Study on the characteristics of greenhouse gas emissions from bioretention facilities with different media

Bioretention facilities were most widely used green stormwater infrastructures. The literature reviews mainly focus on the pollutant removal of bioretention facilities on stormwater runoff. However, there is a knowledge gaps of systematic research on the characteristics of greenhouse gases emission during carbon and nitrogen removal process in bioretention facilities. Focus on above problems, the laboratory scale experiments were processed to investigate the emission characteristics of CO₂, CH₄ and N₂O in bioretention facilities, and the emission flux, cumulative emission and global warming potential (GWP) were evaluated under different bioretention medias. The results showed that under the experimental conditions, the average emission fluxes of CO₂ and CH₄ in the bioretention facilities with zeolite as media were the highest, which were 480.70 mg/(m²·h) and 35.92 μg/(m²·h), respectively; the average emission flux of N₂O in bioretention facilities with fine sand as media was the highest，which was 13.33μg/(m²·h).On the whole, the GWP of bioretention facilities with fine sand as media was the smallest, which was 137.60 kgCO₂/hm². In terms of carbon emission reduction, the COD removal rate under different medias of bioretention facilities were all over than 80%, and the COD removal rate of bioretention facilities with zeolite as media was the highest, which was 93.92%. Considering the greenhouse gas and the runoff volume reduction, fine sand should be prefer selected as bioretention’s media.