Particulate matter bio-monitoring through magnetic properties of an Indo-Burma hotspot region

ABSTRACT Present study aimed to investigate the bio-monitoring study of particulate matter (PM) pollutants of 12 roadside plant species, in Aizawl, Mizoram, India (an Indo-Burma hot spot region). While, the second part was ascribed to the bio-magnetic monitoring stidies. Pertaining to first part of study, highest dust deposition was noted for Ramrikawn (RKN-Med) site on Ficus bengalensis (1.2 mg cm−2) and lowest in Bauhinia variegate (0.8 mg cm−2). Further, increased concentration of heavy metals (Fe, Cu and Zn) was recorded at RKN-Med site. Roadside plant leaves of F. bengalensis recorded maximum accumulation of Fe (26.1 mg kg−1) and Cu (19.5 mg kg−1) while Cassia auriculata (12.1 mg kg−1) showed lowest accumulation of Fe. B. variegate (1.88 mg kg−1) recorded lowest accumulation of Cu. Zn was recorded maximum (48.2 mg kg−1) in Mangifera indica while B. variegate showed lowest accumulation of 11.3 mg kg−1 Cu at Ramrikawn site. In relation to second part of the study, M. indica, Ficus benghalensis, Psidium guajava and Artocarpus heterophyllus were found to be efficient in bio-magnetic monitoring because all the magnetic properties (magnetic susceptibility, anhysteretic remanent magnetisation and isothermal remanent magnetisation) were high and significantly correlated with ambient PM (R2 = 0.424 to R2 = 0.998) thus may act as proxy for ambient PM.


