Soil Testing

Soils can provide valuable information on the history of use and contamination at a site since chemical constituents will often accumulate in soil horizons and remain stable for decades. Soil toxicity studies, like aquatic tests, are effective scientific tools that can provide accurate and reliable assessments of both the toxicity of chemicals and their bioavailability. TRE scientists are familiar with State of Washington, U.S.EPA, ASTM and OECD protocols for testing soil using plants and animals, having developed standard operating procedures for soil testing in the early 1990s. Short-term survival of organisms is evaluated using acute studies that are only a few days in length, while long-term survival and sublethal impacts are monitored using chronic toxicity tests with endpoints such as seed germination, survival, shoot and root length, biomass, nutrient levels, and pigment concentration.

Soil toxicity tests may be conducted as screening studies to determine the presence or absence of toxicity, or as definitive studies that use a series of soil concentrations, either collected from the field or prepared in the laboratory. Because of the level of effort, and thus cost, required for some soil tests, TRE prefers to work closely with clients and supporting consultants to clearly define the scope of work and Data Quality Objectives (DQOs) to yield usable data in the most cost-effective manner. Types of soil tests conducted by TRE include:

  • Earthworm acute, chronic and bioaccumulation (Eisenia fetida; Lumbricus terrestris)
  • 5-day root elongation using soil elutriates
  • 5-day lettuce emergence and germination in whole soil
  • 14-day germination, survival and growth with lettuce or ryegrass
  • 14-day survival and growth in wetland soil/sediment with freshwater millet (Echinochloa crusgalli)
  • Terrestrial plant toxicity tests of varying duration measuring germination, survival and growth
  • Long-term (up to several months) survival and growth of wetland emergent macrophytes (e.g., Pontederia)