Long-Term Degradation Studies - ACS Symposium Series (ACS

10 Long-Term Degradation Studies Massive Quantities of Phenoxy Herbicides in Test Grids, Field Plots, and Herbicide Storage Sites 1

ALVIN L. YOUNG

Downloaded by TUFTS UNIV on November 27, 2015 | http://pubs.acs.org Publication Date: August 15, 1984 | doi: 10.1021/bk-1984-0259.ch010

Agent Orange Projects Office, Veterans Administration, Washington, DC 20420

Three long-term studies have been conducted on the fate of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) when applied in high concentrations to f i e l d sites i n selected geographical locations. The f i r s t study, initiated i n A p r i l 1970, was of a 208-ha herbicide equipment-testing area (Test Area C-52, Eglin Air Force Base, Florida) that received more than 73,000 kg 2,4,5-T and 76,000 kg 2,4-D during the years 1962-1970. The second study, initiated i n 1972, was on the biological degradation of the herbicides when s o i l incorporated at rates as high as 4,480 kg/ha in plots established i n three climatically different areas of the United States; Northwest Florida, Western Kansas and Northwestern Utah. The third study, initiated i n 1977, was on the fate of the two herbicides in the soils of two 5-ha sites (Gulfport, Mississippi; and Johnston Island, Pacific Ocean) used for the long-term storage of more than 8.4 million L of surplus phenoxy herbicide. The environmental fate of 2,4-D and 2,4,5-T is compared between the individual studies.

From January 1962 to April 1970, a program of aerial a p p l i c a t i o n of h e r b i c i d e s was conducted in Southeast A s i a by the United States A i r Force (USAF). At the conclusion of t h i s program, considerable amounts of h e r b i c i d e were left unused. One of the h e r b i c i d e s used e x t e n s i v e l y in this p r o j e c t was a h e r b i c i d e designated as "Agent Orange" which was formulated as a 1

Current address: Office of Science and Technology Policy, Executive Office of the President, Washington, DC 20506

This chapter not subject to U.S. copyright. Published 1984, American Chemical Society

In Treatment and Disposal of Pesticide Wastes; Krueger, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1984.


162

TREATMENT AND DISPOSAL OF PESTICIDE WASTES

50:50 mixture of the η-butyl e s t e r s of 2,4-dichlorophenoxyacetic a c i d (2,4-D) and 2,4,5-trichlorophenoxyacetic a c i d (2,4,5-T). In 1970, approximately 8.4 m i l l i o n L of t h i s m a t e r i a l were placed i n storage by the A i r F o r c e . An a n a l y s i s of the h e r b i c i d e stocks revealed that i t contained the h i g h l y t o x i c contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The c o n c e n t r a t i o n of the TCDD ranged from 15,890 (1964-1966)

a

Amount of 2,4,5-T and 2,4-D c a l c u l a t e d on weight of a c t i v e i n g r e d i e n t i n the m i l i t a r y H e r b i c i d e s Orange and P u r p l e . Y e a r s when the s p e c i f i c g r i d r e c e i v e d the h e r b i c i d e .