Introduction
Air pollution originating from rapid industrialisation, urbanisation, population growth and economic development has perturbed the pristine environment of urban ecosystems. Unfortunately, urban ecosystems of ecologically sensitive regions like Indo-Burma hot spot are under severe air pollution stress. [1,2] Air pollutants comprised of both particulate matter (PM) and gaseous pollutants may cause adverse health effects in human, affect plant life and impact the global environment by changing the atmosphere of the earth. [3][4][5] Air pollution emanating from PM is particularly deleterious as they lead to various cardio-pulmonary diseases through oxidative stress. [5,6] Many studies highlighted the importance of PM with an aerodynamic diameter of less than 10 µm (PM 10 ), which, due to their small size, can penetrate deep into the human lung and cause cardio vascular diseases. [4][5][6][7][8] These fine and ultrafine particulates have higher burdens of toxicity as they become coated with heavy metals and chemicals, which, when inhaled, can become absorbed into the body and may target specific organs. [5,6,[9][10][11] Heavy metals are classified among the most deleterious groups of anthropogenic environmental pollutants due to their toxicity and persistence in the environment. [86,87] Presence of heavy metals in the roadside and PM in the ambient air is serious and has adverse human health effect. Presence of heavy metals above their threshold level also could be potentially harmful on local vegetation and environment. Elevated levels of heavy metals may cause oxidative stress either by inducing the generation of reactive oxygen species (ROS) within sub cellular compartments or by decreasing enzymatic and non-enzymatic antioxidants due to an affinity with sulphur-containing group (-SH). [86,87] Disturbance in heavy metals concentration can cause significant modification of biochemical processes in plants leading to loss of production, [86,87] lower yield and quality of agricultural crops. Loss of hazel nut production due to high zinc concentration was shown in the leaves of Corylus avellane. [86,87] Excessive copper may destroy sub cellular structure of plants. [ Instead of existing plethora of policies as well as instrumentation technologies with high cost issue and other limitations, [6] urban roadside plants are inextricably linked with eco-sustainability. [2,6,9] Deposition of PM pollutants on leaf surface induces structural and functional changes. [2] Although, plants are very important to maintain urban ecosystem health, however, may be severely affected by PM pollution. [2,4,6,[12][13][14][15][16][17][18] Air Pollution Tolerance Index (APTI) as well as Anticipated Performance Index (API) and impact of PM pollutants on heavy metals and enzyme activity (peroxidase and catalase) of urban roadside plant species may assist in screening of tolerant plants which may be further recommended for green belt development assisting in urban ecosystem restoration. [2,4,17] Pertaining to bio-magnetic monitoring, it is worth to mention that initial researches demonstrated biogenic ferrimagnets be present in the organisms like termites [19] and bacteria. [20] However, it is now well established through cascade of researches that urban PM may also contain magnetic particles along with other air pollutants. [6,[21][22][23][24][25][26][27] Another research in hilly Himalayan region measured magnetic susceptibility (χ) of soils, sediments and roadside materials, in and outside the Kathmandu urban area and magneto-mineralogical analyses as well as scanning electron microscopy on magnetic extracts, grain size fractions or bulk samples of road dust and soils, suggest lithogenic magnetite like minerals and anthropogenic magnetic spherules to be the dominant contributors to the χ signal. [28] Magnetic minerals derived from diverse sources are particularly deleterious to human health in view of their small size and thus their ability to be inhaled inside lungs and get dissolved in alveolar environment leading to several pulmonary as well as cardiovascular diseases. [6] Existing conventional technologies for PM pollution abatement have several limitations; however, bio-magnetic monitoring is an eco-friendly device in urban areas. [6] In this perspective, urban roadside plants presents an eco-sustainable approach. [4,6] Lichens, bryophytes or mosses and certain conifers were may also act as bio-monitoring tool of air pollution in recent times.4,6] However, in urban and peri-urban regions angiospermic plants are mostly suitable for monitoring dust or PM pollution as lichens and mosses are often sensitive and absent. [4,6,29] Further, urban trees and shrubs planted in street canyons proved to be efficient dust capturing tools. [17,30,31] Spreading widely in urban area and easily collected, tree leaves could improve the scanning resolution in the spatial scale. [4,32,33] With the rapid, cost-effective, and non-destructive feature of environmental geomagnetism measurement, the magnetic properties of tree leaves as proxy in monitoring and mapping of PM pollution have drawn increasing attention. [4,34] Therefore, urban angiosperm trees offer positive biological, ecological impacts in comparison to lower plants. [4,6,16,30,31] Several researches demonstrated the magnetic properties of soil, roof and street dust, [35][36][37][38][39][40][41], and parts of plant other than plant leaves like tree bark, [4,31,42] however, a growing body of literature have emphasised the use of plant leaves in monitoring the dust or PM. [4,6,24,27,30,31] Thus, in view of this, magnetic bio-monitoring studies of roadside plant leaves were conducted in Singrauli industrial region as well as Varanasi urban region of India, [6,26,43,44] in some cities of Portugal and mountain areas of Nepal. [45] Further, different researches enriched the bio-magnetic monitoring literature in European countries. [46][47][48] However, the diversity of plants investigated for their bio-magnetic monitoring potential is limited mostly to plants prevailing in temperate conditions, and therefore, field is ripe for the investigation in context of tropical plants. [6] Aizawl, the capital city of Mizoram observed the increase in the number of vehicles and hence PM. [9] Therefore, vehicular pollution may be the primary contributor of particulates, specifically respirable suspended particulate matter (RSPM), having human health implications. Our preliminary study in Aizawl [4,49] recorded the level of suspended particulate matter (SPM) and RSPM above permissible limit of National Ambient Air Quality Standards. Further, PM below the size of 10 μm (PM 10 ), are specifically hazardous to human health, [50] therefore their monitoring is pertinent. [9] Apart from vehicular dust generation other sources are soil erosion, mining and stone quarrying activities prevailing particularly in peri-urban and rural regions of Aizawl. [9] Furthermore, increasingly, air-borne PM emitted from geologic media pose threats to human health as well as the environment. [9,29] Also, the rocks of Aizawl are very fragile; therefore, weathered rock dust may also get deposited on plant leaves. In Indian sub-continent several researches demonstrated significant correlation between magnetic parameters and PM, [26,43] however, they analysed single magnetic parameter while in present study we included several parameters. [4] Several studies have been performed on the impacts of air pollution with selected plants only in urban polluted regions, [2,6,15,[51][52][53] however, no systematic study on bio-monitoring as well as bio-magnetic monitoring has been done in urban portion of ecologically sensitive hilly regions like Aizawl, Mizoram, North East India which is also an integral part of extremely diverse Indo-Burma hot spot region of Myers. [49,54] Further, plant's response may alter under varying pollution stress; however, till date no study has been done in ecologically sensitive hilly regions of Indo-Burma hot spot region to study the impacts of PM pollution on urban roadside plants with their possible phyto-technological innovation.
In the light of abovementioned discussion, present study deals with the quantification of air pollutants in the ambient air, assess the impacts of air pollutants with special reference to PM deposition on plant leaves, heavy metals, and enzymatic activities of some common urban roadside plant species in an Indo-Burma hot spot region. Further, the second part of study attempts to study the bio-magnetic monitoring implications and screen the potent plants which may act as proxy of ambient PM.

