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Establishment of a basis for administrative use of PestSurf

Annex 6

6 Comparison of risk assessment data produced by spray drift assessments, FOCUS SW and PestSurf

6.1 Chemical characteristics of the compound

Table 6.1. Overview of chemical properties of metamitron and the parameters used in the simulations.
Tabel 6.1. Oversigt over metamitrons kemiske egenskaber og parametrene brugt i simuleringerne.

6.2 Concentration generated by spray

6.3 Concentrations generated by FOCUS SW

6.3.2 D3- Ditch

6.3.3 D4 – Stream

6.3.4 D4 - Pond

6.3.5 Conclusion – FOCUS SW

The highest concentration is generated in the ditch (D3). It is caused by wind drift and the concentration becomes 3.67 µg/l. The same scenario shows the highest concentration in the sediment, 0.737 µg/kg. For all scenarios, the concentrations are lower than what is generated by the simpler assessments.

6.4 PestSurf

6.4.2 Sandy Catchment, stream

The distribution of concentrations was assessed in several steps. First, the maximum concentrations at each calculation point were listed, and the dates for the occurrence of the maximum were assessed. The points, for which the maximum value also represents a local maximum, were selected for further analysis. The relevant values are listed in Table 6.2.

Table 6.2. Maximum concentrations (ng/l) of metamitron simulated for each calculation point in the sandy catchment.
Tabel 6.2. Maximumkoncentrationer (ng/l) af metamitron simuleret for hvert beregningspunkt i det sandede opland.

The pattern over time was the same for all calculation points. The peak values are generated by wind drift, see Figure 6.1.

Each of the events generated an almost identical pattern along the stream, see Figure 6.2. The thin black line represents the concentration, while the thick black line shows the maximum concentrations obtained during the simulations. In addition, the outline of the stream is shown. In the middle of the catchment, the stream is protected by unsprayed areas. The maximum values at the center of the catchment are obtained when the peak from upstream move through the catchment during the hour following spraying.

In order to present the data in a similar fashion to the FOCUS SW-results, data were extracted and recalculated for the time series marked in Table 6.2. The global maxima and time weighted concentrations (up to 7 days) were extracted and are reported in Table 6.3 for actual and time weighted concentrations, respectively. Note that the unit is ng/l.

The pesticide sorption to macrophytes in the stream is shown in Figure 6.3, reaching a maximum concentration of 17 ng/l. This is not significant compared to the concentrations in the water phase. The concentration in pore water is shown in Figure 6.4. The concentration in sediment reaches 4 ng/kg.

Figure 6.1. Concentration pattern over time for metamitron in the sandy catchment.
Figur 6.1. Koncentrationsmønster som funktion af tid for metamitron i det sandede opland.

Figure 6.2. Concentration of metamitron in the sandy catchment on 1. May, 2001.
Figur 6.2. Koncentrationer metamitron i det sandede opland den 1. maj 2001.

Figure 6.3. Concentration of metamitron on macrophytes in the sandy catchment.
Figur 6.3. Koncentration af metamitron sorberet på makrofytter i det sandede opland.

Figure 6.4. Pore water concentration of metamitron in the sandy catchment.
Figur 6.4. Porevandskoncentration for metamitron i det sandede opland.

Figure 6.5. Concentration of metamitron in sediment in the sandy catchment. The maximum concentration reached in the catchment is 4 ng/kg. Note that the unit is in µg/g and not µg/m³ as stated.
Figur 6.5. Koncentration af metamitron i sediment i det sandede opland. Maximumskoncentrationen i oplandet er 4 ng/kg. Bemærk at koncentrationen er i µg/g og ikke i µg/m³ som angivet.

The global maximum value calculated by PestSurf for the sandy catchment in the water phase is 16.6 µg/l. This is considerably more than what is found in the D3-ditch scenario (3.67 µg/l). 112 m from the upstream end, the maximum value reached is 590 ng/l, and thus lower than the value obtained in the ditch scenario.

A small amount of pesticide was sorbed to macrophytes in the stream. The concentration in sediment is 0.737 µg/kg in the ditch-scenario and 4 ng/kg in PestSurf.