b



164


Residue S t u d i e s . Despite e x c e l l e n t records as to the number of missions and q u a n t i t y of h e r b i c i d e per mission, there was no way to determine the exact q u a n t i t y of h e r b i c i d e deposited at any point on the instrumented g r i d s . The f i r s t r e s i d u e s t u d i e s of Test Area C-52A i n v o l v e d analyses of s o i l s f o r phenoxy h e r b i c i d e s by both chemical and bioassay techniques. These s t u d i e s , published by Young (2) i n 1974, showed that residues of the phenoxy h e r b i c i d e s r a p i d l y disappeared. However, problems were encountered i n these residue s t u d i e s because of the heterogeneity of the t e s t g r i d s . Not only were there small g e o l o g i c d i f f e r e n c e s ( s o i l types, contours, organic matter and ρ Η ) , and d i f f e r e n c e s i n v e g e t a t i o n d e n s i t y and l o c a t i o n s of water, but most important the h e r b i c i d e s had been sprayed on s p e c i f i c t e s t arrays ( i . e . , along d i c t a t e d f l i g h t paths) over a span of y e a r s . An obvious d i s p a r i t y a l s o e x i s t e d between bioassay data and chemical analyses because the l a t t e r a n a l y s i s f o r 2,4-D and 2,4,5-T alone could not account f o r a l l the b i o l o g i c a l l y a c t i v e phytotoxic components. The l a s t a p p l i c a t i o n of Agent Orange was a p p l i e d i n December 1969 at a r a t e of 28 L/ha. Chemical analyses of s o i l cores from the t r e a t e d areas showed that l e v e l s of t o t a l 2,4-D and 2,4,5-T i n the top 15 cm of s o i l averaged 2.82 ppm i n A p r i l 1970 and l e s s than 8.7 ppb i n December 1970. In October 1973, s o i l samples c o l l e c t e d from Grids I and I I were analyzed and found to c o n t a i n s i g n i f i c a n t l e v e l s of TCDD. Highest TCDD residues (740-1,500 parts per t r i l l i o n , ppt) were found on G r i d I, the area sprayed with H e r b i c i d e Purple i n 1962-1964. Subsequent s o i l samples confirmed TCDD contamination throughout three of the four t e s t g r i d s . The p e r s i s t e n c e of TCDD i n the s o i l s of Test Area C-52A has r e c e n t l y been described by Young, 1983 (4_). Vegetative S t u d i e s . To demonstrate the r a p i d dissappearance of phenoxy h e r b i c i d e s from the environment of the t e s t g r i d s , a v e g e t a t i v e succession study was conducted of the dicotyledonous s p e c i e s . Nine months (June 1971) a f t e r the l a s t d e f o l i a n t equipment t e s t mission, a d e t a i l e d survey of the v e g e t a t i o n was i n i t i a t e d . The 3.0 km^ area was d i v i d e d i n t o a g r i d of 169 s e c t i o n s (each 122 by 122 m), and w i t h i n each s e c t i o n the percentage v e g e t a t i v e coverage was v i s u a l l y ranked as Class 0, 0-5%; I, 5-20%; I I , 20-40%; I I I , 40-60%; IV, 60-80%; and V 80-100%. Three s e c t i o n s w i t h i n each c l a s s were s e l e c t e d at random and surveyed f o r dicotyledonous p l a n t s . An unsprayed area l o c a t e d 0.3 km northwest of the t e s t area was a l s o surveyed. In June 1973, each of these areas was again surveyed, but i n a d d i t i o n i n 15 s e c t i o n s , nine randomly s e l e c t e d areas, each 0.093 m, were analyzed f o r species composition and ground cover d e n s i t y . Vegetative coverage maps prepared i n 1971 and 1973 (Figures 1 and 2 r e s p e c t i v e l y ) confirmed that r a p i d r e - v e g e t a t i o n occurred immediately a f t e r h e r b i c i d e a p p l i c a t i o n s ceased. Table I I


10.

YOUNG

165

Degradation Studies of Phenoxy Herbicides

shows the percent coverage that each v e g e t a t i v e c l a s s i n June 1971 and i n June 1973.

Table I I . Percent of Vegetative Cover Occupied by Class f o r the 3 km Test Area

occupied

Vegetative


2

Vegetative Class 0 (0-5%) I (5-20%) I I (20-40%) I I I (40-60%) IV (60-80%) V (80-100%)

June

1971

June

1973

0 4 12 18 42 23

4 14 29 25 21 4

From June to September 1971, 74 dicotyledonous species were c o l l e c t e d on the 3 km Test Area, and 33 a d d i t i o n a l species were found during the June 1973 survey. The most important dicotyledonous p l a n t s found invading the t e s t area were rough buttonweed, D i o d i a t e r e s Walt; poverty weed, Hypericum gentianoides L.; and common polypremum, Polypremum procumbens L. The s t u d i e s of s o i l residues and v e g e t a t i v e succession of Test Area C-52A confirmed that massive q u a n t i t i e s of phenoxy h e r b i c i d e s r a p i d l y disappeared f o l l o w i n g the termination of an a e r i a l spray equipment t e s t i n g program. 2

