The Lake Ecosystem Nanosilver Project
There is potential to apply nanotechnology to almost every economic sector, including consumer products, agriculture, medicine, transportation and energy. While nano-technology has the potential to produce societal benefits, it should be a priority to better understand the ecological risks from the release of nanomaterials into the environment. Because of its antibacterial properties, silver nanoparticles (AgNP) are currently the most widely used nanomaterials in various consumer products, including socks, underwear, sport clothing, shoe liners, adhesive bandages, antibacterial sprays, food storage containers, laundry additives, home appliances and paint.
Our previous laboratory research showed that nanosilver in the aquatic environment first affects organisms at the bottom of the food chain, including bacteria (Das et al., 2012 a,b) and algae (Das et al., 2014). These responses may have devastating effects upon aquatic ecosystems by reducing overall productivity and altering the cycling of nutrients, such as carbon, nitrogen and phosphorus. There may be compensatory mechanisms within aquatic ecosystems that can mitigate these responses, but it is impossible to predict these responses using laboratory studies.
Through support from the Strategic Grants Program of the Natural Sciences and Engineering Research Council of Canada and from Environment Canada, a team of researchers from Trent University and the International Institute for Sustainable Development (IISD) are conducting the Lake Ecosystem Nanosilver (LENS) project at the Experimental Lakes Area (IISD-ELA) in northwestern Ontario.
In 2012, we conducted a study to determine what happens when nanosilver is added to plastic tubes, or “mesocosms” deployed in one of the ELA lakes (see photo right). We added AgNP over several weeks to a total of 12 mesocosms and monitored what happens to the concentrations and the forms of silver in the water column, as well as the effects on bacteria, algae and plankton living in these systems. The photograph below shows the plume of AgNP (blue) right after addition to one of the mesocosms. Some of the results of this study have been published in peer-reviewed journals (Furtado et al., 2014; Furtado et al. 2015) and more articles will be published soon.
In 2014 and 2015, we conducted a whole lake study in which we added AgNP to Lake 222 at IISD-ELA. The Experimental Lakes Area has been used for over 40 years as a living laboratory to study the effects of pollutants in the environment, including past studies of the impacts of pollution from phosphorus, acid deposition, mercury and endocrine disruptor chemicals. These studies have resulted in policies to reduce the impacts of pollution. While we do not take lightly the impact that this study has had on Lake 222, this approach is the only way to determine ecosystem level impacts. Data generated from this study may influence regulatory policy regarding the ecological risks of nanomaterials.
The photograph below, right shows an aerial view of Lake 222. This is a small lake with a surface area of about 16.5 hectares and a maximum depth of approximately 6 meters. The lake stratifies during the summer to form an upper epilimnion and a lower hypolimnion, with a thermocline temperature gradient at about 3 meters depth.
The lake was dosed during the 2014 and 2015 field seasons with PVP capped AgNP (30-50 nm), purchased as a powder from NanoAmor (Houston, TX, USA). The powder was suspended in the lake water using a rotor-stator dispersion mill prior to addition to the lake. Every second day, 12 L of the AgNP suspension was added to the Lake 222 with a peristaltic pump from a point source along the southwestern shore of the lake, as shown in the photograph below. The additions in 2014 started on June 14th and continued until October 23rd, for a total addition of approximately 9 kg of AgNPs. The additions in 2015 started on May 15th and continued to August 25th for a total of approximately 6 kg added.
We are currently analyzing samples and gathering the data that we have collected over the two field seasons at Lake 222. We are also now monitoring the lake to see what has happened to the silver, now that the AgNP additions have been completed. We will update this website as our study results are published in the peer-reviewed literature.
For more information see the following publications
Das, P., CD Metcalfe, MA Xenopoulos. 2014. Interactive effects of silver nanoparticles and phosphorus on phytoplankton growth in natural waters. Environ. Sci. Technol. 48:4573-4580.
Das, P., C.J. Williams, R.F. Fulthorpe, Md. E. Hoque, C.D. Metcalfe, M.A. Xenopoulos. 2012. Changes in bacterial community structure after exposure to silver nanoparticles in natural waters. Environ. Sci. Technol. 46:9120-9128.
Das, P., CD Metcalfe, CJ Williams, ME Hoque, MA Xenopoulos. 2012. Effects of silver nanoparticles on bacterial activity in natural waters. Environ. Toxicol. Chem., 31:122-130.
Furtado LM, B Cheever, MA Xenopoulus, PC Frost, CD Metcalfe, H Hintelmann. 2015. Environmental fate of silver nanoparticles in boreal lake ecosystems, Environ. Sci. Technol. 49:8441-8450.
Furtado LM, ME Hoque, DF Mitrano, JF Ranville, B Cheever, PC Frost, MA Xenopoulos, H Hintelmann, CD Metcalfe. 2014. The persistence and transformation of silver nanoparticles in littoral lake mesocosms monitored using various analytical techniques, Environ. Chem. 11:419-430.