Site description
Mizoram (21°56 ′ -24°31 ′ N and 92°16 ′ -93°26 ′ E) is one of the seven sisters state under North East India (Figure 1), and it occupies an area of 21,081 km 2 . The forest vegetation of state falls under three major categories, that is, tropical wet evergreen forest, tropical semi-evergreen forest and sub-tropical pine forest. [55] Aizawl district comes under Indo-Burma hotspot region of North East India, [54,56] having variety of diverse plant species possess varying leaf morphology which can be utilised in sampling of dust deposition and hence, the study of magnetic parameters. The diversity of tropical evergreen plants prevails along the roadsides of Aizawl district, and therefore, it can retain the pollutants throughout the year; offering no seasonal constraint. [9] This study was conducted quarterly, that is, summer, rainy, and winter during 2013-2014. Twelve common roadside plants namely Ficus bengalensis, Ficus religiosa, Mangifera indica, Bougainvillea spectabilis, Psidium guajava, Hibiscus rosa-sinensis, Lantana camara, Delonix regia, Artocarpus heterophyllus, Cassia auriculata, Bauhinia variegate and Lagerstroemia speciosa of mixed habits, including shrubs, small trees and large trees were selected for the study for their dust deposition and biochemical studies thus, dust deposition and biochemical parameters were studied on seasonal basis (Table 1). APTI and enzymatic activity (catalase and peroxidase) were studied in winter and summer season at Ramrikawn (RKN-Med; peri-urban area and Mizoram University MZU-Low; a rural area). The plants were selected due to their abundance, ease of sampling and their livelihood importance for local people. The species and characteristics of the selected plants at both the study sites with their leaf characteristics are given in Table 1. At each sampling site, three individual of each selected plant species were marked and 5-10 leaf samples per plant species are collected from the lower branches (at a height of 2-4 m) facing towards roadside in early hours of morning (8 am to 12 am) through random selection and were put in polythene bags, kept in ice box, brought to the laboratory and enzyme activity was studied immediately. The leaf samples were preserved at −20°C for various biochemical analyses within 24 h of their harvesting.
While for bio-magnetic monitoring ten plants were selected at four differentially polluted sites (as the magnetic properties were negligible for the rest two plants). For study of magnetic parameters of plant leaves, the leaves are brought in to laboratory of Department of Environmental Science, Mizoram University. Leaves are dried at 35°C and recorded the dried weight; samples are prepared for magnetic analysis, which involves in packing the dried leaves into the 10 cc plastic sample pots. [4]

SPM and RSPM
Air pollutants such as SPM and RSPM were analysed for the four selected sites was monitored by using 'High Volume Air Sampler' (Envirotech model, APM-460NL) with gaseous attachment (Envirotech model, APM-411TE) regulating eight hours per day in the year of 2013-2014 with a frequency of twice in a season. The apparatus was kept at a height of 2 m from the surface of the ground. Once the sampling was over, the samples were brought to the laboratory and concentration of different pollutants was determined. RSPM were trapped by glass fibre filter papers (GF/A) of Whatman and SPM were collected in the separate containers at average air flow rate of 1.5 m 3 min −1 .

Dust deposition
Three replicates of fully mature leaves of each species were marked. The upper dorsal surface of all these leaves were cleansed using a fine brush and the dust were collected in pre-weighed tracing paper with maximum care. The selected leaves were cut from the petiole and carefully taken to quantify dust accumulation. The individual leaf area was calculated by tracing marginal outline on a graph paper and average from three leaves was taken into consideration. The samples were weighed using an electrical digital balance and the amount of dust was calculated using the equation: where W = Dust content (in milligrams per square centimetre), W 1 = initial weight of tracing paper, W 2 = final weight of tracing paper with dust and A = total area of leaf in (cm 2 ). [17]

Heavy metal analysis
Trace elements (Fe, Cu and Zn) were extracted by digesting leaf samples with 1 mL of 50% perchloric acid, 5 mL concentrated nitric acid and 1 mL concentrated sulphuric acid at moderate heat. [57] The concentrations of Fe, Cu and Zn in the extract were determined by using an Atomic absorption spectrophotometer (model 370A, PERKIN ELMER).

