Remediation of metalaxyl, trifluralin, and nitrate from nursery runoff using container-grown woody ornamentals and phytoremediation areas

Two commonly container-produced woody ornamentals, Salix alba L. ‘Britzensis’ and Sambucus nigra L. ‘Aurea’, were grown in aquatic phytoremediation areas (PAs) to evaluate phytoremediation of trifluralin (2004 and 2005), metalaxyl (2006), and NO₃ ⁻–N (2004–2006) from nursery runoff. The use of container-grown ornamentals for phytoremediation would prevent land area used in production from being converted into wetlands or vegetated filter strips. Twelve nursery beds (NBs) were constructed and graded to allow runoff collection in a small basin at the west end of each production area. Runoff from each NB drained into a PA that contained one of three treatments: (1) 20 plants of S. alba ‘Britzensis’ grown in containers, (2) 20 plants of S. nigra Aurea’ grown in containers, or (3) a PA with no containers and plants serving as a control. Samples of runoff from NBs and water leaving PAs were collected for trifluralin or metalaxyl and NO₃ ⁻–N analysis. Phytoremediation areas with container-grown plants remediated trifluralin, metalaxyl, and NO₃ ⁻–N in runoff water to the same extent as PAs without plants. When data from all treatments were pooled and water exiting PAs was compared to runoff from NBs, PAs were effective in remediating runoff. In 2004 and 2005, overall average trifluralin quantity was reduced by 72% (7.32±0.67mg to 2.03±0.29mg) and 94% (from 7.81±0.86mg to 0.51±0.07mg) as runoff moved through PAs. The overall average metalaxyl quantity was reduced by 48% (34.32±7.98mg to 17.69±2.78mg) as runoff moved through PAs. Nitrate–nitrogen quantities leaving PAs were the same or lower compared to NO₃ ⁻–N captured from NBs depending on sample day, with the greatest reduction of 98% (373–6.00mg) on 14 July 2006. Plants grown in PAs reached marketable size during the experiment. Using PAs with or without container-grown plants as a component of the PA system would reduce environmental contamination from runoff containing metalaxyl, trifluralin, and NO₃ ⁻–N, and would reduce harmful effects to aquatic organisms from runoff containing trifluralin or NO₃ ⁻–N.