Figure 6.6 shows the output of the PestSurf Excel template. The template works with pre-defined data extraction points. The plot requires specification of a “lowest detection value” (ldc) which defines when a pesticide occurrence is defined as an event. The time series plot is identical to the time series shown earlier, and the graph in the upper right corner resembles the plot in Figure 6.2, but takes into account a longer period of time. A curve is generated when a downstream point reaches a concentration higher than the ldc. The programme then tracks the highest concentration for each calculation point in the stream within the last 24 hours. The plot in the lower right corner shows how many events have concentrations higher than a given value for the selected monitoring points. The curves are rather flat, showing little variation from year to year.

Table 6.4 shows part of the result sheet generated by the PestSurf Excel sheet based on the ldc-value. The selected table shows the point along the stream (of the pre-defined points) with the highest concentration. This value was, however, only 9.06 µg/l. Thus, the pre-defined points have not caught the highest concentration of the simulation, which was 16.6 µg/l.

Table 6.3. Concentration of metamitron, ng/l, at selected points in the sandy stream.
Tabel 6.3. Koncentration af malathion, ng/l, på udvalgte lokaliteter i det sandede vandløb.

Click here to see Table 6.3.

Click here to see Figure 6.6.

Figure 6.6. Overview for metamitron in the sandy catchment generated by the PestSurf excel template. The max concentrations generated over the 24 hours are similar to the overview in Figure 6.2. The graph to the lower right shows how many events have concentrations higher than a given value for the selected monitoring points. Detection value was set to 10 ng/l.
Figur 6.6. Oversigt for metamitron i det sandede opland genereret med PestSurf-excel-skabelonen. Den maximale koncentration genereret over 24 timer svarer til oversigten i Figur 6.2. Grafen nederst til højre viser hvor mange hændelser, der har koncentrationer højere end en given værdi i et udvalgt punkt. Detektionsgrænsen var sat til 10 ng/l.

Table 6.4. Part of the result sheet generated by the PestSurf Excel sheet. The selected table shows the point along the stream with the highest concentration recorded. The lowest detection valuε = 10 ng/l, toxicity to fish, daphnies and algae are set to 100, 1000 and 10000 ng/, respectively. The recorded peaks are shown in Figure 6.6.
Tabel 6.4. Uddrag af resultatpresentationen genereret af PestSurf-Excel-arket. Den udvalgte tabel viser det fordefinerede punkt langs med åen med højest koncentration. Detektionsgrænsen er sat til 10 mens toxicitetsværdierne for fisk, dafnier og alger er henholdsvis 100, 1000 og 10000 ng/l. De tabellerede hændelser er vist i Figur 6.6.

Click here to see Table 6.4.

6.4.3 Sandy Catchment, pond

The concentration pattern is evaluated in the middle of the pond only, see Figure 6.7. The pond receives drift and a contribution from groundwater. The maximum concentration is 689 ng/l. The high peaks occurring at the end of June and beginning of July 1999 and 2003 are caused by 26 mm of rainfall on 12^th June and 31.6 mm on 6^th July.

Figure 6.7. Concentration of Metamitron in the sandy pond.
Figur 6.7. Koncentration af metamitron i det sandede vandhul.

In Table 6.5, global maxima and time weighted concentrations (up to 7 days) were extracted. The presently used system of data storage stores data very frequently around the time of spray drift and extends the time period between data storage up to 1 day.

Table 6.5. Maximum concentrations (ng/l)of metamitron generated for the sandy pond.
Tabel 6.5. Maximumkoncentrationer af metamitron (ng/l) genereret for det sandede vandhul.

The sorption to macrophytes is shown in Figure 6.8. The sorbed concentration is considerably lower than the concentration in the water. The maximum concentrations reached for pore water is 28.8 ng/l (see Figure 6.9). The concentration of metamitron adsorbed to sediment is shown in Figure 6.10. The maximum value reached is 0.105 µg/kg.

Figure 6.8. Sorption of metamitron to macrophytes in the sandy pond.
Figur 6.8. Sorption af metamitron til makrofytter i det sandede vandhul.

