Tag Archives: Mark R. Wiesner

Algae outbreaks (dead zones) in wetlands and waterways

It’s been over seven years since I first started writing about Duke University’s  Center for the Environmental Implications of Nanotechnology and mesocosms (miniature ecosystems) and the impact that nanoparticles may have on plants and water (see August 11, 2011 posting). Since then, their focus has shifted from silver nanoparticles and their impact on plants, fish, bacteria, etc. to a more general examination of metallic nanoparticles and water. A June 25, 2018 news item on ScienceDaily announces some of their latest work,

The last 10 years have seen a surge in the use of tiny substances called nanomaterials in agrochemicals like pesticides and fungicides. The idea is to provide more disease protection and better yields for crops, while decreasing the amount of toxins sprayed on agricultural fields.

But when combined with nutrient runoff from fertilized cropland and manure-filled pastures, these “nanopesticides” could also mean more toxic algae outbreaks for nearby streams, lakes and wetlands, a new study finds.

A June 25, 2018 Duke University news release (also on EurekAlert) by Robin A. Smith, which originated the news item, provides more detail,

Too small to see with all but the most powerful microscopes, engineered nanomaterials are substances manufactured to be less than 100 nanometers in diameter, many times smaller than a hair’s breadth.

Their nano-scale gives them different chemical and physical properties from their bulk counterparts, including more surface area for reactions and interactions.

Those interactions could intensify harmful algal blooms in wetlands, according to experiments led by Marie Simonin, a postdoctoral associate with biology professor Emily Bernhardt at Duke University.

Carbon nanotubes and teeny tiny particles of silver, titanium dioxide and other metals are already added to hundreds of commercial products to make everything from faster, lighter electronics, self-cleaning fabrics, and smarter food packaging that can monitor food for spoilage. They are also used on farms for slow- or controlled-release plant fertilizers and pesticides and more targeted delivery, and because they are effective at lower doses than conventional products.

These and other applications have generated tremendous interest and investment in nanomaterials. However the potential risks to human health or the environment aren’t fully understood, Simonin said.

Most of the 260,000 to 309,000 metric tons of nanomaterials produced worldwide each year are eventually disposed in landfills, according to a previous study. But of the remainder, up to 80,400 metric tons per year are released into soils, and up to 29,200 metric tons end up in natural bodies of water.

“And these emerging contaminants don’t end up in water bodies alone,” Simonin said. “They probably co-occur with nutrient runoff. There are likely multiple stressors interacting.”

Algae outbreaks already plague polluted waters worldwide, said Steven Anderson, a research analyst in the Bernhardt Lab at Duke and one of the authors of the research.

Nitrogen and phosphorous pollution makes its way into wetlands and waterways in the form of agricultural runoff and untreated wastewater. The excessive nutrients cause algae to grow out of control, creating a thick mat of green scum or slime on the surface of the water that blocks sunlight from reaching other plants.

These nutrient-fueled “blooms” eventually reduce oxygen levels to the point where fish and other organisms can’t survive, creating dead zones in the water. Some algal blooms also release toxins that can make pets and people who swallow them sick.

To find out how the combined effects of nutrient runoff and nanoparticle contamination would affect this process, called eutrophication, the researchers set up 18 separate 250-liter tanks with sandy sloped bottoms to mimic small wetlands.

Each open-air tank was filled with water, soil and a variety of wetland plants and animals such as waterweed and mosquitofish.

Over the course of the nine-month experiment, some tanks got a weekly dose of algae-promoting nitrates and phosphates like those found in fertilizers, some tanks got nanoparticles — either copper or gold — and some tanks got both.

Along the way the researchers monitored water chemistry, plant and algae growth and metabolism, and nanoparticle accumulation in plant tissues.

“The results were surprising,” Simonin said. The nanoparticles had tiny effects individually, but when added together with nutrients, even low concentrations of gold and copper nanoparticles used in fungicides and other products turned the once-clear water a murky pea soup color, its surface covered with bright green smelly mats of floating algae.

