Journal of Scientific & Industrial Research Vol. 60, October 200 I, pp 786-797
Air Pollution due to Opencast Coal Mining and It's Control in Indian Context
M K Ghose • and S R Majee
Centre of Mining Environment. Indian School of Mines, Dhanbad 826004, India Received: 29 January 200 I; accepted: 29 June 200 I
Open cast mining dominates the coal production scenario in India. It creates more serious air pollution problem in the area.
Coal production scenario and its impact on air quality is described. To maintain the energy demand in opencast mining i~
growing at a phenomenon rate. There is no wcll-clefinccl method for assessing the impact on air quality clue to mining projects.
An investigation is conducted to evaluate the impact on air environment due to opcncast coal mining. Emission factor data arc utilized for computation of dust generation due to different mining activities. Approach for the selection of work zone and ambient air monitoring stations arc clcscribccl. Work zone air quality, ambient air quality, and seasonal variations arc discussed.
which shows high pollution potential clue to SPM. The status of air pollution clue to opencast mining is evaluated and its impact on air environment is assessed. Characteristics SPM show a great concern to human health. Air pollution control measures involve planning and implementation of a series of preventive and suppressive measures in addition to dust extraction system.
The study reveals that there is a need for wider application of dust control chemicals and an in depth techno-economic survey i~
essential. Different abatement measures for control of air pollution arc enumerated. Air pollution control by trees. rrees tolerant to dillerent air pollutants and plant species useful for controlling air pollution is discussed. The methodology adopted could be utilized on industrial scale for various sites.
Introduction
Coal is the primary source of energy'. The develop- ment of various industries has a cascading affect on the demand of coal. With the rapid rate of growth of industries, the future demand of coal will be very high.2 But the utilization of coal would be limited by environmental disruption, including deterioration of air quality due to the emission of particulate matter and other gaseous pollutants from various mining operations, which, in general, have adverse environmental impacts. The magnitude and significance of air pollution, caused by mining, depends on method of mining, scale and concentration of mining activities, geological and geomorphological setting of the area. In India, coal production will have to be increased to meet the energy demand at the rate of 20-25 Mt/y (ref 3). In underground coal mining humans suffer from coal mining inside underground workings but opencast mining creates much more air quality deterioration in respect of dust and gaseous pollutants in and around the mining complexes.
Opencast mining dominates the coal production scenario in India due to the techno-economic factor, better safety, etc. At the time of nationalization in 1973, when the total
· Auti1or for corresponclcncc
coal production was 75 Mt/y the share of opencast mining was 20 per cent. By 2000 AD when the total coal production was 417Mt the share by opencast mining reached about 70 per cent and the future plan envisages larger share by opencast mining.
In opencast mining, a massive overburden will have to be removed to reach the mineral deposits. This may require excavators, transporters, loaders, conveyer belts, etc., which will results in massive discharge of fine particulate from the overburden materials. Similarly normal operations will also require excavation, transportation, loading, unloading, size reduction, stock piling etc4. All of these will generate particulate matter '· The volume and variety of air borne dust particles in the ambient air is ever increasing and causing air pollution problem in the surrounding areas. Cowherdr' has reported that vehicular traffic on haul road of mechanized opencast mines can contribute as much as 80 per cent of the dust emitted. Chadwick et of. 7 have estimated that about 50 per cent of total coal dust released during journey time on an unpaved haul road, while 25 per cent for both during loading and unloading of dumper.
Drilling is perhaps the next important source of fugitive dustK. Another major source of fugitive dust is wind erosion from coal stockpiles.
GHOSE & MAJEE: AIR POLLUTION DUE TO OPEN CAST MINING 787
Over exploitation of nature in the name of industrialization and development is causing degradation of our environment. At the same time, we do relalise that we cannot stop the development in the name of saving environment only. A balance between sustainable development and environment management is the need of the hour. Environmental impact assessment (EIA) plays a crucial role in resolving the conflicts'1. Thus, it is necessary to assess the impacts on air environment due to opencast coal mining so that proper metigative measures could be implemented. However there is no well-defined method of assessing the impacts on air environment due to opencast coal projects. To evaluate the impact on air environment a fact-finding survey is essential. In this study attempts have been made to develop a methodology to evaluate the status of air pollution due to opencast coal mining and to suggest control measures for the control of air pollution.
