Monday, April 8, 2013

Persistent Organic Pollutants in the Water and Atmosphere of the Western South Atlantic

by Erin Markham, University of Rhode Island Graduate School of Oceanography

Persistent organic pollutants (POPs) are compounds that have been created by humans and have the tendency to persist in the environment and to bioaccumulate in organisms through the food web. They can be transported long distances and have been known to cause adverse effects in both humans and the environment.

The majority of these contaminants became common somewhere between the 1940s and 1970s as industrial chemicals, pesticides, and byproducts; many have since been banned. "Legacy POPs" are those chemicals that have been banned for decades, but that still persist in the environment. This includes a group sometimes known as "the dirty dozen," things like PCBs and DDT that have largely been banned since the 1970s.

The air sampler is located up on the flying  bridge of
the Knorr, as high as possible and forward of
the exhaust to eliminate any ship-borne
contamination. (Winn Johnson, WHOI)
Even though these compounds have been out of production for decades, they are still detected at trace levels in the environment. Hydrophobic ("water-hating") compounds such as these attach to organic material or accumulate in fatty tissues. As a result, they tend to bioaccumulate and biomagnify up the food chain as one organism consumes several other contaminated organisms. POPs also sorb to settling particles in coastal ecosystems and collect in bottom sediments.

There are also emerging classes POPs that have either recently been banned or are not yet restricted. Per- and poly-fluorinated compounds (PFCs) fall under this category. PFCs have been in production since the 1950s, with high-volume production beginning in the 1970s, but most research on them has only been conducted within the past 15 years. The two compounds that are most prevalent in the environment are perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA).

Unlike the legacy POPs, these compounds are hydrophilic ("water-loving"), and so the ocean is believed to be their ultimate destination. PFOS was added to Annex B of the Stockholm Convention in 2009, meaning they are only permitted to be used only for limited purposes, but PFOA is still in common use and is a key component of such things as Teflon and Gore-Tex. Most PFCs, including PFOS and PFOA are found in both humans and the environment worldwide and more research needs to be conducted on their potentially adverse health effects.

This water sampler connects to the seawater
flow-through system on the ship, running first
through a filter and then through threepieces
of polyurethane foam. (Winn Johnson, WHOI)
My research on this cruise is focusing on both the traditional hydrophobic compounds as well as perfluorinated compounds. For the more traditional POP contaminants, I will take high-volume air and water samples (600-800 liters), and pass these through a glass-fiber filter and polyurethane foams (PUFs). The idea is that the compounds are likely to sorb to the PUFs and that by taking both water and air samples, we may be able to determine any air-water exchange gradients occurring in this region.

For the perfluorinated compounds, I will take one liter of water from various depths and analyze these for PFOS and PFOA. Much of the globe has been surveyed for surface water concentrations of PFCs, but very little is known about these contaminants at depth. We are particularly interested in the spread of these PFCs away from land via major rivers, such as the Rio de la Plata and the Amazon. Most likely, the transport of these persistent hydrophilic compounds to depth is their main removal pathway from the surface ocean. Sadly, this does not really remove them from the oceans, but is a step towards their ultimate dispersion and dilution worldwide.

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