Using radium and radon to evaluate ground water discharge and benthic exchange in upper Newport Bay, California
University of Southern California, 2007 - Science - 256 pages
Water column and sediment samples collected from Newport Bay, CA, were analyzed for radium and radon during February, April, August, and October, 2004 to quantify ground water discharge and benthic exchange. In-situ fluxes measured with chambers were enhanced from diffusive fluxes by factors of 1.5, 2.3, and 4.5 for Ra-224, Ra-223, and Rn-222, respectively, showing that isotopic flux enhancements correlate with increasing scale length as a result of irrigation. Budgets constructed for each isotope established an upper limit for ground water discharge of 0.09 +/- 0.14 m3/s in April and 0.12 +/- 0.17 m3/s in August, less than 4% of fresh water input. Tidal pumping supplied fluxes of Ra-223 and Ra-224 ∼2.5 times that of diffusion and irrigation. Transport models were constructed to evaluate mixing and potentially localized inputs. The predicted diffusivity was 85-145 m 2/s, indicating that mixing may be driven by two-layer flow, rather than diffusive exchange of eddies.
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12 Distance 2-layer 20 25 Salinity 25 Salinity psu advection Appendix average bathymetry Benthic flux River calculated CM CM coastal coefficient concentration Cosmochimica Acta diffusive fluxes Distance from Ocean distribution dpm/l ebb tide eddy diffusion End-members enhanced estimated estuary fiber Figure 3-2 Continued flow Benthic flux flux River input fresh water input gas exchange geometry ground water discharge ground water flow ground water input Groundwater flow Benthic H H H Hammond input Net Ocean intertidal isotopes isotopic budgets Lower Channel Lower Harbor MHHW mixing MLLW Ocean Exchange Decay Ocean km Orange County pore water activity radioisotopes radium radon Rn-222 budgets San Diego Creek San Joaquin Hills Santa Ana River Saturday Sunday Monday scale length sediment subtidal channel tidal prism tidal pumping transect transport model two-layer upper bay Upper Channel Upper Newport Bay velocity water column water flow rates