Materials and Methods
The study area was one of the largest opencast coal projects (OCP) for coking coal in Jharia Coalfields (JCF).
It has 34.6 Mt quarriable reserve of coal. The project report was sanctioned in the year 1982 for a targeted production of 2.5 Mt/y and the life of the project was 17 y. The quarry was being worked in two patches through separate box cuts. Working depth during the study period was about 60 m in box cut three sections.
Working was going on in X seams having seam thickness of 9.62 m. The project is located in the north-west of JCF in Dhanbad district of Jharkhand State. It covers an area of about 6.8 sq km It is located between latitudes 23°46'30"N and 23°47'4"N and longitudes 86°10'47"E and 86°13 '31 "E. It is surrounded by many open cast and underground coal mines.
Work zone air quality monitoring stations were selected near the sources of air pollution111• The details of the monitoring stations are given in Table I and 2.
Ambient air monitoring stations were selected, keeping in view the dominant wind directions prevailing in the area. One ambient air monitoring station was located in the project office of OCP. The dominant winds directions of the area"·" were Wand NW. During the selection of ambient air monitoring stations the approach was to put two monitoring instruments at upwind (Wand NW) and two instruments at downwind (E and SE) directions. The approach was also to see that these should cover the industrial, residential and sensitive area like hospital as different standards have been laid by Central Pollution
Control Board (CPCB) 13, Government of India. The sampling was continued twice a week for four weeks in a month of each season covering winter (January), summer (May-June), monsoon (August) and post- monsoon (October) seasons.14· Air samples were collected for 24h in three 8h shifts corresponding to daytime, evening, and nighttime. Micrometeorological data were collected on sampling days with respect to wind direction, wind velocity, humidity and temperature.15· "'. SODAR data were collected from a monostatic and Doppler SODAR make M/s Ramtech, France installed at Central Mining Research Station (CMRI), Dhanbad. The parameters studied were wind speed and direction, mixing height, ventilation coefficient (VC).
For the collection of samples of suspended particulate matter (SPM), glass fibre ambient (GF/ A) filter paper was used in a high volume sampler (HYS) and for respirable dust particulate matter (RPM) GF/ A was used in respirable dust sampler (RDS) at a flow rate of 1.1 to 1.5 m'/min that allows the SPM to deposit on the filter paper. Particulate with size range of 0.1 to I 0011m was collected by HYS17. The cut-point diam ofRDS was less than I 011 m. Both, HVS and RDS were manufactured by M/s Envirotech Ltd, New Delhi. HYS, having impingers (bubbler trains) in series with sodium tetrachloromercurate as absorbing solution, were operated at an average flow rate of 0.5L /min for collection of SO (as per IS: 5182, Patt II 1969) for 24h.fn the case of collettion of NO sodium hydroxide was used as absorbing solution and collected at an average flow rate of 0.5L /min for 24h (as per IS: 5182, Part IV 1976).
The impinger samples were put in ice boxes immediately after sampling and transferred to a refrigerator prior to analyse. The samples were analysed spectra- photometrically. using West and Gake methods and Jackob and Hocheiser modified methods for analysis of SO and Nox, respectively17 SPM and RPM were co~puted after weighing the filter paper before and after sampling. The filter paper was conditioned in a dry atmosphere before weighing.
Particle size analysis of SPM was done on the basis of the principle of photo-extinction and sedimentation techniques with a Micron Photosizer manufactured by Seisin Enterprise Co. Ltd, Japan (Model SKN I 000). Attachment of centrifuge with the unit had made it pos- sible to determine size distribution up to 0.02 p. Respi- rable dust sampler (RDS) make Envirotcch, New Delhi
788 J SCIIND RES VOL 60 OCTOBER 2001
Table !- Location of work zone monitoring stations
Sl No. Station site Location
BWI Feeder breaker Roof of feeder breaker control room at about 3m above the ground BW2 Haul road (HR I) At a height of about 2m on the debris at one side of the haul road BW3 Haul road near box cut On the other of haul roard near near the hox cut 3 office
3 section (HR2) at about 3 m above the ground
BW4 Dragline section At a distance of I OOm from the draglinne at about 2m above the ground BWS Shovel/dumper loading On the immediate above the bench of a working bench
BW6 Workshop Roof top of a room ncar the workshop area which is about 3m above the ground
Table 2-Locations of different ambient air monitoring stations
Stn No. Station site Nature of area
BAI Block II OCP Industrial
BA2 Benidih OCP Industrial
survey office
13A3 Nudkhurkee Residential
BA4 Madhuband Residential
BAS Benidih hospital Sensitive
was used to determine respirable particulate matter (RPM). In RDS, the dust-laden air is imparted with a rotating motion by virtue of its tangential entry into the cyclone. Due to this rotation, dust particles >I 0 1J de- posit on the walls of the cyclone and settle below and the air containing the RPM travels up and is collected over GF/ A filter paper. Cascade impactor was also used for particle size analysis (make Graseby, Anderson, UK).
