Oil Spill Effects 389 



I 



M Light Oil ;<0.2g cc"') 



Heavy Oil (0.2-1. Og cc"' ) 

 i 10 20m 



-T 1 — ^-r- 



20 40 60ft 



FIGURE 9-1. Ponds C 

 and E showing location 

 of sampling points for 

 temperature and oxygen 

 in 1970 (solid points), the 

 distribution of oil in July 

 1971, and the location of 

 the 1971 and 1972 vegeta- 

 tion transect (triangles). 



pond as the wind changed while the rest remained in the emergent- 

 vegetation zone. Some of the lighter fractions of oil evaporated and as the 

 remainder became more viscous, it began to adhere to the stems of the 

 emergent plants (first noticed in mid-August). Only a small amount of oil 

 penetrated into the sediment or into the wet litter. A lighter (rainbow- 

 colored) scum surrounded the margin of the ponds and extended over 

 much of the surface whenever the wind fell. Later, the lighter scum folded 

 into brown floating fans whenever it struck a blade of grass. These fans 

 were easily broken up by wave action and sunk. In September, the floating 

 oil retarded freezing so that the water beneath the oil accumulations did 

 not freeze until the ice was 2 cm thick on the rest of the pond. 



The following spring (1971), these same areas of accumulation 

 thawed more rapidly than the rest of the pond. Pond E did overflow during 

 the runoff but little oil moved out of the polygon due to filtering by the 

 snowpack and by the emergent plants. A few small clumps of plant litter 



