Monitoring results 1999 - 2010

Highlights from monitoring period 2009-2010 where 6 pesticides were applied, show that:

• Bifenox acid (degradation product of bifenox) can on loamy soil leach through the root zone and enter both drainage water system and groundwater monitoring wells in concentrations exceeding 0.1 μg/l. Average concentration in the drainage water exceeded 0.1 μg/l and concentrations exceeding 0.1 μg/l were observed up to six months after application. Similar evidence of pronounced leaching was not observed on the coarse sandy soil as there was only a single detection of bifenox acid in soil water, whereas bifenox was detected very sporadically in soil and groundwater, concentrations always less than 0.1 μg/l.
• Ethofumesate, this year used in a new admissible dose that is five times lower than in past applications, was detected once in groundwater, concentrations at less than 0.1 μg/l. When, in the past (before the imposed regulation), ethofumesate was used at a much higher dose, leaching above 0.1 μg/l to both drains and groundwater monitoring wells was observed.
• Metamitron, this year (2009) used in the maximum allowed dosage and previous year (2008) in a dose 33% lower than the permitted, did not cause leaching above 0.1 μg/l of neither metamitron nor its metabolite metamitron–desamino. This leaching pattern differs from previous observations (2000, 2001 and 2003) where metamitron, used at maximum allowed dose, together with its metabolite metamitron-desamino leached above 0.1μg/l to both drains and groundwater monitoring wells.
  
• The leaching pattern of the remaining three pesticides (bentazone, azoxystrobin, triasulfuron) was in line with the previous observations (outlined below).

• Of the 42 pesticides applied, 11 pesticides and/or their degradation product(s) (clopyralid, chlormequat, desmedipham, fenpropimorph, florasulam, iodosulfuron-methyl-sodium, linuron, metsulfuron-methyl, thiamethoxam, tribenuron-methyl, and triasulfuron) did not leach during the entire monitoring period.
• The monitoring data indicate pronounced leaching of 14 of the applied pesticides and/or their degradation products. The following compounds leached through the soil entering drains and suction cups (placed 1 m b.g.s) in average concentrations exceeding 0.1 μg/l:
  • azoxystrobin and its degradation product CyPM,
  • bentazone
  • CL153815 (degradation product of picolinafen)
  • pirimicarb-desmethyl-formamido (degradation product of pirimicarb)
  • propyzamide
  • tebuconazole
  • glyphosate and its degradation product AMPA
  • PPU (degradation products of rimsulfuron)
  • Bifenox acid (degradation product of bifenox)
  • ethofumesate
  • TFMP (degradation product of fluazifop-P-butyl)
  • metamitron and its degradation product metamitron-desamino
  • metribuzin-desamino-diketo and metribuzin-diketo (degradation products of metribuzin)
  • terbuthylazine and its degradation products: desethyl-terbuthylazine, 2-hydroxy-desethyl-terbuthylazine, and 2-hydroxy-terbuthylazine
• For the pesticides and/or their degradation products marked in Italics, pronounced leaching is mainly confined to the depth of 1 meter, where pesticides were frequently found in samples collected from drains and suction cups, while a limited number of detections (fewer than 5 samples per field) exceeding 0.1 μg/l were found in groundwater monitoring wells. For the pesticides and/or their degradation products marked in bold, pronounced leaching below the depth of 1 m was observed. Apart from PPU, these were all frequently detected in concentrations exceeding 0.1 μg/l in groundwater monitoring wells, exceedance of 0.1 μg/l being observed more than six months after application. Although PPU was only detected in a few samples in concentrations exceeding 0.1 μg/l, elevated concentrations just below 0.1 μg/l were found in groundwater monitoring wells during a twoyear period, thus confirming the pronounced leaching and high persistency of PPU in soil and groundwater. Repeated applications of PPU may thus pose a contamination risk of the shallow groundwater. Moreover, for the glyphosate being frequently applied on one loamy soil, detections in groundwater monitoring wells have gradually increased over time. On two occasions heavy rain events and snowmelt induced leaching to the groundwater monitoring wells in concentrations exceeding 0.1 μg/l more than two years after the application.
• The monitoring data also indicate leaching of an additional 17 pesticides, but in low concentrations. Although concentrations exceeded 0.1 μg/l in several samples collected from suction cups and drains (1 m b.g.s.), average leaching concentrations on a yearly basis did not. None of the compounds were found in groundwater monitoring wells in concentrations exceeding 0.1 μg/l.

In order to describe water transport, a bromide tracer was 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 covers the period May 1999–June 2010 and presents the monitoring results from the five agricultural sites presently monitored. The main focus is on evaluating the leaching risk of the pesticides applied during 2008.