Assessment of Impact on Air Environment
The sources of air pollutants were identified and different mining activities were recorded along with production of coal and overburden materials. During the study period the mine was producing 2500 t coal /d and overburden removal was 9950 m3/d. Emission factor data
Direction from Location Block II OCP
Centre On the roof top of the Block II pit oiTice which about 4m above the ground level E On the roof top of the survey office at
about 4m above the ground
w On the roof top of a villager's house which about 7m above the ground SE On the roof top of a villager's house ;ll
about 3m above the ground
NW On the roof top of the hospital at about 4m above the ground
were utilized for assessing dust generation clue to different mining activities1x.20. It has been estimated that different mining activities generate dust, which accounted 9 .36t clust/d21• The dust generated by eli fferent activities contributes SPM as well as settleable fractions in the surrounding locations.
The data of four seasons revealed that SPM concentration for almost all the monitoring stations exceeded the permissible limit specified by Central Pollution Control Board (CPCB) (Table 3) during winter, pre-monsoon and post-monsoon periods. During the monsoon period, SPM fell within the permissible limit due to the removal of dust particulate with rainwater. In fact, they exceeded the permissible limits specified for industrial (500 pg/m3), residential (200 pg/m1) and
GHOSE & MAJEE: AIR POLLUTION DUE TO OPEN CAST MINING 789
Table 3-National ambient air quality standards (Central Pollution Control Board, New Delhi)
Pollutant
Sulphur dioxide (S02 )
Oxides of nitrogen as N02 Suspended particulate matter (SPM) Respirable particulate matter (RPM)
Time weighted average
Annual* 24 h**
Annual*
24 h**
Annual* 24 h**
Annual*
24 h**
Sensitive Industrial
15pg/rn' 80pg/m3 30pg/m3 120pg/m .\ 15pg/m' 80pg/m3 30pgtm·' 120pg/m3 70pg/rn3 360pg/m 3 I 00pg/rn1 500pg/rn3 50pg/rn.1 120pg/rn.1 75pg/m .1 150pg/m.1
Concentration in ambient air
Residential, Methods of measurement Rural
60pg/m3 !.Improved West and Gake method 80pg/m3 2.Uitra lluorescence
60pg/m3 I Jacob and Hocheiser modified 80pgfm3 method
2 Gas phase chemilluminesencc 140pg/rn 3 - High volume sampling 200pg/rn3
60pg/rn3 - Respirable particulate matter 100pg/m3 sampler
Lead (Pb) Annual* 0.50pg/m3 I.Opg/m1 0.75pg/m3 - AAS method after sampling using 24 h** 0.75pg/m·' 1.5pglm3 I.Opg/m3 EPM 2000
Carbon 8 h** I.Omg/rn3 5.0mg/m3 0.50pg/rn1 - Non-dispersive infrared monoxide (CO) I h 2.0mg/nr' I O.Omg/m.1 0.75pg/m3 spectroscopy
*Annual arithmetic mean of minimum I 04 measurements in a year taken twice a week 24 hat uniform interval
**24 h /8 h values should be met 98 per cent of the time in a year. However, 2 per cent of the time. it may exceed but not two consecutive days
hospital (I 00 f.lg/m3) areas. During winter, pre-monsoon and post-monsoon periods RPM concentration in the industrial location (BA I) also exceeds the permissible limit ( 150 f.lg/m3). SO and NOx concentration were also found to exceed th~ permissible limit at different occasiOns.
