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Carbon dioxide evasion from inland waters such as lakes, rivers and streams represents a significant component of the global carbon cycle, yet in many parts of the world, relatively little is known about its source. Radiocarbon dating of aquatic CO2 has the potential to provide new insights into C cycling in the terrestrial-aquatic-atmosphere continuum, and whilst a range of methods are available for the collection of samples for 14C analysis, they all have limitations or disadvantages (e.g. slow collection rates and potential non-equilibrium). These issues are further compounded in remote field sites. Here, we describe a new method for the field collection of CO2 samples from low-pH waters (pH < 7) for radiocarbon analysis, which involves a scaled-up version of the widely used headspace equilibration technique coupled with syringe injection of samples into molecular sieve traps for convenient and stable storage. We present the results of laboratory and field tests to verify this 'super headspace method' and discuss its advantages compared with existing techniques, particularly for sampling in remote locations. This includes its high portability, speed of use and absence of any special sample preservation requirements. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Peatland streams typically contain high methane concentrations and act as conduits for the release of this greenhouse gas to the atmosphere. Radiocarbon analysis provides a unique tracer that can be used to identify the methane source, and quantify the time elapsed between carbon fixation and return to the atmosphere as CH4. Few studies - those that have focus largely on sites with bubble (ebullition) emissions - have investigated the 14C age of methane in surface waters because of the difficulty in collecting sufficient CH4 for analysis. Here, we describe new sampling methods for the collection of CH4 samples from CH4-oversaturated peatland streams for radiocarbon analysis. We report the results of a suite of tests, including using methane 14C standards and replicated field measurements, to verify the methods. The methods are not restricted to ebullition sites, and can be applied to peatland streams with lower methane concentrations. We report the 14C age of methane extracted from surface water samples (~4-13 l) at two contrasting locations in a temperate raised peat bog. Results indicate substantial spatial variation with ages ranging from ~400 (ditch in afforested peatland) to ~3000 years BP (bog perimeter stream). These contrasting ages suggest that methane in stream water can be derived from a wide range of peat depths. This new method provides a rapid (10-15 min per sample) and convenient approach, which should make 14CH4 dating of surface water more accessible and lead to an increased understanding of carbon cycling within the soil-water-atmosphere system. © 2015 The Authors. Ecohydrology published by John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]