Turnover times, water

The turnover time of carbon in biota in the ocean surface water is 3 x 10 /(4 + 36) x lO yr 1 month. The turnover time with respect to settling of detritus to deeper layers is considerably longer 9 months. Faster removal processes in this case must determine the turnover time respiration and decomposition. 

Consider the water balance of a lake with a constant source flux Q. The outlet is the "threshold" type where the sink is proportional to the mass of water above a threshold value Mi S = k(M — Ml). Calculate the turnover time of water at steady state and the response time relative to changes in Q. 

Fig. 6-3 Global water balance. Storages in km fluxes in km /yr. Turnover times calculated as storage divided by total annual inflow. (Data from Shiklomanov and Sokolov, 1983.)...

The enormous volume of the oceans results in an average turnover time of more than 2600 years, compared to less than 10 days for atmospheric water. Although the reservoir is much smaller than the oceans, the cryosphere has the longest turnover time due to the small input flux. Average turnover times for all seven reservoirs, calculated from the data in Fig. 6-3, are shown in Table 6-3. 

Many hydrologic reservoirs can be further subdivided into smaller reservoirs, each with a characteristic turnover time. For example, water resides in the Pacific Ocean longer than in the Atlantic, and the oceans surface waters cycle much more quickly than the deep ocean. Similarly, groundwater near the surface is much more active than deep reservoirs, which may cycle over thousands or millions of years, and water frozen in the soil as permafrost. Typical range in turnover times for hydrospheric reservoirs on a hillslope scale (10-10 m) are shown in Table 6-4 (estimates from Falkenmark and Chapman, 1989). Depths are estimated as typical volume averaged over the watershed area. 

The turnover time of water vapor in the atmosphere obviously is a function of latitude and altitude. In the equatorial regions, its turnover time in the atmosphere is a few days, while water in the stratosphere has a turnover time of one year or more. Table 7-1 Qunge, 1963) provides an estimate of the average residence time for water vapor for various latitude ranges in the troposphere. Given this simple picture of vertical structure, motion, transport, and diffusion, we can proceed to examine the behavior of... 

Turnover times of 137Cs and HTO in the troposphere and removal rates of natural aerosol particles and water vapour. Journal of Geophysical Research, 78, 7076-86. 

Many factors control whether a given water body will become acidified as a result of a given deposition regime. In addition to the deposition rate and the lake residence or turnover time, these include the ratio of water surface area to watershed area, the composition of the lake bottom, the residence time of incident precipitation en route through the watershed, and the buffering capacity of the watershed. The presence of organic material can also be important. 

Table 3.1 Average turnover times of water in different reservoirs on Earth.

Zafiriou et al. (1992) reported trace amounts of N02 (0.4—1 nM) in the tail of the PNM layer in the NW Atlantic Ocean to a depth of at least 1000 m. The N02 inventory in this region was roughly equivalent to that in the PNM feature itself This mid-water N02 pool was dynamic with an estimated turnover time of a few days. At Station ALOHA, Dore and Karl (1996h) likewise detected an... 

Table 1 Turnover times for naphthalene, phenan-threne, and benzo(a)pyrene in water and sediment.

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