A New Technique to Determine the Phosphate Oxygen Isotope Composition of Freshwater Samples at Low Ambient Phosphate Concentration

The oxygen isotope composition of dissolved inorganic phosphate (d18Op) offers new opportunities to understand the sources and the fate of phosphorus (P) in freshwater ecosystems. However, current analytical protocols for determining d18Op are unable to generate reliable data for samples in which ambient P concentrations are extremely low, precisely the systems in which d18Op may provide new and important insights into the biogeochemistry of P. In this paper, we report the development, testing and initial application of a new technique that enables d18Op analysis to be extended into such ecosystems. The Twist Spinning Mode (TSM) protocol described here enables >1000 L of sample with a P concentration <0.016 mg P L-1 to be initially processed within the field in approximately 24 hours. Combined with a new freeze-drying method to maximise the yield and minimise the contamination of silver phosphate generated for isotope ratio mass spectrometry, the TSM protocol is able to generate accurate and precise d18Op data. We evaluated the TSM protocol using synthetic test solutions and subsequently applied the protocol to samples from locations around the Saint-Lawrence River in Montreal, Canada. We believe that the novel technique reported here offers the methodological basis for researchers to extend the application of d18Op into a much wider range of freshwater ecosystems than has been possible to date

The net carbon footprint of a newly created boreal hydroelectric reservoir

We present here the first comprehensive assessment of the carbon (C) footprint associated with the creation of a boreal hydroelectric reservoir (Eastmain-1 in northern Québec, Canada). This is the result of a large-scale, interdisciplinary study that spanned over a 7-years period (2003–2009), where we quantified the major C gas (CO2 and CH4)sources and sinks of the terrestrial and aquatic components of the pre-flood landscape, and also for the reservoir following the impoundment in 2006. The pre-flood landscape was roughly neutral in terms of C, and the balance between pre- and post-flood C sources/sinks indicates that the reservoir was initially (first year post-flood in 2006) a large net source of CO2 (2270 mg C m-2 d-1) but a much smaller source of CH4 (0.2 mg C m-2 d-1). While net CO2 emissions declined steeply in subsequent years (down to 835 mg C m-2 d-1 in 2009), net CH4 emissions remained constant or increased slightly relative to pre-flood emissions. Our results also suggest that the reservoir will continue to emit carbon gas over the long-term at rates exceeding the carbon footprint of the pre-flood landscape, although the sources of C supporting these emissions have yet to be determined. Extrapolation of these empirical trends over the projected life span (100 years) of the reservoir yields integrated long-term net C emissions per energy generation well below the range of the natural-gas combined-cycle, which is considered the current industry standard.status: publishe