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Increasing urbanization and the associated sealing of areas and the use of storm sewer systems for drainage not only increase the risk of flooding but also reduce water quality in streams into which stormwater is discharged. Green infrastructure (GI) measures are applied with the aim of managing this stormwater sustainably and reducing the associated risks. To this end, a quantitative–qualitative approach was developed to simulate GI—namely, rain gardens, bioretention cells, and vegetative bioswales—at the urban catchment scale. The findings highlight the potential of applying GI measures to managing stormwater more effectively in urban environments and mitigating its negative pollution-related impacts. For the housing estate analyzed, a simulated implementation of GI resulted in a reduction in pollution, measured as total nitrogen (N; 9–52%), nitrate-N (5–30%), total phosphorus (11–59%), chemical oxygen demand (8–46%), total suspended solids (13–73%), copper (12–64%), zinc (Zn; 16–87%), polycyclic aromatic hydrocarbons (16–91%), and the hydrocarbon oil index (HOI; 15–85%). Reducing the concentrations of pollutants minimizes the risk to human health determined via the HOI from a low-risk level to zero risk and reduces the ecological risk in terms of Zn pollution from a significant risk to a low risk of adverse effects. The modeling conducted clearly shows that the GI solutions implemented facilitated a quantitative reduction and a qualitative improvement in stormwater, which is crucial from an environmental perspective and ensures a sustainable approach to stormwater management. Lowering the levels of stormwater pollution through the implementation of GI will consequently lower the environmental burden of pollutants in urban areas. [ABSTRACT FROM AUTHOR]

The use of nature-based solutions (NBSs) for hazard mitigation is increasing. In this study, we review the use of NBSs for flood mitigation using a strengths, weaknesses, opportunities, and threats (SWOT) analysis framework for commonly used NBSs. Approaches reviewed include retention and detention systems, bioretention systems, landcover and soil management, river naturalisation and floodplain management, and constructed and natural wetlands. Existing tools for identification and quantification of direct benefits and co-benefits of NBSs are then reviewed. Finally, approaches to the modelling of NBSs are discussed, including the type of model and model parameterisation. After outlining knowledge gaps within the current literature and research, a roadmap for development, modelling, and implementation of NBSs is presented. [ABSTRACT FROM AUTHOR]

Urban nature-based solutions (NBSs) are widely implemented to collect, store, and infiltrate stormwater. This study addressed infiltration rate as a measure of the performance of bioretention solutions. Quick scan research was conducted, starting with mapping over 25 locations of implemented green infrastructure in Riga, Latvia. Basic information, such as location, characteristics, as well as photos and videos, has been uploaded to the open-source database ClimateScan. From this, eight bioswales installed in the period 2017–2022 were selected for hydraulic testing, measuring the infiltration capacity of bio-retention solutions. The results show a high temporal and spatial variation of infiltration rate for the bioswales, even those developed with similar designs: 0.1 to 7.7 m/d, mean 2.0 m/d, coefficient of variation 1.0. The infiltration capacity decreased after saturation: a 30% to 58% decrease in infiltration rate after refilling storage volume. The variation in infiltration rate as well as infiltration rate decrease on saturation is similar to other full-scale studies done internationally. The infiltration rate of most bioswales falls within the range specified by international guidelines, all swales empty within 48 h. Most bioswales empty several times within one day, questioning the effectiveness of water retention and water availability for dry periods. The results are of importance for stakeholders involved in the implementation of NBS and will be used to set up Latvian guidelines for design, construction, and maintenance. [ABSTRACT FROM AUTHOR]

Stormwater transports directly into rivers eroded soil, animal wastes, pesticides, fertilizers and other potential pollutants. Bioretention is often designed to capture and treat it using the natural properties of soil and plants. However, selection of appropriate media structure and plants need to be adequately studied. This study investigated the performance of bioretention system in removing stormwater pollutants using Dracaena, a local plant, also called Song of India Plants. Physical model of three Columns A, B and C were developed having five layered filter media of different configurations whose materials were analyzed to meet the design standards. The plants were introduced into Columns A and C leaving out B as control experiment. The quality parameters were determined before and after treatments at ages 10, 20, 30 and 40 days when Dracaena plants were introduced into bioretention models. The results showed that the bioretention model drastically improved stormwater quality by reducing values of electrical conductivity, total coliforms (TC), fecal coliforms (FC), total suspended solids (TSS) and biochemical oxygen demand (BOD) as compared to the tested raw stormwater samples. The filter media in both Columns A and C substantially reduced the pollutant levels to standard discharge limits for all parameters tested such as TSS, TC, FC, BOD and nitrates. BOD fell within the recommended standard after 20 days of treatment in Column C with considerable reduction in TC and FC by 68.9% and 75.4% respectively when compared to raw stormwater sample. However, Column C completely removed TC and FC at 40 days which are pathogen indicators in wastewater. This study would be useful to the stakeholders for sustainable stormwater treatment and management. [ABSTRACT FROM AUTHOR]

Stormwater transports directly into rivers eroded soil, animal wastes, pesticides, fertilizers and other potential pollutants. Bioretention is often designed to capture and treat it using the natural properties of soil and plants. However, selection of appropriate media structure and plants need to be adequately studied. This study investigated the performance of bioretention system in removing stormwater pollutants using Dracaena, a local plant, also called Song of India Plants. Physical model of three Columns A, B and C were developed having five layered filter media of different configurations whose materials were analyzed to meet the design standards. The plants were introduced into Columns A and C leaving out B as control experiment. The quality parameters were determined before and after treatments at ages 10, 20, 30 and 40 days when Dracaena plants were introduced into bioretention models. The results showed that the bioretention model drastically improved stormwater quality by reducing values of Electrical Conductivity, Total Coliforms (TC), fecal Coliforms (FC), Total Suspended Solids (TSS) and Biochemical Oxygen Demand (BOD) as compared to the tested raw stormwater samples. The filter media in both Columns A and C substantially reduced the pollutant levels to standard discharge limits for all parameters tested such as TSS, TC, FC, BOD and nitrates. BOD fell within the recommended standard after 20 days of treatment in Column C with considerable reduction in TC and FC by 68.9 % and 75.4 % respectively when compared to raw stormwater sample. However, Column C completely removed TC and FC at 40 days which are pathogen indicators in wastewater. This study would be useful to the stakeholders for sustainable stormwater treatment and management.

Bioretention can be an efficient measure of stormwater treatment. The bioretention system has been globally adapted for controlling rainfall-runoff volume and removing pollutants. However, there is a lack of systematic analysis of some hydrological processes in the bioretention facility, such as the transportation of rainfall-runoff (event water) and soil water (pre-event water). This research uniquely applied stable isotope tracing to a bioretention system to investigate the transport of rainfall-runoff and the movement of soil water in a bioretention column. The stable isotope tracing method is helpful for determining the transport process of water and is expected to enhance our understanding of bioretention systems. The ratio of the event rainfall-runoff and the pre-event soil water in the bottom outflow of bioretention columns was calculated by the stable isotope bivariate mixing model based on the oxygen and hydrogen stable isotopic data from continuous testing in the discharge of bioretention column. The time-varying proportion of event water and pre-event water in the hydrographic curve reveals that the outflow process of soil water is divided into three stages. In the early stage, all the outflow was soil water, accounting for about 6–13% of the total outflow. In the middle stage, the proportion of soil water rapidly decreased from 100% to 20% within a few minutes. In the later stage, the soil water proportion decreased slowly from 20% to 0%. The outflow of soil water accounted for more than 36% of the total outflow and decreased with the extension of the drought period. Soil water is a critical part of the bottom outflow of bioretention columns, and the influence of soil water on the hydrological effect of bioretention columns cannot be ignored. [ABSTRACT FROM AUTHOR]

