In our study of the movement and accumulation of gold and silver nanomaterials in simulated salt-marsh enclosures, we found that the particles moved from the water column and were taken up by aquatic organisms. Our findings deepen our understanding of the threats that microscopic contaminants pose on marine life.
Why We Care
Nanomaterials are used in over 1,000 consumer products and may inadvertently contaminate sensitive estuarine and marine ecosystems. With at least one side less than 100 nm by definition, nanomaterials have unique chemical and physical properties (such as high surface area and variable dissolution properties) that may allow them to accumulate in the tissue of commercial fish and shellfish and interfere with the survival and growth of aquatic organisms.
What We Found
In the first study (Ferry et al., 2009), gold nanorods migrated from seawater into biofilms, sediments, plants, and animals. Based on a mass-balance model, approximately 84 percent of the gold was accounted for within the various compartments of the system. Clams and biofilms accumulated the greatest mass of nanoparticles, suggesting that gold nanorods can readily pass from the water column to the marine food web. In the second study (Cleveland et al., 2012), the silver migrated from the water column, accumulating in the estuarine biota (hard clams, grass shrimp, mud snails, cordgrass stalks/leaves, biofilms, intertidal sediment, and sand). The results of bioconcentration and trophic transfer factors indicated that significant amounts of silver were taken up by the organisms through trophic transfer. The nanomaterial products released significant amounts of silver over the 60-day study in the mesocosms, ultimately releasing 82 to 99 percent of their total silver loads.
What We Did
We performed two separate experiments to look at the movement and distribution of manufactured nanomaterials in estuarine mesocosms.
- Study 1. In a cutting-edge study, we added gold nanorods (about 65 × 15 nm) to the surface water of tidally manipulated estuarine mesocosms. Then we tracked the behavior and distribution of the particles for 12 days into various components of the ecosystem, including sediments, cordgrass, fish, shrimp, clams, snails, and biofilms. We then analyzed the components for the presence of gold using high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS).
- Study 2. In the second study, we tracked manufactured silver nanomaterials in mesocosm systems for 60 days as they leached from consumer products and raw materials. We studied silver nanospheres from three end-user consumer products: a bandage, a sock, and a toy bear. In addition, we tested 20-nm and 80-nm raw product silver nanospheres and non-nanoparticle ionic silver. In all cases, the silver was tracked as it migrated from the products in the various compartments of the system. We used HR-ICP-MS to detect the silver.
Having learned from these preliminary experiments that nanomaterials can move into the tissues of estuarine plant and animal species, our next steps include studying the effects of nanomaterials on the health of these aquatic organisms.