Beryllium-7 wet deposition variation with storm height, synoptic classification, and tree canopy state in the mid-Atlantic USA

This is the peer reviewed version of the article which has been published in final form at 10.1002/hyp.10571. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving: http://olabout.wiley.com/WileyCDA/Section/id-820227.html#termsShort-lived fallout isotopes, such as beryllium-7 (7Be), are increasingly used as erosion and sediment tracers in watersheds. Beryllium-7 is produced in the atmosphere and delivered to Earth's surface primarily in precipitation. However, relatively little has been published about the variation in 7Be wet deposition caused by storm type and vegetation cover. Our analysis of precipitation, throughfall, and sediments in two forested, headwater catchments in the mid-Atlantic USA indicates significant variation in isotope deposition with storm type and storm height. Individual summer convective thunderstorms were associated with 7Be activity concentrations up to 5.0 Bq L−1 in precipitation and 4.7 Bq L−1 in throughfall while single-event wet depositional fluxes reached 168 Bq m−2 in precipitation and 103 Bq m−2 in throughfall. Storms originating from the continental USA were associated with lower 7Be activity concentrations and single-event wet depositional fluxes for precipitation (0.7 – 1.2 Bq L−1 and 15.8 – 65.0 Bq m−2) and throughfall (0.1 – 0.3 Bq L−1 and 13.5 – 98.9 Bq m−2). Tropical systems had relatively low activity concentrations, 0.2 – 0.5 Bq L−1 in precipitation and 0.2 – 1.0 Bq L−1 in throughfall, but relatively high single-event depositional fluxes due to large rainfall volumes, 32.8 – 67.6 Bq m−2 in precipitation and 25.7 – 134 Bq m−2 in throughfall. The largest sources of 7Be depositional variation were attributed to storm characteristics including precipitation amount and maximum storm height. 7Be activity associated with fluvial suspended sediments also exhibited the highest concentration and variability in summer (175 – 1450 Bq kg−1). We conclude the dominant source of variation on event-level 7Be deposition is storm type. Our results illustrate the complex relationships between 7Be deposition in precipitation and throughfall and demonstrate event-scale relationships between the 7Be in precipitation and on suspended sediment.National Science Foundatio

Low-Cost, Open-Source, and Low-Power: But What to Do With the Data?

There are now many ongoing efforts to develop low-cost, open-source, low-power sensors and datalogging solutions for environmental monitoring applications. Many of these have advanced to the point that high quality scientific measurements can be made using relatively inexpensive and increasingly off-the-shelf components. With the development of these innovative systems, however, comes the ability to generate large volumes of high-frequency monitoring data and the challenge of how to log, transmit, store, and share the resulting data. This paper describes a new web application that was designed to enable citizen scientists to stream sensor data from a network of Arduino-based dataloggers to a web-based Data Sharing Portal. This system enables registration of new sensor nodes through a Data Sharing Portal website. Once registered, any Internet connected data-logging device (e.g., connected via cellular or Wi-Fi) can then post data to the portal through a web service application programming interface (API). Data are stored in a back-end data store that implements Version 2 of the Observations Data Model (ODM2). Live data can then be viewed using multiple visualization tools, downloaded from the Data Sharing Portal in a simple text format, or accessed via WaterOneFlow web services for machine-to-machine data exchange. This system was built to support an emerging network of open-source, wireless water quality monitoring stations developed and deployed by the EnviroDIY community for do-it-yourself environmental science and monitoring, initially within the Delaware River Watershed. However, the architecture and components of the ODM2 Data Sharing Portal are generic, open-source, and could be deployed for use with any Internet connected device capable of making measurements and formulating an HTTP POST request

Annual variability in the radiocarbon age and source of dissolved CO2 in a peatland stream

Radiocarbon dating has the capacity to significantly improve our understanding of the aquatic carbon cycle. In this study we used a new passive sampler to measure the radiocarbon (14C) and stable carbon (δ13C) isotopic composition of dissolved CO2 for the first time in a peatland stream throughout a complete year (May 2010 – June 2011). The in-stream sampling system collected time-integrated samples of CO2 continuously over approximately one month periods. The rate of CO2 trapping was proportional to independently measured streamwater CO2 concentrations, demonstrating that passive samplers can be used to estimate the time-averaged dissolved CO2 concentration of streamwater. While there was little variation and no clear trend in δ13CO2 values (suggesting a consistent CO2 source), we found a clear temporal pattern in the 14C concentration of dissolved CO2. The 14C age of CO2 varied from 707±35 to 1210±39 years BP, with the youngest CO2 in the autumn and oldest in spring/early summer. Mean stream discharge and 14C content of dissolved CO2 were positively correlated. We suggest that the observed pattern in the 14C content of dissolved CO2 reflects changes in its origin, with older carbon derived from deeper parts of the peat profile contributing proportionally more gaseous carbon during periods of low stream flow