Seasonal variation of SPM in work zone air is shown in Figure I. Work zone air quality to be deteriorated during winter season to great extent. SPM and RPM concentrations were found to be very high and exceeded the permissible limits at all locations. Seasonal variation of SPM in ambient air at different stations is shown in Figure 2 and status of air pollution in the study area is shown in Figure 3. The data of four seasons revealed that SPM concentration for almost all stations exceeded the permissible limit specified by CPCB. Settleable dust observed at different locations also exceeded the permissible limit (I 0 mt/km2/month). The wind rose diagrams at different seasons are shown in Figure 4.
Characteristics of SPM showed the high concentration of respirable fraction, Average particle size distribution of SPM in work zone and ambient air are shown in Figure 5.
Air Pollution Control Strategy
The air pollution control measures involve planning and implementation of a series of preventive and
suppressive measures so that the levels of pollution are maintained within certain standard11. For this an air pollution strategy is formulated which refers to the master plan adopted to tackle the air pollutionY Four types of strategy have been distinguished for air pollution control.
These are:
(i) Air quality management, (ii) Emission standards, (iii) Economic, and (iv) Cost benefit.
Air quality management is the regulation of the amount, location, and time of pollutant emissions to achieve some clearly defined set of ambient air quality standards. It involves the control of pollutant emissions to ensure that these levels do not exceed the acceptable limit. It involves several steps, which are discussed within a five-fold typology (Figure 6). Emission standards are distinguished for large number of pollutants and are applied to individual or specific group of emitters. If emission standards are derived from consideration of air quality standards, this makes the emission strategy, in fact, a part of an air quality management strategy. It is also known as "best available and economically feasible control technology". Such an approach could reduce air pollution up to great extent with known methods but these
790 J SCI IND RES VOL 60 OCTOBER 2001
1.000
'E
..._01
_:. 3000 c
0
Iii -E 2000
<lJ u c u 0
1000
~ Q_
VI
Winter Summer Monsoon P-monsoon
UliiiD BW1 I FBI
~ BW4 IDSI
~ BW2 IHR1l
D sws I SOLI
Clli] BWJ IHR2l
LJ BW6 IWSPI
Figure 1- Seassunal variation or SPM in work zone air 1000,--- -
BOO
• BA1 ~ BA2 f§l BAJ ffiiiill BA' CJ BA6
Figure 2-Seasonal variation or SPM in ambient air at different stations
should be economical. Strategies, using an economic based approach to air pollution control would provide financial incentives for emission sources to pursue the most cost-effective means for reducing pollution. The emission charges strategy, based on requiring polluters to pay charges relating to the amount of pollution they emit are most frequently used. The purpose is to leave to the choice of polluters not to pollute or to pay fine heavily with penalties increasing exponentially with the degree of pollution. Economic approach to provide incentives to a fim1 to find new techniques and new products, which provides lower pollutant emissions. Cost benefit strategy first attempts to quantify the costs of all the damage resulting from air pollutants and the cost of all known ways of controlling these pollutants and then adopt the pollution control options which will minimizes the scene of pollution damages and pollution control costs. In Figure 7. conceptual approach of this form is illustrated.
If pollution control expenditure is not made, ambient air pollution concentration will be high and pollution damage cost will also go up. As control expenditure increases, the pollution concentration and associated damage costs fall.
Strotegy Adopted
As the project area includes the opencast mine, for which no emission standards have been proposed and no economic strategies have been developed, so that the strategy adopted here should be the combination of the air quality management and cost benefit strategy. On the basis of collected field data it has been observed that the main pollution problem in the area is due to the dust. A control plan has been formulated for abatement of air pollution problem. It involves the planning and implementation of a series of prcventi ve and suppressi vc
500
500
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GHOSE & MAJEE: AIR POLLUTION DUE TO OPEN CAST MINING
BA1 BA2 BA3 BA4 BAs
120
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BA1 BA2 BA3 BA4 BAS
E'3 BAL. D BAs
Figure 3 -Status of air pollution in the project area (Annual average concentration of air pollutants under study)
791
792 1 SCI !ND RES VOL 60 OCTOBER 2001
WINTER SEASON N
w ~t===r---(
SE
SW
s
MONSOON SEASON
N NW
w
sw
w
SUMMER SEASON N
SE
s
Nw'T-MONSOON SEASON
w
SE
s
Seal<.> :-1 em = 5 '/,
~ 1 7 14 28 Km/hr
Figure 4--Wind rose diagram during differelll seasons measures, in addition to the dust extraction system1~.
