Fate and transport of copper-based crop protectants in plasticulture runoff and the impact of sedimentation as a best management practice

The fate and distribution of copper-based crop protectants. applied to pl:p lasticulture tomato fields to protect against disease. were investigated in a greenhouse-scale simulation of farming conditions in a coastal environme nt. Following rainfall. 99% of the applied copper was found to remain on th e fields sorbed to the soil and plants: most of the suit-bound copper was f ound sorbed to the top 2.5 cm of soil between the plasticulture rows. Of th e copper leaking the agricultural fields. 82% was found in tile runoff with the majority, 74%, sorbed to the suspended solids. The remaining copper, 1 8%, leuched through the soil and entered the groundwater with 10%: in the d issolved phase anti 8% sorbed to suspended solids. Although only 1% copper was found to leave the held, this was sufficient to cause high copper conce ntrations (average 2102 +/- 433 mug/L total copper and 189 +/- 139 mug L di ssolved copper) in the runoff. Copper concentrations in groundwater samples were also high (average 312 +/- 198 mug L total copper and 216 +/- 99 mug/ L dissolved copper). Sedimentation, a best management practice for reducing copper loadings. was found to reduce the total copper concentrations in ru noff by 90% to a concentration of 245 +/- 127 mug/L L; however, dissolved c opper concentrations remained stable, averaging 139 +/- 55 mug L. Total cop per concentrations were significantly reduced by the effective removal of s uspended solids with sorbed copper. (C) 2001 Elsevier Science Ltd. All righ ts reserved.