Figure 6.9. Pore water concentration of metamitron in the sandy pond.
Figur 6.9. Porevandskoncentration af metamitron i det sandede vandhul.

Figure 6.10. Sorption of metamitron to sediment in the sandy pond. The concentration is in µg/g sediment and not µg/m³ as stated.
Figur 6.10. Sorption af metamitron til sediment i det sandede vandhul. Koncentrationen er i µg/g og ikke i µg/m³ som angivet.

Compared to the FOCUS D3 ditch, the concentration in the PestSurf sandy pond is considerably lower, 0.689 µg/l compared to 3.67 µg/l. The concentration in the sediment is 0.737 µg/kg in the FOCUS SW-D3 ditch calculation and 0.105 µg/kg in the PestSurf-calculation.

In the pond-case, there is no difference between the results of PestSurf and the results extracted by the templates.

Figure 6.11 shows the output of the PestSurf Excel template. The template works with one pre-defined data extraction point for the pond (center of the pond). The plot requires specification of a “lowest detection value” (ldc) which defines when a pesticide occurrence is defined as an event. The time series plot is identical to the time series shown earlier. The plot to the right shows how many events have concentrations higher than a given toxicity value for the selected monitoring points.

Table 6.6 shows part of the result sheet generated by the PestSurf Excel sheet based on the ldc-value.

Click here to see Figure 6.11.

Figure 6.11. Overview for metamitron in the sandy pond generated by the PestSurf excel template. The time series shown is identical to the one in Figure 6.7. The detection value used for generation of the figures is 10 ng/l.
Figur 6.11. Oversigt for metamitron i det sandede vandhul genereret med PestSurf-excel-skabelonen. Den viste tidsserie er mage til den i Figur 6.7. Detektionsgrænsen anvendt til generering af figurer er sat til 10 ng/l.

Table 6.6. Part of the result sheet generated by the PestSurf Excel sheet, applied to metamitron. The detection value used for generation of the table is 10 ng/l. Toxicity to fish, daphnies and algae are set to 100, 1000 and 10000 ng/, respectively. The recorded peaks are shown in Figure 6.11.
Tabel 6.6. Uddrag af resultatpresentationen genereret af PestSurf-Excel-arket anvendt på metamitron. Grænseværdien anvendt til tabelgenerering er 10 ng/l mens toxicitetsværdierne for fisk, dafnier og alger er henholdsvis 100, 1000 og 10000 ng/l. De tabellerede hændelser er vist i Figur 6.11.

Click here to see Table 6.6.

6.4.4 Sandy Loam Catchment, stream

The distribution of concentrations was assessed in several steps. First, the maximum concentrations at each calculation point were listed, and the dates for the occurrence of the maximum were assessed. The points, for which the maximum value also represents a local maximum were selected for further analysis (Table 6.7).

All points show the same type of time series pattern. The six points with highest maximum values were analysed further.

Table 6.7. Maximum concentrations (ng/l) of metamitron simulated for each calculation point in the sandy loam catchment.
Tabel 6.7. Maximumskoncentrationer (ng/l) af metamitron simuleret for hvert beregningspunkt i morænelersoplandet.

All maximum concentrations are caused by drift events, but the picture differs somewhat between the upstream and the downstream end of the main stream. Figure 6.12 and Figure 6.13 show the concentration pattern in the upstream end of the sandy loam catchment. Some drainage events are visible, most importantly the 20-year event on 18. September 1998.

Figure 6.14 shows a concentration pattern which is characteristic for the lower part of the sandy loam catchment. The drainage event becomes less important at this end of the catchment.

Figure 6.12. Concentration pattern for metamitron in the upstream part of the sandy loam catchment.
Figur 6.12. Koncentrationsmønster for metamitron i den opstrøms ende af morænelersoplandet.

Figure 6.13. Concentration pattern for metamitron in the upper part of the sandy loam catchment, about 90 m further downstream than Figure 6.13.
Figur 6.13. Koncentrationsmønster for metamitron i den opstrøms ende af morænelersoplandet, ca 90 m nedstrøms for lokaliteten i Figur 6.13.

