Atlanta, Georgia
About Atlanta
In 2020, the city had a population of 498,715 people, making it the 38th most populous city in the US. The median household income was approximately 83K USD, higher than both the state of Georgia and the national median.
However, the city has a poverty rate of 17.3%, higher than the state and national median, notably of people of color and under 18 years old.
Urban Heat Island
Atlanta temperature has been rising, and is getting between 0.8 and 2.5 degrees warmer than in surrounding areas ( Muse et al., 2022 ). This effect is called Urban Heat Island and appears when the land used in a city changes from forests and vegetation to urban constructions like residential areas, roads and concrete buildings.
Without vegetation or bodies of water, more heat is absorbed and emitted by concrete buildings and roads. We can simulate Atlanta's situation with or without urbanization where we can see that there is almost a 4° difference at day.
To the left we see the temperature at 2 meters with the effect of buildings and roads, and to the right the situation if we removed all of the urban spaces.
The map shows that the heat severity hits lower income and people of color communities. Nevertheless, the people of Atlanta took matters into their own hands and formed an organization to study the heat island in their area.
UrbanHeatATL is an interdisciplinary collaboration between scientists and the community where volunteers receive temperature sensors to map heat anomalies in their locality on a weekly basis.
Analyses show that heat island management strategies would have a positive effect on low-income and mostly communities of color ( Vargo et al., 2016 )
Nitrogen Oxides Emissions
The NOx emissions were provided by the CAMS-GLOB-ANT v6.2 inventory, that is developed as part of the Copernicus Atmosphere Monitoring Service (CAMS; https://doi.org/10.24380/eets-qd81, Soulie et al., 2023).
The spatial distribution of the emissions fluxes (in kg/m2/s)
The NOx emissions of the major city Atlanta can be identified, where higher emissions occurred over Atlanta city , and less activities are seen in the region surrounding the city. In addition, other areas appear noisier, which could be related to road transportation emissions in the main highways of the Georgia state.
The time series for NOx emissions over Atlanta
We observed an overall negative trend in this 23-year time period, indicating a decreasing temporal pattern in emissions (p-value < 0.05 according Mann-Kendall test) of -0.3064099Mg/month (~ -300 kg/month; according to Sen's slope test). Also, the highest decrease was observed in the year 2020, possibly related to the social isolation measures implemented during the COVID-19 pandemic.
The road transportation is the largest emission source of NOx, and also the sector with the highest decrease rate. This behavior suggests that the gradual decrease in emissions from road vehicles, linked to USA regulations, is the main driver for the NOx emission reduction.
The monthly mean based on the 23-year period for anthropogenic NOx emissions
The NOx emissions have a seasonal maximum in the winter (December–February). Monthly mean values of anthropogenic emissions of NOx from residential and commercial sectors has the same pattern, while emissions of NOx from road transportation is relatively constant throughout the year, with lower emissions in the winter.
Concentration Distribution
The NO 2 concentration distribution.
This map shows the distribution of nitrogen dioxide (NO 2 ) concentration in Georgia. Overall, there is an uneven distribution of NO 2 between the northern and southern parts of the state. The area around Atlanta is shown in darker colors, indicating relatively high NO 2 concentrations, close to 25-30 ppb. Atlanta is one of the regions with higher NO 2 concentrations. The high concentration areas in Atlanta are concentrated in the city center and around major transportation routes, where there is heavy traffic and more NO 2 emissions. Additionally, the surrounding areas of Atlanta also show higher NO 2 concentrations, likely due to the dispersion of pollutants from the city.
The Ozone concentration distribution.
The map shows the ozone concentration distribution in Georgia. In the distribution of ozone concentration within the state, the northern part has significantly higher ozone concentrations compared to the southern part. The area around Atlanta has relatively high ozone concentrations. Atlanta is a major city in Georgia, with a dense population and frequent industrial activity, which may contribute to the higher ozone concentration in this area.
Population Exposure
The population exposure distribution.
This map shows the distribution of the population exposed to ozone in Georgia. As expected, Atlanta and its surrounding areas are shown in darker colors, indicating a relatively higher number of people exposed to ozone. As the main city in Georgia, Atlanta has a dense population, resulting in a larger number of people exposed to ozone pollution. The population exposure is particularly severe in the city center and around major transportation routes, where there is heavy traffic, frequent industrial activity, and high pollutant emissions.
Concentration Trends
Monitoring data from the U.S. EPA shows decreasing trends of both ozone and PM2.5 in Atlanta over last several decades.
We find differing trends among ozone precursors, with sharp decreases in mixing ratios of nitrogen oxides over the last few decades and a slight increasing trend measured isoprene mixing ratios. The reason for the increasing isoprene trend remains unclear and is possibly temperature related.
Photo of the U.S. EPA South DeKalb site courtesy of https://ascent.research.gatech.edu/south-dekalb
However, the U.S. EPA monitoring site is located outside of downtown Atlanta, GA and it is unclear whether trends captured by the single U.S. EPA site reflect trends across Atlanta.
Purple Air Monitors
How does the EPA monitoring site compare to PM2.5 within the city of Atlanta?
EPA monitors are designed to capture regional background concentrations of air pollution. Here, we compared reference-grade PM2.5 measurements from the EPA monitoring sites to PM2.5 from a Purple Air monitor situated closer to Downtown Atlanta.
As expected, PM2.5 readings from the Purple Air monitor are higher than from the background EPA monitoring site. However, the two sites show surprisingly similar day-to-day variations even though they located are 16km away. This suggests that the drivers of day-to-day variability could be regional in nature.
Where are Purple Air monitors located in Atlanta?
Location of Purple Air Monitors compared to Race and Hispanic Origin demographics.
Finally, we assess inequities in PurpleAir sensor distribution and find that PurpleAir sensors in Atlanta are disproportionately located in white neighborhoods, revealing critical gaps in our observing network.