Over the course of the experiment, big algal blooms were more than three times more frequent and more persistent in tanks where nanoparticles and nutrients were added together than where nutrients were added alone. The algae overgrowths also reduced dissolved oxygen in the water.

It’s not clear yet how nanoparticle exposure shifts the delicate balance between plants and algae as they compete for nutrients and other resources. But the results suggest that nanoparticles and other “metal-based synthetic chemicals may be playing an under-appreciated role in the global trends of increasing eutrophication,” the researchers said.

Here’s a link to and a citation for the paper,

Engineered nanoparticles interact with nutrients to intensify eutrophication in a wetland ecosystem experiment by Marie Simonin, Benjamin P. Colman, Steven M. Anderson, Ryan S. King, Matthew T. Ruis, Astrid Avellan, Christina M. Bergemann, Brittany G. Perrotta, Nicholas K. Geitner, Mengchi Ho, Belen de la Barrera, Jason M. Unrine, Gregory V. Lowry, Curtis J. Richardson, Mark R. Wiesner, Emily S. Bernhardt. Ecological Applications, 2018; DOI: 10.1002/eap.1742 First published: 25 June 2018

This paper is behind a paywall.

Nanotechnology takes the big data dive

Duke University’s (North Carolina, US) Center for Environmental Implications of Nano Technology (CEINT) is back in the news. An August 18, 2015 news item on Nanotechnology Now  highlights two new projects intended to launch the field of nanoinformatics,

In two new studies, researchers from across the country spearheaded by Duke University faculty have begun to design the framework on which to build the emerging field of nanoinformatics.

An August 18, 2015 Duke University news release on EurekAlert, which originated the news item, describes the notion of nanoinformatics and how Duke is playing a key role in establishing this field,

Nanoinformatics is, as the name implies, the combination of nanoscale research and informatics. It attempts to determine which information is relevant to the field and then develop effective ways to collect, validate, store, share, analyze, model and apply that information — with the ultimate goal of helping scientists gain new insights into human health, the environment and more.

In the first paper, published on August 10, 2015, in the Beilstein Journal of Nanotechnology, researchers begin the conversation of how to standardize the way nanotechnology data are curated.

Because the field is young and yet extremely diverse, data are collected and reported in different ways in different studies, making it difficult to compare apples to apples. Silver nanoparticles in a Florida swamp could behave entirely differently if studied in the Amazon River. And even if two studies are both looking at their effects in humans, slight variations like body temperature, blood pH levels or nanoparticles only a few nanometers larger can give different results. For future studies to combine multiple datasets to explore more complex questions, researchers must agree on what they need to know when curating nanomaterial data.

“We chose curation as the focus of this first paper because there are so many disparate efforts that are all over the road in terms of their missions, and the only thing they all have in common is that somehow they have to enter data into their resources,” said Christine Hendren, a research scientist at Duke and executive director of the Center for the Environmental Implications of NanoTechnology (CEINT). “So we chose that as the kernel of this effort to be as broad as possible in defining a baseline for the nanoinformatics community.”

The paper is the first in a series of six that will explore what people mean — their vocabulary, definitions, assumptions, research environments, etc. — when they talk about gathering data on nanomaterials in digital form. And to get everyone on the same page, the researchers are seeking input from all stakeholders, including those conducting basic research, studying environmental implications, harnessing nanomaterial properties for applications, developing products and writing government regulations.

The daunting task is being undertaken by the Nanomaterial Data Curation Initiative (NDCI), a project of the National Cancer Informatics Nanotechnology Working Group (NCIP NanoWG) lead by a diverse team of nanomaterial data stakeholders. If successful, not only will these disparate interests be able to combine their data, the project will highlight what data are missing and help drive the research priorities of the field.

In the second paper, published on July 16, 2015, in Science of The Total Environment, Hendren and her colleagues at CEINT propose a new, standardized way of studying the properties of nanomaterials.

“If we’re going to move the field forward, we have to be able to agree on what measurements are going to be useful, which systems they should be measured in and what data gets reported, so that we can make comparisons,” said Hendren.

