EPA Posts Underwater Dispersant Monitoring Data

Under stringent plan, BP must conduct constant monitoring of dispersant use at leak source and provide data to the government

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FOR IMMEDIATE RELEASE
May 20, 2010

EPA Posts Underwater Dispersant Monitoring Data
Under stringent plan, BP must conduct constant monitoring of dispersant use at leak source and provide data to the government

WASHINGTON – The U.S. Environmental Protection Agency last night began posting results from the ongoing monitoring of BP’s use of underwater dispersants in the Gulf of Mexico at http://www.epa.gov/bpspill. EPA received this data from BP last night and posted it within hours. Dispersants are a chemical used to break up oil into small droplets so that they are more easily degraded. Dispersants are generally less toxic than the oils they break down.

This is part of EPA’s continued commitment to make air, water, sediment and dispersant monitoring data available to the public as quickly as possible and to ensure the citizens of the gulf region have access to all relevant public and environmental health information relating to the BP spill.

On May 15, EPA and the U.S. Coast Guard authorized BP to use dispersants underwater at the source of the Deepwater Horizon leak. As the dispersant is used underwater, BP is required to do constant, scientifically rigorous monitoring so EPA scientists may determine the dispersant’s effectiveness and impact on the environment, water and air quality, and human health. EPA is posting the information BP collects during the monitoring to ensure the public has access to this data.

While EPA has not yet identified any significant effects on aquatic life, EPA today also directed BP to begin using, within 72 hours, a less toxic and more effective dispersant. EPA took this step because BP is using this dispersant in unprecedented volumes and, last week, began using it underwater at the source of the leak – a procedure that has never been tried before. Given the unprecedented use, EPA wants to ensure BP is using the least toxic approved product.
Regardless of which dispersant BP uses, EPA has been and will continue to closely scrutinize the monitoring results. EPA still reserves the right to stop BP’s use of dispersants underwater entirely if the science indicates that this dispersant method has negative impacts on the environment that outweighs its benefits.

EPA continues to add information to its BP oil spill response Web site to keep the public informed about the impact of the spill and the EPA’s response. The public can also see results of EPA’s ongoing air, water and soil quality monitoring on the Web site.

The dispersant page: http://www.epa.gov/bpspill/dispersants.html
Continue to track EPA’s response to the spill: http://www.epa.gov/bpspill.

Additional information on the broader response from the U.S. Coast Guard and other responding agencies: http://www.deepwaterhorizonresponse.com

Dissolved Oxygen and Dispersants in the Gulf

At 20 C (room temperature) and standard atmospheric pressure (sea level), the maximum amount of oxygen that can dissolve in fresh water is 9 parts per million (ppm or mg/L). If the water temperature is below 20 C, there may be more oxygen dissolved in the sample. Generally a dissolved oxygen level of 9-10 ppm is considered very good. At levels of 4 ppm or less, some fish and macroinvertebrate populations (e.g. bass, trout, salmon, mayfly nymphs, stonefly nymphs, caddisfly larvae) will begin to decline. Other organisms are more capable of surviving in water with low dissolved oxygen levels (i.e sludge worms, leeches).

DO Percent Saturation values of 80-120 % are considered to be excellent and values less than 60% or over 125% are considered to be poor.

Low DO levels may be found in areas where organic material (dead plant and animal matter or oil) is decaying. Bacteria require oxygen to decompose organic waste, thus, deplete the water of oxygen. Areas near sewage discharges sometimes have low DO levels due to this effect. DO levels will also be low in warm, slow moving waters.

http://www.ciese.org/curriculum/waterproj/saturation.shtml

Question 1: Read the following statement and assess the normal range of DO for the Gulf of Mexico? Very Good, Good, or Bad

What is dissolved oxygen (DO) and why would dispersant application monitoring be stopped if DO levels dropped?

Dissolved oxygen (DO) analysis measures the amount of gaseous oxygen (O2) dissolved in the water. Adequate dissolved oxygen is necessary for good water quality. Normal ranges for DO in the Gulf area are 4 mg/l. The lower the concentration of dissolved oxygen, the greater the stress is on aquatic life. The evaluation criteria to determine further use of subsea dispersant include DO levels that are < 2mg/l and the results of toxicity tests.

http://www.epa.gov/bpspill/dispersants.html#q011

Question 2: Which organisms would you most expect to see while snorkeling in the Gulf of Mexico at 2 ppm DO? 4 ppm DO?

Fuel/Dispersant mixture is more toxic

This table unequivocally shows that a fuel/dispersant mixture is more toxic than either fuel or dispersant by itself. This is from the EPA website. LC50 is the Lethal Concentration that kills 50 percent of indicator species, in this case Menidia beryllina (the current EPA-approved marine vertebrate used in both acute and chronic toxicity testing.) and Mysidopsis bahia (opossum shrimp, an estuarine species suitable for life-cycle toxicity tests to determine the effect of a pollutant).


Corexit EC9500A has an LC50 of 25.20 ppm (96-hr) for Menidia beryllina and 32.23 ppm (48-hr) for Mysidopsis bahia.

No. 2 Fuel Oil has an LC50 of 10.72 ppm (96-hr) for Menidia beryllina and 16.12 ppm (48-hr) for Mysidopsis bahia.

Corexit EC9500A & No. 2 Fuel Oil (1:10) has an LC50 of 2.61 ppm (96-hr) for Menidia beryllina and 3.40 ppm (48-hr) for Mysidopsis bahia.

These results indicate that combining the dispersant with the fuel oil increases toxicity 4-10 times.

http://www.epa.gov/oem/content/ncp/products/corex950.htm