A significant watershed-based research and demonstration program is underway to address the problems of small Quebec freshwater lakes impacted by cyanobacteria blooms. These blooms are causing loss of the lakes for recreation, habitat and water supply, and the presence of cyanotoxins is viewed as a public health threat. The program is centered on one template lake and the sustainable control of the responsible nutrients (mainly phosphorus) at their source. Agricultural activities have been identified as significant loading sources and are the focus of the first phase of this work. Unactivated pyrolytic carbon (termed biochar) is one potential controlling agent to reduce the nutrient content of agricultural runoff. The use of sorptive media for interception and filtration in-stream and at agricultural return flow (IRF) outlets is also being investigated. To examine the effectiveness of biochar, an initial field trial was conducted in 2008, where amended and control fields were evaluated for crop productivity as an indirect indicator of drainage quality. Preliminary results indicate that plant yields were substantially increased in the amended fields (by approximately 20%), with root length increases of up to 60%. Most nutrient depletion and water infiltration rates were lower in the amended fields; these results provide indirect evidence that the native and applied nutrients are being held longer in the soil and are more available for uptake. A second trial in these same fields is currently underway, together with a comprehensive laboratory biochar characterization program to quantify the effectiveness of this sustainable material for nutrient source control. In parallel, in-stream and IRF outlet filtration units have been placed based on a laboratory characterization and selection process. System design and current results from this program are presented, in support of the role of these innovative materials for watershed-based source control of nutrient loadings to address this emerging problem.
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