The proposed strategy uses functional assays — relatively simple tests carried out in standardized, well-described environments — to measure nanomaterial behavior in actual systems.

For some time, the nanomaterial research community has been trying to use measured nanomaterial properties to predict outcomes. For example, what size and composition of a nanoparticle is most likely to cause cancer? The problem, argues Mark Wiesner, director of CEINT, is that this question is far too complex to answer.

“Environmental researchers use a parameter called biological oxygen demand to predict how much oxygen a body of water needs to support its ecosystem,” explains Wiesner. “What we’re basically trying to do with nanomaterials is the equivalent of trying to predict the oxygen level in a lake by taking an inventory of every living organism, mathematically map all of their living mechanisms and interactions, add up all of the oxygen each would take, and use that number as an estimate. But that’s obviously ridiculous and impossible. So instead, you take a jar of water, shake it up, see how much oxygen is taken and extrapolate that. Our functional assay paper is saying do that for nanomaterials.”

The paper makes suggestions as to what nanomaterials’ “jar of water” should be. It identifies what parameters should be noted when studying a specific environmental system, like digestive fluids or wastewater, so that they can be compared down the road.

It also suggests two meaningful processes for nanoparticles that should be measured by functional assays: attachment efficiency (does it stick to surfaces or not) and dissolution rate (does it release ions).

In describing how a nanoinformatics approach informs the implementation of a functional assay testing strategy, Hendren said “We’re trying to anticipate what we want to ask the data down the road. If we’re banking all of this comparable data while doing our near-term research projects, we should eventually be able to support more mechanistic investigations to make predictions about how untested nanomaterials will behave in a given scenario.”

Here are links to and citations for the papers,

The Nanomaterial Data Curation Initiative: A collaborative approach to assessing, evaluating, and advancing the state of the field by Christine Ogilvie Hendren, Christina M. Powers, Mark D. Hoover, and Stacey L. Harper.  Beilstein J. Nanotechnol. 2015, 6, 1752–1762. doi:10.3762/bjnano.6.179 Published 18 Aug 2015

A functional assay-based strategy for nanomaterial risk forecasting by Christine Ogilvie Hendren, Gregory V. Lowry, Jason M. Unrine, and Mark R. Wiesner. Science of The Total Environment Available online 16 July 2015 In Press, Corrected Proof  DOI: 10.1016/j.scitotenv.2015.06.100.

The first paper listed in open access while the second paper is behind a paywall.

I’m (mostly) giving the final comments to Dexter Johnson who in an August 20, 2015 posting on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website) had this to say (Note: Links have been removed),

It can take days for a supercomputer to unravel all the data contained in a single human genome. So it wasn’t long after mapping the first human genome that researchers coined the umbrella term “bioinformatics” in which a variety of methods and computer technologies are used for organizing and analyzing all that data.

Now teams of researchers led by scientists at Duke University believe that the field of nanotechnology has reached a critical mass of data and that a new field needs to be established, dubbed “nanoinformatics.

While being able to better organize and analyze data to study the impact of nanomaterials on the environment should benefit the field, what seems to remain a more pressing concern is having the tools for measuring nanomaterials outside of a vacuum and in water and air environments.”

I gather Christine Hendren has succeeded Mark Weisner as CEINT’s executive director.

Carbon nanotube accumulation in Duke University’s (US) mesocosm

This Oct. 1, 2014 news item on ScienceDaily about carbon nanotubes accumulating in the wetlands is carefully worded,

A Duke University team has found that nanoparticles called single-walled carbon nanotubes accumulate quickly in the bottom sediments of an experimental wetland setting, an action they say could indirectly damage the aquatic food chain. [emphasis mine]

The results indicate little risk to humans ingesting the particles through drinking water, say scientists at Duke’s Center for the Environmental Implications of Nanotechnology (CEINT). But the researchers warn that, based on their previous research, the tendency for the nanotubes to accumulate in sediment could indirectly damage the aquatic food chain in the long term if the nanoparticles provide “Trojan horse” piggyback rides to other harmful molecules. [emphases mine]

There’s a lot of hedging (could, if) in the way this research is being described. I imagine the researchers are indicating they have concerns but have no wish to stimulate panic and worry.

