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DDT LOAD ASSESSMENT FOR LAKES SURROUNDED BY ORCHARDS
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.orgCitation: Watershed Management to Meet Water Quality Standards and Emerging TMDL (Total Maximum Daily Load) Proceedings of the Third Conference 5-9 March 2005 (Atlanta, Georgia USA) Publication Date 5 March 2005 701P0105.(doi:10.13031/2013.18047)
Authors: P. S. Burgoon and P. Cross
Keywords: Orchard soils, lake sediments, DDT, turbidity, subsurface colloidal transport, soil erosion, TMDL
Historic use of DDT in orchards surrounding the Manson Lakes has resulted in residual DDT in orchard soils and lake. Consequently, both Roses Lake and Lake Chelan are on the 303(d) list for DDT metabolites in fish tissue. Concurrent sediment analysis revealed total DDT in the sediment. A 2 year project was completed for monitoring DDT and metabolite transport through the Manson Lakes and net export into Lake Chelan. DDT in surrounding orchards soils are similar to those measured in orchards throughout the nation 20 years ago. Sediment sampling showed that the elevated sediment concentrations measured 10 year ago have been buried or diluted from accumulation of new sediment. All surface waters entering and exiting the Manson Lake were sampled monthly for a variety of water parameters. This paper presents the sampling results of DDT, TSS and turbidity sampling. Total DDT was detected year round at concentrations that exceeded the chronic toxicity of 0.001 ug/L; concentrations never exceeded the acute toxicity concentration of 1.1 ug/L. T-DDT moves into the Manson Lakes by two transport mechanisms, 1). Sediment with adsorbed t-DDT is eroded from stream banks and orchards, and 2). T-DDT is transported on colloidal material, moving down through the soil profile year round. Samples from subsurface drains had elevated concentrations of Total DDT that were not correlated with TSS or turbidity. During 2002 about 57% percent of the DDT load was stored in the Manson lakes compared to about 79% storage in 2003. The estimated annual export of t-DDT to Lake Chelan was 1800 mg in 2002 and 2700 mg in 2003. About 85% percent of the DDT exported from the Manson Lakes into Lake Chelan occurred in the winter (December) and early spring (March). The strong seasonal influence may be due to lake turnover.(Download PDF) (Export to EndNotes)