Hydrocarbons in Lakes Mead and Mohave

The National Park Service (NPS) provides stewardship over Lake Mead, Lake Mohave, and the lower Colorado River. These lakes are used intensely for recreational purposes including the use of 2 cycle engines. These types of engines have incomplete combustion and as a result spill about 30% of their fuel into the water. Fuel-related compounds such as benzene, toluene, ethylbenzene, and xylenes, and polycyclic aromatic hydrocarbons (PAH), can cause water degradation when released into water. These compounds also can be chronic or acutely toxic to aquatic life. Some compounds are carcinogens.

Volatile organic compound (VOC) and PAH analyses show boat traffic is the major contributor of these chemicals to Lakes Mead and Mohave. Input from urban Las Vegas area is not a big player in putting these chemicals into the lakes. Bed sediment is not highly contaminated at locations sampled during this study.

Objectives

Assess the concentration of VOC's and PAH at 20 sites in Lakes Mead and Mohave, and a segment of the Colorado River between the two lakes. The data obtained from these samples will help evaluate the effectiveness of long-term personal watercraft regulations. Information gained from these samples may have transfer value to other NPS units that are developing regulations for long-term usage of personal watercraft.

Strategy and Approach

Twenty sites will be samples for VOCs 4 times per year. Bottom sediment will be collected at selected sites and analyzed for PAHs. Passive sampling devices will be deployed for partitioning of polar and non-polar organic compounds.

Relevance and Benefits

This study is relevant to issues two, three, and eight of the Nevada Water Science Center Science Plan. These three issues address the need to assess human health effects, ecological health, and Lake Mead issues. The study also is consistent with a goal of the USGS Strategic Plan, which is to provide water-resource managers with accurate, reliable, and impartial scientific information. The work will benefit the cooperators and other water-resources agencies by providing information necessary for sound resource development and management decisions.

Publications

Lico, M.S., and Johnson, B.T., 2007, Gasoline-related compounds in Lakes Mead and Mohave, Nevada, 2004-06: U.S. Geological Survey Scientific Investigations Report 2007-5144, 29 p.

Lake Mead Bibliography: List of USGS Nevada WSC publications about Lake Mead, including cooperative State publications.