Bioretention systems are a low-impact development (LID) measure to effectively control stormwater runoff and reduce pollutant concentrations. In this paper, three groups of bioretention cells with different filling materials (1# bioretention soil media (BSM), 2# BSM + 5% biochar, and 3# BSM +5% biochar +biological filler) were constructed to analyze the pollutant removal characteristics and microbial action under different simulated rainfall conditions. Results showed that the overall pollutant removal capacity of systems 2# and 3# was higher than that of system 1#, with system 3# having the lowest effluent concentrations of 2.71 mg/L for total nitrogen (TN) and 64.3 mg/L for chemical oxygen demand (COD). The load reduction effect for heavy metals of the three systems was ranked as 2# > 1# > 3#, and average load reduction rates were 80.3, 75.1, and 84.8% for Cu, Pb, and Zn in 2#. Microbial community analysis indicated that Proteobacteria and Firmicutes were the absolute dominant bacteria of the three bioretention systems, and the dominant genera included Bacillus, Hyphomicrobium, Micrococcaceae, and Nitrospira. In addition, the total number of denitrifying functional bacteria genera in systems 2# and 3# was increased by 1.39 and 52.1% compared to system 1#. HIGHLIGHTS The bioretention system of composite filler coupled with the water storage area was constructed for advanced treatment of stormwater runoff.; The overall pollutant removal capacity of the modified bioretention systems 2# (BSM + 5%BC) and 3# (BSM + 5%BC + BM) was improved.; The total number of denitrifying functional bacteria genera in system 3# (BSM + 5%BC + BM) was increased by 52.1% compared to system 1# (BSM).;

The urban development increase in the built-up areas leads to more impervious areas with the consequence of larger runoff. Undeniably, this excess water has many benefits. Low-impact development (LID) is one of the innovations to conserve wasted runoff water. The two LID scenarios (water storage – WS; infiltration – I) under different rainfall depths (20, 25, 30, 35 mm) are assessed using Storm Water Management Model (SWMM) and analyzed based on their benefit–cost. This study aims to evaluate the hydrological performance and the benefit–cost ratio to identify the optimal LID design. The benefit calculation is not only projected by runoff reduction aspects, but also the other opportunities aspects. Based on the hydrological performance, scenario I shows a higher runoff reduction performance than scenario WS. Based on the benefits aspects studied, scenario I provides greater benefits with more cost than the WS scenario. Rainfall depth influenced the life cycle cost with 20-mm WS scenario experiencing faster payback period than other scenarios. HIGHLIGHTS Scenario infiltration excels in reducing runoff, particularly in low rainfall conditions.; Scenario water storage with 20-mm rainfall depth offers the best cost-effectiveness, but sensitivity to costs and discount rate emphasized.;

The use of nature-based solutions (NBSs) for hazard mitigation is increasing. In this study, we review the use of NBSs for flood mitigation using a strengths, weaknesses, opportunities, and threats (SWOT) analysis framework for commonly used NBSs. Approaches reviewed include retention and detention systems, bioretention systems, landcover and soil management, river naturalisation and floodplain management, and constructed and natural wetlands. Existing tools for identification and quantification of direct benefits and co-benefits of NBSs are then reviewed. Finally, approaches to the modelling of NBSs are discussed, including the type of model and model parameterisation. After outlining knowledge gaps within the current literature and research, a roadmap for development, modelling, and implementation of NBSs is presented.

Urban nature-based solutions (NBSs) are widely implemented to collect, store, and infiltrate stormwater. This study addressed infiltration rate as a measure of the performance of bioretention solutions. Quick scan research was conducted, starting with mapping over 25 locations of implemented green infrastructure in Riga, Latvia. Basic information, such as location, characteristics, as well as photos and videos, has been uploaded to the open-source database ClimateScan. From this, eight bioswales installed in the period 2017–2022 were selected for hydraulic testing, measuring the infiltration capacity of bio-retention solutions. The results show a high temporal and spatial variation of infiltration rate for the bioswales, even those developed with similar designs: 0.1 to 7.7 m/d, mean 2.0 m/d, coefficient of variation 1.0. The infiltration capacity decreased after saturation: a 30% to 58% decrease in infiltration rate after refilling storage volume. The variation in infiltration rate as well as infiltration rate decrease on saturation is similar to other full-scale studies done internationally. The infiltration rate of most bioswales falls within the range specified by international guidelines, all swales empty within 48 h. Most bioswales empty several times within one day, questioning the effectiveness of water retention and water availability for dry periods. The results are of importance for stakeholders involved in the implementation of NBS and will be used to set up Latvian guidelines for design, construction, and maintenance.

Bioretention practices have become a common way to protect natural waterways in urban and suburban landscapes across the United States. However, optimal design, implementation, operation, and maintenance are still in need of study. A field survey of 52 bioretention practices was conducted in Davidson County, Tennessee, to address research questions related to operation and maintenance. A suite of site conditions were documented, such as size, signs of erosion, and dominant surface cover. Samples were collected from the surface of the engineered media layer and analyzed for organic matter content and bulk density. Vegetation was described in terms of dominant species and canopy cover. On average, the organic matter content of media under plant‐based mulch cover was significantly greater than that under rock cover (p = 0.002). Bulk density of the surface media is strongly and inversely correlated to organic matter content; bulk density did not generally vary with bioretention area age and was highly variable within treatments. On average, the bulk density of the media under the plant‐based mulch cover was significantly less than that under the rock cover. Media under the composite treatments had similar bulk density to both the plant‐based mulch (p = 0.233) and the rock covers (p = 0.132). Plant canopy did not surpass 70% in practices with bulk density values above 1.55 g/cm3. These results suggest that consideration should be made regarding the tradeoffs between utilizing rock coverings and potential for plant establishment impacts. [ABSTRACT FROM AUTHOR]

In this study, lab-scale bioretention cells were designed for the investigation of antibiotic-resistant bacteria (ARB) outflow profiles at different depths, effects of adsorption and transmission, as well as modelling evaluation of ARB outflow risks using the common decay models (e.g., first-order decay models). ARB outflow was first found in the upper layers (after 100 days of the operation) with the lowest transmission frequencies of antibiotic resistance. Although the adsorption of ARB onto the substrate and its surface biofilms was effective with the maximum amount of ARB adsorbed (Qmax) reaching 108 CFU/g of the substrate and 107 CFU/g of biofilms, ARB outflow was detected in the bottom outlets after over 4 months of operation, reflecting that there was still a risk of antibiotic resistance through the treatment of bioretention cells. ARB outflow for both upper and middle outlets could be well described by third-order polynomial equations with correlation coefficients 0.9067 (p = 0.0002) and 0.9780 (p < 0.0001), respectively, where there were both positive and negative relationships between outflow ARB and inflow ARB, confirming the combined action of mechanisms blocking ARB outflow (e.g., substrate adsorption) and promoting ARB outflow (like transmission). These suggested two potential controlling approaches for ARB outflow from stormwater bioretention cells. HIGHLIGHTS Antibiotic-resistant bacteria (ARB) outflow appeared first in upper layers with the lowest transmission frequencies.; ARB adsorption by substrate and its surface biofilms was found to be effective.; Antibiotic resistance transmission was not the only decisive factor for ARB outflow.; ARB outflow could not be described by the conventional first-order kinetics.;

The urban heat island (UHI) problem is essential for urban living, significantly worldwide urban areas. The preliminary studies found that rising temperatures are proportional to the city’s density and affect human outdoor thermal comfort, which is related to the increasing demand for real estate development, such as the condominium projects located in the city. This research will identify the relationship between outdoor thermal comfort and the bioretention asset to support sustainable city development. Then, this result conducts the outdoor area design guideline for real estate development with nature-based solution responsibility by using bioretention based on the water-sensitive urban design concept. The results show that CASE-03: bioretention combined with large trees can provide additional outdoor thermal comfort during daytime. A preliminary study of the outdoor thermal impacts that affected outdoor thermal comfort and the results will be used as a sustainable guideline for landscape architecture practices in future developments in the city.

Low-Impact Developments (LIDs), like green roofs and bioretention cells, are vital for managing stormwater and reducing pollution. Amidst climate change, assessing both current and future LID systems is crucial. This study utilizes variably saturated flow modeling with the HYDRUS software (version 4.17) to analyze ten locations in Ontario, Canada, focusing on Toronto. Historical and projected climate data are used in flow modeling to assess long-term impacts. Future predicted storms, representing extreme precipitation events, derived from a regional climate model, were also used in the flow modeling. This enabled a comprehensive evaluation of LID performance under an evolving climate. A robust methodology is developed to analyze LID designs, exploring parameters like water inflow volumes, peak intensity, time delays, runoff dynamics, and ponding patterns. The findings indicate potential declines in LID performance attributed to rising water volumes, resulting in notable changes in infiltration for green roofs (100%) and bioretention facilities (50%) compared to historical conditions. Future climate predicted storms indicate reduced peak reductions and shorter time delays for green roofs, posing risks of flooding and erosion. Anticipated extreme precipitation is projected to increase ponding depths in bioretention facilities, resulting in untreated stormwater overflow and prolonged ponding times exceeding baseline conditions by up to 13 h at numerous Ontario locations.

