The Earth Story

Aromatic hydrocarbons

This gasoline pump is a design many around the world will be familiar with. Over the last few decades, pumps have been outfitted with covers for “vapor recovery”. In their best form, these devices work like vacuums – they have lower pressure than the surrounding air so that when compounds in gasoline begin to evaporate, they don’t escape into the air, but are instead sucked back into the storage tank.

If you’ve been to a gas station you’ve almost certainly smelled gasoline, either from the gas tank or after a bit of it spills. If we don’t mind a small spill of gasoline, why do we put effort into sucking these chemicals back in?

A major component of gasoline and one cause of the normal gasoline scent is the compound benzene is one of a family of compounds called “aromatic” compounds; carbon atoms being linked together in a ring define this group. Humans can easily smell benzene because it evaporates, but we shouldn’t do so as it is a known carcinogen. Benzene though isn’t the only compound in this group; there are much more complex molecules called “polycyclic aromatic hydrocarbons (PAHs)” that have several rings of carbon atoms joined together. These compounds are both carcinogenic and can impact other systems in the body such as the skin and kidneys. They don’t have the strong scent of benzene, but they’re present in petroleum products including gasoline and therefore they’re also vapor recovery targets.

PAHs also are produced in many simple chemical processes, including combustion. Forest fires, cooking meat on a grill, and processing of coal and asphalt can all give off PAHs. They are considered a regulated pollutant in both the US and the European Union, but so many common processes release them that their true processing by the planet is poorly understood.

Newly published research led by scientists at the Institute of Environmental Assessment and Water Research in Spain worked to characterize how these compounds, when released by humans, interact with Earth’s Oceans. They sampled waters and the air above the ocean while a research vessel moved around the world in 2010 and 2011, looking at how PAHs moved between the air and the ocean.

They found that ocean surface waters regularly absorb PAHs. On an ordinary day, compounds in the atmosphere slowly sink and deposit on the ocean surface, where they are taken up by the ocean waters. Many pollutants are scrubbed from the air by rain, but these chemicals were moved most easily during dry deposition.

The total volume of these chemicals available to the ocean worldwide is large. Based on this global ocean survey, the scientists estimated that the total input of PAHs to the world’s oceans at an ordinary time was happening at a rate equal to 4x the amount of these chemicals released by the Deepwater Horizon oil spill.

Once the compounds enter the ocean, they are available to life in the oceans if there are mechanisms available to break the chemicals down. Adding these chemicals to the oceans thus provides a type of food for certain organisms that was much less abundant in the oceans prior to human industrial processing. Summing around the oceans globally shows that these chemicals can represent as much as 15% of the carbon added to the ocean.

Increasing amounts of PAHs settling onto the ocean surface therefore is another major, recent disruption in the oceanic food chain driven by human industrial processing. These chemicals were available before humans, but much more rare; every time we spill a bit of gasoline we let more of them loose. What happens to the ocean food chain in areas of heavy PAH deposition and how those chemicals are processed once they reach the ocean is currently not well known; efforts to understand where these chemicals go once they reach the ocean surface is therefore a major project that needs to follow from this work.

-JBB

Image credit: Wisconsin DNR https://flic.kr/p/b3bgGz

References/Original paper: http://bit.ly/244sR4w http://link.springer.com/article/10.1007%2FBF02491036 http://greatist.com/health/smell-of-gasoline-addictive https://fortress.wa.gov/ecy/publications/documents/qa949.pdf http://bit.ly/1TFLPwI

Phosphorus storage

Phosphorus is a nutrient in high demand by life. It’s a major component of fertilizers and a component of sewage, so there are huge supplies of it carried downstream by rivers. Phosphorus is also a nutrient for organisms that live in lakes, rivers, and the ocean, so too much phosphorus also causes blooms of algae, using up oxygen other organisms need and sometimes releasing toxins that can make people sick. Managing phosphorus therefore is a major environmental issue, particularly in heavy agricultural areas.

In many areas, phosphorus usage has gone through a cycle. After phosphorus based fertilizers were developed in the early part of the 20th century, phosphorus usage skyrocketed in areas like Europe and the US. However, after environmental regulations were established and costs of fertilizers began increasing, phosphorus deployment decreased.

To understand how this deployment cycle affected pollution in the oceans, scientists led by Dr. Powers from the Center for Environmental Research, Education, and Outreach in Washington conducted a survey of phosphorus flows recorded leaving three rivers and combined it with a survey of phosphorus usage in the river basin.

The Thames River basin saw a rapid increase in phosphorus usage starting in the first half of the 20th century, but for the next 5 decades more phosphorus was used on the land than came out of the river. Around the year 1990, phosphorus usage in the Thames basin began declining, but interestingly phosphorus kept flowing out of the river. Total phosphorus in Thames River sediment did start to decline, but nowhere near as fast as phosphorus usage on land. Today, more phosphorus is leaving the Thames basin than is used as fertilizer.

Records for the Maumee River in Ohio, which contributes directly to algal blooms in Lake Erie, show a similar effect. Phosphorus usage in the basin has been declining since the 1970s, but phosphorus flows in the river have been increasing the entire time, and today more phosphorus flows into the lake than is used in the basin.

The measurements from these rivers suggest phosphorus has a long residence time in the river basins. It gets stored for some time, either in the sediments, soil, or in the groundwater, and releases gradually over time. Even dramatic cuts in phosphorus usage will take decades to translate to substantial cuts in nutrient pollution to lakes and oceans.

The most extreme location found by the researchers is the Yangtze River (Cháng Jiāng) in China. Phosphorus usage in that basin has skyrocketed since 1990 and as of right now the flows from the river represent only about 40% of the total phosphorus usage in the basin. Even if phosphorus usage started dropping today, outflows down that river will likely increase for years to begin removing the nutrient already present in that river basin.

