Air quality

The OpenAQ platform gathers and shares open air quality data from around the world. 162 automatic monitoring stations are listed on OpenAQ for the UK with hourly NO₂ readings available over the last 90 days. Many of the stations also record levels of coarse and fine particulate matter (PM₁₀ and PM_2.5). This recipe will retrieve hourly mean NO₂ concentrations from the Manchester Piccadilly monitoring station and plot the results.

Ingredients

Data sources

OpenAQ

R packages

Air quality chart

Instructions

Load the necessary R packages.

library(ropenaq) ; library(ggplot2)

Retrieve all the cities with monitoring stations in the UK.

cities <- aq_cities(country = "GB")

Search for monitoring stations that record NO₂ levels in Manchester. Other available pollutants include “pm10” and “pm25” and values for the cityURL variable in the cities dataframe are used for the city name.

locations <- aq_locations(country = "GB", city = "Manchester", parameter = "no2")

Retrieve recent measurements of NO₂ from the Manchester Piccadilly monitoring station. If you want readings from a different monitoring station simply change the city and the location using values for the locationURL field in the locations dataframe.

readings <- aq_measurements(country = "GB", 
                            city = "Manchester", 
                            parameter = "no2",
                            location = "Manchester+Piccadilly")

Plot the hourly mean levels of NO₂ over the last 90 days and add a horizontal line indicating the legal limit.

ggplot() + 
  geom_line(data = readings, aes(x = dateLocal, y = value), 
            colour = "#c51b8a", size = 0.5) +
  geom_hline(aes(yintercept = 200), color = "#000000", size = 1) +
  annotate(geom = "text", x = as.POSIXct(Sys.Date()-5), y = 200, 
           label = "Legal limit (18 exceedances allowed)", fontface = "bold", vjust = 2) +
  scale_y_continuous(limits = c(0, 210), expand = c(0.005, 0.005)) +
  labs(x = "time (hours)",
       y = expression(paste(mu, "g/",m^3)),
       title = expression(paste("Hourly mean ", NO[2], " concentrations")),
       subtitle = paste("Manchester Piccadilly, last 90 days"),
       caption = "Source: DEFRA | openaq.org") +
  theme_minimal() +
  theme(plot.margin = unit(c(1,1,1,1), "cm"),
        panel.grid.major.x = element_blank(),
        panel.grid.minor = element_blank(),
        plot.title = element_text(size = 16, face = "bold"),
        axis.title.x = element_text(hjust = 1),
        axis.title.y = element_text(hjust = 1),
        plot.caption = element_text(size = 9, color = "grey50", hjust = 1, margin = margin(t = 15)))

Output the chart as a PNG file.

ggsave("air_quality.png", dpi = 300)