Report from the Sub-comittee on the environment and health

36
Soil water samples containing pesticides generally indicate use of <strong>the</strong>
pesticides in question on <strong>the</strong> surface of <strong>the</strong> ground directly over <strong>the</strong>
sampling site or transport with rainwater. Pesticides spilled on <strong>the</strong>
surface of <strong>the</strong> soil or pesticide waste buried near <strong>the</strong> sampling site can be
detected in soil water or drain water, but if several suction cups are
established under <strong>the</strong> same field, a point source occurrence near one of
<strong>the</strong>m can be detected.
Drain water samples represent water <strong>from</strong> <strong>the</strong> entire catchment area that
is drained by <strong>the</strong> drainage system in question. The catchment area can
include many fields with different uses, backfilled marlpits, buried waste,
sites for filling and washing of spraying equipment, greenhouses, etc. To
be able to interpret <strong>the</strong> result of a drain water sample it is important to
know which catchment area <strong>the</strong> sample in question represents. By
placing vertical drainpipes with screens at a depth of 1 metre one can
extract drain water samples that represent <strong>the</strong> local area around <strong>the</strong>
screen when <strong>the</strong> soil is saturated.
We have analyses of pesticides in soil and drain water <strong>from</strong> 10 different
localities in Denmark. The samples analysed include samples <strong>from</strong>
Højvands Rende and Bolbro Bæk, which are part of LOOP in Aquatic
Environment Plan I. A number of samples have also been taken in
special studies and research projects in <strong>the</strong> last 10 years. However, <strong>the</strong>re
have been no systematic analyses of pesticides in soil water and drain
water of <strong>the</strong> kind carried out in groundwater.
The results of all analyses of pesticides and <strong>the</strong>ir metabolites in soil and
drain water are shown in tables 4.13 and 4.14. Table 4.13 shows <strong>the</strong>
occurrences in fields with sandy soil, and table 4.14 <strong>the</strong> occurrences in
fields with clayey soil. These analyses do not include analyses of drain
water <strong>from</strong> filling and washing sites, greenhouses, and o<strong>the</strong>r point
sources, where high concentrations of pesticides have been found in
special analyses.
The analyses cover 27 pesticides and metabolites. The number of
analyses carried out is shown in <strong>the</strong> tables. The results are given as
detections of less than 0.1 microgramme per litre, detections greater than
0.1 microgramme per litre and <strong>the</strong> highest concentration detected. It will
be seen directly <strong>from</strong> a comparison of tables 4.13 and 4.14 that both <strong>the</strong>
concentration levels and <strong>the</strong> frequency of detections are highest in
localities with clayey soil. The substances detected in <strong>the</strong> highest
concentrations are atrazine (7.8 microgrammes per litre), hexazinone (4.3
microgrammes per litre), dichlorprop (1.4 microgramme per litre) and
2,4-D (1.2 microgramme per litre). Concentrations greater than 0.1
microgramme per litre have also been found for <strong>the</strong> pesticides
isoproturon, bentazon, MCPA, and mechlorprop, and for <strong>the</strong> degradation
products desisopropylatrazine, 2,4-dichlorophenol and ETU.
Some of <strong>the</strong>se detections can be correlated with pesticides used on
experimental areas or stated to have been used on <strong>the</strong> land in question.
For example, relatively high concentrations of both atrazine and
hexazinone (herbicides) were detected under a Christmas tree plantation,
where <strong>the</strong> substances had previously been used (Felding 1992). In some