Check out my new guest post. See it here at Water Underground!
Check out my new guest post. See it here at Water Underground!
In geochemistry I see the term “bad actors” used more often than it should be to describe well-known environmental contaminants. “Bad actors” refers to contaminants we see frequently in the environment and know have significant environmental or human health effects. Think mercury, nitrates, lead, arsenic, sulphur dioxide, etc.
However, this article is on the up and coming contaminants that are just starting to achieve awareness in the environmental community so I thought calling them rough teenagers was an apt play on words. Feel free to call me out for my use of rampant hyperbole. Nonetheless, the contaminants/classes of contaminant described here are starting to cause major environmental problems and accompanying angst for environmental scientists, regulators and companies. They are certainly starting to appear more frequently in the scientific literature as the academic community is alerted to their presence and potential effects, which results in an increase in publications exploring their environmental behaviour and impacts.
Pharmaceuticals are a major emerging contaminant. It seems like hardly a day goes by without another article on pharmaceutical products in major water bodies or how they pass through water treatment plants. The way a pharmaceutical product ends up in the environment is simple. We take them, pee out the excess which ends up in the water treatment plant or septic system and then is released to the environment. These drugs still retain their efficacy, at least to some degree, when they enter the environment and therefore can induce huge impacts throughout the ecosystem as they act on organisms much smaller and much different to humans.
Microbeads and Personal Care Products
This is a trendy one. Microbeads and similar additives to cosmetics and shampoos have really caught the attention of the media and their environmental impacts have not yet been fully understood. Microbeads are tiny, tiny pieces of recycled plastic, usually polyethylene or similar petrochemical plastics, that are added to personal care products to give them an abrasive feel when used. They make your shampoo feel like it’s rubbing/cleaning your scalp or skin. However, their environmental impact when you wash your shampoo down the drain is where the problem with microbeads starts. Their small size, less than 5mm and commonly much smaller than that, means they can pass through water treatment systems and enter freshwater bodies and the ocean. Once circulated within these waterbodies they are ingested by fish, birds and other aquatic life posing a threat to their health. In fact, the threat of microbeads and the fact that their concentration has increased in large water bodies so rapidly has led to their ban in many nations. Hopefully, we’ll be able to take microbeads off this list soon!
When you hear about element 34, Se, you might think of it as a helpful micronutrient, dandruff killer or it’s namesake, Selene, the Greek word for the moon. Unfortunately, it is much more harmful to the environment than we previously realized. The toxicity of selenium relates to the fact that it is a teratogen for fish and is even toxic for humans at higher doses. This means, that it leads to birth defects in fish and can lead to the disease selenosis in humans. The concentration at which it induces birth defects is also much lower than previously realized. Compounding selenium’s high toxicity is the fact that it is quite mobile in the environment and is easily transported in groundwater and surface water making it very difficult to control. Selenium is often released to the environment from mines as it co-occurs with a wide variety of other elements, such as lead, nickel, uranium, gold, and coal.
I see articles on this come up all the time, particularly about silver and copper nanoparticles, but there are others as well. It seems that the research community is kind of playing catch up in terms of assessing the transport and effect of nanoparticles on the environment, but I’ve started to see lots of articles on them now. Nanomaterials are particles that have a size range of 1-100 nanometres (10^-9 to 10^-7 m). They are used for an ever expanding variety of applications at the moment including coatings to add strength, keep your smelly socks from smelling, in electronics, in medecine, etc. The list is huge. However, once these nanomaterials have served their purpose or during their use they can be released to the environment. Once in the environment at higher concentrations these nanoparticles, often made of silver, carbon, titanium, cerium and other metals, can be ingested and inhaled by people and animals or enter the aquatic environment and expose fish and other aquatic biota. The effects that they have vary widely and are just starting to be understood but some types, such as silver, may affect plankton and algae, the basis upon which the aquatic food chain is built.
Rare Earth Elements
Rare earth elements (REE’s) such as cerium, dysprosium, lanthanum, etc. are being mined in greater quantities than even before to enable the production of cell phones and computers. Their widespread use has led to a boom in rare-earth element exploration and mining around the world as well as their relatively recent appearance in the litany of environmental contaminants. As newcomers, their effects are not yet fully understood, although given the increase in mining, research on the environmental effects of REE mines is forging ahead (I’m not sorry about the pun). Environmental exposure to REE’s has been implicated in a wide variety of human and ecological health effects such as cardic and respiratory issues. The mining of REE’s can also release a wide variety of other toxic elements such as arsenic, lead and cadmium. Furthermore, REE ores are often also enriched in radioactive elements, such as uranium and thorium, which can make REE mine wastes a radiological concern. If care is taken during the mining stage, however, REE’s can be mined safely.
