The study of heavy metal (HM s) contamination of environment is of great interest due to their serious health hazard. In this work, the contamination of tree leaves with the HM s in the most polluted industrial city, Korba, India is described. The leaves of common trees i.e. Azadirachta indica, Butea monosperma, Eucalyptus, Ficus religiosa, Mangifera indica and Tectona grandis were selected for assessment of the HM s contamination as bioindicator. The elevated concentration of HM s ( i.e. As, Fe, Cr, Mn, Cu, Zn, Cd, Pb and Hg) in the tree leaves was observed, ranging from 2.8 - 43, 728 - 5182, 8.6 - 49, 48 - 1196, 43 - 406, 79 - 360, 1.12 - 1.65, 1.6 - 16.4 and 0.13 - 0.76 mg/kg, respectively. The concentration, enrichment and sources of the HM s in the leaves are described. Azadirachta indica leaves, accumulating higher concentration of the HM s, showed a higher efficiency as bioindicator for the urban pollution.
The quality of environment (i.e. air, water and soil), microorganism activities, plant growth, etc. are affected by heavy metal (HMs) contaminations [
The Korba coal basin, Chhattisgarh, India (22˚21'N, 82˚40'E, above >250 m from seas levels) was selected for the proposed investigation due to extreme environmental pollution. The area is covered by the dense tropical moist and deciduous forest dominated by trees i.e. Tectona grandis, Shorea Robusta, Pterocarpus marsupium, Anogeissus latifolia, Madhuca indica, Dendrocalamus strictus, Azadirachta indica, Butea monosperma, Eucalyptus, Ficus religiosa, Mangifera indica, etc. Several open and underground coal mines are in operation with production of >10,000 MT/Yr coal. The most of electricity (40,000 MW) of the state is produced by the thermal power plants emitting effluents in the city. The Asia biggest aluminium plant with captive power plant of 1200 MW is also in operation. The population of city is ≈ 1 million, being exposed with severs particulate and fly ash pollution.
The sampling networks of soil and plant samples are shown in
A 0.5 × 5 kg of the surface soil samples (0 - 10 cm) from rhizospheric zone of five trees of each species was collected in January, 2013 from Manikpur, Korba as prescribed in the literature [
The leaves from five trees of each species (≥10 Yrs old) were collected manually in January, 2013, washed thoroughly with deionized water and dried in a shed [
The soil sample was mixed with deionised water into 1:2 (w/v) ratio in a 100-ml conical flask. The suspension was allowed to stand an overnight, and pH value of the extract was measured by Hanna pH meter type-HI991300.
A 0.25 g each of soil sample was digested with 8 ml aqua regia in the closed microwave vessel for 15 min. Similarly, 0.25 g dried leave sample was digested with 5 ml HNO3 + 2 ml H2O2. An aliquot of the extract was diluted with deionized distilled water for further analysis. Similar procedure was applied for the digestion of the soil (NCS DC73382, Spex Certiprep, UK) and leaf (NIST-1515, USA) reference samples.
The Varian Liberty AX Sequential ICP-AES (plasma flow: 15 L/min, auxiliary flow: 1.5 L/min, power: 1 KW, PMT voltage: 650 V) was used for analysis of the metals i.e. Cr, Mn, Fe, Cu and Zn. A VARIAN “SpectrAA 220Z” model graphite furnace atomic absorption spectrometer (GF-AAS) equipped with a longitudinal Zeeman effect background corrector and THGA tube, auto sampler and automatic data processor was employed for analysis of metals i.e. Cd and Pb. The VARIAN “SpectraAA 55B equipped with hydride/cold vapour regenerator accessories was selected for analysis of elements i.e. As and Hg. The accuracy of the method for analysis of the metals (n = 3) in the reference materials was found to be ≤2%. The precision of the analysis for the metals in soil and leaf samples was ≤ 5%.
The enrichment factor (Ef) is used to assess pollution of heavy metals in soil with respect to crustal contributions [
where, symbols Cm and CAl denote the concentration of the metal and aluminium in the soil and crust. The background concentration of Al, Fe, As, Cr, Mn, Cu, Zn, Cd, Pb and Hg in the earth crust reported was 81,500, 39,200, 4.8, 92, 775, 28, 67, 0.09, 17 and 0.05 mg/kg, respectively [
The physico-chemical characteristics of the rhizospheric soils are summarized in
The concentration of HMs in the dried leaves is summarized in
The As content in the lichens of Mandav Monuments, India was reported maximum up to 51.95 mg/kg [
The bioaccumulation factor (Bf) of the metals (ratio of leaf to soil content) in the leaves is presented in
The result of factor analysis in tree leaves is given in
Soil | Color | pH | Mean value (n = 5) mg/kg | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
As | Cr | Mn | Fe | Cu | Zn | Cd | Pb | Hg | |||
S1 | Br | 6.96 | 15.5 | 59 | 749 | 33,818 | 50 | 36 | 1.31 | 36.2 | 1.37 |
S2 | Bk | 6.85 | 20.0 | 62 | 618 | 34,218 | 56 | 40 | 1.39 | 32.7 | 1.81 |
S3 | Br | 6.37 | 15.6 | 72 | 1760 | 38,499 | 56 | 44 | 1.38 | 47.7 | 1.71 |
S4 | Bk | 6.16 | 15.8 | 34 | 314 | 17,718 | 49 | 26 | 1.11 | 18.5 | 1.95 |
S5 | Br | 7.12 | 10.8 | 53 | 634 | 45,426 | 59 | 50 | 1.52 | 27.2 | 1.16 |
S6 | Br | 7.18 | 12.2 | 64 | 780 | 38,700 | 62 | 62 | 1.10 | 35.2 | 1.26 |
S = Soil, Br = Brown, Bk = Blackish.
