The interim report on particulate source apportionment study for air quality in Vasco conducted by IIT Bombay says that most of the air pollution is caused by the burning of biomass for water heating and cooking and also by coal handling at the Mormugao Port Trust.
A regulatory dispersion model called ‘AERMOD’ was used to study the extent of influence of the port activities on the study areas.
It was found that the strength of the source progressively reduces with distance from the port towards Vasco city.
The study, which started in February 2018, was conducted using handheld real-time instrument (TSI: DustTrak) for PM10 and PM2.5 at certain identified locations – residential, commercial, and mixed source locations, ‘B-Type’ buildings, the MPT colony, the commercial centre, the fish market, the Baina Residence Colony, the Sada Colony, Mangor Hill and the MPT Guesthouse.
Parameters were checked for three times in a day – in the morning (6 am to 10 am), afternoon (12 pm to 3 pm) and at evening (5 pm to 10 pm).
The report, which analyses historical data on particulate matter levels, says the levels at the MPT and in Vasco city are similar, adding that the strength of the pollutant source progressively reduces with distance from the port towards Vasco city, and large particles travel for a short distance from the source and therefore likely to be a local concern.
However further study (source apportionment based on chemical analysis) will be able to comment on such local sources, the interim report says.
“If the particulate matter at near source is ~10 μg/m3, then within 1 km towards Vasco it reduces to ~0.5 μg/m3. The PM10 at the MPT berth were measured as 128 μg/m3 to 452 μg/m3. If these were to be selected then it is expected that the contribution at 1 km would be 6.4 to 23 μg/m3, and at 2 km would be 1.28 to 5 μg/m3,” the report explains.
During the sampling period between May 1 and May 14, 2018, 24-hour samplings were carried out at the MPT Guesthouse, the fish market and Mangor Hill.
The study shows the concentration of PM10 at the fish market and Mangor Hill which was recorded between 60 μg/m3 and maximum 80 μg/m3 with a slight difference in readings between the two locations. Similarly, the PM2.5 during the same period between these two locations was also found comparable between 20-25 μg/m3 to maximum 35-40 μg/m3.
It had been expected that the concentrations at the fish market would be higher than Mangor Hill as the fish market is closer to the port. But the concentrations at the fish market were comparable to those at Mangor Hill, indicating that there are possible influences of other local sources.
Samples of PM10 were collected at the berths at a time when the Adani Group firm was handling coal, and JSW was handling limestone in December 2018.
The gravimetric analysis result on these measurements showed high level of PM10 concentration of 453 μg/m3 at the JSW unit which was more than the value of 305 μg/m3 recorded at the Adani plant.
To decide the sampling locations for the pre-monsoon sampling and assess the effect of port activities on air quality of Vasco, a dispersion model (AERMOD) was used. Meteorology data (MM5) were procured for the study purpose.
The PM2.5 concentrations were spatially similar throughout the loop locations, but varied with the time of the day. These were about 200 μg/m3 recorded in morning, 150 μg/m3 in afternoon and 100 μg/m3 in the evening.
The size distribution of particulate matter at the fish market, which was highest during daytime between 200-220 μg/m3, went down at evening.
Moreover, the temporal variation of PM2.5 at the MPT Guesthouse, the fish market and Mangor Hill sites using DustTrak measurements (averaged for 30-minute measurement) was found seeing the trend of PM2.5 at the fish market mostly during morning and nighttime.
Furthermore, the loop study measurements in residential areas of Sada Colony, Sasmolem, New Vaddem and A-type MPT building the morning concentrations were found to be higher than those in the afternoons and evenings.
The relative temporal and spatial variation of PM2.5 concentrations measured using DustTrak (average of 10-day measurements at the fish market and Mangor Hill and five-day measurements
at other locations) the concentration was found at all locations except the MPT Guesthouse: the morning concentrations were higher than afternoons and evenings.
The concentrations during mornings at Sada Colony location were higher compared to all other locations.
The study attributed the cause of the increased pollution to biomass burning for water heating and cooking in the morning.
The study revealed that CAAQMS data provided by the MPT for 2016-2018 for Adani and JSW sites, was erroneous and showed low concentration of PM10 and suggested for quality check.