An Empirical Model to Evaluate SPM Concentration in a Colliery Area

Jharkhand , a state in India is rich in minerals particularly coal. Large number of mines is excavated here. Opening of new mines and expanding existing mines causes air pollution. The main pollutants emitted are suspended particulate matter, oxides of nitrogen, sulphur dioxide and carbon dioxide. In this paper empirical models are developed to calculate SPM concentration in terms of NOx concentrations and SO2 concentrations. It has been seen that there is a good linear relationship between hourly SPM and NOx concentrations and also between SPM and SO2 concentrations.


Introduction
Jharkhand is a mineral rich state in India. It has lot of deposits of minerals like iron, manganese, coal etc. Availability of commercial energy at affordable price is critical for industrial development of India. In the present scenario coal remains the cheap and abundantly available source for commercial energy. Increase in production will be achieved through opening new mines and expanding existing mines. Hence lots of mining operations are carried out in Jharkhand.
Air Quality Modeling is an attempt to predict or simulate the ambient concentrations of contaminants in the atmosphere.Many empirical and polynomial models have already been employed for estimating pollutant concentrations (Dastoor and Pudykiewicz, 1996;Binkowski and Ching, 1996;Stalbones et al., 1998;Cohn et al., 2001;Vardoulakis et al., 2003).. Karim M.M. and Ohno.T have developed an empirical model to evaluate SPM concentrations for the city of Nagoya, Japan. The model applies a linear relationship between the observed hourly SPM and NO x concentrations. There is a very good linear correlation between the two concentrations. In another paper (Tian J. and Chen D.) developed a semi-empirical model to predict hourly ground-level fine particulate matter (PM2.5) concentration in southern Ontario. The model is able to explain 65% of the variability in ground-level PM2.5 concentration. The model-predicted values of PM2.5 mass concentration are highly correlated with the actual observations. The root-mean-square error of the model is 6.1 μg/m³. HoermannS et.al has done an empirical analysis on particulate matter PM10 in Graz. They developed two models, prediction model and regression model. An empirical model to predict suspended particulate matter from lakes is presented by Lindstrom.M. et al. It predicts lake typical SPMvalues from lake total phosphorous concentration (TP).The model is shown to be stable and can be very useful in predictive lake modeling.

Methodology
This study has been undertaken to review the air quality of two coal mines and to develop an empirical model to evaluate SPM concentration from ambient NO x concentrations and SO 2 concentrations. One is Dhanbad colliery area Fig (1) and the other one is Magadh open cast mine Fig (2). The empirical methods are based on cross correlation of measured air quality data. These methods are reasonably reliable for predicting average SPM concentration. Dhanbad already has a network of continuous monitoring stations.
The area of study, Jharia coal fields is located in the heart of Dhanbad district in Jharkhand. Jharia encompasses an area of 9077.15 hectares and supports a population of 426415. Jharia coal fields are one among the few sources of prime coking coal in India. Mining is the most dominant industrial activity producing 24 million tons of coal every year. The coal mines studied included both open cast and underground mines. The major activities causing pollution are excavation works, explosion and transportation of coal. The major pollutants are SPM, sulphur dioxide and nitrogen oxides. The coal produced from this place is important for many heavy industries like iron &steel, power generation etc. As a result there is an increased production year after year.
During all these years due to mining and allied activities, air pollution has taken its toll on the people and environment so much that even an hour outside will result in stains all over the clothes. It has also resulted in increased suffering and respiratory problems mainly asthma, nausea, inflammation of respiratory tracts, deposition of dust in the lungs and eye irritation.  The two types of sources that have impact on the air quality are mining sources and non-mining sources. The activities associated with mining which generate pollution are drilling, blasting, coal crushing, coal dumps, overburden dumps, coal transportation and coal loading on wagons. The main pollutants emitted from all above operations are particulate matter. The major non-mining activities contribute to air pollution are road and rail traffic, other industries like fire brick, coke manufacturing units and burning of fuel for domestic use.
Data from various monitoring stations around the colliery area were collected. The data was collected from the area with different topographic conditions to get a true set of varied results, which would give representative results. The data collected consists of concentration of SPM, NO x and SO 2 by ambient air sampling.
The area under study was divided into two parts, part A and part B. Linear relationships have been developed between observed hourly SPM and NO x and SPM and SO 2 concentrations for each part individually and for whole area based on monitoring network. These linear relationships are then used to evaluate the coefficients of the linear equation.     Correlations obtained are summarized in Table 1 and Table 2 Dhanbad Colliery

SPM Concentration by Gaussian-Plume Method
Meteorological data during the above period are collected for Dhanbad colliery and Magadh opencast mines.
The meteorological data collected are wind speed, temperature, cloud cover etc. The concentration of dust due to mining activities is calculated using Gaussian-plume equation ( Hanadi.S.et al). The general Gaussian -plume equation is where C = Concentration of the pollutant (g/m 3 ) Q = Emission rate (gm/sec) σ y , σ z = dispersion coefficient (m) u = wind speed (m/s) x, y, z = distances from the source in three planes (m) h = height of plume (m) As the site selected is a coalmine, sources are considered to be located on level ground.
Hence, h = 0 Therefore concentration is calculated using equation given below

Results and Discussions
The general equation for Dhanbad coal area can be summarized as follows A comparison is made between the concentrations obtained from the field using high volume samplers and concentration calculated using the empirical formulae. There is only 10% variation between the observed values and the values predicted by the empirical formulae. The comparisons between the two values for Dhanbad and Magadh mines are shown in Table 3 and Table 4.Comparison is also made between concentration of SPM calculated by Gaussian Plume method, empirical formulae and measured by high volume samplers. (Table 5 & Table 6).The results do not vary much.