MacGREGOR: AMOUNT AND PROPORTIONS OF DDT 



Figure 9. — Increase in p,p' DDE in the ocean off southern 

 California, 1949-70. The points are averages of all stations com- 

 bined in 2-yr groupings. Because the same patterns of stations were 

 not run each year, myctophids were not obtained from the same 

 stations or the same number of stations each year. Also pesticide 

 concentrations were more dependent on distance from the point 

 source of contamination than on year. This makes the coarse group- 

 ing of data necessary when increase in DDE with time only is 

 considered. The two theoretical lines are computed to the formula 

 Yf. = K(\-S^). in which Yc = computed value ofp.p'DDE, K = 

 value at which metabolism, excretion, and dispersal of DDE equals 

 input, S = survival of DDE for 1 yr, and X = year with 1949 

 considered as year no. 1. The data indicate thatp.p'DDE is very 

 stable. For the 98% survival curve, which more closely fits the data. 

 90% of the equilibrium value would not be attained for 1 14 yr. 



log y = log a + 6 log X + c log X' 



in which Y = calculated value of DDE in parts per 

 billion, X = distance from sewer outfall in nauti- 

 cal miles, andX' = year. The data were grouped 

 for greater ease of computation and to minimize 

 individual variations which tend to distort the 

 actual values transformed from log-log calculated 

 values if not minimized by averaging. 



The values determined for the above equation 

 are: 



log a 3.054 



6 (distance) -1.062 (SE 0.057) 



c (year) 1.423 (SE 0.122) 



The correlation coefficients are: 



multiple 

 partial (6) 

 partial (c) 



0.978 



-0.829 



0.522 



all of which are significant atP of less than 0.001. 



The computed lines did not fit the data for 1949, 

 1950, and 1951 very well. These years were left 

 out of the calculations because the input of DDE 

 was rising relatively rapidly at this time and did 

 not begin to stabilize until about 1953. Also in 

 these earlier years, the influence of the sewer dis- 

 charge of pesticide extended out to only about 100 

 nautical miles from the outfall. In the following 

 years the influence of the sewer discharge in- 

 creased rapidly to between 300 and 400 nautical 

 miles from the outfall before becoming indistin- 

 guishable from the ocean background. Although 

 there are no extensive data for any one station 

 throughout the period under study, we can now 

 calculate values for a theoretical station 20 nauti- 

 cal miles from the sewer outfall from the 

 DDE-time-distance formula and in conjunction 

 with the observed changes in ratios among the 

 various DDT analogs, obtain a description of the 

 metabolism of DDT in the marine environment as 

 reflected in the myctophid fish, S. leucopsarus. 



Because o,p'DDE was not quantified, we used 

 onlyp,/? 'DDE, p,p 'DDT, and p,p 'DDD in the ratios. 

 In more than 300 myctophids 30 mm or longer in 

 standard length in which the above three con- 

 stituents and o,p 'DDT and o,p 'DDD were measur- 

 able, o,p'DDT and o,p'DDD averaged 22.3% of 

 p,p'DDT and p,p 'DDD. In samples of commercial 

 DDT that were tested o,p 'DDT averaged about 

 25% of p,p 'DDT. 



From the calculated values of DDE and ratios of 

 DDE to DDT, we can calculate that at our 

 theoretical 20 mile station DDT accumulates in 

 the fish up to 1.077 ppm when input equals 

 metabolism. From this we may calculate that: 



Yt = 1.077(1 - 0.708^) 



in which Y, equals calculated p,p' DDT and X 

 equals the year with 1949 equal to year 1. From 

 the values obtained (Table 1, Figure 10) we may 

 recalculate values for DDE. These values remain 

 essentially the same as those calculated from the 

 DDE-time-distance formula for the later years 

 but make allowances for lower input from DDT for 

 the earlier years if we use the formula: 



2.0467^ = 0.368X - 1.077 + 1.077(0.708^) 

 or Ye = 0.18QX - 0.526 + 0.526(0.708^) 



in which Ye -= calculated p,p 'DDE andX equals 

 the year and in which we assume that there is no 

 further metabolism of DDE. 



285 



