Report from the Sub-comittee on the environment and health

Table 4.17 shows <strong>the</strong> quantities of pesticide transported with surface runoff
in <strong>the</strong> years mentioned. For both years, <strong>the</strong> quantities, stated in parts
per thousand of <strong>the</strong> sprayed pesticide, were 0.08 for mechlorprop, 0.002
for dichlorprop and 0.001 for alphacypermethrin.
Mechlorprop and dichlorprop were detected particularly in <strong>the</strong> aqueous
phase of <strong>the</strong> surface run-off, while alphacypermethrin was only detected
in samples of water containing particles of soil, which accords with <strong>the</strong>
fact that this substance adsorbs strongly to soil particles. It will be seen
that <strong>the</strong> biggest run-off was of substances applied in <strong>the</strong> autumn.
Table 4.17
Spraying of pesticides on <strong>the</strong> trial field and pesticides detected in surface run-off (Felding et al. 1997).
The substances in question were authorised at <strong>the</strong> time of spraying.
Spraying date Pesticide Dose, kg a.i.
per ha
Concentration in
samples
(microgramme per
litre)
Total quantity in
run-off
(milligramme)
Period in which
pesticide occurred
after spraying
21-11-1991 mechlorprop 0.584 0.05-3.5
8 28/11-91 to
0.29-15
10/11-92
14-05-1992 dichlorprop 3.00 0.04-4.6 4 26/07-92 to
22/2-93
02-07-1992 alphacypermethri
n
0.0125 not detected - -
13-11-1992 mechlorprop 0.584 0.13-6.2
42 20/11-92 to
0.11-7.2
02/08-93
28-04-1993 dichlorprop 3.00 0.21-0.39 1 28/6-93 to 31/8-
93
30-06-1993 alphacypermethri 0.0125 0.01-0.21 0.009 25/07-93 to
n
11/09-93
a.i. = active ingredient
Events with run-off occur only, and momentarily, when <strong>the</strong> precipitation
within 24 hours exceeds 10 mm (DMU 1995); Groenendijk et al. 1994;
Liess et al. 1999; Møhlenberg, Gustavson 1999). On average, this occurs
three times a year in Denmark (Funen County, South Jutland County).
During precipitation events of more than 10 mm, <strong>the</strong> surface run-off of
pesticides make up 0.2 % of <strong>the</strong> pesticide pool <strong>from</strong> <strong>the</strong> nearest 2 ha in
<strong>the</strong> field, which, according to Groenendijk et al 1994, is a good estimate
in countryside with slight gradients. Swedish studies <strong>from</strong> 1990-1996
(Kreuger 1998; Kreuger, Tornqvist 1998) estimate correspondingly that
0.1-0.3% of <strong>the</strong> pesticide spread on fields in <strong>the</strong> catchment area are lost
to <strong>the</strong> aquatic environment. Recent German studies carried out near
Braunschweig, which has <strong>the</strong> same type of soil and field topography as
Eastern Denmark, has shown that <strong>the</strong> run-off of fenvalerate, among o<strong>the</strong>r
pesticides, occurred in pulses and was clearly associated with
precipitation events of more than 10 mm per day (Liess et al. 1999). The
total transport to a watercourse was calculated at between 0.012% and
0.068% of <strong>the</strong> total amount applied to a 9 ha field. Converting to a runoff
area of 2 ha and taking account of <strong>the</strong> degradation as used in <strong>the</strong>
model in section 10.3.3, that corresponds to a loss of 0.05-0.03% with
surface run-off (Møhlenberg, Gustavson 1999). Møhlenberg, Gustavson
use a loss of 0.2% <strong>from</strong> 2 ha as a conservative estimate in <strong>the</strong> model
calculations in section 10.3.3.
43