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Establishment of a basis for administrative use of PestSurf

Annex 12

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

12.1 Chemical characteristics of the compound

Table 12.1. Overview of chemical properties of tribenuron-methyl and the parameters used in the simulations.
Tabel 12.1. Oversigt over tribenuron-methyl s kemiske egenskaber og parametrene brugt i simuleringerne.

12.2 Concentration generated by spray

12.3 Concentrations generated by FOCUS SW

12.3.1 D3- Ditch

12.3.2 D4 – Stream

12.3.3 D4 - Pond

12.3.4 Conclusion – FOCUS SW

The highest concentration is generated in the ditch (D3). It is caused by wind drift and the concentration becomes 0.095 µg/l. The same scenario shows the highest concentration in the sediment, 0.011 µg/l. For all scenarios, the concentrations are lower than what is generated by the simpler assessments, but for the ditch and stream-scenarios the difference between the simple drift calculation and the FOCUS SW-simulation is rather small.

12.4 PestSurf

12.4.1 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 12.2.

Table 12.2. Maximum concentrations (ng/l) of tribenuron methyl simulated for each calculation point in the sandy catchment.
Tabel 12.2. Maximumkoncentrationer (ng/l) af tribenuron-methyl 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 12.1.

Each of the events generated an almost identical pattern along the stream. Figure 12.2 to Figure 12.5 show the peak concentrations of tribenuron methyl moving through the sandy catchment after spraying.

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 hours following spraying.

Figure 12.1. Concentration pattern over time for tribenuron methyl in the sandy Catchment.
Figur 12.1. Koncentrationsmønster som funktion af tid for tribenuron-methyl i det sandede opland.

Figure 12.2. Concentrations of tribenuron methyl in the sandy catchment on 1. April 2001, 8.33.
Figur 12.2. Koncentrationer tribenuron-methyl i det sandede opland den 1. april 2001, 8.33.

Figure 12.3. Concentrations of tribenuron methyl in the sandy catchment on 1. April 2001, 9.00.
Figur 12.3. Koncentrationer tribenuron-methyl i det sandede opland den 1. april 2001, 9.00.

Figure 12.4. Concentrations of tribenuron methyl in the sandy catchment on 1. April 2001, 10.00.
Figur 12.4. Koncentrationer tribenuron-methyl i det sandede opland den 1. april 2001, 10.00.

Figure 12.5. Concentrations of tribenuron methyl in the sandy catchment on 1. April 2001, 12.00.
Figur 12.5. Koncentrationer tribenuron-methyl i det sandede opland den 1. april 2001, 12.00.

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 12.2. The global maxima and time weighted concentrations (up to 7 days) were extracted and are reported in Table 12.3. Note that the unit is ng/l.

Table 12.3. Concentration (ng/l) of tribenuron methyl at selected points in the sandy stream.
Tabel 12.3. koncentration af tribenuron-methyl, ng/l, på udvalgte lokaliteter i det sandede vandløb.

Click here to see Table 12.3.

An example of the amount of pesticide sorbed to macrophytes is shown in Figure 12.6. The maximum value of 1.7 ng/l is reached 1421 m from the upstream end. The concentration does not significantly influence the concentration in the water phase- The porewater concentrations are shown in Figure 12.7. The sorption to sediment is <0.01 ng/kg.

Figure 12.6. Typical concentration pattern for tribenuron methyl sorbed on macrophytes in the sandy catchment. The maximum value (1.71 ng/l) is reached 1421 m from the upstream end.
Figur 12.6. Typisk koncentrationsmønster af tribenuron-methyl sorberet på makrofytter i det sandede opland. Den maximalt opnåede værdi, ( 1.71 ng/l) is reached 1421 m fra den opstrøms ende.

