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Table of contents
PREFACE
SUMMARY
DANSK SAMMENDRAG
1 INTRODUCTION.
1.1 OBJECTIVE .
1.2 STRUCTURE OF THE PLAP .
2 PESTICIDE LEACHING AT TYLSTRUP
2.1 MATERIALS AND METHODS .
- 2.1.1 Site description and monitoring design .
- 2.1.2 Agricultural management.
- 2.1.3 Model set-up and calibration .
2.2 RESULTS AND DISCUSSION .
- 2.2.1 Soil water dynamics and water balances
- 2.2.2 Bromide leaching.
- 2.2.3 Pesticide leaching.
3 PESTICIDE LEACHING AT JYNDEVAD .
3.1 MATERIALS AND METHODS .
- 3.1.1 Site description and monitoring design
- 3.1.2 Agricultural management.
- 3.1.3 Model set-up and calibration .
3.2 RESULTS AND DISCUSSION
- 3.2.1 Soil water dynamics and water balances.
- 3.2.2 Bromide leaching.
- 3.2.3 Pesticide leaching.
4 PESTICIDE LEACHING AT SILSTRUP
4.1 MATERIALS AND METHODS .
- 4.1.1 Site description and monitoring design
- 4.1.2 Agricultural management.
- 4.1.3 Model set-up and calibration .
4.2 RESULTS AND DISCUSSION
- 4.2.1 Soil water dynamics and water balances.
- 4.2.2 Bromide leaching.
- 4.2.3 Pesticide leaching.
5 PESTICIDE LEACHING AT ESTRUP .
5.1 MATERIAL AND METHODS.
- 5.1.1 Site description and monitoring design
- 5.1.2 Agricultural management.
- 5.1.3 Model set-up and calibration .
5.2 RESULTS AND DISCUSSION
- 5.2.1 Soil water dynamics and water balances.
- 5.2.2 Bromide leaching.
- 5.2.3 Pesticide leaching.
6 PESTICIDE LEACHING AT FAARDRUP.
6.1 MATERIALS AND METHODS .
- 6.1.1 Site description and monitoring design
- 6.1.2 Agricultural management.
- 6.1.3 Model set-up and calibration .
6.2 RESULT AND DISCUSSION .
- 6.2.1 Soil water dynamics and water balances.
- 6.2.2 Bromide leaching.
- 6.2.3 Pesticide leaching.
7 PESTICIDE LEACHING AT SLAEGGERUP.
7.1 MATERIALS AND METHODS .
- 7.1.1 Site description and monitoring design
- 7.1.2 Agricultural management.
- 7.1.3 Model set-up and calibration .
- 7.2 RESULTS AND DISCUSSION
- 7.2.1 Soil water dynamics and water balances.
- 7.2.2 Pesticide leaching.
8 PESTICIDE ANALYSIS QUALITY ASSURANCE.
8.1 MATERIALS AND METHODS .
- 8.1.1 Internal QA
- 8.1.2 External QA
8.2 RESULTS AND DISCUSSION
- 8.2.1 Internal QA
- 8.2.2 External QA
8.3 SUMMARY
9 SUMMARY OF MONITORING RESULTS .
10 REFERENCES.
| Summary
In 1998, the Danish Government initiated the Pesticide Leaching Assessment Programme (PLAP), an intensive monitoring programme aimed at evaluating the leaching risk of pesticides under field conditions. The objective of the PLAP is to improve the scientific foundation for decision making in the Danish registration procedures for pesticides. The specific aim is to analyse whether pesticides applied in accordance with current regulations leach to the groundwater in unacceptable concentrations.
The PLAP includes evaluation of the leaching risk of 28 pesticides at six agricultural sites (ranging from 1.1 to 2.4 ha) representing a range of Danish soil and climate conditions. The pesticides were all applied at the maximum permitted rate. In order to describe water transport, bromide tracer was also applied to the fields. Bromide and pesticide concentrations are measured monthly in both the unsaturated and the saturated zones, and weekly in the drainage water. This report presents the monitoring results for the six agricultural sites during the monitoring period May 1999-June 2003, with the main focus on the last year of the monitoring period (July 2002-June 2003). The report must be seen as a provisional report because not all of the pesticides applied have been monitored for at least two consecutive years. The findings so far nevertheless show that:
- A quarter of the applied pesticides (7 of 28) were not leached during the current monitoring period.
- The monitoring data indicate marked leaching of four of the applied pesticides or their degradation products. Thus glyphosate and its degradation product AMPA as well as the degradation products of metribuzin, terbuthylazine and rimsulfuron leached from the root zone (1 m b.g.s.) in average concentrations exceeding the maximum allowable concentration of 0.1 µg/l.
- At the two sandy sites, previous application of pesticides has caused marked groundwater contamination with degradation products of metribuzin. These appear to be relatively stable, and both leached throughout the entire monitoring period, thus indicating continuation of leaching as long as four years after application. There was evidence that the degradation products may persist in the groundwater several years after application.
- Finally, the monitoring data indicate leaching of a further 17 pesticides. The levels of leaching hitherto detected were not unacceptable, however. Although the concentration in several samples exceeded 0.1 µg/l, the average concentration did not.
The monitoring data was supported by hydrological modelling (MACRO version 4.2) providing an overall water balance for each of the six sites. The models were parameterized using measured data as well as literature/default values. Subsequently the model was thoroughly calibrated to the sandy soils whereas a more simple calibration was done on the loamy soils. During the calibration period May 1999-June 2002 the models generally performed well when comparing simulated and observed time series for groundwater table, soil water content and drainage flow in the loamy soils, and for bromide concentration in the sandy soils. The latest year of the monitoring period, July 2002-June 2003, is considered a validation period and no further model calibration has therefore been performed. The model validation results confirmed the previous results indicating that all models generally performed well as regards predicting the above-mentioned time series.
The overall quality of the pesticide analysis was considered satisfactory. The QA system showed that:
- Reproducibility of the pesticide analyses was good, total standard deviation being in the range 0.001-0.053 µg/l.
- No differences in reproducibility were observed between pesticides and degradation products
- Recovery was generally good (70-125%) in external spiked samples. Low recovery of the pesticides desmedipham, fluroxypyr and phenmedipham was observed at single sites. High recovery was observed for bentazone and the degradation products triazinamin- methyl and triazinamin at single sites.
- Variation in recovery of the same compound in spiked samples from different field sites indicate that uncertainties in analysis are partly attributable to differences in matrix composition.
- Contamination of samples was not observed during collection, storage and analysis.
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