Vol. 16—1962 - NorthEastern Weed Science Society

460
deteJ'lnined by a modification .~.: the 4-amino.~tipyrine colorlm~t'ic
method (2). Analyses forphe~ol were made iJIl.o.rder to asoertain
the background level of these naturally oocurring compounds fr~
decaying vegetation and to oq~~~t the 2,4-DOf data. The 2,4-0·
was determined by a modified bhromotropie a~~ color1metrio
method (3). '\
Materials
. . . ..-.. , -; , ;. " , ':t ,,~
The granular formulatiori,QeOntained 20 p,tr oent by weight.oid
equivalent of the 1-so-octylest,er of 2,1.L-dh~oropbenoxyaoeticiaoid.
This material was added at tnlil rate of 20 po~s of the acid ..
equivalent peraore or at theo,oncentration~ll.34 mg/l. This,
formulati.on was f.oupd also to contain 0.65milgram of 2,4-DCP or.
a ooncentration of ~.36 ug/lln the lake. " ,
Table I shows the chemicaf quality of ti1~.lake water. just I .
before addition of ~he 2,4-D.· The high pH value of 9.4 was attlr1.buted
to a tributary,cl[lrrying dra~nag~ from ,a l1~e,~one quarry. The
bicar.bonate, (.to.~&l).alkal1nit.y·.... _.nd thoe tota ..l..fha.r..dne sa were. of ,
low to medium conoen..trationlil.,,' the color v~+ e or 20 is fair1Y
low for surface waters. Or8~ni~ matter was ,.asured indireotll
th%'oush: the ohlorin$demand an-¢oB.O.D. analy~s. The valuesai'.
0.4 mS/1 ,.ana. I. 3.5 mg. /1, r.espect.i. ".el Y, indioa.,t.!E.. ,mall amounts ot,
organio matter. ,The natural or background '.~~'hold odor numb.~
of 2 was~ulte low and was qual1tativeJ,y IdeD~ltied as "earthY"i
or "musty'. Small, insignificant amount s 01"_'interfering sub- :
stanoes were repo;oted as 2,4-D epd phenol. lfo2,4-DCP was '
detected prior to herbicide t!'$atment." I
Results
No significant eftects on the chemical characteristics ot pH,
total l;1ardness, and total alkalinity (Table It bY' the 2,4-D weI'$
observed th%'oughout a samplintp~riod ot 70 ~.1s •. LikeWise, th~re
were no signifioant devlations.tromthe orig~'al values tor colpr,
chlorine demand, B.O.D. and d113i!Jolved oxygen'.~ These latter
analyses were made primarllytl)\observe any slIeondary etfects
on water quality by decaying vegetation. Apparently the release
of organio matter was too slow to register an appreoiable effect.
The threshold odor number remained at the value o~ 2 throughout
the sampling period'.,!lhe slS1'lticancecf thi. oboorvElt!on is .
discussed later in the paper. ' I'
Table II shows the oocurrence and perslstenceot 2,4-D,
2,4-DCP, ..andphenol atvarioue t.1meinterval.a....up ..to 132 days •.
The maximum conoentration ot 2,4~D, 49.5 ug/l~ was observed
13 days atter treatment whereupon there wu a'"gradual decrease I
to 13.0 ug/l atter 132 days .'J:'!?-ese data shQ~, :1:h.at very 11 ttle
2,4-D was detected in the "r:ree~rlowing" portion ot the lake
despite the fact that the he~btcide was appli.~ at the concentration
ot 1.34 nig/l. .• " ':,'