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We investigated the role of extracellular polymeric substances (EPS) in the adhesion of Pseudomonas fluorescens, Bacillus subtilis, and Escherichia coli on four variable charge soils. Cation exchange resin was used to remove surface-bound EPS. It was observed that soil cation exchange capacity (CEC) and Fe2O3 contents greatly influenced their adhesion ability for the bacteria. The maximum adhesion capacity of Ultisol from Guangzhou for E. coli, P. fluorescens, and B. subtilis were 609.3, 1113.9, and 2169.2 mg g−1, respectively. The values were 434.7, 837.5, and 2067.9 mg g−1 for Oxisol and 134, 632.3, and 408.5 mg g−1 for Alfisol. EPS removal decreased the adhesion of the bacteria in variable charge soils and thus increased their mobility in the soils. However, EPS removal did not greatly alter the electrokinetic properties of bacterial cells. There was significant (p ˃ 0.05) difference in the rates of deprotonation between the different bacteria species. The deprotonation rates were 53.8, 71.7, and 5.6% for native P. fluorescens, B. subtilis, and E. coli, and 22.4, 63.9, and 6.5% for the EPS-free bacteria, respectively. Therefore, bacterial mobility in variable charge soils is greatly influenced by the concentration of EPS and CEC as well as Fe2O3 contents of the soils. [ABSTRACT FROM AUTHOR]

Green roof stormwater retention performance is fundamentally related to design configurations and climates. Efficient tools for assessing stormwater retention performance of green roofs with various configurations in different climates are highly desirable for practical applications. In this study, a hydrological model which can be used to simulate dynamic changes in moisture content and evapotranspiration of green roofs is developed and tested (with average Nash-Sutcliffe Efficiency of 0.8197 for calibration and 0.8252 for verification) using monitoring data (2018–2019) of four green roofs with various configurations. The model is applied to simulate long-term (1970–2018) moisture content, actual evapotranspiration, and retention performance of green roofs in eight cities across different climates of China. Green roofs built with engineered soil and Portulaca grandiflora show the largest evapotranspiration and thus provide the largest stormwater retention rates (R r), while green roofs with light growing medium and Sedum lineare show the lowest evapotranspiration and R r. R r of green roofs increases as climate changes from humid to arid. Green roofs at Guangzhou (humid climate) provide the lowest R r (28% ± 3%) caused by plenty of rainfall (1827 mm), while green roofs at Urumqi (desert climate) show the lowest mean annual actual evapotranspiration (167–269 mm) but provide the largest R r (84% ± 5%) as a result of the lowest annual rainfall (282 mm). The results highlight that stormwater retention performance of green roofs could be enhanced through configuration optimization. However, a limiting factor in improving green roofs water retention rates may be the peculiarity of local climatic conditions. [Display omitted] • A green roof (GR) hydrological model is developed and tested with observed data. • Long-term stormwater retention rates (R r) of GRs is assessed using the model. • R r Increases as climate changes from humid to arid. • Optimizing configurations can improve R r to the limitations determined by climates. [ABSTRACT FROM AUTHOR]