Estimation of enzyme activity (catalase and peroxidase)
For the determination of some antioxidant enzyme activities, enzyme extraction procedure was prepared according to Nayyar and Gupta [58] with some modification in relation to quantity of reaction mixture (1000 µl), enzyme extract (50 µl) and concentration of H 2 O 2 (10 mM). Aforesaid components may vary in quantitative perspective in varying protocols. Catalase activity was determined according to Aebi [59] by monitoring the decomposition of H 2 O 2 . In 1 mL of reaction mixture contain potassium phosphate buffer (pH 7.0), 50 µl of enzyme extract and 10 mM H 2 O 2 to initiate the reaction. The reaction was measured at 240 nm for 5 min and H 2 O 2 consumption was calculated using extinction coefficient, 43.6 M − 1 cm −1 and was expressed in units per mg protein.
Peroxidase activity was determined using the guaicol oxidation method by Chance and Machly [60]. 3 mL reaction mixture contains10 mM potassium phosphate buffer (pH 7.0), 8 mM guaicol and 50 µl enzyme extract. The reaction was initiated by adding 10 mM H 2 O 2 . The increase in absorbance was recorded within 5 min at 470 nm due to the formation of tetra guaicol. A unit of peroxidase activity was expressed as the change in absorbance per min and specific activity as enzymes units per mg soluble protein (extinction coefficient 6.39 mM −1 cm −1 ).

APTI and API of plant species
APTI plays a significant role to determine resistivity and susceptibility of plant species against pollution level. To evaluate the tolerance level of plant species to air pollution [18] used four leaf parameters (i.e. relative water content, pH, chlorophyll content and ascorbic acid) to derive an empirical number indicating the APTI. The APTI was calculated using the formula as given below. [18] where, A = Ascorbic acid (mg g −1 ), T = total chlorophyll (mg g −1 -f.w.), P = pH of the leaf extract and R = relative water content of leaf (%).
By combining the resultant APTI values with some relevant biological and socio-economic characters (plant habit, canopy structure, type of plant, laminar structure and economic value), the API was calculated for different species. Based on these characters, different grades (+ or −) are allotted to plants. Different plants are scored according to their grades. [53]

Magnetic parameters
As mentioned earlier bio-magnetic monitoring study was carried out in Aizawl district from four different sampling points (Figure 1). Site 1: Durtlang (Urban area); Site 2: Zarkawt (Urban area); Site 3: Ramrikawn (peri-urban area); Site 4: Mizoram University Campus (MZU). MZU campus is an institutional area with low traffic density. Therefore, we selected MZU as reference or control site in order to compare the results recorded from other sites. Further, we took winter season as dust or PM tends to concentrate during this season through atmospheric inversion [60] particularly during morning hours. Further, in our recent research [17] we recorded maximum dust deposition during winter season. This suggests that localised conditions like environmental, meteorological or anthropogenic may be influencing or disturbing particulate deposition or it may reflect differences in the ability of leaf species to capture particulates. [9] The magnetic parameters such as χ, anhysteretic remanent magnetisation (ARM) and saturation isothermal remanent magnetisation (SIRM) were performed with dried leaves in 10 cc plastic sample pots at K.S. Krishnan Geomagnetic Research Lab of Indian Institute of Geomagnetism, Allahabad, Uttar Pradesh, India.
The χ indicates the total composition of the dust deposited on the leaves, with a prevailing contribution from ferromagnetic minerals, which could show higher susceptibility values than paramagnetic and diamagnetic minerals, such as, clay or quartz.

Statistical analysis
All statistical calculation was performed using Statistical Programme for Social Science (SPSS version 11.2) and SAS software.

