Hedges are ubiquitous green elements in many European cities. The selection of hedge types characterized by different traits can be suggested for urban greening projects to decrease pollution levels. At this end, carbon dioxide (CO2) sequestration and noise attenuation capability were analyzed in the following hedge types: Laurus nobilis, Nerium oleander, Pittosporum tobira and Pyracantha coccinea, largely used as green infrastructure in Rome (Italy). Representative hedges for each species were selected from high level traffic streets in the city centre (P sites). Traffic density (TD) was monitored simultaneously with CO2 concentration and noise level (N) in each of the considered P sites. The monthly CO2 sequestration capability (MSC) was calculated multiplying the total photosynthesis per hedge by the total photosynthetic activity time (in hours) per month. The multiple regression analysis predicted noise attenuation (ΔN) by a linear combination of total leaf area (TLA), total leaf density (TLD) and leaf mass area (LMA) of the considered hedge types. All the considered species, being evergreens, were active all year long, including winter, when CO2 emissions from road transport peaked. Nevertheless, among the considered hedge types, P. tobira and L. nobilis were the most efficient species in both MSC (31.6±2.8 and 25.4±2.4 kg CO2 month–1, respectively) and ΔN (15±1%, mean value). The results give insight on the use of hedges to mitigate pollution effects. Moreover, this method can be used to monitor hedge contribution to air quality, in relation to various elements in the city (i.e. traffic density, new cars produced, application of management projects, local laws). These results might be available for projects based on the use of vegetation in order to improve environmental quality in urban areas.

This study explored the interspecies and seasonal variation of polycyclic aromatic hydrocarbons (PAHs) in the extracted lipids of the leaves of seven local plants in an urban environment of Kolkata (22°33′N and 88°20′E), India. Based on the degree of toxicity and carcinogenicity (expressed in terms of their Benzo(a)pyrene equivalent (BaPeq) concentrations) the overall foliar-PAH accumulation during the study period (September 2018‒;August 2019) in the various plants showed the following order: Nerium oleander (80.96 ± 30.08 ng.gdw−1) > Mangifera indica (74.15 ± 20.34 ng.gdw−1) > Lantana aculeata (60.13 ± 21.71 ng.gdw−1) > Thevetia peruviana (40.97 ± 12.45 ng.gdw−1) > Ixora coccinea (38.11 ± 9.5 ng.gdw−1) > Murraya paniculata (37.1 ± 7.35 ng.gdw−1) > Polyalthia longifolia (25.72 ± 5.71 ng.gdw−1). The PAHs like phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, chrysene, benzo (b+k)fluoranthene, benzo(a)pyrene, benzo [ghi]perylene and indeno [1,2,3-cd]pyrene were predominant during the study period over the PAHs like naphthalene, acynaphthylene, acenaphthene, fluorine and dibenz [a,h]anthracene in the extracted lipids. The temperature-dependent partitioning of the PAHs onto leaf-surface and photo-degradation could have affected the availability of the PAHs. The foliar PAH accumulation varied seasonally as winter (December–February) > postmonsoon (September–November) > premonsoon (March–May) > monsoon (June–August). The leaf epicuticular wax determined the PAH uptake and storage, which in turn was affected by the temperature and solar radiation. In consistence with the idea of “nature-based solutions” for deteriorated air quality remediation in an urban environment, this study could be a promising initiative to build up cost-effective biological filters to combat the airborne pollutants and improve urban air quality.

