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The longest total flow distance for mobilized pesticides between the closest cultivation plot edge and the POCIS sampling station was 187 m for diazinon (Station ID: 020d) and 42 m for carbofuran (Station ID:008d) (Table 4). The positive sampling stations with the longest flow distances between the cultivation plot and the sampling station also correspond with larger drainage areas than other detections with 0.43 km2 (Station ID: 020d) and 2.03 km2 (Station ID: 008d) for diazinon and carbofuran, respectively. All downstream diazinon-positive sampling stations occurred where upstream drainage areas fell within the lower quartile compared to all downstream sampling stations (Figure 3). The area draining to the downstream sampling station where carbofuran was detected was approximately equal to the median of all downstream sampling stations.
Table 4

POCIS summary for deployments and sampling stations where laboratory analysis confirmed soluble pesticides

Station IDNational forestOverland flow distance (m)In-stream flow distance (m)Deployment duration (days)Time since eradication (days)Drainage area (km2)Result
007d Six Rivers 68.36 44.66 44 102 0.27 Diazinon 
008d Plumas 4.37 37.54 181 92 2.03 Carbofuran 
020d Shasta-Trinity 24.29 162.36 38 91 0.43 Diazinon 
026d Six Rivers 75.52 101.18 36 104 0.13 Diazinon 
036u Eldorado n.a. n.a. 56 496 0.28 Carbofuran 
Station IDNational forestOverland flow distance (m)In-stream flow distance (m)Deployment duration (days)Time since eradication (days)Drainage area (km2)Result
007d Six Rivers 68.36 44.66 44 102 0.27 Diazinon 
008d Plumas 4.37 37.54 181 92 2.03 Carbofuran 
020d Shasta-Trinity 24.29 162.36 38 91 0.43 Diazinon 
026d Six Rivers 75.52 101.18 36 104 0.13 Diazinon 
036u Eldorado n.a. n.a. 56 496 0.28 Carbofuran 

Overland and in-stream flow distances represent the minimum downslope flow distance between the nearest cultivation plot edge and the sampling station. All positive detections were recorded during only one sampling deployment and tested negative during subsequent deployments.

Figure 3

Box plot of the area draining to all polar organic chemical integrative sampling stations deployed both up- and downstream of trespass cannabis cultivation complexes as part of the microscale study. Sampling stations where diazinon was detected are indicated by red triangles and carbofuran-positive sampling stations by black diamonds. Please refer to the online version of this paper to see this figure in colour: http://dx.doi.org/10.2166/wqrj.2022.101.

Figure 3

Box plot of the area draining to all polar organic chemical integrative sampling stations deployed both up- and downstream of trespass cannabis cultivation complexes as part of the microscale study. Sampling stations where diazinon was detected are indicated by red triangles and carbofuran-positive sampling stations by black diamonds. Please refer to the online version of this paper to see this figure in colour: http://dx.doi.org/10.2166/wqrj.2022.101.

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