Enrichment Evaluation of Heavy Metals from Stormwater Runoff to Soil and Shrubs in Bioretention Facilities

Yongwei Gong,Guohong Zhang,Linmei Nie,Yan Hao

doi:10.3390/w14040638

Yongwei Gong, Guohong Zhang + Show 2 more

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https://doi.org/10.3390/w14040638

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Abstract

Bioretention facilities with different inflow concentrations, growing media and plants were examined to determine whether the soil in these facilities was polluted with heavy metals and whether runoff had obvious toxic effects on plants. Using Beijing soil background value as the standard, the soils were evaluated by bioaccumulation index and single factor index. The results show that stormwater runoff containing Cu caused slight pollution in soils, and stormwater runoff containing Zn and Pb was not polluted. Nemerow comprehensive index evaluation revealed that the heavy metals content in the facilities containing vermiculite (a yellow or brown mineral found as an alteration product of mica and other minerals, used for insulation or as a moisture-retentive medium for growing plants) and perlite (a form of obsidian characterized by spherulites formed by cracking of the volcanic glass during cooling, used as insulation or in plant growth media) were higher than the standard. High influent concentration caused significantly higher heavy metals content in plants. While Pb accumulation in the two studied plants was the highest, Cu and Zn accumulation, which are essential for plant growth, was relatively low. The contents of the three heavy metals in the studied plants also exceeded their corresponding critical values.

Highlights

In recent years, stormwater runoff pollution has become a more serious and important factor, deteriorating the water quality of urban rivers and lakes in most cities in China
Analysis of the effect of different road stormwater runoff concentrations revealed that, the Cu content in the soil of SS-H with high influent concentration showed an overall increasing trend, the final increase in the Cu content in the soil was only 147% higher than the background value recorded before the start of the experiment and was significantly lower that noted in SS-L with low influent concentration
A bioretention system was set up to perform experiments designed with different media types and influent concentrations to determine the impact of stormwater runoff containing three heavy metals, Cu, Zn, and Pb, on the soil and plants in the bioretention facility

Summary

Introduction

Stormwater runoff pollution has become a more serious and important factor, deteriorating the water quality of urban rivers and lakes in most cities in China. To mitigate the problems of urban flood and runoff pollution, China is vigorously promoting the construction of a Sponge City. The road stormwater runoff produced during the Sponge City construction process might disturb plant growth. Discharge of road stormwater runoff into green space is prohibited in many areas, which undoubtedly hinders the construction of Sponge Cities in corresponding areas. Bioretention facility have become one of the most common and important measures in the source control of Sponge City construction because of the obvious removal effect of substrates and plants on rainwater runoff pollution [1,2,3], so it is most obviously affected by this regulation

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