Applied horticultural biotechnology for the mitigation of indoor air pollution

Exposure to indoor air pollution is an emerging world-wide problem, with growing evidence that it is a major cause of morbidity worldwide. Whilst most indoor air pollutants are of outdoor origin, these combine with a range of indoor sourced pollutants that may lead to high pollutant levels indoors. The pollutants of greatest concern are volatile organic compounds (VOCs) and particulate matter (PM), both of which are associated with a range of serious health problems. Whilst current buildings usually use ventilation with outdoor air to remove these pollutants, botanical systems are gaining recognition as an effective alternative. Whilst many years research has shown that traditional potted plants and their substrates are capable of removing VOCs effectively, they are inefficient at removing PM, and are limited in their pollutant removal rates by the need for pollutants to diffuse to the active pollutant removal components of these systems. Active botanical biofiltration, using green wall systems combined with mechanical fans to increase pollutant exposure to the plants and substrate, show greatly increased rates of pollutant removal for both VOCs, PM and also carbon dioxide (CO2). A developing body of research indicates that these systems can outperform existing technologies for indoor air pollutant removal, although further research is required before their use will become widespread. Whilst it is known that plant species selection and substrate characteristics can affect the performance of active botanical systems, optimal characteristics are yet to be identified. Once this research has been completed, it is proposed that active botanical biofiltration will provide a cheap and low energy use alternative to mechanical ventilations systems for the maintenance of indoor environmental quality

Do the plants in functional green walls contribute to their ability to filter particulate matter?

© 2017 Elsevier Ltd Indoor air quality has become a growing concern as people are spending more time indoors, combined with the construction of highly sealed buildings that promote thermal efficiency. Particulate matter (PM) is a common indoor air pollutant, with exposure to high concentrations associated with several detrimental health outcomes. Active botanical biofilters or functional green walls are becoming increasingly efficient and have the potential to mitigate high suspended PM concentrations. These systems, however, require further development before they become competitive with industry standard in-room air filters. Whilst the plant growth substrate in active biofilters can act as a filter medium, it was previously not known whether the plant component of these systems played a function in PM filtration. This study thus examines the influence of the botanical component on active green wall PM single pass removal efficiency (SPRE), with a focus on evaluating the air filtration features of different plant species in green wall modules. All tested botanical biofilters outperformed biofilters that consisted only of substrate. Green walls using different plant species had different single pass removal efficiencies, with fern species recording the highest removal efficiencies across all measured particle sizes (Nephrolepis exaltata bostoniensis SPRE for PM0.3-0.5 and PM5-10 = 45.78% and 92.46% respectively). Higher removal efficiencies were associated with increased pressure drop across the biofilter. An assessment of plant morphological data suggested that the root structure of the plants strongly influenced removal efficiency. These findings demonstrate the potential to enhance active botanical biofiltration technology with appropriate plant species selection

Mapping Urban aerosolized fungi: Predicting spatial and temporal indoor concentrations

© 2018, Society for Human Ecology. All rights reserved. The prediction of bioaerosols, specifically airborne fungi, can be achieved using various mapping techniques, potentially enabling the determination of ambient indoor concentrations within environments where people spend most of their time. The concentration and composition of indoor air pollutants are determined by a multitude of variables, with building ventilation type being the most predominant factor in most scenarios. A predictive statistical model-based methodology for mapping airborne fungi was developed utilizing satellite-based technology. Mapping was carried out for total aerosolized fungal spores and the diversity of aerosolized fungi in Sydney, Australia, over four seasons. Corresponding data for a range of environmental parameters known to influence airborne fungi were also used, notably green space density, land cover, altitude, meteorological variables, and other locally determined factors. Statistical models previously developed from the combined meteorological and environmental variable data were used to establish spatiotemporal models for airborne fungi across the study area for each season. Results showed that the models produced reasonable predictions of monitored aeromycota concentrations; although, the accuracy of these predictions for individual survey periods was variable. Using known indoor/outdoor (I/O) ratios of airborne fungi for the area, the prevalence and concentrations of indoor aeromycota were modeled for buildings with both natural and mechanical ventilation. As accurate manual assessment of the aeromycota is labor, time, and cost intensive, the current findings should assist in the prediction of fungal aerosols in both urban and indoor environments. Additionally, understanding the indoor microbiome has great importance for the health and well-being of the occupants concerned

Understanding the impacts of air pollution on human experience: Two case studies

In the months that preceded the global spread of COVID-19, a series of airborne events transformed the atmosphere of the Indo-Pacific region; the bushfire smoke on the East coast of Australia, the tear gas used in the Santiago de Chile and Hong Kong protests, the Indian Supreme Court ruling on Delhi’s pollution failures, and activists covering iconic statues with respirators across Johannesburg and Pretoria. All these incidents map the political struggles taking place in the region’s air, triggering a proliferation of masked faces avant la lettre. The publication Folk Costumes, Indo-Pacific Air is an account of the region’s masked state. It brings together culturally and geographically diverse case studies exploring air’s effects on the body to describe the emergent wearable architectures it produces. Considered as folk costumes, these wearables are socio-technical constructions that mediate our relationship with the environment—they negotiate our daily struggles, emancipatory efforts, and emotional inner-lives. Discussing air as a political matter, the book collects contributions by scientists, writers, historians, architects, photographers, and dilettantes, encouraging readers to fly freely between visual and conceptual affinities to create a map of a region in the making