It is traditionally accepted that urban vegetation contributes to improve air quality by intercepting and retaining the particulate matter. Although the mitigating role of plants has been recognized by several studies, the role of individual species is still poorly understood. This is particularly important in cities like Santiago (Chile), which has high levels of atmospheric particulate and also has high plant species diversity. In this study, we evaluated the retention of atmospheric particles by three widely distributed ornamental species (Nerium oleander, Pittosporum tobira, and Ligustrum lucidum) in Santiago. For this proposal, we took leaf samples in different sampling points across the city which vary in their concentration of atmospheric particulate. Samples were taken 12 and 16 days after a rainfall episode that washed the leaves of plants in the sampling sites. In the laboratory, leaves were washed to recover the surface retained particles that were collected to determine its mass gravimetrically. With this information, we estimated the foliar retention (mass of particulate matter retained in the foliar surface) and daily retention efficiency (mass of particulate matter retained in the foliar surface per day). We found that foliar retention and daily retention efficiency varied significantly between the studied species. The leaves of N. oleander retained 8.2 g m⁻² of particulate matter on average, those of P. tobira 6.1 g m⁻², and those of L. lucidum 3.9 g m⁻²; meanwhile, the daily retention efficiencies of particulate matter were 0.6, 0.4, and 0.3 g m⁻² day⁻¹ for N. oleander, P. tobira, and L. lucidum, respectively. These results suggest that the studied species retain atmospheric particulate matter differentially in Santiago. These results can be attributed to differences on leaf surface characteristics. The recognition of the most efficient species in the retention of the atmospheric particulate matter can help to decide which species can be used to improve the air quality in the city.

In this study, the effects of industrial and urban pollution on Pb, Al, Cd, Cu, and Zn accumulation, peroxidase activity, and pigment and protein contents were investigated in shrub and tree leaves in Antakya, Turkey. We determined that industrial and traffic activities produce the most plant-incorporated air pollutants in Antakya City. Cu and Al amounts were high in plants in the urban street location and Cd, Pb, and Zn amounts where high for all plants in the industrial site. Acer negundo L. showed maximum Pb and Zn accumulation at the industrial site and Al accumulation for the urban street site. Higher Cd and Cu amounts were detected in Platanus orientalis L. and Nerium oleander L. in the industrial and urban street sites, respectively. Compared to the control site, decreases in pigment and total soluble protein contents and increases in peroxidase enzyme activity were more evident in industrial and urban street sites. Our results indicated that industry and urban air pollution is high in Antakya City and Pb pollution was at an especially alarming level for vegetation and human health.

Air pollutant concentration of Trivandrum, the capital of Kerala, exceeded the limits of National Ambient Air Quality (NAAQ) standards, according to a study conducted in 2015 by NATPAC. These polluted corridors harbour vegetation on roadsides and traffic islands, planted solely for aesthetic appeal. Analysis of air pollution tolerance levels of existing plants can act as a scientific basis for efficient planning of the urban landscape. Sixty-seven species, including flowering, fruit-bearing, ornamental, shade-providing and timber-yielding species, were screened for their relative resistance to air pollution. Based on leaf pH, relative water content, chlorophyll and ascorbic acid levels, the Air Pollution Tolerance Indices (APTI) of each species were formulated and they were grouped into the following: tolerant, moderately tolerant, intermediate and sensitive groups. Agave americana (18.40), Cassia roxburghii (17.63), Anacardium occidentale (11.97), Cassia fistula (11.60), Mangifera indica (11.59) and Saraca asoca (10.88) may be considered for planting near green spaces like roundabouts and near pollution prone industrial areas, as they belong to tolerant category. Comparison of APTI during summer and monsoon also revealed the stability of Agave americana, Saraca asoca, Ficus benghalensis, Peltophorum pterocarpum, Ficus elastica, Ixora finlaysoniana, Mangifera indica, Canna indica and Delonix regia in maintaining pollution tolerance even during water disparity. Agave americana, Anacardium occidentale, Ficus elastica, Mangifera indica, Syzygium cumini, Ficus benghalensis, Nerium oleander and Ficus benjamina were found to be suited for mass planting, as was evident from their Anticipated Performance Indices (API).

