ANALYSIS OF PEAK DDT CONCENTRATION LEVELS VS. PEAK PRODUCTION AND CONSUMPTION LEVELS OF DDT IN MICHIGAN INLAND LAKES

DDT and its breakdown products (DDD and DDE) are still found in the environment despite nearly 40 years since its ban. Previous studies of inland lakes sediment cores have found historical peak DDT, and total DDT (DDT, DDD, and DDE) levels coincide within the time frame of peak production of DDT in 1962 and peak consumption in 1959. This observation has allowed us to hypothesize that DDT, DDD, and DDE levels should share a similar peak in lake sediment from that time period. If true, inland lake sediment deposited during this time period should show peak concentrations of DDT and its breakdown products to fall between 1959 and 1962. To test this hypothesis, core sediment samples were collected from 30 lakes in Michigan, sectioned into 2.0 cm samples and submitted for radiometric dating and chemical analyses. Findings show evidence for degradation of DDT in all lakes studied. Also, dates associated with peak concentration of DDT and its breakdown products varied from 1950’s to late 1970’s. Several lakes also exhibited increasing trends to present. Overall, this study concludes that DDT, DDD, and DDE concentrations within the lake sediment record to be largely consistent with peak production and consumption. However, it remains unclear why some lakes exhibit a delay in peak DDT values or an increase in recent sediments, possibly due to lag time in the movement of the compound from the landscape to the lake or continued use of the compound in some watersheds despite its ban. Also, literature DDT degradation rates of 15 to 20 years are shown to be inconsistent with some lakes studied, possibly owing to physical differences of the lakes studied.