TY - JOUR
T1 - Widespread elevated atmospheric SF6 mixing ratios in the Northeastern United States
T2 - Implications for groundwater dating
AU - Santella, Nicholas
AU - Ho, David T.
AU - Schlosser, Peter
AU - Stute, Martin
N1 - Funding Information:
We thank J. Simpson, for discussions and advice, A. Caniano, J. Dacey, M. Garrison, J. Gribbon, M. Hendricks, J. Housell, C. Kosar, R. Kruzansky, X. Liu, B. Ma, K. Mull, A. Santella, and D. Santella for assistance in the field, J. Dacey for providing laboratory space at WHOI, and the many employees of federal, state and local parks departments who facilitated the field work. Remote atmosphere SF 6 data was obtained from Geoff Dutton of NOAA/CMDL . Funding was provided by NSF/DOE through the Environmental Molecular Science Institute. Additional funding was provided by the USEPA – NIEHS/Superfund Basic Research Program through Grant P42ES10349.
PY - 2008/1/30
Y1 - 2008/1/30
N2 - SF6 is a promising transient tracer for groundwater dating, but elevated levels of atmospheric SF6 may limit application of this dating method in urban areas. To determine the magnitude of this limitation within the United States (US), this study derives average atmospheric SF6 mixing ratios from soil air measurements from five major urban areas. All surveyed sites showed SF6 elevated above Northern Hemisphere clean air levels. In many cases, SF6 mixing ratios were highest within large cities, but significantly elevated levels persisted hundreds of kilometers beyond the urban centers. Estimated SF6 emissions from New York city were anomalously large, resulting in average levels over 200% above remote atmosphere values. Emissions from other urban areas included in this study appear to be typical for large cities in the US and maximum observed elevations of SF6, in these areas, were in the range of 50-100%. These findings imply that caution is needed in choosing an atmospheric input function when using SF6 as a transient tracer within or near urbanized regions. Within the Northeast US, the assumption of remote atmospheric SF6 may lead to significant errors in estimation of groundwater ages, especially in the case of an expected future flattening of the atmospheric mixing ratio curve.
AB - SF6 is a promising transient tracer for groundwater dating, but elevated levels of atmospheric SF6 may limit application of this dating method in urban areas. To determine the magnitude of this limitation within the United States (US), this study derives average atmospheric SF6 mixing ratios from soil air measurements from five major urban areas. All surveyed sites showed SF6 elevated above Northern Hemisphere clean air levels. In many cases, SF6 mixing ratios were highest within large cities, but significantly elevated levels persisted hundreds of kilometers beyond the urban centers. Estimated SF6 emissions from New York city were anomalously large, resulting in average levels over 200% above remote atmosphere values. Emissions from other urban areas included in this study appear to be typical for large cities in the US and maximum observed elevations of SF6, in these areas, were in the range of 50-100%. These findings imply that caution is needed in choosing an atmospheric input function when using SF6 as a transient tracer within or near urbanized regions. Within the Northeast US, the assumption of remote atmospheric SF6 may lead to significant errors in estimation of groundwater ages, especially in the case of an expected future flattening of the atmospheric mixing ratio curve.
KW - Groundwater age
KW - Northeastern USA
KW - SF
KW - Unsaturated zone
KW - Urban groundwater
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U2 - 10.1016/j.jhydrol.2007.10.031
DO - 10.1016/j.jhydrol.2007.10.031
M3 - Article
AN - SCOPUS:37549029830
SN - 0022-1694
VL - 349
SP - 139
EP - 146
JO - Journal of Hydrology
JF - Journal of Hydrology
IS - 1-2
ER -