Where should soil be preserved?

• A. In paper envelope
• B. In sterile paint cans or glass jars
• C. In a sealed plastic bag
• D. In a metal cookie tin

Answer: (B)

Soil preservation hinges on keeping the sample uncontaminated and as close to its original state as possible. That means using a clean, inert container that can be sealed tightly to prevent moisture exchange, dust entry, and cross-contamination, while also allowing proper labeling and chain-of-custody documentation. Sterile paint cans or glass jars meet these requirements by providing a sturdy, airtight interior and a surface that won’t react with the soil.

This is why they’re the best option: they minimize the risk of chemical interactions or biological changes in the soil, keep moisture stable, and maintain the integrity of trace clues that might be needed for later analysis. In contrast, a paper envelope is porous and susceptible to moisture loss, dirt ingress, and degradation, which can alter the sample. A sealed plastic bag can trap moisture and promote mold or microbial growth, and it also increases the chance of cross-contamination if the bag or the outside is compromised. A metal cookie tin might seem durable, but it’s not designed for clean, sterile storage and can introduce residues or corrosion products that interfere with analysis.

So, the safest, most reliable choice is a sterile, clean, airtight container such as a sterile paint can or glass jar.