Bioretention can be an efficient measure of stormwater treatment. The bioretention system has been globally adapted for controlling rainfall-runoff volume and removing pollutants. However, there is a lack of systematic analysis of some hydrological processes in the bioretention facility, such as the transportation of rainfall-runoff (event water) and soil water (pre-event water). This research uniquely applied stable isotope tracing to a bioretention system to investigate the transport of rainfall-runoff and the movement of soil water in a bioretention column. The stable isotope tracing method is helpful for determining the transport process of water and is expected to enhance our understanding of bioretention systems. The ratio of the event rainfall-runoff and the pre-event soil water in the bottom outflow of bioretention columns was calculated by the stable isotope bivariate mixing model based on the oxygen and hydrogen stable isotopic data from continuous testing in the discharge of bioretention column. The time-varying proportion of event water and pre-event water in the hydrographic curve reveals that the outflow process of soil water is divided into three stages. In the early stage, all the outflow was soil water, accounting for about 6–13% of the total outflow. In the middle stage, the proportion of soil water rapidly decreased from 100% to 20% within a few minutes. In the later stage, the soil water proportion decreased slowly from 20% to 0%. The outflow of soil water accounted for more than 36% of the total outflow and decreased with the extension of the drought period. Soil water is a critical part of the bottom outflow of bioretention columns, and the influence of soil water on the hydrological effect of bioretention columns cannot be ignored.

Low impact development (LID) is a sustainable land use and planning strategy that aims to minimize the environmental impacts of development. A community can enhance their water resources and create sustainable and resilient neighbourhoods. This approach has demonstrated success in managing stormwater and promoting water reuse globally, however, its suitability in developing countries like Indonesia remains uncertain and requires further investigation. The implementation of LID in developing countries may face several challenges including high density and complex drainage networks, combined sewer usage, clay soil type, irregular housing layouts, community socio-economic characteristics, affordability, cost, and the availability of regulations and policies. With proper planning and site-specific strategies, LID can be implemented effectively in Indonesia. Clear regulations, secured funding source and community-based LID are all essential for successful LID deployment. This paper can be used as a starting point for considering LID implementation in Indonesia and other countries with similar characteristics. HIGHLIGHTS The applicability of LID in developing countries like Indonesia remains uncertain and requires further investigation.; The implementation of LID in Indonesia faces several challenges including high-density and complex drainage networks, combined sewer usage, clayey soil type, irregular housing layouts, community socio-economic, affordability, and cost, coupled with the availability of regulations and policies.; With proper planning and site-specific strategies that address these challenges, LID can be implemented effectively in Indonesia.;

There has been a rapid development in studies of nature-based solutions (NbS) worldwide, which reveals the potential of this type of solution and the high level of interest in its implementation to improve the resilience of cities. Much relevant information and many important results are being published, and it is now possible to see their diverse benefits and complexity. Several authors highlight their role in urban areas not just in temperature control, but also in human health, ecosystem development and water management. However, in the current reality of cities, where water use is being (and will be) constantly challenged, analyzing NbS advantages for the urban water cycle is crucial. This study performed an intense review of the NbS literature from 2000 to 2021, to identify their contributions to the improvement of urban water cycle management and thus provide a solid information base for distinct entities (public institutions, private investors and the urban population in general) to disseminate, apply and justify their implementation. In general terms, the urban water cycle embraces not only the abstraction of water for urban consumption, but also its return to nature and all the stages in between, including water reuse and stormwater management. This review will highlight the important benefits that NbS in general, and green roofs in particular, provide to urban stormwater control, a key factor that contributes to urban sustainability and resilience in order to face future climate challenges. The novelty of the present review paper falls within the conclusions regarding the crucial role that NbS develop in urban water management and the main features that must be tested and technically enhanced to improve their functioning. [ABSTRACT FROM AUTHOR]

Bioswales are used to attenuate stormwater pollution, but their long-term sustainability regarding sequestered metals is relatively unknown, and a clear rationale for prioritizing soil management is lacking. Impervious areas draining into four 14-year-old suburban bioswales were delineated, for which surface soils (top 10 cm; 72 samples) were sampled; soils from 4 adjacent reference sites were also sampled. Total and water soluble metals (Cd, Cu, Pb, Zn) were quantified, and the relationships between metal concentrations and drainage area characteristics evaluated. Annual metal loads were estimated using regional runoff data to simulate current and future metal concentrations; risks to soil biota were assessed by comparing metal concentrations to ecological screening levels. The drainage areas' percent imperviousness (37-71%) and ratios of impervious drainage area to bioswale area (2.0-5.7) varied, owing to differing proportions of rooftops, paved surfaces, lawns, and natural soils. Total Cu and Zn ranged from 10.0 to 43.2 mg/kg dry soil, and 15.6 to 129.5 mg/kg dry soil, respectively. Across all bioswales, total Zn was positively correlated to percent impervious area (r = 0.32, p = 0.0073), the ratio of connected impervious drainage area to infiltration area (r = 0.32, p = 0.0073), and percent drainage area as paved surfaces (r = 0.46, p = 5.6 E-05), but negatively correlated to percent drainage area as lawns (r = -0.48; p = 2.4 E-05). Water soluble metal concentrations were orders of magnitude lower than total metals. Given annual metal loads (0.2-0.4 mg Cu/kg dry soil; 1.5-3.1 mg Zn/kg dry soil), replacing bioswale soils to constrain metal concentrations would be unnecessary for decades. Taken together, this study proposes a transferable approach of estimating, then verifying via sampling and analysis, bioswale soil metal concentrations, such that soil management decisions can be benchmarked to ecological screening levels.

Urban stormwater management has become a major issue over the last decades for flood prevention as well as water resource preservation. The development of green infrastructures such as bioretention systems since the 1990s has often been reported as an effective means of runoff mitigation with subsequent conveyed pollutant capture. Nevertheless, climate change involving more frequent extreme weather events as well as the variety of emerging pollutants in urban runoff have put an increasing strain on bioretention processes. Within this context, this mini-review deals with the opportunity of upgrading vegetated bioretention systems with active control technology to enhance their pollutant treatment capacity through proper control of critical bioretention operational variables and relying on improved ecological functioning and resilience. It is envisioned that such nature-based solutions hybridized with real-time control technology would help to improve stormwater reuse for more sustainable urban water management within the nexus of water–energy–food and greenhouse gases in future cities. HIGHLIGHTS Needs to enhance the capacity of soluble pollutant retention by current bioretention cells.; Real-time control of bioretention cells as a promising way to improve biofiltration performances.; Real-time control of soil moisture level to foster ecological functioning, bioremediation and ecosystem resilience of bioretention cells.; Healthier actively controlled bioretention ecosystems as a way to increase stormwater reuse.;

Bioretention cells, or rain gardens, can effectively reduce many contaminants in polluted stormwater through phytoremediation and bioremediation. The vegetated soil structure develops bacterial communities both within the soil and around the vegetation roots that play a significant role in the bioremediative process. Prediction of a bioretention cell's performance and efficacy is essential to the design process, operation, and maintenance throughout the design life of the cell. One of the key hurdles to these important issues and, therefore, to appropriate designs, is the lack of effective and inexpensive devices for monitoring and quantitatively assessing this bioremediative process in the field. This research reviews the available technologies for biomass monitoring and assesses their potential for quantifying bioremediative processes in rain gardens. The methods are discussed based on accuracy and calibration requirements, potential for use in situ, in real-time, and for characterizing biofilm formation in media that undergoes large fluctuations in nutrient supply. The methods discussed are microscopical, piezoelectric, fiber-optic, thermometric, and electrochemical. Microscopical methods are precluded from field use but would be essential to the calibration and verification of any field-based sensor. Piezoelectric, fiber-optic, thermometric, and some of the electrochemical-based methods reviewed come with limitations by way of support mechanisms or insufficient detection limits. The impedance-based electrochemical method shows the most promise for applications in rain gardens, and it is supported by microscopical methods for calibration and validation. [ABSTRACT FROM AUTHOR]

