Estimation of Air Quality in the Opencast Mine of Jharia Coal Field, India

A systematic air quality assessment study was carried out at Rajapur opencast mine in Jharia Division as per standard guideline. The average concentration of SPM, PM10 and PM2.5 concentrations were observed to be in the range of 294 to 965μg/m3, 100 to 498 μg/m3 and 85 to 296 μg/m3 respectively. The SO2 and NOx concentration were in the range of 48.2 to 98.2μg/m3 and 32.8 to 149.39 μg/m3 respectively. The trace metals concentration in PM10, e.g., lead, nickel, arsenic etc. were also analyzed by Atomic Absorption Spectroscopy technique and were observed to be 0.380 ± 0.009 μg/m3, 0.06 ±0.02 μg/m3, and 0.00432±0.028 μg /m3 respectively. The observed concentrations were then compared with National ambient air quality standard (NAAQS, 2009) and Ambient Air quality Standard for existing as well as new Coal Mines (CMS, 2000). Most of them were found exceeding the statutory norms.


IntrOduCtIOn
Coal mining industry now uses modern technology with powerful and high capacity machinery so as to increase coal extraction capability at the cost of large amount of dust, gases, etc. spewed into the atmosphere, thereby degrading quality of air.These pollutants have harmful consequences not only on the mine workers, but also, depending on the meteorological conditions, on the human settlements, agricultural lands and live stocks in the nearby areas.
Particulate matter is the predominant pollutant connected with the coal mining and its handling operations.The airborne particulates and the associated trace metals were found to be the major cause of both acute and chronic adverse health effects (Prieditis and Adamson, 2002;Magas et al., 2007;Wild et al., 2009).A number of epidemiological studies indicated a significant linkage between airborne particulate matters and elevated rate of mortality (Pope, 2000;Shah, 2009).

MAtErIAlS And MEthOd
Ambient air quality monitoring was undertaken at Rajapur OCP of Jharia coalfield during Summer, 2014.The sampling was done for twenty four hours and twice a week and it was continued for four weeks in summer season as per the criteria of IS 5158 Part-XIV, 2006.
Sampling for estimation of SPM and PM 10 concentrations were performed with the help of Respirable Dust Sampler with thermo-electrically cooled gaseous sampler attachment (Envirotech make).The flow rate of the sampler was maintained at 1.1-1.3m 3 /min for respirable particulate matter and 0.5 and 0.2 lpm for SO 2 and oxides of nitrogen (NOx) respectively.The respirable dust sampler (APM 460 NL) uses an enhanced model of cyclone to separate the coarser particles from the air stream before filtering it on the 0.5 micron glass-fiber poresize filter which allows a determination of both SPM and the respirable fraction of suspended particulate matter (RPM).The coarse particles collected in the cyclone separator are transferred quantitatively on a petridish and evaluated gravimetrically.Sum of masses of coarse and respirable particles gives the mass of SPM collected during sampling.The SPM concentrations are computed from the mass of SPM and total volume of air sampled.Similarly, for PM 2.5, APM 560 Fine Dust Sampler (16.7 LPM) was used.Here, ambient air is allowed to pass through Louvered inlet and WINS Impactor assembly.Particulate matter of size <2.5 microns is deposited on 46.2 mm dia.PTFE filter paper.The difference of final weight and initial weight of filter paper gives the weight of particulate matter of size <2.5 microns.The concentration of PM 2.5 is computed as the weight of dust deposited on the filter divided by volume of air sampled.The samplers were installed in the field as per the prescribed sampling siting criteria of IS: 5182 part IV giving a special emphasizes on machine safety and power availability.For analysis of trace metals in ambient air was done according to standard methodology.The acid digestion was performed in Teflon bombs.The filtrates were analyzed using AAS (GBC Avanta) for determination of trace metals.The detection limit for different trace metals for the AAS are as follows Fe (0.005 ppm), Pb (0.01 ppm), Ni (0.009 ppm), Zn (0.005 ppm), Cu (0.001 ppm, Cd (0.004 ppm), Mn 90.0015 ppm) and Cr 90.003 ppm).The concentration of an element in the atmosphere is obtained from the following relation, C(ìg/m3) = Concentration of the element in digested sample (ìg/mL)/volume of the air sample(m 3 ) x Total volume of the sample (mL)/ Percent of filter area used for analysis.

rESultS And dISCuSSIOnS
The average concentration of SPM, PM 10 and PM 2.5 concentrations were observed in the range of 294 to 965ìg/m 3 , 100 to 498 ìg/m 3 and 85 to 296 ìg/m 3 respectively.SO 2 and NOx concentration were in the range of 48.2 to 98.2ìg/m 3    The emission inventory indicates that heavy duty diesel trucks were accountable for majority of the exhaust particulate matter (Sawyer et al., 2000).The SPM concentration exceeded permission level of CMS (600 ìg/m 3 ).The movement of vehicles on the haul road of the opencast mines has been recognized as the major source of fugitive dust emitted from the surface coal mines (Cowherd, 1979).The average SO 2 concentration was below NAAQS (80 ìg/m 3 ) and CMS (120 ìg/m 3 ).The same for NO X was found above NAAQS (80 ìg/m 3 ) but below CMS (120 ìg/ m 3 ).The main source of NOx in coal mining rejoin are vehicular exhaust, blasting operations, etc. unpremeditated burning of coal in waste dumps and mine fire release considerable amount of oxides of nitrogen.During combustion process (at high temperature) atmospheric nitrogen combines with oxygen to form NO X which is aggravated when engine is diesel operated.Tunnel studies indicated that diesel engine produce five times the amount of NO X per mass of fuel burned when compared to gasoline vehicles (Kirchstetter et al., 1998).
Trace elements analysis of dust samples (PM 10 ) during summer season were done and shown in Table 2.Trace element pollutants in PM 10 may be natural or anthropogenic.Several trace elements (Pb, Cu, Mn, Co) are considered essential for life.The sources of trace elements may be attributed as discussed below: Pb (lead): may be due to higher emissions from vehicular exhausts.This does not rule out the case of adulteration of fuel for automobiles.ni (nickel): may be due to traffic exhausts, wearing and tearing of vehicular engines parts for old vehicles, etc.
As(Arsenic):Arsenic compounds can be either organic or inorganic.Inorganic arsenic can cause acute, sub acute and chronic effects, which may be either chronic or systematic.Langard,1994;Danielsen et al.,1993) and from the abrasion of brake lining and tire of the vehicles (Sadasivan and Negi,1900;Hopke,1980).

Fe (Iron) :
This is due to the use of iron in brake lining which leads to its emission in ambient air.(Hulskotte et al., 2006) Zn (Zinc): This is due to tracer of tire wear particles from vehicular movement (Birmili et al., 2006; Wang et al., 2006) Cd (Cadmium): Cd level may be related due to the composition of gasoline, motor oil, car tires and road side deposition of the residues of those materials as well as traffic density (Sharma and Prasad,2010) Cr (Chromium): Chromium is emitted mainly by fumes stainless steel welding (WHO.2000;

table 1 : Air quality data
and 32.8 to 149.39 ìg/m 3 respectively.The air quality data are depicted in Table 1.The observed concentrations were then compared with National ambient air quality standard (NAAQS, 2009).Ambient Air quality Standard for existing as well as new Coal Mines (CMS, 2000) laid down and notified by MOEF, GOI in September 2000 was also considered to evaluate the pollution status.The comparisons are presented in Fig 2 to Fig 6.The average PM 10 concentration exceeded