Dust Extraction System
The dust extraction system envisages wet type dust extractors. This includes network of suction heads and ducting connected to wet wall cyclone for separating dust from the air stream. Air outlet of cyclone collectors will have to be connected, so as to discharge clean air to atmosphere and collected dust from the cyclone shall have to be disposed off suitably. It includes the following:
(i) Wet Wall Cyclone Separators
The wet wall cyclone separators must include its all required accessories like water spray nozzles, headers, water piping hydraulic scales, solenoid valves, and isolating valves to ensure sufficient separation of coal dust from dust laden air.
100r-~
20~ ~ ---'---'~ J
s 10 20 1.0 60 eo 100
Particle size (IJ) - Work zone - 1 - Ambient tone-
Figure 5-Average particle size distribution or SPM in ambient and work zone air
GHOSE & MAJEE: AIR POLLUTION DUE TO OPEN CAST MINING
SPECIFY AIR QUALITY COMPILE AN MONITOR MONITOR STANDARDS INVENTORY OF METEOROLOGICAL AIR POLLUTION
OR GOALS SOURCE EMISSIONS CONDITIONS CONCENTRATION
I I J
l
CALCULATE AIR O.UAUTY APPLY MODEL TOJ
DEVISE A SET OF EMISSION CONTROL TACTICS TO ACHIEVE
AIR QUALITY STANDARDS
J
ENFORSE EMISSIONl
CONTROL TACTICS_j
1 l
AIR-QUA L!TY AIR-QUALITY
STANDARDS STANDARDS
ACHIEVED NOT ACHIEVED
Figure 6-Stages involved in the ambient air-quality management strategy
"'
0
u
POLLUTION CONTROL EXPENDITURE I OR COST l
TOTAL OAHAGf +CONTROL
1/cosT
I I
\ /.
' OPTIHUH /
, ....
'I ---/
...
____
... /Ambient air pollution concentration
\
POLLUTION DAHAGf COS\
Figure 7-Schematic representation of the relationship between pollution control expenditure, pollution damage cost and polluiant concentration
793
794 J SCIIND RES VOL 60 OCTOBER 2001
(ii) Air Exhaust Fan
Air exhaust fan should be of centrifugal type with radial bladed impeller. The fans should be of robust. The fan associated with dust extraction should be designed for adequate duty keeping of approx. 25 per cent on pressure rating. The fan must be vibration-free during operation and designed to limit noise level to 90 elBA. The fan and motor are to be observed for continuous operation. Relevant IS code of engineering practices has to be employed for the design and construction of impeller, shaft and bearings.
(iii) Dust Collection Hood
Necessary dust collecting hoods and MS sheet ducting of adequate size and design must be provided for guiding dust laden air from the generating points to wet wall cyclone separators and dust-free air from cyclone to atmosphere via extraction fans. The clean air from the fan has to be taken to a suitable height (not less than 2m or I .5 m above height of roof in the vicinity, which ever is more) before discharging into atmosphere. The following points should be considered while designing hood and ducting system. Centre line of hoods is to be located at the points of generation of maximum pressure. The hood connection has to be designed for collecting the dusty air from various dust generation sources. The hoods are to be adequately sized to collect all dusty air generated at the point. Velocity in the hood should not be too high as to draw the large size particle. The ducts for conveying dusty air are to be of should have round shape, having stream line appearance.
(iv) Dust Arrester
The dust produced during drilling and blasting could be minimized by arresting and filtering the dust-laden air before it is thrown into the working environment.
Dust arresters commonly used with clown the hole drills at the collar of the holes being drilled.
(v) Dust Extractors with a Filtering or a Porous Layer
The filtering unit may be made of solid and continuous consisting of paper, which gives a very high efficiency. The filtering layer may comprise friable material such as loose powder, sand or granular material, in a horizontal or vertical bed, cotton, wool, glass cloth with silicon and other synthetic fibres.
Dust Suppressive Measures (i) Water Spraying
The regular spraying of water over coal increases the free moisture content of the coal and also provides quantity of water needed to bind the dust and to agglomerate into a semisolid condition.