Plant | As | Fe | Cr | Mn | Cu | Zn | Cd | Pb | Hg |
---|---|---|---|---|---|---|---|---|---|
Mangifera indica | 3.9 | 1570 | 9.5 | 302 | 77 | 86 | 1.65 | 3.3 | 0.17 |
Eucaliptus | 2.8 | 728 | 8.6 | 1196 | 43 | 184 | 1.20 | 1.7 | 0.20 |
Butea monosperma | 3.0 | 2400 | 14.6 | 343 | 55 | 86 | 1.15 | 1.6 | 0.76 |
Ficus religiosa | 3.1 | 1700 | 21.3 | 58 | 48 | 83 | 1.12 | 1.8 | 0.17 |
Tectona grandis | 6.4 | 2891 | 14.3 | 48 | 98 | 79 | 1.20 | 1.8 | 0.13 |
Azadirachta indica | 43.1 | 5182 | 48.6 | 94 | 406 | 360 | 1.12 | 16.4 | 0.36 |
Plant | As | Fe | Cr | Mn | Cu | Zn | Cd | Pb | Hg |
---|---|---|---|---|---|---|---|---|---|
Mangifera indica | 0.24 | 0.05 | 0.16 | 0.41 | 1.54 | 2.41 | 1.26 | 0.10 | 0.13 |
Eucaliptus | 0.13 | 0.03 | 0.14 | 1.94 | 0.77 | 4.61 | 0.87 | 0.06 | 0.10 |
Butea monosperma | 0.20 | 0.05 | 0.22 | 0.19 | 0.98 | 1.98 | 0.84 | 0.03 | 0.43 |
Ficus religiosa | 0.20 | 0.10 | 0.62 | 0.19 | 0.98 | 3.17 | 1.01 | 0.10 | 0.10 |
Tectona grandis | 0.59 | 0.05 | 0.27 | 0.08 | 1.66 | 1.58 | 0.78 | 0.06 | 0.10 |
Azadirachta indica | 3.54 | 1.33 | 0.76 | 0.11 | 6.55 | 5.80 | 1.01 | 0.48 | 0.36 |
Variable | Factor-I | Factor-II | Factor-III |
---|---|---|---|
Cd | −0.35 | 0.79 | 0.03 |
Cr | 0.93 | −0.12 | 0.30 |
Cu | 0.97 | 0.06 | 0.21 |
Fe | 0.83 | −0.15 | 0.50 |
Mn | −0.16 | −0.02 | −0.98 |
Pb | 0.97 | 0.09 | 0.15 |
Zn | 0.97 | 0.00 | −0.23 |
Hg | −0.37 | −0.75 | 0.03 |
As | 0.98 | 0.02 | 0.17 |
Eigenvalue | 5.90 | 1.25 | 1.15 |
% Variance | 65.60 | 13.90 | 12.74 |
% Cumulative Variance | 65.60 | 79.49 | 92.23 |
Loading value > 0.70, significant at p < 0.05.
Cd | Cr | Cu | Fe | Mn | Pb | Zn | Hg | As | |
---|---|---|---|---|---|---|---|---|---|
Cd | 1.00 | ||||||||
Cr | −0.44 | 1.00 | |||||||
Cu | −0.24 | 0.94 | 1.00 | ||||||
Fe | −0.35 | 0.90 | 0.92 | 1.00 | |||||
Mn | 0.06 | −0.46 | −0.35 | −0.60 | 1.00 | ||||
Pb | −0.19 | 0.94 | 0.99 | 0.86 | −0.29 | 1.00 | |||
Zn | −0.32 | 0.84 | 0.90 | 0.69 | 0.07 | 0.92 | 1.00 | ||
Hg | −0.19 | −0.27 | −0.34 | −0.14 | 0.10 | −0.33 | −0.33 | 1.00 | |
As | −0.28 | 0.95 | 1.00 | 0.90 | −0.32 | 0.99 | 0.92 | −0.33 | 1.00 |
The soil of the Korba city, India is highly polluted with As, Cu, Pb and Hg due to coal burning and mining. The highest phytoextraction of the HMs was observed with Azadirachta indica leaves; it may be due to interaction of the alkaloids with the metals. Significant Bf values (>1) for metals i.e. As, Cu and Zn with the Azadirachta indica leaves were marked. The Azadirachta indica leaves could be considered as bioindicator for soil pollution of the HMs in the coal burning area of the country.
We are thankful to the Alexander von Humboldt Foundation, Bonn, Germany for granting financial support to one of the author: KSP.
Khageshwar SinghPatel,ReetuSharma,Nohar SinghDahariya,AnkitYadav,BorislavBlazhev,LaurentMatini,JonHoinkis, (2015) Heavy Metal Contamination of Tree Leaves. American Journal of Analytical Chemistry,06,687-693. doi: 10.4236/ajac.2015.68066