COVID-19: A Spectio-temporal analysis of Air quality status in Coking Coalfields of India due to nationwide lockdown in India

A novel infectious corona virus disease (COVID-19) was identified in the month of December 2019. It has now been announced as a worldwide pandemic by theWorld Health Organization. COVID-19 pandemic has positive impacts on the environmental pollutants. Inpresentwork,Coalfield areas of JhariaCoalfields (JCF), India have been takenas a case study to evaluate the effect of the lockdown on air quality at 10 locations. This study had been selected to estimate the reduction in concentration of pollutants like PM10, PM2.5, SO2, andNOx during 3 Seasons (summer, Post-Monsoon andwinter season) in the year 2019 in comparison to the concentration during the lockdown period i.e. from April 2020 to June 2020. The study areas selected was as fire affected and non-fire affected areas of Jharia Coalfield to identify the contribution of pollutants in the mining area to establish the baseline concentration of Business as usual (BAU) vs. the lockdown condition. The average reduction in concentration of PM10, PM2.5, SO2 and NOx was observed as 18%, 14%, 22% and 26% respectively during the lockdown period in comparison with the annual average concentration. As observed, the AQI value at the selected monitoring sites in JCF was 1.5 times higher in comparison to the lockdown period. This study will provide the confidence to the regulatory body for strict implementation of the applicable air quality standard/policies in the mining areas. The study will also provide confidence to the regulatory body in making emission control strategies for improvement of environmental conditions and human health.


Introduction
D ue to the spread of a novel contagious infection of the coronavirus (COVID- 19) entire world is going through a very stressful situation [1]. World Health Organization (WHO) has declared COVID-19 as a 'global pandemic' on 11 March 2020. First case of COVID-19 in India was reported in Kerala on 30th January 2020. As the number of COVID-19 cases increased to 500, Honourable Prime Minister of India asked nationwide Janta (Public) Curfew across India on 22nd March 2020. Followed by this, nationwide lockdown was declared from 25th March 2020 in different phases. The first phase of lockdown was from 25th March to 14th April 2020, second phase was from 15th April 2020 to 3rd May 2020, the 3rd phase was from 4th May to 17th May 2020 and the fourth phase was from 18th May to 31st May 2020.
During the lockdown, social gathering was prohibited. Shopping complexes, school/colleges, educational institutes, restaurants and cinema halls were fully closed. Employees were asked to work from home. Transportation services including Railways, Air and road were suspended except essential services. Hence, the lockdown led to minimum human activities on the road and around the study area. Though, the lockdown has affected economy of the country, but this helped in reduction of air pollution level across the country.
Coal Mining activities are always blamed for degradation of Air Quality Status of its surrounding [2]. COVID-19 has given an opportunity to assess pollution load in the mining areas due to mining activities.
This study will provide the baseline condition of the air pollution condition of the coal mining area. This study will provide the confidence to the regulatory body for strict implementation of the applicable air quality standard/policies in the mining areas. The study will also provide confidence to the regulatory body in making emission control strategies for improvement of environmental conditions and human health. The data from study may also be utilized for Validation of Air Quality Models currently being used for Air Quality Impact Prediction (AQIP) in the coalfield areas.
India is falling in the in the list of developing nations of the world. India is the world's largest producer of coal after China. The share of coal has increased in energy mix as well as the power mix in India. Coal provided 44% of the total primary energy supply (TPES) and 74% of electricity generation [21]. India has abundant coal reserve [2]. Coal mining come under essential services, the only measure activity was coal mining in the study area.
This present study had been commenced for assessment the ambient air quality like PM 10 , PM 2.5 , SO 2 and NOx during three seasons of the previous year i.e. summer, post-monsoon and winter and during the lockdown period i.e. from April 2020 to June 2020.
This study had been undertaken for assessment of ambient air quality among the mine fire-affected and non-mine fire affected coal mining areas of JCF to identify the contribution of pollutants in the mining area for comparison of Business as usual (BAU) and during the lockdown period to establish the baseline concentration of BAU vs. the lockdown condition.
This study will be beneficial for the policy maker for reviewing pollution standard in mining areas for implementation of better mitigation measures.