Result and discussion
Ambient air quality of Aizawl revealed high PM Concentrations {(both SPM as well as RSPM}) particularly during winter and summer season ( Table 2).
High dust deposition was recorded for all the plant species at the RKN-Med (Ramrikawn) site and the trend of dust trapping capacity among the plant species was F. bengalensis > P. guajava > B. spectabilis > M. indica > L. camara > H. rosa-sinensis > L. speciosa > A. heterophyllus > F. religiosa > D. regia > C. auriculata > B. variegate (Figure 2). Analysis of the dust or PM collected from the leaf surface indicated the presence of some high concentration of toxic heavy metals such as Fe, Cu and Zn. Significant positive correlation recorded between dust deposition and heavy metals (Fe, Cu and Zn) at both MZU-Low and RKN-Med site ( Table 2). High concentrations of heavy metals in plants of RKN-Med site may be due to heavy traffic frequency and more commercial and domestic activities when compared the MZU-Low site. Verma and Singh [61] also demonstrated high metals concentration at heavy polluted sites in Lucknow, India compared to low polluted site while using F. religiosa and Thevetia nerifolia as bio-monitoring tool.
The accumulated metal concentrations in leaves of plants differ from one species to another in response to dust or PM accumulation. [17] Foliage of F. bengalensis recoded maximum accumulation of Fe (26.1 mg kg −1 ) and Cu (19.5 mg kg −1) while C. auriculata    translocated to other parts of the plant through active uptake mechanism. [17,54,56,60] However, in certain cases through other mechanisms metals may adhere as plaques on root surfaces without uptake and translocation to other parts of the plant. [17] Alfani et al.
[71] observed that metal concentration was significantly higher in leaves from the urban roadside plants. They [71] also observed a positive correlation between leaf deposition and leaf metal accumulations. Therefore, plants growing along the roadsides may also work as phyto remediator of air-borne metals released from the vehicles and street dust. [9,17,60] Presence of these heavy metals in the dust or PM may also play an important role in disturbing the various physiological, biochemical and metabolic processes in plants. [6,9,17,60] (Table 2). P. guajava (36.11 ± 0.06 U mg −1 protein) showed highest catalase concentration and D. regia (4.10 ± 0.01 U mg −1 protein) showed lowest catalase concentration. Highest peroxidase concentration was recorded in D. regia (0.18 ± 0.02 U mg −1 protein) and lowest in L. speciosa (0.04 ± 0.03 U mg −1 protein).
In plant cells, electron may be transferred through chloroplast or mitochondrial electron transfer system. These electrons can produce ROS, when come into contact with oxygen molecules.  The plant cells have several antioxidantive enzymes {(superoxide dismutase (SOD), glutathione reductase, catalase and peroxidase}) and low-molecular antioxidants such as ascorbic acid, glutathione, α-tocopherol, flavonoids and carotenoids to protect plants against these oxidative stressors. [78][79][80][81] Pollution load increases catalase and peroxidase content in this study may be a function of ROS production in response to air pollution stress. ROS or free radical production under pollution stress would increase the scavenging properties of enzymatic and non-enzymatic metabolites, particularly catalase and peroxidase, as well as other compounds such as ascorbate, carotenoid, SOD [18] based on dosage and plant physiological status. Varshney and Varshney [82] reported increase in peroxides activity in plants under a variety of stresses like mechanical injury and attack by pathogen or an influence of environmental pollution. The increase in peroxidase and catalase activity varies with the plant species and the concentration of pollutants. [18] At different study site, F. bengalensis is evaluated as the best variety, P. guajava as excellent and M. indica is judged to be very good, while L. speciosa was recognised as good performer. The API of the examined plant species at both the sites showed that Ficus benghalensis, P. guajava, M. indica and L. speciosa have similar API value (Table 3). These plants can be consider the most tolerant plant to grow in polluted areas which may afford protection from pollution stress while the economic and aesthetic values of these trees are well known and thus they may be recommended for future plantation in the industrial and urban areas to combat atmospheric particulate pollution.
Screening of appropriate plant species might be useful for plantations, to mitigate atmospheric pollution. Ecological conservation and pollution abatement through Green Belt are two major components which are vital for any activity, whether proposed existing  or under expansion stage. An evaluation of APTI and API might be very useful in the screening of appropriate plant species, useful for plantations to mitigate atmospheric pollution and maintain a social-aesthetic balance in environment surrounding industrial and urban areas. The result form a basis for the selection of tolerant species fit for industrial and urban sites continuously exposed to elevated level of particulate pollutants. Therefore, roadside plants of present study i.e. P. guajava, F. bengalensis and M. indica with high API and APTI value can be used as sink and mitigators of air pollutants originating from multifaceted sources at heavily polluted sites while B. variegate and D. regia with low APTI and API value may act as bio indicators of air (particulate) pollutants. On the basis of above data a suggestive ecological model around a polluted site is proposed to ensure a relatively pollution free environment worth for human habitation. Plants with some economic and aesthetic value, dense canopy and large leaf area may be selected for green belt development in industrial/urban areas. The present study is a strong first step and warrants further efforts which may paves the way to screen the feasibility of this plants in context of their potentiality to be planted in other urban areas with varying pollution load.
[91] Zerovalent Iron, which is the fourth most plentiful element in the Earth's crust at nano-scale possesses very potent magnetic and catalytic properties. Iron nanoparticles (NPs)/nanocomplexes are widely used in the field of engineering, medicine, agriculture and environment. Iron NPs find application in removable electronic media, mobile phones, electrical components, sensors, transducers, targeted drug delivery, cancer treatment, magnetic resonance imaging, hyperthermia, water purification, etc.            [90] Ramrikawn site shows slightly higher magnetic values comparing to the other sites. On the other hand, Ramrikawn and Zarkawt experiences relatively higher deposition of magnetic grains, originating from PM. χ, ARM and SIRM values are found to be higher for F. bengalensis, M. indica, A. heterophyllus, P. guajava and L. camara comparing to other plants. The spatial trends of these three magnetic parameters display similar trends having Ramrikawn at maximum value and MZU area at lowest value. The correlation coefficients indicated significant relationship between the concentration of PM and magnetic measurement for ten plant leaves (Supplementary Tables 10-19). Hansard et al. [47] studied atmospheric particle pollution emitted by a combustion plant using the tree leaves. Results show that a significant correlation is obtained between the SIRM and PM 10 . Rai et al. [4] also observed a good correlation of magnetic parameters (χ, ARM and SIRM) with air pollutants particularly heavy metals. Further, Kardel et al. [48] recorded significant correlation between leaf SIRM and ambient PM concentrations. The other studies also demonstrated a significant correlation between magnetic parameter and PM. [26,43] The average magnetic concentration data (Tables 4-7) demonstrate that the accumulation of PM on tree leaves varies at different studied locations. The results suggest that Ramrikawn and Zarkawt experience the heaviest load of particulates in comparison to the low-deposition sites of Durtlang and MZU area. Ramrikawn recorded the highest values of magnetic parameters which may be attributed to heavy vehicular load, street dust and dust from fragile rocks. Zarkawt and Durtlang may have vehicular pollution as only source of PM while MZU, being a rural area is relatively free from vehicular pollution and other anthropogenic activities. F. bengalensis, M. indica, A. heterophyllus, P. guajava and L. camara leaves were rougher when compared to Bauhinia variegata, C. fistula, H. rosa-sinensis, F. religiosa and B. spectabilis which may be attributed to its high magnetic concentrations.
Sitewise, plants from Ramrikawn, Zarkawt and Durtlang showed high pollutant magnetic concentration due to tall buildings which may tend to concentrate the pollutants through the low dispersal of pollutants. At MZU site dispersal of particulates may take place due to lack of high buildings and multilane condition. Further, at Ramrikawn site there exist narrow as well as poor roads with heavy traffic, street dust load and tall buildings.
Finally, Supplementary Tables 10-19 clearly indicates the positive and significant correlation of magnetic measurements/properties of different plants with SPM and RSPM at four different study sites. Plants like M. indica, F. benghalensis, P. guajava and A. heterophyllus were found to be efficient in bio-magnetic monitors because all the magnetic properties (χ, ARM and SIRM) were high and significantly correlated with ambient PM.