Figure 6.14. Concentration pattern for metamitron in the lower end of the sandy loam catchment.
Figur 6.14. Koncentrationsmønster for metamitron i den nedstrøms ende af morænelersoplandet.

The concentrations in the sandy loam catchment are shown in Figure 6.15 for 30. April 2001. The thin black line represents the concentration, while the thick black line shows the maximum concentrations obtained during the simulations. In addition, the outline of the stream is shown.

Figure 6.15. Concentrations in the sandy loam catchment on 30. April 2001. The concentrations are generated by drift.
Figur 6.15. Koncentrationer i morænelersoplandet den 30.april-2001. Koncentrationerne genereres af drift.

To be able to extract comparable values to FOCUS SW, the global maxima and time weighted concentrations (up to 7 days) were extracted when these were meaningful. The values are listed in Table 6.8.

Table 6.8. Maximum concentrations (ng/l) of metamitron simulated for selected calculation point in the sandy loam catchment.
Tabel 6.8. Maximumskoncentrationer (ng/l) af metamitron for udvalgte lokaliteter i morænelersoplandet.

Click here to see Table 6.8.

Figure 6.16 and Figure 6.17 show the concentrations sorbed to macrophytes. The pattern follows the pattern of the water concentrations, and the maximum value recorded is 222 ng/l. This value is small compared to the concentrations in the water phase and the influence of the macrophytes on the concentration in the water phase is therefore negligible.

Porewater concentrations reached 3.90 ng/l (an example is shown in Figure 6.18), while sediment concentrations were 12.4 ng/kg at maximum (Figure 6.19).

Figure 6.16. Concentration of metamitron on macrophytes in ng/l in the upstream part of the sandy loam catchment.
Figur 6.16. Koncentration af metamitron på makrofytter i den opstrøms ende af morænelersoplandet.

Figure 6.17. Concentration on macrophytes in ng/l in the downstream end of sandy loam catchment.
Figur 6.17. Koncentration af metamitron på makrofytter i den nedstrøms ende af morænelersoplandet.

Figure 6.18. Maximum pore water concentration of metamitron for the main stream in the sandy loam catchment. The maximum value reached is 3.90 ng/l 125 m from the upstream end of the sandy loam catchment.
Figur 6.18. Maximale værdier for porevandskoncentrationen af metamitron i hovedvandløbet i morænelersoplandet. Den maximale værdi nået er 3.90 ng/l 125 m from the opstrøms ende af morænelersoplandet.

Figure 6.19. Sorption of metamitron on sediment in the sandy loam catchment. The concentration is in µg/g sediment and not µg/m³ as stated.
Figur 6.19. Sorption af metamitron til sediment i morænelersoplandet. Koncentrationen er i µg/g sediment og ikke µg/m³ som angivet.

Compared to the FOCUS SW-stream-scenario for D4, the concentration level in the sandy loam stream is much higher (44.9 µg/l compared to 3.05 µg/l). This value is found in the downstream end and thus affected by the simultaneous spraying of a long stretch of stream. 125 m from the upstream end, the concentration reaches 23.1 µg/l on 1.May 2005. The water depth in the upper 125 m is between 3.7 and 5.7 cm at the time of spraying, resulting in a factor of 6.4. In addition, the PestSurf stream is not rectangular.

The concentration in the sediment is considerably lower, 12.4 ng/kg compared to 149 ng/kg in the FOCUS SW-D4-stream. The flow velocity is a very important factor in limiting the diffusion from the water phase to the sediment.

Figure 6.20, Figure 6.21, Table 6.9 and
Table 6.10 show the results as generated by the PestSurf templates. The maximum value generated by the templates for the upper part of the stream is 16.3 µg/l, and for the lower part, 44.9 µg/l. The maximum value generated in the downstream part of the catchment by PestSurf is 44.9 µg/l. Thus, in this case, the templates did catch the maximum concentration of the PestSurf simulation.

Click here to see Figure 6.20.