The ability of aquatic (Juncus effusus L., Scirpus holoschoenus L., Thypha latifolia L. and Juncus sp.) and land (Cistus ladanifer L., Erica andevalensis C.-R., Nerium oleander L., Isatis tinctoria L., Rosmarinus officinalis L., Cynodon dactylon L. and Hordeum murinum L.) plants from Portugal (Aljustrel, Lousal and São Domingos) and Morocco (Tighza and Zeida) mining areas to uptake, translocate and tolerate heavy metals (Cu, Zn and Pb) was evaluated. The soils (rhizosphere) of the first mining area are characterized by high acidity conditions (pH 2–5), whereas from the second area, by alkaline conditions (pH 7.0–8.5). Physicochemical parameters and mineralogy of the rhizosphere were determined from both areas. Chemical analysis of plants and the rhizosphere was carried out by inductively coupled plasma emission spectrometry. The sequential chemical extraction procedure was applied for rhizosphere samples collected from both mining areas. In the acid conditions, the aquatic plants show a high capacity for Zn bioaccumulation and translocation and less for Pb, reflecting the following metal mobility sequence: Zn > Cu > Pb. Kaolinite detected in the roots by infrared spectroscopy (IR) contributed to metal fixation (i.e. Cu), reducing its translocation to the aerial parts. Lead identified in the roots of land plants (e.g. E. andevalensis) was probably adsorbed by C–H functional groups identified by IR, being easily translocated to the aerial parts. It was found that aquatic plants are more efficient for phytostabilization than bioaccumulation. Lead is more bioavailable in the rhizosphere from Morocco mining areas due to scarcity of minerals with high adsorption ability, being absorbed and translocated by both aquatic and land plants.

The experiment was carried out during two seasons (spring and autumn) of the year 2015, in El-Max (industrial zone) and Antoniadis park (control zone), Alexandria, Egypt. Nerium oleander L. plants has been used in this experiment because of its capability to remediate heavy metals (HMs) from the soil. This study aimed to evaluate the performance of the Phytoremediation Uptake Model (UPM) in predicting the uptake of HMs (lead (Pb), cadmium (Cd), and zinc (Zn)) from the soil. UPM was used to estimate the contribution of various pathways in the remediation of these HMs through different parts, leaves, stem, and root. Besides, it includes soil-root-leaf and soil-leaf pathways and its deposition. The performance of the UPM has been examined using many statistical calculations tools (Person correlation coefficient (R²), root mean square error (RSME %), mean bias error (MB %), and Willmott index of agreement degree (d)). The results showed a high harmony between the UPM predictions and the experiment. Moreover, most R² values are ranged mostly between 0.97 and 0.99 during the spring and the autumn in the study areas. Therefore, the correlation is very strong between the measured and the predicted HMs concentrations. In addition, the less value of RMSE% (0.13) was obtained in the lower parts of the plant, while the greatest value was observed in leaf model (42.53). Also, the values of MB% were acceptable and within the range between 3.01 and 10.41. In addition, the values of the Willmott index of the agreement were within the acceptable range (0.80 to 0.97). Thus, one may conclude that the UPM has proved a high performance in estimating the uptake and removal of different concentrations of HMs from soil under different spatial and temporal conditions.

The vegetation plays important role in urban environment and associated ecology. Urban vegetation experienced various changes due to biotic and natural interference which alter the vegetation structure, function and ecology. The present study deals with the assessment of shrub species structure, diversity, biomass, volume, C storage and CO₂ mitigation potential in an urban setup. Total four sites were selected, viz., east, west, north and south directions of Ambikapur City. A sum of eight shrub species representing seven families was recorded in Ambikapur City area. The highest representatives were recorded towards east direction (seven species with six families) and lowest towards south direction (five species with five families). The total density of shrubs ranged between 230 and 570 individual ha⁻ ¹ being highest at east direction and least at south direction. The higher diversity was found at east direction. The shrub biomass was ranged between 0.999 and 2.603 t/ha being highest at north direction and lowest at east direction. The shrub volume, C storage and CO₂ mitigation values reflected similar trend as in case of shrub biomass. The shrub volume, C stock and CO₂ mitigation values were ranged from 0.141 to 0.250 m³/ha, 0.437 to1.132 t/ha and 1.597 to 4.156 t/ha, respectively, among the various sites. The species like Cestrum nocturnum and Nerium oleander are found to be potential in terms of various ecological services such as biomass, C storage and CO₂ mitigation in different sites. However, Lantana camara was also found to be potential species under urban setup which can be utilized for its various ecological functions. Further, it was found that the contribution of the non-native species was higher over native species in terms of stand density, basal area, biomass, C stock, volume and CO₂ mitigation potential among different study sites.

