Subscribe for email alerts

Don’t miss a single Science & Enterprise post. Sign up for our daily email alerts.

Please share Science & Enterprise

Effects Assessed of Manufactured Nanoparticles on Soybeans

Soybean field (ARS/USDA)

Soybean field (Agricultural Research Service/USDA)

Researchers from University of California in Santa Barbara found manufactured nanoparticles disposed after manufacturing or customer use can end up in agricultural soil and eventually affect soybean crops. Findings of the team that includes academic, government, and corporate researchers from elsewhere in California, Texas, Iowa, New York, and Korea appear online today in the Proceedings of the National Academy of Sciences.

The research aimed to discover potential environmental implications of new industries that produce nanomaterials. Soybeans were chosen as test crops because their prominence in American agriculture — it is the second largest crop in the U.S. and the fifth largest crop worldwide — and its vulnerability to manufactured nanomaterials. The soybeans tested in this study were grown in greenhouses.

The researchers studied two manufactured nanomaterials produced in large quantities: zinc oxide and cerium oxide. Zinc oxide is used in cosmetics, lotions, and sunscreens. These nanoparticles may dissolve and re-form as particles, or remain as a particle, as they are processed through wastewater treatment. At the final stage of wastewater treatment is a solid material, called biosolids, which is applied to soils in many parts of the U.S. This solid material fertilizes the soil, returning nitrogen and phosphorus that are captured during wastewater treatment, but they can also introduce zinc oxide to the soil.

Cerium oxide is used as an ingredient in catalytic converters found on vehicles and motorized farm equipment to minimize carbon monoxide production, and in fuel to increase fuel combustion. Cerium can enter soil through the atmosphere when fuel additives are released with diesel fuel combustion. Cerium oxide can enter the soil along with zinc oxide in biosolids from wastewater treatment.

The study shows that soybean plants grown in soil that contains zinc oxide accumulate zinc in the plants’ tissues. The soybean plants absorbed zinc into the stems, leaves, and beans. Food quality was affected, although it may not be harmful to humans to eat the soybeans if the zinc is in the form of ions or salts in the plants, according to UC Santa Barbara’s Patricia Holden, a professor of environmental science and the study’s senior author.

For cerium oxide, nanoparticles do not accumulate in the plant tissues, but growth among the test plants was stunted. The researchers found changes occurring in the root nodules, where symbiotic bacteria normally accumulate and convert atmospheric nitrogen into ammonium, a process that fertilizes the plant. These changes in the root nodules suggest that greater use of synthetic fertilizers may be needed when manufactured nanomaterials build up in the soil.

Holden says the likelihood of high concentrations of these nanoparticles in agriculture needs further monitoring. “We have very limited information about the quantity or state of these synthetic nanomaterials in the environment right now,” notes Holden. “We know they’re being used in consumer goods, and we know they’re going down the drain.”

Read more:

*     *     *

Comments are closed.