Figure 6.20. Overview for metamitron in the sandy loam catchment generated by the PestSurf excel template for the upstream part of the catchment. The detection value was set to 10 ng/l.
Figur 6.20. Oversigt for metamitron i morænelersoplandet genereret med PestSurf-excel-skabelonen for den opstrøms del af oplandet. Detektionsgrænsen var sat til 10 ng/l.

Click here to see Figure 6.21.

Figure 6.21. Overview for metamitron in the sandy loam catchment generated by the PestSurf excel template for the downstream part of the catchment. The detection value was set to 10 ng/l.
Figur 6.21. Oversigt for metamitron i morænelersoplandet genereret med PestSurf-excel-skabelonen for den nedstrøms del af oplandet. Detektionsgrænsen var sat til 10 ng/l.

Table 6.9. Part of the result sheet generated by the PestSurf Excel sheet for the upstream part of the sandy loam catchment. The detection value for generation of the table is 10 ng/l, toxicity to fish, daphnies and algae are set to 100, 1000 and 10000 ng/, respectively. The recorded peaks are shown in Figure 6.20.
Tabel 6.9. Uddrag af resultatpresentationen genereret af PestSurf-Excel-arket for den opstrøms del af morænelersoplandet. Detektionsgrænsen for tabelgenerering er sat til 10 ng/l. Toxicitetsværdierne for fisk, dafnier og alger er henholdsvis 100, 1000 og 10000 ng/l. Hændelserne er vist i Figur 6.20.

Click here to see Table 6.9.

Table 6.10. Part of the result sheet generated by the PestSurf Excel sheet for the downstream part of the sandy loam catchment. The detection value for generation of the table is 10 ng/l, toxicity to fish, daphnies and algae are set to 100, 1000 and 10000 ng/, respectively. The recorded peaks are shown in Figure 6.21.
Tabel 6.10. Uddrag af resultatpresentationen genereret af PestSurf-Excel-arket for den nedstrøms del af morænelersoplandet. Detektionsgrænsen for tabelgenerering er sat til 10 ng/l. Toxicitetsværdierne for fisk, dafnier og alger er henholdsvis 100, 1000 og 10000 ng/l. Hændelserne er vist i Figur 6.21.

Click here to see Table 6.10.

6.4.5 Sandy Loam Catchment, pond

The concentration pattern is evaluated in the middle of the pond only, see Figure 6.22. The pond receives contributions through drift, in good correspondence with the fact that it is situated in the upper part of the sandy loam catchment. The maximum concentration is 0.355 µg/l.

Figure 6.22. Concentrations of metamitron for the sandy loam pond.
Figur 6.22. Koncentration af metamitron i morænelersvandhullet.

Figure 6.23. Metamitron sorbed to the macrophytes in the sandy loam pond.
Figur 6.23. Metamitron sorberet til makrofytter i morænelers-vandhullet.

Figure 6.23 shows the sorption of macrophytes in the pond. The concentrations are about 100 times lower than the concentrations in the water phase. The concentration in porewater is shown in Figure 6.24. As shown in Figure 6.25, the maximum concentration in sediment is quite small, 0.8 ng/kg.

Figure 6.24. Pore water concentration of metamitron in the sandy loam pond.
Figur 6.24. Porevandskoncentration af metamitron i morænelersvandhullet.

Figure 6.25. Metamitron sorbed to sediment in the sandy loam pond. The concentration is in µg/g sediment and not µg/m³ as stated.
Figur 6.25. Metamitron sorberet til sediment i morænelersvandhullet. Koncentrationen er i µg/g sediment og ikke µg/m³ som angivet.

In Table 6.11, global maxima and time weighted concentrations (up to 7 days) were extracted.

Table 6.11. Actual and time weighted concentrations (ng/l) of metamitron in the sandy loam pond.
Tabel 6.11. Beregnede og tidsvægtede koncentrationer (ng/l) af metamitron i morænelersvandhullet.

Figure 6.26 shows a page of the output from the PestSurf template, with a time series identical to Figure 6.22.