Tanning sludge enriched with high concentrations of Cr and other metals has adverse effects on the environment. Plants growing in the metalliferous soils may have the ability to cope with high metal concentrations. This study focuses on potentials of using native plants for bioindication and/or phytoremediation of Cr-contaminated sites. In the study, we characterized plants and soils from six tanning sludge storage sites. Soil in these sites exhibited toxic levels of Cr (averaged 16,492 mg kg⁻¹) and other metals (e.g., 48.3 mg Cu kg⁻¹, 2370 mg Zn kg⁻¹, 44.9 mg Pb kg⁻¹, and 0.59 mg Cd kg⁻¹). Different metal tolerance and accumulation patterns were observed among the sampled plant species. Phragmites australis, Zephyranthes candida, Cynodon dactylon, and Alternanthera philoxeroides accumulated moderate-high concentrations of Cr and other metals, which could make them good bioindicators of heavy metal pollution. High Cr and other metal concentrations (e.g., Cd and Pb) were found in Chenopodium rubrum (372 mg Cr kg⁻¹), Aster subulatus (310 mg Cr kg⁻¹), and Brassica chinensis (300 mg Cr kg⁻¹), being considered as metal accumulators. In addition, Nerium indicum and Z. candida were able to tolerate high concentrations of Cr and other metals, and they may be used as preferable pioneer species to grow or use for restoration in Cr-contaminated sites. This study can be useful for establishing guidelines to select the most suitable plant species to revegetate and remediate metals in tanning sludge-contaminated fields.

PURPOSE: The aim of this work was to investigate the possibility of using several bush and arboreal plant species, usually present as ornamental plants in street and parks, as environmental indicators of pollution. This is a research paper that evaluates the real possibility of using a fast and low-cost procedure to evaluate the pollution degree through data obtained from plant species growing within an urban environment. METHODS: Leaves of six different bush and arboreal species were collected from different parts of Madrid (Spain), ranging from highly polluted considered areas to medium and low contaminated ones. A total of 66 chemical elements, from major to minor and trace, were determined for every leaf sample by inductively coupled plasma-mass spectrometry. Statistical analyses were carried out using mainly box and whisker plots, linear discriminant analysis and cluster analysis. RESULTS: The pollution by different elements of the studied areas of Madrid cannot be considered generally dangerous for human health. The level detected for the contaminants, in general, is similar or lower than other urban cities. Pb and V concentrations in plant samples tend to increase as traffic density increases. The different studied plant species showed a different capability of accumulation of certain elements. Cedrus deodara accumulates specially Ag, Hg, Mo and V; Cupressus sempervirens, Zr; Pinus pinea, As and Sb; Nerium oleander Ni, Pb, Mo and Se; Ligustrum ovalifolium, Sc and V; and Pittosporum tobira, Ag, Cd, Rb and Sc. CONCLUSIONS: The leaves and needles collected from bush and arboreal plants common in this city have demonstrated to be useful to evaluate the level of pollution not only through the chemical analysis but also through the recognition of the visual injury symptoms. The application of multivariate statistical techniques combined with determining of element concentration and correlation analysis has been proved to be an effective tool for reach the objectives of the present work. This allows visualising quickly the damages and leading the sampling through the points of high-level pollution, saving analysis, time and money.