Climate change represents a paramount challenge for humanity in the 21st century. Green infrastructure (GI), due to its myriad environmental and societal benefits, has emerged as an essential natural life support system and a pivotal strategy to combat climate change-induced risks. Consequently, GI has garnered considerable global interest. As of now, comprehensive and systematic environmental impact assessments of GI are underway worldwide. Nonetheless, there remains a conspicuous scarcity of life-cycle approaches to delineate the evolutionary trajectory of this domain. Employing three bibliometric software tools—the R language "Bibliometrix" package (version 4.0.1), CiteSpace (version 6.2.R2 Basic), and "VOSviewer" (version 1.6.18)—this study scrutinizes the progression of the GI paradigm until 2022. An exhaustive review of 1124 documents published on the Web of Science between 1995 and 2022 facilitates an overarching evaluation of GI, encompassing environmental, economic, and social facets from a life-cycle standpoint. The analysis results reveal that (1) the majority of current studies accentuate the economic and environmental efficacy of GI throughout its life cycle, with the social performance receiving comparatively less focus, potentially due to the difficulties in formulating a social life-cycle-assessment database; (2) contemporary research predominantly concentrates on the life-cycle carbon footprint of GI, warranting further exploration into its water and carbon footprints; and (3) multi-objective optimization emerges as a promising avenue for future GI investigations. This review thus furnishes a comprehensive understanding of the performance of GI from a life-cycle perspective. [ABSTRACT FROM AUTHOR]

In recent years, as a result of intensive urbanisation, a significant increase in the surface of impermeable areas has been observed, which results in changes in the hydrological cycle of catchments. In order to counteract these changes, low-impact development (LID) solutions are increasingly being implemented in urban catchments, including bioretention systems. Taking this into account, a new bioretention drainage channel (BRC) was designed, whose main task is retention, infiltration, and pre-treatment of rainwater. The pilot laboratory tests carried out on two BRC prototypes (K1 and K2) showed that the average rate of reduction of mineral-suspended solids from rainwater was 69% and 57%, respectively, for K1 and K2. Analysing the results of the research, it was found that the bioretention drainage channel is characterised by very high efficiency in removing petroleum hydrocarbons from rainwater, and the reduction rate of these pollutants for both the K1 and K2 channels was close to 100%. In turn, hydrodynamic studies carried out on the model of the urban catchment showed that the implementation of BRCs will reduce the peak runoff by more than 82%, and the maximum flow in the sewage network by 83%. [ABSTRACT FROM AUTHOR]

We conducted a column study to better understand the relative effects of plants, design elements, and operating conditions on pollutant removal in stormwater biofilters in southern California under local conditions. We planted five southern California native species (Baccharis pilularis, Carex praegracilis, Juncus patens, Leymus condensatus, and Muhlenbergia rigens) in experimental biofilter columns fitted with a saturated zone and evaluated pollutant removal during weekly dosing and following a 52-day dry period. Columns planted with C. praegracilis and J. patens were also evaluated under conditions of fortnightly dosing and without the presence of a saturated zone. During weekly dosing, planted columns had a total nitrogen removal efficiency of 46% on average whereas removal was 8% in unplanted columns. B. pilularis and M. rigens performed better than other species at nitrogen removal. The presence of a saturated zone improved nitrogen removal and metal removal, but only before the 52-day dry period. With a few exceptions, local best management practice effluent concentrations limits were exceeded but performed similarly to existing southern California biofilters. Nitrogen removal decreased slightly under a fortnightly dosing frequency, which better represented rainfall event frequency in Los Angeles when compared to weekly dosing.

Bioretention is commonly used for runoff pollution control. The first flush strength of pollutants can affect bioretention performance. To examine the influence of the first flush strength on bioretention performance, bioretention columns filled with garden soil as the main media were established. Activated carbon and water treatment residuals (WTR) were added and compared for their ability to enhance phosphorus removal. Waste edible fungus culture medium (WEFCM) as a carbon source was also explored. When WEFCM was used as a carbon source instead of wood chips, total nitrogen (TN) removal increased from 60.83 ± 21.22 to 62.21 ± 16.43%, but chemical oxygen demand (COD) leaching was observed. WTR was better able than activated carbon to enhance phosphorus removal (87.97 ± 8.87 vs. 81.66 ± 9.27%) without impacting TN removal. NH4+-N removal increased with increasing first flush strength, but there was no trend for suspended solids (SS), COD, TN, or total phosphorus. First leaching phenomenon in bioretention outflow was proposed in this study. A low first leaching was observed in the outflow when the inflow had a uniform pollutant mass (i.e., no first flush) because of media leaching. A weak first leaching outflow was observed for SS and COD when they were present at strong first flush inflow. HIGHLIGHTS Waste edible fungus culture medium can be used as a carbon source instead of wood chips.; Water treatment residuals enhanced P removal better than activated carbon at the same volume ratio.; NH4+-N removal increased with increasing first flush strength, but SS, COD, TN, and TP did not.; A strong SS and COD first flush inflow led to considerable first leaching mitigation effect in the outflow.;

【Objective】 Bioretention is a method to purify water, and the aim of this paper is to study its effect on stormwater runoff. 【Method】 We took stormwater runoff in Shijiazhuang city as an example, investigating the outflow characteristics of the bioretention system in response to two rainfall patterns, constant pattern and Chicago pattern using column experiment and HYDRUS model. From the simulated results, we analyzed and discussed the sensitivities of the runoff to soil hydraulic parameters, catchment area and thickness of the planting soil layer. We also developed a model to predict the influence of rainfalls with different return periods (N) on outflow. 【Result】 Compared to constant rainfall, the Chicago rainfall pattern delayed the emergence of outlet-outflow and prolonged the ponding duration on the soil surface. The hydraulic parameters to which the runoff was sensitive include saturated soil permeability Ks, saturated soil water content θs, and the empirical parameter α in the van Genuchten formula. An increase in Ks increased the maximum outlet-drainage rate and brought forward its arrival time. Increasing θs prolonged the latent time and reduced the outflow rate and ponding duration. Increasing the parameter α resulted in an increase in outflow. Doubling the catchment area ratio increased the maximum drainage rate, the peak-reduction rate and ponding duration by 13%, 33% and 300%, respectively, whereas reducing the latent time by 16%. Change in thickness of the planting soil layer did not show a significant effect on the outflow pattern. 【Conclusion】 The bioretention system is more permeable with more than 90% of rainwater flowing through the planting soil layer. When the return period of the rainfall is no more than 5 years, there is no overflow with the peak reduction rate being 40.6%~76.5%, the latent time > 1 h and ponding time < 2 h.

Bioretention cells (BRCs) are a promising low-impact development (LID) practice that are commonly used in urban settings to improve the water quality and mitigate the hydrological effects of stormwater runoff. BRCs have been the subject of extensive research in order to better comprehend their function and improve their effectiveness. However, BRC performance differs greatly among regions in terms of hydrologic performance and quality enhancement. Due to this variance in BRC effectiveness, the current study conducted a comprehensive systematic review to answer the question, "Are BRCs an effective LID method for urban catchment stormwater management?". This review study analyzed the effectiveness of BRCs in mitigating hydrologic impacts and enhancing the quality of stormwater runoff in urban catchments. A review of 114 field, laboratory, and modeling studies on BRCs found that the promising BRCs may be one of the most successful approaches to restore urban hydrology cycle and improve stormwater water quality. With further development of BRCs, their performance in terms of quantity and quality will become more reliable, helping to develop long-term solutions to stormwater urban drainage issues. At the end of this review, the knowledge gaps and future prospects for BRC research are presented. In addition to providing a foundational grasp of BRC, this review study outlines the key design recommendations for BRC implementation in order to address the issues raised by certain BRC design errors. [ABSTRACT FROM AUTHOR]

BRCs (bioretention cells), one of many low-impact development (LID) practices, are increasingly utilized to lessen the amount of runoff while simultaneously improving the runoff quality. Because the goal of BRCs and LID designs, in general, is to mimic or replicate the pre-development hydrology, it is critical to evaluate the hydrologic and ecologic performances of the BRC facility from the perspective of replicating the pre-development hydrology. The metrics developed in this study were intended to represent the hydrologic regime including the runoff volume control metrics, peak flow frequency exceedance curve, and flow duration curve. We also used a hydrological indicator of T0.5, the fraction of a multi-year period in which the flow exceeds the 0.5-year return period storm to represent the performances regarding downstream ecology. The indicators were compared to their pre-development values to determine how closely they reflected and replicated the pre-development state. A long-term stormwater management model (SWMM) model was developed to examine conditions before and after development and water movement in BRCs. When the BRCs facilities areas are 5% of the entire impervious study area, key findings show that: (1) BRCs have significant runoff volume control performances. (2) The peak flow frequency exceedance curve with BRCs could fully match the pre-development scenario for minor rainfall events compared to the 0.1-year storm. Flow duration curves with BRCs showed that, the frequency, magnitude, and duration of small flows that occurred for more than 90% of the total time closely matched those of pre-development hydrology. (3) T0.5 with BRCs showed significant improvement compared with the value of the area with no BRCs and was close to the pre-development T0.5. The findings presented in this study indicated the significant performance of BRCs in improving downstream ecology. [ABSTRACT FROM AUTHOR]

