This table shows nonpoint sources and pollutants associated with them. Source: (Adapted from The Stormwater Pollution Prevention Handbook, Conservation Toronto and Region, 2001).

Link to this table.

Factor Description Source
Soil texture Filtration is generally more effective in fine grained soils (i.e. silts and clays). This process is generally only significant when the average size of the pathogen is greater than 5% of the average pore space meaning protozoa and some bacteria may be removed this way but not viruses Karathanasis et al., 2007; Ginn et al., 2002
Soil cation exchange capacity The process by which the pathogen becomes attached to the soil particles. It is most effective with viruses and smaller bacteria. Adsorption generally increases as the clay content in the soil increases and increases as soil pH decreases. Bitton and Gerba, 1994; Lewis et al., 1980
Soil moisture content Moisture content appears to be one of the most influential factors in determining the survival time of pathogens. In general the survival time will increase as the moisture content increases. Beard, 1940; Kibby et al., 1987
Temperature In general, survival time increases as temperature decrease. McFeters and Stuart, 1972; Kibby et al., 1978
pH Survival time of pathogens appears greatest when soil is near neutral pH and decreases as the pH moves away from that range. McFeters and Stuart, 1972
Organic content The increased presence of organic content increases the survival time of pathogens, as well as allows for the potential for some re-growth. This may be due not only to the presence of available nutrients but also to the fact that organic matter has the ability to retain moisture. Lewis et al., 1980; Tate, 1978
Predation Microbial predators in the sub-surface reduce the concentration of pathogens in the soil and water (Tate, 1978). Tate, 1978

aRepresentative list only; many additional pollutants can be associated with most of the activities listed
bCombined sewers are very limited in Minnesota, with only a few remnants still existing in the metropolitan area. However, the same concerns apply for sewage spills and accidental overflows.