Abstract
Limited information is available on the risk to aquatic environments from the aerial application of copper fungicides to treat dothistroma needle blight in managed forests. Cuprous oxide was aerially applied to three catchments of Pinus radiata of varying age classes in the central North Island of New Zealand. Copper was monitored in stream water and sediments prior to and for 1 month after application. Copper deposits collected from tracer plates deployed above the water surface along the stream channels within the treated areas at each site ranged from 13 to 406 ppm. Lowest concentrations occurred above small stream channels with dense overhead riparian vegetation. Peak copper concentrations in stream water across the three sites ranged from 28 to 60 μg L−1 and were below the analytical detection limit within hours. Copper concentrations were higher and persisted for longer in stream sediment (range 1.7–6.1 mg kg−1, sampled at two sites only). Copper concentrations in sediments were below environmental guidelines. Copper concentrations in water and sediment indicated a low risk to aquatic organisms based on the exposure times to the concentrations measured in this study.
Highlights
Copper is a naturally occurring metallic element found in the earth’s crust and is an essential trace element required in very small quantities to support the functioning of biological systems of all living organisms
Regardless of the tree age, stream size, stream flow, riparian composition, flight line direction, or leaving a Bno spray^ buffer along the stream edge, copper was detected in the stream water for a short duration at all three sites on the day of copper application
Given that a Bspray drift^ method is used to facilitate the penetration of copper into the infected stands, along stand edges
Summary
Copper is a naturally occurring metallic element found in the earth’s crust and is an essential trace element required in very small quantities to support the functioning of biological systems of all living organisms. Both deficient and excess concentrations of copper in the environment can be harmful (Environmental Protection Agency 2007; Soetan et al 2010; Kiaune and Singhasemanon 2011). A number of reports have highlighted the increasing prevalence of the disease and an increase in the severity of outbreaks (Barnes et al 2008; Welsh et al 2009; Barnes et al 2014), in the northern hemisphere forests which authors suggest may be attributable to underlying changes in weather patterns (Welsh et al 2014; Woods et al 2016)
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