These are just a few of the emerging contaminants I have seen gaining traction flipping through the literature. There are loads more unfortunately. As we develop new and better technologies the unintended consequence is that the waste products or products themselves may pose an environmental threat that we do not predict or understand in order to bring the product to market. It usually falls to the scientific community and regulators to bring awareness of the effects these contaminants have and propose solutions. Every action has a reaction, and the development of new industries and new technologies often results in environmental effects that can take many years to discover and resolve. That said, by being aware of these emerging threats to the environment it is possible to take steps to reduce their harm before it is too late. The very brief overviews above do not do justice to each category and the complexity of their environmental transport and effects; particularly as studies in the natural environment are uncommon and most toxicity information is based on lab tests.
There are a lot of other new and not so new contaminants that are still cycling through the environment. There are also some success stories where problems were recognized and fixed so I don’t mean to imply that all hope is lost. If you can think of some additional “rough teenagers” that I did not bring awareness to here please post them in the comments section!
A big welcome to the new EGU blog network blog Water Underground! Water Underground is the first geoscience blog that I am aware to be cross-hosted on both the EGU and AGU blog networks allowing it to reach people across the world. Water Underground, founded by Dr. Tom Gleeson, a prof at the University of Victoria, Canada, is a welcome addition to the EGU as it will cover groundwater, climate, and much more (it’s also good to have a fellow Canuck)! The writers of the blog are actually a collection of hydrogeologists and hydrologists from across the world, bringing a truly international perspective.
By the way, the image above is of an artesian spring that I took a few years ago near Chalk River, Ontario. See this link for my post about it.
A recently published paper (by myself and colleagues from uOttawa and Environment Canada) investigates the environmental fate of the long lived radioisotope of iodine, 129I, which was released by the Fukushima-Daichii Nuclear Accident (FDNA). Within 6 days of the FDNA 129I concentrations in Vancouver precipitation increased 5-15 times above pre-Fukushima concentrations and then rapidly returned to background. The concentrations of 129I reached were never remotely close to being dangerous, however they were sufficient to distinguish the impact of the FDNA on the region.
Subsequent sampling of groundwater revealed slight increases in 129I concentration that were coincident with the expected recharge times. This suggests that a small fraction of the FDNA-derived 129I may have been transported into local groundwater after infiltrating through soils.
What is iodine-129 and where does it come from?
Iodine-129 is the longest lived isotope of iodine with a half-life of 15.7 million years. It is radioactive and occurs everywhere throughout the environment. It is produced in three ways. The first two are natural and the third is by the nuclear industry.
The natural production of 129I occurs in the atmosphere and in soil/rocks. The atmospheric production happens when a cosmic ray proton hits a xenon-129 nucleus and removes a neutron, replacing it and creating an iodine-129 nucleus. The production in soil and rocks happens when a uranium-238 nucleus spontaneously fissions and one of the halves it releases has a mass of 129 ala, iodine-129.
The anthropogenic production occurs because when uranium fissions in a nuclear reactor sometimes one of the parts is 129I. This anthropogenic production is by far the largest source in the environment as substantial amounts have been released by nuclear fuel reprocessing. This 129I that has been released can trace a host of environmental processes and inform us about what happens to 129I or the much more dangerous, 131I. The current levels of 129I are much too low to pose a health threat to humans or the environment, but do allow 129I to be used as an environmental tracer.
129I from Fukushima is present in Vancouver, B.C. rain
The purpose of this research was to discover the fate of 129I in the released by Fukushima, which although a small amount, was isolated in time and space. We measured the 129I deposition in rain and its subsequent movement though soils and see if it reached groundwater. The results tell us about the impact of Fukushima, how 129I moves, where it is attenuated, and how quickly contaminants in this aquifer move from the ground surface to the water table. This knowledge can then be applied to understand 129I behavior in other settings such as nuclear waste repositories and watersheds or it can be used to learn about the behavior of other types of contaminant in this aquifer and how vulnerable it is to contamination.
