Report from the Sub-comittee on the environment and health

cases, low concentrations of pesticides have been detected in places
where <strong>the</strong>se substances have not been used for years. This could indicate
that <strong>the</strong> retention time for <strong>the</strong> pesticides in question in <strong>the</strong> soil has been
long in <strong>the</strong>se cases. In a special analysis of <strong>the</strong> chlorophenoxy acids
MCPA, dichlorprop, 2,4-D and mechlorprop, all <strong>the</strong> substances were
detected after 3 years in soil water at a depth of one metre in
concentrations that were in several cases greater than 0.1 microgramme
per litre (Felding 1993). The detections of ETU are <strong>from</strong> a trial area
treated many times with dithiocarbamate fungicides, which break down
into ETU (Spliid 1998a).
As a test system between full-scale field analyses and simple laboratory
analyses, lysimeter analyses with undisturbed columns of soil can be
used to predict whe<strong>the</strong>r a pesticide or its degradation products can leach
<strong>from</strong> a column of soil. Such lysimeter analyses now form part of <strong>the</strong>
documentation material used as <strong>the</strong> basis for approving new pesticides. A
lysimeter can consist of a block of soil sampled at <strong>the</strong> site in a steel frame
without being disturbed. The lysimeter is moved to <strong>the</strong> test locality,
where crops are grown in it and it is treated with <strong>the</strong> pesticide in <strong>the</strong>
ordinary way. The naturally or artificially supplied water passing <strong>the</strong>
block of soil is collected. Using a radioactively labelled pesticide, one
can determine whe<strong>the</strong>r <strong>the</strong>re is any breakthrough of radioactivity and
thus of pesticide or degradation products. Where possible, <strong>the</strong> substances
passing <strong>the</strong> soil column are identified by means of chromatographic
methods and by comparison with reference substances. A lysimeter
analysis is typically carried out several years after <strong>the</strong> pesticide has been
applied. It can be used to determine <strong>the</strong> risk of a pesticide leaching in
different types of soil, with different cultivation conditions and in
different precipitation situations, with a surface area <strong>from</strong> 0.25 to 1 m 2 .
To determine <strong>the</strong> mobility in columns of soil in <strong>the</strong> deeper soil layers,
columns with a surface area of, for example, 0.25 m 2 can be sampled in a
steel cylinder and taken to <strong>the</strong> laboratory, where <strong>the</strong> temperature and <strong>the</strong>
groundwater’s movements can be simulated and controlled.
Table 4.13
Pesticides and metabolites detected in fields with sandy soil (Spliid 1998a)
Soil water and drain water analyses
Localities with sandy soil
Component Detections Detections Highest value Number of
< 0.1 µg/l > 0.1 µg/l (µg/l) analyses
Atrazine 10 1 0.11 98
Cyanazine n.d. n.d. n.d. 21
Desethylatrazine M
n.d. n.d. n.d. 21
Desisopropylatrazine M
1 1 0.11 21
Dimethoate n.d. n.d. n.d. 21
Hexazinone 1 n.d. 0.02 21
Hydroxy-carbofuran M
n.d. n.d. n.d. 21
Isoproturon 4 1 0.29 75
Metamitron 4 n.d. 0.01 21
Simazine 8 n.d. 0.09 82
Terbuthylazine n.d. n.d. n.d. 21
2,4-D 2 3 1.2 82
2,4-dichlorophenol M
7 5 0.22 54
2,6-dichlorophenol M
1 n.d. 0.05 54
4-chloro-, 2-methylphenol M
n.d. n.d. n.d. 54
Bentazone 3 2 0.1 21
37