Conclusions
Urban roadside plants of present study i.e. F. bengalensis, F. religiosa, M. indica, B. spectabilis, P. guajava, H. rosa-sinensis, L. camara, D. regia, A. heterophyllus, C. auriculata, B. variegate and L. speciosa may be used as control of PM pollutants originating from multifaceted sources after further research at heavily polluted urban sites. The present study is a strong first step and warrants further effort which may paves the way to screen the feasibility of these plants in context of their potentiality to be planted in other urban areas with varying pollution load. It will further enhance the conservation of biodiversity of these plants and their wide utilisation as well as sustainable management in respect of green belt development. [83][84][85][86] In nutshell, the use of urban roadside plants as bio indicators or biomarker is an inexpensive and convenient technique and thus offers an eco-sustainable green tool for urban ecosystem restoration. Results from second part of this work validate the magnetic analysis of roadside tree leaves as proxy indicators of PM pollution. Magnetic concentration data suggest that the deposition of PM on roadside tree leaves varies due to different traffic behaviour between sites and due to other activities like soil erosion, mining and stone quarrying etc. The magnetic analysis of dust loadings on roadside tree leaves provides an alternative proxy method to conventional pollution monitoring. Present study may be a novel contribution in the area of bio-magnetic as well as bio-monitoring as the previous related studies confined their quest mostly to temperate plants, concentrating on single magnetic parameter. However, in present study we have selected several bio-monitoring parameters (dust capturing potential, APTI, API, heavy metals, enzymatic activities) and three magnetic parameters (χ, ARM and SIRM). Study concluded that bio-monitoring as an eco-sustainable tool while bio-magnetic monitoring as an application of environmental geomagnetism may act as proxy for ambient PM pollution and may act as a cost-effective green tool for environmental management in urban and peri-urban regions. Moreover, tolerant roadside plants find their suitability for plantation in ecologically sensitive regions having implications for urban ecosystem restoration.