An Oct. 1, 2014 Duke University news release (also on EurekAlert), which originated the news item, goes on to explain the interest in carbon nanotubes specifically,

Carbon nanotubes are rapidly becoming more common because of their usefulness in nanoelectric devices, composite materials and biomedicine.

The Duke study was done using small-scale replications of a wetland environment, called “mesocosms,” that include soil, sediments, microbes, insects, plants and fish. These ecosystems-in-a-box are “semi-closed,” meaning they get fresh air and rainwater but don’t drain to their surroundings. While not perfect representations of a natural environment, mesocosms provide a reasonable compromise between the laboratory and the real world.

“The wetland mesocosms we used are a much closer approximation of the natural processes constantly churning in the environment,” said Lee Ferguson, associate professor of civil and environmental engineering at Duke. “Although it’s impossible to know if our results are fully accurate to natural ecosystems, it is clear that the processes we’ve seen should be considered by regulators and manufacturers.”

Ferguson and his colleagues dosed the mesocosms with single-walled carbon nanotubes and measured their concentrations in the water, soil and living organisms during the course of a year. They found that the vast majority of the nanoparticles quickly accumulated in the sediment on the “pond” floor. However, they found no sign of nanoparticle buildup in any plants, insects or fish living in the mesocosms.

That sounds marvelous and then the researchers provide a few facts about carbon nanotubes,

While this is good news for humans or other animals drinking water after a potential spill or other contamination event, the accumulation in sediment does pose concerns for both sediment-dwelling organisms and the animals that eat them. Previous research has shown that carbon nanotubes take a long time to degrade through natural processes — if they do at all — and any chemical that binds to them cannot easily be degraded either.

“These nanoparticles are really good at latching onto other molecules, including many known organic contaminants,” said Ferguson. “Coupled with their quick accumulation in sediment, this may allow problematic chemicals to linger instead of degrading. The nanoparticle-pollutant package could then be eaten by sediment-dwelling organisms in a sort of ‘Trojan horse’ effect, allowing the adsorbed contaminants to accumulate up the food chain.

“The big question is whether or not these pollutants can be stripped away from the carbon nanotubes by these animals’ digestive systems after being ingested,” continued Ferguson. “That’s a question we’re working to answer now.”

It’s good to see this research is being followed up so quickly. I will keep an eye out for it and, in the meantime, wonder how the followup research will be conducted and what animals will be used for the tests.

Here’s a link to and a citation for the researchers’ most recent paper on possible ‘Trojan’ carbon nanotubes,

Fate of single walled carbon nanotubes in wetland ecosystems by Ariette Schierz, Benjamin Espinasse, Mark R. Wiesner, Joseph H. Bisesi, Tara Sabo-Attwood, and P. Lee Ferguson. Environ. Sci.: Nano, 2014, Advance Article DOI: 10.1039/C4EN00063C First published online 03 Sep 2014

This is an open access paper.

I have written about Duke University and its nanoparticle research in mesocosms before. Most recently, there was a Feb. 28, 2013 posting about work on silver nanoparticles which mentions research in the ‘mesocosm’ (scroll down about 50% of the way). There’s also an Aug. 15, 2011 posting which describes the ‘mesocosm’ project at some length.

For anyone unfamiliar with the Trojan horse story (from its Wikipedia entry; Note: Links have been removed),

The Trojan Horse is a tale from the Trojan War about the subterfuge that the Greeks used to enter the city of Troy and win the war. In the canonical version, after a fruitless 10-year siege, the Greeks constructed a huge wooden horse, and hid a select force of men inside. The Greeks pretended to sail away, and the Trojans pulled the horse into their city as a victory trophy. That night the Greek force crept out of the horse and opened the gates for the rest of the Greek army, which had sailed back under cover of night. The Greeks entered and destroyed the city of Troy, decisively ending the war.