(ii) Water Spraying by Ultrasonk Dry Fogging System hy Means nf Service Nozzle
In this system, water droplets are set between 0.3 to 5.0-mm diam with the help of compressed air. With increasing fineness of droplets, the surface area affinity for dust increases, along with the number of droplets per unit volume. It is clue to the fact that the droplets roughly having the same size as that of the dust particles and as they are charged, the affinity required for wetting the dust is achieved and the dust particles agglomerate and suppresses at the source. This requires no wetting agent.
(iii) Chemicals for Dust Control
Water spraying requires huge quantity of water but clue to the scarcity of water in most of the coal mines it is required to reduce water consumption for dust suppression. It is possible only if suitable chemicals.
which act as wetting agents, are added to water. It helps in proper wetting of the finer sizes of dust and increases the efficiency of wetting.
Chemicals, useful as wetting agents are the following:
(a) Aqueous solution of CaCI , MgCI , hydrated time,
::! ~
sodium silicate. etc.,
(b) Teepol- laboratory grade product of Burmah Shell, (c) Kodak wetting agent- product of Kodak Ltd, (d) Lessapol- product ofT mperial Chemical Industries, (e) Filset 50- product of Filler Group of Company, (f) Jalasakti - A hygroscopic solid.
(iv) Haul Road Dust Consolidation
Surface mine haul road is the most prolific source of dust in surface mines25. Watering of the haul roads is the most common method of controlling dust emission. The frequency of watering has to be related to the climatic conditions. Various products are available in the market for consolidation of haul road dust as the water is quickly evaporated if the water spraying is not done at frequent
GHOSE & MAJEE: AIR POLLUTION DUE TO OPE CAST MINING
Dust Source
Blasting
Loading and unloading
Mobile equipment
Fixed plant (Crushers, screen conveyors. etc.)
Dust blow
Table 4--Abatement measures for control of air pollution at the source Control measures
2 Dust suppression by water and I or detergent 3 Use of dust arrester
I Dust may be suppression by water sprays
Before charging and blasting consideration of expected atmospheric condition I Suppress dust by automatic or mannual water sprays (with detergent) 2 Enclose of the loading and unloading area, wherever possible
I Internal roads to be surfaced 2 Exhausts fan to be directed upwards 3 Dust suppression by water sprays 4 Selection of proper routes 5 Sheeting of loads of fine materials 6 Green barrier along mine road
I Provision of enclosers
2 Use of water sprays to suppress dust
3 Use of dust collectors (bag, wet or dry centrifugal, electrostatic, etc.) 4 Green barrier all around
I Enclosure of stock piles 2 Vegetation of waste dumps 3 Water spraying to suppress dust 4 Establishment of green barriers of trees
Air Pollution Control by Trees
795
intervals. The raised dust causes the problem of visibility on the haul road, which, in turn, affects the average vehicle speed in addition to the pollution problem. The health of the workers would be affected due to high respirable dust concentration. Various products are available in the market for the consolidation of haul road dust. Hygroscopic salts extract moisture from the atmosphere and keep the road surface damp. Most common examples are calcium chloride, sodium silicate, magnesium chloride, and hydrated lime. Surfactants/
wetting agents could reduce the surface tension of water helping wetting of dust particles and thus economize the watering costs. Monitoring of SPM was done with the help of high volume air samplers. SPM was measured before and after application of the chemical (Filset-50) and found that SPM level of 263 I 11g/m3 came down to about 780 11g/m3 after one month of application. The study reveals that there is a need for wider application of dust control chemicals on the haul roads of Indian coal mines.
Plantation of trees is one of the best measures for checking the air pollution. Trees are to be selected, based on the type of pollutants, their intensity, location, easy availability and sustainability to the climate. For arresting dust pollution, trees having compact branching, closely arranged leaves, broad leaves of simple elliptical and hairy structure, shiny or waxy leaves and high proline content are suitable. A list of trees tolerant to different air pollutants is given in Table 5
Control of Air Pollution
Different abatement measures for control of dust generated from different mining operations are given in Table 4.
