Understanding Fate and Effects of Copper Pesticides in Aquatic Systems

Copper sulfate and other chelated or complex copper forms are commonly used to manage nuisance and noxious algae and invasive weeds through direct application to aquatic systems. Regulatory scrutiny and perceived non-target species impacts supported the need for an accurate risk assessment of fate and effects of copper applied as a pesticide. Copper inputs to aquatic systems originate from numerous sources (e.g. natural, storm water, industrial) whereas direct pesticide applications account for approximately 13%. Following a pesticide application, copper rapidly partitions to suspended algae and particulates and the majority (>90%) of applied copper is transferred to sediments within 2 days. Copper subsequently shifts to less bioavailable forms and risks to non-target species are significantly decreased. Additionally, the copper that partitions to sediments is diluted through migration to greater sediments depths and accretion. Even when elevated sediment copper concentrations were measured following chronic applications or high treatment levels, no adverse effects to non-target species were observed with laboratory or field experiments. When used appropriately copper can be an effective tool for water resource managers with negligible environmental impact.