A competitive model for determining air pollution in urban areas: The potential for vegetation for air pollution mitigation

Over the past few decades, the relationship between air pollution and urban forestry has been receiving increasing consideration as global cities have undergone rapid transformation. Urbanisation has resulted in population densification and increased air pollution due to the increased anthropogenic sources. Consequently, urban forestry has been proposed as one of the solutions as it has the potential to mitigate and ameliorate urban air pollution. This research investigated the spatial extent of four air pollutant concentrations and urban forestry to determine the relationship between air pollution concentrations and urban forestry across Sydney, Australia. Ambient air pollutant concentrations and other variables such as land cover, population density, dwelling density, were combined to create a Land Use Regression (LUR) model to develop predictive models for urban CO, NO₂, SO₂, and PM₁₀ concentrations. Differences in pollutant concentrations were assessed with ArcGIS and analysis of covariance across various land cover types; active vegetation, non-active vegetation and bare ground. The relative influence of predictor variables for pollutant concentrations were determined using a stepwise multiple linear regression. An inverse relationship between urban forestry and air pollution was observed and quantified in the land cover model. Furthermore, tree canopy cover was negatively correlated with all four air pollutants and urban indicators of pollution including dwelling density, population density and traffic count was positively correlated with the pollutants. This LUR model established a statistically significant spatial relationship between urban forestry and air pollution mitigation and amelioration. These findings confirm urban forestry’s capabilities to mitigate and ameliorate air pollution on a city-wide scale. Furthermore, these findings could be incorporated in to or used to develop urban planning and greening policies whilst promoting urban forestry uptake in Sydney

The evolution of botanical biofilters: developing practical phytoremediation of air pollution for the built environment

Indoor air quality is of emerging importance due to the rapid growth of urban populations that spend the majority of their time indoors. Amongst the public, there is a common perception that potted plants can clean the air of pollutants. Many laboratory based studies have demonstrated air pollution phytoremediation with potted plants. It has, however, been difficult to extrapolate these removal efficiencies to the built environment and, contrary to popular belief, it is likely that potted plants could make a negligible contribution to built environment air quality. To overcome this problem, active green walls have been developed which use plants aligned vertically and the addition of active airflow to process a greater volume of air. Although a variety of designs have been devised, this technology is generally capable of cleaning a variety of air pollutants to the extent where comparisons against conventional air filtration technology can be made. The current work discusses the history and evolution of air phytoremediation systems from potted plants through to practical botanical air filtration

Grey to Green Transition: mapping a way forward for green walls

Youtube: https://www.youtube.com/watch?v=-3KUUGyUwAg Urbanisation and densification continue to present a unique set of environmental challenges, as declining urban green spaces are intrinsically linked with population growth, urban sprawl and development. Consequently, the loss of green space also comes with increased air pollution, elevated levels of noise pollution, loss of biodiversity and the increase in urban heat island effect. Further, space limitations are characteristically an issue faced in urban areas as green space is often in competition with other land uses or socioeconomic priorities. Despite these issues, many global cities aim to achieve sustainability targets or green goals in the near future. For example, the City of Sydney’s current goal is to have 40% green cover by 2050, while the cities of Melbourne and Brisbane aim to achieve their 40% green cover targets by 2040 and 2031 respectively. But, it is unknown if it can be achieved with the cities’ current structures and designs. Increasingly, green walls (GWs) have been considered an adaptive environmental solution to space-limited urban areas while potentially improving the sustainability and regreening of cities. Therefore, evaluation methods are required to allow for appraisal to see if existing walls can be retrofitted with GWs. Furthermore, there is a lack of feasibility studies aimed at quantifying the potential for retrofit suitability of GWs across large urban areas or cities. This study developed a preliminary evaluation tool for GW suitability in high density urban areas. Using the tool, the quantity of walls across five major Australian cities that could potentially incorporate GWs was determined. Each wall was analysed using a set of criteria that assessed and ranked the wall based on its suitability. Interestingly, major cities across Australia varied in terms of greening potential with the cities of Sydney and Brisbane recording the greatest proportional length of walls suitable for GW implementation, with approximately 34%. Comparatively, the cities of Perth and Adelaide had the least greening potential, with less than 5% for each city, as many walls were excluded due to the prevalence of glazed facades and heritage buildings. Furthermore, Australian cities had very few GWs present with less than 1% of surveyed walls already greened. These results indicate that cities like Sydney and Brisbane could realistically achieve their targets if they incorporated urban forestry vertically. Though, Perth and Adelaide may need to consider other greening options such as green roofs. These results also highlight the importance of green walls and green roofs as a solution to the space-constrained areas that are characteristic of our urban cityscapes and they offer a green alternative to urban parklands and forestry that may not be viable in the future. Additionally, the accessibility of this tool will allow interested individuals, communities and organisations to assess the retrofit suitability of an area for GW implementation with minimal requirements in terms of training or resources, and could be applied globally. Subsequently, the outcomes of this study emphasised the need for more governmental support and incentives to encourage GW uptake, and this tool could play a pivotal role in the expansion of green infrastructure and urban forestry