Recently, biochar with persistent free radicals has widely been applied to the removal of nutrient in bioretention cells. However, there is a lack of information on hydrogen peroxide (H2O2) levels in biochar-based bioretention cells with three environmental conditions and its potential risks. In this study, batch experiments were used to investigate H2O2 levels in biochar-based bioretention cells with different weight ratios of sand to biochar (S/B), hydraulic loading rate (HLR) and antecedent dry period (ADP). Potential risks of H2O2 on dominant community were also explored. Results showed that H2O2 levels in bioretention cells with 9:1, 8:2 and 7:3 of S/B were significantly high with the range from 0.024 to 0.044 mmol/L, and the production decreased with the increasing contents of biochar. Furthermore, H2O2 levels in three different heights of substrate layers and the bottom outlet enhanced with the rise of HLR, where the amplification of H2O2 in the middle layer was the largest, reaching 438.5% (ratio of H2O2 level at 2.0 m3/m2/d of HLR to the one at 0.4 m3/m2/d of HLR). In contrast, the long ADP was unfavorable to H2O2 levels in biochar-based bioretention cells. The production of H2O2 resulted in the change of dominant microflora (Bacteroidetes and Firmicutes), and the dosage of biochar could be the key. Altering these mentioned factors to achieve the regulation of microbial community structure in bioretention cells with biochar could be one of the promising approaches for the improvement of biological degradation function. [ABSTRACT FROM AUTHOR]

Microbial transformation is a vital mechanism to internally treat nitrogen (N) within bioretention cells (BRCs); nitrifying and denitrifying microorganisms are the main drivers of permanent nitrogen removal. The limited research of the characteristics of nitrifying and denitrifying microbes in different layers during dry periods has prevented further understanding of nitrogen behavior in bioretention cells. In this paper, high-throughput sequencing technology and qPCR were used to analyze the microbial community and the abundance of six functional genes in soil and water samples of a layered BRC. This study found that the microbial community structure of the gravel layer was distinguished from that of the other three layers. With the extension in the dry period, the amount of microbial species shared by all four layers increased, showing a convergent succession of microorganisms. The nitrification and denitrification functional genes mainly existed in the upper layer of the bioretention cell; in addition, the abundance of the functional genes in the sand layer increased after rainfall and peaked at about 24–48 h, after which the abundance decreased and became steady. Correlation analysis indicated that the abundance of nitrification and denitrification functional genes was significantly affected by TOC, ammonia nitrogen concentration and nitrate nitrogen concentration. [ABSTRACT FROM AUTHOR]

Detailed data on the long-term performance of bioretention cells (BC) for stormwater management are sparse. This research aimed at setting up and testing an infrastructure that will provide the data on hydrologic and chemical performance of BC. Two identical experimental BC’s were built. The monitoring methodology monitoring was developed and tested during a first growing season with the first BC supplied with natural rainfall, while the second BC was used for ponding experiments. Key layer of the BCs, a biofilter, was composed of sand, compost and topsoil. Both BCs are equipped with sensors monitoring the components of water balance and the water potential of the biofilter. High levels of total suspended solids were detected in the outflow. The runoff coefficient for the entire period of the growing season was 0.72 in the first BC and 0.86 in the second BC, while the peak outflow reduction for individual rainfall episodes ranged between 75% to 95% for the first BC and 19% to 30% for the second BC. Saturated hydraulic conductivity of the biofilter in the first BC decreased by two orders of magnitudes after the first year of operation. Retention curves of the biofilter changed due to material consolidation.

Biochar has been proved as a promising and efficient filler in bioretention facilities for enhancing the stormwater pollutants removal. However, the migration behaviors of stormwater pollutants in biochar filled bioretention facilities is unclear. In this study, as one of the most typical stormwater pollutants, naphthalene was selected as an example and a HYDRUS-1D model was first used to understand the migration behavior of naphthalene in a bioretention facility. In comparison with the conventional bioretention soil media (sandy loam), the amended biochar filled bioretention cell showed that the naphthalene removal rate was enhanced by up to 10.1%. Meanwhile, the experimental data was well-fitted by the "two-site sorption model" in HYDRUS-1D model. Another, the effect of rainfall intensity on the naphthalene migration in both bioretention columns was further investigated. The HYDRUS-1D model fitting indicated that the increase in rainfall intensity promoted naphthalene migration by increasing hydraulic conductivity and water flux. In addition, static batch experiments revealed that the biochar filled fillers achieved about 50% higher adsorption capacity than sandy loam. The sensitivity analysis from the HYDRUS-1D model data verified adsorption coefficient K d and longitudinal dispersivity λ are the main factors affecting naphthalene migration. Finally, the model simulation displays that the proportion of naphthalene retained by the fillers was highest during high rainfall intensities, indicating that the fillers remain the most important fate for naphthalene. This study presents research on the behavior and mechanisms of stormwater pollutant transport through improved bioretention facilities. [Display omitted] • The HYDRUS-1D model was first employed to understand the migration behavior of naphthalene in biochar filled bioretention facilities. • The amended biochar filled bioretention enhanced naphthalene adsorption by up to 10.1% via "two-site adsorption model". • The migration of naphthalene within the amended biochar medium is primarily influenced by the adsorption and dispersion factors. • Naphthalene migration in a biochar filled bioretention is slower than sandy loam bioretention column. [ABSTRACT FROM AUTHOR]

Bioretention basins are extensively used in urban areas to manage stormwater by reducing peak flows and pollution. This study evaluated the performance of a bioretention basin in removing heavy metals, polycyclic aromatic hydrocarbons (PAHs), and oil and grease. Using droplet digital PCR (ddPCR), the presence of metal resistance genes (MRGs) and antibiotic resistance genes (ARGs) in the basin's soil was analyzed. The results indicated effective removal of Zn (67%), but higher concentration of Mg was observed at the outlet. Cu, Fe and Pb showed no significant differences in the in- and outflow concentrations. The system successfully removed 82% of influent PAHs. Soil samples collected in summer and fall revealed higher MRG abundance in summer, with copA being the most prevalent MRG (1.2–4.8 log 10 copies/g soil). Among the ARGs, sul1 was consistently found throughout the basin (2.5–6.7 log 10 copies/g soil), while tetW was detected primarily at the basin's start and end in the topsoil layer. Rubellimicrobium and Geobacter were identified as potential carriers of ARGs/MRGs. Although the concentration of metals in soil was not measured in the current study, these findings emphasize the need to understand heavy metal distribution and the occurrence of MRGs and ARGs in stormwater control systems to improve their design and effectiveness. [Display omitted] • Stormwater bioretention basin monitored for removal of heavy metals, PAHs and oil & grease. • Soil samples were analyzed for metal resistance genes and antibiotic resistance genes. • Removal of Cu and Zn from the basin, while Pb and Mg were higher in the outlet. • MRGs was more abundant in summer, copA was detected throughout the basin. • Sul1 was detected throughout the basin, tetW was detected only in top layer of soil. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of mycorrhizal inoculation on six common Australian biofilter plant species using a pot experiment. We divided 120 pots planted with six common biofilter species into four treatments: control water-deficit, inoculated water-deficit, control well-watered, and inoculated well-watered. Inoculated treatments were inoculated with a commercially available blend of arbuscular mycorrhizal fungi spores. While well-watered pots were watered to pot capacity daily, water-deficit pots were subjected to a simulated drought that lasted six weeks until harvesting. All plants inoculated with arbuscular mycorrhizal fungi developed greater total root surface area, plant biomass, and plant relative growth rate. Which are associated with better stormwater nutrient removal. Mycorrhizal inoculation also increased the average root diameter, total length, and surface area of thick roots (diameter > 1 mm) of six species, which are essential to maintain the infiltration rates and hydraulic functions of biofilter systems. Moreover, an increase in shoot biomass following inoculation was also observed across six species, potentially contributing to higher water loss and stormwater volume reduction. Although the water-deficit condition greatly limited the effects of mycorrhizal inoculation on other morphological traits, we still observed the benefits of inoculation on total root length and surface area in well-watered J. pallidus and C. appressa. As drought stress imposes limitations on the effects of inoculation, we recommend inoculation should be carried out in advantageous times, such as during wet periods before the drought season for the optimal colonization and plant biomass and morphological responses. Additionally, selecting mycorrhizae-responsive species like C. appressa, J. pallidus, and G. sieberiana can result in favorable outcomes. [ABSTRACT FROM AUTHOR]

