Pesticide properties include physical and chemical characteristics such as solubility, adsorption, volatility, and the potential for degradation, as discussed earlier. Pesticide chemicals that dissolve readily in water are highly soluble and, thus, are generally carried with the water flow. Such pesticides have a tendency to leach from the soil to groundwater. However, many pesticides do not leach because they are adsorbed on the soil particles or organic matter even though they may have a relatively high solubility. Highly volatile chemicals are easily lost to the atmosphere and are less likely to leach to groundwater unless they are also highly soluble and, thus, collected in water systems. Degradation affects the potential for a pesticide to reach groundwater. The persistence of the pesticide influences the potential for contamination. The longer the compound lasts before it is broken down, the longer it is subject to the forces of leaching. However, many highly persistent pesticides, such as the chlorinated hydrocarbons, have not been found in groundwater because of their low solubility and strong adsorption to soil particles. On the other hand, some pesticides of low persistence, such as aldicarb, have been found in groundwater. Table 1 lists the persistency of certain pesticides in soils. Information on other pesticides can be found on pesticide labels or through Environmental Protection Agency Fact Sheets and Health Advisories, Material Data Safety Sheets, company research literature, and literature available through your local county Extension office.
| Table 1. Pesticide Persistence in Soils | ||
|---|---|---|
| Low Persistence (half-life <30 days) | Moderate Persistence (half-life 30-100 days) | High Persistence (half-life >100 days) |
| Aldicarb | Aldrin | Bromacil |
| Captan | Atrazine | Chlordane |
| Dalapon | Carbaryl | Lindane |
| Dicamba | Carbofuran | Paraquat |
| Malathion | Diazinon | Picloram |
| Methyl Parathion | Endrin | Trifluralin |
| Oxamyl | Fonofos | |
| 2, 4-D | Glyphosate | |
| 2, 4, 5-T | Heptachlor | |
| Linuron | ||
| Parathion | ||
| Phorate | ||
| Simazine | ||
| Terbacil | ||
| TCA | ||