Figure 12.7. Pore water concentration of tribenuron methyl in the sandy catchment. The maximum concentration reached is 0.019 ng/l 1421 m from the upstream end.
Figur 12.7. Porevandskoncentrationer af tribenuron-methyl i det sandede opland. Den maximale koncentration (0.019 ng/l) er fundet 1421 m fra den opstrøms ende.

The global maximum value calculated by PestSurf for the sandy catchment in the water phase is 321 ng/l. This is considerably more than what is found in the D3-ditch scenario (95 ng/l). However, 112 m from the upstream end, the concentration only reaches 10 ng/l, which is considerably less than what is found in the D3-ditch.

Sediment concentrations are 11 ng/kg in the D3-ditch scenaro and below 0.01 ng/kg in the PestSurf sandy catchment.

Figure 12.8 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 12.2, 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 (ldc) for the selected monitoring points.

Table 12.4 shows part of the result sheet generated by the PestSurf Excel sheet. The selected table shows the point along the stream (of the pre-defined points) with the highest concentration. This value was, however, only 187 ng/l. Thus, the pre-defined points have not caught the highest concentration of the simulation, which was 321 ng/l.

Click here to see Figure 12.8.

Figure 12.8. Overview for tribenuron methyl in the sandy catchment generated by the PestSurf excel template. The max concentrations generated over the 24 hours are similar to the overviews in Figure 12.2 and Figure 12.3. 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 0.05 ng/l.
Figur 12.8. Oversigt for tribenuron-methyl i det sandede opland genereret med PestSurf-excel-skabelonen. Den maximale koncentration genereret over 24 timer svarer til oversigten i Figur 12.2 og Figur 12.3. Grafen nederst til højre viser hvorm mange hændelser, der har koncentrationern højere end en given værdi for de prædefinerede lokaliteter. Detektionsgrænsen var sat til 0.05 ng/l.

Table 12.4. 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 value is 0.05 ng/l, toxicity to fish, daphnies and algae are set to 2, 10 and 20 ng/, respectively. The recorded peaks are shown in Figure 12.8.
Tabel 12.4. 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 0.05 ng/l mens toxicitetsværdierne for fisk, dafnier og alger er henholdsvis 2, 10 og 20 ng/l. De tabellerede hændelser er vist i Figur 12.8.

Click here to see Table 12.4.

12.4.2 Sandy Catchment, pond

The concentration pattern is evaluated in the middle of the pond only, see Figure 12.9. The pond receives drift but the contribution through groundwater dominates the picture during the wet years 1998-1999, repeated in 2002-2003. The maximum concentration is 289 ng/l. Between the time of spraying and the max concentration occurring in the pond is 27 mm of rainfall in 1998 (2002) and 50 mm in 1999 (2003). The general water level in the catchment must be high during these periods to cause such a quick response.

Figure 12.9. Concentrations of tribenuron methyl in the sandy pond.
Figur 12.9. Koncentration af tribenuron-methyl i det sandede vandhul.

In Table 12.5, global maxima and time-weighted concentrations (up to 7 days) were extracted.

Table 12.5. Maximum concentrations (ng/l) of tribenuron methyl generated in the sandy pond.
Tabel 12.5. maximumkoncentrationer af tribenuron-methyl (ng/l) genereret for det sandede vandhul.

The sorption to macrophytes is shown in Figure 12.10. The pattern follows closely the concentration in the water. The water concentration is marginally influenced by the presence of macrophytes. Time series of porewater concentration and tribenuron methyl sorbed to sediment is shown in Figure 12.11 and Figure 12.12. The maximum concentration reached in sediment is 3.1 ng/kg.

Figure 12.10. Sorption of tribenuron methyl to macrophytes in the sandy pond.
Figur 12.10. Sorption af tribenuron-methyl til makrofytter i det sandede vandhul.

Figure 12.11. Tribenuron methyl concentration in the pore water in the sandy pond.
Figur 12.11. Porevandskoncentration af tribenuron-methyl i det sandede vandhul.

