MacGREGOR: DDT OFF SOUTHERN CALIFORNIA 



depth when the 27 stations of heavy sewer deposi- 

 tion in shallower waters are omitted. 



The very high correlation coefficient (0.909) be- 

 tween p,p'DDD/p,p'DDT and p,p'DDE/p,p'DDT 

 shows that when metabolism of DDT to DDD is 

 high, metabolism of DDT to DDE is high also. 

 These high rates of metabolism are negatively 

 correlated with depth. Actually, they are more 

 probably associated with some of the conditions 

 prevailing at depth in the ocean off Los Angeles. 

 The deep areas sampled tend to be anaerobic, and 

 it is probably the lack of oxygen and colder water 

 that determines the low rate of metabolism. The 

 high correlations of the ratios with sample weight 

 and percent water are secondary effects of the 

 correlations of these two factors with depth. 



The high negative correlation between 

 p,p'DDE/p,p'DDD and depth indicates that 

 metabolism of DDT to DDE is favored over me- 

 tabolism to DDD in shallower waters. However, 

 the positive correlation ofp,p ' DDE /p,p' DDD with 

 p,p'DDD/p,p'DDT (0.297) as well as with 

 p,p'DDE/p,p'DDT (0.446) supports the conclusion 

 that metabolism to both metabolites is much 

 greater in shallow aerobic waters than in deep 

 anaerobic waters. Actually, much more DDT is 

 probably metabolized to DDD than to DDE under 

 all circumstances prevailing in the study area, 

 but the DDE is much more persistent than the 

 DDD and accumulates to a greater degree while 

 DDD is further metabolized to DDMU and other 

 metabolites. 



There was at least 10 times as much DDE as 

 DDT in the bottom sediments from stations along 

 the coast of the study area, while 10 stations in 

 deeper waters north of Santa Catalina Island had 

 less DDE than DDT in the bottom samples (Fig- 

 ures 3, 4). DDD tended to follow somewhat the 

 same pattern (Figure 5). 



At the 10 stations the average total DDT was 

 19.9 mg/m2, of which 60% was DDT, 19% DDD, 

 and 2V/c DDE. Mean depth was 341 fathoms (623 

 m) and the total area represented by the 10 sta- 

 tions was 111 sq nautical miles containing an es- 

 timated 5.74 metric tons of total DDT. 



It appears that most of the pesticide discharged 

 from the Los Angeles County sewer outfalls has 

 been DDT with the exception of the period of 

 sewer cleaning operations in 1970-71 when DDD 

 and DDE predominated (MacGregor 1974). Most 

 of the DDT settles on the bottom close to the out- 

 falls in shallow waters. Once the DDT becomes 

 part of the bottom sediment it tends to stay there 



Figure 3.— Distribution of ratios ofp.p'DDE top,p'DDT. In 

 the shallow waters near shore the ratios exceed 10:1, while in 

 the deeper waters north of Santa Catalina Island the ratios 

 are less than 1:1. 



B 



Figure 4. — Chromatograms of: A — a deepwater sample 

 1274 m), station 30-40, showing highp,p'DDT peak, and D— 

 a shallow-water sample (36.5 m), station 40-16, showing a high 

 DDE peak. B and C are standards of the DDT analogs. 



and metabolize in place, rapidly in shallower 

 waters and more slowly in deeper waters. 



31 



