VOC Loading from Marine Engines to a Multiple-use Lake

Abstract

A detailed boating use survey was conducted at a Northern California multiple-use lake, and the results were used to quantify daily MTBE and BTEX loading from recreational boating. Boat owner interviews and whole-lake activity surveys were conducted on 43 days between June 17 and September 20, 2000, including 38 days during the peak boating months of July and August. The dominant class of marine engines was found to be 4-stroke inboards and inboard/outboards, which constituted 60 percent of the total number of engines and consumed 69 percent of the fuel used at the lake. 2-stroke outboard engines with carburetors represented 26 percent of the engines and 14.3 percent of the fuel consumption, but were found to contribute 68 percent of MTBE and BTEX loading, while 4-stroke inboards were responsible for 4.2 percent. A sampling program was conducted in which MTBE/BTEX samples were collected on 23 days between May 22 and October 23, 2000. Results showed that MTBE appeared in 95 percent of epilimnetic samples up to a maximum concentration of 3.5 μg·l⁻¹ while toluene was detected in 22 percent of epilimnetic samples at a maximum concentration of 0.5 μg·1⁻¹. O-xylene was detected on one day, and benzene, ethlybenzene and m,p-xylene were not detected. The study demonstrated that MTBE is more persistent than BTEX compounds in surface water bodies, and accumulates over time with continuous inputs.

Key Words:

• fuel
• VOC
• lake
• MTBE
• BTEX
• loading