Delta salinity

Water quality issues for the lower Sacramento and San Joaquin rivers and for the Delta include salinity, dissolved organic carbon (DOC), suspended sediment. 

Fig. 4 Maximum salinity intrusions into the Delta at five year time intervals from 1945 to 1990 are shown. Drought conditions and rising sea level from climate change are predicted to increase salinity intrusions eastward into the Delta in the future...

Figure 8.1 The duration of NREM sleep and delta activity during NREM sleep following saline (open circles) or 0.5mg/kg MK-801 (filled circles), administered 6h after the start of the dark period. MK-801 initially produced a period of wakefulness approximately 3 h long. In the subsequent light period, NREM sleep duration (A), total integrated amplitude (TIA, a period amplitude measure similar to power) of NREM sleep delta (B), and NREM sleep delta integrated amplitude per minute (IA/min) (C) were all significantly increased above control levels.

At the Ebro delta, P. pectinatus is mainly found in the least brackish areas, while Ruppia cirrhosa inhabits transitional zones between freshwater and seawater. Mixed stands of Zostera noltii, R. cirrhosa, and the floating macroalga Chaetomorpha linum develop in saline areas [37]. 

Delta irrigation channels (Faria, personal communication) indicate a saline water intrusion in the irrigation channels of the Delta. This saline intrusion may cause a dilution of mercury pollution originated at the chlor-alkali plant, hence resulting in lower average THg concentrations in Delta specimens. 

However, salinity values are easily obtained with a salinometer (which measures electrical conductivity and is appropriately calibrated with standard solutions and adjusted to account for T effects). The salinity of seawater increases if the loss of H2O (evaporation, formation of ice) exceeds the atmospheric input (rain plus rivers), and diminishes near deltas and lagoons. Salinity and temperature concur antithetically to define the density of seawater. The surface temperature of the sea reflects primarily the latitude and season of sampling. The vertical thermal profile defines three zones surface (10-100 m), where T is practically constant thermoclinal (100-1000 m), where T diminishes regularly with depth and abyssal... 

In summary, these studies point toward important roles for organic matter and salinity in determining sulfur behavior, but are not focused on intermediate sediments and, with a few exceptions (3), are not petrographic in nature. A reconnaissance investigation was undertaken to ascertain possible influences on sulfur incorporation in Mississippi Delta Plain sediments and to determine forms of sulfur in these sediments. 

River water runoff is responsible for many hydrological features of river mouths and their parts - deltas, semi-enclosed coastal water bodies and open nearshore zone. Water runoff influences water levels in deltas, delta inundation, water salinity at the mouths, etc. Water runoff depresses action of the storm surges on the deltas. River sediments load determines channel processes, sedimentation in a delta and nearshore, delta formation processes, the rate of delta progradation into the sea. 

The mixing zone of river fresh water with salinity less than 0.5%o and sea brackish water with salinity up to 18%> occupies a bend up to 20-30 km in width during high-flow period and western winds and of 3-5 km during the low-flow period and eastern winds [7,30]. The Danube water spreads mainly on the surface with layer from 1-3 to 5 m [9]. The Danube River water runoff and its distribution between delta branches play a very important role not only in hydrological and hydrochemical regime of the delta and mouth nearshore zone but also in formation of ecological conditions in the northwestern part of the Black Sea as a whole [7,9,30]. 

In a classic paper, Pillsbury (1981) described how recycling of salts via irrigation and agricultural return flow controls the salinity of downstream rivers in arid zones. Once the natural salt balance is disturbed and salts begin to accumulate, either in the unsaturated zone or in drainage waters, the salinity increases. The salinity of the Colorado River is derived from a century of activity that includes upstream diversion of freshwater, massive irrigation, evapotranspiration and salt accumulation in the soil, and return of saline drainage back to the river (Pillsbury, 1981). Similarly, the rise of the salinity in the Nile Delta has been attributed to a disturbance of the natural salts balance after the construction of Assuan dam and the reduction of the natural outflow of salts from the Nile River to... 

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