Lithogenic and cosmogenic tracers in catchment hydrology

Groundwater and surface water flow to the Merced River, Yosemite Valley, California: 36Cl and Cl− evidence

“…Previous 36 Cl/Cl results suggest that some groundwater within Yosemite National Park originated in metamorphic rock that was intruded by the granitics, with the implication that it is connate [ Nimz , ]. Although small volumes of connate waters may exist in the Sierra Nevada, virtually all surface water observed today originated as precipitation [ Nimz et al ., ; Hudson et al ., ].…”

Seasonal evolution of water contributions to discharge from a Greenland outlet glacier: insight from a new isotope-mixing model

“…Be activities likely reflects atmospheric inventory depletion and wet deposition-related dilution effects of precipitation-event frequency and duration (Nimz, 1998 Be signal, and most likely represented a switch in end-member contribution from snowmelt to ice melt. The May value, however, was consistent with a hydrological connection between surface melt and subsurface discharge at this point in the season.…”

Hydrologic and Geochemical Controls on the Transport of Radionuclides in Natural Undisturbed Arid Environments as Determined by Accelerator Mass Spectrometry Measurements

“…Bomb-pulse values measured in these studies were 8.3 x 10 -11 (dilute groundwater) and about 8.5 x 10 -11 (marine sediment). The groundwater sample contains chlorine with a bomb-pulse , which is a factor of 4 lower than the maximum ratio reported for very dilute groundwater at Yosemite, California (Nimz, 1998). If the iodine bomb-pulse value were to scale accordingly, the maximum precipitation 129 I/I bomb-pulse ratio in the western United States could be expected to be at least 3 x 10 -10 , or about 3 orders of magnitude higher than background.…”

“…Changes in pre-1950's 36 Cl/Cl ratios observed in deep soil profiles below the bomb-pulse peak may be an indication of paleoclimate conditions (Phillips, 1994). The 36 Cl/Cl ratio (non-bomb-pulse) for chlorine deposited at any given time is the result of mixing of cosmogenic 36 Cl produced in the atmosphere with stable chlorine from ambient sources, most prominently the oceans (Nimz, 1998). Changes in atmospheric circulation and thus of the mixing of cosmogenic 36 Cl with marine chloride may produce a "secular variation" in 36 Cl/Cl ratios at depth.…”