Figure 12.12. Sorption of tribenuron methyl to sediment in the sandy pond. The concentration is in µg/g sediment and not µg/m³ as stated.
Figur 12.12. Sorption af tribenuron-methyl 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 higher, 0.289 µg/l compared to 0.095 µg/l. The ditch-concentration is caused by wind drift, while the concentration in the sandy pond is caused by groundwater contribution.

With respect to sediment concentrations, it is opposite. The concentration in the D3-ditch reaches 11 ng/kg while PestSurf only reaches 3.1 ng/kg.

In the pond-case, there is no difference between the results of PestSurf and the results extracted by the templates. Figure 12.13 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 12.6 shows part of the result sheet generated by the PestSurf Excel sheet based on the ldc-value.

Click here to see Figure 12.13.

Figure 12.13. Overview for tribenuron methyl in the sandy pond generated by the PestSurf excel template. The time series shown is identical to the one in Figure 12.9. The detection value is set to 25 ng/l.
Figur 12.13. Oversigt for tribenuron-methyl i det sandede vandhul genereret med PestSurf-excel-skabelonen. Den viste tidsserie er mage til den i Figur 12.9. Detektionsgrænsen er sat til 25 ng/l.

Table 12.6. Part of the result sheet generated by the PestSurf Excel sheet, applied to Tribenuron methyl. The limiting value used for generation of the table is 25 ng/l. The toxicity values were set to 50,100 and 1000 ng/l, respectively. The recorded peaks are shown in Figure 12.13.
Tabel 12.6. Uddrag af resultatpresentationen genereret af PestSurf-Excel-arket. Grænseværdien anvendt til tabelgenerering er sat til 25 ng/l mens toxicitetsværdierne for fisk, dafnier og alger er henholdsvis 50, 100 og 1000 ng/l. De tabellerede hændelser er vist i Figur 12.13.

Click here to see Table 12.6.

12.4.3 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 (Table 12.7). The points, for which the maximum value also represents a local maximum were selected for further analysis.

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

Table 12.7. Maximum concentrations (ng/l) of tribenuron methyl simulated for each calculation point in the sandy loam catchment.
Tabel 12.7. Maximumskoncentrationer (ng/l) af tribenuron-methyl simuleret for hvert beregningspunkt i morænelersoplandet.

All maximum concentrations are caused by drift events. Small drainage events are visible, particularly in the upstream part of the catchment. Figure 12.14 shows the concentration pattern for the upstream part of the catchment and Figure 12.15 for the lower part.

At the top end, two drainage events stand out in the simulations, 2-28 April 1996 and 2002, and the extreme event in September 1998. The April event is caused by 33 mm of rainfall on 2. April, the day after spraying and rain during the following period, see Table 12.8. This causes a drainage event on the 2. April, and the pesticide peak appears at its tail. The event on the 28 April causes another drainage event with pesticide occurrence.

Table 12.8. Rainfall in connection with tribenuron methyl peak in April 1996 and 2000.
Tabel 12.8. Nedbør i forbindelse med tribenuron-methyl-forekomst i april 1996 og 2000.

a)

b)

Figure 12.14. Concentration pattern for tribenuron methyl in Ovrelillebaek, 290 and 625 n m from the upstream end of the main stream in the upstream part of the sandy loam catchment.
Figur 12.14. Koncentrationsmønster for tribenuron-methyl i Øvre Lillebæk, 290 og 625 m frden øvre del af morænelersoplandet.

a)

b)

Figure 12.15. Concentration pattern for tribenuron methyl in the lower end of the sandy loam catchment.
Figur 12.15. Koncentrationsmønster for tribenuron-methyl i den nedre del af morænelersoplandet.

Three longitudinal profiles from a drift event are shown in Figure 12.16-Figure 12.18 depicts the concentrations on 31^st March 2000. 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 12.16. Concentrations in the the main stream of the sandy loam catchment on 31. March 2000, 8.30. The concentrations are generated by drift.
Figur 12.16. Koncentrationer i morænelersoplandet den 31. marts-2000, 8.30. Koncentrationerne skyldes drift.

