Runoff water and sediment from impervious surfaces in urban areas (roads, parking lots, roofs) carry a variety of pollutants, including heavy metals such as lead, zinc, cadmium and copper. Urban surface water commonly contains hydrocarbon compounds from oil, grease and fuels deposited on streets. It also may contain hazardous household and industrial wastes such as oils, paint thinners, organic preservatives and solvents.

Landscape and turfgrass areas catch and filter polluted runoff water that does not enter storm sewers, especially if proper landscape designs are used. Turfgrass traps the water in its porous yet dense biomass of shoots and roots.

Turfgrass is a dynamic ecosystem. Its biomass contains microscopic bacteria, fungi and actinomycetes as well as earthworms and other invertebrates (insects, gastropods, nematodes, spiders, mites).

As the leaves, stems and roots of grasses in the upper layers of the soil decompose/ they produce nutrients that support a large and diverse population of organisms. Microorganisms that thrive in the turfgrass ecosystem make up one of the most active biological systems for the degradation of trapped organic chemicals and pollutants. Grasslands have more of these organisms than cropland or forests. Mowed turfgrasses are likely to have even higher levels of these beneficial microorganisms because of the nutrients available from clippings (if they are returned and not collected) and the moisture available through irrigation.