A wide green belt of fast growing trees should be raised around the coal project. New colonies and residential building should be created at a considerable distance from the project. To create green barrier around roadsides, fixed plants, stockpiles of OB dumps the following guidelines may be useful in increasing the efficiency:
(i) Trees should be planted in beds arranged perpendicular to the direction of prevailing wind, (ii) Trees should be planted in a concentric fashion
around the source of pollution,
(iii) Peripheral plantations may also be used as wind brakes on dry tailings,
7% .I SCI IND RES VOL 60 OCTOBER 2001
(iv) A judicious mixture of open and permeable planting with dense planting should be made to achieve maximum beneficial effect,
(v) Plants and trees of different heights should be planted on both sides of the traffic lanes,
(vi) A wide green belt of I 0-m width with 6 rows of tall fast growing trees will have to be raised around the CHP and mine complex.
Table 5-Trees tolerant to air pollutants Dust pollution
Alswnia scholoris Cassia sia111ea Dalbe1gia sissoo Ficus henghalensis F. in{t'c/oria i\1/angifi'm indiu1
Pt'lloii!IOrtllll feiTII.f!.illl'l/111 Polwt!thia lognifl'lia Shm•ea rolmsta
'li'clontl gmndis Alnus l'iridis OI.One Accr Ncgunda Accr Plwllanoides Quercus palustris
AarJ!Iatanoides A. negunda Qut'IY"IIS palustris
Sulphur dioxide Alhi:ialehheck
Ailw111111s e.rcd1·11 Alstonia sclwlaris A:adimchw indica Fims religiosa Lagestm<'lllia MiiiiiiSOIIS clw1gi Polmlthia lognift'm
Tl'llrinalia m:jww A en f'latanoides Quacus fWiustri.l·
Q. mhra
Oxides or nitrogen
Cagus orit'lllalis Quercus mhmr Nohinia f!Sellllocacia Lead
Cassia silllllt'S Zi~.1pl111s n1t111ritiww
Maiti and Banerjee21' have found that the plants can act as living filters of dust polluting in mining areas. It is reported that a 8 m wide green belt between roads and buildings can reduce the dust fall by 2-J times conifer reduce dust fall up to 42 per cent in temperate urban areas. The study indicates these evergreen plants with simple, polish surface like -Alstonia scholaris, Ficus lunea, F. henghalensis and Mognifem indica are best dust catchers. Plant species useful for controlling air pollution are given in Table 6.
Conclusions
Main air pollution problem due to opencast mining is clue to the dust. Work zone and ambient air quality data also reveal the high pollution potential in the project area and surrounding locations. The respirable fraction in SPM is founclto be high and alarming to human health.
Air pollution control measures involve planning and implementation of a series of preventive and suppression measures in addition to dust extraction system. There is a need for wider application of dust control chemicals on haul roads for which an in depth technoeconomic survey is essential. By proper implementation of suggested abatement measures, air pollution in opencast mine and its environment can be suitably controlled and also a right kind of balance between sustainable development and environmental management can be maintained. The methodology adopted rnay have formed guidelines which could be utilized on industrial scale for various sites
Acknowledgements
The authors are thankful to the Ministry of Environmental and Forests, Government of India for financial grants for infrastructral facilities at Centre of Mining Environment, Indian School of Mines. Financial
Table 6 -Useful plant spcci(;s rnr controlling :~ir pollution along with their ch:1racteristics Speci:tl properties
(i) Puhe~cence on leaves t0 entrap : and hold dust panicle'
(ii) Leaves and branches to slow winll. (iii) Blossoms and foliage that prmidc
plca~ant smell to mask: ndnur.
(il) Lca1·cs and br;111chc' to slow the act1on of r;Jill\:
(v) Plants th;ll absorb SO
NdlllC or species
Cua:ama, Putrwrjil'£1, N1·ctantlll's, Trenw, llolof!i'leliu. Tem1inalia
Alhi::ia. Smnania, PellmJJiwmlll. h1111arindus /)ei!Jagio Morinda. Cl'sllwn. Locntmw, Anona, /11iclll'litl, .laslllillltlll (itms, Plu1ncritt, !11ognoliu.
A:an!ichw. Nelia. Acacia a,,,·icn!twfrnmis. /)c/oni.r Ca.Hw Lir·lll'tts. Fagus, Acer
GHOSE & MAJEE: AIR POLLUTION DUE TO OPEN CAST MINING 797
support in the form fellowship received from the University Grants Commission to S R Majee is gratefully acknow I edged.
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