S o i l Incorporation/Biodégradation P l o t s

One p o t e n t i a l method proposed f o r the d i s p o s a l of H e r b i c i d e Orange was subsurface i n j e c t i o n or s o i l i n c o r p o r a t i o n of the h e r b i c i d e at massive c o n c e n t r a t i o n s . The premise f o r such s t u d i e s was that high concentrations of the h e r b i c i d e s and TCDD would be degraded to innocuous products by the combined a c t i o n of s o i l microorganisms and s o i l h y d r o l y s i s . In order to f i e l d t e s t t h i s conceptj biodégradation p l o t s were e s t a b l i s h e d i n three c l i m a t i c a l l y d i f f e r e n t areas of the United States; Northwest F l o r i d a ( E g l i n A i r Force Base), Western Kansas (Garden C i t y ) and Northwestern Utah ( A i r Force L o g i s t i c s Command Test Range Complex). A comparison of the s o i l s of the three s i t e s i s given i n Table I I I . The Utah s i t e had a mean annual r a i n f a l l of 15 cm, while the Kansas and F l o r i d a s i t e s had 40 and 150 cm, r e s p e c t i v e l y . Table IV describes the experimental p r o t o c o l f o r the three s i t e s to i n c l u d e when the p l o t s were e s t a b l i s h e d , the method of h e r b i c i d e i n c o r p o r a t i o n , the experimental design and the i n i t i a l c a l c u l a t e d h e r b i c i d e c o n c e n t r a t i o n , ppm, at the %



T R E A T M E N T A N D DISPOSAL O F PESTICIDE WASTES

Figure 1. The May 1971 Vegetation Density Map of the 169 s e c t i o n s (each 122 m χ 122 m) that c o n s t i t u t e d the 2.5 km area that r e c e i v e d more than 69,300 kg 2,4-D and 2,4,5-T between June 1964 and December 1969, Test Area C-52A, E g l i n AFB, F l o r i d a . 2


Degradation Studies of Phenoxy Herbicides


YOUNG

Figure 2. The June 1973 Vegetation Density Map of the 169 s e c t i o n s (each 122 m χ 122 m) that c o n s t i t u t e d the 2.5 km area that r e c e i v e d more than 69,300 kg 2,4-D and 2,4,5-T between June 1964 and December 1969, Test Area C-52A, E g l i n AFB, F l o r i d a . 2


168


time the p l o t s were e s t a b l i s h e d . Further d e t a i l s on experimental p r o t o c o l can be obtained from Young, et a l (5)t 1974, and Young et a l (£), 1976.

Table I I I . Comparison of the C h a r a c t e r i s t i c s of the Top 15 cm Layer From Each of the S o i l Biodégradation S i t e s

Location

pH a

E g l i n AFB, F L Garden C i t y , K S AFLC Test Range Complex, UT


b

5.6 7.0 7.8

Organic Sand Matter (%) (%) 0.5 1.7 1.4

91.6 37 27

Silt (%) 4.0 42 53

Soil Clay Description (%) 4.4 21 20

Sandy loam S i l t loam Clay loam

C

a

P l o t s l o c a t e d on Test Area C-52A, E g l i n AFB Reservation, Florida. APlots l o c a t e d on the Kansas A g r i c u l t u r a l Experiment S t a t i o n , Garden C i t y , Kansas. P l o t s l o c a t e d 120 km west of S a l t Lake C i t y , Utah. c

