Vol. 15—1961 - NorthEastern Weed Science Society

The 15 minute, 0.1 mg/l residual chlorine demand was, in general,
increased by the liquid and granular herbicide formulations. When
the increase in chlorine demand was expressed as percent of the
control, it was found to be a function of the type of formulation,
concentration of the herbicide, and period of .storage. In general,
the liquid formulations produced higher chlorine demands for a given
herbicide concentration than the granular formulae. In addition, a
percentagewise increase in the chlorine demand was observed in the
liquid formulated systems as the concentration of the herbicide was
increased from 1 to 10 mg/l. The chlorine demand of the liquid carrier
systems showed an increase followed by a decrease during a 74 day
storage period. Neither the herbicide concentration nor length of
storage appeared to affect the percentage increase of the chlorine
demand produced by one of the granular formulations. In this system,
the chlorine demand increased by 50 percent and persisted for 50
days in the 1, 5, and 10 mg/l herbicide systems. The second granular
formulation showed an increase followed by a decrease in chlorine
demand during a storage period of 50 days.
Significant amounts of 2,4 dichlorophenol and 2,4,5 trichlorophenol
were found in all experimental systems. It was discovered in the
course of the investigation that the 4-amino antipyrine colorimetric
method offered by the 10th edition of Standard Methods does not
quantitatively detect para-substituted phenols. The prescribed pH
conditions of 10.0-10.~ do not permit the 4-amino antipyrine-phenol
complex to develop color. Thereupon, the method was modified to pH
conditions of 8.0+ 0.1 where the para-halogenated phenols developed
maximum color. Consequently, higher phenol concentrations were found
in the herbicide treated waters than initially indicated by the unmodified
method. For example, a water treated with a 1 mgjl acid
equivalent concentration of an ester formulation of 2,4-D showed a
2,4 dichlorophenol concentration of 58.2 ppb after 14 days of storage
by the modified method as against a 0.0 ppb phenol concentration by
the unmodified method.
547.
The concentration of the free phenolic contamination was found
to be a function of initial herbicide dosage and the type of formulation.
The free phenol concentrations imparted to the water by the liquid
formulated herbicide generally increased during a storage period of
140 days. On the other hand, the phenol concentration that resulted
from the granular 2,4-D formulations generally decreased during a
storage period of 92 days. For any given system, the phenol concentration
increased as the herbicide dosage was increased from 1
to 10 mg/l.
It is suggested that there are three mechanisms responsible for
the release of free phenols from the 2,4-D and 2(2,4,5}-TP herbicides.
They are as follows: (1) a free phenol impurity present in the
formulation as a result of the manufacturing process, (2) chemical
hydrolysis of the organic esters in water, and (3) biological degradation
of the ester portion of the herbicide. Several commercial formulations
of the 2,4-D herbicides were found to contain trace quantities of free
2,4 dichlorophenol. Likewise there is evidence from this inves~igation