Which method can be used to prevent soil sample contamination during testing?

Cleaning tools and equipment thoroughly is essential to prevent soil sample contamination during testing because any residue or foreign particles on tools can significantly alter the sample's composition. Contamination can lead to inaccurate test results, which could affect the evaluation of soil properties and behavior. By ensuring that all tools, containers, and other equipment used during sampling are free from dirt, chemicals, or remnants from previous samples, one can maintain the integrity of the soil sample and achieve reliable results.

The other methods suggested could inadvertently introduce variables that compromise the samples. For instance, storing samples outdoors can expose them to environmental elements and pollutants. Using less water during sampling might not aid significantly in avoiding contamination and could affect the soil’s moisture content. Performing tests in windy conditions can also increase the chances of airborne particles settling in the samples. Therefore, maintaining clean tools and equipment is the most effective method for ensuring that soil samples remain uncontaminated.