The relationship between typical heavy metal content and physiological indexes of shrubs in bioretention facilities

Abstract

Bioretention facilities have been widely constructed, but it is unknown whether rainfall runoff containing pollutants will hurt the plants in bioretention facilities. Experiments were carried out to explore the relationship between the heavy metal (Cd and Pb) contents of four shrubs and three physiological indexes. The results show the following: (1) The heavy metal absorption of shrubs may be directly proportional to the heavy metal content in stormwater runoff. (2) For the experimental devices, sand/soil-low concentration (SS-L) and sand/soil-high concentration (SS-H), except that the contents of Cd and Pb of L. vicaryi in SS-H showed a trend of increasing first and then decreasing, the contents of heavy metals in other shrubs showed a gradual increase. (3) For SS-L, the net photosynthetic rate (NPR) and transpiration rate (TR) of R. xanthina were in direct proportion to the contents of Cd and Pb in vivo. The NPRs and TRs of the other three shrubs and the chlorophyll content (CC) of L. vicaryi presented an inversely proportional relationship. For SS-H, the NPR of L. vicaryi was in direct proportion to its Cd and Pb contents. Almost all other conditions showed an inverse relationship.