Air monitoring

Under the National Air Monitoring Programme (NAMP) there are four monitoring stations in Nagaland i.e. two stations at Dimapur and two stations at Kohima. Under this programme four air pollutants are monitored and analyzed viz., Nitrogen dioxide (NO2), Sulphur dioxide (SO2), Respirable Suspended Particulate Matter (RSPM) and Suspended Particulate Matter (SPM). The monitoring of pollutants is carried out for 24 hours (4 hourly sampling for gaseous pollutants (NO2 & SO2) and 8 hourly sampling for particulate matter (RSPM & SPM)) twice in a week.

The Nagaland Pollution Control Board regularly monitors ambient air quality of Dimapur and Kohima city throughout the year using manually operated Respirable Dust Samplers. The data generated in the NAMP stations are uploaded in the Environmental Data Bank of the Central Pollution Control Board.

The readings and data comparison of Dimapur and Kohima NAMP stations for the year 2012 are discussed in the following paragraph given below.

  1. Ambient Air Quality of Dimapur City:

The Board has been regularly monitoring air quality under NAMP at two stations (Bank colony (317) & Dhobinala (448) in Dimapur. The parameters which are monitored are Respirable Suspended Particulate Matter (RSPM), Suspended Particulate Matter (SPM), Nitrogen Dioxide and Sulphur dioxide. The gaseous pollutants i.e. Nitrogen dioxide (NO2) and Sulphur dioxide (SO2) are within the national standards in both the stations.

Table 1:   The monthly average concentration and Annual Average of particulate matters (RSPM & SPM) for both the stations i.e. Dhobinala (448) and Bank colony (317) for the year 2014

Sl. no Months for the year 2014 Bank Colony (317) Dhobinala (448)
RSPM SPM RSPM SPM
1 January 221 335 296 459
2 February 165 262 205 365
3 March 134 228 218 418
4 April 133 320 240 441
5 May 73 144 130 230
6 June 42 69 82 193
7 July 36 71 67 148
8 August 38 68 64 123
9 September 48 78 69 136
10 October 101 177 132 276
11 November 146 209 184 359
12 December 196 277 214 392
  Annual Average 111 186 158 295

A graph illustrating the average concentration of Respirable Suspended Particulate Matter (RSPM) and Suspended Particulate Matter (SPM) for both the stations is shown below:

Air-monitoring-graph

The average concentration (24 hourly) of RSPM is highest in the month of January in both the stations i.e. Bank Colony (317) with 221 µg/m3 and Dhobinala (448) with 296 µg/m3. The lowest reading of RSPM is recorded in the month of July with 36 µg/m3 for Bank Colony and 64 µg/m3 in August for Dhobinala station respectively.

Air-monitoring-graph2

The average concentration (24 hourly) of SPM is highest in the month of January in both the stations with 335 µg/m3 in Bank Colony (317) station and 459 µg/m3 in Dhobinala (448) station while the lowest reading of SPM is recorded in the month of August for both the stations with 68 µg/m3 in Bank Colony (317) station and 123 µg/m3 in Dhobinala station (448) respectively. The particulate matter (RSPM & SPM) is higher in Dhobinala (448) station compared to Bank colony (317) station.

1.1 Annual Average Concentration:

The annual average concentration of Particulate Matter (RSPM and SPM) at the two monitoring stations is illustrated in the table given below.

Table 2:      Comparison values of Annual Average Concentration of Particulate Matter (RSPM and SPM) for both the stations i.e. Bank Colony (317) and Dhobinala (448) for the consecutive years 2011, 2012, 2013 and 2014.

 

Years Bank Colony (317) Dhobinala (448)
RSPM SPM RSPM SPM
2011 80 128 98 202
2012 76 130 95 199
2013 89 156 116 254
2014 111 186 158 295

The trend analysis of particulate matter in the city for the past four years (2011, 2012, 2013 and 2014) shows an increasing pattern.

 

The table above represented shows that the levels of RSPM for both the two monitoring stations exceeded the prescribed NAAQS (National Ambient Air Quality Standard) of 60 µg/m3 (Annual).

In the case of SPM, it also shows data exceeding the prescribed standard of 140 µg/m3 (Annual) in station located Dhobinala (448), whereas it shows below the prescribed standard in the station located at Bank Colony (317) for the year 2011 and 2012, however, in the following year 2013 and 2014 it showed an increased beyond the permissible limits.

The annual average value for both the RSPM and SPM in the year 2014 is higher than that compared with the past 3 years in both the stations.

The annual average concentration of Particulate Matter (RSPM and SPM) at the two monitoring stations is illustrated in the graph given below.

Air-monitoring-graph3

Air-monitoring-graph4

The annual average value for RSPM and SPM in 2014 is higher than that all the preceding years in both the stations. The RSPM and SPM values also exceed the National Ambient Air Quality Standard in both the cases.

 

  1. Ambient Air Quality of Kohima City:

Under the National Air Monitoring Programme (NAMP) there are two permanent monitoring stations in Kohima, it is located Opposite NST office (609) and Opposite War Cemetery (610)

Table 3:    The monthly average concentration of Particulate Matter (RSPM and SPM) for both the stations i.e. Opposite N.S.T office (609) and Opposite War Cemetery (610).