Table V compares the degradation of t o t a l 2,4-D and 2,4,5-T (η-butyl e s t e r s and a c i d s ) over s i x years of observations i n the Kansas and F l o r i d a l o c a t i o n s . Although the r a t e s of a p p l i c a t i o n were s i m i l a r , the method of a p p l i c a t i o n , preplant i n c o r p o r a t i o n versus subsurface i n j e c t i o n , r e s u l t e d i n s i g n i f i c a n t d i f f e r e n c e s i n the i n i t i a l concentrations of h e r b i c i d e s i n the p l o t s . The a c i d of 2,4,5-T comprised most of the t o t a l r e s i d u e a f t e r the f i r s t two y e a r s . Although some residues were recovered, e s p e c i a l l y i n l a t e r years, at depths below 15 cm, the majority (90 percent) of residue was confined to the top 15 cm of s o i l p r o f i l e . The a d d i t i o n of s o i l amendments such as lime, organic matter and f e r t i l i z e r d i d not a p p r e c i a b l y i n c r e a s e the o v e r a l l r a t e of disappearance of the h e r b i c i d e . The a d d i t i o n of a c t i v a t e d coconut c h a r c o a l , however, s i g n i f i c a n t l y decreased the r a t e of disappearance of h e r b i c i d e . Six years a f t e r the c h a r c o a l p l o t s were e s t a b l i s h e d , residues ( p r i m a r i l y 2,4,5-T a c i d ) were s t i l l present. M i c r o b i a l s t u d i e s were conducted on the biodégradation p l o t s i n F l o r i d a . S o i l samples were taken from a l l p l o t s i n June and August 1974 (2 years) and i n A p r i l 1975 (3 y e a r s ) . Although b a c t e r i a l and fungal l e v e l s were s i m i l a r f o r c o n t r o l p l o t s or p l o t s r e c e i v i n g e i t h e r h e r b i c i d e or h e r b i c i d e plus the s o i l amendments lime, f e r t i l i z e r , and organic matter, the l e v e l s were s i g n i f i c a n t l y higher i n the p l o t s r e c e i v i n g the a c t i v a t e d c h a r c o a l . Microorganisms tended to be concentrated i n the l e v e l which contained the charcoal (0-15 cm), but g r e a t l y reduced i n


In Treatment and Disposal of Pesticide Wastes; Krueger, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1984. 5,000 10,000 20,000

1,120 kg Herbicide/ha 2,240 kg Herbicide/ha 4,480 kg Herbicide/ha

Simulated Subsurface I n j e c t i o n (8 cm band width)

10/2/72

AFLC Test Range Complex, Utah

c

b

a

1,000 2,000

2,240 kg Herbicide/ha 4,480 kg Herbicide/ha

Preplant Incorporate ( R o t o t i l l e r )

R a t e of h e r b i c i d e c a l c u l a t e d as a c t i v e i n g r e d i e n t . H e r b i c i d e i n j e c t e d a t 10-15 cm l e v e l or preplant incorporated i n the 0-15 cm l e v e l . A l l p l o t s d u p l i c a t e d . T h e amendments i n c l u d e d 4.5 kg l i m e , 13.5 kg organic matter, and 1.4 kg f e r t i l i z e r (12:4:8 f o r Ν,Ρ,Κ, r e s p e c t i v e l y ) uniformly mixed w i t h i n the top 0-30 cm of s o i l i n the p l o t . C o n t a i n e d i n the top 0-15 cm l a y e r .

5,000

5/10/72

5,000 5,000

Garden C i t y , Kansas

a

4,480 kg H e r b i c i d e / h a 4,480 kg Herbicide/ha, plus s o i l amendments^ 4,480 kg Herbicide/ha plus s o i l amendments and a c t i v a t e d charcoal

Treatment

Simulated Subsurface I n j e c t i o n (30cm band width)

Method of Incorporation

Calculated I n i t i a l Herbicide Concentration (ppm)

c

Studies I n v o l v i n g Use of H e r b i c i d e Orange

4/2/72

Date Established

D e s c r i p t i o n s of Three S o i l Biodégradation

E g l i n AFB, Florida

Location

Table IV.



170

Table V. Concentration (ppm) of T o t a l 2,4-D and 2,4,5-T ( H e r b i c i d e Orange) Over a Six-Year Period i n F i e l d P l o t s i n Kansas and F l o r i d a Florida


Time A f t e r Application (years) Day 5 0.25 0.5 1 1.5 2.0 2.5 ^ π j .υ 4.0 5.0 6.0

b

Herbicide + Amendments

Herbicide

+

+ Kansas 1,950 1,070 490 210 40

Long-Term Degradation Studies - ACS Symposium Series (ACS

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