Burnett
William C.
Burnett
William C.
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ArticleClosing the global marine Ra-226 budget reveals the biological pump as a dominant removal flux in the upper ocean(American Geophysical Union, 2022-06-10) Xu, Bochao ; Cardenas, M. Bayani ; Santos, Isaac R. ; Burnett, William C. ; Charette, Matthew A. ; Rodellas, Valenti ; Li, Sanzhong ; Lian, Ergang ; Yu, ZhigangRadium isotopes are powerful proxies in oceanography and hydrology. Radium mass balance models, including assessments of submarine groundwater discharge (SGD), often overlook particle scavenging (PS) as a pathway for dissolved radium removal from the world ocean. Here, we build a global ocean 226Ra mass balance model and reevaluate the potential importance of PS. We find that PS is the major 226Ra sink for the upper ocean, removing about 96% of the total input from various sources. Aside from vertical exchange with the lower ocean, SGD is the largest 226Ra source into the upper ocean. The biological pump transfers particles to the deep ocean, resulting in a major but often overlooked impact on the global 226Ra marine budget. Our findings suggest that radium mass balance models should consider PS in systems with high siliceous algae production and export fluxes and long water residence times to prevent underestimation of large-scale SGD fluxes.
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PreprintReference material for radionuclides in sediment IAEA-384 (Fangataufa Lagoon sediment)( 2006-07-11) Povinec, Pavel P. ; Pham, Mai Khanh ; Sanchez-Cabeza, J. A. ; Barci-Funel, G. ; Bojanowski, R. ; Boshkova, T. ; Burnett, William C. ; Carvalho, Fernando ; Chapeyron, B. ; Cunha, I. L. ; Dahlgaard, H. ; Galabov, N. ; Fifield, L. K. ; Gastaud, J. ; Geering, J. -J. ; Gomez, I. F. ; Green, N. ; Hamilton, T. ; Ibanez, F. L. ; Ibn Majah, M. ; John, M. ; Kanisch, G. ; Kenna, Timothy C. ; Kloster, M. ; Korun, M. ; Liong Wee Kwong, L. ; La Rosa, J. ; Lee, S.-H. ; Levy-Palomo, I. ; Malatova, M. ; Maruo, Y. ; Mitchell, P. ; Murciano, I. V. ; Nelson, Robert K. ; Nouredine, A. ; Oh, J.-S. ; Oregioni, B. ; Le Petit, G. ; Pettersson, H. B. L. ; Reineking, A. ; Smedley, P. A. ; Suckow, A. ; van der Struijs, T. D. B. ; Voors, P. I. ; Yoshimizu, K. ; Wyse, E.A reference material designed for the determination of anthropogenic and natural radionuclides in sediment, IAEA-384 (Fangataufa Lagoon sediment), is described and the results of certification are presented. The material has been certified for 8 radionuclides (40K, 60Co, 155Eu, 230Th, 238U, 238Pu, 239+240Pu and 241Am). Information values are given for 12 radionuclides (90Sr, 137Cs, 210Pb (210Po), 226Ra, 228Ra, 232Th, 234U, 235U, 239Pu, 240Pu and 241Pu). Less reported radionuclides include 228Th, 236U, 239Np and 242Pu. The reference material may be used for quality management of radioanalytical laboratories engaged in the analysis of radionuclides in the environment, as well as for the development and validation of analytical methods and for training purposes. The material is available from IAEA in 100 g units.
