The bar chart compares the average daily minimum and maximum concentrations of two air pollutants, SO2 and N2O in 4 cities is Los Angeles, Calcutta, Beijing, and Mexico in 2000, measured in micrograms per cubic metre.
Looking at the illustrations, it is immediately evident that Mexico city recorded the highest pollution levels for both gases, whereas the opposite was true for Los Angeles with the lowest SO2 figures but high N2O levels. In most cities, maximum levels were significantly higher than minimum ones, indicating considerable daily fluctuation.
Looking at sulphur dioxide (SO₂), Mexico City had the highest levels among the four cities. The minimum figure was 80 micrograms per cubic metre, and the maximum reached 200, showing a large increase during the day. Beijing also had a big difference between its minimum and maximum levels, rising from 25 to 100. Calcutta’s SO₂ levels were lower and more stable, ranging from 47 to 59. Los Angeles recorded the lowest amounts overall, with figures between only 2 and 10, which were much lower than those in the other cities.
Regarding nitrous oxide (N2O), Mexico City again recorded the highest levels. The minimum concentration was 113 micrograms per cubic metre, and the maximum rose to 207, making it the most polluted city for this gas. Los Angeles also had relatively high N2O figures compared to its SO2 levels, increasing from 39 to 104. In contrast, Calcutta and Beijing showed lower levels of N2O. Calcutta’s figures ranged from 30 to 52, while Beijing recorded the lowest minimum level of 14 and a maximum of 54.
In conclusion, Mexico City had the highest pollution levels for both gases in 2000, while Los Angeles recorded the lowest SO₂ levels. Calcutta and Beijing showed moderate figures in comparison. The chart clearly highlights noticeable differences in air quality among the four cities.