Copper-based algaecides and herbicides are commonly used in aquatic systems to control problematic algae and weeds leading to concerns of copper accumulation at application sites. In spite of this accumulation, algaecides and herbicides are still applied routinely throughout the year and, therefore, create an environmental concern. Excessive amounts of copper are toxic to fish and other aquatic organisms as well as affect microbial metabolic activities in aquatic sediments. For this study, water and sediment were collected from two central Florida lakes that have had monthly treatments of copper-based pesticides for the past seven years. Control samples were collected at an untreated lake. Sequential extraction of sediments was conducted to determine the concentration and chemical speciation of copper in sediments with depth. Samples were taken seasonally and the average concentration of copper was determined by inductively coupled plasma mass spectrometry (ICP-MS). Preliminary results indicated that copper concentrations increased with depth in the sediment of treated lakes with highest concentrations in the 6 – 10 cm depth fraction. Speciation experiments determined that copper was primarily associated with the organic fraction. Copper was also present in the adsorbed and precipitated fractions, confirming thermodynamic models of copper speciation. In contrast, control lake sediments contained lower total copper concentrations and did not exhibit changes in depth. The results of this study will elucidate the fate of copper from pesticides in aquatic environmental systems.

Accumulation of copper in sediments of lakes treated with copper-based pesticides

255th National Meeting (2018)

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