TP, rain garden soils were a source of both pollutants.

Mulch retained 3542 of the 3620 mg of Cu, or 98% of inputs. Pb retention on mulch was 636 g, or 36% of the total Pb inflow, and Zn was lower at 1763 g, or 16% of total Zn inflow. Plants only removed 0.1, 0, and 0.2% of inputs of Cu, Pb, and Zn, respectively. Despite the small percent uptake, Zn tissue concentrations in winterberry (Ilex verticillata) increased from 21 to 344 mg/kg. Percent increases of Zn in the two other plant species used were much lower. Although winterberry does not appear to be hyperaccumulating Zn at the Haddam site, the results of this study suggest that its potential use in overall phytoremediation should be further investigated.

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