Biochar and vegetation effects on discharge water quality from organic-substrate green roofs.

Green roofs have been increasingly used to improve stormwater management, but poor vegetation performance on roof systems, varying with vegetation type, can degrade discharge quality. Biochar has been suggested as an effective substrate additive for green roofs to improve plant performance and discharge quality. However, research on the effects of biochar and vegetation on discharge quality in the long term is lacking and the underlying mechanisms involved are unclear. We examined the effects of biochar amendment and vegetation on discharge quality on organic-substrate green roofs with pre-grown sedum mats and direct-seeded native plants for three years and investigated the key factors influencing discharge quality. Sedum mats reduced the leaching of nutrients and particulate matter by 6-64% relative to native plants, largely due to the higher initial vegetation cover of the former. Biochar addition to sedum mat green roofs resulted in the best integrated water quality due to enhanced plant cover and sorption effects. Structural equation modeling revealed that nutrient leaching was primarily influenced by rainfall depth, time, vegetation cover, and substrate pH. Although biochar-amended sedum mats showed better discharge quality from organic-substrate green roofs, additional ecosystem services may be provided by native plants, suggesting future research to optimize plant composition and cover and biochar properties for sustainable green roofs.

Synthesis of an aggregation-induced emission (AIE) dye with pH-sensitivity based on tetraphenylethylene-pyridine for fluorescent nanoparticles and its applications in bioimaging and in vitro anti-tumor effect.

In this contribution, a novel AIE monomers 2-(4-styrylphenyl)- 1,2-diphenylvinyl)styryl)pyridine (SDVPY) with smart fluorescent pH-sensitivity basing on tetraphenylethylene-pyridine were successfully synthesized for the first time, subsequently, a series of amphiphilic copolymers PEG-PY were achieved by reversible addition-fragmentation chain transfer (RAFT) polymerization of SDVPY and poly(ethylene glycol) methacrylate (PEGMA), which would self-assemble in water solution to form core-shell nanoparticles (PEG-PY FONs) with about 150 nm diameter. The PEG-PY FONs showed obvious fluorescence response to Fe3+, HCO3- and CO32- ions in aqueous solution owing to their smart pH-sensitivity and AIE characteristics, and their maximum emission wavelength could reversibly change from 525 nm to 624 nm. The as-prepared PEG-PY FONs showed also prospective application in cells imaging with the variable fluorescence for different pH cells micro-environment. When PEG-PY copolymers self-assembled with the anti-tumor drug paclitaxel (PTX), the obtained PY-PTX FONs could effectively deliver and release PTX with pH-sensitivity, and could be easily internalized by A549 cells and located at the cytoplasm with high cytotoxicity, which was further confirmed by the Calcein-AM/PI staining of dead and alive A549 cells. Moreover, the flow cytometry results indicated that the PY-PTX FONs could obviously induce the apoptosis of A549 cells, which further showed the great potential of PY-PTX FONs in the application of tumors therapy.

Biochar Benefits Green Infrastructure: Global Meta-Analysis and Synthesis.

Urbanization has degraded ecosystem services on a global scale, and cities are vulnerable to long-term stresses and risks exacerbated by climate change. Green infrastructure (GI) has been increasingly implemented in cities to improve ecosystem functions and enhance city resilience, yet GI degradation or failure is common. Biochar has been recently suggested as an ideal substrate additive for a range of GI types due to its favorable properties; however, the generality of biochar benefits the GI ecosystem function, and the underlying mechanisms remain unclear. Here, we present a global meta-analysis and synthesis and demonstrate that biochar additions pervasively benefit a wide range of ecosystem functions on GI. Biochar applications were found to improve substrate water retention capacity by 23% and enhance substrate nutrients by 12-31%, contributing to a 33% increase in plant total biomass. Improved substrate physicochemical properties and plant growth together reduce discharge water volume and improve discharge water quality from GI. In addition, biochar increases microbial biomass on GI by ∼150% due to the presence of biochar pores and enhanced microbial growth conditions, while also reducing CO2 and N2O emissions. Overall results suggest that biochar has great potential to enhance GI ecosystem functions as well as urban sustainability and resilience.

Biochar granulation reduces substrate erosion on green roofs.

