Parameterizing air-water gas exchange in the shallow, microtidal New River estuary

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution-NonCommercial‐NoDerivs License. The definitive version was published in Van Dam, B. R., Edson, J. B., & Tobias, C. Parameterizing air-water gas exchange in the shallow, microtidal New River estuary. Journal of Geophysical Research-Biogeosciences, 124(7), (2019): 2351-2363, doi: 10.1029/2018JG004908.Estuarine CO2 emissions are important components of regional and global carbon budgets, but assessments of this flux are plagued by uncertainties associated with gas transfer velocity (k) parameterization. We combined direct eddy covariance measurements of CO2 flux with waterside pCO2 determinations to generate more reliable k parameterizations for use in small estuaries. When all data were aggregated, k was described well by a linear relationship with wind speed (U10), in a manner consistent with prior open ocean and estuarine k parameterizations. However, k was significantly greater at night and under low wind speed, and nighttime k was best predicted by a parabolic, rather than linear, relationship with U10. We explored the effect of waterside thermal convection but found only a weak correlation between convective scale and k. Hence, while convective forcing may be important at times, it appears that factors besides waterside thermal convection were likely responsible for the bulk of the observed nighttime enhancement in k. Regardless of source, we show that these day‐night differences in k should be accounted for when CO2 emissions are assessed over short time scales or when pCO2 is constant and U10 varies. On the other hand, when temporal variability in pCO2 is large, it exerts greater control over CO2 fluxes than does k parameterization. In these cases, the use of a single k value or a simple linear relationship with U10 is often sufficient. This study provides important guidance for k parameterization in shallow or microtidal estuaries, especially when diel processes are considered.We thank SERDP and DCERP for funding and support. Dennis Arbige assisted with EC tower construction, and Susan Cohen provided invaluable logistical support. I also thank Marc Alperin (UNC Chapel Hill) for his thoughtful guidance and encouragement with this project. All data sets for this manuscript are available at FigShare (https://doi.org/10.6084/m9.figshare.7276877.v1). Additional funding for this project was provided by DAAD (57429828) from funds of the German Federal Ministry of Education and Research (BMBF)

Comparison of floating chamber and eddy covariance measurements of lake greenhouse gas fluxes

Fluxes of carbon dioxide (CO2) and methane (CH4) from lakes may have a large impact on the magnitude of the terrestrial carbon sink. Traditionally lake fluxes have been measured using the floating chamber (FC) technique; however, several recent studies use the eddy covariance (EC) method. We present simultaneous flux measurements using both methods at lake Tamnaren in Sweden during field campaigns in 2011 and 2012. Only very few similar studies exist. For CO2 flux, the two methods agree relatively well during some periods, but deviate substantially at other times. The large discrepancies might be caused by heterogeneity of partial pressure of CO2 (pCO(2w)) in the EC flux footprint. The methods agree better for CH4 fluxes. It is, however, clear that short-term discontinuous FC measurements are likely to miss important high flux events.Funding Agencies|Swedish research council FORMAS; VR</p

Concentração e fluxo de CO2 sobre o reservatório hidrelétrico de Balbina (AM)

The reservoir Balbina (59º 28’ 50w, 1º 53’ 25” S), located near the city of Manaus, Amazonas, in Central Amazônia, Brazil, is the second largest hydroelectric reservoir in an area located in the Amazon Basin. In this reservoir, CO2 measurements were performed at high frequency (10 Hz), CO2 flux with gas analyzer infrared (IRGA) coupled to a floating chamber and meteorological variables with a buoy instrumented to 2 m from the lake surface. The average CO2 concentration was 392 and 426 ppm for the day and night, respectively, and the daily average emission rate was 40.427±24.040 μmol-1.m-2.d-1. The accumulation of CO2 in the lake overnight, beyond respiration, shows to be affected by low wind speeds, waterside convection, physical processes involving high concentrations of CO2 for the surface and the presence of land breeze. The fluxes show no statistically significant difference with the meteorological variables and were considerably lower than a previous study for the same lake. However, the values are in agreement with other studies in Amazonian tropical lakes and other reservoirs. © 2017, ABES - Associacao Brasileira de Engenharia Sanitaria e Ambiental. All rights reserved

European nutrition and health report 2009

The aim of the European Nutrition and Health Report (ENHR) 2009 is to provide acomprehensive view of the nutrition and health status in the European Union (EU). It isnot intended to generate new data, but rather to collect available and authorised data,published or unpublished, on the nutrition and health situation in the countries of the E