451 
Data tabulated below show the loss of insecticides from water containing 
mosquito larvae by codistillation: 
Original Conc. % Codistilled After 
Insecticide ppm 20 hours at 26.5°C 
aldrin -024 93 
dieldrin 024 55 
heptachlor 21 91 
heptachlor epoxide 225 : 42 
~ p,p'-DDT -0056 30 
chlordane 20 70 
lindane 2023 30 
Source: Buescher et al., 1964. 
Bridges (1961) found that endrin accidentally sprayed on a pond in Colorado 
to a level of 40ppb was gone from the water in a month, from the sediment 
in 3 months, from the vegetation in 2 months, and from the fish in 4 
months. 
DDT is considered to be one of the most persistent pesticides in the envir- 
onment. Two of its major metabolites are DDE and DDD. Of these two, DDE 
is the compound most frequently encountered in environmental sediment sam- 
ples. In soils and sediments DDT is slowly converted to DDE under aerobic 
conditions by fungi, molds, and bacteria. All of the cyclodiene insecti- 
cides including aldrin, chlordane, endrin, dieldrin, and heptachlor are 
generally held to be persistent in the environment. But all can be meta- 
bolized by various microorganisms. 
Even though some toxic, synthetic, organic compounds may be refractory to 
biologic degradation for long periods of time, there are other ways that 
these compounds are sequestered when combined in marine sediments. Many 
such compounds are bound to organic matter and clay particles in marine 