The FOCUS SW-scenario D4- pond generates a maximum concentration of 0.149 µg/l, while PestSurf reaches 0.355 µg/l. The difference can be explained by the difference in area of the two ponds.

The concentrations in the sediment differ substantially, being 62 ng/kg in the FOCUS-calculation and 0.8 ng/kg in the PestSurf calculation.

Click here to see Figure 6.26.

Figure 6.26. Overview for metamitron in the sandy loam pond generated by the PestSurf excel template. The time series shown is identical to the one in Figure 6.22. The lowest detection value was set to 10 ng/l.
Figur 6.26. Oversigt for metamitron i morænelersoplandet genereret med PestSurf-excel-skabelonen. Den viste tidsserie er mage til den i Figur 6.22. Detektionsgrænsen er sat til 10 ng/l.

Table 6.12. Part of the result sheet generated by the PestSurf Excel sheet. The lowest detection valuε = 10 ng/l, toxicity to fish, daphnies and algae are set to 100, 1000 and 10000 ng/, respectively. The recorded peaks are shown in Figure 6.26.
Tabel 6.12. Uddrag af resultatpresentationen genereret af PestSurf-Excel-arket. Detektionsgrænsen er sat til 10 ng/l. Toxicitetsværdierne for fisk, dafnier og alger er henholdsvis 100, 1000 og 10000 ng/l. De tabellerede hændelser er vist i Figur 6.26.

Click here to see Table 6.12.

Table 6.13. Summary of simulation results for metamitron.
Tabel 6.13. Opsummerede resultater for metamitron.

Click here to see Table 6.13.

6.5 Summary of Simulations

The maximum actual concentrations for all simulations are recorded in Table 6.13.

All maximum concentrations are generated by drift in the FOCUS SW-scenarios while in PestSurf, the maximum concentration for the sandy pond is generated by groundwater contributions.

The concentration in the sandy pond is smaller than the concentration in the D3 ditch, which again is smaller than in the sandy stream. For the pond, this is mainly due to lower exposure. For the stream, the higher concentration is due to the spraying along the whole stream within 30 minutes. 112 m from the upstream end of the stream, the concentration only reaches 0.590 µg/l, considerably less than the 3.67 µg/l reached further in the FOCUS SW D3-ditch. The difference is due to protection from a 20 m buffer zone. The water depth at the time of maximum concentration is 12.5 cm.

The D4 pond (149 ng/l) and the sandy loam pond (0.355 ng/l) differ in concentration level due to differences in pond characteristics. The difference in concentration is very close to a factor of 2.4.

With respect to the sandy loam stream, the concentration is considerably higher in the PestSurf simulation than in the D4-stream (44.9 µg/l compared to 3.05 µg/l). This is due to spraying along a long stretch of the stream and the very small water depth present at the time of spraying. 125 m from the upstream end, a maximum concentration of 23.1 µg/l is found. The corresponding water depth is around 5 cm. The maximum value on the 500-1700 m streach is 21.6 µg/l.

Macrophyte adsorption is low and does not play a role for the final concentration in the water phase.

The concentration in the sediment is considerably lower in the PestSurf-calculations. For the stream calculations, two major factors play a role. First of all, the water flow in the PestSurf streams is higher than in the FOCUS stream, leading much less diffusion into the sediment. Secondly, the description in PestSurf only contains one calculation layer for sediment, which is different from the FOCUS description. For the PestSurf ponds, the description of diffusion into sediment is similar to the description used in FOCUS. It is less clear why the concentrations are considerably lower in this case.

To judge the effect of the sorbed amounts on the water concentration, the amount per square meter can be calculated: For the D4-stream, the sediment concentration is 0.149 µg/kg. In 40 kg sediment^[1]/m^2,, the total amount is 5.96 mg. In the water phase, the concentration is 3.047 µg/l, in 300 l/m², resulting in 914 mg. The pesticide in sediment thus has a limited influence on the concentration in the water phase.

Footnotes

^[1] The weight of sediment is calculated as 1m*1m*0.05 m * 800 kg/m³

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Version 1.0 December 2006, © Danish Environmental Protection Agency