Figure 12.17 .Concentrations in the the main stream of the sandy loam catchment on 31. March 2000, 9.00.
Figur 12.17. Koncentrationer i morænelersoplandet den 31. marts-2000, kl. 9.00.

Figure 12.18. Concentrations in the the main stream of the sandy loam catchment on 31. March 2000, 12.00. The concentrations are negligible in most of the catchment.
Figur 12.18. Koncentrationer i morænelersoplandet den 31. marts-2000, kl. 12.00. Koncentrationerne er ubetydelige i det meste af oplandet.

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 (Table 12.9).

Figure 12.19 and b)

Figure 12.20 show the concentrations sorbed to macrophytes in the upper and lower part of the catchment. The highest value reached is 28 ng/l 125 m from the upstream end of the main stream. Figure 12.21 shows the concentration of pesticide in porewater. The highest concentration reached is 0.279 ng/l 125 m from the upstream end of the main stream.

Due to low sorption, the amount of tribenuron methyl adsorbed to sediment is <0.01 ng/kg in most of the catchment. The maximum concentration in sediment (0.18 ng/kg) is shown in Figure 12.22.

The pattern of sorption to macrophytes follows the pattern of the water concentrations. The concentration influences the concentration in the water phase significantly, particularly outside the periods of drift contributions.

Figure 12.19. Concentration on macrophytes in OvreLillebaek. The pattern follows the pattern of concentrations in the stream.
Figur 12.19. Koncentration af tribenuron-methyl på makrofytter i Øvre Lillebæk. Mønsteret følger samme mønster som vandkoncentrationerne.

a)

b)

Figure 12.20. Concentration on macrophytes in ng/l in two points in NedreLillebaek. The pattern follows the pattern of concentrations in the stream.
Figur 12.20. Koncentration af tribenuron-methyl på makrofytter i to punkter i Nedre Lillebæk. Mønsteret følger samme mønster som vandkoncentrationerne.

a)

b)

Figure 12.21. Concentration of tribenuron methyl in porewater in the upstream and downstream ends of the sandy loam catchment. The maximum concentration reached in the catchment is 0.28 ng/l.
Figur 12.21. Koncentration af tribenuron-methyl i porevand i den opstrøms og nedstrøms ende af morænelersoplandet. Den maximale koncentration fundet i oplandet er 0.28 ng/l.

Figure 12.22. Maximum sediment concentration of tribenuron methyl in the sandy loam catchment. Note that the concentration is in µg/g and not µg/m³ as indicated.
Figur 12.22. Maximal sedimentkoncentration af tribenuron-methyl i morænelersoplandet. Bemærk at koncentrationen er i µg/g sediment og ikke µg/m³ som angivet.

FOCUS SW D4-stream reaches 76 ng/l while PestSurf generates 747 ng/l. Both models generate the maximum concentrations through wind drift. However, some drainage contribution does take place in the sandy loam stream. 125 m from the upstream end, the concentration reaches 553 ng/l. The water depth at the time of maximum concentration is around 4.8 cm. This, and the fact that the PestSurf stream is not rectangular, accounts for the difference between the two models.

For the sediment, the D4-simulations reach 2 ng/kg while PestSurf predicts a maximum of 0.18 ng/kg.

Figure 12.23, Figure 12.24, Table 12.10 and Table 12.11 show the results as generated by the PestSurf templates. The maximum value generated by the templates for the upper part of the stream is 288 ng/l, and for the lower part 747 ng/l. The maximum value generated in the (upstream part of the) catchment is 627 ng/l and for the lower part, 747 ng/l. Thus, the templates did catch the maximum concentration of the PestSurf simulation.