-JBB

Image credit: Chelys http://bit.ly/1Txx6zT

Reference/Original Paper: http://bit.ly/1UL1V9k

More: https://www.epa.gov/nutrientpollution/problem

Clean Water Tastes Sweetest

You wouldn't think that adding sugar to your water or spraying it with Febreeze would ever be a good idea, but the same molecules behind the odor-absorbing spray are also behind a new breakthrough in water filtering: a sugar-based polymer that cleans water more efficiently (and more cheaply) than the activated carbon found in most commercial filters.

Rising levels of organic micropollutants like pesticides and pharmaceuticals in our water resources are a growing concern both to human health and ecosystems, but commonly used charcoal filters can take hours to absorb pollutants, and aren't effective against many types of pollutant. The new substance, cooked up by organic chemists at Cornell University, is a β-cyclodextrin polymer, and tests of its filtering capabilities have shown adsorption rates that are 15-200 times greater than those for charcoal and other filter types. When tested against BPA (Bisphenol A, a byproduct of plastic manufacturing linked to health risks) contaminated water, the β-cyclodextrin filter reached 95% of its adsorption capacity in just 10 seconds.

How does the filter work? A polymer is a long chain of repeating molecules, and the base molecule of the β-cyclodextrin polymer is made up of two parts. The first is called cyclodextrin, a ring of sugar molecules; this is the same molecule used in Febreeze to trap smelly particles. The second, and our Scrabble-winning word for the day, is called tetrafluoroterephthalonitrile. This mouthful is a 6 carbon ring with fluoride and cyano groups attached. (The second image below shows cyclodextrin in blue and the tetrafluoro molecule in red.) When the two components are combined together, the base molecule can be built into a porous 3D lattice. When water passes through the lattice, the micropollutants are pulled out of the water and get "stuck" to the filter.

Part of the filter's effectiveness is due to its surface area; the surface area per mass is so high that 2 grams contains enough area to cover an NBA basketball court. Some carbon filters have similar or higher surface areas, however; the real difference comes from the material properties. The sugar-based filter binds other molecules more effectively, and more quickly. The true advantages, though, are the ones that will hopefully make this technology easy to develop on a wider scale: it's cheaper by half than activated charcoal. It's also far easier to clean and reuse; charcoal has to be heated to a high temperature to release its captured pollutants, and loses some of its effectiveness afterwards. The β-cyclodextrin filter only needs to be washed with methanol at room temperature, and its effectiveness does not degrade as quickly. These factors combined may mean an improvement upon the Brita in your fridge or on your tap, but if the technology can be widely developed into an easily deployable form, it could also be a great boon for reducing pollution wide-scale, and for improving clean water access in developing countries.

-CEL Images: (1) Credit: Jacqueline Isabella Gisen (distributed via imaggeo.egu.eu) (2) Credit: http://bit.ly/1R3xQk8 Sources: http://bit.ly/1R3xQk8 Alsbaiee et al, 2015 http://bit.ly/1MC7D4e

MARINE POLLUTION - IT COMES FROM YOU

While this photograph, entitled “Other People’s Toys”, appears to simply represent waterfowl pursuing a soccer career, the photo and title both represent a larger, less comical issue. Every year humans consciously and subconsciously dump our unwanted or unused waste into our waterways. This waste is known as “marine pollution”.

Marine pollution comes from many sources however 80% of marine pollution originates on land, that’s right, the stuff we live on. While it’s easy to say it’s not our fault, this large fraction of litter in our waterways is due to our own subconscious disregard for our environment. Pollution originating on land can be loosely divided into two categories; point source and nonpoint source. Point source pollution is defined by the EPA Clean Water Act as “any discernible, confined and discrete conveyance…from which pollutants are or may be discharged.” In other words; anything that’s made by humans to carry pollutants more efficiently into the environment. While this is bad, nonpoint source pollution could be looked at as even worse. As its name suggests, it’s any pollution that doesn’t have a man-made way of reaching and infecting Mother Nature.

Both types of pollution are equally to blame for the negative impacts of land-based litter in our waterways. However, nonpoint source pollution is a much more difficult beast to address. Unlike point source, nonpoint source pollution doesn’t go through pipes, ditches, channels or anything else built with the intent to carry whatever waste humans decide to dispose of. Rather, nonpoint source pollution makes its way into the water by hitching a ride with whatever runoff might grab it.

The origin of these pollutants can be traced to places and items that we rely on as every day commodities, making it difficult to address. These include, but are not limited to, oil from car, truck, and boat engines, construction runoff, fertilizers, and air pollution (vehicle and aerosol emissions). This pollution doesn’t just hurt Mother Nature’s feelings, it also hurts our wallets. “Each year,” according to the National Oceanic and Atmospheric Administration (NOAA), “millions of dollars are spent to restore and protect areas damaged or endangered by nonpoint source pollutants.”

As humans pursuing continued existence on this planet, this should be a much larger deal than the general public views it as. The positive side of the subject cannot and will not be seen until we, the residents of this planet, do our part. “Our part” can range anywhere from picking up trash to driving more efficient cars to donating to local and national conservation organizations. Regardless of the medium, it’s up to us to make the difference, and we can.

-Mike

For more information regarding the NOAA: http://oceanservice.noaa.gov/facts/pollution.html. EPA: http://water.epa.gov/polwaste/nps/whatis.cfm. Photo credit: “Other People’s Toys”, Maret Hosemann, via flickr, http://www.flickr.com/photos/maret1983/6813956182.