Extensive Greenroofs can typically remove about 50-60% phosphorous and 60-70% nitrogen from rainfall. Intensive greenroofs remove more pollutants and can uptake as much as 70% phosphorous and 80% nitrogen. The amount of pollution reduction is based on the depth of the soil, the time of year, and the type and number of plants installed. Extensive greenroofs do an excellent job of absorbing ground level ozone and CO2 and other airborne particulates and if 20% of the roofs in the D.C. were "greened" the pollutant reduction would be equivalent to the planting of over 100,000 trees.