Table 12.9. Maximum concentrations (ng/l) of tribenuron methyl simulated for selected calculation point in the sandy loam catchment.
Tabel 12.9. Maximums koncentrationer (ng/l) af tribenuron-methyl for udvalgte lokaliteter i morænelersoplandet.

Click here to see Table 12.9.

Click here to see Figure 12.23.

Figure 12.23. Overview for tribenuron methyl in the sandy loam catchment generated by the PestSurf excel template for the upstream part of the catchment. The detection value was set to 1 ng/l.
Figur 12.23. Oversigt for tribenuron-methyl genereret med PestSurf-excel-skabelonen for den opstrøms del af morænelers-oplandet. Detektionsgrænsen var sat til 1 ng/l.

Click here to see Figure 12.24.

Figure 12.24. Overview for tribenuron methyl in the sandy loam catchment generated by the PestSurf excel template for the downstream part of the catchment. The detection value was set to 1 ng/l.
Figur 12.24. Oversigt for tribenuron-methyl genereret med PestSurf-excel-skabelonen for den nedstrøms del af morænelers-oplandet. Detektionsgrænsen var sat til 1 ng/l.

Table 12.10. Part of the result sheet generated by the PestSurf Excel sheet for the upstream part of the sandy loam catchment. The lowest detection value is for generation of the table is 1 ng/l, toxicity to fish, daphnies and algae are set to 5, 10 and 100 ng/, respectively. The recorded peaks are shown in Figure 12.23.
Tabel 12.10. Uddrag af resultatpresentationen genereret af PestSurf-Excel-arket for den opstrøms del af morænelersoplandet. Detektionsgrænsen for tabelgenerering er 1 ng/l. Toxicitetsværdierne for fisk, dafnier og alger er henholdsvis 5, 10 og 100 ng/l. Hændelserne er vist i Figur 12.23.

Click here to see Table 12.10.

Table 12.11. Part of the result sheet generated by the PestSurf Excel sheet for the downstream part of the sandy loam catchment. The lowest detection value for generation of the table is 1 ng/l, toxicity to fish, daphnies and algae are set to 5, 10 and 100 ng/, respectively. The recorded peaks are shown in Figure 12.24.
Tabel 12.11. Uddrag af resultatpresentationen genereret af PestSurf-Excel-arket for den nedstrøms del af morænelersoplandet. Detektionsgrænsen for tabelgenerering er sat til 1 ng/l. Toxicitetsværdierne for fisk, dafnier og alger er henholdsvis5, 10 og 100 ng/l. Hændelserne er vist i Figur 12.24.

Click here to see Table 12.11.

12.4.4 Sandy loam catchment, pond

The concentration pattern is evaluated in the middle of the pond only, see Figure 12.25. The pond receives contributions mainly through drift, in good correspondence with the fact that it is situated in the upper part of the sandy loam catchment. However, some drainage contributions are visible in the wet periods. The maximum concentration is quite low, 10.3 ng/l.

Figure 12.25. Concentrations of tribenuron methyl for the sandy loam pond.
Figur 12.25. Koncentration af tribenuron-methyl i morænelersvandhullet.

Figure 12.26. Tribenuron methyl sorbed to the macrophytes in the sandy loam pond.
Figur 12.26. Tribenuron-methyl sorberet til makrofytter i morænelers-vandhullet.

Figure 12.26 shows that the macrophytes participate in the regulation of the concentrations in the pond. The concentrations on macrophytes and in the water phase are comparable. The concentration in the porewater is shown in Figure 12.27. The adsorption to sediment is <0.01 ng/kg.

Figure 12.27. Tribenuron methyl in porewater in the sandy loam pond.
Figur 12.27. Tribenuron-methyl i porevand i morænelersvandhullet.

In Table 12.12, global maxima and time weighted concentrations (up to 7 days) were extracted.

Table 12.12. Actual and time weighted concentrations (ng/l) of tribenuron methyl in the sandy loam pond.
Tabel 12.12. Beregnede og tidsvægtede koncentrationer (ng/l) af tribenuron-methyl i morænelersvandhullet.