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DatasetNumber of gene markers identified in sediment in samples from Little Lagoon, Alabama collected from 2012-2013.(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-03-15) Mortazavi, Behzad ; Burnett, William C.Number of gene markers identified in sediment in samples from Little Lagoon, Alabama collected from 2012-2013. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/723948
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DatasetDenitrification and DNRA data from Little Lagoon, Alabama collected from 2012-2013(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-03-15) Mortazavi, Behzad ; Burnett, William C.Denitrification and DNRA data from Little Lagoon, Alabama collected from 2012-2013 For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/723966
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DatasetSediment oxygen demand and ammonium, nitrate plus nitrate, and phosphate flux data from Little Lagoon, Alabama(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-03-15) Mortazavi, Behzad ; Burnett, William C.Sediment oxygen demand and ammonium, nitrate plus nitrate, and phosphate flux data from Little Lagoon, Alabama from 2010-2013 For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/723984
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DatasetPhysical environmental data from Little Lagoon, Alabama collected from 2012-2013.(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-03-14) Mortazavi, Behzad ; Burnett, William C.Physical environmental data from Little Lagoon, Alabama collected from 2012-2013. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/723993
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PreprintIsotopic, geophysical and biogeochemical investigation of submarine groundwater discharge : IAEA-UNESCO intercomparison exercise at Mauritius Island( 2011-09) Povinec, Pavel P. ; Burnett, William C. ; Beck, A. ; Bokuniewicz, Henry J. ; Charette, Matthew A. ; Gonneea, Meagan E. ; Groening, M. ; Ishitobi, T. ; Kontar, E. ; Kwong, L. Liong Wee ; Marie, D. E. P. ; Moore, Willard S. ; Oberdorfer, J. A. ; Peterson, R. ; Ramessur, R. ; Rapaglia, J. ; Stieglitz, T. ; Top, ZaferSubmarine groundwater discharge (SGD) into a shallow lagoon on the west coast of Mauritius Island (Flic-en-Flac) was investigated using radioactive (3H, 222Rn, 223Ra, 224Ra, 226Ra, 228Ra) and stable (2H, 18O) isotopes and nutrients. SGD intercomparison exercises were carried out to validate the various approaches used to measure SGD including radium and radon measurements, seepage-rate measurements using manual and automated meters, sediment bulk conductivity and salinity surveys. SGD measurements using benthic chambers placed on the floor of the Flic-en-Flac Lagoon showed discharge rates up to 500 cm/day. Large variability in SGD was observed over distances of a few meters, which were attributed to different geomorphological features. Deployments of automated seepage meters captured the spatial and temporal variability of SGD with a mean seepage rate of 10 cm/day. The stable isotopic composition of submarine waters was characterized by significant variability and heavy isotope enrichment and was used to predict the contribution of fresh terrestrially derived groundwater to SGD (range from a few % to almost 100 %). The integrated SGD flux, estimated from seepage meters placed parallel to the shoreline, was 35 m3/m day, which was in a reasonable agreement with results obtained from hydrologic water balance calculation (26 m3/m day). SGD calculated from the radon inventory method using in situ radon measurements were between 5 and 56 m3/m per day. Low concentrations of radium isotopes observed in the lagoon water reflected the low abundance of U and Th in the basalt that makes up the island. High SGD rates contribute to high nutrients loading to the lagoon, potentially leading to eutrophication. Each of the applied methods yielded unique information about the character and magnitude of SGD. The results of the intercomparison studies have resulted a better understanding of groundwater-seawater interactions in coastal regions. Such information is an important pre-requisite for the protection management of coastal freshwater resources.
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PreprintEvaluation of the flushing rates of Apalachicola Bay, Florida via natural geochemical tracers( 2007-07-10) Dulaiova, Henrieta ; Burnett, William C.We used naturally occurring radium isotopes as tracers of water exchange in Apalachicola Bay, a shallow coastal-plain estuary in northwestern Florida. The bay receives fresh water and radium from the Apalachicola River, and mixes with Gulf of Mexico waters through four inlets. We deployed moored buoys with attached Mn-fibers at several stations throughout the estuary during two summer and two winter periods. After deployment for at least one tidal cycle we measured the ratio of the two short-lived radium isotopes 223Ra (half-life = 11 d) and 224Ra (3.6 d) to estimate “radium ages” of the water in the bay. During our four seasonal deployments the river discharge ranged from 338 to 1016 m3 s- 1. According to our calculations the water turnover time in the bay during these samplings ranged from 6 to 12 days. Age contours in the bay showed that winds and tides as well as river discharge influence the water movement and the residence time of freshwater in the bay. We also calculated the mean age of river water in the bay which was between 5 to 9 days during the studied periods. We suggest that this approach can be used to quantify transport processes of dissolved substances in the bay. For example, soluble nutrient or pollutant transport rates from a point source could be examined. We conclude that the radium age technique is well suited for flushing rate calculations in river dominated shallow estuaries.
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PreprintAssessment of groundwater discharges into West Neck Bay, New York, via natural tracers( 2006-05-21) Dulaiova, Henrieta ; Burnett, William C. ; Chanton, Jeffrey P. ; Moore, Willard S. ; Bokuniewicz, Henry J. ; Charette, Matthew A. ; Sholkovitz, Edward R.A field experiment to compare methods of assessing submarine groundwater discharge (SGD) was held on Shelter Island, NY, in May 2002. We evaluated the use of radon, radium isotopes, and methane to assess SGD rates and dynamics from a glacial aquifer in the coastal zone. Fluxes of radon across the sediment-water interface were calculated from changes in measured surface water inventories following evaluation and correction for tidal effects, atmospheric evasion, and mixing with offshore waters. These fluxes were then converted to SGD rates using the measured radon concentration in the groundwater. We used the short-lived radium isotopes to calculate a horizontal mixing coefficient to assess radon loss by mixing between nearshore and offshore waters. We also made an independent calculation of SGD using the Ra-derived mixing coefficient and the long-lived 226Ra concentration gradient in the bay. Seepage rates were calculated to range between 0 and 34 cm.day-1 using the radon measurements and 15 cm.day-1 as indicated by the radium isotopes. The radiotracer results were consistent and comparable to SGD rates measured directly with vented benthic chambers (seepage meters) deployed during this experiment. These meters indicated rates between 2 and 200 cm.day-1 depending on their location. Both the calculated radon fluxes and rates measured directly by the automated seepage meters revealed a clear reproducible pattern of higher fluxes during low tides. Considering that the two techniques are completely independent, the agreement in the SGD dynamics is significant. Methane concentration in groundwater was very low (~30 nM) and not suitable as SGD tracer at this study site.