Green roofs are exposed to high winds and harsh environmental conditions that can degrade vegetation and erode substrate material, with negative consequences to ecosystem services. Biochar has been promoted as an effective substrate additive to enhance plant performance, but unprocessed biochars are susceptible to wind and water erosion. Applications of granulated biochars or chemical dust suppressants are suggested as a means to mitigate biochar and substrate erosion; however, research on biochar type and chemical dust suppressant use on biochar and substrate erosion is lacking. Vegetation is a crucial factor that influences substrate erosion, yet plant responses may vary with biochar type and chemical dust suppressant; thus, the effects of possible mitigation measures on biochar and substrate erosion are unclear. We investigated the effects of surface-applied granulated and unprocessed biochars and an organic dust suppressant (Entac™) on biochar and substrate erosion on green roofs with Sedum album L. and a native plant mix. Our results show that 94% of unprocessed biochars were lost from green roofs after 2 years regardless of the Entac™ amendment, likely due to the lightweight nature and fragmentation of biochar particles. In contrast, granulation of biochars reduced the biochar erosion and total substrate erosion by 74% and 39%, respectively, possibly due to enhanced biochar bulk density and particle size and improved moisture retention of biochar-amended substrates. Additionally, Sedum album better reduced biochar and substrate erosion than the native plant mix, likely due to rapid development of high vegetation cover that reduced wind exposure and enhanced substrate moisture retention. We conclude that applications of granulated biochars can substantially reduce biochar and substrate erosion on green roofs, improving green roof sustainability. Supplementary Information: The online version contains supplementary material available at 10.1007/s42773-022-00186-7.

Biochar granulation, particle size, and vegetation effects on leachate water quality from a green roof substrate.

Biochar, due to its favourable physiochemical properties, has been promoted as an ideal substrate additive on green roofs, with potential benefits to hydrological function. However, biochar is susceptible to water erosion, which may result in biochar loss and water pollution. The use of granulated biochars or biochars in large particle sizes could potentially alleviate biochar erosion loss, but effects on leachate quality have not been investigated. Also, biochar type and particle size influence plant performance, and effects on discharge quality may vary with vegetation. We assessed the effects of unprocessed and granulated biochars at five (0.25-0.5 mm, 0.5-1 mm, 1-2 mm, 2-2.8 mm, 2.8-4 mm) and four (1-2 mm, 2-2.8 mm, 2.8-4 mm, and 4-6.3 mm) particle size ranges, respectively, on leachate quality on a typical green roof substrate, with presence and absence of vegetation (Agastache foeniculum - a drought-tolerant native forb). We evaluated integrated leachate quality using the CCME Water Quality Index (WQI). Unprocessed biochars reduced nutrient leaching due to increased water retention capacity (WRC) and total porosity. In contrast, granulated biochars, although showing less pronounced mitigation of nutrient leaching, reduced total suspended solids (TSS) and improved WQI in leachate due to enhanced plant performance. In addition, small biochar particles better reduced nutrient leaching and particle loss than large biochar particles, possibly due to increased WRC and formation of water-stable aggregates. The presence of vegetation generally reduced the leaching of nutrients and TSS, consistent with plant nutrient uptake and root substrate stabilization. However, plant biomass was correlated with increased total N leaching, likely due to litter inputs and rapid litter decomposition. We conclude that applications of granulated biochars may best improve discharge quality from green roofs through sorption effects and by enhancing plant performance.

Biochar granulation enhances plant performance on a green roof substrate.

Green roofs have been widely promoted as a means to enhance ecosystem services in cities, but roofs present a harsh growing environment for plants. Biochar is suggested to be a highly beneficial substrate additive for green roof systems due to its low weight, high nutrient and water retention capacity, and recalcitrance. However, biochar is susceptible to wind and water erosion, which may result in biochar loss and negative environmental impacts. Applications of biochar as large particles or in granulated form may mitigate biochar erosion potential, but relevant data on plant performance and substrate properties are lacking. We examined the effects of granulated and conventional biochars at a range of particle sizes on plant performance of the drought-tolerant forb Agastache foeniculum. We found that granulated biochar strongly enhanced plant growth, reproduction, and physiological status, acting to neutralize pH and enhance water retention capacity of the substrate. In contrast, although conventional biochar reduced substrate bulk density and enhanced substrate total porosity and water retention capacity, it suppressed plant growth. Our results also suggest that granulated biochar at intermediate particle sizes (2-2.8 mm) best enhanced plant performance. We conclude that use of granulated biochars on green roofs can strongly promote plant performance while increasing water infiltration and retention.