The FOCUS SW-scenario D4-pond generates a concentration of 3 ng/l, which is in the same order of magnitude as the PestSurf sandy loam pond-concentration of 10 ng/l. Both maximum concentrations are generated through drift. The difference between the results of the two models is partly due to the higher exposure of the the PestSurf sandy loam pond and the fact that the water depth at the time of spraying is 0.75 cm.

With respect to sediment, the D4-scenario reaches 2 ng/kg while PestSurf predicts values < 0.01 ng/kg.

Figure 12.28 and Table 12.13 show output from the PestSurf template, with a time series identical to Figure 12.25.

Click here to see Figure 12.28.

Figure 12.28. Overview for Tribenuron in the sandy loam pond generated by the PestSurf excel template. The time series shown is identical to the one in Figure 12.25. The detection value used is 1 ng/l.
Figur 12.28. Oversigt for tribenuron-methyl i morænelersvandhullet genereret med PestSurf-excel-skabelonen. Den viste tidsserie er mage til den i Figur 12.25. Detektionsgrænsen er sat til 1 ng/l.

Table 12.13. Part of the result sheet generated by the PestSurf Excel sheet. The limiting value is set to 1 ng/l. The toxicity values for fish, daphnies and algae were set to 2, 10 and 100 ng/l, respectively. The recorded peaks are shown in Figure 12.28.
Tabel 12.13. Uddrag af resultatpresentationen genereret af PestSurf-Excel-arket. Detektionsgrænsen er sat til 1 ng/l. Toxicitetsværdierne for fisk, dafnier og alger er henholdsvis 2, 10 og 100 ng/l. De tabellerede hændelser er vist i Figur 12.28.

Click here to see Table 12.13.

Table 12.14. Summary of simulation results for tribenuron methyl.
Tabel 12.14. Opsummerede resultater for tribenuron-methyl.

Click here to see Table 12.14.

12.5 Summary of simulations

The maximum actual concentrations for all simulations are recorded in Table 12.14.

The concentrations generated for the sandy pond and stream are about a factor 3 higher than the concentrations generated for the FOCUS SW D3-ditch. The pond is influenced by groundwater, while the D3-ditch and the sandy stream are influenced by wind drift. The high concentration generated in the stream is caused by the fact that the total agricultural area is sprayed within 30 minutes. However, 112 m from the upstream end, the concentration only reaches 10 ng/l, which is considerably less than what is found in the D3-ditch (95 ng/l). The low concentration in PestSurf, however, is due to a combination of a 20 m wide buffer zone and a water depth at the time of maximum concentration of 13-14 cm.

The FOCUS SW D4-pond and the PestSurf sandy loam pond differ by a factor of 3. The diffence is caused by the higher exposure of the sandy loam pond and a lower water level during the dry year of the simulation.

With respect to the D4-stream and the sandy loam stream, FOCUS SW generates 76 ng/l while PestSurf generates 747 ng/l. Both models generate the maximum concentrations through wind drift. However, some drainage contribution does take place in the sandy loam stream. The high concentrations in PestSurf are generated due to accumulation of drift contributions along the stream. 125 m from the upstream end, the concentration reaches 553 ng/l. The water depth at the time of maximum concentration is around 4.8 cm. This, and the fact that the PestSurf stream is triangular, accounts for the difference between the two models.

The maximum value obtained between 500 and 1700 m from the upstream end is 390 ng/l.

Macrophytes influence the concentrations, particularly in the sandy loam pond, but to some extent also in the sandy loam stream.

With respect to sediment concentrations, the maximum value generated by FOCUS is 11 ng/kg and the maximum value generated by PestSurf 3.1 ng/kg. PestSurf values are consistently lower than the FOCUS-SW-values but both models results in low sorption values.

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Version 1.0 December 2006, © Danish Environmental Protection Agency