Green infrastructure (GI) systems have been employed as an environmentally sustainable alternative to treat stormwater in urban areas, and many previous studies indicated GI practices are effective at reducing stormwater runoff flows to watersheds by rerouting flows through vegetation and soil. However, little is known about the effects of maintenance on GI performance. This study evaluated the maintenance efficiency for four GI designs (bioretention, grass channel, compost-amended grass channel, and bioswale) receiving the same weather conditions and pollutants along Lorton Road, Fairfax County, VA, USA., based on water-quality performance and economic costs. Seven regular maintenance events and a forebay restoration were monitored from 2018 to 2022. Stormwater quality performance among these four GI practices before and after these in-field maintenance activities was assessed on the load reduction of dissolved organic carbon (DOC), total dissolved nitrogen (TDN), total suspended solids (TSS), and runoff over four years. The average runoff reductions over all monitored storms were 74%, 85%,63%, and 68% for bioretention, grass channel, compost-amended grass channel, and bioswale, respectively. Over these maintenance events, the mean runoff reduction of all monitored GI designs improved by 3% after maintenance, DOC mass load reduction increased by 41%, TDN mass load reduction improved by 21%, and TSS mass load reduction increased by 2%. All the pollutant and runoff reductions for swales improved after spring maintenance events, and monitored GI systems generally performed better after spring maintenance events, potentially due more to the vegetation growth than the maintenance work. Bioretention and compost-amended grass channel DOC load reductions were the only statistically significant GI performance improvements attributable to maintenance. [Display omitted] • Stormwater quantity and quality performance were monitored for four types of green infrastructure. • Cost efficiency of green infrastructure maintenance was evaluated over four years. • BR and CAGC displayed statistically significant increases in DOC load reduction after maintenance. • Runoff treated by BR basin increased after forebay restoration. • This study will help improve the design and maintenance of future green infrastructure systems. [ABSTRACT FROM AUTHOR]

Urban surface temperatures are high in summertime, and thermal pollution caused by heat transfer from pavement to stormwater runoff is harmful to aquatic ecosystems. However, there is a lack of studies investigating the temperature change pattern during rainstorms and evaluating the effects of bioretention on dynamic characteristics of thermal pollution. Therefore, this study selected a 1.05 ha parking lot retrofitted with five individual bioretention cells in Beijing as the object to compare the temperature and volume of stormwater runoff before and after bioretention treatment. In the LID parking lot, the average EMT and EMXT (event maximum temperature) of runoff decreased by 2.28 °C and 4.18 °C, respectively, and the median percent thermal load reduction was 90.6%. Data analysis from 15 summer rainfall events showed that the sequence of factors affecting runoff EMT (event mean temperature) was average air temperature, max air temperature, max solar radiation, and rainfall peak 5-min intensity. Bioretention profoundly changed the thermal dynamic characteristics of stormwater runoff. Surface runoff temperatures generally showed a decreasing trend over time. The temperature change pattern of LID parking lot outflow was synchronized with that of the inflow and varied with different grades of precipitation. The probability of the peak temperature ahead of peak flow decreased from 80% to 53%, suggesting that 27% of the thermal first-flush effect of thermal pollution from the urban surface was alleviated by site-scale bioretention implementation. The site-scale bioretention combination had a lower effluent temperature and a higher thermal load reduction rate than single-scale solutions. These results fill the gap in research on the thermal pollution reduction process of bioretention. Furthermore, they can guide the optimization of bioretention design methods and strategies to protect urban water bodies from the stormwater runoff thermal pollution. [Display omitted] • The average air temperature is the most effective characteristic in predicting EMT. • Bioretention retrofits reduced the probability of thermal first-flush by 27%. • Intra-event temperature dynamics varied based on rainfall duration and grade. • Distributed bioretention installations can limit thermal pollution from stormwater. [ABSTRACT FROM AUTHOR]

Rain gardens, a type of green infrastructure (GI), have been recognized for mitigating flooding and improving water quality from minor storms by trapping stormwater pollutants. Yet, the capability of these systems to retain microplastics (MPs) from stormwater, especially in size <125 μ m , remains inadequately understood. This study investigated the spatial and temporal distributions of MPs in three rain gardens located in Newark, New Jersey, USA. The rain gardens have been in operation for ∼7 years and located in different land uses: low-density residential (Site 1), commercial (Site 2), and high-density residential (Site 3). The sediment samples were collected during May 2022, August 2022, and February 2023 at various soil depths and horizontal distances of rain gardens. The MPs were quantified and characterized using Fourier transform infrared (FTIR) spectrometer and a Raman microscope. The overall mean concentration varied between sampling sites, with 469 ± 89.8 pkg − 1 in Site 1, 604 ± 91.4 pkg − 1 in Site 2, and 997 ± 64.3 pkg − 1 in Site 3, with Polypropylene as the dominant polymer, followed by nylon and polyethylene. In the vertical direction, larger MPs (250 μ m –5 mm) were effectively retained within the top 5 cm and their concentration declined exponentially with the increasing depths. Small-sized MPs (1–250 μ m) were prevalent at deeper depths (≥ 10 cm), and no MPs were found below 15 cm. In the horizontal direction, the highest MP concentration was observed near the stormwater inlet, and the concentration decreased away from the inlet. Over the nine-month period, a notable increase in concentration was observed at all sites. These findings contribute valuable knowledge towards developing effective measures for retaining MPs from stormwater and monitoring GIs in urban environments. [Display omitted] • The MP accumulation decreases with depth in the bioretention media. • The larger-sized MPs (250 μ m –5 mm) are primarily retained in the top 5 cm. • The MPs in rain gardens reached down to 15 cm. • In the horizontal direction, MPs are highest near the inlet of rain gardens. [ABSTRACT FROM AUTHOR]

There has been a rapid development in studies of nature-based solutions (NbS) worldwide, which reveals the potential of this type of solution and the high level of interest in its implementation to improve the resilience of cities. Much relevant information and many important results are being published, and it is now possible to see their diverse benefits and complexity. Several authors highlight their role in urban areas not just in temperature control, but also in human health, ecosystem development and water management. However, in the current reality of cities, where water use is being (and will be) constantly challenged, analyzing NbS advantages for the urban water cycle is crucial. This study performed an intense review of the NbS literature from 2000 to 2021, to identify their contributions to the improvement of urban water cycle management and thus provide a solid information base for distinct entities (public institutions, private investors and the urban population in general) to disseminate, apply and justify their implementation. In general terms, the urban water cycle embraces not only the abstraction of water for urban consumption, but also its return to nature and all the stages in between, including water reuse and stormwater management. This review will highlight the important benefits that NbS in general, and green roofs in particular, provide to urban stormwater control, a key factor that contributes to urban sustainability and resilience in order to face future climate challenges. The novelty of the present review paper falls within the conclusions regarding the crucial role that NbS develop in urban water management and the main features that must be tested and technically enhanced to improve their functioning.

