The coal is contaminated with toxic metals at the trace levels. They are released into the environment during mining, handling and burning of coal. The Korba basin has one of the largest coal exploitation areas in the country. In this work, contamination and sources of toxic metals i.e. Hg and Pb in the air, soil and sediment of the Korba basin, India are described. The concentration of Hg and Pb in the ambient air was ranged from 7.4 - 29 and 7.0 - 585 ng/m 3 with mean value of 18 ± 4 and 129 ± 104 ng/m 3 in the winter season. The mean concentration of Hg in the soil and sediment was 0.22 ± 0.03 and 0.44 ± 0.08 mg/kg, respectively. The higher concentration of Pb in the environmental samples was observed.
Heavy metals i.e. Pb and Hg are highly toxic to the developing brain and nervous system [
The Korba basin (22˚21'N, 82˚40'E) has largest coal deposit in the country extending over ≈530 km2. Several open and underground coal mines are in operation with production of >10,000 MT/Yr coal. They are consumed by the thermal power plants running in the basin for production of electricity (40,000 MW) by pouring effluents into the environment. The population (≈0.5 million) of the basin is exposed severely with particulate and fly ash pollution. The increased prevalence rate of air and water borne diseases in human and domestic animals was observed.
The sampling network for collection of particulate matters (PM), soil and sediment is shown in
The Anderson sampler (1531-107B-G289X) with eight stages: PM10.0-9.0, PM9.0-5.8, PM5.8-4.7, PM4.7-3.3, PM3.3-2.1, PM2.1-1.1, PM1.1-0.7 and PM0.7 was used for the collection of respirable particulate matters in the segregation forms. The sampler was run for 72 hr at four locations in January, 2013. The mass of dried loaded and blank filters were weighted out.
The surface soil (0 - 10 cm) samples from 30 locations of the basin were collected in January, 2013 [
The weighed amount of the sample was digested with acids by the microwave probe by using prescribed procedure. The Pb and Hg contents were analyzed by the Varian GF-AAS and CV-AAS techniques. The elemental or black carbon (BC or EC) and organic carbon (OC) were analyzed by the thermal and titration methods [
The atmosphere of Korba basin is dusty due to huge emission of coal and ash particulates. The meteorology of the studied area during the winter period (2012-13) is summarized in
The distribution of the PM in the ambient air is summarized in
S. No. | Sampling location | Sampling date | Temperature (T) ˚C | Humidity (H), % | WS km/hr | WD | ||
---|---|---|---|---|---|---|---|---|
Min | Max | Min | Max | |||||
1 | Korba city | 26-12-2012 | 8 | 25 | 32 | 61 | 4 | E |
2 | ITI colony | 27-12-2012 | 11 | 27.5 | 54.5 | 77 | 4.5 | SE |
3 | CSEB colony | 01-01-2013 | 17.5 | 27.5 | 65 | 92 | 4.5 | E |
4 | Manikpur | 02-01-2013 | 10.5 | 24 | 27 | 47 | 8 | SE |
5 | BALCO | 05-01-2013 | 8.5 | 23.5 | 35 | 69 | 3 | SW |
6 | Kusmunda | 06-01-2013 | 14.5 | 29.5 | 40 | 65 | 3.5 | NW |
7 | Niharika | 08-01-2013 | 14 | 26.5 | 33 | 55.5 | 4 | SE |
8 | Darri | 09-01-2013 | 15 | 27 | 28 | 47.5 | 4 | SE |
9 | Mudapar | 13-01-2013 | 8 | 26 | 24 | 49 | 4 | SE |
10 | Banki | 14-01-2013 | 30 | 30 | 35 | 57 | 4 | SE |
E = East, S = South, W = West, N = North.
S. No. | PM10, µg/m3 | EC concentration | Pb concentration | Hg concentration | |||
---|---|---|---|---|---|---|---|
Ambient air, µg/m3 | PM, % | Ambient air, ng/m3 | PM, mg/kg | Ambient air, ng/m3 | PM, mg/kg | ||
1 | 315 | 26 | 8.2 | 101 | 320 | 18.8 | 59.7 |
2 | 775 | 68 | 8.8 | 585 | 755 | 18.0 | 23.3 |
3 | 196 | 16 | 8.2 | 109 | 556 | 7.4 | 37.7 |
4 | 226 | 18 | 7.9 | 83 | 368 | 17.2 | 76.2 |
5 | 209 | 16 | 7.5 | 59 | 280 | 15.0 | 71.8 |
6 | 319 | 19 | 6.1 | 7.0 | 22 | 17.0 | 53.3 |
7 | 283 | 22 | 7.7 | 71 | 252 | 24.3 | 86.1 |
8 | 666 | 46 | 6.9 | 21 | 31 | 17.4 | 26.1 |
9 | 666 | 53 | 8.0 | 193 | 290 | 29.0 | 43.5 |
10 | 251 | 18 | 7.2 | 60 | 240 | 11.7 | 46.7 |
Mercury is a highly mobile metal, being liquid at room temperature, and behaves like organic compounds. The concentration of the Hg (n = 10) in the air (associated to PM10) was ranged from 7.4 - 29 ng/m3 with mean value of 18 ± 4 ng/m3,
All the soil and sediment were composed of micrometer-scale grains with nano-scale structure. They were colored, ranging from whitish (W) to black (B) due to deposition of the fly ash and black carbon,
At least 2-folds higher concentration of Hg in the sediment was observed and may be due to its highly mobile nature. The concentration of Hg in the sediments (n = 26) was ranged from 0.12 - 0.82 mg/kg with the mean value of 0.44 ± 0.08 mg/kg. Extremely high concentration of Hg in the sediment of Hong Kong and Mumbai, maximum up to in the 0.855 - 2.66 mg/kg was reported [