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ArticleCarbon accumulation, flux, and fate in Stordalen Mire, a permafrost peatland in transition(American Geophysical Union, 2022-01-03) Holmes Huettel, M. Elizabeth ; Crill, Patrick M. ; Burnett, William C. ; McCalley, Carmody K. ; Wilson, Rachel M. ; Frolking, Stephen ; Chang, Kuang-Yu ; Riley, William J. ; Varner, Ruth K. ; Hodgkins, Suzanne B. ; McNichol, Ann P. ; Saleska, Scott R. ; Rich, Virginia I. ; Chanton, Jeffrey P.Stordalen Mire is a peatland in the discontinuous permafrost zone in arctic Sweden that exhibits a habitat gradient from permafrost palsa, to Sphagnum bog underlain by permafrost, to Eriophorum-dominated fully thawed fen. We used three independent approaches to evaluate the annual, multi-decadal, and millennial apparent carbon accumulation rates (aCAR) across this gradient: seven years of direct semi-continuous measurement of CO2 and CH4 exchange, and 21 core profiles for 210Pb and 14C peat dating. Year-round chamber measurements indicated net carbon balance of −13 ± 8, −49 ± 15, and −91 ± 43 g C m−2 y−1 for the years 2012–2018 in palsa, bog, and fen, respectively. Methane emission offset 2%, 7%, and 17% of the CO2 uptake rate across this gradient. Recent aCAR indicates higher C accumulation rates in surface peats in the palsa and bog compared to current CO2 fluxes, but these assessments are more similar in the fen. aCAR increased from low millennial-scale levels (17–29 g C m−2 y−1) to moderate aCAR of the past century (72–81 g C m−2 y−1) to higher recent aCAR of 90–147 g C m−2 y−1. Recent permafrost collapse, greater inundation and vegetation response has made the landscape a stronger CO2 sink, but this CO2 sink is increasingly offset by rising CH4 emissions, dominated by modern carbon as determined by 14C. The higher CH4 emissions result in higher net CO2-equivalent emissions, indicating that radiative forcing of this mire and similar permafrost ecosystems will exert a warming influence on future climate.
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ArticleA new perspective for assessing water transport and associated retention effects in a large reservoir(John Wiley & Sons, 2018-09-23) Xu, Bochao ; Yang, Disong ; Yao, Peng ; Burnett, William C. ; Ran, Xiangbin ; Charette, Matthew A. ; Huang, Xinying ; Liu, Sumei ; Yu, ZhigangRadioactive tracer techniques may be useful for assessing water transport and the overall effects of concurrent biogeochemical processes in river‐reservoir systems. In this study, we show that radium isotopes can assess the hydrodynamics and sediment/nutrient retention in the Xiaolangdi Reservoir, the largest impoundment along the Yellow River, China. Activity ratios of 224Ra/226Ra and 223Ra/226Ra were used for water mass age calculations in the riverine, transition, and lentic reaches of the reservoir. Water ages were combined with the length scale of three river‐reservoir zones to determine water transport rates of 3.6 ± 1.2, 1.3 ± 0.3, and 0.16 ± 0.14 km/day, respectively. Radium ages were also used to quantify the net retention of sediment and nutrients in different parts of the river‐reservoir system. Suspended sediment was removed at a rate of 1.4 ± 0.6 g/m3/day, mainly in the riverine zone. Nutrient dynamics were more complicated, with addition or removal at different rates within the three zones.