Bioretention systems, which mimic natural hydrology and reduce volume of stormwater runoff, are a preferred solution for meeting water balance objectives, but lack of knowledge about the long-term performance of these systems hinders their wider adoption. This study was a field survey of mature (>3 years and up to 10 years post-construction) bioretention cells across Ontario, Canada. The survey involved visual inspections, determination of soil physical parameters and soil-water interaction parameters, infiltration capacity testing and synthetic drawdown testing. Results indicate that infiltration capacity remains above the recommended minimum of 25 mm/hr, likely due to high content soils and development of soil structure due to biological factors over time. The drawdown times for three sites ranged from 5 minutes to 6 hours, much less than the maximum allowed drawdown time of 24–48 hours. Ksat (saturated hydraulic conductivity) was only moderately negatively correlated with age, and where data existed on KSat at the beginning of operation, KSat improved for six out of nine sites. Soil-water interaction properties more closely resembled loam soils than sandy soils, which may be due to the development of a soil structure over time. We recommend conducting visual inspections regularly over infiltration capacity testing for quick determination of maintenance needs. HIGHLIGHTS Hydrology of bioretention continues to perform well over long-term (up to 10 years).; Media infiltration rates remain high and increased for 6/9 sites.; Drawdown times much faster than design.; Soil structure developed over time likely contributes to more water holding capacity available for plant uptake.;

Typical continental, cold climate conditions were applied to four large, laboratory columns to simulate temperatures ranging from −20 to +20 °C over summer, winter, and spring runoff. The goal of this research was to assess the seasonal effectiveness of bioretention application in cold climate regions that are currently experiencing the impacts of climate change. 1.6 years’ worth of equivalent Edmonton precipitation volume was applied over a 10-month period to evaluate the water quality improvement through two soil types (i.e., loam and sandy loam) with and without amendments intended to enhance nutrient removal. During summer, excellent removal of total suspended solids (TSS), phosphate, and ammonium (i.e., ≥90% average concentration reduction) was observed in both the loam and sandy loam columns without the nutrient removal amendments. The columns containing the amendments also reduced TSS, ammonium, and phosphate, but not as effective as the non-amended columns for TSS and ammonium. During winter and spring runoff, if infiltration occurs, physical removal of TSS, phosphate, and ammonium was still achieved, only days after the complete freezing (and subsequent thawing) of bioretention media at −20 °C. After an initial maturation and leaching period, nitrate was well removed (≥65.2% average concentration reduction) via denitrification in the columns with the nutrient removal amendments and submerged zone. HIGHLIGHTS Four large bioretention columns with two soil media (loam and sandy loam) underwent simulated summer, winter, spring runoff, and another summer of stormwater applications.; All columns effectively reduced TSS, ammonium, and phosphate concentrations in the effluent during the summer.; If infiltration occurs during winter and spring runoff, physical removal of TSS, phosphate, and ammonium can still be achieved.;

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The nitrogen removal performance of bioretention urgently needs to be improved, and sponge iron has great potential to address this challenge. This study reported the results of a long-term investigation on bioretention columns improved by sponge iron, examining the durability of sponge iron from nitrogen removal performance, sponge iron properties, and the evolution of biological elements. The results showed that after 9 months of continuous operation, the removal rates of ammonia nitrogen (NH 4 + -N), and total nitrogen (TN) in the bioretention columns with an appropriate proportion of sponge iron could reach 80% (some even over 90%). However, the long-term stress of sponge iron exposure, combined with the cumulative effect of pollutants, might lead to the excessive accumulation of reactive oxygen species (ROS) in plants, thereby posing risks of diminished chlorophyll content and enzyme activity. Simultaneously, the extended exposure could also have detrimental effects on microbial diversity and the abundance of dominant bacteria such as 3 - -N), and total nitrogen (TN) in the bioretention columns with an appropriate proportion of sponge iron could reach 80% (some even over 90%). However, the long-term stress of sponge iron exposure, combined with the cumulative effect of pollutants, might lead to the excessive accumulation of reactive oxygen species (ROS) in plants, thereby posing risks of diminished chlorophyll content and enzyme activity. Simultaneously, the extended exposure could also have detrimental effects on microbial diversity and the abundance of dominant bacteria such as Proteobacteria and Sphingorhabdus . Therefore, it is necessary to select plant species and functional genes that demonstrate high adaptability to iron-induced stress.

Global climate change and rapid urbanization have resulted in more frequent and intense rainfall events in urban areas, raising concerns about the effectiveness of stormwater bioretention systems. In this study, we optimized the design by constructing a multi-layer filler structure, including plant layer, biochar layer, and pyrite layer, and evaluated its performance in nitrogen (N) and phosphorus (P) removal under different temperatures (5-18 °C and 24-43 °C), rainfall intensity (47.06 mm rainfall depth), and frequency (1-5 days rainfall intervals) conditions. The findings indicate that over 775 days, the plant system consistently removed 62.3% of total nitrogen (TN) and 97.0% of total phosphorus (TP) from 103 intense rainfall events. Temperature fluctuations had minimal impact on nitrate nitrogen (NO 3 - -N) and TP removal, with differences in removal rates of only 1.0% and 0.6%, respectively, among plant groups. Across the multi-layer structure, plant roots mitigated the impact of temperature differences on NO 3 - -N removal, while high-frequency rainfall fluctuated the stability of NO 3 removal. In summary, the synergistic effects of the multi-layer filler structure improved and stabilized N and P removal, providing valuable insights for addressing runoff pollution in bioretention systems amidst rapid urbanization and climate change challenges.- -N removal. Dense plant roots reinforced N and P removal by facilitating denitrification in the vadose zone (biochar) and strengthening denitrification processes. Biochar and pyrite contributed to stable microenvironments and diverse ecological functions, enhancing NO 3 - -N and PO 4 3- removal. In summary, the synergistic effects of the multi-layer filler structure improved and stabilized N and P removal, providing valuable insights for addressing runoff pollution in bioretention systems amidst rapid urbanization and climate change challenges., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

The traditional bioretention systems possess a remarkably low nitrogen and phosphorus removal effect. The removal rate fluctuates greatly, and even appears as negative removal of nitrogen and phosphorus. Four simulated bioretention experimental columns with different bilayer media, packing composition and structure were constructed. Based on the traditional fillers, the modified composite fillers with hydroxy-aluminum and modified vermiculite sludge particle (HAVSP) were added. The traditional filler (C1) and the modified composite filler (C2) were added respectively, moreover saturated zones were set up to enhance the effect of nitrogen and phosphorus removal. Removal of nutrients from experimental columns by simulated runoff efficiency was evaluated and compared. In addition, the effect of media depth on phosphorus retention and denitrifying enzyme activity in bioretention columns was also evaluated. The experimental column #2 filled with C2 had the optimum removal effect on TP (93.70%), however, the removal effect of TP by filling C1 experimental columns was insufficient (57.36%). Designed to remove nitrate (NO3−-N) and total nitrogen, the experimental column #4 showed the best performance (83.54% and 92.15%, respectively). In this study, we propose a fold-flow bioretention system by filling HAVSP in combination with saturated zones. The runoff water quality can be effectively improved, and a new bioretention cell configuration can be provided for efficient stormwater treatment. HIGHLIGHTS Proposing a novel bioretention system by installing a fold-flow board and combining with saturated zones.; Filling hydroxy-aluminum vermiculite sludge particle and setting a bilayer filler inside the structure of the bioretention system.; Evaluating the effect of media depth on phosphorus retention and denitrifying enzyme activity in bioretention columns.;

In recent years, as a result of intensive urbanisation, a significant increase in the surface of impermeable areas has been observed, which results in changes in the hydrological cycle of catchments. In order to counteract these changes, low-impact development (LID) solutions are increasingly being implemented in urban catchments, including bioretention systems. Taking this into account, a new bioretention drainage channel (BRC) was designed, whose main task is retention, infiltration, and pre-treatment of rainwater. The pilot laboratory tests carried out on two BRC prototypes (K1 and K2) showed that the average rate of reduction of mineral-suspended solids from rainwater was 69% and 57%, respectively, for K1 and K2. Analysing the results of the research, it was found that the bioretention drainage channel is characterised by very high efficiency in removing petroleum hydrocarbons from rainwater, and the reduction rate of these pollutants for both the K1 and K2 channels was close to 100%. In turn, hydrodynamic studies carried out on the model of the urban catchment showed that the implementation of BRCs will reduce the peak runoff by more than 82%, and the maximum flow in the sewage network by 83%.

Bioretention cells, or rain gardens, can effectively reduce many contaminants in polluted stormwater through phytoremediation and bioremediation. The vegetated soil structure develops bacterial communities both within the soil and around the vegetation roots that play a significant role in the bioremediative process. Prediction of a bioretention cell’s performance and efficacy is essential to the design process, operation, and maintenance throughout the design life of the cell. One of the key hurdles to these important issues and, therefore, to appropriate designs, is the lack of effective and inexpensive devices for monitoring and quantitatively assessing this bioremediative process in the field. This research reviews the available technologies for biomass monitoring and assesses their potential for quantifying bioremediative processes in rain gardens. The methods are discussed based on accuracy and calibration requirements, potential for use in situ, in real-time, and for characterizing biofilm formation in media that undergoes large fluctuations in nutrient supply. The methods discussed are microscopical, piezoelectric, fiber-optic, thermometric, and electrochemical. Microscopical methods are precluded from field use but would be essential to the calibration and verification of any field-based sensor. Piezoelectric, fiber-optic, thermometric, and some of the electrochemical-based methods reviewed come with limitations by way of support mechanisms or insufficient detection limits. The impedance-based electrochemical method shows the most promise for applications in rain gardens, and it is supported by microscopical methods for calibration and validation.