The biogeochemistry of carbon across a gradient of streams and rivers within the Congo Basin

Dissolved organic carbon (DOC) and inorganic carbon (DIC and pCO2), lignin biomarkers and the optical properties of dissolved organic matter (DOM) were measured in a gradient of streams and rivers within the Congo Basin (Republic of Congo), with the aim of examining how vegetation cover and hydrology influences the composition and concentration of exported fluvial carbon (C). Three sampling campaigns (February 2010, November 2010 and August 2011) spanning 56 sites are compared by sub-basin watershed land cover type (savannah, tropical forest, and swamp) and hydrologic regime (high, intermediate, and low). Land cover properties predominately controlled the amount and quality of DOC, chromophoric DOM (CDOM) and lignin phenol concentrations (∑8) exported in streams and rivers throughout the Congo Basin. Higher DIC concentrations and changing DOM composition (lower molecular weight, less aromatic C) during periods of low hydrologic flow indicated a shift from rapid overland supply pathways in wet conditions to deeper groundwater inputs during drier periods. Lower DOC concentrations in forest and swamp sub-basins were apparent with increasing catchment area, indicating enhanced DOC loss with extended water residence time. Surface water pCO2 in savannah and tropical forest catchments ranged between 2600 and 11922 µatm, and swamp regions contained extremely high pCO2 (10598-15802 µatm), highlighting their potential as significant pathways for water-air efflux. Our data suggest that the quantity and quality of DOM exported to streams and rivers is largely driven by terrestrial ecosystem structure and that anthropogenic land-use or climate change may impact the composition and reactivity of fluvial C, with ramifications for regional C budgets and future climate scenarios

Photochemical Degradation of Dissolved Organic Matter and Dissolved Lignin Phenols from the Congo River

Photochemical degradation of Congo River dissolved organic matter (DOM) was investigated to examine the fate of terrigenous DOM derived from tropical ecosystems. Tropical riverine DOM receives greater exposure to solar radiation, particularly in large river plumes discharging directly into the open ocean. Initial Congo River DOM exhibited dissolved organic carbon (DOC) concentration and compositional characteristics typical of organic rich blackwater systems. During a 57 day irradiation experiment, Congo River DOM was shown to be highly photoreactive with a decrease in DOC, chromophoric DOM (CDOM), lignin phenol concentrations (Σ8) and carbon-normalized yields (Λ8), equivalent to losses of ~45, 85–95, \u3e95 and \u3e95% of initial values, respectively, and a +3.1 % enrichment of the δ13C-DOC signature. The loss of Λ8 and enrichment of δ13C-DOC during irradiation was strongly correlated (r = 0.99, p \u3c 0.01) indicating tight coupling between these biomarkers. Furthermore, the loss of CDOM absorbance was correlated to the loss of Λ8 (e.g., a355 versus Λ8; r = 0.98, p \u3c 0.01) and δ13C-DOC (e.g., a355 versus δ13C; r = 0.97, p \u3c 0.01), highlighting the potential of CDOM absorbance measurements for delineating the photochemical degradation of lignin and thus terrigenous DOM. It is apparent that these commonly used measurements for examination of terrigenous DOM in the oceans have a higher rate of photochemical decay than the bulk DOC pool. Further process-based studies are required to determine the selective removal rates of these biomarkers for advancement of our understanding of the fate of this material in the ocean

Radiocarbon dating of methane and carbon dioxide evaded from a temperate peatland stream

Streams draining peatlands export large quantities of carbon in different chemical forms and are an important part of the carbon cycle. Radiocarbon (14C) analysis/dating provides unique information on the source and rate that carbon is cycled through ecosystems, as has recently been demonstrated at the air-water interface through analysis of carbon dioxide (CO2) lost from peatland streams by evasion (degassing). Peatland streams also have the potential to release large amounts of methane (CH4) and, though 14C analysis of CH4 emitted by ebullition (bubbling) has been previously reported, diffusive emissions have not. We describe methods that enable the 14C analysis of CH4 evaded from peatland streams. Using these methods, we investigated the 14C age and stable carbon isotope composition of both CH4 and CO2 evaded from a small peatland stream draining a temperate raised mire. Methane was aged between 1617-1987 years BP, and was much older than CO2 which had an age range of 303-521 years BP. Isotope mass balance modelling of the results indicated that the CO2 and CH4 evaded from the stream were derived from different source areas, with most evaded CO2 originating from younger layers located nearer the peat surface compared to CH4. The study demonstrates the insight that can be gained into peatland carbon cycling from a methodological development which enables dual isotope (14C and 13C) analysis of both CH4 and CO2 collected at the same time and in the same way