Location of the study area
Jharia Coalfield contributes to the Indian economy as it provides metallurgical coal as well as thermal coal to steel and power sectors respectively. It provides infrastructural input to many core industries and powerhouses.
As per the coal mining history of India, it was supposed to be the smartest and profitable area for mining as it has the highest concentration of thick coal seams at relatively shallow depths. In India only JCF is having known reserves of prime coking coal in India and meets a sizeable proportion of coking coal required by the steel industry.
The Jharia coalfield, located in Damodar valley region covering an area of 453 sq. km is sickleshaped and morph tectonically represents halfgraben configuration with its southern boundary marked by basin margin fault [3]. It is bounded by the latitudes 23 36 0 e23 48 0 N and the longitudes 86 07 0 e87 29 0 E. JCF is spread in 38 km (length) and 17 km width ( Fig. 1 (a), (b)).
The study area falls under tropical climate and is characterized by very hot summer and cold winters. The months of May and June are very hot. The average temperature of the study area was varying from 20 C to 40 C during the study period. The wettest month (with the highest rainfall) was July (342 mm) and driest month (with the lowest rainfall) is December (5 mm). The area receives annual rainfall of about 1140e1700 mm.
Predominant wind direction was from the southwest during the study period. As the wind rose diagram indicates, the percentage of calm condition was 8.76%.

Study area and its monitoring locations
Air quality monitoring stations were selected at nine locations predominantly affected areas due to mining activities based on coal mine fire and nonfine areas [4,5].
Coal mining in Jharia coalfields is very difficult due to the problem of mine fire and subsidence. In JCF, shallow depth coal seams of good quality were mined out unscientifically. Mining activities were functioned within small leaseholds. In the old days, when the surface was not densely populated, the mine operators used to extract as much coal as possible in the upper coal horizons without stowing or supporting.
The mine fires occurs due to spontaneous heating of the coal through two interconnected processes between oxygen coal contact or oxidation process and the thermal process. The fire spreads and reaches in the strata. About 10% of total national coal resources are in the fire-affected areas [2]. This unscientific mining in the area leads to coal mine fire, caused severe air pollution in the area.
To study background concentration level Monitoring at Koyla Nagar, Dhnabad campus was also done for the same period. The details of monitoring stations along with latitude-longitude and source of air pollution have been presented in the Table 1.

Monitoring
The monitoring sites (Table 1) had been selected by considering predominant wind direction and area affected by mine fire to give an actual picture. The air quality monitoring had been done in three seasons summer, post-monsoon and winter for the previous year 2019 and again during lockdown period i.e. from April 2020 to June 2020. Monitoring in the selected areas was completed twice in a week (for 24 h) at the uniform intervals ( Table 2).    The particulate matter concentration is affected by the mechanism of dispersion of pollutant, topography of the monitoring areas along with meteorological parameters [9]. The particulate matter in the winter season near the pollution sources remains concentrated. Due to lower temperatures and wind speed, the particulate matter does not disperse to a greater distance. In the summer season, due to higher wind speed and dispersion of particulate matter lower atmospheric pollutants were observed. During post-monsoon season, the lower pollution level was observed due to higher relative humidity. In this season, the particulate matter washed out by precipitation, causing the lowest concentration level.

Results and discussion
Spatial distribution of particulate pollutants concentration observed at different monitoring stations have been drawn. There were significant variations in the concentration level at all the monitoring sites selected among JCF.
Air quality of reference site, Koyla Nagar colony (L-10) was observed as a satisfactory level because it was far away from mining and its allied activities.   Koyla Nagar colony is surrounded by Green Belt and is free from any polluting sources. Hence, the pollutants levels observed were minimum in all three seasons. All sites except the at Koyla Nagar (L-10) (reference site) indicated a much higher concentration of gaseous pollutants than the NAQQS (2009) permissible limit in the prelockdown situation.
Average Among the selected monitoring stations, concentration at NT/ST Expan. OCP was found the highest concentration of gaseous pollutants (SO 2 and NO x ) during the entire monitoring period [10]. It was because of the existence of coal mines nearby the site which were highly affected by coal mine fire. , were present nearby to mines fire affected area. These sites showed higher level of gaseous pollutants (SO 2 and NO x ) which badly polluted the ambient air quality. In monitored coal mines, sulphur rich coal discharges sulphur dioxide after the combustion. The coke-oven plants also discharge incompletely oxidized nitrogen dioxide. Due to this monitoring stations like, Lohapatty OC, Tetulmari, Bastacolla, Damoda, Murulidih 20 and 21 pits and Jogidih Colliery showed higher concentration. Hence, the production of higher levels of SO 2 and NOx was a sign of the greater level of pollution in the areas under coal mine fire [16]. The concentration levels of gaseous pollutants were higher at all monitoring sites in winter in comparison with the seasons like summer and post-monsoon. It was due to the lower atmospheric dispersion of pollutants concentrations during the winter seasons [11,12].
The Jharia Coalfields falling under a tropical climatic pattern with temperature lower along with lower sunlight and lower wind speed (on an average 2 km/h) during winter season. This causes very poor dispersion of pollutants in the areas. Hence concentration level of NOx was highest in winter in comparison with seasons like summer and postmonsoon. Raised levels of NO x in six monitoring sites may also be endorsed due to the incident like active coal mine fire, vehicular movement and other mining and allied activities [13,14]. Spatial distribution of the average concentration levels of pollutants like PM 10 , PM 2.5 , SO 2 and NOx are depicted in Fig. 3 [2,15].