Urban stormwater has become a persistent concern on a global scale due to its adverse environmental implications. It is the prime vector of aquatic contaminants worldwide that causes pollutants when water bodies drain. Bioretention systems are increasingly used to alleviate setbacks associated with stormwater run-off in urban locales. It has played a substantial role in the implementation of low impact development (LID), a concept that addresses urban stormwater problems caused by land changes and development. The use of LID technologies is an innovative approach. However, it is beset with challenges, such as the insufficiency of data on rainfall distribution and difficulty in interpreting data. To address these research gaps, the present study developed a fuzzy rough set data algorithm for bioretention systems. Event mean concentration calculations and fuzzification of rainfall were performed to produce a rough set-based decision rule. Using the Weibull probability distribution, fuzzification of rainfall and parameter data, rule induction, and Preece testing, bioretention design considerations were determined. The bioretention characterizations generated evident pollutants present in the catch basin before and after filtration. In addition, the bioretention characterization conducted in this study was able to reduce the number of tests needed for rainfall identification based on the different attributes. [ABSTRACT FROM AUTHOR]

The increase in urbanization and climate change projections point to a worsening of floods and urban river contamination. Cities need to adopt adaptive urban drainage measures capable of mitigating these drivers of change. This study presents a practical methodology for a modular design of bioretention systems incorporating land use and climate change into existing sizing methods. Additionally, a sensitivity analysis for these methods was performed. The methodology was applied to a case study in the city of Sao Carlos, SP, Brazil. Three application scales were evaluated: property scale (PS), street scale (SS) and neighborhood scale (NS) for three temporal scenarios: current, 2015–2050 and 2050–2100. The choice of the sizing method was the factor with greatest influence on the final bioretention performance, as it considerably affected the surface areas designed, followed by the hydraulic conductivity of the filtering media. When analyzing the sensitivity of the parameters for each method, the runoff coefficient and the daily precipitation with 90% probability were identified as the most sensitive parameters. For the period 2050–2100, there was an increase of up to 2×, 2.5× and 4× in inflow for PS, SS and NS, respectively. However and despite the great uncertainty of future drivers, bioretention performance would remain almost constant in future periods due to modular design. [ABSTRACT FROM AUTHOR]

The performance of the bioretention system is significantly affected by the soil media characteristics. In order to standardize the gradation of packing soil media and then improve the construction level of bioretention facilities in Chongqing urban area, two types of traditional bioretention soil media (BSM1 and BSM2) are mixed with loamy sand and fine sand in a mass ratio of 1:9, and sandy soil and fine sand in a mass ratio of 2 : 8, respectively, combining the results of the soil background survey in Chongqing. And on this basis, vermiculite (Ver.), biochar (BC) and perlite (Per.) are added as modifiers into BSM1 and BSM2 in different mass ratios, which finally configurates 6 types of modified soil media. Furthermore, the hydraulic permeability and pollutants removal performance of bioretention system with different soil media are investigated. Results show that different soil media shows different initial hydraulic permeability coefficient and attenuation performance, among which, the hydraulic permeability of BSM2+8%Ver. soil medium changes in a stable range of 41~53 mm/h, while the permeability of BSM2+8%BC soil medium has the highest attenuated rate. All soil media show an effective removal performance in runoff pollutants, especially in suspended solids (SS), and the effluent turbidity can reach 10~16 NTU. The removal capacity of the bioretention columns packed with BSM1 and its modified groups in organic pollutants and nutrients are superior to the other columns. Finally, this paper considers the factors of soil medium decontamination capacity, hydraulic permeability and price, the comprehensive ranking of modified soil media using the projection pursuit method: BSM1+2%Ver. (0.60) >BSM1 (0.52) >BSM1+2%BC (0.41) >BSM1+2%Per. (0.40) >BSM2+ 8%Ver. (0.33)>BSM2+8%BC(0.23)>BSM2 (0.15)>BSM2+8%Per. (0.14). [ABSTRACT FROM AUTHOR]

Submerged zone in bioretention facilities for stormwater treatment has been approved to be an effective structure amendment to improve denitrification capability. However, the role and influence of water quality changes in the submerged zone under natural continuous random rainfall patterns are still not clear, especially when the rainfall is less than the pore water in the submerged zone. In this study, continuous rainfall events with different rainfall volume (light rain-light rain-heavy rain) were designed in a lab-scale woodchip mulched pyrite bioretention facility to test the effects of rainfall pattern. The results exhibited that light rain events significantly affected the pollutant removal performance of bioretention for the next rainfall. Different effects were observed during the long-term operation. In the 5th month, light rain reduced the ammonia removal efficiency of subsequent rainstorm events by 8.70%, while in the 12th month, when nitrate leakage occurred, light rain led to a 40.24% reduction in the next heavy rain event's nitrate removal efficiency. Additionally, light rain would also affect the concentration of by-products in the next rainfall. Following a light rain, the concentration of sulfate in the subsequent light rainfall can increase by 24.4 mg/L, and by 11.92 mg/L in a heavy rain. The water quality in the submerged zone and media characteristics analysis suggested that nitrogen conversion capacity of the substrate and microbes, such as Nitrospira (2.86%) and Thiobacillus (35.71%), as well as the in-situ accumulation of pollutants under light rain played important roles. This study clarifies the relationship between successive rainfall events and provides a more comprehensive understanding of bioretention facilities. This is beneficial for field study of bioretention facilities in the face of complex rainfall events. [Display omitted] • A novel rainfall pattern was proposed to evaluate the efficiency of bioretention. • Light rain significantly impacts the performance of the next heavy rainfall. • Light rain leads to nitrate and sulfate accumulation in the submerged zone. • Microorganism is the main factor of ammonia accumulation in submerged zone. • 5. Thiobacillus and Pseudomonas are the dominant bacteria in the submerged zone. [ABSTRACT FROM AUTHOR]

Urbanization coupled with climate change results in significant stormwater management challenges. In this context, the use of green infrastructures such as bioswales and bioretention systems to intercept, slow down and filter runoff has been increasing in North America in recent years. However, little data is available on the selection of optimal plant species adapted to cold climates, their optimal positioning in the swale and intra and inter-seasonal variation in plant growth. A field experiment was conducted during three growing seasons from July 2020 to August 2022 in a proximal suburb of Québec City, Canada, to monitor the survival rate. Growth (height and plant area), and floridity (number of flower buds and flower stems) of 22 plant species in 48 cold climate bioretention cells located along streets. The study aimed to understand the influence of planting position (margin: upper position, usually dryer; slope; middle position, fluctuating water conditions; bottom: lower position, usually moister) on species development, in order to identify the species most and least adapted to the different moisture conditions. Results showed that survival was generally high (> 86%) and was not affected by position within the bioretention cells. However, for most species, plant area increased, and height decreased at the margin compared to the slope position, while floridity only increased at the margin for four species (Heliopsis helianthoides (L.) Sweet, Coreopsis verticillata L., Hemerocallis ' Stella Supreme" L., Verbena hastata L.). Seven species (Campanula carpatica Jacq "Alba", Hesperis matronalis L., Osmundastrum cinnamomeum (L.) C. Presl, Rudbeckia hirta L., Verbena hastata L. , Cerastium tomentosum L., Athyrium filix-femina (L.) Roth ex Mertens) exhibited lower survival and growth rates over time than the others. Overall, 15 out of 22 species performed well in the bioretention cells with minimum maintenance over the course of the experiment. Results also showed that plant area at the end of the growing season was much more influenced by position in the bioretention cells than were height or floridity, while survival was not influenced by this factor. A better knowledge of plant interactions in varying spatial distribution over time can contribute to improving and potentially maximizing bioretention performance. • 22 plant species were studied to see how planting position affects plant development over three years under a cold climate. • 15 species had high survival rates (>86%) regardless of position. • Plant area increased and height decreased at the margin compared to the slope position for most species. • Understanding plant growth can improve future planting arrangements and bioretention performance. [ABSTRACT FROM AUTHOR]