Abstract
Stormwater runoff is identified as urban nonpoint source pollution that increasingly introduces contaminants to urban water bodies and impedes sustainable development. The pollution load of runoff varies due to the interception of different land cover types during the urban hydrological process. During the rainy season (June–August) in 2018, five different underlying surfaces (green roof, parking lot, urban road, parkway, and grassland) were selected in Guangzhou to analyze the migration characteristics of stormwater runoff pollutants. The concentrations of heavy metals, such as chromium (Cr), cadmium (Cd), lead (Pb), and mercury (Hg), as well as total nitrogen (TN), total phosphorus (TP), and polycyclic aromatic hydrocarbons (PAHs) were collected and analyzed on different underlying surfaces with the rainfall data at the beginning of a stormwater runoff event. The results showed that PAHs, heavy metals, and TP existed mainly in the form of particles; nitrogen was mainly present as ammonia and nitrate; and the TN, TP, PAHs, and heavy metal were significantly different in the stormwater runoff on each underlying surface. The pollutant concentration in urban road runoff was the highest, accounting for 40–70% of the total pollutant concentration in the stormwater runoff, and the pollutant concentration in green roof runoff was the lowest, accounting for 10–40% of the total pollutant concentration in the runoff. An obvious effect of initial rainfall erosion was observed during stormwater runoff from urban roads and parking lots, and the scouring effect on grasslands and green roofs was mainly due to the many factors affecting the underlying surface during the middle and late stages. The rates of reduction of heavy metals were the most significant. The effect of water purification was positively correlated with stormwater runoff duration. The rates of reduction of TN, heavy metals (Cr, Cd, and Hg), and PAHs in the grassland areas were 35.20 ± 26.28, 0.24 ± 10.13, 71.77 ± 10.97,32.62 ± 110.48, and 41.30 ± 8.78%, respectively. This study could provide a theoretical basis for preventing and managing pollutants in urban stormwater runoff.
Highlights
Population growth, industrial development, land use, waste emissions, and automobile exhaust have significantly increased the urban environmental load with the development of urbanization (Gimeno et al, 2014)
The Output of Heavy Metal Pollutants on Different Underlying Surfaces As shown in Figure 2, the heavy metal Cd concentration at the beginning of the stormwater runoff ranked as the parking lot, urban road, grassland, parkway, and green roof
The concentrations of grassland and green roof were higher than those of other surface runoff at the end of the stormwater lasting 40 min. This result shows that the heavy metal Cd content collected by stormwater runoff on the impermeable surface was higher
Summary
Population growth, industrial development, land use, waste emissions, and automobile exhaust have significantly increased the urban environmental load with the development of urbanization (Gimeno et al, 2014). Numerous studies on stormwater management strategies have focused on the characteristics of stormwater runoff occurring on different urban underlying surfaces (Gilbert and clausen, 2006; Ou et al, 2011; Ouyang et al, 2010), including the initial runoff erosion effect (Soller et al, 2005; Ouyang et al, 2010; Zeng et al, 2019) and runoff models and other aspects (Deletic, 1998; Yu et al, 2016; Andrzejc et al, 2020). The effects of different land cover types on runoff pollution in the same environment are not well understood
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