Temporal trends in ambient fine particulate matter and the impacts of COVID-19 on this pollutant in Grenada, West Indies

Figures & data

Figure 1. Geographical locations of the five PurpleAir monitors that were installed on Grenada and Carriacou.

Figure 2. Daily mean PM_2.5 concentrations averaged across the five PurpleAir monitors installed in Grenada and Carriacou from January 7 to December 31, 2020.

Figure 3. Boxplot comparison of hourly PM_2.5 concentrations at a rural location (orange) and an urban location (blue) on weekdays, by time of day. Time period of data: January 30 to February 28, 2020 and April 27 to August 31, 2020.

Figure 4. A box plot comparison of daily mean PM_2.5 concentrations on Saharan dust days and non-dust days in Grenada and Carriacou from January 7 to December 31, 2020.

Table 1. Results from fitting a multivariate linear regression model for daily concentrations of PM_2.5 in the presence of public health measures, and meteorological factors, from January 6 to December 31, 2020, in Grenada, West Indies.

	PM2.5 based on 4 Grenada monitors^1				PM2.5 based on all 5 monitors^2
Variable	Parameter estimate				Parameter estimate
	β	SE(β)	Sum Sq	p-value	β	SE(β)	Sum Sq	p-value
Presence of public health measures (Yes vs No)	−1.189	0.383	64.47	0.002	−1.148	0.387	68.83	0.003
Daily mean temperature (in Celsius)	0.487	0.155	41.10	0.001	0.467	0.150	36.29	0.002
Daily mean relative humidity (%)	−0.064	0.030	11.74	0.037	−0.072	0.031	15.72	0.019
Saharan Dust Day(Yes vs No)	4.570	0.346	974.23	<0.001	4.932	0.349	1134.26	<0.001
Residuals	-	-	1982.14	-	-	-	2019.82	-

¹The adjusted R² for this regression model was 0.35.

²The adjusted R² for this regression model was 0.38.

Table 2. Descriptive statistics of daily meteorological measures during Saharan dust days and non-dust days.

Daily mean environmental variable	Mean	SD	Min.	1^st Quartile	Median	3^rd Quartile	Max.
Saharan dust day (56 days)
Visibility (km)	13.4	2.4	3.4	12.6	14.2	14.8	17.4
Wind Speed (m/s)	6.8	1.5	3.1	5.9	6.9	7.8	10.3
Atmospheric Pressure (mbs)	1013.7	1.6	1009.7	1012.6	1013.8	1015.0	1016.7
Relative Humidity (%)	79.0	5.3	55.6	75.7	78.9	82.0	89.4
Precipitation (mm)	4.3	8.8	0.0	0.0	0.2	3.3	42.5
Temperature (Celsius)	27.5	1.3	22.0	26.8	27.8	28.5	29.2
Non-dust day (310 days)
Visibility (km)	20.5	3.1	14.2	18.0	20.3	22.6	28.8
Wind Speed (m/s)	5.5	1.7	0.9	4.2	5.7	6.9	8.9
Atmospheric Pressure (mbs)	1013.1	1.7	1008.7	1011.9	1013.2	1014.4	1016.6
Relative Humidity (%)	78.5	4.2	67.7	75.6	78.5	81.5	90.4
Precipitation (mm)	2.2	5.2	0.0	0.0	0.0	1.8	46.0
Temperature (Celsius)	27.8	1.0	24.6	27.1	27.8	28.5	30.3

Data availability statement

PurpleAir data are freely available online on their website. All enquiries about accessing additional data should be directed toward the corresponding author.