# Mdpj _sciences_
## 8 Conclusions  
This review aimed to evaluate the effectiveness of various green systems, including green walls, active green walls, and urban greenery systems, in mitigating environmental pollutants such as particulate matter (PM), VOCs, and gases like CO2 and NO2. The key findings from the reviewed studies indicate that green systems can significantly reduce pollutant concentrations in both indoor and outdoor environments. Active green walls, in particular, showed enhanced efficiency due to the incorporation of airflow through vegetation, with species such as _Chlorophytum comosum_ and _Sangeveria trifasciata_ demonstrating high pollutant absorption capacities.  
The key findings are as follows:  
* Green systems effectively reduce various pollutants. Active green walls achieved higher removal efficiencies compared to passive systems, with VOC reductions of up to 96.34%, PM reductions of 65.42%, and CO2 reduction rates reaching 4.8% under optimal conditions.
* Specific plant species, like _Chlorophytum comosum_ and _Sangeveria trifasciata_, exhibited high capacities for pollutant absorption, making them ideal for green systems.
* Proper maintenance is crucial for sustaining the performance of green systems. This includes regular checks of irrigation systems, substrates, and plant health to prevent declines in efficiency.
* The potential for pollutant resuspension is a significant gap in current research. Addressing this issue is essential for designing more effective and reliable green systems.  
The findings highlight the potential of green systems to improve air quality in urban environments, contributing to public health and environmental sustainability. Urban planners and policy-makers can leverage these insights to develop regulations and incentives for adopting green systems. For instance, mandating green wall installations in new buildings and incorporating specific plant species into urban landscapes could enhance urban air quality.  
To advance the field, researchers, policy-makers, and practitioners should focus on the following:  
* Conducting long-term studies to assess the durability and effectiveness of green systems under varying seasonal conditions and prolonged pollutant exposure.
* Including economic analyses to evaluate the cost-benefit ratio of large-scale green system implementations.  
* Enhancing the reliability and applicability of simulation models through real-world validation against field data.
* Developing maintenance programs that ensure the long-term efficiency of green systems, addressing potential issues like pollutant resuspension.  
By addressing these areas, future research can build on the current understanding and develop more effective and sustainable green systems for environmental pollutant mitigation. This will not only enhance air quality but also contribute to healthier urban living environments.  
Conceptualization, S.C. and P.R.D.; methodology, S.C.; formal analysis, S.V.; investigation, S.C. and S.V.; writing--original draft preparation, S.V.; writing--review and editing, S.C.; visualization, S.C.; supervision, P.R.D. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
No new data were created or analyzed in this study.  
The publication was created within the framework of the European Union--FSE-REACT-EU, PON Research and Innovation 2014-2020 DM1062/2021.  
The authors declare no conflicts of interest.