Pollutant concentration levels during the lockdown period
During lock down period the average PM 10  It was observed that there was a significant reduction of pollutant levels at all the monitoring stations in comparison with the Annual Average (BAU), Summer-2019 and during Lock-down period at ten monitoring sites of JCF. This reduction was due to the decreased human activities in the area other than mining activities.
Comparative Concentration level of PM 10 , PM 2.5 , SO 2 and NOx between annual Average (BAU), Summer-2019 and during the lockdown period at ten monitoring sites of JCF has been shown in the Fig. 5.
Comparative reduction of concentration levels (%) w.r.t. annual average (BAU) vs. annual average at all the monitoring sites have been executed, the same has been shown in the table no. 3. It has been observed that there was a significant reduction in all the four parameters like PM 10 , PM 2.5 , SO 2 and NOx.
The average reduction in concentration of PM 10 , PM 2.5 , SO 2 and NOx was observed as 18%, 14%, 22% and 26% respectively during the lockdown period in comparison with the annual average concentration (see Table 3).
The graphical representation of the % reduction has been shown in the Fig. 6.

Air quality index
Data generated after monitoring at different monitoring stations does not represent air quality status to the common public, scientific community and policy makers. Hence to represent the air quality in a single number (AQI index value), air quality index (AQI) is a very important tool.
To compare air quality status of the study area in the pre-lockdown (BAU) and lockdown period AQI for all the monitoring stations have been calculated and represented in the Table 4. AQI of the monitoring stations have calculated by using National Air Quality Index guidelines provided by Central Pollution Control Board (CPCB), Government of India [8].
AQI converts complex air quality data of the pollutants into a single number (index value) and a specific color code gives information on air quality and its connected health impacts, which can be understood by a common people. The pollutant concentration (Ip) values were calculated and the  maximum Ip values were taken as the AQI of the site monitored according to the formula: where I P is the sub-index, B HI is the breakpoint concentration greater than or equal to the concentration given, B LO is the breakpoint concentration less than or equal to the concentration given, I HI is where P ¼ 1, 2, …, n denotes n pollutants. AQI were calculated by using the formula prescribed by CPCB (2014) for all the ten selected monitoring stations (Fig. 7). AQI values in the prelockdown varies from minimum 95 to maximum 328 and during the lockdown it was varying from minimum 97 to maximum 309. As shown in the table no. 3 the AQI values in the monitoring location falling in the mine fire affected area was observed in the very poor category. However, it has been noted that during the lockdown period the AQI value observed was in the poor category. Further, it is observed that in the reference site (L-10), AQI value was in the satisfactory category in both the period of monitoring i.e. in BAU vs. the lockdown period.
The reason of monitoring areas falling in the category very poor, it was due to burning of coal, road transportation of the coal and insufficient burning of coal in the exposed coal seams and over burden (OB) of the mining areas.
As observed, the air quality of the monitoring station at Koyla Nagar (L-10) comes under satisfactory level, as this location does not attract any mining and its allied activities.
As observed (Fig. 7) the AQI of the monitoring area shows the overall image of the Jharia Coalfields with pollution load in the coal capital of India.

Conclusions
COVID-19 has created a severe threat to the population on the earth. It has affected the world economy. However, the COVID-19 has some positive impact on air pollution reduction of the glove due to the implementation of national lockdown since 25th March 2020 [18e20]. The present study has shown the comparative status of the pollutants in the selected study area in the pre-lockdown situation (BAU) and during the lockdown. It was observed that there was a significant reduction of pollutant levels at all the monitoring stations in comparison with the Annual Average (BAU), Summer-2019 and during the lockdown period at ten monitoring sites of JCF. The average reduction in concentration of PM 10 , PM 2.5 , SO 2 and NOx was observed as 18%, 14%, 22% and 26% respectively during the lockdown period in comparison with the annual average concentration. This reduction was due to the decreased human activities in the area other than mining activities. As observed, the AQI value at the selected monitoring sites in JCF was 1.5 times higher than the in comparison to the lockdown period. This study will provide the baseline condition of the air pollution condition of the coal mining area. This study will provide the confidence to the regulatory body for strict implementation of the applicable air quality standards/policies in the mining areas. The study will also provide confidence to the regulatory body in making emission control strategies for the improvement of environmental conditions and human health. The data from study may also be utilized for Validation of Air quality Models currently being used for Air quality Impact Prediction (AQIP) in the coalfield areas.

Ethical statement
The authors state that the research was conducted according to ethical standards.

Funding body
None.

Conflicts of interest
None declared.
Appendix A. Supplementary Data.