TY - JOUR
T1 - The use of 3H and tritiogenic 3He to determine CFC degradation and vertical mixing rates in Framvaren Fjord, Norway
AU - Shapiro, Stephanie D.
AU - Schlosser, Peter
AU - Smethie, William M.
AU - Stute, Martin
N1 - Funding Information:
The authors gratefully acknowledge Dr. Jens M. Skei of the Norwegian Institute for Water Research, Oslo, Norway, Dr. Brent A. McKee of the Louisiana Universities Marine Center, Cocodrie, Louisiana, and Dr. James F. Todd of the National Oceanic and Atmospheric Administration Office of Global Pro- grams, Silver Spring, MD for organizing the sampling expedition, as well as Dr. Kelly K. Falkner of Oregon State University, Corvallis, OR, and Dr. Jens M. Skei for assistancew ith sampling. The assistance of Eugene Gorman of the Lamont-Doherty Earth Observatory,P alisades, NY, who provided guidance in analyzing the CFC samples, and of Dr. Allen M. Shapiro of the U.S. Geological Survey, Reston, VA, who provided the 1D diffusion models is also gratefully acknowledged. The W.M. Keck Foundation and the National Science Foundation provided the funds for the Noble Gas Facility. Funding for S.D.S. was provided by the Columbia University Strategic Research Initiative. L-DE0 contribution No. 5658.
PY - 1997/12
Y1 - 1997/12
N2 - Concentrations of CFC-11 and CFC-12, as well as tritium and helium isotopes were measured in the super-anoxic, sub-surface waters of Framvaren Fjord in Norway to assess the stability of CFCs in reducing environments. This fjord provides an ideal environment to study the degradation of CFCs because of its relatively simple dynamics and the narrow zone in which chemical reactions and biological activity, relevant to CFC degradation, occur in the water column. CFCs and tritium enter the fjord at the surface and are transported into the deep water primarily by turbulent vertical mixing. The turbulent vertical mixing rate was determined by fitting a 1D model to the vertical distributions of [3H] and [3H] + [3He(trit)], and found to be 0.006-0.008 cm2 s-1. Using these values, the degradation rates for CFC-11 and CFC-12 were obtained by comparing model simulations incorporating first-order degradation rates to the observed CFC profiles. CFC-11 is degraded at a rate of 6-9 yr-1 below 19 m depth where oxygen concentrations are zero. CFC-12 is found to have a maximum degradation rate of 0.01 to 0.03 yr-1.
AB - Concentrations of CFC-11 and CFC-12, as well as tritium and helium isotopes were measured in the super-anoxic, sub-surface waters of Framvaren Fjord in Norway to assess the stability of CFCs in reducing environments. This fjord provides an ideal environment to study the degradation of CFCs because of its relatively simple dynamics and the narrow zone in which chemical reactions and biological activity, relevant to CFC degradation, occur in the water column. CFCs and tritium enter the fjord at the surface and are transported into the deep water primarily by turbulent vertical mixing. The turbulent vertical mixing rate was determined by fitting a 1D model to the vertical distributions of [3H] and [3H] + [3He(trit)], and found to be 0.006-0.008 cm2 s-1. Using these values, the degradation rates for CFC-11 and CFC-12 were obtained by comparing model simulations incorporating first-order degradation rates to the observed CFC profiles. CFC-11 is degraded at a rate of 6-9 yr-1 below 19 m depth where oxygen concentrations are zero. CFC-12 is found to have a maximum degradation rate of 0.01 to 0.03 yr-1.
UR - http://www.scopus.com/inward/record.url?scp=0031450995&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0031450995&partnerID=8YFLogxK
U2 - 10.1016/S0304-4203(97)00007-8
DO - 10.1016/S0304-4203(97)00007-8
M3 - Article
AN - SCOPUS:0031450995
SN - 0304-4203
VL - 59
SP - 141
EP - 157
JO - Marine Chemistry
JF - Marine Chemistry
IS - 1-2
ER -