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ArticleA benthic monitor for coastal water dissolved oxygen variation: Mn/Ca ratios in tests of an epifaunal foraminifer(American Geophysical Union, 2021-12-17) Guo, Xiaoyi ; Wei, Qinsheng ; Xu, Bochao ; Burnett, William C. ; Bernhard, Joan M. ; Nan, Haiming ; Lian, Ergang ; Yang, Shouye ; Yu, ZhigangAn appropriate proxy could help to better understand dissolved oxygen variations in the past, helping to predict potential outcomes of future environmental changes. In the Changjiang Estuary (China), the foraminifer Cribrononion subincertum (C. subincertum) shows a distinct population maximum in the topmost sediment, an indication of an epifaunal species. Therefore, the geochemical composition of C. subincertum tests could record changes in the region’s bottom water chemistry. Our results showed that Mn/Ca ratios in tests of living (Rose-Bengal stained) C. subincertum analyzed by LA-ICP-MS were responsive to variations of bottom water dissolved oxygen concentrations, with average foraminiferal Mn/Ca ratios three times higher during low-oxygen period than in winter. In the uppermost centimeters of sediment, wider ranges of foraminiferal Mn/Ca occurred in summer compared to winter ranges. Our results imply that this epifaunal benthic foraminiferal species could serve as a useful benthic monitor with the Mn/Ca ratios representing a reliable proxy of hypoxia in the past.
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DatasetHS- and NH4+ porewater data from Little Lagoon, Alabama collected from 2012-2013.(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-03-15) Mortazavi, Behzad ; Burnett, William C.HS- and NH4+ porewater data from Little Lagoon, Alabama collected from 2012-2013. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/723975
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DatasetPotential denitrification and N2 fixation from slurry assays from Little Lagoon, Alabama collected from 2012-2013(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-03-15) Mortazavi, Behzad ; Burnett, William C.Potential denitrification and N2 fixation from slurry assays from Little Lagoon, Alabama collected from 2012-2013 For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/723957
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Dataset15NO3 data, acetylene reduction assays, and NH4+ diffusion average summaries from samples collected in Little Lagoon, Alabama from 2012 to 2013.(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-03-15) Mortazavi, Behzad ; Burnett, William C.15NO3 data, acetylene reduction assays, and NH4+ diffusion average summaries from samples collected in Little Lagoon, Alabama from 2012 to 2013. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/723935
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PreprintIsotope tracing of submarine groundwater discharge offshore Ubatuba, Brazil : results of the IAEA–UNESCO SGD project( 2008-06-12) Povinec, Pavel P. ; Bokuniewicz, Henry J. ; Burnett, William C. ; Cable, J. ; Charette, Matthew A. ; Comanducci, J.-F. ; Konta, E. A. ; Moore, Willard S. ; Oberdorfer, J. A. ; de Oliveira, J. ; Peterson, R. ; Stieglitz, T. ; Taniguchi, M.Results of groundwater and seawater analyses for radioactive (3H, 222Rn, 223Ra, 224Ra, 226Ra, 228Ra) and stable (2H, 18O) isotopes are presented together with in situ spatial mapping and time-series 222Rn measurements in seawater, direct seepage measurements using manual and automated seepage meters, pore water investigations using different tracers and piezometric techniques, and geoelectric surveys probing the coast. This study represents first time that such a new complex arsenal of radioactive and non-radioactive tracer techniques and geophysical methods have been used for simultaneous submarine groundwater discharge (SGD) investigations. Large fluctuations of SGD fluxes were observed at sites situated only a few meters apart (from 0 cm d-1 to 360 cm d-1; the unit represents cm3/cm2/day), as well as during a few hours (from 0 cm d-1 to 110 cm d-1), strongly depending on the tidal fluctuations. The average SGD flux estimated from continuous 222Rn measurements is 17±10 cm d-1. Integrated coastal SGD flux estimated for the Ubatuba coast using radium isotopes is about 7x103 m3 d-1 per km of the coast. The isotopic composition (δ2H and δ18O) of submarine waters was characterised by significant variability and heavy isotope enrichment, indicating that the contribution of groundwater in submarine waters varied from a small percentage to 20%. However, this contribution with increasing offshore distance became negligible. Automated seepage meters and time-series measurements of 222Rn activity concentration showed a negative correlation between the SGD rates and tidal stage. This is likely caused by sea level changes as tidal effects induce variations of hydraulic gradients. The geoelectric probing and piezometric measurements contributed to better understanding of the spatial distribution of different water masses present along the coast. The radium isotope data showed scattered distributions with offshore distance, which imply that seawater in a complex coast with many small bays and islands was influenced by local currents and groundwater/seawater mixing. This has also been confirmed by a relatively short residence time of 1-2 weeks for water within 25 km offshore, as obtained by short-lived radium isotopes. The irregular distribution of SGD seen at Ubatuba is a characteristic of fractured rock aquifers, fed by coastal groundwater and recirculated seawater with small admixtures of groundwater, which is of potential environmental concern and has implications on the management of freshwater resources in the region.