 

Sl. no Months for the year 2014 Opp. NST office

(609)

Opp. War Cemetery (610)
RSPM SPM RSPM SPM
1 January 87 151 127 273
2 February 84 144 131 277
3 March 88 154 133 294
4 April 84 155 118 246
5 May 64 127 122 270
6 June 42 84 94 222
7 July 44 92 86 187
8 August 44 106 74 158
9 September 50 110 91 192
10 October 66 163 119 285
11 November 86 184 122 276
12 December 109 231 139 335

 

A graph illustrating the average concentration of Respirable Suspended Particulate Matter (RSPM) for both the stations i.e. opposite N.S.T office (609) and Opposite War cemetery (610) is shown below:

Air-monitoring-graph5

The concentration values of Respirable Suspended Particulate Matter (RSPM) was recorded highest during the month of December for both the stations with a value of 109 µg/m3 in station Opposite NST Office and 139 µg/m3 in station Opp. War Cemetery (610).

The average concentration of Suspended Particulate Matter (SPM) for both the stations i.e. Opposite N.S.T office (609) and Opposite War cemetery (610), are also illustrated in the graph shown below:

Air-monitoring-graph6

The concentration value of Suspended Particulate Matter (SPM) was also recorded highest during the month of December for both the stations Opposite N.S.T office (609) and Opposite War Cemetery (610) with values of 231 µg/m3 and 335 µg/m3 respectively.

Analysis of air quality data of Kohima reveals that the major air pollution problem of the city is the presence of high level of RSPM particularly in station located Opposite War cemetery. This is a real concern as exposure to high level of RSPM is reported to be associated with increased morbidity and mortality in the exposed population. The air quality data also indicates that the air pollution becomes more serious during the winter months.

The gaseous parameters i.e. Nitrogen Dioxide (NO2) and Sulphur Dioxide (SO2) are within the permissible limits for both the stations i.e. Opp. N.S.T office (609) and opposite War Cemetery (610).

 2.1 Annual Average Concentration:

The annual average concentration of Particulate Matter (RSPM and SPM) at the two monitoring stations is illustrated in the table given below.

 

Table 4:      Comparison values of Annual Average Concentration of Particulate Matter (RSPM and SPM) for both the stations i.e. opposite N.S.T office (609) and Opposite War cemetery (610) for the consecutive years 2011, 2012, 2013 and 2014.

Years Opp. NST office (609) Opp. War Cemetery (610)
RSPM SPM RSPM SPM
2011 62 106 92 195
2012 63 107 100 217
2013 66 128 104 238
2014 71 142 113 251

 

The trend analysis of particulate matter in the city for the past few years (2011, 2012, 2013 and 2013) shows an increasing pattern for both the monitoring stations.

The table above represented shows that the levels of RSPM for both the two monitoring stations exceeded the prescribed NAAQS (National Ambient Air Quality Standard) of 60 µg/m3 (Annual). However, station Opp. War Cemetery (610) shows data exceeding much higher that the station opposite N.S.T office (609).

In the case of SPM, it also shows data exceeding the prescribed standard of 140 µg/m3 (Annual) in station located Opp. War Cemetery (610), whereas it shows below the prescribed standard in the station Opposite N.S.T office (609), however, in the year 2014 it showed an increased with a value of 142 µg/m3.

The annual average concentration of Particulate Matter (RSPM and SPM) is represented in the graph given below:

Air-monitoring-graph7

Air-monitoring-graph8

An increasing trend of the particulate matters (RSPM and SPM) may be due to various factors such as bad roads conditions, vehicle movements/pedestrian, burning of waste, etc. The increasing influx of population, unorganized operating industries, besides the industries, emission from automobiles plying on city streets is increasing steadily without any major checks and improper waste management are also the cause behind the increasing air pollution level.

NATIONAL AMBIENT AIR QUALITY STANDARDS (2009)

Pollutants Time weighted average Concentration in Ambient Air
Industrial, Residential, Rural and Other Areas Ecologically Sensitive Area (notified by Central Government)
Sulphur Dioxide (SO2), µg/m3 Annual * 50 20
24 hours ** 80 80
Nitrogen Dioxide (NO2), µg/m3 Annual * 40 30
24 hours ** 80 80
Particulate Matter (Size less than 10µm) or PM10 , µg/m3 Annual * 60 60
24 hours ** 100 100
Suspended Particulate Matter (SPM), µg/m3 Annual *     140*** 70
24 hours **     200*** 100

 

*    Annual Arithmetic mean of minimum 104 measurements in a year at a particular site taken twice a week 24 hourly at uniform intervals.
** 24 hourly or 8 hourly or 1 hourly monitored values, as applicable, shall be complied with 98 % of the time in a year.2% of the time, they may exceed the limits but not on two consecutive days of monitoring.
*** The values under industrial area for Suspended Particulate Matter (SPM) is 360 µg/m3 (Annual Average) and 500 µg/m3 (24 Hourly)