Riverine coupling of biogeochemical cycles between land, oceans, and atmosphere

Author Posting. © Ecological Society of America, 2011. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Frontiers in Ecology and the Environment 9 (2011): 53–60, doi:10.1890/100014.Streams, rivers, lakes, and other inland waters are important agents in the coupling of biogeochemical cycles between continents, atmosphere, and oceans. The depiction of these roles in global-scale assessments of carbon (C) and other bioactive elements remains limited, yet recent findings suggest that C discharged to the oceans is only a fraction of that entering rivers from terrestrial ecosystems via soil respiration, leaching, chemical weathering, and physical erosion. Most of this C influx is returned to the atmosphere from inland waters as carbon dioxide (CO2) or buried in sedimentary deposits within impoundments, lakes, floodplains, and other wetlands. Carbon and mineral cycles are coupled by both erosion–deposition processes and chemical weathering, with the latter producing dissolved inorganic C and carbonate buffering capacity that strongly modulate downstream pH, biological production of calcium-carbonate shells, and CO2 outgassing in rivers, estuaries, and coastal zones. Human activities substantially affect all of these processes.The US National Science Foundation (NSF) and the National Oceanographic and Atmospheric Administration (NOAA) provided funding for this work

Controls on the composition and lability of dissolved organic matter in Siberia's Kolyma River basin

High-latitude northern rivers export globally significant quantities of dissolved organic carbon (DOC) to the Arctic Ocean. Climate change, and its associated impacts on hydrology and potential mobilization of ancient organic matter from permafrost, is likely to modify the flux, composition, and thus biogeochemical cycling and fate of exported DOC in the Arctic. This study examined DOC concentration and the composition of dissolved organic matter (DOM) across the hydrograph in Siberia's Kolyma River, with a particular focus on the spring freshet period when the majority of the annual DOC load is exported. The composition of DOM within the Kolyma basin was characterized using absorbance-derived measurements (absorbance coefficienta330, specific UV absorbance (SUVA254), and spectral slope ratio SR) and fluorescence spectroscopy (fluorescence index and excitation-emission matrices (EEMs)), including parallel factor analyses of EEMs. Increased surface runoff during the spring freshet led to DOM optical properties indicative of terrestrial soil inputs with high humic-like fluorescence, SUVA254, and low SRand fluorescence index (FI). Under-ice waters, in contrast, displayed opposing trends in optical properties representing less aromatic, lower molecular weight DOM. We demonstrate that substantial losses of DOC can occur via biological (∼30% over 28 days) and photochemical pathways (>29% over 14 days), particularly in samples collected during the spring freshet. The emerging view is therefore that of a more dynamic and labile carbon pool than previously thought, where DOM composition plays a fundamental role in controlling the fate and removal of DOC at a pan-Arctic scale

Summer CO2 evasion from streams and rivers in the Kolyma River basin, north-east Siberia

Inland water systems are generally supersaturated in carbon dioxide (CO2) and are increasingly recognized as playing an important role in the global carbon cycle. The Arctic may be particularly important in this respect, given the abundance of inland waters and carbon contained in Arctic soils; however, a lack of trace gas measurements from small streams in the Arctic currently limits this understanding.We investigated the spatial variability of CO2 evasion during the summer low-flow period from streams and rivers in the northern portion of the Kolyma River basin in north-eastern Siberia. To this end, partial pressure of carbon dioxide (pCO2) and gas exchange velocities (k) were measured at a diverse set of streams and rivers to calculate CO2 evasion fluxes. We combined these CO2 evasion estimates with satellite remote sensing and geographic information system techniques to calculate total areal CO2 emissions. Our results show that small streams are substantial sources of atmospheric CO2 owing to high pCO2 and k, despite being a small portion of total inland water surface area. In contrast, large rivers were generally near equilibrium with atmospheric CO2. Extrapolating our findings across the Panteleikha-Ambolikha sub-watersheds demonstrated that small streams play a major role in CO2 evasion, accounting for 86% of the total summer CO2 emissions from inland waters within these two sub-watersheds. Further expansion of these regional CO2 emission estimates across time and space will be critical to accurately quantify and understand the role of Arctic streams and rivers in the global carbon budget