The results in rain show an increase in 129I concentrations of up to 220 million atoms/L*. This increase was seen ~6-10 days after the emission from Fukushima began and are 5-15 times higher than rain samples collected before Fukushima. Following this increase 129I concentrations returned to background with a few weeks. This agrees with other studies monitoring the fallout of Fukushima derived radioisotopes [Wetherbee et al., 2012]. Furthermore, atmospheric back trajectory modelling shows trajectories for air parcels arriving in Vancouver from over the Pacific ocean and Japan.
We also calculated the mass flux of 129I from Fukushima. That is the actual quantity of 129I that was deposited on the region in grams, or in this case in atoms/m2. This was calculated by simply multiplying the concentration of 129I in rain by the amount of rain that fell. We found that only about 15% of the annual 129I deposition in the Vancouver region could be directly linked to Fukushima affected rain events. The total mass deposited by Fukushima was ~0.0000000000002 (2 x 10^-13) grams. This is a negligibly small quantity with respect to radioactive risk.
Despite the fact that the deposition of 129I from Fukushima was infinitesimally small it was still measurable. Therefore, the question became where did it go and can we learn about local groundwater resources using 129I as a tracer?
129I variation in groundwater may be due to Fukushima
The results in groundwater show very small 129I concentration increases. Two different wells were sampled. The first had a recharge time, which is the time it takes for water to move from the water table to the well screen, where it is sampled, of 0.9 years and the second had a recharge time of 1.2 years [Wassenaar et al., 2006]. The exact time it takes for water and dissolved contaminants to travel through the unsaturated zone was unknown. However, the sediments of this aquifer are very coarse and are known for their ability to rapidly transport contaminants, such as nitrate [Chesnaux and Allen, 2007]. Therefore, if we were going to see 129I from Fukushima this was an ideal location.
The increases in groundwater 129I concentrations were seen in two different wells (ABB03 and PB20) located close to one another. The two wells also had slightly different recharge times. The first was 0.9 years and the second was 1.2 years. The 129I anomaly in the first well occurred at 0.9 years and in the second well at 1.2 years. These 129I anomalies, which occurred exactly when the recharge age predicted they would, suggests that some of the 129I deposited by Fukushima was reaching the wells and causing these increases.In order to verify if it was possible for 129I to travel from the ground surface to the water table in the time required to produce the variations observed we modelled its transport time and attenuation through the unsaturated zone.
The time it took for 129I to reach the water table in the model was then added to the previously dated recharge time to get an estimate for how long it might take 129I from Fukushima to reach the wells we sampled. The results show that it is indeed possible for 129I deposited in rain to infiltrate through the unsaturated zone and reach the wells in time for us to detect it. However, this rapid transport assumes that certain flow paths exist to rapidly conduct 129I due to the heterogeneous lithology of the unsaturated zone. There is evidence of such flow paths [McArthur et al., 2010].
Thanks for reading, if you have any questions or concerns please leave a comment or send me an email to discuss further!
*Note: 100 million atoms/L of 129I is equivalent to an activity of 0.00000014 (1.4 x 10^-7) Bq/L. These quantities are extremely low level and only the most sensitive analytical methods in the world can detect them. This amount of radioactivity is several orders of magnitude lower than the natural background radiation produced by naturally occurring radionuclides in soil and the atmosphere. For more on naturally occurring radioactivity see here. Even a clean rainfall has about 1 Bq/L of tritium (radioactive hydrogen), which remains from atmospheric weapons testing in the 1960’s
Access the full paper here: http://onlinelibrary.wiley.com/doi/10.1002/2015WR017325/abstract
Chesnaux, R., and D. M. Allen (2007), Simulating Nitrate Leaching Profiles in a Highly Permeable Vadose Zone, Environ. Model. Assess., 13(4), 527–539, doi:10.1007/s10666-007-9116-4.
McArthur, S. A. Q., D. M. Allen, and R. D. Luzitano (2010), Resolving scales of aquifer heterogeneity using ground penetrating radar and borehole geophysical logging, Environ. Earth Sci., 63(3), 581–593, doi:10.1007/s12665-010-0726-9.
Wassenaar, L. I., M. J. Hendry, and N. Harrington (2006), Decadal geochemical and isotopic trends for nitrate in a transboundary aquifer and implications for agricultural beneficial management practices., Environ. Sci. Technol., 40(15), 4626–32.
Wetherbee, G. A., D. A. Gay, T. M. Debey, C. M. B. Lehmann, and M. A. Nilles (2012), Wet Deposition of Fission-Product Isotopes to North America from the Fukushima Dai-ichi Incident, March 2011, Environ. Sci. Technol., 46(5), 2574–2582.