In Hong Kong, green buffers around urban water-bodies were studied in order to investigate the environmental factors influencing the emission of greenhouse gases from rivers. The researchers, with the help of citizen scientists, compared the amount of available carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in 15 urban rivers in Hong Kong. Each river was subject to a different amount of pollution from its surrounding catchment. Citizen scientists took samples to determine the quantity of nutrient pollution and carbon present in each site. This information allowed researchers to examine the link between river catchment conditions, in particular the presence of green buffer areas, and the carbon emission of rivers and how this fluctuated with seasons.